JPWO2019035224A1 - Free-cutting copper alloy and method for producing free-cutting copper alloy - Google Patents

Abstract

This free-cutting copper alloy has Cu: 76.0-78.7%, Si: 3.1-3.6%, Sn: 0.40-0.85%, P: 0.05-0.14 %, Pb: 0.005% or more and less than 0.020%, the balance is made of Zn and inevitable impurities, the composition satisfies the following relationship, 75.0 ≦ f1 = Cu + 0.8 × Si−7.5 × Sn + P + 0.5 × Pb ≦ 78.260.0 ≦ f2 = Cu−4.8 × Si−0.8 × Sn−P + 0.5 × Pb ≦ 61.50.09 ≦ f3 = P / Sn ≦ 0.30 The area ratio (%) of the phase satisfies the following relationship: 30 ≦ κ ≦ 65, 0 ≦ γ ≦ 2.0, 0 ≦ β ≦ 0.3, 0 ≦ μ ≦ 2.0, 96.5 ≦ f4 = α + κ, 99.4 ≦ f5 = α + κ + γ + μ, 0 ≦ f6 = γ + μ ≦ 3.0, 35 ≦ f7 = 1.05 × κ + 6 × γ1 / 2 + 0.5 × μ ≦ 70 α phase exists in α phase The long side of the γ phase is 50 μm or less, and the long side of the μ phase is 25 μm or less.

Description

The present invention provides a free-cutting copper alloy having excellent corrosion resistance, high strength, high-temperature strength, good ductility and impact properties, and having a significantly reduced lead content, and a method for producing a free-cutting copper alloy About. In particular, appliances used for drinking water that people and animals ingest daily, such as water taps, valves, fittings, etc., as well as valves, fittings, etc. used in harsh environments where high-speed fluid flows. The present invention relates to a free-cutting copper alloy used for industrial piping and a method for producing a free-cutting copper alloy.
This application is based on international applications PCT / JP2017 / 29369, PCT / JP2017 / 29371, PCT / JP2017 / 29373, PCT / JP2017 / 29374, PCT / JP2017 / 29376 filed on August 15, 2017. Insist and use that content here.

Conventionally, as copper alloys used in electrical, automotive, mechanical and industrial piping such as potable water appliances, valves, joints, pressure vessels, etc., 56 to 65 mass% Cu and 1 to 4 mass% Pb Cu-Zn-Pb alloy (so-called free-cutting brass) with the balance being Zn, or 80-88 mass% Cu, 2-8 mass% Sn, 2-8 mass% Pb, A Cu—Sn—Zn—Pb alloy (so-called bronze: gunmetal) in which the balance is Zn is generally used.
However, in recent years, there has been a concern about the influence of Pb on the human body and the environment, and the movement of regulations concerning Pb has been activated in each country. For example, in California, the United States, regulations from January 2010 and in the United States have been effective since January 2014, with the Pb content contained in drinking water devices and the like being 0.25 mass% or less. In addition, it is said that the amount of Pb leached into drinking water will be regulated to about 0.05 mass% in the future in view of the influence on infants and the like. In countries other than the United States, the movement of the regulation is rapid, and the development of a copper alloy material corresponding to the regulation of the Pb content and further reducing the Pb content is required.

  In other industrial fields, such as automobiles, machinery, and electrical / electronic equipment, for example, the European ELV Directive and the RoHS Directive allow exceptionally Pb content of free-cutting copper alloys up to 4 mass%. However, as in the drinking water field, strengthening regulations on Pb content, including the elimination of exceptions, are being actively discussed.

In such a trend of strengthening Pb regulation of free-cutting copper alloys, a β-phase is increased in a copper alloy containing Bi and Se having a machinability function or an alloy of Cu and Zn instead of Pb. A copper alloy containing a high concentration of Zn with improved machinability has been proposed.
For example, in Patent Document 1, it is assumed that corrosion resistance is insufficient only by containing Bi instead of Pb, and in order to reduce the β phase and isolate the β phase, a hot extrusion rod after hot extrusion is used. It has been proposed to gradually cool to 180 ° C. and further to perform heat treatment.
Further, in Patent Document 2, the corrosion resistance is improved by adding 0.7 to 2.5 mass% of Sn to the Cu-Zn-Bi alloy to precipitate the γ phase of the Cu-Zn-Sn alloy. Yes.

However, as shown in Patent Document 1, an alloy containing Bi instead of Pb has a problem in corrosion resistance. And Bi has many problems including the possibility of being harmful to the human body like Pb, the problem of resources because it is a rare metal, and the problem of making the copper alloy material brittle. Yes. Furthermore, as proposed in Patent Documents 1 and 2, even if the β phase is isolated by increasing the corrosion resistance by slow cooling after heat extrusion or heat treatment, the corrosion resistance is improved in severe environments. It is not connected to.
Moreover, as shown in Patent Document 2, even if the γ phase of the Cu—Zn—Sn alloy is precipitated, this γ phase is originally poor in corrosion resistance compared to the α phase, and at last, is corrosion resistance under severe environments. It will not lead to improvement. In the Cu—Zn—Sn alloy, the γ phase containing Sn is inferior in the machinability function as it is necessary to add Bi having machinability function together.

  On the other hand, for copper alloys containing a high concentration of Zn, the β phase is inferior to Pb in machinability, so it cannot be substituted for a free-cutting copper alloy containing Pb. Since it contains a large amount of β phase, the corrosion resistance, particularly the dezincification corrosion resistance and the stress corrosion cracking resistance are extremely bad. In addition, since these copper alloys have low strength at high temperatures (for example, 150 ° C.), they are used, for example, in automobile parts used under high temperatures close to the engine room and piping used under high temperatures and high pressures. Can not respond to the thin and light weight.

  Furthermore, since Bi makes a copper alloy brittle and ductility decreases when a large amount of β phase is contained, a copper alloy containing Bi or a copper alloy containing a large amount of β phase is used as an automobile, machine, or electrical component. It is inappropriate as a drinking water device material including a valve. For brass containing γ phase containing Sn in Cu-Zn alloy, stress corrosion cracking cannot be improved, the strength at room temperature and high temperature is low, and the impact characteristics are poor. It is inappropriate.

On the other hand, as free-cutting copper alloys, Cu—Zn—Si alloys containing Si instead of Pb have been proposed in, for example, Patent Documents 3 to 9.
In Patent Documents 3 and 4, by having an excellent machinability function of γ phase, excellent machinability is realized without containing Pb or with a small amount of Pb. . When Sn is contained in an amount of 0.3 mass% or more, the formation of a γ phase having a machinability function is increased and promoted, and the machinability is improved. In Patent Documents 3 and 4, the corrosion resistance is improved by forming many γ phases.

Further, in Patent Document 5, excellent free machinability is obtained by containing a small amount of Pb of 0.02 mass% or less and simply defining the total content area of the γ phase and the κ phase. Here, Sn acts to form and increase the γ phase and to improve the erosion corrosion resistance.
Further, in Patent Documents 6 and 7, a casting product of Cu—Zn—Si alloy is proposed, and in order to refine the crystal grains of the casting, a very small amount of P and Zr is contained. The ratio of Zr is important.

Patent Document 8 proposes a copper alloy in which Fe is contained in a Cu—Zn—Si alloy.
Further, Patent Document 9 proposes a copper alloy in which Sn, Fe, Co, Ni, and Mn are contained in a Cu—Zn—Si alloy.

  Here, in the above Cu-Zn-Si alloy, as described in Patent Document 10 and Non-Patent Document 1, the Cu concentration is 60 mass% or more, the Zn concentration is 30 mass% or less, and the Si concentration is 10 mass% or less. In addition to the matrix α phase, 10 types of metal phases such as β phase, γ phase, δ phase, ε phase, ζ phase, η phase, κ phase, μ phase, χ phase, and in some cases , Α ′, β ′, and γ ′ are known to contain 13 types of metal phases. Furthermore, as the amount of added elements increases, the metal structure becomes more complex, new phases and intermetallic compounds may appear, and alloys obtained from equilibrium diagrams and actually produced alloys Then, it is well known from experience that a large deviation occurs in the composition of the existing metal phase. Furthermore, it is well known that the composition of these phases varies depending on the concentration of Cu, Zn, Si, etc. of the copper alloy and the processing heat history.

  By the way, the γ phase has excellent machinability, but since the Si concentration is high, it is hard and brittle, if it contains a large amount of γ phase, corrosion resistance, ductility, impact properties, high temperature strength (high temperature creep), etc. in harsh environments Cause problems. For this reason, Cu—Zn—Si alloys containing a large amount of γ phase are also restricted in their use, as are copper alloys containing Bi and copper alloys containing a lot of β phases.

  Note that the Cu—Zn—Si alloys described in Patent Documents 3 to 7 show relatively good results in the dezincification corrosion test based on ISO-6509. However, in the dezincification corrosion test based on ISO-6509, in order to judge the quality of dezincification corrosion resistance in general water quality, a cupric chloride reagent completely different from the actual water quality is used for 24 hours. It is only evaluated in a short time. That is, since the evaluation is performed in a short time using a reagent different from the actual environment, the corrosion resistance under a severe environment cannot be sufficiently evaluated.

  Patent Document 8 proposes that a Cu—Zn—Si alloy contain Fe. However, Fe and Si form a Fe—Si intermetallic compound that is harder and more brittle than the γ phase. This intermetallic compound has a problem that the life of the cutting tool is shortened during cutting, and a hard spot is formed during polishing, resulting in appearance problems. Moreover, since the additive element Si is consumed as an intermetallic compound, the performance of the alloy is reduced.

  Furthermore, in Patent Document 9, Sn, Fe, Co, and Mn are added to a Cu—Zn—Si alloy, and Fe, Co, and Mn all combine with Si to form a hard and brittle intermetallic compound. Is generated. For this reason, similarly to Patent Document 8, a problem occurs during cutting and polishing. Furthermore, according to Patent Document 9, the β phase is formed by containing Sn and Mn. However, the β phase causes serious dezincification corrosion and increases the sensitivity to stress corrosion cracking.

JP 2008-214760 A International Publication No. 2008/081947 JP 2000-119775 A JP 2000-119774 A International Publication No. 2007/034571 International Publication No. 2006/016442 International Publication No. 2006/016624 JP-T-2006-511792 Japanese Patent Laid-Open No. 2004-263301 U.S. Pat. No. 4,055,445 International Publication No. 2012/057055 JP 2013-104071 A

Genjiro Mima, Shoji Hasegawa, Journal of Copper Technology Research, 2 (1963), pp. 62-77

  The present invention has been made to solve such problems of the prior art, and is a free-cutting copper excellent in corrosion resistance, impact characteristics, ductility, room temperature and high-temperature strength in a fluid having a high flow velocity under severe water quality environment. An object is to provide an alloy and a method for producing a free-cutting copper alloy. In this specification, unless otherwise specified, the corrosion resistance refers to dezincification corrosion resistance. Moreover, a hot work material refers to a hot extrusion material, a hot forging material, and a hot rolling material. High temperature characteristics refer to high temperature creep and tensile strength at about 150 ° C. (100 ° C. to 250 ° C.). The cooling rate refers to an average cooling rate in a certain temperature range.

In order to solve such problems and achieve the above object, the free-cutting copper alloy according to the first aspect of the present invention comprises 76.0 mass% or more and 78.7 mass% or less of Cu, and 3.1 mass. % To 3.6 mass% Si, 0.40 mass% to 0.85 mass% Sn, 0.05 mass% to 0.14 mass% P, and 0.005 mass% to less than 0.020 mass%. Pb, and the balance consists of Zn and inevitable impurities,
The Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, the P content is [P] mass%, and the Pb content is [ Pb] mass%,
75.0 ≦ f1 = [Cu] + 0.8 × [Si] −7.5 × [Sn] + [P] + 0.5 × [Pb] ≦ 78.2
60.0 ≦ f2 = [Cu] −4.8 × [Si] −0.8 × [Sn] − [P] + 0.5 × [Pb] ≦ 61.5,
0.09 ≦ f3 = [P] / [Sn] ≦ 0.30,
And having a relationship
In the constituent phase of the metal structure, the α phase area ratio is (α)%, the β phase area ratio is (β)%, the γ phase area ratio is (γ)%, and the κ phase area ratio is (κ)%. When the area ratio of the μ phase is (μ)%,
30 ≦ (κ) ≦ 65,
0 ≦ (γ) ≦ 2.0,
0 ≦ (β) ≦ 0.3,
0 ≦ (μ) ≦ 2.0,
96.5 ≦ f4 = (α) + (κ),
99.4 ≦ f5 = (α) + (κ) + (γ) + (μ),
0 ≦ f6 = (γ) + (μ) ≦ 3.0,
35 ≦ f7 = 1.05 × (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 70,
And having a relationship
The κ phase is present in the α phase, the long side length of the γ phase is 50 μm or less, and the long side length of the μ phase is 25 μm or less.

  The free-cutting copper alloy according to the second aspect of the present invention is the free-cutting copper alloy according to the first aspect of the present invention, further comprising 0.01 mass% or more and 0.08 mass% or less of Sb, 0.02 mass%. It contains one or two or more selected from As of 0.08 mass% or less and Bi of 0.01 mass% or more and 0.10 mass% or less.

The free-cutting copper alloy according to the third aspect of the present invention includes 76.5 mass% to 78.3 mass% Cu, 3.15 mass% to 3.5 mass% Si, and 0.45 mass% to 0.005. Including 77 mass% or less of Sn, 0.06 mass% or more and 0.13 mass% or less of P, and 0.006 mass% or more and 0.018 mass% or less of Pb, with the balance consisting of Zn and inevitable impurities,
The Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, the P content is [P] mass%, and the Pb content is [ Pb] mass%,
75.5 ≦ f1 = [Cu] + 0.8 × [Si] −7.5 × [Sn] + [P] + 0.5 × [Pb] ≦ 77.7,
60.2 ≦ f2 = [Cu] −4.8 × [Si] −0.8 × [Sn] − [P] + 0.5 × [Pb] ≦ 61.3,
0.10 ≦ f3 = [P] / [Sn] ≦ 0.27
And having a relationship
In the constituent phase of the metal structure, the α phase area ratio is (α)%, the β phase area ratio is (β)%, the γ phase area ratio is (γ)%, and the κ phase area ratio is (κ)%. When the area ratio of the μ phase is (μ)%,
33 ≦ (κ) ≦ 60,
0 ≦ (γ) ≦ 1.5,
0 ≦ (β) ≦ 0.1,
0 ≦ (μ) ≦ 1.0,
97.5 ≦ f4 = (α) + (κ),
99.6 ≦ f5 = (α) + (κ) + (γ) + (μ),
0 ≦ f6 = (γ) + (μ) ≦ 2.0,
38 ≦ f7 = 1.05 × (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 65,
And having a relationship
The κ phase is present in the α phase, the long side length of the γ phase is 40 μm or less, and the long side length of the μ phase is 15 μm or less.

  The free-cutting copper alloy according to the fourth aspect of the present invention is the free-cutting copper alloy according to any one of the first to third aspects of the present invention, wherein the inevitable impurities Fe, Mn, Co, and Cr are the same. The total amount is less than 0.08 mass%.

  The free-cutting copper alloy according to the fifth aspect of the present invention is the free-cutting copper alloy according to any one of the first to fourth aspects of the present invention, wherein the amount of Sn contained in the κ phase is 0.43 mass%. It is 0.90 mass% or less and the amount of P contained in the κ phase is 0.06 mass% or more and 0.22 mass% or less.

The free-cutting copper alloy according to the sixth aspect of the present invention is the free-cutting copper alloy according to any one of the first to fifth aspects of the present invention, wherein the U-notch-shaped Charpy impact test value is 12 J / cm ² or more. The creep strain after holding at 150 ° C. for 100 hours under a load of 45 J / cm ² or less and corresponding to 0.2% proof stress at room temperature is 0.4% or less. To do.
The Charpy impact test value is a value for a U-notch test piece.

The free-cutting copper alloy according to the seventh embodiment of the present invention is a hot-working material according to any one of the first to fifth aspects of the present invention, and is a hot work material, and has a tensile strength S (N / Mm ² ) is 550 N / mm ² or more, elongation E (%) is 12% or more, U-notch-shaped Charpy impact test value I (J / cm ² ) is 12 J / cm ² or more and 45 J / cm ² or less, And 650 ≦ f8 = S × {(E + 100) / 100} ^1/2 , or 665 ≦ f9 = S × {(E + 100) / 100} ^1/2 + I.

  The free-cutting copper alloy according to the eighth aspect of the present invention is the free-cutting copper alloy according to any one of the first to seventh aspects of the present invention. , Pressure vessels, and joints, or automotive parts and electrical parts that come into contact with liquids.

The method for producing a free-cutting copper alloy according to the ninth aspect of the present invention is the method for producing a free-cutting copper alloy according to any one of the first to eighth aspects of the present invention,
One or both of a cold working step and a hot working step, and an annealing step performed after the cold working step or the hot working step,
In the annealing step, the copper alloy is held under any of the following conditions (1) to (4),
(1) Hold at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes to 8 hours,
(2) Hold at a temperature of 515 ° C. or higher and lower than 525 ° C. for 100 minutes to 8 hours,
(3) The maximum temperature reached is 525 ° C. or more and 610 ° C. or less and is maintained for 20 minutes or more in the temperature range from 575 ° C. to 525 ° C., or (4) the temperature range from 575 ° C. to 525 ° C. is 0.1 Cool at an average cooling rate of ℃ / min or more and 2.5 ℃ / min or less,
Next, the temperature range from 460 ° C. to 400 ° C. is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min.

A method for producing a free-cutting copper alloy according to a tenth aspect of the present invention is a method for producing a free-cutting copper alloy according to any one of the first to sixth aspects of the present invention,
A casting process, and an annealing process performed after the casting process,
In the annealing step, the copper alloy is held under any of the following conditions (1) to (4),
(1) Hold at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes to 8 hours,
(2) Hold at a temperature of 515 ° C. or higher and lower than 525 ° C. for 100 minutes to 8 hours,
(3) The maximum temperature reached is 525 ° C. or more and 610 ° C. or less and is maintained for 20 minutes or more in the temperature range from 575 ° C. to 525 ° C., or (4) the temperature range from 575 ° C. to 525 ° C. is 0.1 Cool at an average cooling rate of ℃ / min or more and 2.5 ℃ / min or less,
Next, the temperature range from 460 ° C. to 400 ° C. is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min.

The method for producing a free-cutting copper alloy according to an eleventh aspect of the present invention is the method for producing a free-cutting copper alloy according to any one of the first to eighth aspects of the present invention,
The material temperature at the time of hot working including the hot working process is 600 ° C. or higher and 740 ° C. or lower,
In the cooling process after hot plastic working, the temperature range from 575 ° C. to 525 ° C. is cooled at an average cooling rate of 0.1 ° C./min to 2.5 ° C./min, and 460 ° C. to 400 ° C. The temperature range up to is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min.

A method for producing a free-cutting copper alloy according to a twelfth aspect of the present invention is a method for producing a free-cutting copper alloy according to any one of the first to eighth aspects of the present invention,
One or both of a cold working step and a hot working step, and a low temperature annealing step performed after the cold working step or the hot working step,
In the low temperature annealing step, when the material temperature is in the range of 240 ° C. or more and 350 ° C. or less, the heating time is in the range of 10 minutes or more and 300 minutes or less, the material temperature is T ° C., and the heating time is t minutes, 150 ≦ The condition is (T−220) × (t) ^1/2 ≦ 1200.

  According to the aspect of the present invention, the γ phase, which is excellent in machinability function but is inferior in corrosion resistance, ductility, impact properties, and high temperature strength (high temperature creep), is minimized, and there is no limit to the μ phase effective for machinability. It defines a metal structure in which a κ phase is present in the α phase which is small and effective in strength, machinability, ductility, and corrosion resistance. Furthermore, the composition and manufacturing method for obtaining this metal structure are defined. Therefore, according to the embodiment of the present invention, machinability, corrosion resistance in harsh environments including high-speed fluid, cavitation resistance, erosion corrosion resistance, normal temperature strength, high temperature strength, free wear resistance excellent in wear resistance A copper alloy and a method for producing a free-cutting copper alloy can be provided.

2 is an electron micrograph of the structure of a free-cutting copper alloy (Test No. T05) in Example 1. 2 is a metallographic micrograph of the structure of a free-cutting copper alloy (Test No. T03) in Example 1. 2 is an electron micrograph of the structure of a free-cutting copper alloy (Test No. T03) in Example 1. Test No. 2 in Example 2 It is a metallographic micrograph of the cross section after using it in the severe water environment for 8 years of T401. Test No. 2 in Example 2 It is a metal micrograph of the cross section after the dezincification corrosion test 1 of T402. Test No. 2 in Example 2 It is a metal micrograph of the cross section after the dezincification corrosion test 1 of T63.

Below, the manufacturing method of the free-cutting copper alloy and free-cutting copper alloy which concern on embodiment of this invention is demonstrated.
The free-cutting copper alloy according to the present embodiment is an electrical / automobile / machine / industrial piping member such as a faucet, valve, joint, etc. used for drinking water taken daily by humans and animals. It is used as equipment, parts, pressure vessels and joints that come into contact with liquids.

Here, in this specification, an element symbol with parentheses such as [Zn] indicates the content (mass%) of the element.
In this embodiment, a plurality of compositional relational expressions are defined using the content display method as follows.
Composition relation f1 = [Cu] + 0.8 × [Si] −7.5 × [Sn] + [P] + 0.5 × [Pb]
Composition relation f2 = [Cu] −4.8 × [Si] −0.8 × [Sn] − [P] + 0.5 × [Pb]
Compositional relation f3 = [P] / [Sn]

Further, in the present embodiment, in the constituent phase of the metal structure, the area ratio of the α phase is (α)%, the area ratio of the β phase is (β)%, the area ratio of the γ phase is (γ)%, The area ratio is represented by (κ)%, and the μ phase area ratio is represented by (μ)%. The constituent phase of the metal structure indicates an α phase, a γ phase, a κ phase, and the like, and does not include intermetallic compounds, precipitates, non-metallic inclusions, and the like. The κ phase present in the α phase is included in the area ratio of the α phase. The α ′ phase is included in the α phase. The sum of the area ratios of all the constituent phases is 100%.
In this embodiment, a plurality of organizational relational expressions are defined as follows.
Organizational relationship f4 = (α) + (κ)
Tissue relational expression f5 = (α) + (κ) + (γ) + (μ)
Organizational relation f6 = (γ) + (μ)
Tissue relational expression f7 = 1.05 × (κ) + 6 × (γ) ^1/2 + 0.5 × (μ)

  The free-cutting copper alloy according to the first embodiment of the present invention includes 76.0 mass% to 78.7 mass% Cu, 3.1 mass% to 3.6 mass% Si, and 0.40 mass% or more. It contains Sn of 0.85 mass% or less, P of 0.05 mass% or more and 0.14 mass% or less, and Pb of 0.005 mass% or more and less than 0.020 mass%, with the balance being Zn and inevitable impurities. The compositional relational expression f1 is in the range of 75.0 ≦ f1 ≦ 78.2, the compositional relational expression f2 is in the range of 60.0 ≦ f2 ≦ 61.5, and the compositional relational expression f3 is 0.09 ≦ f3. Within the range of ≦ 0.30. The area ratio of the κ phase is in the range of 30 ≦ (κ) ≦ 65, the area ratio of the γ phase is in the range of 0 ≦ (γ) ≦ 2.0, and the area ratio of the β phase is 0 ≦ (β ) ≦ 0.3, and the area ratio of the μ phase is in the range of 0 ≦ (μ) ≦ 2.0. The organizational relational expression f4 is in the range of 96.5 ≦ f4, the organizational relational expression f5 is in the range of 99.4 ≦ f5, the organizational relational expression f6 is in the range of 0 ≦ f6 ≦ 3.0, The organization relational expression f7 is set in the range of 35 ≦ f7 ≦ 70. The κ phase exists in the α phase. The long side length of the γ phase is 50 μm or less, and the long side length of the μ phase is 25 μm or less.

