JP5794906B2 - Copper alloy material with excellent machinability - Google Patents

Description

  The present invention relates to a copper alloy material suitable for metal parts used in electronic equipment, precision machines, etc., particularly copper alloy parts produced by cutting, and a method for producing the same.

  Cutting methods such as turning and drilling are methods for producing metal parts. Cutting is an effective processing method particularly for manufacturing parts having complicated shapes and parts requiring high dimensional accuracy. When cutting, machinability often becomes a problem. The machinability includes items such as cutting waste treatment, tool life, cutting resistance, and cutting surface roughness, and the material has been improved to improve them.

  Copper alloys are used in many metal parts for reasons such as high strength, excellent electrical conductivity and thermal conductivity, excellent corrosion resistance, and excellent color tone. There are also many cutting processes, such as taps, valves, gears, ornaments, etc., brass (Cu-Zn), bronze (Cu-Sn), aluminum bronze (Cu-Al). ), Alloys in which lead is added to white (Cu—Zn—Ni system) to improve machinability are used (Patent Documents 1 to 4).

In order to improve the machinability of the copper alloy material as described above, lead is generally added. This is because lead does not dissolve in the copper alloy, so it is finely dispersed in the material, and the cutting waste is easily divided at that portion during cutting. However, the use of lead is being restricted because it is believed to affect the human body and the environment, and there is an increasing demand for materials that have improved machinability without containing lead. As an alternative material for a copper alloy containing lead, a copper alloy obtained by adding bismuth to brass or bronze (Patent Documents 5 and 6) is known.
In brass, by increasing the amount of zinc, a β-phase γ phase that is a copper-zinc compound is formed, or silicon is added to form a κ phase that is a copper-zinc-silicon compound, and these Machinability is improved by causing a compound to act as a starting point for cutting waste cutting (Patent Document 7). Among the copper-zinc-based compounds that are formed by improving the amount of zinc, as a technique for forming a γ phase in particular, a technique for forming three phases of α, β, and γ by adding Sn is known ( Patent Documents 8 to 11).

JP 60-056036 A JP 58-113336 A JP 51-101716 A Japanese Patent Laid-Open No. 01-177327 JP 2001-059123 A JP 2000-336442 A JP 2004-183056 A JP 2000-319737 A JP-A-11-131159 JP 2002-12928 A Japanese Patent No. 3303301 JP 2001-11551 A

However, the technique described in each patent document has the following problems.
In each technique of Patent Literatures 1 to 4, as described above, lead is used as an additive element for improving machinability, and there is a concern about the burden on the environment. In addition, in the techniques of Patent Documents 5 and 6, machinability is improved when bismuth is added, but cracking is likely to occur during processing, and particularly hot processing becomes difficult. That is, it is necessary to improve the hot workability.
In Patent Document 7, the κ phase of a copper-zinc-silicon compound improves machinability, but deteriorates hot workability and cold workability, and is difficult to process into a plate shape or the like.
In Patent Documents 8 to 11, in a copper-zinc-tin alloy, machinability is improved by dispersion of β and γ phases. However, in order to ensure cold workability by coexistence with α phase, There is a demand for further improvement in machinability.

  As described above, in the invention of the copper alloy which is intended to improve the machinability, the machinability is not sufficient, which contains harmful elements, the machinability is still insufficient, and the extensibility is insufficient for processing into a plate shape or the like. There is a problem. Copper alloys that can be processed into plate shapes because metal parts for precision machinery such as gears and watch base plates are made by pressing and cutting from metal materials in the shape of plates. Material is required. Moreover, since it is manufactured by cutting from a small-diameter bar for use as an IC socket pin or the like, it needs to be processed into a small-diameter bar. However, since the compatibility between machinability and extensibility is inadequate, it is still the case that machined brass containing lead is still used, and it does not contain lead due to environmental and human effects. In addition, it is desired to develop a Cu—Zn plate having improved machinability and excellent extensibility.

