JP6448168B1 - Free-cutting copper alloy and method for producing free-cutting copper alloy - Google Patents

Abstract

This free-cutting copper alloy has Cu: 75.4-78.7%, Si: 3.05 to 3.65%, Sn: 0.10 to 0.28%, P: 0.05 to 0.14. %, And Pb: 0.005% or more, less than 0.020%, the balance consists of Zn and inevitable impurities, the composition satisfies the following relationship,
76.5 ≦ f1 = Cu + 0.8 × Si−8.5 × Sn + P ≦ 80.3, 60.7 ≦ f2 = Cu−4.6 × Si−0.7 × Sn−P ≦ 62.1, 25 ≦ f7 = [P] / [Sn] ≦ 1.0,
The area ratio (%) of the constituent phases satisfies the following relationship:
28 ≦ κ ≦ 67, 0 ≦ γ ≦ 1.0, 0 ≦ β ≦ 0.2, 0 ≦ μ ≦ 1.5, 97.4 ≦ f3 = α + κ, 99.4 ≦ f4 = α + κ + γ + μ, 0 ≦ f5 = γ + μ ≦ 2.0, 30 ≦ f6 = κ + 6 × γ ^1/2 + 0.5 × μ ≦ 70,
The long side of the γ phase is 40 μm or less, the long side of the μ phase is 25 μm or less, and the κ phase is present in the α phase.

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, pressure vessels, etc. used in various harsh environments 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 potable water appliances, valves, joints, pressure vessels, etc. for electrical, automotive, mechanical and industrial piping, 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 related to Pb has been activated in each country. For example, in California, the United States, the regulation which makes Pb content contained in a drinking water apparatus etc. into 0.25 mass% or less has been in force since January 2010 and since January 2014 in the United States. In the near future, it is said that regulations up to about 0.05 mass% will be made in view of the effects on infants. 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 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, It has been proposed to gradually cool to 180 ° C. and further to perform heat treatment.
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 corrosion resistance is improved by isolating the β phase by slow cooling after heat extrusion or heat treatment, the corrosion resistance is improved in severe environments. It is not connected to.
Further, 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 finally, 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, these copper alloys have low strength, particularly at high temperatures (for example, about 150 ° C.), so they are used, for example, in automobile parts used under high temperatures close to the engine room and under high temperatures and high pressures. Valves and piping that cannot be reduced in thickness and weight. Furthermore, for example, pressure vessels, valves, and pipes related to high-pressure hydrogen can be used only under a low normal pressure because of their low tensile strength.

  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, an extremely small amount of Pb of 0.02 mass% or less is contained, and mainly by considering the Pb content, the total content area of the γ phase and κ phase is simply defined to be excellent. It is intended to obtain free-cutting properties. Here, Sn acts on the formation and increase of the γ phase 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 and hard and brittle, if it contains a large amount of γ phase, it has corrosion resistance, ductility, impact properties, high temperature strength (high temperature creep) under severe conditions, A problem occurs in cold workability. 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 US 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), 62-77

  The present invention has been made to solve the problems of the prior art, and is a free-cutting copper alloy excellent in corrosion resistance, impact characteristics, ductility, normal temperature and high temperature in severe environments, and It is an object to provide a method for producing a free-cutting copper alloy. In this specification, unless otherwise specified, corrosion resistance refers to both dezincification corrosion resistance and stress corrosion cracking resistance. Moreover, a hot work material refers to a hot extrusion material, a hot forging material, and a hot rolling material. Cold workability refers to workability performed in the cold such as caulking and bending. 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 75.4 mass% or more and 78.7 mass% or less of Cu, and 3.05 mass. % And above 3.65 mass% Si, 0.10 mass% and above 0.28 mass% Sn, 0.05 mass% and below 0.14 mass% P, and 0.005 mass% and below 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%,
When the Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, and the P content is [P] mass%,
76.5 ≦ f1 = [Cu] + 0.8 × [Si] −8.5 × [Sn] + [P] ≦ 80.3,
60.7 ≦ f2 = [Cu] −4.6 × [Si] −0.7 × [Sn] − [P] ≦ 62.1,
0.25 ≦ f7 = [P] / [Sn] ≦ 1.0
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)%,
28 ≦ (κ) ≦ 67,
0 ≦ (γ) ≦ 1.0,
0 ≦ (β) ≦ 0.2,
0 ≦ (μ) ≦ 1.5,
97.4 ≦ f3 = (α) + (κ),
99.4 ≦ f4 = (α) + (κ) + (γ) + (μ),
0 ≦ f5 = (γ) + (μ) ≦ 2.0,
30 ≦ f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 70,
And having a relationship
The long side length of the γ phase is 40 μm or less, the long side length of the μ phase is 25 μm or less, and a needle-like κ phase exists in the α phase.

  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 1 or 2 or more selected from As of 0.08 mass% or less and Bi of 0.005 mass% or more and 0.20 mass% or less.

The free-cutting copper alloy according to the third aspect of the present invention includes 75.6 mass% to 77.9 mass% of Cu, 3.12 mass% to 3.45 mass% of Si, and 0.12 mass% to 0.002%. 27 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 total amount of the inevitable impurities Fe, Mn, Co, and Cr is less than 0.08 mass%,
When the Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, and the P content is [P] mass%,
76.8 ≦ f1 = [Cu] + 0.8 × [Si] −8.5 × [Sn] + [P] ≦ 79.3
60.8 ≦ f2 = [Cu] −4.6 × [Si] −0.7 × [Sn] − [P] ≦ 61.9,
0.28 ≦ f7 = [P] / [Sn] ≦ 0.84
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) ≦ 56,
0 ≦ (γ) ≦ 0.5,
(Β) = 0,
0 ≦ (μ) ≦ 1.0,
98.5 ≦ f3 = (α) + (κ),
99.6 ≦ f4 = (α) + (κ) + (γ) + (μ),
0 ≦ f5 = (γ) + (μ) ≦ 1.2,
30 ≦ f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 58,
And having a relationship
The long side length of the γ phase is 25 μm or less, the long side length of the μ phase is 15 μm or less, and a needle-like κ phase exists in the α phase.

  The free-cutting copper alloy according to the fourth aspect of the present invention is the free-cutting copper alloy according to the third aspect of the present invention, further comprising Sb of 0.012 mass% or more and 0.07 mass% or less, 0.025 mass%. It contains 1 or 2 or more selected from As of 0.07 mass% or less and Bi of 0.006 mass% or more and 0.10 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 amount of Sn contained in the κ phase is 0.11 mass%. The amount of P contained in the κ phase is 0.07 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 with a load corresponding to 0.2% proof stress at room temperature being less than 50 J / cm ² is 0.4% or less. .
The Charpy impact test value is a value for a U-notch test piece.

The free-cutting copper alloy according to the seventh aspect of the present invention is a hot-working material in the free-cutting copper alloy according to any of the first to fifth aspects of the present invention, and has a tensile strength S (N / mm ² ) is 540 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 660 ≦ f8 = S × {(E + 100) / 100} ^1/2 , or 685 ≦ 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 . It is used for pressure vessels / joints, automotive parts, or electrical product parts.

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 heated and cooled 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 505 ° 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 620 ° C. or less and is kept 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 step, and an annealing step performed after the casting step,
In the annealing step, the copper alloy is heated and cooled 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 505 ° 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 620 ° C. or less and is kept 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,
Including hot working process,
The material temperature when hot-working 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, free cutting with high strength at normal temperature and high temperature and excellent cold workability such as corrosion resistance, impact characteristics, ductility, wear resistance, pressure resistance characteristics, caulking and bending in severe environments. It is possible to provide a method for producing a free-cutting copper alloy and a free-cutting copper alloy.

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. T73) in Example 1. 2 is an electron micrograph of the structure of a free-cutting copper alloy (Test No. T73) in Example 1. Test No. 2 in Example 2 It is a metallographic micrograph of the cross section after using it under the severe water environment for 8 years of T601. Test No. 2 in Example 2 It is a metal micrograph of the cross section after the dezincification corrosion test 1 of T602. Test No. 2 in Example 2 It is a metal micrograph of the cross section after the dezincification corrosion test 1 of T10.

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 electric / automobile / machine / equipment such as appliances, valves, joints, sliding parts, etc. used for drinking water taken daily by humans and animals such as water taps, valves, joints, etc. It is used as an industrial piping member, a device, a part, a pressure vessel / joint that comes into contact with a liquid.

Here, in this specification, an element symbol with parentheses such as [Zn] indicates the content (mass%) of the element.
And in this embodiment, using this content display method, a plurality of compositional relational expressions are defined as follows.
Composition relation f1 = [Cu] + 0.8 × [Si] −8.5 × [Sn] + [P]
Composition relation f2 = [Cu] -4.6 × [Si] −0.7 × [Sn] − [P]
Compositional relation f7 = [P] / [Sn]

Furthermore, 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 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 relation f3 = (α) + (κ)
Tissue relational expression f4 = (α) + (κ) + (γ) + (μ)
Organizational relationship f5 = (γ) + (μ)
Tissue relational expression f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ)

  The free-cutting copper alloy according to the first embodiment of the present invention includes 75.4 mass% or more and 78.7 mass% or less of Cu, 3.05 mass% or more and 3.65 mass% or less of Si, and 0.10 mass% or more. It contains Sn of 0.28 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 made of Zn and inevitable impurities. The compositional relational expression f1 is within the range of 76.5 ≦ f1 ≦ 80.3, the compositional relational expression f2 is within the range of 60.7 ≦ f2 ≦ 62.1, and the compositional relational expression f7 is 0.25 ≦ f7 ≦ 1.0. Within the range of The area ratio of the κ phase is in the range of 28 ≦ (κ) ≦ 67, the area ratio of the γ phase is in the range of 0 ≦ (γ) ≦ 1.0, and the area ratio of the β phase is 0 ≦ (β) ≦ 0. In the range of 2, the area ratio of the μ phase is in the range of 0 ≦ (μ) ≦ 1.5. The organization relational expression f3 is in the range of f3 ≧ 97.4, the organizational relational expression f4 is in the range of f4 ≧ 99.4, the organizational relational expression f5 is in the range of 0 ≦ f5 ≦ 2.0, and the organizational relational expression f6 is in the range of 30 ≦ f6 ≦ 70. It is assumed to be inside. The long side length of the γ phase is 40 μm or less, the long side length of the μ phase is 25 μm or less, and the κ phase exists in the α phase.

  The free-cutting copper alloy according to the second embodiment of the present invention includes 75.6 mass% to 77.9 mass% Cu, 3.12 mass% to 3.45 mass% Si, and 0.12 mass% or more. It contains 0.27 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 compositional relational expression f1 is in the range of 76.8 ≦ f1 ≦ 79.3, the compositional relational expression f2 is in the range of 60.8 ≦ f2 ≦ 61.9, and the compositional relational expression f7 is 0.28 ≦ f7 ≦ 0.84. Within the range of The area ratio of the κ phase is in the range of 30 ≦ (κ) ≦ 56, the area ratio of the γ phase is in the range of 0 ≦ (γ) ≦ 0.5, the area ratio of the β phase is 0, and the area ratio of the μ phase is The range is 0 ≦ (μ) ≦ 1.0. Organizational relational expression f3 is in the range of f3 ≧ 98.5, organizational relational expression f4 is in the range of f4 ≧ 99.6, organizational relational expression f5 is in the range of 0 ≦ f5 ≦ 1.2, and organizational relational expression f6 is in the range of 30 ≦ f6 ≦ 58. It is assumed to be inside. The long side length of the γ phase is 25 μm or less, the long side length of the μ phase is 15 μm or less, and the κ phase is present in the α phase.

  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 005 mass% or more and 0.20 mass% or less.