  The free-cutting copper alloy according to the second embodiment of the present invention includes 76.5 mass% to 78.3 mass% Cu, 3.15 mass% to 3.5 mass% Si, and 0.45 mass% or more. It contains 0.77 mass% or less of Sn, 0.06 mass% or more and 0.13 mass% or less of P, and 0.006 mass% or more and 0.018 mass% or less of Pb, with the balance being Zn and inevitable impurities. The composition relational expression f1 is in the range of 75.5 ≦ f1 ≦ 77.7, the compositional relational expression f2 is in the range of 60.2 ≦ f2 ≦ 61.3, and the composition relational expression f3 is 0.1 ≦ f3. Within the range of ≦ 0.27. The area ratio of the κ phase is in the range of 33 ≦ (κ) ≦ 60, the area ratio of the γ phase is in the range of 0 ≦ (γ) ≦ 1.5, and the area ratio of the β phase is 0 ≦ (β ) ≦ 0.1, and the area ratio of the μ phase is in the range of 0 ≦ (μ) ≦ 1.0. The organizational relational expression f4 is in the range of 97.5 ≦ f4, the organizational relational expression f5 is in the range of 99.6 ≦ f5, the organizational relational expression f6 is in the range of 0 ≦ f6 ≦ 2.0, The organization relational expression f7 is set within the range of 38 ≦ f7 ≦ 65. The κ phase exists in the α phase. The long side length of the γ phase is 40 μm or less, and the long side length of the μ phase is 15 μm or less.

  Moreover, in the free-cutting copper alloy that is the first embodiment of the present invention, Sb of 0.01 mass% or more and 0.08 mass% or less, As of 0.02 mass% or more and 0.08 mass% or less, 0.0. You may contain 1 or 2 or more selected from Bi of 01 mass% or more and 0.10 mass% or less.

  In the free-cutting copper alloys according to the first and second embodiments of the present invention, the total amount of Fe, Mn, Co, and Cr that are inevitable impurities is preferably less than 0.08 mass%.

  Furthermore, in the free-cutting copper alloy according to the first and second embodiments of the present invention, the amount of Sn contained in the κ phase is 0.43 mass% or more and 0.90 mass% or less, and is contained in the κ phase. The amount of P is preferably 0.06 mass% or more and 0.22 mass% or less.

Further, 0 in the free-cutting copper alloy according to the first and second embodiments of the invention, are Charpy impact test value of U notch shape 12 J / cm ² or more 45 J / cm ² or less, and at room temperature. It is preferable that the creep strain after holding the copper alloy at 150 ° C. for 100 hours with a 2% yield strength (a load corresponding to a 0.2% yield strength) is 0.4% or less.
In the free-cutting copper alloy (hot work material) subjected to hot working according to the first and second embodiments of the present invention, tensile strength S (N / mm ² ), elongation E (%), Charpy impact In relation to the test value I (J / cm ² ), the tensile strength S is 550 N / mm ² or more, the elongation E is 12% or more, and the U-notch-shaped Charpy impact test value I is 12 J / cm ² or more and 45 J / cm. ^And f8 = S × {(E + 100) / 100} ^1/2 , which is the product of tensile strength (S) and {1/2 of {(elongation (E) +100) / 100}} It is preferable that the value is 650 or more, or the value of f9 = S × {(E + 100) / 100} ^1/2 + I, which is the sum of f8 and I, is 665 or more.

  The reason why the component composition, the composition relational expressions f1, f2, and f3, the metal structure, the structural relational expressions f4, f5, f6, and f7, and the mechanical characteristics are defined as described above will be described below.

<Ingredient composition>
(Cu)
Cu is a main element of the alloy of the present embodiment, and in order to overcome the problems of the present invention, it is necessary to contain at least 76.0 mass%. When the Cu content is less than 76.0 mass%, depending on the content of Si, Zn, Sn and the manufacturing process, the proportion of the γ phase exceeds 2%, and the dezincification corrosion resistance becomes worse. In addition, stress corrosion cracking resistance, impact characteristics, cavitation resistance, erosion corrosion resistance, ductility, normal temperature strength and high temperature creep are poor. In some cases, a β phase may appear. Therefore, the lower limit of the Cu content is 76.0 mass% or more, preferably 76.5 mass% or more, more preferably 76.8 mass% or more.
On the other hand, when the Cu content exceeds 78.7 mass%, the corrosion resistance, cavitation resistance, erosion corrosion resistance, and strength are not only saturated, but the proportion of the κ phase may be excessive. In addition, a μ phase with a high Cu concentration, and in some cases, a ζ phase and a χ phase are likely to precipitate. As a result, the machinability, impact properties, ductility, and hot workability may be deteriorated depending on the requirements of the metal structure. Therefore, the upper limit of the Cu content is 78.7 mass% or less, preferably 78.3 mass% or less, and preferably 78.0 mass% or less, more preferably 77.7 mass if the ductility and impact properties are considered important. % Or less.

(Si)
Si is an element necessary for obtaining many excellent characteristics of the alloy of the present embodiment. Si contributes to the formation of metal phases such as κ phase, γ phase, and μ phase. Si improves the machinability, corrosion resistance, stress corrosion cracking resistance, cavitation resistance, erosion corrosion resistance, wear resistance, normal temperature strength and high temperature characteristics of the alloy of this embodiment. Regarding machinability, even if Si is contained, the machinability of the α phase is hardly improved. However, due to the presence of phases harder than the α phase such as the γ phase, the κ phase, and the μ phase formed by the inclusion of Si, excellent machinability can be obtained without containing a large amount of Pb. However, as the proportion of the metal phase such as the γ phase and the μ phase increases, the ductility and impact characteristics deteriorate. It becomes inferior in corrosion resistance under severe environments. Furthermore, there is a problem in high temperature creep characteristics that can withstand long-term use. On the other hand, the κ phase is useful for improving machinability, strength, cavitation resistance, and wear resistance. However, if the κ phase is excessive, the ductility, impact properties, and workability are reduced, and in some cases It also deteriorates the machinability. For this reason, it is necessary to define the κ phase, γ phase, μ phase, and β phase within appropriate ranges.

In order to solve these metal structure problems and satisfy all the characteristics, Si needs to be contained in an amount of 3.1 mass% or more, depending on the contents of Cu, Zn, Sn, and the like. The lower limit of the Si content is preferably 3.15 mass% or more, more preferably 3.17 mass% or more, and still more preferably 3.2 mass% or more. At first glance, it is thought that the Si content should be lowered in order to reduce the proportion of the γ phase having a high Si concentration and the μ phase. However, as a result of intensive studies on the blending ratio with other elements and the manufacturing process, it is necessary to define the lower limit of the Si content as described above. Further, although depending on other elements, compositional relational expressions, and manufacturing processes, when the Si content exceeds about 3%, an elongated, needle-like κ phase can be present in the α phase. And the amount of acicular κ phase increases at the Si content of 3.1 mass% to 3.15 mass%. Hereinafter, the κ phase existing in the α phase is also referred to as κ1 phase. The α phase is strengthened by the κ phase present in the α phase, and tensile strength, high temperature strength, machinability, cavitation resistance, erosion corrosion resistance, corrosion resistance, wear resistance, and impact properties are maintained without impairing ductility. Can be improved.
On the other hand, if the Si content is too high, the κ phase becomes excessive, resulting in poor ductility, impact properties, and machinability. For this reason, the upper limit of the Si content is 3.6 mass% or less, preferably 3.5 mass% or less, and when emphasis is placed on ductility and impact characteristics, it is preferably 3.45 mass% or less, more preferably 3.4 mass%. % Or less.

(Zn)
Zn is a main constituent element of the alloy of this embodiment together with Cu and Si, and is an element necessary for improving machinability, corrosion resistance, strength, and castability. In addition, although Zn is made into the remainder, if it is described strongly, the upper limit of Zn content is about 20.5 mass% or less, and a minimum is about 16.5 mass% or more.

(Sn)
Sn greatly improves dezincification corrosion resistance, cavitation resistance, and erosion corrosion resistance under severe conditions, and improves stress corrosion cracking resistance, machinability, and wear resistance. In copper alloys consisting of multiple metal phases (constituent phases), the corrosion resistance of each metal phase is superior or inferior, and even if it eventually becomes two phases of α phase and κ phase, corrosion starts from the phase with inferior corrosion resistance. Corrosion proceeds. Sn increases the corrosion resistance of the α phase, which is the most excellent in corrosion resistance, and at the same time improves the corrosion resistance of the κ phase, which is the second most excellent in corrosion resistance. Sn is about 1.4 times the amount allocated to the κ phase than the amount allocated to the α phase. That is, the Sn amount allocated to the κ phase is about 1.4 times the Sn amount allocated to the α phase. As the amount of Sn is larger, the corrosion resistance of the κ phase is further improved. By increasing the Sn content, the superiority or inferiority of the corrosion resistance between the α phase and the κ phase is almost eliminated, or at least the difference in corrosion resistance between the α phase and the κ phase is reduced, and the corrosion resistance as an alloy is greatly improved.

However, the inclusion of Sn promotes the formation of γ phase or β phase. Although Sn itself does not have an excellent machinability function, the machinability of the alloy is improved as a result by forming a γ phase having an excellent machinability. On the other hand, the γ phase deteriorates the corrosion resistance, ductility, impact characteristics, and high temperature characteristics of the alloy and decreases the strength. In the case of containing about 0.5% Sn, Sn is distributed about 7 times to about 15 times and more in the γ phase than in the α phase. That is, the Sn amount allocated to the γ phase is about 7 to about 15 times the Sn amount allocated to the α phase. The γ phase containing Sn is insufficient to the extent that the corrosion resistance is slightly improved compared to the γ phase not containing Sn. Thus, the inclusion of Sn in the Cu—Zn—Si alloy promotes the formation of the γ phase in spite of increasing the corrosion resistance of the κ phase and the α phase. For this reason, unless the essential elements of Cu, Si, P, and Pb are made to have a more appropriate blending ratio and a proper metal structure including the manufacturing process, the inclusion of Sn increases the corrosion resistance of the κ phase and α phase. Stays slightly elevated. On the other hand, the increase in the γ phase leads to a decrease in the corrosion resistance, ductility, impact properties, high temperature properties and tensile strength of the alloy.
By increasing the concentration of Sn in the α phase and κ phase, the α phase and κ phase are strengthened, and cavitation resistance, erosion corrosion resistance, and wear resistance can be improved. In addition, the elongated κ phase present in the α phase strengthens the α phase and works more effectively on these properties.
Moreover, when Sn is contained in the κ phase, the machinability of the κ phase is improved. The effect is increased by co-addition with P.
Depending on how Sn is utilized, corrosion resistance, cavitation resistance, erosion corrosion resistance, wear resistance, normal temperature strength, high temperature characteristics, impact characteristics, and machinability are greatly affected. If the utilization method is wrong, these characteristics are worsened due to an increase in the γ phase.

By controlling the metal structure including the relational expression and manufacturing process described later, it becomes possible to make a copper alloy excellent in various characteristics. In order to exert such an effect, the lower limit of the Sn content needs to be 0.40 mass% or more, preferably 0.45 mass% or more, more preferably 0.48 mass% or more.
On the other hand, when Sn is contained in excess of 0.85 mass%, the proportion of the γ phase increases regardless of the composition ratio of the composition or the production process. In addition, the amount of Sn dissolved in the κ phase becomes excessive, and the effects on cavitation resistance and erosion corrosion resistance are saturated. Existence of excessive Sn in the κ phase impairs the toughness of the κ phase and lowers the ductility and impact properties of the alloy. The upper limit of the Sn content is 0.85 mass% or less, preferably 0.77 mass% or less, and more preferably 0.70 mass% or less.

(Pb)
The inclusion of Pb improves the machinability of the copper alloy. About 0.003 mass% of Pb is dissolved in the matrix, and Pb exceeding the Pb exists as Pb particles having a diameter of about 1 μm. The machinability of the alloy of the present embodiment basically uses the machinability function of the κ phase, which is harder than the α phase, and the machinability is further improved by providing a different action of soft Pb particles. To do. The alloy of this embodiment has high machinability due to the inclusion of Sn in the κ phase, ensuring the proper amount of κ phase, the presence of the κ1 phase in the α phase, etc. A sufficient effect can be obtained with a small amount. Pb exhibits an effect at 0.005 mass% or more. Preferably it is 0.006 mass% or more.
Pb is harmful to the human body, and the alloy of this embodiment contains a large amount of κ phase and it is difficult to make the γ phase 0%. Therefore, as the Pb content increases, ductility, impact properties, The effect on strength and high temperature characteristics is increased. The alloy of this embodiment already has a high machinability, and considering the influence of the human body and the like, the Pb content is sufficient to be less than 0.020 mass%. Preferably it is 0.018 mass% or less.

(P)
P improves dezincification corrosion resistance, machinability, cavitation resistance, erosion corrosion resistance, and wear resistance under severe environments. In particular, the effect becomes remarkable by adding P together with Sn.
P is approximately twice the amount allocated to the κ phase relative to the amount allocated to the α phase. That is, the P amount allocated to the κ phase is approximately twice the P amount allocated to the α phase. P has a great effect of increasing the corrosion resistance of the α phase, but the addition of P alone has a small effect of increasing the corrosion resistance of the κ phase. P can improve the corrosion resistance of the κ phase by coexisting with Sn, but hardly improves the corrosion resistance of the γ phase. Moreover, the machinability effect of P becomes more effective when both P and Sn are added.
In order to exert these effects, the lower limit of the P content is 0.05 mass% or more, preferably 0.06 mass% or more, more preferably 0.07 mass% or more.
On the other hand, even if P is contained in an amount exceeding 0.14 mass%, not only the corrosion resistance effect is saturated, but also the impact characteristics and ductility are deteriorated due to the increase of the P concentration in the κ phase, and the machinability is also poor. Influence. Moreover, it becomes easy to form a compound of P and Si. For this reason, the upper limit of the content of P is 0.14 mass% or less, preferably 0.13 mass% or less, and more preferably 0.12 mass% or less.

(Sb, As, Bi)
Both Sb and As further improve dezincification corrosion resistance and stress corrosion cracking resistance under a particularly severe environment, like P and Sn.
In order to improve the corrosion resistance by containing Sb, it is necessary to contain Sb in an amount of 0.01 mass% or more, and it is preferable to contain Sb in an amount of 0.015 mass% or more. On the other hand, even if Sb is contained in an amount exceeding 0.08 mass%, the effect of improving the corrosion resistance is saturated, and the γ phase is increased. On the other hand, the Sb content is 0.08 mass% or less, preferably 0.8. It is 06 mass% or less.
Moreover, in order to improve corrosion resistance by containing As, it is necessary to contain As in an amount of 0.02 mass% or more, and 0.025 mass% or more is preferable. On the other hand, since the effect of improving the corrosion resistance is saturated even if As is contained exceeding 0.08 mass%, the content of As is 0.08 mass% or less, and preferably 0.06 mass% or less.
By containing Sb alone, the corrosion resistance of the α phase is improved. Although Sb has a higher melting point than Sn, it is a low melting point metal and behaves similar to Sn. It is more distributed in the γ and κ phases than in the α phase and improves the corrosion resistance of the κ phase. However, Sb hardly has an effect of improving the corrosion resistance of the γ phase, and containing an excessive amount of Sb may increase the γ phase. For this reason, in order to utilize Sb, the γ phase is preferably made 2.0% or less.
As enhances the corrosion resistance of the α phase among Sn, P, Sb, and As. Even if the κ phase is corroded, the corrosion resistance of the α phase is enhanced, so that As serves to stop the corrosion of the α phase that occurs in a chain reaction. However, even when As is added alone or when As is added together with Sn, P, and Sb, the effect of improving the corrosion resistance of the κ phase and γ phase is small.
In addition, when both Sb and As are contained, even if the total content of Sb and As exceeds 0.10 mass%, the effect of improving the corrosion resistance is saturated, and the ductility and impact characteristics are lowered. For this reason, it is preferable that the total content of Sb and As is 0.10 mass% or less.
Bi further improves the machinability of the copper alloy. For that purpose, it is necessary to contain Bi in an amount of 0.01 mass% or more, and it is preferable to contain Bi of 0.02 mass% or more. On the other hand, although the harmfulness of Bi to the human body is uncertain, the upper limit of the Bi content is set to 0.10 mass% or less, preferably 0.05 mass% or less because of its impact on impact characteristics and high temperature characteristics.

(Inevitable impurities)
Examples of inevitable impurities in the present embodiment include Al, Ni, Mg, Se, Te, Fe, Mn, Co, Ca, Zr, Cr, Ti, In, W, Mo, B, Ag, and rare earth elements. .
Conventionally, free-cutting copper alloys are not mainly made of high-quality raw materials such as electrolytic copper and electrolytic zinc, but recycled copper alloys are the main raw materials. In a lower process (downstream process, machining process) in the field, cutting is performed on most members and parts, and a copper alloy that is discarded in a large amount at a rate of 40 to 80 with respect to the material 100 is generated. Examples include chips, scraps, burrs, runners, and products containing manufacturing defects. These discarded copper alloys are the main raw materials. If separation of cutting chips and the like is insufficient, Pb, Fe, Mn, Se, Te, Sn, P, Bi, Sb, As, Ca, Al, Zr, Ni, and rare earths from other free-cutting copper alloys Element is mixed. The cutting chips include Fe, W, Co, Mo and the like mixed from the tool. Since the waste material includes plated products, Ni, Cr, and Sn are mixed therein. Mg, Fe, Te, Se, Cr, Ti, Co, In, and Ni are mixed in pure copper-based scrap. From the point of reuse of resources and cost problems, scraps such as chips containing these elements are used as raw materials up to a certain limit, at least as long as the properties are not adversely affected.
Empirically, Ni is often mixed from scrap or the like, but the amount of Ni is allowed to be less than 0.06 mass%, but the amount of Ni is preferably 0.05 mass% or less.
Fe, Mn, Co, Cr and the like form an intermetallic compound with Si, and in some cases, form an intermetallic compound with P, which affects machinability, corrosion resistance and other characteristics. Although depending on the contents of Cu, Si, Sn, and P and the relational expressions f1 and f2, Fe is likely to be combined with Si, and the inclusion of Fe may consume the same amount of Si as Fe. It promotes the formation of Fe-Si compounds that adversely affect machinability. For this reason, the amount of Fe, Mn, Co, and Cr is preferably 0.05 mass% or less, and more preferably 0.04 mass% or less. Further, Fe easily forms an intermetallic compound with P and not only consumes P but also the intermetallic compound impairs machinability. Therefore, the total content of Fe, Mn, Co, and Cr is preferably less than 0.08 mass%. This total amount (total amount of Fe, Mn, Co, and Cr) is more preferably less than 0.07 mass%, and more preferably less than 0.06 mass% if the raw material circumstances allow.
On the other hand, regarding Ag, Ag is generally regarded as Cu and has almost no influence on various properties. Therefore, it is not necessary to limit it, but it is preferably less than 0.05 mass%.
Te and Se themselves have free-cutting properties and are rare but may be mixed in large amounts. In view of the influence on ductility and impact properties, the content of each of Te and Se is preferably less than 0.03 mass%, and more preferably less than 0.02 mass%.
Each amount of other elements such as Al, Mg, Ca, Zr, Ti, In, W, Mo, B, and rare earth elements is preferably less than 0.03 mass%, more preferably less than 0.02 mass%. More preferably, it is less than 0.01 mass%.
The amount of the rare earth element is a total amount of at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Tb, and Lu. is there.
The amount of these inevitable impurities is desirably controlled and limited in view of the influence on the characteristics of the alloy of this embodiment.

(Composition relational expression f1)
The composition relational expression f1 is an expression showing the relation between the composition and the metallographic structure, and even if the amount of each element is in the range specified above, if the compositional relational expression f1 is not satisfied, the present embodiment is the target. It cannot satisfy the characteristics. In the composition relational expression f1, a large coefficient of −7.5 is given to Sn. When the composition relational expression f1 is less than 75.0, although depending on other relational expressions, the proportion of the γ phase increases and the long side of the γ phase becomes long. As a result, not only the corrosion resistance is deteriorated, but also the strength at normal temperature is lowered, the ductility, impact characteristics and high temperature characteristics are deteriorated, and the cavitation resistance and erosion corrosion resistance are deteriorated. Therefore, the lower limit of the compositional relational expression f1 is 75.0 or more, preferably 75.5 or more, and more preferably 75.8 or more. As the compositional relational expression f1 becomes a more preferable range, the area ratio of the γ phase decreases, and even if the γ phase exists, the γ phase is granulated. That is, it tends to be a γ phase with a short long side, and the corrosion resistance, impact characteristics, ductility, normal temperature strength, and high temperature characteristics are further improved.
On the other hand, the upper limit of the composition relational expression f1 mainly affects the proportion of the κ phase when the Sn content is within the range of the present embodiment. When the compositional relational expression f1 is larger than 78.2, the proportion of the κ phase is excessive, and the μ phase is liable to precipitate. If the κ phase is too much, impact properties, ductility, machinability, hot workability, and erosion corrosion resistance will deteriorate. Therefore, the upper limit of the compositional relational expression f1 is 78.2 or less, preferably 77.7 or less, and more preferably 77.3 or less.
Thus, a copper alloy having excellent characteristics can be obtained by defining the composition relational expression f1 within the above range. Note that the selective elements As, Sb, Bi, and separately unavoidable impurities are not specified in the compositional relational expression f1 because their contents are considered and the compositional relational expression f1 is hardly affected. .

(Composition relational expression f2)
The composition relational expression f2 is an expression representing the relation between composition, workability, various characteristics, and metal structure. When the compositional relational expression f2 is less than 60.0, the proportion of the γ phase in the metal structure increases, and other metal phases such as the β phase tend to appear and remain, and the corrosion resistance, ductility, and impact characteristics are increased. , Cold workability and high temperature strength characteristics are deteriorated. Also, the crystal grains become coarse during hot forging, and cracks are likely to occur. Therefore, the lower limit of the compositional relational expression f2 is 60.0 or more, preferably 60.2 or more, more preferably 60.3 or more.
On the other hand, when the compositional relational expression f2 exceeds 61.5, the hot deformation resistance is increased, the hot deformability is lowered, and there is a possibility that surface cracking occurs in the hot extruded material or the hot forged product. In addition, a coarse α phase having a length in the direction parallel to the hot working direction exceeding 500 μm and a width exceeding 150 μm may appear. If a coarse α phase is present, the machinability is lowered and the strength is lowered. In addition, a long γ phase is likely to exist around the boundary between the coarse α phase and κ phase, resulting in poor corrosion resistance, cavitation resistance, erosion corrosion resistance, high temperature characteristics, and wear resistance. . On the other hand, it also affects the generation of needle-like κ phase existing in the α phase, and the larger the value of f2, the less κ1 phase exists. The upper limit of the compositional relational expression f2 is 61.5 or less, preferably 61.3 or less, more preferably 61.2 or less. Thus, by setting the compositional relational expression f2 in a narrow range, it is possible to obtain good corrosion resistance, erosion corrosion resistance, strength, machinability, hot workability, impact characteristics, and high temperature characteristics.
Note that the selective elements As, Sb, Bi and separately specified inevitable impurities are not specified in the compositional relational expression f2 because their contents are considered and the compositional relational expression f2 is hardly affected. .