  In view of such a problem, the present invention has been made, and while it is a copper alloy material excellent in machinability, it can be processed into a plate shape or a thin rod shape, and Cu- It is an object to provide a Zn alloy material.

  As a result of intensive studies, the present inventors have found that in a Cu-Zn alloy, the Zn content is improved, the structure in the alloy is a two-phase structure of a β phase and a γ phase, and the γ phase on the grain boundary of the β phase is β By controlling the ratio including the phase boundary, controlling the thickness of the γ phase on the β phase grain boundary, and controlling the dispersion of the γ phase in the β phase grain, Cu— excellent in machinability A Zn-based alloy was found.

That is, the present invention provides the following solutions.
(1) A copper alloy material containing Zn in an amount of 48 to 54 mass%, the balance being Cu and inevitable impurities, and the γ phase is formed on the grain boundary of the β phase so as to cover the periphery of the β phase. When the ratio of the γ phase included in the total grain boundary length of the β phase is evaluated by a cross section, the grain boundary inclusion rate is 60% or more, and the average value of the thickness of the γ phase is the average of the β phase. A copper alloy material excellent in machinability, wherein the ratio to the particle size is 0.5% or more and 10% or less.
(2) The γ phase is dispersed in the β phase grains, and the number density of the γ phases in the β phase grains is 250 / mm ² or more and less than 1000 / mm ² , The copper alloy material excellent in machinability as described in (1).
(3) The copper alloy material according to (1) or (2), wherein the shape is a plate material.
(4) including a treatment in which a heat treatment for making a β single phase is performed at 600 ° C. or more and 840 ° C. or less for 10 to 120 minutes, and then a heat treatment for dispersing the γ phase is performed at 300 ° C. or more and less than 600 ° C. for 10 to 600 minutes. The manufacturing method of the copper alloy material of any one of-(3).
(5) The heat treatment for forming a β single phase is performed at 600 ° C. or more and 840 ° C. or less for 10 to 120 minutes, and then the γ phase is formed so as to cover the grain boundaries of the β phase. Any one of (1) to (3), including a heat treatment to be performed and a heat treatment to be performed at 300 ° C. or more and less than 500 ° C. for 120 to 600 minutes to form a γ phase in the β phase grains in any order 2. A method for producing a copper alloy material according to item 1.
(6) A manufacturing process including a hot working step before heat treatment to make a β single phase, performing material heating before hot working at 600 ° C. or higher and 840 ° C. or lower, and finishing hot working at 470 ° C. or higher. (4) or the manufacturing method as described in (5).
(7) (6) including a manufacturing process in which the hot working is hot rolling, material heating before hot rolling is performed at 600 ° C. or higher and 840 ° C. or lower, and hot rolling is ended at 470 ° C. or higher. The manufacturing method as described.
(8) The manufacturing process in which the hot working is hot extrusion, material heating before hot extrusion is performed at 600 ° C. or higher and 840 ° C. or lower, and hot extrusion is finished at 470 ° C. or higher is included in (6). The manufacturing method as described.
(9) Including a hot working step, material heating before hot working is performed at 600 ° C. or higher and lower than 840 ° C., and hot working is finished at 600 ° C. or higher and rapidly cooled. The copper alloy material according to any one of (1) to (3), including a manufacturing process including a process of performing a heat treatment for dispersing the γ phase at a temperature of 300 ° C. or higher and lower than 600 ° C. for 10 to 600 minutes after forming the phase. Production method.
(10) Including a hot working step, material heating before hot working is performed at 600 ° C. or higher and lower than 840 ° C., and hot working is finished at 600 ° C. or higher and rapidly cooled. After forming the phase, heat treatment is performed at 500 ° C. or more and less than 600 ° C. for 10 to 120 minutes so that the γ phase is covered with the β phase grain boundary, and 300 ° C. or more and 500 ° C. is formed to form the γ phase in the β phase grains. The manufacturing method of the copper alloy material of any one of (1)-(3) including the process which implements the heat processing performed for 120 to 600 minutes below in arbitrary orders.
(11) The manufacturing method according to (9) or (10), wherein the hot working is hot rolling.
(12) The manufacturing method according to (9) or (10), wherein the hot working is hot extrusion.