  Further, in the free-cutting copper alloy according to the second embodiment of the present invention, Sb of 0.012 mass% to 0.07 mass%, As of 0.025 mass% to 0.07 mass%, 0.0. You may contain 1 or 2 or more selected from Bi of 006 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 0.11 mass% or more and 0.40 mass% or less, and is contained in the κ phase. It is preferable that the amount of P is 0.07 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 present invention, Charpy impact test values of U notch shape is less than 12 J / cm ² or more 50 J / cm ^2, 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 540 N / mm ² or more, the elongation E is 12% or more, the U-notch-shaped Charpy impact test value I is 12 J / cm ² or more, And the value of f8 = S × {(E + 100) / 100} ^1/2 , which is the product of the tensile strength (S) and {1/2 of ((elongation (E) +100) / 100}) is 660 or more. It is preferable that the value of f9 = S × {(E + 100) / 100} ^1/2 + I, which is the sum of f8 and I, is 685 or more.

  The reason why the component composition, the composition relational expressions f1, f2, and f7, the metal structure, the structural relational expressions f3, f4, f5, and f6, 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 Cu in an amount of at least 75.4 mass% or more. When the Cu content is less than 75.4 mass%, depending on the content of Si, Zn, Sn, Pb and the manufacturing process, the proportion of the γ phase exceeds 1.0%, corrosion resistance, impact characteristics, Poor ductility, room temperature strength, and high temperature properties (high temperature creep). In some cases, a β phase may appear. Therefore, the lower limit of the Cu content is 75.4 mass% or more, preferably 75.6 mass% or more, more preferably 75.8 mass% or more.
On the other hand, if the Cu content exceeds 78.7%, the effects on corrosion resistance, normal temperature strength, and high temperature strength are saturated, and the proportion of the κ phase may be excessive. Further, the μ phase with high Cu concentration, and in some cases, the ζ phase and the χ phase are likely to precipitate. As a result, the machinability, ductility, impact characteristics, 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 78.2 mass% or less, 77.9 mass% or less, and more preferably 77.6 mass% or less if the ductility and impact properties are regarded as important. It is.

(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, strength, high temperature characteristics, and wear resistance of the alloy of this embodiment. Regarding the machinability, in the case of the α phase, there is almost no improvement in machinability even if Si is contained. However, excellent machinability can be achieved even if a large amount of Pb is not contained by a phase harder than the α phase such as the γ phase, κ phase, and μ phase formed by the inclusion of Si. However, as the proportion of the metal phase such as γ phase and μ phase increases, the ductility, impact properties, cold workability degradation problems, corrosion resistance degradation problems in harsh environments, and long-term use Cause problems with high temperature characteristics. The κ phase is useful for improving machinability and strength. However, if the κ phase is excessive, the ductility, impact properties, and workability are lowered, and in some cases, the machinability is also deteriorated. For this reason, it is necessary to define the κ phase, γ phase, μ phase, and β phase within appropriate ranges.
Further, Si has an effect of greatly suppressing the evaporation of Zn during melting and casting, and the specific gravity can be reduced as the Si content is increased.

In order to solve these metal structure problems and satisfy all the characteristics, Si needs to be contained in an amount of 3.05 mass% or more, depending on the contents of Cu, Zn, Sn, and the like. The lower limit of the Si content is preferably 3.1 mass% or more, more preferably 3.12 mass% or more, and even more preferably 3.15 mass% or more. When emphasizing especially strength, 3.25 mass% or more is preferable. At first glance, it is considered 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. In addition, depending on the content of other elements, the relational expression of the composition, and the manufacturing process, there is an elongated, needle-like κ phase in the α phase with a Si content of about 2.95 mass% as a boundary. It becomes like this. And at about 3.05 mass%, the amount of acicular κ phase increases in the α phase, and the amount of acicular κ phase further increases when the Si content is between 3.1 mass% and 3.15 mass%. To do. The κ phase present in the α phase improves machinability, tensile strength, impact properties, wear resistance, and high temperature properties without impairing ductility. Hereinafter, the κ phase existing in the α phase is also referred to as κ1 phase.
On the other hand, if the Si content is too high, the κ phase will be excessive, and at the same time the κ1 phase will be excessive. If the κ phase is excessive, it becomes a problem in terms of ductility, impact properties, and machinability. If too much κ1 phase is present in the α phase, the ductility of the α phase itself deteriorates and becomes ductile as an alloy. Decreases. For this reason, the upper limit of the Si content is 3.65 mass% or less, preferably 3.55 mass% or less. Especially when workability such as ductility, impact characteristics, and caulking is emphasized, preferably 3.45 mass% or less. More preferably, it is 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 21.5 mass% or less, and a minimum is about 17.0 mass% or more.

(Sn)
Sn greatly improves dezincification corrosion resistance under particularly severe environments, and improves stress corrosion cracking resistance, machinability and wear resistance. In copper alloys composed 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 enhances the corrosion resistance of the α phase, which has the highest corrosion resistance, and at the same time improves the corrosion resistance of the κ phase, which has the second highest corrosion resistance. Sn is about 1.4 times as much as 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 increases, the corrosion resistance of the κ phase is further improved. The increase in the Sn content almost eliminates the superiority or inferiority of the corrosion resistance between the α phase and the κ phase, 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 the γ phase. Sn itself does not have a particularly excellent machinability function, but by forming a γ phase having excellent machinability, the machinability of the alloy is improved as a result. On the other hand, the γ phase deteriorates the corrosion resistance, ductility, impact characteristics, cold workability, and high temperature characteristics of the alloy and decreases the strength. Sn is distributed to the γ phase by about 10 to 17 times compared to the α phase. That is, the Sn amount allocated to the γ phase is about 10 to about 17 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, if the essential elements of Cu, Si, P, and Pb are set to a more appropriate blending ratio and the metal structure is not in a proper state including the manufacturing process, the inclusion of Sn increases the corrosion resistance of the κ phase and α phase. However, 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. Moreover, containing Sn in the κ phase improves the machinability of the κ phase. The effect is further increased by containing Sn together with P.

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 0.10 mass% or more, preferably 0.12 mass% or more, more preferably 0.15 mass% or more.
On the other hand, when Sn is contained exceeding 0.28 mass%, the proportion of the γ phase increases. As a countermeasure, it is necessary to increase the Cu concentration. However, since the κ phase increases as the Cu concentration increases, there is a possibility that good impact characteristics cannot be obtained. The upper limit of the Sn content is 0.28 mass% or less, preferably 0.27 mass% or less, more preferably 0.25 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. Pb is effective in machinability even if it is a very small amount, and starts to exhibit its effect at a content of 0.005 mass% or more. In the alloy of the present embodiment, the γ phase that excels in machinability is suppressed to 1.0% or less. Therefore, even if Pb is a small amount, it substitutes for the γ phase. The lower limit of the Pb content is preferably 0.006 mass% or more.
On the other hand, Pb is harmful to the human body and is related to components and metal structure, but has an effect on impact properties, high temperature properties, cold workability, and tensile strength. For this reason, the upper limit of the content of Pb is less than 0.020 mass%, and preferably 0.018 mass% or less.

(P)
P, like Sn, significantly improves the corrosion resistance in particularly severe environments.
As with Sn, the amount allocated to the κ phase is approximately twice 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 is remarkable in terms of the 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. However, P can improve the corrosion resistance of the κ phase by coexisting with Sn. P hardly improves the corrosion resistance of the γ phase. Further, the fact that the κ phase contains P slightly improves the machinability of the κ phase. By adding both Sn and P, the machinability is more effectively improved.
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 exceeding 0.14 mass%, not only the corrosion resistance effect is saturated, but also a compound of P and Si is easily formed, impact properties, ductility, and cold workability are deteriorated. On the other hand, machinability also worsens. 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 in a particularly severe environment like P and Sn.
In order to improve corrosion resistance by containing Sb, Sb needs to be contained in an amount of 0.01 mass% or more, and preferably contains 0.012 mass% or more of Sb. On the other hand, even if the Sb content exceeds 0.08 mass%, the effect of improving the corrosion resistance is saturated and the γ phase is increased. Therefore, the Sb content is 0.08 mass% or less, preferably 0.07 mass%. % Or less.
Moreover, in order to improve corrosion resistance by containing As, it is necessary to contain As at 0.02 mass% or more, and it is preferable to contain As at 0.025 mass% or more. On the other hand, even if As is contained in excess of 0.08 mass%, the effect of improving the corrosion resistance is saturated. Therefore, the content of As is 0.08 mass% or less, and preferably 0.07 mass% or less.
By containing Sb alone, the corrosion resistance of the α phase is improved. Sb is a low melting point metal that has a higher melting point than Sn, exhibits a similar behavior to Sn, and is more distributed to the γ and κ phases than the α phase. Sb has the effect of improving the corrosion resistance of the κ phase when added together with Sn. However, the effect of improving the corrosion resistance of the γ phase is small both when containing Sb alone and when containing Sb together with Sn and P. Rather, containing an excessive amount of Sb may increase the γ phase.
Among Sn, P, Sb, and As, As enhances the corrosion resistance of the α phase. 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, As has little effect on improving the corrosion resistance of the κ phase and γ phase.
When both Sb and As are contained, the effect of improving the corrosion resistance is saturated even if the total content of Sb and As exceeds 0.10 mass%, and the ductility, impact characteristics, and cold workability are reduced. For this reason, it is preferable that the total amount of Sb and As be 0.10 mass% or less.
Bi further improves the machinability of the copper alloy. For that purpose, it is necessary to contain Bi 0.005 mass% or more, and it is preferable to contain 0.006 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 0.20 mass% or less because of the impact on impact characteristics, high temperature characteristics, hot workability, and cold workability Is 0.15 mass% or less, more preferably 0.10 mass% or less.

(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, Sb, As, Bi, Ca, Al, B, Zr, and Ni are obtained from other free-cutting copper alloys. And rare earth elements. 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, Cr, Ti, Co, In, Ni, Se, and Te 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 is preferably less than 0.05 mass%.
Fe, Mn, Co, and Cr form an intermetallic compound with Si, and in some cases form an intermetallic compound with P, affecting 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. The total content of these Fe, Mn, Co, and Cr is preferably less than 0.08 mass%, and the total amount is more preferably less than 0.07 mass%, and even more preferably 0.06 mass%. Is less than.
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 impurity elements (inevitable impurities) is desirably controlled and limited in view of the influence on the characteristics of the alloy of the present 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, Sn is given a large coefficient of -8.5. If the compositional relational expression f1 is less than 76.5, no matter how the manufacturing process is devised, the proportion of the γ phase increases, the β phase appears in some cases, and the long side of the γ phase becomes longer. Corrosion resistance, ductility, impact properties, and high temperature properties deteriorate. Therefore, the lower limit of the compositional relational expression f1 is 76.5 or more, preferably 76.8 or more, more preferably 77.0 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 is present, the γ phase tends to be divided, and more corrosion resistance, ductility, impact characteristics, at room temperature Strength and high temperature characteristics are improved.
On the other hand, the upper limit of the compositional relational expression f1 mainly affects the proportion of the κ phase, and if the compositional relational formula f1 is larger than 80.3, the proportion of the κ phase is excessive when emphasis is placed on ductility and impact characteristics. . In addition, the μ phase is easily precipitated. When there are too many κ phases and μ phases, ductility, impact properties, cold workability, high temperature properties, hot workability, corrosion resistance, and machinability deteriorate. Therefore, the upper limit of the compositional relational expression f1 is 80.3 or less, preferably 79.6 or less, more preferably 79.3 or less, and further preferably 78.9 or less.
Thus, a copper alloy having excellent characteristics can be obtained by defining the compositional 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 60.7, the proportion of the γ phase in the metal structure increases, and other metal phases such as the β phase are likely to appear and remain, and the corrosion resistance, ductility, impact characteristics are increased. , Cold workability and high temperature characteristics deteriorate. 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 60.7 or more, preferably 60.8 or more, more preferably 61.0 or more.
On the other hand, when the compositional relational expression f2 exceeds 62.1, 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. Although there is a relationship with the hot working rate and the extrusion ratio, for example, hot extruding at about 630 ° C. and hot forging (both material temperatures immediately after hot working) become difficult. In addition, a coarse α phase having a length exceeding 1000 μm and a width exceeding 200 μm is likely to appear in the metal structure parallel to the hot working direction. When a coarse α phase is present, machinability is reduced, and the length of the long side of the γ phase existing at the boundary between the α phase and the κ phase is increased. Further, the κ1 phase is less likely to appear in the α phase, and the strength and wear resistance are lowered. Also, the solidification temperature range, ie (liquidus temperature-solidus temperature) exceeds 50 ° C, shrinkage cavities during casting become prominent, and sound casting is obtained. It becomes impossible. Therefore, the upper limit of the compositional relational expression f2 is 62.1 or less, preferably 61.9 or less, and more preferably 61.7 or less.
Thus, by defining the composition relational expression f2 in a narrow range as described above, a copper alloy having excellent characteristics can be manufactured with a high yield. 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 f7)
The composition relational expression f7 particularly relates to the corrosion resistance. To the Cu—Zn—Si alloy, 0.05 to 0.14 mass% of P and 0.10 to 0.28 mass% of Sn are added together, and [P] / [Sn] is a mass concentration ratio. 0.25 to 1.0, atomic concentration ratio of about 1 to about 4, that is, when there are 1 to 4 P atoms per 1 Sn atom, anti-zinc corrosion resistance of α phase and κ phase Will improve. When [P] / [Sn] is less than 0.25, the improvement in corrosion resistance is small, the high temperature characteristics are deteriorated, and the effect on machinability is reduced. It is more preferably 0.28 or more, and further preferably 0.32 or more. On the other hand, when [P] / [Sn] exceeds 1.0, not only the effect on dezincification corrosion resistance but also the ductility becomes poor, and the impact characteristics deteriorate. Preferably, [P] / [Sn] is more preferably 0.84 or less, and still more preferably 0.64 or less.