(Composition relational expression f3)
Inclusion of Sn in an amount of 0.40 mass% or more particularly improves cavitation resistance and erosion corrosion resistance. In the present embodiment, the γ phase in the metal structure is reduced, and more Sn is effectively contained in the κ phase or α phase. Furthermore, the effect increases more by adding Sn with P. The compositional relational expression f3 is related to the blending ratio of P and Sn, and the value of P / Sn is 0.09 or more and 0.30 or less, that is, the number of P atoms is 1 / n with respect to Sn1 atoms at an atomic concentration. When it is 3 to 1.1, corrosion resistance, cavitation resistance, and erosion corrosion resistance can be improved. f3 is preferably 0.10 or more. Moreover, the preferable upper limit of f3 is 0.27 or less. Below the lower limit of the P / Sn range, the corrosion resistance, cavitation resistance and erosion corrosion resistance are particularly poor. When the upper limit is exceeded, the impact properties and ductility are particularly poor.

(Comparison with patent literature)
Here, Table 1 shows the results of comparing the compositions of the Cu—Zn—Si alloy described in Patent Documents 3 to 12 described above and the alloy of this embodiment.
This embodiment and PTL 3 are different in Pb content. This embodiment and Patent Document 5 differ depending on whether the ratio of P / Sn is specified. This embodiment and PTL 4 are different in Pb content. This embodiment and Patent Documents 6 and 7 differ depending on whether or not Zr is contained. This embodiment differs from Patent Document 8 in whether or not Fe is contained. This embodiment and Patent Document 9 differ depending on whether or not Pb is contained, and also differ in whether or not Fe, Ni, and Mn are contained. Patent Document 10 differs from this embodiment in that it does not contain Sn, P, or Pb. Patent Document 5 is silent about the κ1 phase, f2, and f7 present in the α phase that contributes to strength, machinability, and wear resistance, and has a low strength balance. Patent Document 11 relates to brazing heated to 700 ° C. or higher, and relates to a brazing structure. Patent Document 12 relates to a material that is rolled into a screw or gear.
As described above, the composition range is different between the alloy of the present embodiment and the Cu—Zn—Si alloy described in Patent Documents 3 to 12.

<Metallic structure>
The Cu—Zn—Si alloy has 10 or more types of phases and a complicated phase change occurs, and the target characteristics are not necessarily obtained only by the composition range and the relational expression of the elements. Ultimately, by specifying and determining the type and range of the metal phase present in the metal structure, the desired characteristics can be obtained.
In the case of a Cu—Zn—Si alloy composed of a plurality of metal phases, the corrosion resistance of each phase is not the same and is superior or inferior. Corrosion proceeds starting from the boundary between the phase with the least corrosion resistance, ie, the most susceptible to corrosion, or the phase with poor corrosion resistance and the adjacent phase. In the case of a Cu—Zn—Si alloy composed of three elements of Cu, Zn, and Si, for example, α phase, α ′ phase, β (including β ′) phase, κ phase, γ (including γ ′) phase, μ Comparing the corrosion resistance of the phases, the order of the corrosion resistance is α phase> α ′ phase> κ phase> μ phase ≧ γ phase> β phase in order from the excellent phase. The difference in corrosion resistance between the κ phase and the μ phase is particularly large.

Here, the composition of each phase varies depending on the composition of the alloy and the occupied area ratio of each phase, but the following can be said.
The Si concentration of each phase is, in descending order of concentration, μ phase> γ phase> κ phase> α phase> α ′ phase ≧ β phase. The Si concentration in the μ phase, γ phase and κ phase is higher than the Si concentration of the alloy component. Further, the μ phase Si concentration is about 2.5 to about 3 times the α phase Si concentration, and the γ phase Si concentration is about 2 to about 2.5 times the α phase Si concentration.
The Cu concentration of each phase is, in descending order of concentration, μ phase> κ phase ≧ α phase> α ′ phase ≧ γ phase> β phase. The Cu concentration in the μ phase is higher than the Cu concentration of the alloy.

  In the Cu—Zn—Si alloys disclosed in Patent Documents 3 to 6, the γ phase having the best machinability function coexists mainly with the α ′ phase, or exists at the boundary between the κ phase and the α phase. The γ phase selectively becomes a source of corrosion (starting point of corrosion) under the severe water quality or environment for the copper alloy, and the corrosion proceeds. Of course, if the β phase exists, the β phase corrosion starts before the γ phase corrosion. When the μ phase and the γ phase coexist, the corrosion of the μ phase is slightly delayed from the γ phase or starts almost simultaneously. For example, when the α phase, κ phase, γ phase, and μ phase coexist, and the γ phase and μ phase are selectively dezincified, the corroded γ phase and μ phase are converted into Cu by the dezincification phenomenon. It becomes a rich corrosion product, which corrodes the κ phase or the adjacent α ′ phase, and the corrosion proceeds in a chain reaction.

  In addition, the quality of drinking water in Japan and around the world is various, and the quality of the water is becoming corrosive to copper alloys. For example, due to safety issues to the human body, although there is an upper limit, the concentration of residual chlorine used for disinfecting purposes has increased, and the copper alloy, which is a water supply device, is becoming susceptible to corrosion. It can be said that the corrosion resistance in the use environment where many solutions are present, such as the use environment of the members including the automobile parts, machine parts, and industrial piping, is the same as or more than that of drinking water. In addition, to meet the demands of the times, corrosion resistance under high temperature or high-speed fluid, reliability of high pressure vessels and high pressure valves, or reduction in thickness and weight, high strength, excellent high temperature creep, and cavitation resistance Therefore, a copper alloy member having excellent erosion corrosion resistance is required.

  On the other hand, even if the amount of γ phase or γ phase, μ phase, β phase is controlled, that is, the existence ratio of each phase is greatly reduced or eliminated, the two phases of α phase and κ phase The corrosion resistance of the Cu—Zn—Si alloy is not perfect. Depending on the corrosive environment, the κ phase, which has lower corrosion resistance than the α phase, may be selectively corroded, and it is necessary to improve the corrosion resistance of the κ phase. Further, when the κ phase is corroded, the corroded κ phase becomes a corrosion product rich in Cu, and the corrosion product causes the α phase to corrode. For this reason, it is necessary to improve the corrosion resistance of the α phase.

  The γ phase is a hard and brittle phase, and becomes a stress concentration source microscopically when a large load is applied to the copper alloy member. Since the γ phase is a stress concentration source, it becomes a starting point for chip division during cutting, promotes chip division, and lowers cutting resistance. Thus, although it leads to improvement of machinability, it increases stress corrosion cracking sensitivity and decreases ductility and impact characteristics. Also, the high temperature strength is lowered by the high temperature creep phenomenon. Similar to the γ phase, the μ phase is a hard phase containing a large amount of Si, and mainly exists at the crystal grain boundary of the α phase, the phase boundary of the α phase, and the κ phase. Therefore, like the γ phase, the μ phase becomes a micro stress concentration source. Due to the stress concentration source or the grain boundary sliding phenomenon, the μ phase lowers the ductility and impact characteristics and lowers the high temperature strength. In addition, the γ phase and the μ phase deteriorate cavitation resistance and erosion corrosion resistance. The μ phase is a stress concentration source like the γ phase, but the effect of improving the machinability is smaller than that of the γ phase.

However, in order to improve the corrosion resistance and the above-mentioned characteristics, if the existence ratio of the γ phase, or the γ phase and the μ phase is greatly reduced or eliminated, the inclusion of a small amount of Pb and the α phase and κ phase With only two phases, there is a possibility that satisfactory machinability cannot be obtained. Therefore, on the premise that it contains a small amount of Pb and has excellent machinability, it improves corrosion resistance, ductility, impact properties, strength, high-temperature strength, cavitation resistance, erosion corrosion resistance in harsh usage environments. In order to achieve this, it is necessary to define the constituent phases (metal phase, crystal phase) of the metal structure as follows.
Hereinafter, the unit of the ratio (existence ratio) occupied by each phase is the area ratio (area%).

(Γ phase)
The γ phase is the phase that contributes most to the machinability of Cu-Zn-Si alloys, but has excellent corrosion resistance, cavitation resistance, erosion corrosion resistance, ductility, strength, high temperature characteristics, and impact characteristics in severe environments. To make it easier, the γ phase must be limited. In order to make the corrosion resistance, cavitation resistance and erosion corrosion resistance excellent, it is necessary to contain Sn. However, as the Sn content increases, the γ phase further increases. In order to satisfy these contradictory phenomena, that is, machinability and corrosion resistance at the same time, the contents of Sn and P, compositional relational expressions f1, f2, and f3, a structural relational expression described later, and a manufacturing process are limited.

(Β phase and other phases)
To obtain good corrosion resistance, cavitation resistance, erosion corrosion resistance, high ductility, impact properties, strength, high temperature properties, especially β phase, γ phase, μ phase, and ζ phase in the metal structure The proportion of the other phases is important.
The proportion of the β phase needs to be at least 0% or more and 0.3% or less, preferably 0.1% or less, and most preferably no β phase exists.
The proportion of other phases such as ζ phase other than α phase, κ phase, β phase, γ phase, and μ phase is preferably 0.3% or less, and more preferably 0.1% or less. Optimally, it is preferable that no other phase such as ζ phase exists.

First, in order to obtain excellent corrosion resistance, the proportion of the γ phase must be 0% or more and 2.0% or less, and the length of the long side of the γ phase must be 50 μm or less.
The length of the long side of the γ phase is measured by the following method. For example, using a 500 × or 1000 × metal micrograph, the maximum length of the long side of the γ phase is measured in one field of view. As will be described later, this operation is performed mainly in an arbitrary visual field of five visual fields. The average value of the maximum lengths of the long sides of the γ phase obtained in each field of view is calculated and set as the length of the long sides of the γ phase. For this reason, it can be said that the length of the long side of the γ phase is the maximum length of the long side of the γ phase.
The proportion of the γ phase is preferably 1.5% or less, more preferably 1.0% or less, and further preferably 0.5% or less. Even if the proportion of the γ phase having an excellent machinability function is 0.5% or less, the κ phase improved by the inclusion of Sn and P, the content of a small amount of Pb, and the α phase An excellent machinability as an alloy can be provided by the κ phase (κ1 phase) present therein.
Since the length of the long side of the γ phase affects the corrosion resistance, the length of the long side of the γ phase is 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and optimally 20 μm. It is as follows.
As the amount of γ phase increases, the γ phase is more easily selectively corroded, and the effective elements Sn and P are not effectively distributed to the κ phase. In addition, the longer the γ phase is, the easier it is to be selectively corroded, and the progress of corrosion in the depth direction is accelerated. In the γ phase, the length of the long side of the γ phase as well as the amount of the γ phase affects properties other than the corrosion resistance. The long γ phase is mainly present at the boundary between the α phase and the κ phase, and deteriorates the strength at room temperature, impact characteristics, high temperature characteristics, wear resistance, and cavitation resistance due to the decrease in ductility.

  The proportion of the γ phase and the length of the long side of the γ phase are greatly related to the contents of Cu, Sn, and Si and the compositional relational expressions f1 and f2.

  If the γ phase increases, the ductility, impact properties, normal temperature strength, high temperature strength, stress corrosion cracking resistance, and wear resistance deteriorate, so the γ phase needs to be 2.0% or less, Preferably it is 1.5% or less, More preferably, it is 1.0% or less, More preferably, it is 0.5% or less. The γ phase present in the metal structure becomes a stress concentration source when a high stress is applied. Moreover, coupled with the fact that the crystal structure of the γ phase is BCC, the strength at normal temperature and the high temperature strength are lowered, and the impact characteristics and the stress corrosion cracking resistance are lowered.

(Μ phase)
Since the μ phase affects corrosion resistance, cavitation resistance, erosion corrosion resistance, ductility, impact properties, and high temperature properties, at least the proportion of the μ phase must be 0% or more and 2.0% or less. . The proportion of the μ phase is preferably 1.0% or less, more preferably 0.3% or less, and it is optimal that the μ phase does not exist. The μ phase exists mainly at the grain boundaries and phase boundaries. For this reason, in a severe environment, the μ phase undergoes intergranular corrosion at the crystal grain boundary where the μ phase exists. In addition, when an impact action is applied, cracks starting from the hard μ phase present at the grain boundaries are likely to occur. Further, for example, when copper alloy is used for a valve used around an automobile engine or a high-temperature high-pressure gas valve, if the alloy is kept at a high temperature of 150 ° C. for a long time, the grain boundary slips and creep easily occurs. For this reason, it is necessary to limit the amount of the μ phase, and at the same time, make the length of the long side of the μ phase mainly present at the crystal grain boundaries 25 μm or less. The length of the long side of the μ phase is preferably 15 μm or less, more preferably 5 μm or less, and optimally 2 μm or less.
The length of the long side of the μ phase is measured by the same method as that for measuring the length of the long side of the γ phase. That is, depending on the size of the μ phase, a metal micrograph of 500 times or 1000 times, or a secondary electron image photograph (electron micrograph) of 2000 times or 5000 times, and the length of the μ phase in one field of view. Measure the maximum side length. This operation is performed in any of the five visual fields. The average value of the maximum lengths of the long sides of the μ phase obtained in each field of view is calculated and taken as the length of the long sides of the μ phase. For this reason, it can be said that the length of the long side of the μ phase is the maximum length of the long side of the μ phase.

(Κ phase)
Under recent high-speed cutting conditions, the machinability of the material including cutting resistance and chip discharge is important. However, in the state where the proportion of the γ phase having the most excellent machinability function is limited to 2.0% or less, and the Pb content having the excellent machinability function is limited to less than 0.020 mass%, In order to provide excellent machinability, the proportion of the κ phase needs to be at least 30%. The proportion of the κ phase is preferably 33% or more, more preferably 35% or more.
The κ phase has no brittleness, is much more ductile and has excellent corrosion resistance than the γ phase, μ phase, and β phase. The γ phase and the μ phase exist along the grain boundary and phase boundary of the α phase, but such a tendency is not observed in the κ phase. The κ phase is superior to the α phase in terms of strength, machinability, cavitation, wear resistance, and high temperature characteristics, excluding ductility. The mixed structure of the α phase and κ phase, which is the alloy of this embodiment, has an appropriate phase ratio, and further improves the α phase and κ phase, thereby improving various mechanical properties including machinability and various corrosion resistances. It is possible to create a copper alloy excellent in
As the κ phase increases, the machinability improves, and the tensile strength increases because the κ phase is a hard phase. On the other hand, as the κ phase increases, the ductility and impact properties gradually decrease. When the proportion of the κ phase exceeds 60% and reaches about 2/3, the property that the κ phase is high in strength and hard is superior to the machinability improving function, the cutting resistance is increased, and The severability becomes worse. At the same time, ductility and impact properties are lowered, and the tensile strength is saturated as the ductility is lowered. Therefore, the coexistence of the soft α phase of about 1/3 or more and the hard κ phase of 2/3 or less in the metal structure makes it possible to cut the κ phase rather than the problems of ductility and impact characteristics of the κ phase. Excellent properties such as performance and high strength come into play. In this embodiment, Sn is contained in the κ phase in an amount of about 0.43 mass% to about 0.90 mass%, and the cavitation property, erosion corrosion resistance, corrosion resistance, wear resistance, and machinability of the κ phase. While the function is superior, the ductility and impact characteristics of the κ phase are further reduced. Therefore, in view of machinability, ductility and impact characteristics, the proportion of the κ phase needs to be set to at least 65% or less. The proportion of the κ phase is preferably 60% or less, more preferably 56% or less, and still more preferably 52% or less.
At the same time, an acicular κ phase (κ1 phase) can be present in the α phase depending on the composition and the conditions of the manufacturing process. The presence of the κ phase in the α phase improves the mechanical properties of the α phase itself, such as machinability, strength, high temperature characteristics, and wear resistance, as well as cavitation resistance and erosion corrosion resistance. Can do. As a result, machinability as an alloy, strength at normal temperature, high temperature characteristics, corrosion resistance, cavitation resistance, erosion corrosion resistance, and wear resistance are improved.

(Α phase, its improvement)
The α phase is a main phase forming a matrix, and is a phase that is a source of characteristics of all copper alloys including the alloy of the present embodiment. The α phase has the most ductility and toughness and is a so-called sticky phase. However, the alpha phase stickiness increases the cutting resistance of the alloy and makes the chips continuous. In order to improve the machinability function and mechanical properties of the α phase, Sn is contained in the α phase to slightly reduce its viscosity. When the acicular κ phase (κ1 phase) is present in the α phase, the machinability function of the α phase itself is further improved, and the strength and wear resistance are greatly improved. Therefore, the presence of an appropriate amount of κ1 phase in the α phase enhances the machinability, strength, wear resistance, cavitation resistance, erosion corrosion resistance, and high temperature characteristics of the alloy without impairing ductility and toughness. Thus, in the alloy of this embodiment, the presence of the κ1 phase improves the machinability of the α phase itself, and has an excellent machinability function even with a small amount of Pb.

(Existence of elongated and needle-like κ phase (κ1 phase) in α phase)
When the requirements of the composition and the relational expressions f1, f2 and the process are satisfied, a needle-like κ phase (κ1 phase) is present in the α phase. This κ phase is harder than the α phase. The thickness of the κ phase (κ1 phase) present in the α phase is about 0.1 μm to about 0.2 μm (about 0.05 μm to about 0.5 μm), and the thickness is thin, elongated, and needle-like. It is a feature. The presence of the needle-like κ1 phase in the α phase provides the following effects.
1) The α phase is strengthened and the tensile strength as an alloy is improved.
2) The machinability of the α phase is improved, and the machinability such as reduction of the cutting resistance of the alloy and improvement of chip breaking properties is improved.
3) Since it exists in the α phase, it does not adversely affect the corrosion resistance of the alloy.
4) The α phase is strengthened and the wear resistance of the alloy is improved.
5) Since it exists in the α phase, the effect on ductility and impact properties is negligible.
The acicular κ phase present in the α phase is affected by constituent elements such as Cu, Zn and Si and relational expressions. When the requirements of the composition and metal structure of the present embodiment are satisfied, when the Si amount exceeds about 3.0 mass%, the needle-like κ1 phase starts to exist in the α phase. When the Si amount is about 3.1 mass% to about 3.15 mass%, the κ1 phase is more clearly present in the α phase. However, the presence of the κ1 phase is greatly influenced by the compositional relational expression f2 or f1, and if the value of f2 is large, the κ1 phase is difficult to exist.
On the other hand, if the proportion of the κ1 phase in the α phase becomes large, that is, if the amount of the κ1 phase is too large, the ductility and impact characteristics of the α phase are impaired. As a result, the ductility and impact properties of the alloy are impaired and the strength is reduced. The proportion of the κ1 phase in the α phase is mainly linked to the proportion of the κ phase in the metal structure, and is also influenced by the contents of Cu, Si, Zn and the relational expression. When the proportion of the κ phase exceeds 65%, the proportion of the κ1 phase present in the α phase becomes too large. From the viewpoint of an appropriate amount of κ1 phase present in the α phase, the amount of κ phase in the metal structure is 65% or less, preferably 60% or less. Preferably, it is 56% or less, More preferably, it is 52% or less.
The κ1 phase present in the α phase can be confirmed as a thin linear object or a needle-like object when magnified by a magnification of 500 times and in some cases about 1000 times with a metal microscope. However, since it is difficult to calculate the area ratio of the κ1 phase, the κ1 phase in the α phase is included in the area ratio of the α phase.

(Organizational relational expression f4, f5, f6)
In order to obtain various excellent corrosion resistance, ductility, strength, impact properties, and high temperature properties, the sum of the proportions of the α phase, which is the main phase having excellent ductility and excellent corrosion resistance, and the κ phase (structure relational expression f4 = (α ) + (Κ)) is 96.5% or more. The value of f4 is preferably 97.5% or more, more preferably 98% or more, and optimally 98.5% or more. Since the range of the κ phase is defined, the range of the α phase is generally determined.
Similarly, the sum of the proportions occupied by α phase, κ phase, γ phase, and μ phase (tissue relationship f5 = (α) + (κ) + (γ) + (μ)) is 99.4% or more, 99 .6% or more is preferable.
Further, the total ratio of the γ phase and the μ phase (f6 = (γ) + (μ)) needs to be 0% or more and 3.0% or less. The value of f6 is preferably 2.0% or less, more preferably 1.0% or less, and optimally 0.5% or less.
Here, in the relational expression of the metal structure, f4 to f6, 10 types of metal phases of α phase, β phase, γ phase, δ phase, ε phase, ζ phase, η phase, κ phase, μ phase, and χ phase are represented. The target is not intermetallic compounds, Pb particles, oxides, non-metallic inclusions, undissolved substances, etc. Further, the κ1 phase is included in the α phase, and the μ phase that cannot be observed with a metal microscope of 500 times or 1000 times is excluded. In addition, although the intermetallic compound formed by Si, P, and an element inevitably mixed (for example, Fe, Co, Mn) is not included in the area ratio of the metal phase, it affects the machinability. It is necessary to keep an eye on.

(Organizational relational expression f7)
The alloy of this embodiment is excellent in machinability in the Cu—Zn—Si alloy while minimizing the content of Pb harmful to the human body. In particular, it is necessary to satisfy all of excellent corrosion resistance, cavitation resistance, erosion corrosion resistance, impact characteristics, ductility, wear resistance, normal temperature strength, and high temperature characteristics. However, machinability and excellent corrosion resistance and impact characteristics are contradictory characteristics.
In terms of metal structure, the machinability is better if it contains a larger amount of the γ phase, which is the most excellent in machinability, but the γ phase must be reduced in terms of corrosion resistance, impact properties, and other characteristics. When the proportion of the γ phase is 2.0% or less, it has been found from the experimental results that the value of the above-described structural relational expression f7 is in an appropriate range in order to obtain good machinability. .

Regarding the structural relational expression f7 regarding machinability, the γ phase has the best machinability, and particularly when the γ phase is small, that is, when the area ratio of the γ phase is 2.0% or less, the machinability is effectively made machinable. Contribute. For this reason, a coefficient six times higher than that of the κ phase is given to the square root of the ratio (%) occupied by the γ phase. Moreover, since the κ phase contains Sn, the machinability of the κ phase is improved. For this reason, a coefficient of 1.05 is given to the κ phase, and this coefficient is more than twice the coefficient of the μ phase. In order to obtain good machinability, the structure relational expression f7 is required to be 35 or more, preferably 38 or more, and more preferably 42 or more.
On the other hand, when the structural relational expression f7 exceeds 70, the cutting resistance increases and the chip breaking property also deteriorates. And an impact characteristic and ductility worsen, and intensity | strength also becomes low with ductility fall. For this reason, the organization relational expression f7 is 70 or less, preferably 65 or less, more preferably 60 or less, and still more preferably 55 or less.

(Amount of Sn and P contained in κ phase)
In order to improve the corrosion resistance of the κ phase, Sn is contained in the alloy in an amount of 0.43 mass% to 0.90 mass% and P is contained in an amount of 0.06 mass% to 0.22 mass%. Is preferred.
In the alloy of this embodiment, when the Sn content is within the above range, when the Sn amount allocated to the α phase is 1, the κ phase is about 1.4, the γ phase is about 7 to about 15 , Sn is allocated to the μ phase at a ratio of about 2. For example, in the case of the alloy of this embodiment, in the Cu—Zn—Si alloy containing 0.5 mass% of Sn, the proportion of the α phase is 50%, the proportion of the κ phase is 49%, and the proportion of the γ phase is In the case of 1%, the Sn concentration in the α phase is about 0.38 mass%, the Sn concentration in the κ phase is about 0.53 mass%, and the Sn concentration in the γ phase is about 4 mass%. If the area ratio of the γ phase is large, the amount of Sn consumed (consumed) in the γ phase increases, and the amount of Sn allocated to the κ phase and the α phase decreases. Therefore, when the amount of γ phase is reduced, Sn is effectively used for corrosion resistance and machinability as described later.
On the other hand, when the amount of P allocated to the α phase is 1, P is allocated at a ratio of about 2 for the κ phase, about 3 for the γ phase, and about 4 for the μ phase. For example, in the case of the alloy of this embodiment, in a Cu—Zn—Si alloy containing 0.1 mass% of P, the proportion of α phase is 50%, the proportion of κ phase is 49%, and the proportion of γ phase Is 1%, the P concentration in the α phase is about 0.06 mass%, the P concentration in the κ phase is about 0.12 mass%, and the P concentration in the γ phase is about 0.18 mass%.