FIG. 1 shows a schematic diagram of a material structure in the present invention. In addition, the γ phase “includes” the β phase grain boundary means a state in which the γ phase 2 covers the circumference of the β phase grain 1 as shown in FIG. The thickness of the γ phase refers to the width between arrows indicated by 4 in FIG. The dispersion of the γ phase in the β phase grains means a state in which the γ phase 3 is dispersed in the β phase grains in FIG.
Further, the position of the cross section for evaluating the grain boundary coverage is not particularly limited, but in the case of a plate material, a “surface for cutting” is preferable, and in the case of a bar material, a “surface perpendicular to the extrusion direction” is preferable. .

  The Cu—Zn copper alloy material of the present invention is excellent in machinability without using environmentally hazardous substances such as lead. The copper alloy material of the present invention is suitable as a material for parts such as precision parts manufactured by cutting.

It is sectional drawing which shows typically the structure | tissue of the copper alloy material of this invention.

  In the present invention, the copper alloy material does not limit the shape, thickness, or width, but includes a plate material, a bar material, and the like. A plate material is preferred.

  A preferred embodiment of the copper alloy material of the present invention will be described in detail. First, the effect of each alloy element and the range of its content will be described.

  In a preferred embodiment of the copper alloy material of the present invention, zinc (Zn) affects the formation of β phase and γ phase and improves machinability. In the present invention, it is necessary to make the range exhibit a β + γ two-phase structure, and is preferably 48 to 54 mass%. More preferably, it is 49-52 mass%. If the amount is too small, the γ phase is not formed. If the amount is too large, the amount of γ phase formed is too large, so that a suitable γ phase dispersion state cannot be obtained, and problems such as cracking occur during processing.

  Impurities other than Cu and Zn are allowed to be contained in trace amounts unless the level changes the phase of the Cu-Zn alloy.

Next, a preferred form of the metal structure that can improve machinability will be described. In order to improve the machinability with the β phase as the parent phase, a form in which the γ phase that is the starting point of the fragmentation is formed is necessary. The γ phase is not simply formed, and the γ phase needs to be formed on the grain boundary of the β phase so as to cover the periphery of the β phase. When the ratio of the γ phase included in the total grain boundary length of the β phase is defined by the following equation as the grain boundary coverage ratio, the range of the grain boundary coverage ratio f for a certain cross section is 60% to 100%. is there. If it is less than 60%, the chip breaking property is insufficient. Even if 100%, there is no problem with the chip breaking property, but when there is a β-phase grain boundary that is not covered by the γ phase, cracks are more likely to develop in the grains during the cutting process. It can be said that it will be good. From that viewpoint, a more preferable range is 80 to 95%.

Grain boundary inclusion rate f = total of γ phase length on β phase grain boundary / β phase grain boundary length × 100 (%)

As for the average value of the thickness of the γ phase on the grain boundary, the ratio of the β phase to the average crystal grain size determined by the following formula is preferably 0.5% or more and 10% or less. If it is less than 0.5%, the machinability may be insufficient. If it exceeds 10%, it becomes too brittle, so that chipping may occur during cutting and the product shape may not be obtained.

Average value of γ phase thickness on β phase grain boundary / β phase average crystal grain size x 100 (%)

Further, the machinability can be further improved by forming the γ phase in the grains of the β phase. It is preferable that the number density of γ phases in the β phase grains is 250 to 1000 / mm ² . A more preferable range is 400 to 1000 pieces / mm ² . When the number density is smaller than 250 pieces / mm ² , the machinability may be insufficient. When the number density exceeds 1000 pieces / mm ² , it becomes too brittle, so that chipping may occur during cutting and the product shape may not be obtained.