(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 Patent Document 3 differ in the content of Pb and Sn, which is a selective element. This embodiment and Patent Document 4 differ in the content of Pb and Sn, which is a selective element. This embodiment and Patent Documents 6 and 7 differ depending on whether or not Zr is contained. This embodiment is different 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. This embodiment differs from Patent Document 10 in whether or not Sn, P, and Pb are contained.
As described above, the composition range is different between the alloy of the present embodiment and the Cu—Zn—Si alloys described in Patent Documents 3 to 9 except Patent Document 5. 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.

<Metallic structure>
A 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 elements. Finally, 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 When 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. Moreover, the Si concentration of the μ phase is about 2.5 to about 3 times the Si concentration of the α phase, and the Si concentration of the γ phase is about 2 to about 2.5 times the Si concentration of the α phase.
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. The same can be said for drinking water in the use environment in which many solutions are present, such as the use environment of members including the automobile parts, machine parts, and industrial piping.

  On the other hand, even if the amount of γ phase, or γ phase, μ phase, β phase is controlled, that is, the proportion of each phase is greatly reduced or eliminated, α phase, α ′ phase, κ The corrosion resistance of a Cu—Zn—Si alloy composed of three phases 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. Furthermore, when the κ phase is corroded, the corroded κ phase becomes a corrosion product rich in Cu and corrodes the α phase, so 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. The γ phase is elongated mainly at the α-κ phase boundary (the phase boundary between the α phase and the κ phase) and the crystal grain boundary. Since the γ phase becomes a stress concentration source, it becomes a starting point of chip division during cutting, and has a great effect of promoting chip division and reducing cutting resistance. On the other hand, the γ phase is a cause of the stress concentration, which lowers ductility, cold workability and impact properties, and lowers tensile strength due to lack of ductility. Furthermore, the high temperature creep strength is lowered by the high temperature creep phenomenon. Since the μ phase is mainly present at the grain boundary of the α phase, the phase boundary between the α phase and the κ phase, it becomes a micro stress concentration source like the γ phase. Due to stress concentration sources or due to grain boundary sliding, the μ phase increases stress corrosion cracking susceptibility, reduces impact properties, and reduces ductility, cold workability, room temperature and high temperature strength. Note that the μ phase has the effect of improving machinability like the γ phase, but the effect is much 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, the γ phase and the μ phase is greatly reduced or eliminated, the inclusion of a small amount of Pb and the α phase, α ′ phase There is a possibility that satisfactory machinability cannot be obtained with only three phases of κ phase. Therefore, in order to improve the corrosion resistance, ductility, impact characteristics, strength, high temperature characteristics in severe use environment on the premise of containing a small amount of Pb and having excellent machinability, the structure of the metal structure The phase (metal phase, crystal phase) needs to be specified as follows.
In the following, 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 under severe environments, strength at room temperature, high temperature characteristics, ductility, cold workability, and impact characteristics. To make things, the γ phase must be limited. In order to make the corrosion resistance excellent, it is necessary to contain Sn, but the inclusion of Sn further increases the γ phase. 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 f7, a structural relational expression described later, and a manufacturing process are limited.

(Β phase and other phases)
In order to obtain good corrosion resistance and high ductility, impact properties, strength, and high temperature strength, the proportion of other phases such as β phase, γ phase, μ phase, and ζ phase in the metal structure is particularly important .
The proportion of the β phase must be at least 0.2% or less, preferably 0.1% or less, and optimally, the β phase is preferably absent.
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 needs to be 0% or more and 1.0% or less, and the length of the long side of the γ phase needs to be 40 μm or less.
The length of the long side of the γ phase is measured by the following method. The maximum length of the long side of the γ phase is measured in one field of view mainly using a metal micrograph at a magnification of 500 times or 1000 times. This operation is performed in an arbitrary field of view as described later. The average value of the maximum lengths of the long sides of the γ phase obtained in each field of view is calculated and taken 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.
When the γ phase is increased, not only the corrosion resistance but also the strength, ductility, cold workability, impact characteristics, and high temperature characteristics deteriorate. In order to emphasize and improve these characteristics, the proportion of the γ phase is 1.0% or less, preferably 0.8% or less, and more preferably 0.5% or less. It is optimal that the γ phase is not sufficiently observed with a 500 × microscope, ie substantially 0%.
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 40 μm or less, preferably 25 μm or less, more preferably 10 μm or less, and optimally 5 μm or less. It is. The size that can be clearly distinguished from the γ phase with a 500 × microscope is the γ phase having a long side length of about 2 μm or more.
The greater the amount of γ phase, the more likely the γ phase is selectively corroded. Further, the longer the γ phase is, the more easily the γ phase is selectively corroded, and the progress of the corrosion in the depth direction is accelerated. In addition, the more parts are corroded, the more the corrosion resistance of the α ′ phase existing around the corroded γ phase, the κ phase, and the α phase is affected.
On the other hand, regarding machinability, the presence of the γ phase has the greatest effect of improving the machinability of the copper alloy of the present embodiment, but it is necessary to eliminate it as much as possible from various problems of the γ phase. Yes, the κ1 phase described later is an alternative to the γ phase. It is also effective to increase the Sn concentration and the P concentration in the κ phase.

  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.

(Μ phase)
The μ phase is effective in improving machinability, but since it affects corrosion resistance, ductility, cold workability, impact properties, tensile strength at room temperature, and high temperature properties, at least the proportion of the μ phase Must be 0% or more and 1.5% 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. Further, when an impact action is applied, cracks starting from the μ phase existing at the grain boundary are likely to occur. Further, for example, when a copper alloy is used for a valve or a high-pressure gas valve used around an automobile engine, if it 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, further preferably 4 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, the magnification is 500 ×, and in some cases, a 1000 × metal micrograph or a 2000 × or 5000 × secondary electron image photo (electron micrograph) is used in one field of view. Measure the maximum length of the long side of the μ phase. 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 1.0% or less, and the Pb content having the excellent machinability function is limited to less than 0.02 mass%, In order to provide excellent machinability, the proportion of the κ phase needs to be at least 28%. The proportion of the κ phase is preferably 30% or more, more preferably 32% or more, and most preferably 34% or more. The tensile strength at room temperature and the high temperature strength increase as the proportion of the κ phase increases. Further, when the proportion of the κ phase is the minimum amount that satisfies the machinability, the ductility is high, the impact characteristics are excellent, and the corrosion resistance is good.
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. In addition, it is superior in strength, machinability, wear resistance, and high temperature characteristics than the α phase.
As the proportion of the κ phase increases, the machinability is improved, the tensile strength and the high temperature strength are high, and the wear resistance is improved. However, on the other hand, as the κ phase increases, the ductility, cold workability, and impact properties gradually decrease. When the proportion of the κ phase reaches a certain amount, specifically, the effect of improving machinability is saturated at about 50%, and the machinability decreases when the κ phase increases. To do. When the proportion of the κ phase reaches a certain amount, the hardness index increases, but as the ductility decreases, the improvement in tensile strength begins to saturate, and the cold workability and hot workability also deteriorate. In view of deterioration of ductility and impact properties, and improvement in strength and machinability, the proportion of the κ phase needs to be 67% or less, and approximately 2/3 or less. That is, the excellent characteristics of the κ phase are activated by the coexistence of the soft α phase and the κ phase of about 2/3 or less, which are suitable for ductility of about 1/3 or more. The proportion of the κ phase is preferably 60% or less, more preferably 56% or less, and 50% or less when ductility, impact characteristics, and workability are emphasized.
In order to obtain excellent machinability in a state where the area ratio of the γ phase is limited to 1.0% or less and the Pb content is limited to less than 0.02 mass%, the coverage of the κ phase and the α phase itself is limited. It is necessary to improve machinability. That is, by containing Sn and P in the κ phase, the machinability of the κ phase is improved. Furthermore, the presence of a needle-like κ phase (κ1 phase) in the α phase improves the machinability of the α phase and improves the machinability of the alloy with almost no loss of ductility. About 32% to about 56% of the κ phase in the metal structure has a good balance of ductility, cold workability, strength, impact properties, corrosion resistance, high temperature properties, machinability, and wear resistance. Ideal for.

(Existence of elongated and needle-like κ phase (κ1 phase) in α phase)
When the above-described composition and compositional relational expressions f1 and f2 and the process requirements are satisfied, an acicular κ 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, a needle-like κ1 phase starts to exist in the α phase when the Si amount is about 2.95 mass% or more. When the amount of Si is about 3.05 mass% or more, it becomes clear, and when it is about 3.12 mass% or more, the κ1 phase is more clearly present in the α phase. Further, the presence of the κ1 phase is affected by the compositional relational expression. For example, when the compositional relational expression f2 is 61.9 or less, and further 61.7 or less, the κ1 phase is more likely to exist.
However, if the proportion of the κ1 phase in the α phase increases, that is, if the amount of the κ1 phase increases too much, the ductility and impact characteristics of the α phase are impaired. The amount of the κ1 phase in the α phase is mainly linked with 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 f2. When the amount of κ phase exceeds 67%, the amount of κ1 phase present in the α phase becomes too large. Also 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 preferably 67% or less, more preferably 60% or less, and ductility, cold workability and impact. When emphasizing characteristics, it is preferably 56% or less, and more preferably 50% 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 f3, f4, f5, f6)
In order to obtain excellent corrosion resistance, ductility, impact characteristics, and high temperature characteristics, the total proportion of α phase and κ phase (structure relational expression f3 = (α) + (κ)) is 97.4% or more. . The value of f3 is preferably 98.5% or more, more preferably 99.0% or more. Similarly, the sum of the proportions of α phase, κ phase, γ phase, and μ phase (structure relationship f4 = (α) + (κ) + (γ) + (μ)) is 99.4% or more, preferably Is 99.6% or more.
Further, the total ratio of the γ phase and the μ phase (f5 = (γ) + (μ)) is 0% or more and 2.0% or less. The value of f5 is preferably 1.2% or less, more preferably 0.6% or less.
Here, in the relational expression of the metal structure, f3 to f6, 10 kinds 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. In addition, the needle-like κ phase (κ1 phase) existing in the α 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, the intermetallic compound formed by Si, P, and an element inevitably mixed (for example, Fe, Co, Mn) is out of the applicable range of the area ratio of the metal phase. However, since these intermetallic compounds affect the machinability, it is necessary to keep an eye on inevitable impurities.