  Both Sn and P elements improve the corrosion resistance of the α phase and the κ phase, but the amount of Sn and P contained in the κ phase is about each compared to the amount of Sn and P contained in the α phase. 1.4 times and about 2 times. That is, the amount of Sn contained in the κ phase is about 1.4 times the amount of Sn contained in the α phase, and the amount of P contained in the κ phase is about 2 times the amount of P contained in the α phase. Is double. For this reason, the degree of improvement in the corrosion resistance of the κ phase is superior to the degree of improvement in the corrosion resistance of the α phase. As a result, the corrosion resistance of the κ phase approaches that of the α phase. When the P / Sn ratio (f3) is appropriate, cavitation resistance, erosion corrosion resistance, and corrosion resistance are further improved.

  When the content of Sn in the copper alloy is 0.40 mass% or less, there is a problem in cavitation resistance and erosion corrosion resistance under severe conditions. This problem can be solved by increasing the Sn content, increasing the concentrations of Sn and P in the κ phase, and controlling the concentration ratio of P and Sn. At the same time, the corrosion resistance is improved. In addition, when a large amount of Sn is distributed in the κ phase, the machinability of the κ phase is improved, and thus the loss of machinability due to the decrease in the γ phase can be compensated.

  On the other hand, Sn is largely distributed to the γ phase, but even if a large amount of Sn is contained in the γ phase, the corrosion resistance of the γ phase is hardly improved, and the effect of improving cavitation resistance and erosion corrosion resistance is small. . This is presumably due to the fact that the crystal structure of the γ phase is a BCC structure. On the contrary, when the proportion of the γ phase is large, the amount of Sn allocated to the κ phase decreases, and the degree of improvement in the corrosion resistance, cavitation resistance, and erosion corrosion resistance of the κ phase decreases. For this reason, the Sn concentration contained in the κ phase is preferably 0.43 mass% or more, more preferably 0.47 mass% or more, and further preferably 0.54 mass% or more. Originally, the κ phase is inferior in ductility and toughness to the α phase, but when the Sn concentration in the κ phase reaches 1 mass%, the ductility and toughness of the κ phase are further impaired. Therefore, the Sn concentration contained in the κ phase is preferably 0.90 mass% or less, more preferably 0.84 mass% or less, and further preferably 0.78 mass% or less. When Sn is contained in a predetermined amount in the κ phase, the corrosion resistance, cavitation resistance and erosion corrosion resistance are improved, and the machinability and wear resistance are also improved without greatly impairing the ductility and toughness.

As in the case of Sn, when a large amount of P is distributed to the κ phase, the corrosion resistance, cavitation resistance, and erosion corrosion resistance are improved, and the machinability of the κ phase is improved. However, when P is excessively contained, P is consumed in the formation of an intermetallic compound with Si, which deteriorates the characteristics, or the solid solution of excess P in the κ phase is caused by the ductility of the κ phase. , Impairing toughness, impairing impact properties and ductility as an alloy, and causing a decrease in strength due to a decrease in ductility. The P concentration contained in the κ phase is preferably 0.06 mass% or more, more preferably 0.07 mass% or more, and further preferably 0.08 mass% or more. The upper limit of the P concentration contained in the κ phase is preferably 0.22 mass% or less, more preferably 0.19 mass% or less, and further preferably 0.16 mass% or less.
By adding both P and Sn, corrosion resistance, cavitation resistance, erosion corrosion resistance, and machinability are improved.

<Characteristic>
(Normal temperature strength and high temperature strength)
Tensile strength is regarded as important as a necessary strength in various fields including joints, piping, valves, automobile valves, hydrogen stations, containers in a high-pressure hydrogen environment such as hydrogen power generation. In the case of a pressure vessel, the allowable stress is affected by the tensile strength. For example, valves used in environments close to the engine room of automobiles and high-temperature / high-pressure valves are used in a temperature environment of up to about 150 ° C. At that time, they may not be deformed or destroyed when pressure or stress is applied. Required. Since the alloy of this embodiment does not cause hydrogen embrittlement, if it has high strength, the allowable stress and the allowable pressure increase, and it can be used more safely in applications related to hydrogen.
For this purpose, the hot extruded material and the hot forged material, which are hot-worked materials, are preferably high-strength materials having a tensile strength at room temperature of 550 N / mm ² or more. The tensile strength at normal temperature is preferably 565 N / mm ² or more, more preferably 575 N / mm ² or more, and most preferably 590 N / mm ² or more. A hot forged alloy having a high tensile strength of 590 N / mm ² or more and free cutting properties is not found except for the alloy of this embodiment. Hot forgings are generally not cold worked. For example, the surface can be cured by shots, but it is only a cold work rate of about 0.1 to 2.5%, and the improvement in tensile strength is about ² to 40 N / mm ² . The pressure resistance performance depends on the tensile strength, and high tensile strength is required for a member to which pressure is applied, such as a pressure vessel and valves. For this reason, the forging material of this embodiment is suitable for the members to which pressure is applied, such as these pressure vessels and valves.
The alloy of this embodiment is improved in tensile strength by heat treatment under an appropriate temperature condition higher than the recrystallization temperature of the material or by applying an appropriate thermal history. Specifically, it is improved by about 10 to about 60 N / mm ² depending on the composition and heat treatment conditions, compared with the hot-worked material before the heat treatment. In addition to age-hardening alloys such as Corson alloy and Ti-Cu, there are almost no examples of copper alloys that increase in tensile strength due to heat treatment at a temperature higher than the recrystallization temperature. The reason why the strength is improved in the alloy of this embodiment is considered as follows. By performing the heat treatment under an appropriate condition of 515 ° C. or more and 575 ° C. or less, the α phase and κ phase of the matrix become soft. On the other hand, the presence of acicular κ phase in the α phase strengthens the α phase, increases the ductility due to the decrease in the γ phase, increases the maximum load that can withstand fracture, and the proportion of the κ phase. The increase greatly exceeds the softening of the α and κ phases. In the alloy of this embodiment, by making these metallographic structures, not only the corrosion resistance but also the tensile strength, ductility, impact value, and cold workability are greatly improved as compared with the hot-worked material before heat treatment. Finished in a high strength, high ductility, high toughness alloy.
On the other hand, the hot-worked material is drawn, drawn, and rolled cold after an appropriate heat treatment to improve the strength. In the alloy of the present embodiment, when cold working is performed, when the cold working rate is 15% or less, the tensile strength increases by about 12 N / mm ^{2 for} each cold working rate of 1%. On the other hand, impact characteristics and Charpy impact test values are reduced by about 4% for a cold work rate of 1%. Or, the impact value I ₀ of the _{heat-treated,} when the cold working ratio and RE%, the impact value I _R after cold working is generally the following conditions 20% cold working ratio, I R ₌ I ₀ × It can be organized by {20 / (20 + RE)}. For example, when a cold-worked material is produced by subjecting an alloy material having a tensile strength of 570 N / mm ² and an impact value of 30 J / cm ² to cold drawing at a cold work rate of 5%, The tensile strength of the material is about 630 N / mm ² and the impact value is about 24 J / cm ² . If the cold working rate is different, the tensile strength and impact value cannot be determined uniquely. Thus, when cold working is performed, the tensile strength increases, but the impact value and elongation decrease. It is necessary to set an appropriate cold working rate in order to obtain target strength, elongation, and impact value according to the application.
Regarding high-temperature strength (characteristics), the creep strain after exposing (holding) a copper alloy to 150 ° C. for 100 hours with a stress corresponding to 0.2% proof stress at room temperature being 0.4% or less. It is preferable. This creep strain is more preferably 0.3% or less, and still more preferably 0.2% or less. Thereby, it is difficult to deform even when exposed to high temperature, and a copper alloy having excellent high temperature strength is obtained.

(Normal temperature strength, ductility, cold workability)
Even if the machinability is good and the tensile strength is high, the use is limited when the ductility and toughness are poor. Machinability requires a kind of brittleness in the material because chips are cut during cutting. Tensile strength and ductility are contradictory properties, but it is desirable that a high balance can be achieved between tensile strength and ductility (elongation). In a heat-processed material or a material that has been cold-worked before and after heat treatment, including a heat treatment step, the tensile strength is 550 N / mm ² or more, the elongation is 12% or more, and tensile The product of the strength (S) and {(elongation (E%) + 100) / 100} to the 1/2 power, f8 = S × {(E + 100) / 100} ^1/2 value is 650 or more. It is a measure of one high strength and high ductility material. f8 is more preferably 665 or more, and further preferably 680 or more.
In addition, about a casting, since a crystal grain tends to become coarse and a micro defect may be included, it does not apply.

Incidentally, in the case of free-cutting brass containing 60 mass% Cu, 3 mass% Pb and the balance containing Pb composed of Zn and inevitable impurities, the tensile strength at room temperature of the hot extruded material and hot forged product is in ^{360N / mm 2 ~400N / mm 2} , elongation is 35% to 45%. That is, f8 is about 450. Further, the creep strain after the alloy is exposed to 150 ° C. for 100 hours under a stress corresponding to 0.2% proof stress at room temperature is about 4 to 5%. For this reason, the tensile strength and heat resistance of the alloy of this embodiment are a very high level compared with the free-cutting brass containing the conventional Pb. That is, the alloy of this embodiment is excellent in various corrosion resistances, has a high strength at room temperature, and is hardly deformed even when exposed to a high temperature for a long time by adding the high strength. It becomes possible. In particular, forging materials such as high-pressure valves and high-pressure hydrogen valves cannot be cold-worked, so that high strength can be utilized to increase the allowable pressure, or to reduce the thickness and weight.
The high temperature characteristics of the alloy of the present embodiment are substantially the same for hot forged materials, extruded materials, and cold worked materials. In other words, the 0.2% yield strength is increased by cold working, but the creep after the alloy is exposed to 150 ° C. for 100 hours even when a load corresponding to the high 0.2% yield is applied. The strain is 0.4% or less and high heat resistance is provided. The high temperature characteristics are mainly influenced by the area ratios of the β phase, γ phase, and μ phase, and the higher the area ratio, the worse. In addition, the high temperature characteristics become worse as the long side lengths of the α phase crystal grain boundaries and the μ phase and γ phase existing at the phase boundary are longer.

(Impact resistance)
Generally, when a material has high strength, it becomes brittle. It is said that a material excellent in chip breaking property in cutting has some kind of brittleness. Impact characteristics and machinability, impact characteristics and strength are contradictory characteristics in a certain aspect.
However, when copper alloy is used for various parts such as drinking water appliances such as valves and fittings, automobile parts, machine parts, industrial piping, etc., copper alloy is not only high strength but also against impact. It must be able to withstand More specifically, when subjected to Charpy impact test at U-notch test piece, Charpy impact test value is preferably not 12 J / cm ² or more, more preferably 14J / cm ² or more, more preferably 16J / cm ² or more. In particular, for hot-worked materials and hot-forged materials that have not been cold worked, the Charpy impact test value is preferably 14 J / cm ² or more, more preferably 16 J / cm ² or more, and even more preferably. 18 J / cm ² or more. The alloy of this embodiment relates to an alloy having excellent machinability, and the Charpy impact test value does not need to exceed 45 J / cm ² . On the contrary, if the Charpy impact test value exceeds 45 J / cm ² , the toughness and the viscosity of the material increase, so that the cutting resistance becomes high and the machinability becomes worse, for example, chips are easily connected. For this reason, the Charpy impact test value is preferably 45 J / cm ² or less.
When the amount of hard κ phase increases, the amount of acicular κ phase present in α phase increases, the Sn concentration in κ phase increases, and the amount of acicular κ phase present in α phase increases Strength and machinability are increased, but toughness, that is, impact properties are decreased. For this reason, strength, machinability, and toughness (impact characteristics) are contradictory characteristics. The following formula defines a strength / ductility / impact balance index f9 in which impact properties are added to strength / ductility.
Regarding the hot-worked material, the tensile strength (S) is 550 N / mm ² or more, the elongation (E) is 12% or more, the Charpy impact test value (I) is 12 J / cm ² or more, and S and {(E + 100 ) / 100} 1/2 power and I, f9 = S × {(E + 100) / 100} ^1/2 + I is preferably 665 or more, more preferably 680 or more, and even more preferably 690 or more. It can be said that it is a material having high strength, ductility, and toughness.
Impact properties (toughness) and ductility are similar properties, but the strength / ductility balance index f8 is 650 or more, or the strength / ductility / impact balance index f9 (hereinafter, f8 and f9 are also referred to as strength balance indexes). Preferably satisfies any of 665 or more.

The impact characteristics of the alloy of the present embodiment are also closely related to the metal structure, and the γ phase deteriorates the impact characteristics. Further, if the μ phase is present at the phase boundary of the α phase crystal grain boundary, the α phase, the κ phase, and the γ phase, the crystal grain boundary and the phase boundary are weakened and the impact characteristics are deteriorated.
As a result of research, it has been found that the impact characteristics are particularly deteriorated when a μ phase having a long side exceeding 25 μm exists at the grain boundary or phase boundary. For this reason, the length of the long side of the existing μ phase is 25 μm or less, preferably 15 μm or less, more preferably 5 μm or less, and optimally 2 μm or less. At the same time, the μ phase existing at the crystal grain boundary is more easily corroded in a harsh environment than the α phase and the κ phase, causing intergranular corrosion and deteriorating high-temperature characteristics. In the case of the μ phase, if the occupation ratio is small, the length of the μ phase is short, and the width is narrow, it is difficult to confirm with a metal microscope having a magnification of about 500 times or 1000 times. When the length of the μ phase is 5 μm or less, the μ phase may be observed at a grain boundary or a phase boundary when observed with an electron microscope having a magnification of 2000 times or 5000 times.

(Relationship between properties and κ phase)
Although there is a tradeoff with ductility and toughness, the tensile strength increases when the amount of hard κ phase is larger than α phase. At the same time, since the κ phase has a good machinability function and excellent wear resistance, the proportion of the κ phase needs to be 30% or more, preferably 33% or more, more preferably 35% or more. It is. On the other hand, when the proportion of the κ phase exceeds 65%, the toughness and ductility are remarkably lowered, and the tensile strength is lowered as the ductility is lowered. When the hard κ phase coexists with the soft α phase, the effect on the machinability by the κ phase can be exhibited. However, when the proportion of the κ phase exceeds 65%, not only the effect cannot be exhibited, but also the cutting resistance increases, and the chip breaking property deteriorates. For this reason, the proportion of the κ phase is preferably 60% or less, more preferably 56% or less, and still more preferably 52% or less. Further, when an appropriate amount of Sn is contained in the κ phase, the corrosion resistance is improved, and the machinability, strength, and wear resistance of the κ phase are also improved. On the other hand, as the content of Sn in the κ phase increases, the ductility and impact properties of the κ phase decrease. By making the proportion of the κ phase in the metal structure and the Sn content in the κ phase appropriate and more preferable, it is possible to balance machinability, strength, ductility, impact properties, and various corrosion resistances. For this purpose, the relational expressions f1 and f2 are important.

(Κ phase within α phase (κ1 phase))
Depending on the composition and process conditions, an acicular κ phase can be present in the α phase. Specifically, normally, α-phase crystal grains and κ-phase crystal grains exist independently, but in the case of the alloy of this embodiment, acicular κ is formed inside the α-phase crystal grains. There can be multiple phases. Thus, by the presence of the κ phase in the α phase, the α phase is appropriately strengthened, and the tensile strength, wear resistance, and machinability are improved without significantly impairing the ductility and toughness.
From a certain aspect, cavitation resistance is affected by wear resistance, strength, and corrosion resistance, and erosion corrosion resistance is affected by corrosion resistance and wear resistance. In particular, when the amount of κ phase is large, when the κ1 phase is present in the α phase, and when the Sn concentration in the κ phase is high, the cavitation resistance is improved. In order to improve the erosion-corrosion resistance, it is most effective to increase the Sn concentration in the κ phase, and if the κ1 phase is present in the α phase, it becomes even better. Regarding the cavitation resistance and erosion corrosion resistance, the Sn concentration in the κ phase is more important than the Sn concentration of the alloy, and the Sn concentration in the κ phase is 0.43 mass%, 0.47%, and 0.54%. As it increases, both properties become even better. What is important together with the Sn concentration in the κ phase is the corrosion resistance of the alloy. This is because when a copper alloy is actually used, when the material is corroded and a corrosion product is formed, the corrosion product easily peels off under a high-speed fluid, and a new new surface. Is exposed. And it repeats corrosion and peeling. The tendency can also be judged in the accelerated test (corrosive accelerated test).
In the alloy of the present embodiment, Sn is contained, and the γ phase is limited to 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less. As a result, the amount of Sn dissolved in the κ phase and the α phase is increased, and the corrosion resistance, wear resistance, erosion corrosion resistance, and cavitation resistance are greatly improved.

<Manufacturing process>
Next, the manufacturing method of the free-cutting copper alloy which concerns on 1st, 2nd embodiment of this invention is demonstrated.
The metal structure of the alloy of this embodiment changes not only by the composition but also by the manufacturing process. In addition to being affected by the hot working temperature and heat treatment conditions of hot extrusion and hot forging, the average cooling rate (also referred to simply as the cooling rate) during the cooling process in hot working and heat treatment is also affected. As a result of diligent research, in the cooling process of hot working and heat treatment, the cooling rate in the temperature range of 460 ° C. to 400 ° C. and the cooling rate in the temperature range of 575 ° C. to 525 ° C., particularly 570 ° C. to 530 ° C. It turns out that the organization is greatly affected.
The manufacturing process of this embodiment is a process necessary for the alloy of this embodiment and has a balance with the composition, but basically plays the following important role.
1) Decrease the γ phase that deteriorates the corrosion resistance and impact properties, and reduce the length of the long side of the γ phase.
2) The μ phase that deteriorates the corrosion resistance and impact characteristics is controlled, and the length of the long side of the μ phase is controlled.
3) The acicular κ phase (κ1 phase) appears in the α phase.
4) Decreasing the amount of γ phase and increasing the amount (concentration) of Sn dissolved in the κ phase and α phase.

(Melting casting)
Melting is performed at about 950 ° C. to about 1200 ° C., which is about 100 ° C. to about 300 ° C. higher than the melting point (liquidus temperature) of the alloy of this embodiment. Casting and castings are performed at about 900 ° C. to about 1100 ° C., which is about 50 ° C. to about 200 ° C. above the melting point. It is cast into a predetermined mold and cooled by several cooling means such as air cooling, gradual cooling, and water cooling. And, after solidification, the constituent phases change variously.

(Hot processing, hot extrusion)
Examples of hot working include hot extrusion and hot forging.
For example, with regard to hot extrusion, although depending on the equipment capacity, the material temperature when actually being hot worked, specifically, the condition immediately after passing through an extrusion die (hot working temperature) is 600 to 740 ° C. It is preferable to carry out hot extrusion. When hot working at a temperature exceeding 740 ° C., a large amount of β phase is formed during plastic working, a β phase may remain, and a large amount of γ phase remains, which adversely affects the constituent phase after cooling. Moreover, even if it heat-processes at the next process, the metal structure of a hot work material will influence. The hot working temperature is preferably 670 ° C. or lower, and more preferably 645 ° C. or lower. When hot extrusion is carried out at 645 ° C. or lower, the γ phase of the hot extruded material is reduced. Further, the α phase becomes a fine grain shape, and the strength is improved. When a hot-forged material and a heat-treated material after hot forging are produced using the hot-extruded material having a small γ-phase, the amount of γ-phase in the hot-forged material and the heat-treated material becomes smaller.
On the other hand, when the hot working temperature is low, the hot deformation resistance increases. From the viewpoint of deformability, the lower limit of the hot working temperature is preferably 600 ° C. or higher. When the extrusion ratio is 50 or less or when hot forging into a relatively simple shape, hot working can be performed at 600 ° C. or higher. The lower limit of the hot working temperature is preferably 605 ° C. with a margin. Although depending on the equipment capacity, the hot working temperature is preferably as low as possible.
In view of the measurement position where actual measurement is possible, the hot working temperature is defined as the temperature of the hot work material that can be measured approximately 3 seconds or 4 seconds after hot extrusion, hot forging, and hot rolling. To do. The metal structure is affected by the temperature immediately after machining that has undergone large plastic deformation.

The brass alloy containing Pb in an amount of 1 to 4 mass% occupies most of the extruded material of the copper alloy, but in the case of this brass alloy, except for those having a large extruded diameter, for example, those having a diameter exceeding about 38 mm, Typically, it is wound into a coil after hot extrusion. The ingot (billet) being extruded is deprived of heat by the extrusion device and the temperature is lowered. The extruded material is deprived of heat by contacting the winding device, and the temperature further decreases. A decrease in temperature of about 50 ° C. to 100 ° C. from the temperature of the ingot at the beginning of extrusion or from the temperature of the extruded material occurs at a relatively fast cooling rate. The coil wound after that is cooled at a relatively slow cooling rate of about 2 ° C./min in the temperature range from 460 ° C. to 400 ° C., depending on the weight of the coil, etc., due to the heat retaining effect. . When the material temperature reaches about 300 ° C., the subsequent cooling rate is further slowed down, so that water cooling may be performed in consideration of handling. In the case of a brass alloy containing Pb, hot extrusion is performed at about 600 to 800 ° C., but a large amount of β phase rich in hot workability exists in the metal structure immediately after extrusion. When the cooling rate after extrusion is high, a large amount of β phase remains in the metal structure after cooling, resulting in poor corrosion resistance, ductility, impact properties, and high temperature properties. In order to avoid this, the β phase is changed to the α phase by cooling at a relatively slow cooling rate utilizing the heat retention effect of the extruded coil, and a metal structure rich in the α phase is obtained. As described above, since the cooling rate of the extruded material is relatively fast immediately after extrusion, the subsequent cooling is slowed down to form a metal structure rich in α-phase. In addition, although patent document 1 does not have a description of a cooling rate, it discloses that it is gradually cooled until the temperature of the extruded material becomes 180 ° C. or less for the purpose of reducing the β phase and isolating the β phase.
As described above, the alloy of the present embodiment is manufactured at a cooling rate completely different from the conventional method for manufacturing a brass alloy containing Pb.