  As for the particle size of the γ phase in the β phase grains, the contribution to the machinability is not larger than the number density of the γ phase, and the particle size may be on the order of microns.

  The β phase preferably has a substantially recrystallized structure. The crystal grain size is preferably 30 to 500 μm. More preferably, it is 50-300 micrometers. In the present specification, the crystal grain size means an average crystal grain size measured based on the cutting method of JIS H 0501.

  Next, production conditions in a preferred embodiment of the present invention will be described. The manufacturing process of the copper alloy material of the present invention can be performed by processing an ingot of the above alloy composition manufactured by a conventional method in a manufacturing process including a series of processes of heat treatment after hot working. Since the above-described dispersed state of the γ phase determines machinability, it is necessary to control a series of steps from hot working to heat treatment.

  The ingot holding temperature before hot working is preferably 600 ° C. or higher and 840 ° C. or lower, more preferably 650 to 750 ° C. The holding time is 30 to 600 minutes, preferably 60 to 120 minutes. When the holding temperature is higher than 840 ° C., the Cu—Zn phase is dissolved and becomes a factor that breaks during hot working. When the temperature is lower than 600 ° C., the hot processing described later cannot be completed by 470 ° C. due to a temperature drop during the hot processing. If the holding time is shorter than 30 minutes, the cast structure cannot be homogenized. When it is carried out for more than 600 minutes, Zn may evaporate from the material surface and the material may become non-uniform.

  The hot working is preferably completed up to 470 ° C. If it is less than 470 degreeC, the regularity of a beta phase will increase, the workability of material may fall remarkably, and it may lead to a crack in hot processing.

  Regarding the hot working method, forging, extrusion, rolling and the like are not particularly selected, but a treatment for extending the material by hot rolling and hot extrusion is preferred.

  By adjusting the processing rate of hot working, it is possible to control the crystal grain size of the substantially recrystallized β phase. Specifically, the processing rate is preferably 5 to 40%.

  In order to control the form of the γ phase, it is necessary to perform heat treatment for forming the γ phase after the β phase is once changed. It is preferable that the heat treatment for forming a β single phase is performed at 600 ° C. or higher and 840 ° C. or lower after hot working. A more preferable temperature is 650 ° C. or higher and 750 ° C. or lower. The heat treatment time is preferably 10 to 120 minutes. More preferably, it is 30 to 60 minutes. If it is lower than 600 ° C., it cannot be a β single phase, and if it is higher than 840 ° C., a Cu—Zn phase is dissolved. When the treatment time is shorter than 10 minutes, the β single phase cannot be obtained, and when the treatment time exceeds 120 minutes, the β phase crystal grains are markedly coarsened. The β single phase means a state in which the γ phase does not exist in the grain boundaries and grains of the β phase. After the β single phase treatment, it is desirable to suppress the formation of the γ phase by setting the cooling rate to 10 ° C./min or more by rapid cooling by water cooling or air blowing. More preferably, it is 50 ° C./min or more.

  The β single phase may be performed simultaneously with hot working. When performing hot working and β single phase at the same time, complete the hot working up to 600 ° C, and after the β single phase treatment, the cooling rate is 10 ° C / min. It is desirable to cool down and suppress the formation of the γ phase. More preferably, it is 50 ° C./min or more.

  About dispersion | distribution of (gamma) phase, it can form in the above-mentioned form by heat processing for 10 to 600 minutes at 300 degreeC or more and less than 600 degreeC after (beta) single phase process. When the temperature is lower than 300 ° C. and 600 ° C. or higher, the formation of the γ phase is insufficient, the grain boundary coverage is low, and the γ phase density in the grains is also low.