(Organizational relational expression f6)
In the alloy of this embodiment, the Cu-Zn-Si alloy has good machinability while keeping the Pb content to a minimum, and particularly excellent corrosion resistance, impact properties, ductility, cold workability, It is necessary to satisfy all of normal temperature and high temperature strength. However, machinability and excellent corrosion resistance and impact characteristics are contradictory characteristics.
In terms of the metal structure, the machinability is better if it contains more γ phase, which has the best 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 1.0% or less, it has been found from the experimental results that the value of the above-described structure relational expression f6 is in an appropriate range in order to obtain good machinability. .

Since the γ phase is the most excellent in machinability, a six-fold higher coefficient is given to the value of the square root of the proportion ((γ) (%)) of the γ phase in the structural relational expression f6 regarding the machinability. As described above, the γ phase has a great effect on improvement of chip breaking property and reduction of cutting resistance even if the amount is small. On the other hand, the coefficient of the κ phase is 1. The κ phase forms a metal structure together with the α phase, and is not unevenly distributed at the phase boundary such as the γ phase and the μ phase, and exhibits an effect according to the existence ratio. The coefficient of μ phase is 0.5, and the effect of improving machinability is small. The β phase and the other phases have almost no effect of improving the machinability and may act negatively in some cases. However, in the present embodiment, since they hardly exist, they are not included in f6. In order to obtain good machinability, the value of the structure relational expression f6 needs to be 30 or more. f6 is preferably 32 or more, more preferably 34 or more.
On the other hand, when the structural relational expression f6 exceeds 70, the machinability deteriorates conversely, and the impact characteristics and ductility become conspicuous. For this reason, the organization relational expression f6 needs to be 70 or less. The value of f6 is preferably 62 or less, more preferably 58 or less. The coexistence of the κ phase with the soft α phase has the effect of improving the machinability of the κ phase. However, if the proportion of the γ phase and the Pb content are greatly limited, the presence of the κ phase When the ratio is about 50%, the effect of improving the chip breaking property and the effect of reducing the cutting resistance are saturated, and gradually worsens as the amount of κ phase increases. That is, even if the amount of κ phase increases too much, the composition ratio and the mixed state with the soft α phase deteriorate, and the fragmentation property of chips decreases. When the proportion of the κ phase exceeds about 50%, the influence of the high κ phase becomes strong, and the cutting resistance gradually increases.

(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 0.10 mass% to 0.28 mass%, and P is contained in an amount of 0.05 mass% to 0.14 mass%. It is preferable to make it.
In the alloy of this embodiment, when the Sn content is 0.10 to 0.28 mass%, when the Sn amount allocated to the α phase is 1, the κ phase is about 1.4 and the γ phase is Sn is distributed at a ratio of about 10 to about 17 and about 2 to about 3 for the μ phase. The amount allocated to the γ phase can be reduced to about 10 times the amount allocated to the α phase by devising the manufacturing process. For example, in the case of the alloy of this embodiment, in a Cu—Zn—Si—Sn alloy containing Sn in an amount of 0.2 mass%, the proportion of α phase is 50%, the proportion of κ phase is 49%, γ When the proportion of the phase is 1%, the Sn concentration in the α phase is about 0.15 mass%, the Sn concentration in the κ phase is about 0.22 mass%, and the Sn concentration in the γ phase is about 1.8 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 the γ phase is greatly limited as in the alloy of the present embodiment, Sn is effectively used for the corrosion resistance and machinability of the α phase and the κ phase 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 κ phase. The amounts of Sn and P contained in the κ phase are about 1.4 times and about twice as much as the amounts of Sn and P contained in the α phase, respectively. 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 by Sn and P 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. Note that by adding both Sn and P, the corrosion resistance of the κ phase can be improved, and when the ratio [P] / [Sn] (f7) is appropriate, the corrosion resistance is further improved.

  When the Sn content is less than 0.10 mass%, the corrosion resistance of the κ phase is inferior to that of the α phase, and therefore the κ phase may be selectively corroded under severe water quality. Many distributions of Sn to the κ phase improve the corrosion resistance of the κ phase, which is inferior in corrosion resistance to the α phase, and make the corrosion resistance of the κ phase containing Sn above a certain concentration approach the corrosion resistance of the α phase. At the same time, the inclusion of Sn in the κ phase improves the machinability function of the κ phase and improves the wear resistance. For this purpose, the Sn concentration in the κ phase is preferably 0.11 mass% or more, more preferably 0.14 mass% or more.

On the other hand, Sn is distributed in a large amount in 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 because the crystal structure of the γ phase is mainly a BCC structure. . On the contrary, when the proportion of the γ phase is large, the amount of Sn allocated to the κ phase is reduced, and the degree of improvement in the corrosion resistance of the κ phase is reduced. Decreasing the proportion of the γ phase increases the amount of Sn allocated to the κ phase. When a large amount of Sn is distributed in the κ phase, the corrosion resistance and machinability of the κ phase are improved, and the loss of machinability of the γ phase can be compensated. It seems that as a result of Sn contained in the κ phase in a predetermined amount or more, the machinability function of the κ phase itself and the cutting performance of the chips were improved. However, if the Sn concentration in the κ phase exceeds 0.40 mass%, the machinability of the alloy is improved, but the ductility and toughness of the κ phase begin to be impaired. If the ductility and cold workability are more important, the upper limit of the Sn concentration in the κ phase is preferably 0.40 mass% or less, more preferably 0.36 mass% or less.
On the other hand, when the Sn content is increased, it becomes difficult to reduce the amount of γ phase due to the relationship with Cu and Si. In order to make the occupying ratio of the γ phase 1.0% or less, further 0.5% or less, it is necessary to make the Sn content in the alloy 0.28 mass% or less, and the Sn content is It is preferable to set it to 0.27 mass% or less.

  As in the case of Sn, when a large amount of P is distributed to the κ phase, the corrosion resistance is improved and the machinability of the κ phase is improved. However, when an excessive amount of P is contained, it is expended in the formation of Si intermetallic compounds, which deteriorates the characteristics, or the solid solution of excess P in the κ phase causes the ductility of the κ phase. , Impairing toughness, impairing impact properties and ductility as an alloy. The lower limit value of the P concentration in the κ phase is preferably 0.07 mass% or more, more preferably 0.08 mass% or more. The upper limit value of the P concentration in the κ phase is preferably 0.22 mass% or less, more preferably 0.18 mass% or less.

<Characteristic>
(Normal temperature strength and high temperature characteristics)
As strength required in various fields including containers, fittings, piping, valves, automotive valves, fittings related to hydrogen in drinking water valves, equipment, hydrogen stations, hydrogen power generation etc. or in high pressure hydrogen environment, Tensile strength is important. In the case of a pressure vessel, the allowable stress is affected by the tensile strength. Unlike the iron-based material, the alloy according to the present embodiment does not cause hydrogen embrittlement. Therefore, when the alloy has high strength, the allowable stress and the allowable pressure are increased, and can be used more safely. 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, of course, they are not deformed or destroyed when pressure or stress is applied. Is required.
For that purpose, it is preferable that the hot extruded material, the hot rolled material, and the hot forged material, which are hot processed materials, are high strength materials having a tensile strength at room temperature of 540 N / mm ² or more. Tensile strength at room temperature, more preferably 560N / mm ² or more, more preferably 575N / mm ² or more, and most preferably at 590N / 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 in a copper alloy. 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 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, the tensile strength is improved by about 10 to about 60 N / mm ² compared to the hot-worked material before the heat treatment, depending on the composition and heat treatment conditions. 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 appropriate conditions of 505 ° C. or higher and 575 ° C. or lower, 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 increases the proportion of the κ phase. This greatly exceeds the softening of the α and κ phases. As a result, not only the corrosion resistance but also the tensile strength, ductility, impact value, and cold workability are greatly improved compared to the hot-worked material, resulting in a high strength, high ductility and high toughness alloy. Incidentally, the elongation or impact value is improved by about 1.05 to about 2 times, although it depends on the composition and manufacturing process, as compared with the hot-worked material before the heat treatment.
On the other hand, in some cases, the hot-worked material is cold-drawn, drawn, or rolled after 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 heat treatment _material, 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 × (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 the target strength, elongation, and impact value according to the application.
On the other hand, when cold working such as drawing, wire drawing, and rolling is performed, and then heat treatment is performed under appropriate conditions, tensile strength, elongation, and impact properties are all compared to hot-worked materials, particularly hot-extruded materials. Rise. In some cases, a tensile test cannot be performed on a forged product or the like. In that case, since there is a strong correlation between the Rockwell B scale (HRB) and the tensile strength (S), it is possible to simply measure the Rockwell B scale and estimate the tensile strength. However, this correlation is based on the premise that the composition of the present embodiment is satisfied and the requirements of f1 to f7 are satisfied.
HRB: 65 to 88: S = 4.3 × HRB + 242
HRB: When 88 and 99 or less: S = 11.8 × HRB-422
The tensile strength when the HRB is 65, 75, 85, 88, 93, 98 is estimated to be approximately 520, 565, 610, 625, 675, 735 N / mm ² , respectively.
Regarding the high temperature creep, it is preferable that the creep strain after holding the copper alloy at 150 ° C. for 100 hours with a stress corresponding to 0.2% proof stress at room temperature is 0.4% or less. This creep strain is more preferably 0.3% or less, and still more preferably 0.2% or less. In this case, even when exposed to a high temperature such as a high-temperature high-pressure valve or a valve material close to the engine room of an automobile, it is difficult to deform and has excellent high-temperature characteristics.

Even if the machinability is good and the tensile strength is high, the use is limited when the ductility and cold workability are poor. Regarding cold workability, for example, in water-related appliances, automobiles, and electrical parts, hot forging materials and cutting materials may be slightly caulked and bent, and it is necessary that they do not break. . Machinability requires a kind of brittleness because the chips are divided, but cold workability is a contradictory characteristic. Similarly, 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 540 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, and the value of f8 = S × {(E + 100) / 100} ^1/2 is 660 or more. It is a measure of one high strength and high ductility material. f8 is more preferably 675 or more. In processing rate between 2-15% cold, when subjected to cold working at an appropriate working ratio after heat treatment before or thermal treatment, more than 12% elongation and 580N / mm ² or more, further 600N / mm ² or more in tensile strength Can be combined.
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. Even after the alloy is exposed to 150 ° C. for 100 hours with a stress corresponding to 0.2% proof stress at room temperature, the creep strain is about 4 to 5%. For this reason, the tensile strength and heat resistance of the alloy of the present embodiment are higher than those of conventional free-cutting brass containing Pb. That is, the alloy of this embodiment is excellent in corrosion resistance, has high strength at room temperature, adds high strength, and hardly deforms even when exposed to high temperature for a long time, making it possible to make thin and lightweight by making use of high strength. Become. In particular, in the case of a forging material such as a valve for high-pressure gas or high-pressure hydrogen, it is not possible to substantially perform cold working, so that the allowable pressure can be increased, or the thickness and weight can be reduced by utilizing high strength.
The high temperature characteristics of the alloy of the present embodiment are substantially the same for the extruded material and the cold-worked material. That is, 0.2% proof stress is increased by performing cold working, but the alloy is kept at 150 ° C. for 100 hours even in a state where a load corresponding to 0.2% proof stress increased by the cold working is applied. Creep strain after exposure 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 performing a Charpy impact test at U-notch test piece, Charpy impact test value (I) is preferably 12 J / cm ² or more, more preferably 16J / cm ² or more. For hot-worked material that has 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 20 J / cm ² or more. Optimally, it is 24 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 50 J / cm ² in particular. On the contrary, when the Charpy impact test value exceeds 50 J / cm ² , ductility and toughness increase, so that the cutting resistance increases and the machinability deteriorates, such as chips becoming more likely to be connected. For this reason, the Charpy impact test value is preferably 50 J / cm ² or less.
When the amount of hard κ phase increases, the amount of acicular κ phase present in the α phase increases, or the Sn concentration in the κ phase increases, the strength and machinability increase, but the toughness, that is, the impact properties decrease. . For this reason, strength, machinability, and toughness (impact characteristics) are contradictory characteristics. The following formula defines a strength / ductility / impact balance index (hereinafter also referred to as a strength balance index) f9 in which impact characteristics are added to strength / ductility.
Regarding the hot-worked material, the tensile strength (S) is 540 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 685 or more, more preferably 700 or more, high strength Thus, it can be said that the material has ductility and toughness.
Although the impact characteristics and ductility are similar characteristics, it is preferable that the strength balance index f8 is 660 or more or the strength balance index f9 is 685 or more.