(Hot forging)
As a material for hot forging, a hot extruded material is mainly used, but a continuous cast bar is also used. Compared to hot extrusion, since hot forging is processed into a complex shape, the temperature of the material before forging is high. However, the temperature of the hot forging material subjected to large plastic working, which is the main part of the forged product, that is, the material temperature after about 3 seconds or 4 seconds after forging is from 600 ° C. as in the case of the hot extruded material. 740 ° C is preferred.
And at the time of cooling after hot forging, the temperature range from 575 ° C. to 525 ° C. is cooled at a cooling rate of 0.1 ° C./min to 2.5 ° C./min. Next, the temperature range from 460 ° C. to 400 ° C. is cooled at a cooling rate of 2.5 ° C./min to 500 ° C./min. The cooling rate in the temperature range of 460 ° C. to 400 ° C. is more preferably 4 ° C./min or more, and further preferably 8 ° C./min or more. This prevents an increase in μ phase.
Furthermore, a material having various properties such as corrosion resistance and machinability can be obtained by devising the cooling rate after forging. That is, the temperature of the forged material is about 600 ° C. or more and 740 ° C. or less after about 3 seconds or 4 seconds after hot forging. When cooling at a cooling rate of 0.1 ° C./min to 2.5 ° C./min in a temperature range of 575 ° C. to 525 ° C., particularly in a temperature range of 570 ° C. to 530 ° C., γ The phase decreases. The lower limit value of the cooling rate in the temperature region from 575 ° C. to 525 ° C. is set to 0.1 ° C./min or more in consideration of economy, while when the cooling rate exceeds 2.5 ° C./min, γ The reduction in the amount of phase is insufficient. Preferably it is 1.5 degrees C / min or less, More preferably, it is 1 degrees C / min or less. Cooling at a cooling rate of 2.5 ° C./min or less in a temperature range of 575 ° C. or more and 525 ° C. or less is a condition equivalent to maintaining the temperature range of 525 ° C. or more and 575 ° C. or less for 20 minutes or more, which will be described later. As a result, the metal structure can be improved.
The cooling rate in the temperature range from 460 ° C. to 400 ° C. is 2.5 ° C./minute or more and 500 ° C./minute or less, preferably 4 ° C./minute or more, more preferably 8 ° C./minute or more. This prevents an increase in μ phase. Thus, in the temperature range of 575 to 525 ° C., cooling is performed at a cooling rate of 2.5 ° C./min or less, preferably 1.5 ° C./min or less. In the temperature range of 460 to 400 ° C., cooling is performed at a cooling rate of 2.5 ° C./min or more, preferably 4 ° C./min or more. As described above, the cooling rate is decreased in the temperature range of 575 to 525 ° C., and the cooling rate is increased in the temperature range of 460 ° C. to 400 ° C., thereby achieving a more suitable material. When heat treatment is performed in the next step or the final step, it is not necessary to control the cooling rate in the temperature range of 575 ° C. to 525 ° C. after the hot working in the temperature range of 460 ° C. to 400 ° C. .

(Heat treatment)
The main heat treatment of copper alloy is also called annealing. For example, when processing into a small size that cannot be extruded by hot extrusion, after cold drawing or cold drawing, heat treatment is performed as necessary and recrystallization is performed. That is, it is performed for the purpose of softening the material. Moreover, also in a hot work material, heat processing is implemented as needed, when the material which hardly has a process distortion is requested | required, when making it an appropriate metal structure.
Also in the brass alloy containing Pb, heat treatment is performed as necessary. In the case of the brass alloy containing Bi of Patent Document 1, it is heat-treated at 350 to 550 ° C. for 1 to 8 hours.
In the case of the alloy according to the present embodiment, first, when the alloy is held at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes or more and 8 hours or less, corrosion resistance, impact properties, high temperature properties, strength, and ductility are improved. However, if heat treatment is performed under conditions where the temperature of the material exceeds 610 ° C., a large amount of γ phase or β phase is formed, and the α phase becomes coarse. As the heat treatment conditions, the temperature of the heat treatment is preferably 575 ° C. or lower. On the other hand, although heat treatment at a temperature lower than 525 ° C. is possible, the degree of decrease of the γ phase is rapidly reduced and it takes time. At a temperature of at least 515 ° C. and less than 525 ° C., a time of 100 minutes or more, preferably 120 minutes or more is required. Further, in the heat treatment for a long time at a temperature lower than 515 ° C., the decrease of the γ phase remains little or hardly decreases, and the μ phase appears depending on the conditions. The heat treatment time (time kept at the heat treatment temperature) needs to be kept at a temperature of 525 ° C. or higher and 575 ° C. or lower for at least 20 minutes. Since the retention time contributes to the decrease of the γ phase, it is preferably 40 minutes or more, more preferably 80 minutes or more. The upper limit of the holding time is 8 hours, and is 480 minutes or less, preferably 240 minutes or less from the economical viewpoint. Or as above-mentioned, at the temperature of 515 degreeC or more and less than 525 degreeC, it is 100 minutes or more, Preferably it is 120 minutes or more and 480 minutes (8 hours) or less. The advantage of heat treatment at a temperature of 515 ° C. or more and less than 525 ° C. is that when the amount of the γ phase of the material before the heat treatment is small, the softening of the α phase and the κ phase is minimized, and there is almost no growth of the α phase grains. , Higher strength can be obtained.
As another heat treatment method, in the case of a continuous heat treatment furnace in which a hot-extruded material, a hot-forged product, a hot-rolled material, or a material that has been cold-drawn or drawn is moved in a heat source, the material temperature When the temperature exceeds 610 ° C., it is a problem as described above. However, once the temperature of the material is raised to 525 ° C. or higher and 610 ° C. or lower, preferably 595 ° C. or lower, and then maintained at a temperature range of 525 ° C. or higher and 575 ° C. or lower for 20 minutes or longer, that is, 525 ° C. The total of the time held in the temperature range of 575 ° C. or lower and the time required to pass through the temperature range of 525 ° C. or higher and 575 ° C. or lower after cooling is 20 minutes or longer, thereby improving the metal structure. It becomes possible. In the case of a continuous furnace, since the time for which the maximum temperature is maintained is short, the cooling rate in the temperature region from 575 ° C. to 525 ° C. is preferably 2.5 ° C./min or less, more preferably 2 ° C / min or less, more preferably 1.5 ° C / min or less. Of course, the set temperature is not less than 575 ° C. For example, when the maximum temperature reached is 545 ° C, the holding time when the temperature from 545 ° C to 525 ° C is at least 20 minutes or more reaches 545 ° C is 0 minutes. In this case, it may be passed under the condition that the cooling rate is 1 ° C./min or less. The definition of the holding time is not limited to a continuous furnace, and is defined as the time from when the maximum temperature reached minus 10 ° C.
In these heat treatments as well, the material is cooled to room temperature, but in the cooling process, the cooling rate in the temperature range of 460 ° C. to 400 ° C. needs to be 2.5 ° C./min or more and 500 ° C./min or less. Preferably it is 4 degrees C / min or more. That is, it is necessary to increase the cooling rate around 500 ° C. Generally, in cooling from a furnace, the cooling rate is slower at a lower temperature, for example, 430 ° C. than 550 ° C.

When the metallographic structure is observed with an electron microscope of 2000 times or 5000 times, the cooling rate at the boundary whether or not the μ phase is present is about 8 ° C./min in the temperature range from 460 ° C. to 400 ° C. In particular, the critical cooling rate that greatly affects various properties is about 2.5 ° C./min, or about 4 ° C./min. Of course, the appearance of the μ phase also depends on the composition, and the higher the Cu concentration, the higher the Si concentration, and the higher the value of the relational expression f1 of the metal structure, the faster the μ phase is formed.
That is, when the cooling rate in the temperature range from 460 ° C. to 400 ° C. is slower than about 8 ° C./min, the length of the long side of the μ phase precipitated at the grain boundary reaches about 1 μm, and further as the cooling rate becomes slower. grow up. When the cooling rate is about 5 ° C./min, the length of the long side of the μ phase is about 3 μm to 10 μm. When the cooling rate is less than about 2.5 ° C./min, the length of the long side of the μ phase exceeds 15 μm, and in some cases exceeds 25 μm. When the length of the long side of the μ phase reaches about 10 μm, the μ phase can be distinguished from the grain boundary with a 1000 × metal microscope, and can be observed. On the other hand, the upper limit of the cooling rate depends on the hot working temperature, but if the cooling rate is too fast (over 500 ° C / min), the constituent phase formed at high temperature is brought to room temperature as it is, and the κ phase Increases and the β phase and γ phase that affect the corrosion resistance and impact properties increase.

  Currently, brass alloys containing Pb account for most of the extruded materials of copper alloys. In the case of this brass alloy containing Pb, as disclosed in Patent Document 1, it is heat-treated as necessary at a temperature of 350 to 550 ° C. The lower limit of 350 ° C. is a temperature at which recrystallization occurs and the material is almost softened. At the upper limit of 550 ° C., recrystallization is completed and the recrystallized grains start to become coarse. In addition, there is an energy problem due to raising the temperature, and the β phase significantly increases when heat treatment is performed at a temperature higher than 550 ° C. For this reason, it is thought that an upper limit is 550 degreeC. As a general production facility, a batch furnace or a continuous furnace is used. In the case of a batch furnace, after the furnace is cooled, it is cooled to air after reaching about 300 ° C. or about 200 ° C. In the case of a continuous furnace, it is cooled at a relatively slow rate until the material temperature falls to about 300 ° C. Cooling is performed at a cooling rate different from that of the method for producing the alloy of the present embodiment.

  Regarding the metal structure of the alloy of this embodiment, what is important in the manufacturing process is the cooling rate in the temperature range of 460 ° C. to 400 ° C. in the cooling process after heat treatment or after hot working. When the cooling rate is less than 2.5 ° C./min, the proportion of the μ phase increases. The μ phase is mainly formed around crystal grain boundaries and phase boundaries. Under severe conditions, the μ phase has poor corrosion resistance compared to the α phase and κ phase, which causes selective corrosion and intergranular corrosion of the μ phase. Also, the μ phase, like the γ phase, becomes a stress concentration source or causes grain boundary sliding, and lowers impact characteristics and high-temperature strength. Preferably, in the cooling after hot working, the cooling rate in the temperature range of 460 ° C. to 400 ° C. is 2.5 ° C./min or more, preferably 4 ° C./min or more, more preferably 8 ° C./min. More than a minute. The upper limit of the cooling rate is preferably 500 ° C./min or less, more preferably 300 ° C./min or less in consideration of the influence of thermal strain.

(Cold working process)
In order to improve the dimensional accuracy or to make the extruded coil straight, the hot extruded material may be cold worked. For example, the hot extruded material is subjected to cold drawing at a processing rate of about 2% to about 20%, preferably about 2% to about 15%, more preferably about 2% to about 10%, and heat treatment is performed. Is done. Alternatively, after hot working and then heat treatment, cold drawing is performed at a working rate of about 2% to about 20%, preferably about 2% to about 15%, more preferably about 2% to about 10%. In some cases, a correction process is added. Depending on the dimensions of the final product, cold working and heat treatment may be repeated. Note that the straightness of the bar may be improved only by the straightening equipment, or shot peening may be applied to the forged product after hot working, and the actual cold working rate is about 0.1% to about 2 Although it is about 5%, the strength increases even with a slight cold working rate.
The advantage of cold working is that the strength of the alloy can be increased. By combining cold working at a processing rate of 2% to 20% and heat treatment for hot-worked materials, even if the order is reversed, high strength, ductility, and impact characteristics must be balanced. Depending on the purpose, strength-oriented, ductility and toughness-oriented characteristics can be obtained.
When the heat treatment according to this embodiment is performed after cold working at a processing rate of 2 to 15%, both the α phase and the κ phase are sufficiently recovered by the heat treatment, but the two phases are processed without being completely recrystallized. Strain remains. At the same time, while the γ phase decreases, the acicular κ phase (κ1 phase) exists in the α phase, the α phase is strengthened, and the κ phase increases. As a result, all of the ductility, impact properties, tensile strength, high temperature properties, and strength / ductility balance index exceed the hot-worked material. In a copper alloy that is widely used as a free-cutting copper alloy, if it is heated to 525 ° C. to 575 ° C. after cold working of 2 to 15%, the strength is greatly reduced by recrystallization. .
On the other hand, after heat treatment, if cold working is performed at an appropriate cold working rate, the ductility and impact properties are lowered, but the material is finished with higher strength, and the balance index f8 reaches 670 or more, or f9 reaches 680 or more. be able to.
By adopting such a manufacturing process, the alloy is excellent in corrosion resistance and excellent in impact characteristics, ductility, strength, and machinability.

(Low temperature annealing)
In the bar material and the forged product, the bar material and the forged product may be annealed at a low temperature below the recrystallization temperature for the purpose of removing residual stress and correcting the bar material. As conditions for the low temperature annealing, it is desirable that the material temperature is 240 ° C. or higher and 350 ° C. or lower, and the heating time is 10 minutes to 300 minutes. Further, assuming that the temperature (material temperature) of low-temperature annealing is T (° C.) and the heating time is t (minutes), low-temperature annealing is performed under the conditions satisfying the relationship of 150 ≦ (T−220) × (t) ^1/2 ≦ 1200. It is preferable to implement. Here, the heating time t (minutes) is counted (measured) from a temperature (T-10) that is 10 ° C. lower than the temperature at which the predetermined temperature T (° C.) is reached.

When the temperature of the low-temperature annealing is lower than 240 ° C., the residual stress is not sufficiently removed and correction cannot be performed sufficiently. When the temperature of the low temperature annealing exceeds 350 ° C., the μ phase is formed around the crystal grain boundary and the phase boundary. If the low-temperature annealing time is less than 10 minutes, the residual stress is not sufficiently removed. When the low-temperature annealing time exceeds 300 minutes, the μ phase increases. As the temperature of the low-temperature annealing is increased or the time is increased, the μ phase increases, and the corrosion resistance, impact characteristics, and high-temperature strength decrease. However, by performing low-temperature annealing, the precipitation of the μ phase is unavoidable, and how to keep the precipitation of the μ phase to a minimum while removing the residual stress is a point.
The lower limit of the value of (T−220) × (t) ^1/2 is 150, preferably 180 or more, more preferably 200 or more. Moreover, the upper limit of the value of (T−220) × (t) ^1/2 is 1200, preferably 1100 or less, and more preferably 1000 or less.

(Casting heat treatment)
Even when the final product is a casting, the metal structure can be improved by subjecting the casting that has been cooled to room temperature after casting to heat treatment under any of the following conditions.
Hold at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes to 8 hours, or hold at a temperature of 515 ° C. or more and less than 525 ° C. for 100 minutes to 8 hours. Alternatively, the temperature of the material is once increased to 525 ° C. or more and 610 ° C. or less, and then held in a temperature region of 525 ° C. or more and 575 ° C. or less for 20 minutes or more. Alternatively, a temperature corresponding to that, specifically, a temperature range of 525 ° C. or more and 575 ° C. or less is cooled at a cooling rate of 0.1 ° C./min or more and 2.5 ° C./min or less.
Next, by cooling the temperature range from 460 ° C. to 400 ° C. at a cooling rate of 2.5 ° C./min to 500 ° C./min, it becomes possible to improve the metal structure, corrosion resistance, wear resistance, erosion resistance Corrosion property can be improved.
In addition, since the crystal grain of the casting is coarse and defects of the casting exist, the strength balance characteristics of tensile strength, elongation, and f8 and f9 are not applied.

By such a manufacturing method, the free-cutting copper alloy according to the first and second embodiments of the present invention is manufactured.
The hot working process, the heat treatment (also called annealing) process, and the low temperature annealing process are processes for heating the copper alloy. Regardless of whether or not cold working is performed, when the low temperature annealing process is not performed, or when the hot working process or the heat treatment process is performed after the low temperature annealing process (when the low temperature annealing process is not the last step for heating the copper alloy). Of the hot working process and the heat treatment process, the process to be performed later is important. When the hot working process is performed after the heat treating process or when the heat treating process is not performed after the hot working process (when the hot working process is the last step of heating the copper alloy), the hot working process is It is necessary to satisfy the heating conditions and the cooling conditions described above. When the heat treatment step is performed after the hot working step or when the hot working step is not performed after the heat treatment step (when the heat treatment step is the last step for heating the copper alloy), the heat treatment step is performed under the heating conditions described above. It is necessary to satisfy the cooling conditions. For example, when the heat treatment step is not performed after the hot forging step, the hot forging step needs to satisfy the above-described hot forging heating conditions and cooling conditions. When the heat treatment step is performed after the hot forging step, the heat treatment step needs to satisfy the heating condition and the cooling condition of the heat treatment described above. In this case, the hot forging process does not necessarily satisfy the above-described hot forging heating conditions and cooling conditions.
In the low-temperature annealing step, the material temperature is 240 ° C. or more and 350 ° C. or less, and this temperature is related to whether or not the μ phase is generated, and the temperature range in which the γ phase decreases (575 to 525 ° C., 525 to 515 ° C.). It doesn't matter. Thus, the material temperature in the low-temperature annealing process is not related to the increase or decrease of the γ phase. For this reason, when a low temperature annealing process is performed after a hot working process or a heat treatment process (when the low temperature annealing process is the last step for heating a copper alloy), the conditions before the low temperature annealing process are performed together with the conditions of the low temperature annealing process. The heating conditions and cooling conditions of the process (the process of heating the copper alloy immediately before the low-temperature annealing process) are important, and the processes before the low-temperature annealing process and the low-temperature annealing process must satisfy the above-described heating conditions and cooling conditions. . In detail, in the process before the low-temperature annealing process, the heating condition and the cooling condition of the subsequent process among the hot working process and the heat treatment process are important, and the above-described heating condition and cooling condition must be satisfied. When performing a hot working process or a heat treatment process after a low temperature annealing process, the process performed later is important among the hot working process and the heat treatment process as described above, and it is necessary to satisfy the heating condition and the cooling condition described above. A hot working process or a heat treatment process may be performed before or after the low temperature annealing process.

  According to the free-cutting alloys according to the first and second embodiments of the present invention configured as described above, the alloy composition, composition relational expression, metal structure, and structural relational expression are defined as described above. Therefore, it is excellent in corrosion resistance, impact characteristics, and high temperature characteristics in harsh environments. Moreover, even if there is little content of Pb, the outstanding machinability can be obtained.

  The embodiment of the present invention has been described above, but the present invention is not limited to this, and can be appropriately changed without departing from the technical requirements of the present invention.

  Hereinafter, the result of the confirmation experiment conducted to confirm the effect of the present invention will be shown. In addition, the following Examples are for demonstrating the effect of this invention, Comprising: The requirements, the process, and conditions which were described in the Example do not limit the technical scope of this invention.

Example 1
<Actual operation experiment>
The trial production of the copper alloy was carried out using the low-frequency melting furnace and semi-continuous casting machine used in actual operation. Tables 2 and 3 show the alloy compositions. Since actual operating equipment was used, impurities were also measured in the alloys shown in Tables 2 and 3. The manufacturing process was performed under the conditions shown in Tables 6 to 12.

(Process No. A1-A12, AH1-AH11)
A billet having a diameter of 240 mm was manufactured by a low-frequency melting furnace and a semi-continuous casting machine which are actually operated. The raw material used was based on actual operation. The billet was cut to a length of 800 mm and heated. Hot extrusion was performed to form a round bar shape with a diameter of 25.6 mm and wound around a coil (extruded material). Next, by adjusting the temperature of the coil and adjusting the fan, the cooling rate in the temperature range of 575 ° C. to 525 ° C. is set to 20 ° C./min, and the cooling rate in the temperature range of 460 ° C. to 400 ° C. is set to 15 ° C./min. The extruded material was cooled. Even in a temperature range of 400 ° C. or lower, cooling was performed at a cooling rate of about 15 ° C./min. The temperature was measured using a radiation thermometer centering on the final stage of hot extrusion, and the temperature of the extruded material was measured about 3 to 4 seconds after being extruded from the extruder. In addition, Daido Special Steel Co., Ltd. model DS-06DF radiation thermometer was used for temperature measurement.
The average value of the temperature of the extruded material is within ± 5 ° C. of the temperature shown in Tables 6 and 7 ((temperature shown in Tables 6 and 7) −5 ° C. to (temperature shown in Tables 6 and 7) + 5 ° C.). I confirmed that there was.
Step No. For AH11, the extrusion temperature was 580 ° C. In steps other than step AH11, the extrusion temperature was 640 ° C. Process No. with an extrusion temperature of 580 ° C. In AH11, all three types of prepared materials could not be extruded to the end, and abandoned.
After extrusion, the process No. In AH1, only correction was performed. Step No. In AH2, an extruded material having a diameter of 25.6 mm was cold drawn to a diameter of 25.0 mm.
Step No. In A1 to A9 and AH3 to AH10, an extruded material having a diameter of 25.6 mm was cold drawn to a diameter of 25.0 mm. The drawn material was heated and held at a predetermined temperature and time in an electric furnace in actual operation, an electric furnace in a laboratory, or a continuous furnace in a laboratory. Alternatively, the maximum reached temperature was changed, and the cooling rate in the temperature range of 575 ° C. to 525 ° C. or the cooling rate in the temperature range of 460 ° C. to 400 ° C. was changed.
Step No. In A10 and A11, the extruded material having a diameter of 25.6 mm was heat-treated. Next, the process No. In A10 and A11, cold drawing rates of about 5% and about 8% were applied, respectively, and the diameters were 25 mm and 24.5 mm, respectively, and correction was performed (drawing and correction after heat treatment).
Step No. A12 is process No. except that the dimension after drawing is φ24.5 mm. It is the same process as A1.
Regarding the heat treatment conditions, as shown in Tables 6 and 7, the temperature of the heat treatment was changed from 505 ° C. to 620 ° C., and the holding time was also changed from 5 minutes to 180 minutes.
In the following table, the case where cold drawing was performed before the heat treatment was indicated by “◯”, and the case where it was not performed was indicated by “−”.
Alloy No. Regarding S01, the molten metal was transferred to a holding furnace, and Sn and Fe were additionally contained. Alloy No. For S02, the molten metal was transferred to a holding furnace and Pb was additionally contained. For the alloys S01 and S02, the process No. EH1 or process no. E1 was applied and evaluated.

(Process No. B1-B3, BH1-BH3)
Step No. The material (bar material) having a diameter of 25 mm obtained in A10 was cut into a length of 3 m. Next, the bars were arranged in a mold and annealed at a low temperature for the purpose of correction. The low-temperature annealing conditions at that time were the conditions shown in Table 9.
In addition, the value of the conditional expression in the table is the value of the following expression.
(Conditional expression) = (T−220) × (t) ^1/2
T: temperature (material temperature) (° C.), t: heating time (min)
As a result, the process No. Only BH1 had poor linearity in all of the three types of materials prepared, so the subsequent characteristic investigation (except for the analysis of the metal structure) was not performed.

(Process No. C0, C1)
An ingot (billet) having a diameter of 240 mm was manufactured by a low-frequency melting furnace and a semi-continuous casting machine that are actually operated. The raw material used was based on actual operation. The billet was cut to a length of 500 mm and heated. Then, hot extrusion was performed to obtain a round bar-shaped extruded material having a diameter of 50 mm. This extruded material was extruded on an extrusion table in the form of a straight bar. The temperature was measured using a radiation thermometer centered on the end of extrusion, and the temperature of the extruded material was measured about 3 to 4 seconds after being extruded from the extruder. It was confirmed that the average value of the temperature of the extruded material was ± 5 ° C. of the temperature shown in Table 10 ((temperature shown in Table 10) −5 ° C. to (temperature shown in Table 10) + 5 ° C.). The cooling rate from 575 ° C. to 525 ° C. and the cooling rate from 460 ° C. to 400 ° C. after extrusion were 16 ° C./min and 12 ° C./min (extruded material). In the process described later, the process No. The extruded material (round bar) obtained in C0 was used as a forging material. Step No. C1 was heated at 560 ° C. for 80 minutes, and then the cooling rate from 460 ° C. to 400 ° C. was set to 12 ° C./min.

(Process No. D1-D7, DH1-DH7)
Step No. A 50 mm diameter round bar obtained at C0 was cut to a length of 180 mm. This round bar was placed horizontally and forged to a thickness of 16 mm with a press machine having a hot forging press capacity of 150 tons. The temperature was measured using a radiation thermometer after about 3 seconds to about 4 seconds from immediately after hot forging to a predetermined thickness. The hot forging temperature (hot working temperature) is within the range of the temperature ± 5 ° C. shown in Table 11 ((temperature shown in Table 11) −5 ° C. to (temperature shown in Table 11) + 5 ° C.). It was confirmed.
Step No. In D1 to D4, DH2, DH6, and DH7, heat treatment is performed in a laboratory electric furnace, and the heat treatment temperature, time, cooling rate in the temperature range of 575 ° C. to 525 ° C., and temperature range of 460 ° C. to 400 ° C. The cooling rate was changed.
Step No. In D5, D7, DH3, and DH4, heating was performed at 565 ° C. to 590 ° C. for 3 minutes in a continuous furnace in the laboratory, and the cooling rate was changed.
In addition, the temperature of heat processing is the highest ultimate temperature of a material, As the holding time, the time hold | maintained in the temperature range from the highest ultimate temperature to (maximum ultimate temperature -10 degreeC) was employ | adopted.
Step No. In DH1, D6, and DH5, the cooling after hot forging was performed by changing the cooling rate in the temperature range of 575 ° C. to 525 ° C. and 460 ° C. to 400 ° C. In all cases, the preparation of the sample was completed by cooling after forging.