The impact characteristics are 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 impact characteristics are particularly deteriorated when a μ phase having a long side exceeding 25 μm exists at a grain boundary or a 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 than the α phase and the κ phase in a harsh environment, 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 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.

<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. Not only is it affected by the hot working temperature and heat treatment conditions of hot extrusion and hot forging, but also the average cooling rate (also referred to simply as the cooling rate) during the cooling process in hot working or heat treatment is 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 the present embodiment is a process necessary for the alloy of the present embodiment and has a balance with the composition, but basically plays the following important role.
1) The γ phase that deteriorates the corrosion resistance and impact characteristics is reduced, and the length of the long side of the γ phase is reduced.
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 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 casting products are cast into a predetermined mold at about 900 ° C. to about 1100 ° C., which is about 50 ° C. to about 200 ° C. higher than the melting point, and some cooling means such as air cooling, slow cooling, and water cooling Cooled by. And, after solidification, the constituent phases change variously.

(Hot processing)
Examples of hot working include hot extrusion, hot forging, and hot rolling.
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 decreases. 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 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.

In the present embodiment, 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. Subsequently, 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 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. The temperature drop from 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 it may be water-cooled 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 completely different cooling rate in the cooling process after hot working as compared with 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. Although it depends on the forging equipment capacity and the degree of processing of the forged product, it is preferable to carry out at 605 ° C. to 695 ° C. because the amount of γ phase is reduced immediately after forging, the α phase becomes finer, and the strength is improved.
In addition, if the extrusion temperature at the time of manufacturing the hot extrusion rod is lowered and the metal structure is small in γ phase, when hot forging is performed on this hot extrusion rod, even if the hot forging temperature is high, A hot forged structure in which a state with little γ phase is maintained is obtained.
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 amount of phase is insufficiently reduced. 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./min or more and 500 ° C./min or less, preferably 4 ° C./min or more, more preferably 8 ° C./min 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 conversely, the cooling rate is increased in the temperature range of 460 ° C. to 400 ° C., thereby completing a material having a more suitable metal structure.
In the case where the heat treatment is performed again in the next step or the final step, it is necessary to control the cooling rate in the temperature range from 575 ° C. to 525 ° C. after the hot working and in the temperature range from 460 ° C. to 400 ° C. do not do.

(Hot rolling)
In the case of hot rolling, rolling is repeated, but the final hot rolling temperature (material temperature after 3 to 4 seconds) is preferably 600 ° C. or higher and 740 ° C. or lower, more preferably 605 ° C. or higher and 670 ° C. It is as follows.
In the cooling after hot extrusion and hot rolling, the temperature region of 575 ° C. to 525 ° C. is cooled at a cooling rate of 0.1 ° C./min to 2.5 ° C./min, similar to hot forging. By cooling and cooling a temperature range of 460 to 400 ° C. at a cooling rate of 2.5 ° C./min or more and 500 ° C./min or less, it becomes possible to obtain a metal structure with less γ phase.

(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 usually 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 of this embodiment, when it 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, tensile strength, ductility, corrosion resistance, impact properties, and high temperature properties are improved. However, if heat treatment is performed under conditions where the temperature of the material exceeds 620 ° 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 505 ° C. and less than 525 ° C., a time of 100 minutes or longer, preferably 120 minutes or longer is required. Furthermore, in the heat treatment for a long time at a temperature lower than 505 ° 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 505 degreeC or more, Preferably it is 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 or less.
The advantage of heat treatment at this temperature is that, when the amount of γ phase of the material before heat treatment is small, softening of α phase and κ phase is minimized, α phase grain growth hardly occurs, and higher strength is obtained. be able to. In addition, the κ1 phase that contributes to strength and machinability is most abundant in heat treatment at 515 ° C. or more and 545 ° C. or less.
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 620 ° C., it is a problem as described above. However, once the temperature of the material is raised to 525 ° C. or higher and 620 ° 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 of passing through the temperature region of 525 ° C. or higher and 575 ° C. or lower in the cooling after holding is 20 minutes or more, thereby improving the metal structure. It becomes possible. In the case of a continuous furnace, since the time for which the maximum temperature is reached is short, the cooling rate in the temperature range from 575 ° C. to 525 ° C. is preferably 0.1 ° C./min to 2.5 ° C./min. More preferably, it is 2 degrees C / min or less, More preferably, it is 1.5 degrees 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 temperature range from 545 ° C to 525 ° C may be maintained for at least 20 minutes. If the temperature reaches 545 ° C., which is the highest temperature, and the holding time is 0 minute, the temperature range from 545 ° C. to 525 ° C. may be passed under the condition that the average cooling rate is 1 ° C./min or less. That is, if the temperature is kept at 525 ° C. or higher for 20 minutes or longer, the maximum temperature is not a problem as long as it is within the range of 525 ° C. to 620 ° C. 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. 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, although the upper limit of the cooling rate depends on the hot working temperature etc., 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 Increase in β phase and γ phase, which affect corrosion resistance and impact properties.

  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. 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 500 ° C./min or less, preferably 300 ° C./min or less in consideration of the influence of thermal strain.

(Cold working process)
In order to obtain high strength, to improve dimensional accuracy, or to make the extruded coil straight, cold work may be performed on the hot-worked material. For example, the hot-worked material is cold worked at a working 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. Or after hot working and then heat treatment, cold drawing and rolling at a working rate of about 2% to about 20%, preferably about 2% to about 15%, more preferably about 2% to about 10%. Processing is performed, and in some cases, a correction process is added. Depending on the dimensions of the final product, cold working and heat treatment may be repeated. In addition, the straightness of the bar may be improved only by the straightening equipment, or shot peening may be performed on 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.
An 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 application, properties emphasizing strength, emphasizing ductility and toughness 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. . That is, in the conventional free-cutting copper alloy that has been cold worked, the strength is greatly reduced by the recrystallization heat treatment, but the strength of the alloy of the present embodiment that has been cold worked is conversely increased and very high. Get strength. As described above, the cold-worked alloy of this embodiment and the conventional free-cutting copper alloy are completely different in behavior after heat treatment.
On the other hand, if cold working is performed at an appropriate cold working rate after the heat treatment, the ductility and impact properties are lowered, but the material is finished with higher strength, and the strength balance index f8 reaches 660 or more, or f9. Can reach 685 or more.
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 rods, forgings, and castings, the bar and forgings are sometimes annealed at a temperature below the recrystallization temperature for the main purpose of removing residual stress and correcting the rods. In the case of the alloy of the present embodiment, the elongation and the yield strength are improved while maintaining the tensile strength. 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 characteristics decrease. However, by performing low-temperature annealing, the precipitation of the μ phase is unavoidable, and the key is how to keep the precipitation of the μ phase to a minimum while removing the residual stress. Therefore, the value of the relational expression of (T−220) × (t) ^1/2 is important.
In addition, the lower limit of the value of (T−220) × (t) ^1/2 is 150, preferably 180 or more, and 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 in the case where the final product is a casting, after casting, the casting that has been cooled to room temperature is first subjected 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 505 ° C. or more and less than 525 ° C. for 100 minutes to 8 hours. Alternatively, the temperature of the material is raised to the maximum temperature of 525 ° C. or more and 620 ° C. or less, and then kept in a temperature range of 525 ° C. or more and 575 ° C. or less for 20 minutes or more. Alternatively, under a condition corresponding thereto, specifically, a temperature region of 525 ° C. or more and 575 ° C. or less is cooled at an average cooling rate of 0.1 ° C./min or more and 2.5 ° C./min or less.
Next, the metal structure can be improved by cooling the temperature range from 460 ° C. to 400 ° C. at an average cooling rate of 2.5 ° C./min to 500 ° C./min.
Note that the strength balance characteristics of f8 and f9 are not applied because the crystal grains of the casting are coarse and defects of the casting exist.

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 higher and 350 ° C. or lower, 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 505 ° 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 performing a low temperature annealing process after a hot working process and a heat treatment process (when a low temperature annealing process becomes the process of heating a copper alloy at the end), with the conditions of a low temperature annealing process, before a 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 a hot working process or a heat treatment process is performed after the low temperature annealing process, as described above, the subsequent process is important among the hot working process and the heat treatment process, and the above-described heating condition and cooling condition must be satisfied. 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 the semi-continuous casting machine used in actual operation. Table 2 shows the alloy composition. Since actual operating equipment was used, impurities in the alloys shown in Table 2 were also measured. The manufacturing process was performed under the conditions shown in Tables 5 to 11.

(Process No. A1-A14, AH1-AH14)
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, the extruded material was cooled at a cooling rate of 20 ° C./min in a temperature range of 575 ° C. to 525 ° C. and a temperature range of 460 ° C. to 400 ° C. by adjusting the temperature of the coil and adjusting the fan. Even in a temperature range of 400 ° C. or lower, cooling was performed at a cooling rate of about 20 ° 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 ± 5 ° C. of the temperature shown in Tables 5 and 6 ((temperature shown in Tables 5 and 6) −5 ° C. to (temperature shown in Tables 5 and 6) + 5 ° C.). I confirmed that there was.
Step No. For AH12, the extrusion temperature was 580 ° C. In steps other than step AH12, the extrusion temperature was 640 ° C. Process No. with an extrusion temperature of 580 ° C. In AH12, both of the two 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 A6 and AH3 to AH6, an extruded material having a diameter of 25.6 mm was cold drawn to a diameter of 25.0 mm. The drawn material is heated and held at a predetermined temperature and time in an actual electric furnace or laboratory electric furnace, and the average cooling rate in the temperature range of 575 ° C. to 525 ° C. in the cooling process, or 460 ° C. to 400 ° C. The average cooling rate in the temperature region was changed.
Step No. In A7 to A9 and AH7 to AH11, an extruded material having a diameter of 25.6 mm was cold drawn to a diameter of 25.0 mm. The drawn material is heat-treated in an electric furnace in a laboratory or a continuous furnace in a laboratory, and is cooled at a maximum temperature, a cooling rate in a temperature range of 575 ° C. to 525 ° C., or a temperature range of 460 ° C. to 400 ° C. The speed 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%, respectively, were applied, 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.
Step No. A13, process no. A14 and step No. AH13, process no. AH14 changed the cooling rate after hot extrusion, and changed 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. during the cooling process.
Regarding the heat treatment conditions, as shown in Tables 5 and 6, the heat treatment temperature was changed from 495 ° C. to 635 ° C., and the holding time was changed from 5 minutes to 180 minutes.
In the table below, 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 “?”.

(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 8.
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.

(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-like 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 centering 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. ((temperature shown in Table 9) −5 ° C. to (temperature shown in Table 9) + 5 ° C.) of the temperature shown in Table 9. The cooling rates from 575 ° C. to 525 ° C. and the cooling rates from 460 ° C. to 400 ° C. after extrusion were 15 ° 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 60 minutes, and then the cooling rate from 460 ° C. to 400 ° C. was set to 12 ° C./min. Step No. C0, process no. C1 was also used in part as a wear test material.