<Laboratory experiment>
A prototype test of a copper alloy was conducted using laboratory equipment. Tables 4 and 5 show the alloy compositions. The balance is Zn and inevitable impurities. Copper alloys having the compositions shown in Tables 2 and 3 were also used in laboratory experiments. The manufacturing process was performed under the conditions shown in Table 13 to Table 17.

(Process No. E1, EH1)
In the laboratory, the raw materials were dissolved at a predetermined component ratio. A molten metal was cast into a mold having a diameter of 100 mm and a length of 180 mm to produce a billet. In addition, a billet was produced by casting a part of the molten metal into a mold having a diameter of 100 mm and a length of 180 mm from a melting furnace that is actually operated. This billet is heated, and step No. E1 and EH1 were extruded into round bars with a diameter of 40 mm.
Immediately after the extrusion tester stopped, temperature measurement was performed using a radiation thermometer. As a result, this corresponds to the temperature of the extruded material after about 3 seconds or 4 seconds after being extruded from the extruder.
Step No. In EH1, the sample preparation operation was completed by extrusion, and the obtained extruded material was used as a hot forging material in the steps described later.
Step No. In E1, heat treatment was performed under the conditions shown in Table 13 after extrusion.
Step No. The extruded materials obtained with EH1 and E1 were also used as materials for evaluating hot workability.

(Process No. F1-F5, FH1, FH2)
Step No. EH1 and process No. described later. A round bar 40 mm in diameter obtained with PH1 was cut into a length of 180 mm. Step No. EH1 round bar or process no. The PH1 casting was placed horizontally and forged to a thickness of 15 mm with a press machine having a hot forging press capacity of 150 tons. About 3 seconds to 4 seconds after immediately after hot forging to a predetermined thickness, temperature was measured using a radiation thermometer. The hot forging temperature (hot working temperature) is within the range of the temperature ± 5 ° C. shown in Table 14 ((temperature shown in Table 14) −5 ° C. to (temperature shown in Table 14) + 5 ° C.). It was confirmed.
The cooling rate in the temperature range from 575 ° C. to 525 ° C. after the hot forging and the cooling rate in the temperature range from 460 ° C. to 400 ° C. were set to 22 ° C./min and 18 ° C./min, respectively. Step No. In FH1, the process No. Although the hot forging was performed on the round bar obtained by EH1, the sample preparation operation was completed by cooling after the hot forging.
Step No. In F1, F2, F3 and FH2, the process No. Hot forging was performed on the round bar obtained by EH1, and heat treatment was performed after hot forging. Heat treatment was performed by changing the cooling rate in the temperature range from 575 ° C. to 525 ° C. and the cooling rate in the temperature range from 460 ° C. to 400 ° C.
Step No. In F4 and F5, hot forging was performed using a casting (No. PH1) cast in a mold as a forging material. After hot forging, heat treatment was performed by changing heating conditions and cooling rate.

(Process No. P1-P3, PH1)
Step No. In PH1, a melt obtained by melting a raw material at a predetermined component ratio was cast into a mold having an inner diameter of φ40 mm to obtain a casting. In addition, from the melting furnace actually operated, a part of the molten metal was cast into a mold having an inner diameter of 40 mm to produce a casting.
Step No. In PC, a continuous casting rod having a diameter of 40 mm was produced by continuous casting (not shown in the table).
Step No. In P1, the process No. Heat treatment was applied to the casting of PH1, In P2 and P3, the process No. The PC casting was heat treated. Step No. In P1 to P3, heat treatment was performed by changing heating conditions and cooling rates.

  About the above-mentioned test material, metal structure observation, corrosion resistance (dezincification corrosion test / immersion test), and machinability were evaluated by the following procedures.

(Observation of metal structure)
The metal structure was observed by the following method, and the area ratio (%) of α phase, κ phase, β phase, γ phase, and μ phase was measured by image analysis. The α ′ phase, β ′ phase, and γ ′ phase were included in the α phase, β phase, and γ phase, respectively.
The bar and the forged product of each test material were cut in parallel to the longitudinal direction or parallel to the flow direction of the metal structure. Next, the surface was polished (mirror polished) and etched with a mixed solution of hydrogen peroxide and ammonia water. In the etching, an aqueous solution obtained by mixing 3 mL of 3 vol% hydrogen peroxide water and 22 mL of 14 vol% ammonia water was used. The metal polishing surface was immersed in this aqueous solution at a room temperature of about 15 ° C. to about 25 ° C. for about 2 seconds to about 5 seconds.
Using a metal microscope, the metal structure was observed mainly at a magnification of 500 times, and depending on the state of the metal structure, the metal structure was observed at a magnification of 1000 times. In a five-view micrograph, each phase (α phase, κ phase, β phase, γ phase, μ phase) was manually painted using image processing software “Photoshop CC”. Next, binarization was performed with image analysis software “WinROOF2013” to obtain the area ratio of each phase. Specifically, for each phase, the average value of the area ratios of five fields of view was obtained, and the average value was used as the phase ratio of each phase. The total area ratio of all the constituent phases was set to 100%.
The length of the long side of the γ phase and μ phase was measured by the following method. When it was difficult to discriminate mainly 500 times, a metal microscope photograph of 1000 times was used, and the maximum length of the long side of the γ phase was measured in one field of view. This operation was performed in five arbitrary fields of view, and the average value of the maximum lengths of the long sides of the obtained γ phase was calculated to obtain the long side length of the γ phase. Similarly, depending on the size of the μ phase, a 500 × or 1000 × metal microscope photograph or a 2000 × or 5000 × secondary electron image photograph (electron micrograph) is used, and the length of the μ phase in one field of view. The maximum side length was measured. This operation was performed in five arbitrary fields of view, and the average value of the maximum lengths of the long sides of the obtained μ phase was calculated to obtain the length of the long side of the μ phase.
Specifically, evaluation was performed using photographs printed out to a size of about 70 mm × about 90 mm. In the case of magnification of 500 times, the size of the observation visual field was 276 μm × 220 μm.

When the phase was difficult to identify, the phase was specified at a magnification of 500 times or 2000 times by the FE-SEM-EBSP (Electron Back Scattering Diffraction Pattern) method.
Moreover, in the Example which changed the cooling rate, in order to confirm the presence or absence of the micro phase which mainly precipitates in a crystal grain boundary, using JSM-7000F made from JEOL Ltd., acceleration voltage 15kV, current value ( Using the setting value 15) and JXA-8230 manufactured by JEOL Ltd., a secondary electron image was taken under the conditions of an acceleration voltage of 20 kV and a current value of 3.0 × 10 ⁻¹¹ A, and 2000 times or 5000 The metal structure was confirmed at double magnification. Even if the μ phase could be confirmed by a secondary electron image of 2000 times or 5000 times, the area ratio was not calculated when the μ phase could not be confirmed by a 500 or 1000 times metallographic micrograph. That is, the μ phase, which was observed in a secondary electron image of 2000 times or 5000 times but could not be confirmed in a metal micrograph of 500 times or 1000 times, was not included in the area ratio of the μ phase. This is because the μ phase that cannot be confirmed with a metal microscope mainly has a long side length of 5 μm or less and a width of 0.3 μm or less, and therefore has a small effect on the area ratio.
The length of the μ phase was measured in five arbitrary visual fields, and the average value of the longest length of the five visual fields was defined as the length of the long side of the μ phase as described above. Confirmation of the composition of the μ phase was performed with the attached EDS. In addition, although the μ phase could not be confirmed at 500 times or 1000 times, when the length of the long side of the μ phase was measured at a higher magnification, the area ratio of the μ phase was 0% in the measurement results in the table. However, the length of the long side of the μ phase is shown.

(Observation of μ phase)
Regarding the μ phase, after the hot extrusion or heat treatment, the presence of the μ phase could be confirmed when the temperature range of 460 ° C. to 400 ° C. was cooled at a cooling rate of 8 ° C./min or 15 ° C./min or less. FIG. An example of the secondary electron image of T05 (alloy No. S01 / process No. A3) is shown. It was confirmed that the μ phase was precipitated in the α phase crystal grain boundary (white gray elongated phase).

(Acicular κ phase present in α phase)
The acicular κ phase (κ1 phase) present in the α phase has a width of about 0.05 μm to about 0.5 μm, and has an elongated linear shape and a needle shape. If the width is 0.1 μm or more, the presence can be confirmed even with a metal microscope.
FIG. 2 shows test No. 1 as a representative metal micrograph. The metal micrograph of T03 (alloy No. S01 / process No. A1) is shown. FIG. 3 is an electron micrograph of a needle-like κ phase existing in a typical α phase. The electron micrograph of T03 (alloy No. S01 / process No. A1) is shown. 2 and 3 are not identical. In copper alloys, there is a risk of being confused with twins existing in the α phase, but the κ phase existing in the α phase has a narrow width of the κ phase itself, and two twins form one set. So you can distinguish. In the metal micrograph of FIG. 2, a thin and linear needle-like pattern phase is observed in the α phase. In the secondary electron image (electron micrograph) of FIG. 3, it is clearly confirmed that the pattern existing in the α phase is the κ phase. The thickness of the κ phase was about 0.1 to about 0.2 μm.
The amount (number) of acicular κ phases in the α phase was judged with a metallographic microscope. A microscopic photograph of five fields of view with a magnification of 500 times or 1000 times taken in the determination of the metal constituent phase (observation of the metal structure) was used. The number of needle-like κ phases was measured in an enlarged field of view printed out to a dimension of about 70 mm in length and about 90 mm in width, and the average value of five fields of view was determined. When the average value of the number of acicular κ phases in 5 fields of view was 20 or more and less than 70, it was clearly determined that the needles had κ phases and was expressed as “Δ”. When the average value of the number of acicular κ phases in five fields of view was 70 or more, it was judged that there were many acicular κ phases, and indicated as “◯”. When the average value of the number of needle-like κ phases in five fields of view was 19 or less, it was judged that the needle-like κ phases were scarcely present, and expressed as “×”. The number of acicular κ1 phases that could not be confirmed in the photograph was not included. In the case of magnification of 500 times, the size of the observation visual field was 276 μm × 220 μm.

(Sn content and P content in κ phase)
The amount of Sn and the amount of P contained in the κ phase were measured with an X-ray microanalyzer. The measurement was performed under the conditions of an acceleration voltage of 20 kV and a current value of 3.0 × 10 ⁻⁸ A using “JXA-8200” manufactured by JEOL.
Test No. T101 (Alloy No. S03 / Process No. AH1), Test No. T103 (Alloy No. S03 / Process No. A1), Test No. For T130 (alloy No. S03 / process No. BH3), the results of quantitative analysis of the Sn, Cu, Si, and P concentrations of each phase with an X-ray microanalyzer are shown in Tables 18-20.
About μ phase, it measured with EDS attached to JSM-7000F, and measured the part where the length of the long side was large in the field of view.

From the above measurement results, the following knowledge was obtained.
1) The concentration allocated to each phase is slightly different depending on the manufacturing method.
2) The distribution of Sn to the κ phase is about 1.3 times that of the α phase.
3) The Sn concentration of the γ phase is about 8 to about 11 times the Sn concentration of the α phase.
4) The Si concentrations of the κ phase, the γ phase, and the μ phase are about 1.5 times, about 2.2 times, and about 2.7 times, respectively, compared with the Si concentration of the α phase.
5) The Cu concentration of the μ phase is higher than that of the α phase, κ phase, γ phase, and μ phase.
6) When the proportion of the γ phase increases, the Sn concentration of the κ phase inevitably decreases.
7) The distribution of P to the κ phase is about twice that of the α phase.
8) The P concentration of the γ phase and μ phase is about 2.5 times and about 3.5 times the P concentration of the α phase.
9) Even with the same composition, when the proportion of the γ phase is decreased, the Sn concentration of the α phase is increased about 0.3 times from 0.34 mass% to 0.44 mass%. Similarly, the Sn concentration of the κ phase increases about 0.4 times from 0.44 mass% to 0.58 mass%. The increase in Sn in the κ phase exceeded the increase in Sn in the α phase (Alloy No. S03).

(Mechanical properties)
(Tensile strength)
Each test material was processed into a JIS Z 2241 No. 10 test piece, and the tensile strength was measured. Tensile strength of the hot extruded material or hot forging, 550 N / mm ² or more, preferably 565N / mm ² or more, 575N / mm ² or more, further if 590N / mm ² or more, free-cutting copper It is the highest level among the alloys, and the allowable stress of members used in each field can be improved, or the thickness and weight can be reduced.
Since the alloy of this embodiment is a copper alloy having a high tensile strength, the finished surface roughness of the tensile test piece affects the elongation and the tensile strength. For this reason, the tensile test piece was produced so that the following conditions might be satisfied.
(Conditions for finished surface roughness of tensile test piece)
The difference between the maximum value and the minimum value of the Z-axis is 2 μm or less in the cross-section curve per 4 mm of the reference length at any place between the marks on the tensile test piece. The cross-sectional curve refers to a curve obtained by applying a reduction filter having a cutoff value λs to the measured cross-sectional curve.
(High temperature creep)
From each test piece, a test piece with a flange having a diameter of 10 mm of JIS Z 2271 was produced. Creep strain after 100 hours at 150 ° C. was measured in a state where a load corresponding to 0.2% proof stress at room temperature was applied to the test piece. Creep strain after 0.2% proof stress, that is, elongation between gauge points at normal temperature, with a load corresponding to 0.2% plastic deformation applied, and holding the test piece at 150 ° C. for 100 hours with this load applied Is 0.4% or less, it is good. If this creep strain is 0.3% or less, further 0.2% or less, it is the highest level for copper alloys. For example, it is reliable for valves used at high temperatures and automotive parts close to the engine room. Can be used as a high material.
(Impact characteristics)
In the impact test, U-notch specimens (notch depth 2 mm, notch bottom radius 1 mm) according to JIS Z 2242 were sampled from extruded rods, forged materials and their substitutes, cast materials, and continuous cast rods. A Charpy impact test was performed with an impact blade having a radius of 2 mm, and the impact value was measured.
In addition, the relationship of the impact value when it performs with a V notch test piece and a U notch test piece is as follows.
(V-notch impact value) = 0.8 × (U-notch impact value) −3

(Machinability)
The machinability was evaluated by a cutting test using a lathe as follows.
About the hot-extrusion rod material of diameter 50mm, 40mm, or 25.6mm, the cold drawing material of diameter 25mm (24.5mm), and casting, the cutting process was given and the test material was produced by making diameter 18mm. For the forged material, cutting was performed to prepare a test material with a diameter of 14.5 mm. Point nose straight tools, especially tungsten carbide tools without chip breakers, were attached to the lathe. Using this lathe, under a dry condition, a rake angle of -6 degrees, a nose radius of 0.4 mm, a cutting speed of 150 m / min, a cutting depth of 1.0 mm, and a feed speed of 0.11 mm / rev, a diameter of 18 mm or a diameter The circumference of a 14.5 mm test material was cut.
A signal emitted from a three-part dynamometer attached to the tool (AST tool dynamometer AST-TL1003, manufactured by Miho Electric Manufacturing Co., Ltd.) was converted into an electrical voltage signal and recorded on a recorder. These signals were then converted into cutting forces (N). Therefore, the machinability of the alloy was evaluated by measuring the cutting force, in particular the main component force showing the highest value during cutting.
At the same time, chips were collected and the machinability was evaluated by the shape of the chips. The most serious problem in practical cutting is that the chips are entangled with the tool or the chips are bulky. For this reason, the case where only a chip having a chip shape of 1 turn or less was evaluated as “good” (good). The case where the chip shape generated chips exceeding 1 roll and up to 3 rolls was evaluated as “Fair”. The case where chips having a chip shape exceeding 3 turns was evaluated as “x” (poor). In this way, a three-stage evaluation was performed.
The cutting resistance depends on the strength of the material, for example, shear stress, tensile strength and 0.2% proof stress, and the higher the strength, the higher the cutting resistance tends to be. If the cutting resistance is about 10% to about 20% higher than the cutting resistance of a free-cutting brass rod containing 1 to 4% of Pb, it is sufficiently acceptable for practical use. In the present embodiment, while keeping the Pb content to a minimum, the κ1 phase is present in the α phase, the concentration of Sn and P in the κ phase is increased, and high machinability is aimed. The cutting resistance was evaluated with 125N as a boundary (boundary value). Specifically, when the cutting resistance was 125 N or less, it was evaluated that the machinability was excellent (evaluation: ◯). When the cutting resistance was more than 125N and not more than 145N, the machinability was evaluated as “possible (Δ)”. If the cutting resistance exceeded 145 N, it was evaluated as “impossible (×)”. Incidentally, for the 58 mass% Cu-42 mass% Zn alloy, the process No. When E1 was applied and a sample was manufactured and evaluated, the cutting resistance was 185N.

(Hot processing test)
A rod having a diameter of 50 mm, a diameter of 40 mm, a diameter of 25.6 mm, or a diameter of 25.0 mm, and a casting were cut to a diameter of 15 mm and cut to a length of 25 mm to prepare a test material. The test material was held at 740 ° C. or 635 ° C. for 20 minutes. Next, the test material was placed vertically, and was hot-compressed at a strain rate of 0.02 / second and a processing rate of 80% using an Amsler tester equipped with an electric furnace with a hot compression capacity of 10 tons. did.
In the evaluation of hot workability, when a crack having an opening of 0.2 mm or more was observed using a magnifying glass having a magnification of 10 times, it was determined that cracking occurred. When no cracks occurred at two conditions of 740 ° C. and 635 ° C., it was evaluated as “◯” (good). A case where cracking occurred at 740 ° C. but no cracking occurred at 635 ° C. was evaluated as “Δ” (fair). The case where cracks did not occur at 740 ° C. but cracks occurred at 635 ° C. was evaluated as “Fair”. The case where cracks occurred at two conditions of 740 ° C. and 635 ° C. was evaluated as “x” (poor).
When cracks did not occur under the two conditions of 740 ° C and 635 ° C, regarding practical hot extrusion and hot forging, even if some material temperature drop occurred, Even if the material is in contact instantaneously and there is a temperature drop of the material, there is no practical problem if it is carried out at an appropriate temperature. If cracking occurs at either 740 ° C. or 635 ° C., it is judged that hot working can be performed, but it is necessary to manage in a narrower temperature range due to practical restrictions. If cracks occur at both temperatures of 740 ° C. and 635 ° C., it is judged that there is a large problem in practical use and is impossible.

(Dezincification corrosion test 1, 2)
When the test material was an extruded material, the test material was embedded in a phenol resin material so that the exposed sample surface of the test material was perpendicular to the extrusion direction. When the test material was a cast material (cast bar), the test material was embedded in the phenol resin material so that the exposed sample surface of the test material was perpendicular to the longitudinal direction of the cast material. When the test material was a forged material, it was embedded in the phenol resin material so that the exposed sample surface of the test material was perpendicular to the flow direction of forging.
The sample surface was polished with emery paper up to 1200, then ultrasonically washed in pure water and dried with a blower. Then, each sample was immersed in the prepared immersion liquid.
At the end of the test, the sample was re-embedded in the phenolic resin material so that the exposed surface remained perpendicular to the extrusion direction, longitudinal direction, or forging flow direction. Next, the sample was cut so that the cross section of the corroded portion was obtained as the longest cut portion. Subsequently, the sample was polished.
Using a metal microscope, the corrosion depth was observed at 10 magnifications (arbitrary 10 visual fields) at a magnification of 500 times. The deepest corrosion point was recorded as the maximum dezincification corrosion depth.

In the dezincification corrosion test 1, the following test liquid 1 was prepared as an immersion liquid and the above operation was performed. In the dezincification corrosion test 2, the following test liquid 2 was prepared as the immersion liquid and the above operation was performed.
The test solution 1 is a solution that is administered with an excessive amount of a disinfectant as an oxidizing agent, assumes a severe corrosive environment with a low pH, and further performs an accelerated test in the corrosive environment. When this solution is used, it is estimated that the acceleration test is about 75 to 100 times in the severe corrosive environment. In the present embodiment, in order to aim for excellent corrosion resistance in a severe environment, the corrosion resistance is good when the maximum corrosion depth is 80 μm or less. When excellent corrosion resistance is required, it is estimated that the maximum corrosion depth is preferably 60 μm or less, and more preferably 40 μm or less.
The test solution 2 is a solution for performing an accelerated test in a corrosive environment, assuming high chloride ion concentration, low pH, and water quality in a severe corrosive environment. When this solution is used, it is estimated that the acceleration test is about 30 to 50 times in the severe corrosive environment. If the maximum corrosion depth is 50 μm or less, the corrosion resistance is good. When excellent corrosion resistance is required, it is estimated that the maximum corrosion depth is preferably 35 μm or less, more preferably 25 μm or less. In the present Example, it evaluated based on these estimated values.

  In the dezincification corrosion test 1, hypochlorous acid water (concentration 30 ppm, pH = 6.8, water temperature 40 ° C.) was used as the test solution 1. Test solution 1 was prepared by the following method. Commercially available sodium hypochlorite (NaClO) was added to 40 L of distilled water, and the residual chlorine concentration by the iodine titration method was adjusted to 30 mg / L. Since residual chlorine decomposes and decreases with time, the sodium hypochlorite input was electronically controlled by an electromagnetic pump while constantly measuring the residual chlorine concentration by the voltammetric method. Carbon dioxide was added while adjusting the flow rate in order to lower the pH to 6.8. The water temperature was adjusted with a temperature controller to 40 ° C. Thus, the sample was kept in the test solution 1 for 2 months while keeping the residual chlorine concentration, pH, and water temperature constant. Next, a sample was taken out from the aqueous solution, and the maximum value of the dezincification corrosion depth (maximum dezincification corrosion depth) was measured.

  In the dezincification corrosion test 2, test water having the components shown in Table 21 was used as the test solution 2. Test solution 2 was prepared by adding a commercially available drug to distilled water. Assuming highly corrosive tap water, chloride ions 80 mg / L, sulfate ions 40 mg / L, and nitrate ions 30 mg / L were added. The alkalinity and hardness were adjusted to 30 mg / L and 60 mg / L, respectively, using Japanese general tap water as a guide. Carbon dioxide was added while adjusting the flow rate to lower the pH to 6.3, and oxygen gas was constantly added to saturate the dissolved oxygen concentration. The water temperature was 25 ° C., the same as room temperature. In this way, the sample was held in the test solution 2 for 3 months while keeping the pH and water temperature constant and the dissolved oxygen concentration saturated. Next, a sample was taken out from the aqueous solution, and the maximum value of the dezincification corrosion depth (maximum dezincification corrosion depth) was measured.