(Process No. D1-D8, DH1-DH5)
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 passed 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 10 ((temperature shown in Table 10) −5 ° C. to (temperature shown in Table 10) + 5 ° C.). It was confirmed.
Step No. In D1-D4, D8, DH2, and DH6, heat treatment is performed in an electric furnace in a laboratory, 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. For D8, after heat treatment, processing (compression) with a cold working rate of 1.0% was added.
Step No. In D5, D7, DH3, and DH4, heating was performed at 565 ° C. to 590 ° C. for 3 minutes in a continuous furnace, 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 copper alloy was conducted using laboratory equipment. Tables 3 and 4 show the alloy compositions. The balance is Zn and inevitable impurities. Copper alloys having the compositions shown in Table 2 were also used for laboratory experiments. The manufacturing process was performed under the conditions shown in Tables 12-15.

(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 from a melting furnace in actual operation into a mold having a diameter of 100 mm and a length of 180 mm. 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 12 after extrusion.
Step No. The extruded material obtained by EH1 and E1 was also used as an evaluation material for wear test and hot workability.

(Process No. F1-F5, FH1, FH2)
Step No. EH1 and process No. described later. A round bar having a diameter of 40 mm 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 13 ((temperature shown in Table 13) −5 ° C. to (temperature shown in Table 13) + 5 ° C.). It was confirmed.
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. were 20 ° 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. The heat treatment was performed while changing the heating conditions, 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 (process No. PH1) cast into a mold as a forging material. After hot forging, heat treatment (annealing) was performed by changing heating conditions and cooling rate.

(Process No. P1-P3, PH1-PH3)
Step No. In P1 to P3 and PH1 to PH3, a molten metal in which a raw material was melted at a predetermined component ratio was cast into a mold having an inner diameter of φ40 mm to obtain a casting. A part of the molten metal was cast into a metal mold having an inner diameter of 40 mm from a melting furnace that was actually operated to produce a casting. Step No. In processes other than PH1, heat treatment was performed on the casting by changing the heating conditions and the cooling rate.

(Process No. R1)
Step No. In R1, a part of the molten metal was cast into a 35 mm × 70 mm mold from the melting furnace actually operated. The surface of the casting was chamfered to a size of 30 mm × 65 mm. The casting was then heated to 780 ° C. and subjected to 3 passes of hot rolling to a thickness of 8 mm. After the completion of the final hot rolling, the material temperature after about 3 to about 4 seconds was 640 ° C., and then air-cooled. And the obtained rolled sheet was heat-processed with the electric furnace.

  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-field micrograph, each phase (α phase, κ phase, β phase, γ phase, μ phase) was manually painted using the 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 distinguish mainly 500 times, a 1000 times metal microscope photograph 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 micrograph or a 2000 × or 5000 × secondary electron image photo (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 long side length of the μ phase.
Specifically, evaluation was performed using photographs printed out to a size of about 70 mm × about 90 mm. When the magnification was 500 times, the size of the observation 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, 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, The metal structure was confirmed at a 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. 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 at the grain boundary of the α phase (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 T73 (alloy No. S02 / 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 T73 (alloy No. S02 / process No. A1) is shown. 2 and 3 are not identical. In copper alloys, there is a risk of being confused with twins present in the α phase, but the κ phase present in the α phase has a narrow width of the κ phase itself, and two twins form a pair. I 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 determination of a metal constituent phase (observation of metal structure) was used. The number of acicular 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 number of acicular κ phases in 5 fields was 10 or more and less than 50, it was determined that the needles had κ phases and was expressed as “Δ”. When the average value of the number of needle-like κ phases in five fields of view was 50 or more, it was judged that the needle-like κ phases had many needle-like κ phases and indicated as “◯”. When the average value of the number of needle-like κ phases in 5 fields was less than 10, 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.

(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. T03 (Alloy No. S01 / Process No. A1), Test No. T34 (Alloy No. S01 / Process No. BH3), Test No. T212 (Alloy No. S13 / Process No. FH1), Test No. About T213 (alloy No. S13 / process No. F1), the result of having performed the quantitative analysis of the density | concentration of Sn, Cu, Si, and P of each phase with an X-ray microanalyzer is shown in Table 16-Table 19.
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 alloy composition.
2) The distribution of Sn to the κ phase is about 1.4 times that of the α phase.
3) The Sn concentration of the γ phase is about 10 to about 15 times the Sn concentration of the α phase.
4) The Si concentrations of the κ phase, γ phase, and 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 the μ phase is about 3 times and about 4 times the P concentration of the α phase.
9) Even with the same composition, when the proportion of the γ phase decreases, the Sn concentration of the α phase increases from 0.12 mass% to 0.15 mass% by about 1.25 times (Alloy No. S13). Similarly, the Sn concentration of the κ phase increases about 0.1 times from 0.15 mass% to 0.21 mass%. Further, the increase in Sn in the κ phase exceeded the increase in Sn in the α phase.

(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, preferably 540N / mm ² or more, more preferably 570N / mm ² or more, and most long 590N / mm ² or more, the free-cutting copper alloy Among them, it is the highest level, and it is possible to reduce the thickness and weight of members used in each field or increase the allowable stress.
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-sectional 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, it is the highest level in a copper alloy. For example, it can be used as a highly reliable material in a valve used at a high temperature and an automobile part close to an engine room.
(Impact characteristics)
In the impact test, a U-notch test piece (notch depth 2 mm, notch bottom radius 1 mm) according to JIS Z 2242 was sampled from an extruded bar, a forged material and its substitute, a cast material, and a continuous cast bar. 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.
With respect to hot extruded rods having a diameter of 50 mm, 40 mm, or 25.6 mm, cold drawn materials having a diameter of 25 mm (24.5 mm), and castings, cutting was performed to prepare test materials with a diameter of 18 mm. 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 this embodiment, the cutting resistance was evaluated with 130N as a boundary (boundary value). Specifically, when the cutting resistance was 130 N or less, it was evaluated that the machinability was excellent (evaluation: ◯). If the cutting resistance was more than 130N and 150N or less, the machinability was evaluated as “possible (Δ)”. If the cutting resistance exceeded 150 N, it was evaluated as “impossible (×)”. Incidentally, for the 58 mass% Cu-42 mass% Zn alloy, the process No. When F1 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 cracking occurred in both conditions of 740 ° C. and 635 ° C., it was evaluated as “good” (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 cracking occurred at two conditions of 740 ° C. and 635 ° C. was evaluated as “x” (poor).
When cracking does not occur under two conditions of 740 ° C. and 635 ° C., regarding practical hot extrusion and hot forging, even if some material temperature drop occurs, 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 determined that hot working can be performed, but it is necessary to manage in a narrower temperature range due to practical restrictions. If cracking occurs at both temperatures of 740 ° C. and 635 ° C., it is judged that there is a large problem in practical use and is not possible.

(Caulking (bending) workability)
In order to evaluate the caulking (bending) workability, the outer circumferences of the bar and forging were cut to 13 mm, drilled with a drill having a diameter of 10 mm, and the length was cut to 10 mm. As described above, a cylindrical sample having an outer diameter of 13 mm, a thickness of 1.5 mm, and a length of 10 mm was produced. This sample was sandwiched between vise and flattened into an oval shape by human power, and the presence or absence of cracks was investigated.
The caulking rate (flatness) at the time of crack occurrence was calculated by the following formula.
(Caulking rate) = (1− (length of inner short side after flattening) / (inner diameter)) × 100 (%)
(Length of inner short side after flattening (mm)) = (Length of outer short side of flattened elliptical shape) − (thickness) × 2
(Inner diameter (mm)) = (outer diameter of cylinder) − (thickness) × 2
Note that, when force is applied to the cylindrical material to make it flat and unloading, it tries to return to its original shape by springback, but here, it refers to a permanently deformed shape.
Here, when the caulking rate (bending rate) when cracking occurred was 25% or more, the caulking (bending) workability was evaluated as “◯” (good). When the caulking rate (bending rate) was 10% or more and less than 25%, the caulking (bending) workability was evaluated as “Δ” (possible, fair). When the caulking rate (bending rate) was less than 10%, the caulking (bending) workability was evaluated as “×” (poor).
Incidentally, when a caulking test was conducted with a commercially available Pb-added free-cutting brass rod (59% Cu-3% Pb-residual Zn), the caulking rate was 9%. Alloys with excellent free machinability have some brittleness.

(Dezincification corrosion test 1, 2)
When the test material was an extruded material, the test material was embedded in the 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 cleaned 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 vision 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 the 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 to which a disinfectant serving as an oxidant is excessively administered, has a low pH and assumes a severe corrosive environment, 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. If the maximum corrosion depth is 70 μm or less, the corrosion resistance is good. When excellent corrosion resistance is required, it is estimated that the maximum corrosion depth is preferably 50 μm or less, more preferably 30 μm or less.
The test solution 2 is a solution for performing an accelerated test in a corrosive environment, assuming a 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 40 μm or less, the corrosion resistance is good. When excellent corrosion resistance is required, it is estimated that the maximum corrosion depth is preferably 30 μm or less, more preferably 20 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 amount of 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 20 was used as the test liquid 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.
Each sample was immersed in an aqueous solution (12.7 g / L) of 1.0% cupric chloride dihydrate (CuCl ₂ .2H ₂ O) and held at 75 ° C. for 24 hours. . 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, the corrosion depth was observed at 10 points of view of the microscope at a magnification of 100 times or 500 times. 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.

(Abrasion test)
Wear resistance was evaluated by two types of tests: an Amsler wear test under lubrication and a ball-on-disk friction wear test under dry process. The sample used was the process no. It is an alloy made of C0, C1, E1, EH1, FH1, and PH1.
An Amsler type abrasion test was carried out by the following method. Each sample was cut to a diameter of 32 mm at room temperature to prepare an upper test piece. Further, a lower test piece (surface hardness HV184) made of austenitic stainless steel (SUS304 of JIS G 4303) having a diameter of 42 mm was prepared. 490N was added as a load, and the upper test piece and the lower test piece were brought into contact with each other. Silicon oil was used for the oil droplets and the oil bath. With the load applied and the upper test piece and the lower test piece in contact, the upper test piece has a rotation speed (rotation speed) of 188 rpm, and the lower test piece has a rotation speed (rotation speed) of 209 rpm. The upper test piece and the lower test piece were rotated. The sliding speed was set to 0.2 m / sec due to the peripheral speed difference between the upper test piece and the lower test piece. The test piece was worn by the difference in the diameter and the number of rotations (rotational speed) between the upper test piece and the lower test piece. The upper test piece and the lower test piece were rotated until the number of rotations of the lower test piece reached 250,000 times.
After the test, the change in the weight of the upper test piece was measured, and the wear resistance was evaluated according to the following criteria. The case where the weight reduction of the upper test piece due to abrasion was 0.25 g or less was evaluated as “excellent”. The case where the weight reduction amount of the upper test piece was more than 0.25 g and 0.5 g or less was evaluated as “◯” (good). The case where the weight reduction amount of the upper test piece was more than 0.5 g and 1.0 g or less was evaluated as “Δ” (fair). The case where the weight reduction amount of the upper test piece exceeded 1.0 g was evaluated as “x” (poor). The wear resistance was evaluated at these four levels. In addition, in the lower test piece, when there was a weight loss of 0.025 g or more, it was evaluated as “x”.
Incidentally, the wear loss of the free-cutting brass containing 59Cu-3Pb-38Zn Pb under the same test conditions was 12 g.

A ball-on-disk friction and wear test was performed by the following method. The surface of the test piece was polished with sandpaper having a roughness of # 2000. On this test piece, a steel ball having a diameter of 10 mm made of austenitic stainless steel (SUS304 of JIS G 4303) was slid in a pressed state under the following conditions.
(conditions)
Room temperature, no lubrication, load: 49 N, sliding diameter: diameter 10 mm, sliding speed: 0.1 m / sec, sliding distance: 120 m.
After the test, the change in the weight of the test piece was measured, and the wear resistance was evaluated according to the following criteria. A case where the weight loss of the test piece due to abrasion was 4 mg or less was evaluated as “Excellent”. The case where the decrease in the weight of the test piece exceeded 4 mg and was 8 mg or less was evaluated as “◯” (good). A case where the decrease in the weight of the test piece was more than 8 mg and 20 mg or less was evaluated as “Δ” (fair). The case where the weight loss of the test piece exceeded 20 mg was evaluated as “x” (poor). The wear resistance was evaluated at these four levels.
Incidentally, the wear loss of the free-cutting brass containing 59Cu-3Pb-38Zn Pb under the same test conditions was 80 mg.