(Dezincification corrosion test 3: ISO6509 dezincification corrosion test)
This test is adopted as a dezincification corrosion test method in many countries, and is defined by JIS H 3250 in the JIS standard.
Similar to the dezincification corrosion tests 1 and 2, the test material was embedded in the phenol resin material. For example, it was embedded in the phenol resin material so that the exposed sample surface was perpendicular to the extrusion direction of the extruded material. The sample surface was polished with emery paper up to 1200, and then ultrasonically washed in pure water and dried.
Next, each sample was immersed in an aqueous solution (12.7 g / L) of 1.0% cupric chloride dihydrate (CuCl ₂ .2H ₂ O), and the temperature was adjusted to 75 ° C. for 24 hours. Retained. Thereafter, a sample was taken out from the aqueous solution.
The sample was re-embedded in the phenolic resin material so that the exposed surface remained perpendicular to the extrusion direction, the longitudinal direction, or the forging flow direction. Next, the sample was cut so that the cross section of the corroded portion was obtained as the longest cut portion. Subsequently, the sample was polished.
Using a metal microscope, corrosion depth was observed at 10 magnifications of 200 or 500 magnifications at 10 fields of view of the microscope. The deepest corrosion point was recorded as the maximum dezincification corrosion depth.
In addition, when the test of ISO 6509 is performed, if the maximum corrosion depth is 200 μm or less, the practical corrosion resistance is regarded as a problem-free level. When particularly excellent corrosion resistance is required, the maximum corrosion depth is preferably 100 μm or less, and more preferably 50 μm or less.
In this test, when the maximum corrosion depth exceeded 200 μm, it was evaluated as “x” (poor). The case where the maximum corrosion depth exceeded 50 μm and was 200 μm or less was evaluated as “Δ” (fair). The case where the maximum corrosion depth was 50 μm or less was strictly evaluated as “◯” (good). Since this embodiment assumes a severe corrosive environment, a strict evaluation standard is adopted, and only when the evaluation is “◯”, the corrosion resistance is good.

(Cavitation resistance)
Cavitation is a phenomenon in which bubbles are generated and disappeared in a short time due to a pressure difference in a liquid flow. Cavitation resistance means the difficulty of being damaged by the generation and disappearance of bubbles.
Cavitation resistance was evaluated by direct magnetostrictive vibration test. The sample diameter was 16 mm by cutting, and then the exposed test surface was polished with # 1200 water-resistant abrasive paper to prepare a sample. The sample was attached to the horn at the tip of the vibrator. The sample was ultrasonically vibrated in the test solution under the conditions of vibration frequency: 18 kHz, amplitude: 40 μm, test time: 2 hours. Ion exchange water was used as a test solution for immersing the sample surface. The beaker containing the ion exchange water was cooled, and the water temperature was adjusted to 20 ° C. ± 2 ° C. (18 ° C. to 22 ° C.). The weight of the sample before and after the test was measured, and the cavitation resistance was evaluated by the difference in weight. When the weight difference (amount of decrease in weight) exceeded 0.03 g, it was judged that the surface was damaged and the cavitation resistance was poor, so that it was impossible. When the weight difference (weight reduction amount) is more than 0.005 g and 0.03 g or less, the surface damage is slight and the cavitation resistance is considered to be good. However, since this embodiment aims at excellent cavitation resistance, it was determined to be impossible. When the difference in weight (amount of decrease in weight) was 0.005 g or less, it was judged that there was almost no damage to the surface and the cavitation resistance was excellent. When the weight difference (weight reduction) is 0.003 g or less, it can be determined that the cavitation resistance is particularly excellent.
Incidentally, as a result of testing free-cutting brass containing 59Cu-3Pb-38Zn Pb under the same test conditions, the weight loss was 0.10 g.

(Erosion corrosion resistance)
Erosion-corrosion is a phenomenon in which corrosion rapidly proceeds locally by combining a chemical corrosion phenomenon caused by a fluid and a physical scraping phenomenon. The erosion-corrosion resistance means the difficulty of receiving this corrosion.
The sample surface was made into a flat perfect circle shape with a diameter of 20 mm, and then the surface was polished with # 2000 emery paper to prepare a sample. Test water was applied to the sample at a flow rate of about 9 m / sec (Test Method 1) or about 7 m / sec (Test Method 2) using a 1.6 mm nozzle. Specifically, water was applied to the center of the sample surface from the direction perpendicular to the sample surface. The distance between the nozzle tip and the center of the sample surface was 0.4 mm. Under these conditions, the corrosion weight loss after applying test water to the sample for 336 hours was measured.
As test water, hypochlorous acid water (concentration 30 ppm, pH = 7.0, water temperature 40 ° C.) was used. Test water was prepared by the following method. Commercially available sodium hypochlorite (NaClO) was added to 40 L of distilled water. The amount of sodium hypochlorite was adjusted so that the residual chlorine concentration by the iodine titration method was 30 mg / L. Residual chlorine decomposes and decreases over time. Therefore, the amount of sodium hypochlorite input was electronically controlled by an electromagnetic pump while constantly measuring the residual chlorine concentration by the voltammetry method. Carbon dioxide was added while adjusting the flow rate in order to lower the pH to 7.0. The water temperature was adjusted with a temperature controller to 40 ° C. Thus, the residual chlorine concentration, pH, and water temperature were kept constant.
In Test Method 1, when the corrosion weight loss exceeded 75 mg, it was evaluated that the erosion corrosion resistance was poor. When the corrosion weight loss exceeded 50 mg and was 75 mg or less, it was evaluated that the erosion corrosion resistance was good. When the corrosion weight loss exceeded 30 mg and was 50 mg or less, it was evaluated that the erosion corrosion resistance was excellent. When the corrosion weight loss was 30 mg or less, it was evaluated that the erosion corrosion resistance was particularly excellent.
Similarly, in Test Method 2, when the corrosion weight loss exceeded 60 mg, it was evaluated that the erosion corrosion resistance was poor. When the corrosion weight loss exceeded 40 mg and was 60 mg or less, it was evaluated that the erosion corrosion resistance was good. When the corrosion weight loss exceeded 25 mg and was 40 mg or less, it was evaluated that the erosion corrosion resistance was excellent. When the corrosion weight loss was 25 mg or less, it was evaluated that the erosion corrosion resistance was particularly excellent.

The evaluation results are shown in Tables 22 to 69.
Test No. T01 to T164 are the results of experiments in actual operation. Test No. T201 to T258 are results corresponding to an example in a laboratory experiment. Test No. T301 to T329 are results corresponding to a comparative example in a laboratory experiment.
Regarding the length of the long side of the μ phase in the table, the value “40” means 40 μm or more. In addition, regarding the length of the long side of the γ phase in the table, the value “150” means 150 μm or more.

The above experimental results are summarized as follows.
1) Satisfying the composition of the present embodiment and satisfying the compositional relational expressions f1, f2, and f3, the requirements of the metal structure, and the structural relational expressions f4 to f7, so that good machinability is achieved with a small amount of Pb. Good hot workability, excellent corrosion resistance in harsh environments (hereinafter referred to as corrosion resistance), cavitation resistance, erosion corrosion resistance, high strength, good impact properties, high temperature properties, high It was confirmed that hot extruded materials and hot forged materials having a balance index can be obtained (Alloy Nos. S01, S02, S03, S21 to S35).
2) It has been confirmed that the inclusion of Sb and As improves the corrosion resistance under more severe conditions (Alloy Nos. S41 to S43).
3) It was confirmed that the cutting resistance was further reduced by the inclusion of Bi (Alloy Nos. S42 to S43).

4) When the Cu content was small, the machinability was good, but the corrosion resistance, cavitation resistance, erosion corrosion resistance, impact characteristics, ductility, and high temperature characteristics were poor. When the Cu content was large, machinability, hot workability, ductility, and impact properties were poor (Alloy Nos. S52, S55, and S65).
5) When the Si content was large, machinability, elongation, impact characteristics, and strength balance index were poor. When the Si content was low, machinability, cavitation resistance and erosion corrosion resistance were poor, and the strength was low (Alloy Nos. S53 and S56).
6) When the Sn content was more than 0.85 mass%, the area ratio of the γ phase was more than 2% and the cavitation resistance and erosion corrosion resistance were good, but the elongation, impact properties, and strength balance index were bad. . On the other hand, when the Sn content was less than 0.40 mass%, cavitation resistance and erosion corrosion resistance were poor (Alloy Nos. S59, S58, and S64).
7) When the P content was large, the ductility and impact properties were poor, and the corrosion resistance, cavitation resistance and erosion corrosion resistance were poor. On the other hand, when the P content is low or P is not included, the dezincing corrosion depth in a severe environment is large, and the cavitation resistance, erosion corrosion resistance, and machinability are deteriorated (alloys). No. S60, S63, S64).
8) It has been confirmed that the inclusion of inevitable impurities to the extent that is performed in actual operation does not significantly affect various properties (Alloy Nos. S01, S02, S03).
9) Alloy No. When Fe is further added to S01, the proportion of the κ phase is decreased, and the machinability and tensile strength are reduced. When the amount of Fe is further increased, the machinability and tensile strength are reduced and the corrosion resistance is increased. The erosion-corrosion resistance deteriorated, and the elongation, impact value, and strength balance index slightly decreased. However, machinability, corrosion resistance, and erosion corrosion resistance were within acceptable ranges (alloys Nos. S01, S11, and S12). If it is outside the composition range of the present embodiment but contains Fe exceeding the limit of inevitable impurities, it is presumed that an intermetallic compound of Fe and Si was mainly formed, and it is considered that the above-mentioned characteristics were lowered.
10) Alloy No. When Pb was further added to S02, machinability was improved, but other properties such as other tensile strength, elongation, impact value, high temperature characteristics, cavitation resistance, strength balance index, etc. were slightly deteriorated. When the amount was increased, the above-mentioned characteristics were worsened (Alloy Nos. S02, S13, S14). If machinability can be satisfied, the Pb content should be kept to a minimum. Note that when the Pb content was 0.002 mass%, the cutting resistance was increased, and the cutting chips were poorly divided (alloy No. S71).

11) Even if the composition of each element is satisfied, if the value of the composition relational expression f1 is 75.0 or more and 78.2 or less, preferably 75.5 or more, or 77.7 or less, Sn is 0. Even if contained in 40 to 0.85%, a copper alloy having a γ phase ratio of 2% or less is obtained, and machinability, corrosion resistance, strength, impact characteristics, high temperature characteristics, cavitation resistance, and erosion corrosion resistance are good. (Alloy Nos. S01 to S03, S21 to S35, Process No. E1, F1, etc.).
12) When the composition of each element was satisfied and the value of the compositional relational expression f2 was low, the γ phase increased or the long side of the γ phase became longer. The machinability was good, but some of them had a β phase, and hot workability, corrosion resistance, elongation, impact properties, high temperature properties, cavitation resistance, erosion corrosion resistance were poor, and strength was low. . When the value of the compositional relational expression f2 is high, the κ1 phase becomes difficult to exist, the hot workability and the machinability deteriorate, and the strength also decreases (alloys Nos. S52 to S54, S66 to S68).
13) Even if f1 is satisfied, f2 may not be satisfied, or even if f2 is satisfied, f1 may not be satisfied, and in these cases, characteristics that do not satisfy are given priority (alloy Nos. S54, S58, S66 to S68). Therefore, it is essential to satisfy both relational expressions f1 and f2.
Even if the amount of Sn and P is appropriate, if the relational expression f3 is not satisfied, the corrosion resistance and cavitation resistance are deteriorated, and the erosion and corrosion resistance is deteriorated as compared with the Sn content. All the properties of strength, high temperature properties and machinability were affected (Alloy Nos. S61 and S64).

14) In the metal structure, when the area ratio of the γ phase is more than 2% or the long side of the γ phase is longer than 50 μm, the machinability was good, but the corrosion resistance, cavitation resistance, The erosion-corrosion resistance, impact properties, high-temperature properties, tensile strength, and strength balance index were poor. In particular, when the γ phase is large, selective corrosion of the γ phase occurred in a dezincification corrosion test under a harsh environment (alloy No. S01, process No. AH1, AH2, AH6, C0, DH1, DH5, EH1, FH1). , Alloy No. S51, etc.). When the γ phase ratio is 1.5% or less, further 0.8% or less, and the length of the long side of the γ phase is 40 μm or less, and further 30 μm or less, the corrosion resistance, cavitation resistance, The erosion corrosion property, impact property, high temperature property, tensile strength and strength balance index were further improved (alloy Nos. S01 to S03, S21 to S35, step Nos. E1 and F1).
15) When the area ratio of the μ phase was more than 2%, the corrosion resistance, cavitation resistance, erosion corrosion resistance, impact characteristics, high temperature characteristics, and strength balance index deteriorated. In the dezincification corrosion test under harsh environment, intergranular corrosion and μ phase selective corrosion occurred (Alloy No. S01, Process No. AH4, AH8, BH3). When the μ phase ratio is 1.0% or less, further 0.5% or less, and the length of the long side of the μ phase is 15 μm or less, further 5 μm or less, the corrosion resistance, high temperature characteristics, tensile strength The strength balance index was further improved (alloy Nos. S01 to S03, step Nos. A3, A4, AH3, B1, B3, D2, D3, DH2, FH2).
When the area ratio of the β phase was more than 0.3%, the corrosion resistance, cavitation resistance, erosion corrosion resistance, elongation, impact characteristics, and high temperature characteristics were poor (Alloy Nos. S52 and S67).
When the area ratio of the κ phase was more than 65%, the machinability, elongation and impact properties were poor. On the other hand, when the area ratio of the κ phase was less than 30%, the machinability, cavitation resistance, and erosion corrosion resistance were poor (Alloy Nos. S56 and S53).
When the κ phase is present in the α phase and the presence of the κ1 phase is increased, the corrosion resistance, strength, elongation, strength balance index, impact properties, cavitation resistance, erosion corrosion resistance, and high temperature properties are improved. Good machinability could be maintained even if the decrease was reduced. The κ1 phase is presumed to lead to strengthening of the α phase, reduction of cutting resistance, and chip breaking (alloy Nos. S01 to 03, process Nos. AH1, AH2, A1, and A6). The relational expression f2 has an influence on the amount of acicular κ phase (alloy Nos. S54, S66, S68, S24, S30, etc.).

16) When the structure relational expression f6 = (γ) + (μ) exceeds 3%, or when f4 = (α) + (κ) is less than 96.5%, the corrosion resistance, impact characteristics, and high temperature characteristics were poor. (Alloy No. S52).
When the structural relational expression f7 = 1.05 (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) was smaller than 35 or larger than 70, the machinability was poor (alloy No. S56). , S53, S54).

17) When the amount of Sn contained in the κ phase is lower than 0.43 mass%, cavitation resistance and erosion corrosion resistance deteriorated. Even if the Sn content of the alloy is the same, the Sn concentration in the κ phase varies greatly depending on the proportion of the γ phase, and a large difference occurs in the weight loss (erosion corrosion resistance) of the erosion corrosion test. The erosion-corrosion resistance is affected by the presence or absence of needle-like κ phase in the f1, f2, f3 and α phases, but depends on the corrosion resistance and the Sn concentration in the κ phase. About 0.45% seems to be a critical amount of Sn (Alloy No. S01, Process No. AH1, A1, and Alloy No. S33, Process No. FH1, F1).
When the κ phase ratio was almost the same, the cutting resistance was high when the Sn concentration of the κ phase was low (alloy Nos. S29, S32, S59, etc.).
18) Creep strain when tensile strength is 550 N / mm ² or more, 0.2% proof stress at room temperature is applied and held at 150 ° C. for 100 hours if all the requirements for composition and metal structure are satisfied However, most were good at 0.3% or less (alloy Nos. S01, S02, S03, etc.).
19) The Charpy impact test value was 12 J / cm ² or more if all the requirements for the composition and the requirements for the metal structure were satisfied. Further, the hot extrusion and hot forging materials had Charpy impact test values of 14 J / cm ² or more (alloy Nos. S01, S21 to S35, process Nos. E1, F1, etc.).
If all the requirements of the composition and the requirements of the metal structure were satisfied, the strength balance index f8 was 650 or more and f9 was 665 or more (Alloy No. S01).
In the ISO 6509 test method, an alloy containing about 0.5% or more of the β phase or about 5% or more of the γ phase was rejected (evaluation: Δ, x), but contained 3 to 5% of the γ phase. The alloy containing about 3% of the μ phase was acceptable (evaluation: ◯). The corrosive environment employed in the present embodiment is a proof that a severe environment is assumed (alloy Nos. S01, S02, S03, S52, S67).

20) In the evaluation of the material using the mass production equipment and the material prepared in the laboratory, almost the same result was obtained (alloy No. S01, S02, process No. F1, E1, C1, D1).
21) With respect to the manufacturing conditions, if any one of the following conditions (1) to (3) is satisfied, it has corrosion resistance, cavitation resistance, erosion corrosion resistance, and has good strength, ductility, strength balance index, impact characteristics, It was confirmed that a hot-extruded material and a hot-forged material that have high temperature characteristics can be obtained. Even if a continuous casting rod was used as the forging material, a forged product having good characteristics was obtained. Castings having corrosion resistance, cavitation resistance and erosion corrosion resistance were also confirmed (alloy No. S01, process Nos. A1 to A9, D1 to D7, F1 to F5, P1 to P3).
(1) Hot working was performed at a hot working temperature of 600 ° C. or higher and 740 ° C. or lower. Next, the hot-worked material was heat-treated at 525 ° C. to 575 ° C. for 20 minutes or more and 480 minutes or less, or at 515 ° C. or more and 525 ° C. for 100 minutes or more and 480 minutes or less. Subsequently, the temperature range from 460 ° C. to 400 ° C. was cooled at a cooling rate of 2.5 ° C./min to 500 ° C./min.
(2) Heat treatment was performed at a maximum temperature not exceeding 610 ° C. Subsequently, the temperature range from 575 ° C. to 525 ° C. was cooled at a cooling rate of 2.5 ° C./min or less. Subsequently, the temperature range from 460 ° C. to 400 ° C. was cooled at a cooling rate of 2.5 ° C./min to 500 ° C./min.
(3) In the cooling after forging, the temperature range from 575 ° C. to 525 ° C. was cooled at a cooling rate of 2.5 ° C./min or less. Subsequently, the temperature range from 460 ° C. to 400 ° C. was cooled at a cooling rate of 2.5 ° C./min to 500 ° C./min.

22) The amount of Sn and the amount of P contained in the κ phase increased by appropriate heat treatment and appropriate cooling conditions after hot forging (alloy Nos. S01, S02, S03, process Nos. A1, AH1, C0). , C1, D6).
23) When a cold process with a processing rate of 4 to 10% is included in the process (heat treatment after cold drawing, cold drawing after heat treatment), compared to the original extrudate and those not including cold work, The tensile strength was improved by 50 N / mm ² or more, and the strength balance index was greatly improved. After cold working, when heat treated at 525 ° C. to 575 ° C., both tensile strength and impact properties were improved compared to the hot extruded material (Alloy No. S01, Step No. AH1, AH2, A1, A10-12). .
When heat-treated and cold-worked materials are subjected to appropriate heat treatment, acicular κ phase is present in α phase, the amount of Sn contained in κ phase is increased, and γ phase is greatly increased. However, it was confirmed that good machinability could be secured and the tensile strength, elongation, impact properties, high temperature properties, corrosion resistance, cavitation resistance, erosion corrosion resistance were greatly improved (Alloy No. S01 to S03, step Nos. AH1, A1, D7, C0, C1, EH1, E1, FH1, F1).
In the process of heat-treating hot-worked material and cold-worked material, if the heat treatment temperature is low (505 ° C), or if the holding time is short by heat treatment at 515 ° C or more and less than 525 ° C, the decrease in γ phase is small. The amount of κ1 phase was small, and the corrosion resistance, cavitation resistance, erosion corrosion resistance, impact characteristics, ductility, high temperature characteristics, and strength balance index were poor (Process Nos. AH6, AH9, DH7). When the temperature of the heat treatment was high, the α-phase crystal grains became coarse, the κ1 phase was small, and the γ-phase decrease was small. For this reason, corrosion resistance, cavitation resistance, erosion corrosion resistance and machinability were poor, tensile strength was low, and f8 and f9 were also low (Step Nos. AH5, AH10 and DH6).
When performing low temperature annealing after cold working or after hot working, heat at a temperature of 240 ° C. or higher and 350 ° C. or lower for 10 to 300 minutes, when the heating temperature is T ° C. and the heating time is t minutes, Cold-worked material with excellent impact resistance and high-temperature characteristics, heat resistance, excellent heat resistance under harsh environments when heat-treated under conditions of 150 ≦ (T−220) × (t) ^1/2 ≦ 1200, heat It was confirmed that an inter-processed material was obtained (Alloy No. S01, Process Nos. B1 to B3).
Alloy No. For the steps S01 to S03, the process No. In the sample to which AH11 was applied, since the deformation resistance was high, it was not possible to extrude to the end, so the subsequent evaluation was stopped.
Step No. In BH1, correction was insufficient and low-temperature annealing was unsuitable, resulting in quality problems.

  From the above, like the alloy of this embodiment, the content of each additive element and each composition relational expression, the metal structure, and the alloy of this embodiment in the proper range of each structure relation are hot workability Excellent (hot extrusion, hot forging), good corrosion resistance and machinability. Moreover, in order to acquire the outstanding characteristic in the alloy of this embodiment, it can achieve by making the manufacturing conditions in hot extrusion and hot forging, and the conditions in heat processing into an appropriate range.

(Example 2)
Regarding the alloy which is a comparative example of this embodiment, a copper alloy Cu—Zn—Si alloy casting (test No. T401 / alloy No. S101) used in a severe water environment for 8 years was obtained. There is no detailed information about the water quality of the environment used. In the same manner as in Example 1, test no. The composition of T401 and the metal structure were analyzed. Moreover, the corrosion state of the cross section was observed using a metal microscope. Specifically, the sample was embedded in a phenolic resin material so that the exposed surface was kept perpendicular to the longitudinal direction. Next, the sample was cut so that the cross section of the corroded portion was obtained as the longest cut portion. Subsequently, the sample was polished. The cross section was observed using a metal microscope. The maximum corrosion depth was measured.
Next, test no. A similar alloy casting was produced under the same composition and production conditions as T401 (test No. T402 / alloy No. S102). For similar alloy castings (Test No. T402), the composition described in Example 1, evaluation (measurement) such as analysis of metal structure, and dezincification corrosion tests 1 to 3 were performed. And test no. Corrosion state by actual water environment of T401 and test No. The validity of the accelerated test of the dezincification corrosion test 1 to 3 was verified by comparing the corrosion state by the accelerated test of the dezincification corrosion test 1 to 3 of T402.
Further, the evaluation result (corrosion state) of the dezincification corrosion test 1 of the alloy of the present embodiment described in Example 1 (Test No. T63 / Alloy No. S02 / Process No. C1) and Test No. Corrosion state of T401 and test No. Comparison with the evaluation result (corrosion state) of the dezincification corrosion test 1 of T402, The corrosion resistance of T63 was considered.

Test No. T402 was produced by the following method.
Test No. The raw material was melted so as to have almost the same composition as T401 (alloy No. S101), and cast into a mold having an inner diameter of 40 mm at a casting temperature of 1000 ° C. to produce a casting. Thereafter, the casting was cooled in a temperature range of 575 ° C. to 525 ° C. at a cooling rate of about 20 ° C./min, and then in a temperature range of 460 ° C. to 400 ° C. at a cooling rate of about 15 ° C./min. As described above, test no. A sample of T402 was prepared.
The composition, the analysis method of the metal structure, the measurement method of the mechanical properties, and the methods of the dezincification corrosion tests 1 to 3 are as described in Example 1.
The obtained results are shown in Tables 70 to 73 and FIGS.

In a copper alloy casting (test No. T401) used in a severe water environment for 8 years, at least the contents of Sn and P are outside the scope of the present embodiment.
FIG. The metal micrograph of the cross section of T401 is shown.
Test No. T401 was used in a severe water environment for 8 years, but the maximum corrosion depth of the corrosion caused by this use environment was 138 μm.
On the surface of the corroded portion, dezincification corrosion occurred regardless of the α phase and the κ phase (an average depth of about 100 μm from the surface).
Among the corroded portions where the α phase and κ phase are corroded, the sound α phase was present toward the inside.
The corrosion depths of the α and κ phases are not constant, but have irregularities, but the corrosion occurs preferentially in the γ phase from the boundary to the inside (the α and κ phases are corroded). Depth of about 40 μm from the boundary part to the inside: preferential corrosion of the γ phase occurring locally).