The evaluation results are shown in Table 21 to Table 61.
Test No. T01 to T66, T71 to T119, and T121 to T180 are results corresponding to the examples in the actual operation experiment. Test No. T201-T236, No. T240 to T245 are the results corresponding to the examples in the laboratory experiment. Test No. T501 to T534 are results corresponding to comparative examples in laboratory experiments.
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, satisfying the compositional relational expressions f1, f2, and f7, the requirements of the metal structure, and the structural relational expressions f3, f4, f5, and f6. Has machinability, good hot workability, excellent corrosion resistance in harsh environments, high strength, good ductility, impact properties, bending workability, wear resistance, high temperature properties It was confirmed that a hot extruded material, a hot forged material, and a hot rolled material to be combined were obtained (for example, alloys No. S01, S02, S13, process Nos. A1, C1, D1, E1, F1, F4, R1).
2) When Sb and As were contained, it was confirmed that the corrosion resistance under more severe conditions was improved (alloy Nos. S30 to S32).
3) It was confirmed that the cutting resistance was further reduced when Bi was contained (Alloy No. S32).
4) It was confirmed that the corrosion resistance, machinability and strength were improved by containing Sn in the κ phase at 0.11 mass% or more and P at 0.07 mass% or more (for example, alloys No. S01, S02). , S13).
5) The presence of an elongated needle-like κ phase in the α phase, that is, the κ1 phase, increases the strength, increases the strength / ductility balance f8 and the strength / ductility / impact balance f9, and maintains good machinability. It has been confirmed that the corrosion resistance, wear resistance, and high temperature characteristics are improved (for example, alloy Nos. S01, S02, and S03).

6) When the Cu content was low, the γ phase increased and machinability was good, but the corrosion resistance, ductility, impact properties, bending workability, and high temperature properties were poor. Conversely, when the Cu content is large, the machinability deteriorated. In addition, ductility, impact characteristics, and bending workability also deteriorated (Alloy Nos. S103, S104, S116, etc.).
7) When the Sn content is more than 0.28 mass%, the area ratio of the γ phase is more than 1.0% and the machinability is good, but the corrosion resistance, ductility, impact properties, bending workability, high temperature The characteristics deteriorated (Alloy No. S112). On the other hand, when the Sn content was less than 0.10 mass%, the dezincification corrosion depth in a harsh environment was large (alloy No. S115). The characteristics were further improved when the Sn content was 0.12 mass% or more (Alloy Nos. S01 and S114).
8) When the P content is large, impact properties, ductility, and bending workability deteriorated. The cutting resistance was a little high. On the other hand, when the P content was small, the dezincification corrosion depth was severe under harsh environments (Alloy Nos. S108, S111, S115).
9) It has been confirmed that the inclusion of inevitable impurities to the extent that is carried out in actual operation does not significantly affect various properties (Alloy Nos. S01, S02, S03). Although the composition is in the vicinity of the boundary value of the present embodiment, it is considered that an Fe intermetallic compound of Fe and Si or an intermetallic compound of Fe and P is formed when Fe exceeding the preferable range of inevitable impurities is contained. As a result, the effective Si concentration and P concentration decreased, the corrosion resistance was slightly deteriorated, the tensile strength was slightly decreased, and the machinability was slightly decreased in combination with the formation of intermetallic compounds (alloy No. 1). S113, S119, S120).
10) When the Pb content is low, the machinability is deteriorated, and when the Pb content is high, the high temperature characteristics, tensile strength, elongation, impact characteristics, and bending workability are slightly deteriorated (alloy No. S110, S121).

11) When the value of the compositional relational expression f1 is low, even when Cu, Si, Sn, and P are within the composition range, the dezincification corrosion depth in a harsh environment is large (alloy No. S102).
When the value of the compositional relational expression f1 was low, the γ phase increased and the machinability was good, but the corrosion resistance, ductility, impact characteristics, and high temperature characteristics were deteriorated. When the value of the composition relational expression f1 is high, the κ phase increases and the μ phase may appear, and the machinability, hot workability, ductility, and impact characteristics deteriorated (Alloy Nos. S104, S112, S114, S116).
12) If the value of the compositional relational expression f2 is low, a β phase may appear depending on the composition and the machinability was good, but the hot workability, corrosion resistance, ductility, impact properties, and high temperature properties are poor. became. When the value of the compositional relational expression f2 is high, the hot workability is deteriorated, and even if a predetermined amount of Si is contained, the amount of κ1 phase may be small or may not exist, and the tensile strength is low. The machinability deteriorated. When f2 is high, a coarse α phase appears, and it is assumed that machinability, tensile strength, and hot workability are deteriorated (Alloy Nos. S104, S118, and S107).

13) In the metal structure, when the ratio of the γ phase is more than 1.0% or the long side of the γ phase is longer than 40 μm, the machinability was good, but the strength was low and the corrosion resistance was high. , Ductility, impact properties, high temperature properties deteriorated. In particular, when the γ phase is large, selective corrosion of the γ phase occurred in a dezincification corrosion test under a severe environment (Alloy Nos. S101 and S102). When the proportion of the γ phase is 0.5% or less and the length of the long side of the γ phase is 30 μm or less, the corrosion resistance, impact characteristics, room temperature and high temperature strength are improved (Alloy Nos. S01 and S11). .
When the area ratio of the μ phase is more than 2%, or when the length of the long side of the μ phase exceeds 25 μm, the corrosion resistance, ductility, impact characteristics, and high temperature characteristics deteriorated. In the dezincification corrosion test under harsh environment, intergranular corrosion and μ phase selective corrosion occurred (Alloy No. S01, Process No. AH4, BH3, DH2). When the proportion of the μ phase is 1% or less and the length of the long side of the μ phase is 15 μm or less, the corrosion resistance, ductility, impact properties, room temperature and high temperature properties are improved (Alloy Nos. S01 and S11). .
When the area ratio of the κ phase was more than 67%, the machinability, ductility, bending workability, and impact characteristics deteriorated. On the other hand, when the area ratio of the κ phase is less than 28%, the machinability is poor, and when the κ phase exceeds about 50%, the machinability starts to deteriorate (alloy Nos. S116 and S101).

14) Corrosion resistance, ductility, impact properties, bending when the structural relational expression f5 = (γ) + (μ) exceeds 2.0%, or when f3 = (α) + (κ) is smaller than 97.4% Workability, room temperature and high temperature characteristics deteriorated. When the structure relational expression f5 is 1.2% or less, the corrosion resistance, ductility, impact characteristics, normal temperature and high temperature characteristics are improved (alloy No. S01, process No. AH2, FH1, A1, F1).
When the structure relational expression f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) is larger than 70, or when f6 is smaller than 30, the machinability was poor (alloy Nos. S101 and S105). ). When f6 was 30 or more and 58 or less, the machinability was further improved (Alloy Nos. S01 and S11). In addition, in alloys having the same composition and manufactured by different processes, there are many γ phases, and even though the value of f6 is high, the κ1 phase is not present or the amount of κ1 phase is small. The cutting resistance was almost equivalent (Alloy No. S01, Process No. A1, AH5 to AH7, AH9 to AH11).
When the area ratio of the γ phase exceeded 1.0%, the cutting resistance was low and the shape of the chips was good regardless of the value of the structural relational expression f6 (alloy Nos. S106, S118, etc.).

15) When the amount of Sn contained in the κ phase was lower than 0.11 mass%, the dezincification corrosion depth in a harsh environment was large, and the κ phase was corroded. In addition, the cutting resistance was slightly high, and some chips had poor chip breaking properties (Alloy Nos. S115 and S120). When the amount of Sn contained in the κ phase was higher than 0.14 mass%, the corrosion resistance and machinability were improved (alloy Nos. S20 and S21).
16) When the amount of P contained in the κ phase is lower than 0.07 mass%, the dezincification corrosion depth in a harsh environment is large and the κ phase is corroded (Alloy Nos. S108 and S115).
17) When the area ratio of the γ phase was 1.0% or less, the Sn concentration and the P concentration contained in the κ phase were higher than the amounts of Sn and P contained in the alloy. Conversely, when the area ratio of the γ phase was large, the Sn concentration contained in the κ phase was lower than the amount of Sn contained in the alloy. In particular, when the area ratio of the γ phase was about 10%, the Sn concentration contained in the κ phase was about half of the amount of Sn contained in the alloy (alloy Nos. S02, S14, S104, S118). ). Also, for example, Alloy No. S13, Process No. In FH1 and F1, when the area ratio of the γ phase decreases from 3.1% to 0.1%, the Sn concentration of the α phase increases by 0.03 mass% from 0.12 mass% to 0.15 mass%, and the κ phase The Sn concentration increased by 0.06 mass% from 0.15 mass% to 0.21 mass%. Thus, the increase in Sn in the κ phase exceeded the increase in Sn in the α phase. Although the cutting resistance increased by 5N due to the decrease in the γ phase, the increase in the distribution of Sn to the κ phase, and the presence of many acicular κ phases in the α phase, good machinability was maintained, By strengthening the corrosion resistance of the κ phase, the dezincification depth is reduced to about 1/4, the impact value is increased by about 1.4 times, the high temperature creep is reduced to 1/3, and the tensile strength is about 30 N / mm. ^The strength balance index f8 and f9 increased by 70 and 80, respectively.
18) If all the requirements for the composition and the metal structure are satisfied, the tensile strength is 540 N / mm ² or more, and a load corresponding to 0.2% proof stress at room temperature is applied and held at 150 ° C. for 100 hours. The creep strain at that time was 0.3% or less (Alloy No. S03).
In relation to tensile strength and hardness, alloy no. Using the steps S01, S02, S03, S22 and S101, the process No. The alloy manufactured by the F1, tensile ^strength relative to ^{574N / mm 2, 602N / mm} 2, 586N / mm 2, 562N / mm 2, 523N / mm 2, hardness HRB each, 77,84,80 74, 66.
19) The U-notch 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. In a hot extruded material or forged material that has not been cold worked, the Charpy impact test value of the U notch was 14 J / cm ² or more. And f8 exceeded 660 and f9 exceeded 685 (alloy Nos. S01, S02, S03).
When the Si amount is about 3.05% or more, the needle-like κ1 phase clearly starts to exist in the α phase, and when the Si amount is about 3.12%, the κ1 phase greatly increases. The relational expression f2 affected the amount of κ1 phase (alloy Nos. S22, S12, S107, S115, etc.).
When the amount of the κ1 phase is increased, good machinability is ensured even if the γ phase is 1.0% or less and the Pb content is less than 0.020, and the tensile strength, high temperature characteristics, and wear resistance are good. became. It is presumed that it leads to strengthening of the α phase and chip breaking (alloy Nos. S02, S03, S11, S16, etc.).
According to the test method of ISO 6509, an alloy containing about 1% or more of the β phase or about 5% or more of the γ phase, or containing no P or 0.02% is rejected (evaluation: Δ, × )Met. However, an alloy containing 3 to 5% of γ phase and an alloy containing about 3% of μ phase passed (evaluation: ◯). The corrosive environment employed in the present embodiment is a proof that a severe environment is assumed (alloy Nos. S103, S104, S120).
The wear resistance of the alloy containing many κ1 phases, containing Sn, and containing about 0.1 to about 0.7% of γ phase was excellent both under lubrication and under no lubrication (alloy No. S14, S18 etc.).

20) In the evaluation of the material using the mass production equipment and the material produced in the laboratory, almost the same result was obtained (alloy No, S01, S02, process No. C1, E1, F1).
21) Manufacturing conditions:
Hold a hot extruded material, extruded / drawn material, hot forged product, hot rolled material in a temperature range of 525 ° C. or higher and 575 ° C. or lower for 20 minutes or more, or a temperature of 505 ° C. or higher and lower than 525 ° C. At a cooling rate of 2.5 ° C./min or less in a temperature range of 525 ° C. or more and 575 ° C. or less, and then a temperature range of 460 ° C. to 400 ° C. When cooled at a cooling rate of 2.5 ° C./min or more, the κ1 phase is present, the γ phase is greatly reduced, and the μ phase is hardly present. Corrosion resistance, ductility, high temperature characteristics, impact characteristics, cold workability, A material with excellent mechanical strength was obtained.
In the process of heat-treating hot-worked materials and cold-worked materials, if the heat treatment temperature is low, the decrease in γ phase is small, and corrosion resistance, impact properties, ductility, cold workability, high-temperature properties, strength / ductility / impact The balance was bad. When the heat treatment temperature is high, the α phase crystal grains become coarse, the κ1 phase is small, the γ phase is less decreased, the corrosion resistance and impact properties are poor, the machinability is inferior, and the tensile strength is low (Alloy No. S01, S02, S03, step No. A1, AH5, AH6). Moreover, when the temperature of heat processing was 505 degreeC-525 degreeC, when holding time was short, there was little decrease of the (gamma) phase (process No. A5, AH9, D4, DH6, PH3).
When the cooling rate after the heat treatment was slow in the temperature range from 460 ° C. to 400 ° C., the μ phase was present, the corrosion resistance, impact properties, ductility, high temperature properties were poor, and the tensile strength was low (Step No. 4). A1-A4, AH8, DH2, DH3).
As a heat treatment method, good corrosion resistance, impact characteristics, and high temperature characteristics were obtained by once raising the temperature to 525 ° C. to 620 ° C. and slowing the cooling rate in the temperature range from 575 ° C. to 525 ° C. during the cooling process. . It was confirmed that the characteristics were improved even by the continuous heat treatment method. The amount of γ phase and the amount of κ1 phase were slightly affected by the cooling rate (Steps A7 to A9, D5, D7).
By controlling the cooling rate in the temperature range of 575 ° C. to 525 ° C. to 1.6 ° C./min after the hot forging and cooling after the hot extrusion, the proportion of the γ phase after the hot forging is A few forged products were obtained (Process No. D6).
Even when a casting was used as the hot forging material, good characteristics were obtained as with the extruded material. When an appropriate heat treatment was applied to the casting, the corrosion resistance was good (alloy Nos. S01, S02, S03, process Nos. F4, F5, P1 to P3).
By appropriate heat treatment and appropriate cooling conditions after hot forging, the amount of Sn and P contained in the κ phase increased (alloy Nos. S01, S02, S03, process Nos. A1, AH1, C0, C1). , D6).
When the amount of Sn contained in the κ phase increases, the γ phase is greatly reduced, but it has been confirmed that good machinability can be secured (alloy Nos. S01, S02, process Nos. AH1, A1). , D7, C0, C1, EH1, E1, FH1, F1).
When the needle-like κ phase is present in the α phase, it is presumed that the tensile strength and wear resistance are improved, the machinability is good, and a large decrease in the γ phase is compensated (alloy No. 1). S01, S02, S03, process No. AH1, A1, D7, C0, C1, EH1, E1, FH1, F1).
When the extruded material is cold worked at a processing rate of about 5% and about 8%, and then subjected to a predetermined heat treatment, the corrosion resistance, impact properties, cold workability, high temperature properties, The tensile strength was improved, and in particular, the tensile strength was increased by about 60 N / mm ² and about 80 N / mm ² . Strength, ductility, and impact balance index were also improved by about 70 to about 100 (Alloy Nos. S01, S03, Process Nos. AH1, A1, A12).
When the heat-treated material is processed at a cold working rate of 5%, the tensile strength is increased by about 90 N / mm ² compared to the extruded material, the strength / ductility balance index is improved by about 100, and the corrosion resistance and high temperature characteristics are also improved. . When the cold working rate is about 8%, the tensile strength is increased by about 120 N / mm ² and the strength / ductility / impact balance index is also improved by about 120 (Alloy No. S01, S03, Process No. AH1, A10, A11).
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 step S01 to S03, the process No. In the sample to which AH12 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 an alloy which is a comparative example of this embodiment, a copper alloy Cu—Zn—Si alloy casting (test No. T601 / alloy No. S201) 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 T601 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 T601 (test No. T602 / alloy No. S202). A similar alloy casting (Test No. T602) was subjected to the composition described in Example 1, analysis of metal structure, evaluation (measurement) of mechanical properties, and dezincification corrosion tests 1 to 3. And test no. Corrosion state by actual water environment of T601 and test No. The validity of the accelerated test of the dezincification corrosion tests 1 to 3 was verified by comparing the corrosion state by the accelerated test of the dezincification corrosion tests 1 to 3 of T602.
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. T10 / Alloy No. S01 / Process No. A6) and Test No. Corrosion state of T601 and test No. Comparison with the evaluation result (corrosion state) of the dezincification corrosion test 1 of T602, The corrosion resistance of T10 was considered.

Test No. T602 was manufactured by the following method.
Test No. The raw material was melted so as to have almost the same composition as T601 (alloy No. S201), and cast into a mold having a casting temperature of 1000 ° C. and an inner diameter of φ40 mm to produce a casting. The casting was then cooled in the temperature range from 575 ° C. to 525 ° C. at a cooling rate of about 20 ° C./min, and then in the temperature range from 460 ° C. to 400 ° C. at an average cooling rate of about 15 ° C./min. . As described above, test no. A sample of T602 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 62 to 64 and FIGS.

In a copper alloy casting (test No. T601) 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 T601 is shown.
Test No. T601 was used in a harsh water environment for 8 years, and 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 depth of the α phase and κ phase is not constant, but has irregularities, but roughly from the boundary to the inside, the γ phase preferentially occurred (the α phase and κ phase 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 T602 is shown.
The maximum corrosion depth was 143 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).
A healthy α phase was present in the interior.
The corrosion depth of the α phase and κ phase is not constant, but has irregularities, but roughly from the boundary to the inside, the γ phase preferentially occurred (the α phase and κ phase 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 T601 is the test no. It was slightly shallower than the maximum corrosion depth in the dezincification corrosion test 1 of T602. However, test no. The maximum corrosion depth of T601 is the test no. It was slightly deeper than the maximum corrosion depth in the dezincification corrosion test 2 of T602. 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 T602 dezincification corrosion test 3 (ISO 6509 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 results due to harsh water environment for 8 years of T601, Test No. In the corrosion results of the dezincification corrosion test 1 and 2 of T602, 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 T10 (alloy No. S01 / process No. A6) is shown.
Near the surface, about 30% of the kappa phase exposed on the surface was corroded. However, the remaining kappa and alpha phases were healthy (not corroded). The maximum corrosion depth was about 25 μm. Further, inward, selective corrosion of the γ phase or the μ phase occurred at a depth of about 20 μm. The length of the long side of the γ phase or μ phase is considered to be one of the major factors that determine the corrosion depth.
Test No. 1 in FIGS. Compared to T601 and T602, the test No. of this embodiment in FIG. It can be seen that at T10, corrosion of the α phase and κ phase near the surface is greatly suppressed. This is presumed to delay the progress of corrosion. From the observation results of the corrosion form, it is considered that the corrosion resistance of the κ phase is enhanced by the fact that the κ phase contains Sn as a main factor that the corrosion of the α phase and κ phase near the surface is greatly suppressed.

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. It is suitable for a member, a device that comes into contact with a liquid, a part, a valve that comes into contact with hydrogen, a joint, a tool, or a part.
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, valve stem, union, flange, branch plug, faucet valve, ball valve, various valves, piping joints such as elbow, socket , Cheese, bend, connector, adapter, tee, joint, etc.
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.

Claims (12)

75.4 mass% to 78.7 mass% Cu, 3.05 mass% to 3.65 mass% Si, 0.10 mass% to 0.28 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 total amount of the inevitable impurities Fe, Mn, Co, and Cr is less than 0.08 mass%,
When the Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, and the P content is [P] mass%,
76.5 ≦ f1 = [Cu] + 0.8 × [Si] −8.5 × [Sn] + [P] ≦ 80.3,
60.7 ≦ f2 = [Cu] −4.6 × [Si] −0.7 × [Sn] − [P] ≦ 62.1,
0.25 ≦ f7 = [P] / [Sn] ≦ 1.0
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)%,
28 ≦ (κ) ≦ 67,
0 ≦ (γ) ≦ 1.0,
0 ≦ (β) ≦ 0.2,
0 ≦ (μ) ≦ 1.5,
97.4 ≦ f3 = (α) + (κ),
99.4 ≦ f4 = (α) + (κ) + (γ) + (μ),
0 ≦ f5 = (γ) + (μ) ≦ 2.0,
30 ≦ f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 70,
And having a relationship
Free cutting property characterized in that the length of the long side of the γ phase is 40 μm or less, the length of the long side of the μ phase is 25 μm or less, and a needle-like κ phase exists in the α phase. Copper alloy.   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 0.005 mass% or more and 0.20 mass% or less The free-cutting copper alloy according to claim 1. 75.6 mass% or more and 77.9 mass% or less of Cu, 3.12 mass% or more and 3.45 mass% or less of Si, Sn of 0.12 mass% or more and 0.27 mass% or less of Sn, and 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%,
When the Cu content is [Cu] mass%, the Si content is [Si] mass%, the Sn content is [Sn] mass%, and the P content is [P] mass%,
76.8 ≦ f1 = [Cu] + 0.8 × [Si] −8.5 × [Sn] + [P] ≦ 79.3
60.8 ≦ f2 = [Cu] −4.6 × [Si] −0.7 × [Sn] − [P] ≦ 61.9,
0.28 ≦ f7 = [P] / [Sn] ≦ 0.84
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) ≦ 56,
0 ≦ (γ) ≦ 0.5,
(Β) = 0,
0 ≦ (μ) ≦ 1.0,
98.5 ≦ f3 = (α) + (κ),
99.6 ≦ f4 = (α) + (κ) + (γ) + (μ),
0 ≦ f5 = (γ) + (μ) ≦ 1.2,
30 ≦ f6 = (κ) + 6 × (γ) ^1/2 + 0.5 × (μ) ≦ 58,
And having a relationship
Free cutting property characterized in that the length of the long side of the γ phase is 25 μm or less, the length of the long side of the μ phase is 15 μm or less, and the needle-like κ phase exists in the α phase. Copper alloy.   Furthermore, it contains one or more selected from Sb of 0.012 mass% to 0.07 mass%, As of 0.025 mass% to 0.07 mass%, and Bi of 0.006 mass% to 0.10 mass%. The free-cutting copper alloy according to claim 3. The amount of Sn contained in the κ phase is 0.11 mass% to 0.40 mass%, and the amount of P contained in the κ phase is 0.07 mass% to 0.22 mass%. The free-cutting copper alloy according to any one of claims 1 to 4 . Creep after holding for 100 hours at 150 ° C. with a U-notch-shaped Charpy impact test value of 12 J / cm ² or more and less than 50 J / cm ² and a load corresponding to 0.2% proof stress 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. A hot working material, the tensile strength S (N / mm ²⁾ is 540N / mm ² or more, elongation E (%) is 12% or more, U notch shape of the Charpy impact test value I (J / cm ²⁾ is 12J / cm ² or more and 660 ≦ f8 = S × {(E + 100) / 100} ^1/2 or 685 ≦ f9 = S × {(E + 100) / 100} ^1/2 + I The free-cutting copper alloy according to any one of claims 1 to 5 . It is used for water supply equipment, industrial piping members, equipment in contact with liquids, pressure vessels / joints, automotive parts, or electrical product parts, according to any one of claims 1 to 7. Free-cutting copper alloy. 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 heated and cooled 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 505 ° 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 620 ° C. or less and is kept 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 step, and an annealing step performed after the casting step,
In the annealing step, the copper alloy is heated and cooled 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 505 ° 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 620 ° C. or less and is kept 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 ,
Including hot working process,
The material temperature when hot-working 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