FIG. The metal micrograph of the cross section after the dezincification corrosion test 1 of T402 is shown.
The maximum corrosion depth was 153 μm.
On the surface of the corroded portion, dezincification corrosion occurred regardless of the α phase and the κ phase (an average depth of about 100 μm from the surface).
Among them, a healthy α phase was present toward the inside.
The corrosion depths of the α and κ phases are not constant, but have irregularities, but the corrosion occurs preferentially in the γ phase from the boundary to the inside (the α and κ phases are corroded). The preferential corrosion length of the locally occurring γ phase was about 45 μm.

It was found that the corrosion caused by the severe water environment for 8 years in FIG. 4 and the corrosion caused by the dezincification corrosion test 1 in FIG. In addition, since the amounts of Sn and P do not satisfy the range of the present embodiment, both the α phase and the κ phase corrode at the portion in contact with water and the test solution, and the γ phase is generated at various points at the tip of the corroded portion. It was selectively corroded. The concentrations of Sn and P in the κ phase were low.
Test No. The maximum corrosion depth of T401 is the test No. It was slightly shallower than the maximum corrosion depth in the dezincification corrosion test 1 of T402. However, test no. The maximum corrosion depth of T401 is the test No. It was slightly deeper than the maximum corrosion depth in the dezincification corrosion test 2 of T402. Although the degree of corrosion by the actual water environment is affected by the water quality, the results of the dezincification corrosion tests 1 and 2 and the corrosion result by the actual water environment were almost the same in both the corrosion form and the corrosion depth. Therefore, it was found that the conditions of the dezincification corrosion tests 1 and 2 are appropriate, and the dezincification corrosion tests 1 and 2 can obtain almost the same evaluation results as the corrosion results in the actual water environment.
In addition, the acceleration rate of the accelerated test of the corrosion test methods 1 and 2 is almost the same as the corrosion in the actual severe water environment, which means that the corrosion test methods 1 and 2 are assumed to be a severe environment. It seems to be supporting.
Test No. The result of T402 dezincification corrosion test 3 (ISO6509 dezincification corrosion test) was “◯” (good). For this reason, the result of the dezincification corrosion test 3 did not correspond with the corrosion result by the actual water environment.
The test time of the dezincification corrosion test 1 is 2 months, and is an accelerated test of about 75 to 100 times. The test time of the dezincification corrosion test 2 is 3 months, which is an accelerated test of about 30 to 50 times. On the other hand, the test time of the dezincification corrosion test 3 (ISO 6509 dezincification corrosion test) is 24 hours, which is an acceleration test of about 1000 times or more.
Like the dezincification corrosion test 1 and 2, by using a test solution that is closer to the actual water environment and performing the test for a long period of 2 to 3 months, the evaluation is almost equivalent to the corrosion result of the actual water environment. It is thought that the result was obtained.
In particular, test no. Corrosion result due to severe water environment for 8 years of T401, Test No. In the corrosion results of the dezincification corrosion test 1 and 2 of T402, the γ phase was corroded along with the corrosion of the surface α phase and κ phase. However, in the corrosion result of the dezincification corrosion test 3 (ISO 6509 dezincification corrosion test), the γ phase was hardly corroded. For this reason, in the dezincification corrosion test 3 (ISO 6509 dezincification corrosion test), the corrosion of the surface α phase and κ phase as well as the corrosion of the γ phase could not be evaluated properly, and it did not agree with the actual corrosion result of the water environment. Conceivable.

FIG. The metal micrograph of the cross section after the dezincification corrosion test 1 of T63 (alloy No. S02 / process No. A1) is shown.
Near the surface, only the γ phase exposed on the surface was corroded. The α phase and κ phase were healthy (not corroded). Test No. In T63, the length of the long side of the γ phase is considered to be one of the major factors determining the corrosion depth together with the amount of the γ phase.
Test No. 1 in FIGS. Compared to T401 and T402, the test No. of this embodiment in FIG. It can be seen that at T63, the corrosion of the α-phase and κ-phase near the surface is completely absent or significantly suppressed. This is considered to be due to the fact that the Sn content in the κ phase reached 0.68% and the corrosion resistance of the κ phase was increased from the observation result of the corrosion form.

The free-cutting copper alloy of the present invention is excellent in hot workability (hot extrudability and hot forgeability), and excellent in corrosion resistance and machinability. For this reason, the free-cutting copper alloy of the present invention is used for electric, automobile, mechanical, and industrial piping such as faucets, valves, fittings, etc. Suitable for members, instruments and parts that come into contact with liquids.
Specifically, drinking water, drainage, industrial water flows, faucet fittings, mixed faucet fittings, drainage fittings, faucet bodies, water heater parts, eco-cute parts, hose fittings, sprinklers, water meters, stopcocks, Fire hydrant, hose nipple, water supply / drain cock, pump, header, pressure reducing valve, valve seat, gate valve, valve rod, union, flange, branch plug, faucet valve, ball valve, various valves, piping joints such as elbow, socket, cheese It can be suitably applied as a constituent material or the like used for names such as bends, connectors, adapters, tees, and joints.
Also used as automotive parts, solenoid valves, control valves, various valves, radiator parts, oil cooler parts, cylinders, machine parts, piping joints, valves, valve rods, heat exchanger parts, water supply / drain cocks, cylinders, pumps As an industrial piping member, it can be suitably applied to piping joints, valves, valve rods and the like.

In order to solve such problems and achieve the above object, the free-cutting copper alloy according to the first aspect of the present invention comprises 76.0 mass% or more and 78.7 mass% or less of Cu, and 3.1 mass. % To 3.6 mass% Si, 0.40 mass% to 0.85 mass% Sn, 0.05 mass% to 0.14 mass% P, and 0.005 mass% to less than 0.020 mass%. Pb, and the balance consists of Zn and inevitable impurities,
The total amount of the inevitable impurities Fe, Mn, Co, and Cr is less than 0.08 mass%,
The Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, the P content is [P] mass%, and the Pb content is [ Pb] mass%,
75.0 ≦ f1 = [Cu] + 0.8 × [Si] −7.5 × [Sn] + [P] + 0.5 × [Pb] ≦ 78.2
60.0 ≦ f2 = [Cu] −4.8 × [Si] −0.8 × [Sn] − [P] + 0.5 × [Pb] ≦ 61.5,
0.09 ≦ f3 = [P] / [Sn] ≦ 0.30,
And having a relationship
In the constituent phase of the metal structure, the α phase area ratio is (α)%, the β phase area ratio is (β)%, the γ phase area ratio is (γ)%, and the κ phase area ratio is (κ)%. When the area ratio of the μ phase is (μ)%,
30 ≦ (κ) ≦ 65,
0 ≦ (γ) ≦ 2.0,
0 ≦ (β) ≦ 0.3,
0 ≦ (μ) ≦ 2.0,
96.5 ≦ f4 = (α) + (κ),
99.4 ≦ f5 = (α) + (κ) + (γ) + (μ),
0 ≦ f6 = (γ) + (μ) ≦ 3.0,
35 ≦ f7 = 1.05 × (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 70,
And having a relationship
A needle-like κ phase is present in the α phase, the long side length of the γ phase is 40 μm or less , and the long side length of the μ phase is 15 μm or less .

The free-cutting copper alloy according to the third aspect of the invention is composed of 76.5 mass% to 78.3 mass% Cu, 3.15 mass% to 3.5 mass% Si, and 0.45 mass% to 0.77 mass. % Sn, 0.06 mass% or more and 0.13 mass% or less P, and 0.006 mass% or more and 0.018 mass% or less Pb, with the balance consisting of Zn and inevitable impurities,
The total amount of the inevitable impurities Fe, Mn, Co, and Cr is less than 0.08 mass%,
The Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, the P content is [P] mass%, and the Pb content is [ Pb] mass%,
75.5 ≦ f1 = [Cu] + 0.8 × [Si] −7.5 × [Sn] + [P] + 0.5 × [Pb] ≦ 77.7,
60.2 ≦ f2 = [Cu] −4.8 × [Si] −0.8 × [Sn] − [P] + 0.5 × [Pb] ≦ 61.3,
0.10 ≦ f3 = [P] / [Sn] ≦ 0.27
And having a relationship
In the constituent phase of the metal structure, the α phase area ratio is (α)%, the β phase area ratio is (β)%, the γ phase area ratio is (γ)%, and the κ phase area ratio is (κ)%. When the area ratio of the μ phase is (μ)%,
33 ≦ (κ) ≦ 60,
0 ≦ (γ) ≦ 1.5,
0 ≦ (β) ≦ 0.1,
0 ≦ (μ) ≦ 1.0,
97.5 ≦ f4 = (α) + (κ),
99.6 ≦ f5 = (α) + (κ) + (γ) + (μ),
0 ≦ f6 = (γ) + (μ) ≦ 2.0,
38 ≦ f7 = 1.05 × (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 65,
And having a relationship
A needle-like κ phase is present in the α phase, the long side length of the γ phase is 40 μm or less, and the long side length of the μ phase is 15 μm or less.

The free-cutting copper alloy according to the fourth aspect of the present invention is the free-cutting copper alloy according to any one of the first to third aspects of the present invention , wherein the amount of Sn contained in the κ phase is 0.43 mass%. It is 0.90 mass% or less and the amount of P contained in the κ phase is 0.06 mass% or more and 0.22 mass% or less.

The free-cutting copper alloy according to the fifth aspect of the present invention is the free-cutting copper alloy according to any one of the first to fourth aspects of the present invention, wherein the U-notch-shaped Charpy impact test value is 12 J / cm ² or more. The creep strain after holding at 150 ° C. for 100 hours with a load corresponding to 0.2% proof stress at room temperature being 45 J / cm ² or less is 0.4% or less. To do.
The Charpy impact test value is a value for a U-notch test piece.

The free-cutting copper alloy according to the sixth aspect of the present invention is a hot-working material in the free-cutting copper alloy according to any of the first to fourth aspects of the present invention, and has a tensile strength S (N / mm ² ) is 550 N / mm ² or more, elongation E (%) is 12% or more, U-notch-shaped Charpy impact test value I (J / cm ² ) is 12 J / cm ² or more and 45 J / cm ² or less, and 650 ≦ f8 = S × {(E + 100) / 100} ^1/2 , or 665 ≦ f9 = S × {(E + 100) / 100} ^1/2 + I.

The free-cutting copper alloy according to the seventh aspect of the present invention is the free-cutting copper alloy according to any one of the first to sixth aspects of the present invention . , Pressure vessels, and joints, or automotive parts and electrical parts that come into contact with liquids.

The method for producing a free-cutting copper alloy according to the eighth aspect of the present invention is the method for producing a free-cutting copper alloy according to any one of the first to seventh aspects of the present invention,
One or both of a cold working step and a hot working step, and an annealing step performed after the cold working step or the hot working step,
In the annealing step, the copper alloy is held under any of the following conditions (1) to (4),
(1) Hold at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes to 8 hours,
(2) Hold at a temperature of 515 ° C. or higher and lower than 525 ° C. for 100 minutes to 8 hours,
(3) The maximum temperature reached is 525 ° C. or more and 610 ° C. or less and is maintained for 20 minutes or more in the temperature range from 575 ° C. to 525 ° C., or (4) the temperature range from 575 ° C. to 525 ° C. is 0.1 Cool at an average cooling rate of ℃ / min or more and 2.5 ℃ / min or less,
Next, the temperature range from 460 ° C. to 400 ° C. is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min.

The method for producing a free-cutting copper alloy according to the ninth aspect of the present invention is the method for producing a free-cutting copper alloy according to any one of the first to fifth aspects of the present invention,
A casting process, and an annealing process performed after the casting process,
In the annealing step, the copper alloy is held under any of the following conditions (1) to (4),
(1) Hold at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes to 8 hours,
(2) Hold at a temperature of 515 ° C. or higher and lower than 525 ° C. for 100 minutes to 8 hours,
(3) The maximum temperature reached is 525 ° C. or more and 610 ° C. or less and is maintained for 20 minutes or more in the temperature range from 575 ° C. to 525 ° C., or (4) the temperature range from 575 ° C. to 525 ° C. is 0.1 Cool at an average cooling rate of ℃ / min or more and 2.5 ℃ / min or less,
Next, the temperature range from 460 ° C. to 400 ° C. is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min.

A method for producing a free-cutting copper alloy according to a tenth aspect of the present invention is a method for producing a free-cutting copper alloy according to any one of the first to seventh aspects of the present invention,
The material temperature at the time of hot working including the hot working process is 600 ° C. or higher and 740 ° C. or lower,
In the cooling process after hot plastic working, the temperature range from 575 ° C. to 525 ° C. is cooled at an average cooling rate of 0.1 ° C./min to 2.5 ° C./min, and 460 ° C. to 400 ° C. The temperature range up to is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min.

The method for producing a free-cutting copper alloy according to an eleventh aspect of the present invention is the method for producing a free-cutting copper alloy according to any one of the first to seventh aspects of the present invention,
One or both of a cold working step and a hot working step, and a low temperature annealing step performed after the cold working step or the hot working step,
In the low temperature annealing step, when the material temperature is in the range of 240 ° C. or more and 350 ° C. or less, the heating time is in the range of 10 minutes or more and 300 minutes or less, the material temperature is T ° C., and the heating time is t minutes, 150 ≦ The condition is (T−220) × (t) ^1/2 ≦ 1200.

14) In the metal structure, when the area ratio of the γ phase is more than 2% or the long side of the γ phase is longer than 50 μm, the machinability was good, but the corrosion resistance, cavitation resistance, The erosion-corrosion resistance, impact properties, high-temperature properties, tensile strength, and strength balance index were poor. In particular, when the γ phase is large, selective corrosion of the γ phase occurred in a dezincification corrosion test under a harsh environment (alloy No. S01, process No. AH1, AH2, AH6, C0, DH1, DH5, EH1, FH1). , Alloy No. S51, etc.). When the γ phase ratio is 1.5% or less, further 0.8% or less, and the length of the long side of the γ phase is 40 μm or less, and further 30 μm or less, the corrosion resistance, cavitation resistance, The erosion corrosion property, impact property, high temperature property, tensile strength and strength balance index were further improved (alloy Nos. S01 to S03, S21 to S35, step Nos. E1 and F1).
15) When the area ratio of the μ phase was more than 2%, the corrosion resistance, cavitation resistance, erosion corrosion resistance, impact characteristics, high temperature characteristics, and strength balance index deteriorated. In the dezincification corrosion test under harsh environment, intergranular corrosion and μ phase selective corrosion occurred (Alloy No. S01, Process No. AH4, AH8, BH3). When the μ phase ratio is 1.0% or less, further 0.5% or less, and the length of the long side of the μ phase is 15 μm or less, further 5 μm or less, the corrosion resistance, high temperature characteristics, tensile strength The strength balance index was further improved (alloy Nos. S01 to S03, step Nos. A3, A4, AH3, B1, B3, D2, D3, DH2, FH2).
When the area ratio of the β phase was more than 0.3%, the corrosion resistance, cavitation resistance, erosion corrosion resistance, elongation, impact characteristics, and high temperature characteristics were poor (Alloy Nos. S52 and S67).
When the area ratio of the κ phase was more than 65%, the machinability, elongation and impact properties were poor. On the other hand, when the area ratio of the κ phase was less than 30%, the machinability, cavitation resistance, and erosion corrosion resistance were poor (Alloy Nos. S56 and S53).
When the κ phase is present in the α phase and the presence of the κ1 phase is increased, the corrosion resistance, strength, elongation, strength balance index, impact properties, cavitation resistance, erosion corrosion resistance, and high temperature properties are improved. Good machinability could be maintained even if the decrease was reduced. The κ1 phase is presumed to lead to strengthening of the α phase, reduction of cutting resistance, and chip breaking (alloy Nos. S01 to 03, process Nos. AH1, AH2, A1, and A6). The relational expression f2 affected the amount of acicular κ phase (alloy Nos. S54, S66, S68 , S30, etc.).

Claims (12)

76.0 mass% to 78.7 mass% Cu, 3.1 mass% to 3.6 mass% Si, 0.40 mass% to 0.85 mass% Sn, 0.05 mass% to 0.14 mass % P or less and 0.005 mass% or more and less than 0.020 mass% Pb, the balance consisting of Zn and inevitable impurities,
The Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, the P content is [P] mass%, and the Pb content is [ Pb] mass%,
75.0 ≦ f1 = [Cu] + 0.8 × [Si] −7.5 × [Sn] + [P] + 0.5 × [Pb] ≦ 78.2
60.0 ≦ f2 = [Cu] −4.8 × [Si] −0.8 × [Sn] − [P] + 0.5 × [Pb] ≦ 61.5,
0.09 ≦ f3 = [P] / [Sn] ≦ 0.30,
And having a relationship
In the constituent phase of the metal structure, the α phase area ratio is (α)%, the β phase area ratio is (β)%, the γ phase area ratio is (γ)%, and the κ phase area ratio is (κ)%. When the area ratio of the μ phase is (μ)%,
30 ≦ (κ) ≦ 65,
0 ≦ (γ) ≦ 2.0,
0 ≦ (β) ≦ 0.3,
0 ≦ (μ) ≦ 2.0,
96.5 ≦ f4 = (α) + (κ),
99.4 ≦ f5 = (α) + (κ) + (γ) + (μ),
0 ≦ f6 = (γ) + (μ) ≦ 3.0,
35 ≦ f7 = 1.05 × (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 70,
And having a relationship
A free-cutting copper alloy characterized in that the κ phase is present in the α phase, the long side length of the γ phase is 50 μm or less, and the long side length of the μ phase is 25 μm or less.   Furthermore, it contains 1 or 2 or more selected from Sb of 0.01 mass% or more and 0.08 mass% or less, As of 0.02 mass% or more and 0.08 mass% or less, Bi of 0.01 mass% or more and 0.10 mass% or less. The free-cutting copper alloy according to claim 1. 76.5 mass% to 78.3 mass% Cu, 3.15 mass% to 3.5 mass% Si, 0.45 mass% to 0.77 mass% Sn, 0.06 mass% to 0.13 mass % P and 0.006 mass% or more and 0.018 mass% or less Pb, with the balance consisting of Zn and inevitable impurities,
The Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, the P content is [P] mass%, and the Pb content is [ Pb] mass%,
75.5 ≦ f1 = [Cu] + 0.8 × [Si] −7.5 × [Sn] + [P] + 0.5 × [Pb] ≦ 77.7,
60.2 ≦ f2 = [Cu] −4.8 × [Si] −0.8 × [Sn] − [P] + 0.5 × [Pb] ≦ 61.3,
0.10 ≦ f3 = [P] / [Sn] ≦ 0.27
And having a relationship
In the constituent phase of the metal structure, the α phase area ratio is (α)%, the β phase area ratio is (β)%, the γ phase area ratio is (γ)%, and the κ phase area ratio is (κ)%. When the area ratio of the μ phase is (μ)%,
33 ≦ (κ) ≦ 60,
0 ≦ (γ) ≦ 1.5,
0 ≦ (β) ≦ 0.1,
0 ≦ (μ) ≦ 1.0,
97.5 ≦ f4 = (α) + (κ),
99.6 ≦ f5 = (α) + (κ) + (γ) + (μ),
0 ≦ f6 = (γ) + (μ) ≦ 2.0,
38 ≦ f7 = 1.05 × (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 65,
And having a relationship
A free-cutting copper alloy characterized in that the κ phase is present in the α phase, the long side of the γ phase is 40 μm or less, and the long side of the μ phase is 15 μm or less.   The free-cutting copper alloy according to any one of claims 1 to 3, wherein a total amount of the inevitable impurities Fe, Mn, Co, and Cr is less than 0.08 mass%. .   The amount of Sn contained in the κ phase is 0.43 mass% to 0.90 mass%, and the amount of P contained in the κ phase is 0.06 mass% to 0.22 mass%. The free-cutting copper alloy according to any one of claims 1 to 4. Creep after Charpy impact test value of U notch shape 12 J / cm ² or more 45 J / cm ² or less, and was held for 100 hours at 0.99 ° C. in a state where the load is a load corresponding to 0.2% yield strength at room temperature The free-cutting copper alloy according to any one of claims 1 to 5, wherein the strain is 0.4% or less. It is a hot-worked material, has a tensile strength S (N / mm ² ) of 550 N / mm ² or more, an elongation E (%) of 12% or more, and a U-notch-shaped Charpy impact test value I (J / cm ² ). 12 J / cm ² or more 45 J / cm ² or less, and at 650 ≦ f8 = S × {( E + 100) / 100} 1/2 or 665 ≦ f9 = S ×, { (E + 100) / 100} 1/2 + I The free-cutting copper alloy according to any one of claims 1 to 5, wherein the free-cutting copper alloy is provided.   Any of Claims 1-7 characterized by being used for water supply equipment, industrial piping members, equipment in contact with liquids, pressure vessels, and joints, or automotive parts and electrical product parts in contact with liquids. The free-cutting copper alloy according to claim 1. A method for producing a free-cutting copper alloy according to any one of claims 1 to 8,
One or both of a cold working step and a hot working step, and an annealing step performed after the cold working step or the hot working step,
In the annealing step, the copper alloy is held under any of the following conditions (1) to (4),
(1) Hold at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes to 8 hours,
(2) Hold at a temperature of 515 ° C. or higher and lower than 525 ° C. for 100 minutes to 8 hours,
(3) The maximum temperature reached is 525 ° C. or more and 610 ° C. or less and is maintained for 20 minutes or more in the temperature range from 575 ° C. to 525 ° C., or (4) the temperature range from 575 ° C. to 525 ° C. is 0.1 Cool at an average cooling rate of ℃ / min or more and 2.5 ℃ / min or less,
Next, a method for producing a free-cutting copper alloy, wherein a temperature range from 460 ° C. to 400 ° C. is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min. A method for producing a free-cutting copper alloy according to any one of claims 1 to 6,
A casting process, and an annealing process performed after the casting process,
In the annealing step, the copper alloy is held under any of the following conditions (1) to (4),
(1) Hold at a temperature of 525 ° C. or more and 575 ° C. or less for 20 minutes to 8 hours,
(2) Hold at a temperature of 515 ° C. or higher and lower than 525 ° C. for 100 minutes to 8 hours,
(3) The maximum temperature reached is 525 ° C. or more and 610 ° C. or less and is maintained for 20 minutes or more in the temperature range from 575 ° C. to 525 ° C., or (4) the temperature range from 575 ° C. to 525 ° C. is 0.1 Cool at an average cooling rate of ℃ / min or more and 2.5 ℃ / min or less,
Next, a method for producing a free-cutting copper alloy, wherein a temperature range from 460 ° C. to 400 ° C. is cooled at an average cooling rate of 2.5 ° C./min to 500 ° C./min. A method for producing a free-cutting copper alloy according to any one of claims 1 to 8,
The material temperature at the time of hot working including the hot working process is 600 ° C. or higher and 740 ° C. or lower,
In the cooling process after hot plastic working, the temperature range from 575 ° C. to 525 ° C. is cooled at an average cooling rate of 0.1 ° C./min to 2.5 ° C./min, and 460 ° C. to 400 ° C. A method for producing a free-cutting copper alloy, characterized by cooling the temperature range up to 2.5 ° C./min to 500 ° C./min. A method for producing a free-cutting copper alloy according to any one of claims 1 to 8,
One or both of a cold working step and a hot working step, and a low temperature annealing step performed after the cold working step or the hot working step,
In the low temperature annealing step, when the material temperature is in the range of 240 ° C. or more and 350 ° C. or less, the heating time is in the range of 10 minutes or more and 300 minutes or less, the material temperature is T ° C., and the heating time is t minutes, 150 ≦ (T-220) × (t) ^1/2 ≦ 1200 A method for producing a free-cutting copper alloy, characterized in that