  Regarding the dispersion of the γ phase, it is possible to strictly control the γ phase on the β grain boundaries and in the grains by performing a two-stage heat treatment. That is, the heat treatment for forming the γ phase so as to cover the grain boundaries of the β phase is performed at 500 ° C. or more and less than 600 ° C. for 10 to 120 minutes, and the heat treatment for forming the γ phase in the grains of the β phase is 300 ° C. or more and less than 500 ° C. When it is carried out for 120 to 600 minutes, a more preferable γ phase form is obtained. Either the process of forming the γ phase at the grain boundary of the β phase or the process of forming the γ phase in the grains of the β phase may be performed first. In this case, it is desirable that the high temperature treatment for promoting the formation on the grain boundaries is performed in a shorter time than the low temperature treatment for promoting the formation within the grains.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

Example 1
The inventive and comparative copper alloys having the compositions shown in Table 1 were melted in a high-frequency melting furnace and cast into a cast iron mold having a thickness of 30 mm, a width of 120 mm, and a length of 150 mm to obtain an ingot.

  In Invention Examples 1 to 3 and Comparative Example 1, the gate and bottom of the ingot obtained were cut and heated to 750 ° C., held at that temperature for 1 hour, and then hot rolled. The rolling rate of each pass was 10 to 25%, and the thickness was reduced to 6 mm in 8 passes. The hot rolling was finished up to 600 ° C. and then air-cooled to room temperature. Both sides were cut 1.5 mm each to remove the oxide film. Thereafter, heat treatment was performed at 680 ° C. for 30 minutes in an argon gas atmosphere, and water cooling was performed (cooling rate of 150 ° C./min or more). Subsequently, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Invention Example 4, the heat treatment up to 680 ° C. was the same as that in Invention Example 1, but the final heat treatment was performed at 500 ° C. for 60 minutes in an argon gas atmosphere and air-cooled to room temperature.

  In Invention Example 5, the heat treatment up to 680 ° C. was the same as that in Invention Example 1, but the final heat treatment was performed at 400 ° C. for 60 minutes in an argon gas atmosphere and air-cooled to room temperature.

  In Invention Example 6, the heat treatment up to 680 ° C. was the same as that in Invention Example 1, but the final heat treatment was performed at 300 ° C. for 600 minutes in an argon gas atmosphere and air-cooled to room temperature.

  In Invention Example 7, the heat treatment up to 680 ° C. was the same as that in Invention Example 2, but the final heat treatment was performed at 420 ° C. for 60 minutes in an argon gas atmosphere and air-cooled to room temperature.

  In Invention Example 8, the heat treatment up to 680 ° C. is the same as that in Invention Example 1, but after that, the heat treatment is performed at 550 ° C. for 30 minutes in an argon gas atmosphere and air-cooled to room temperature. Was carried out at 350 ° C. for 300 minutes and air-cooled to room temperature.

  In Invention Example 9, the heat treatment up to 680 ° C. is the same as that in Invention Example 1, but after that, the heat treatment is performed at 350 ° C. for 300 minutes in an argon gas atmosphere and air-cooled to room temperature. Was carried out at 570 ° C. for 20 minutes and air-cooled to room temperature.

  In Invention Example 10, the pouring gate and the bottom of the ingot obtained were cut, heated to 830 ° C. after cutting, held at that temperature for 1 hour, and then hot rolled. The rolling rate of each pass was 10 to 25%, and the thickness was reduced to 6 mm in 8 passes. Hot rolling was finished up to 780 ° C. and then air-cooled to room temperature. Both sides were cut 1.5 mm each to remove the oxide film. Thereafter, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Invention Example 11, the gate and bottom of the resulting ingot were cut and heated to 600 ° C., held at that temperature for 1 hour, and then hot rolled. The rolling rate of each pass was 10 to 25%, and the thickness was reduced to 6 mm in 8 passes. Hot rolling was finished up to 470 ° C. and then air-cooled to room temperature. Both sides were cut 1.5 mm each to remove the oxide film. Thereafter, heat treatment was performed at 680 ° C. for 30 minutes in an argon gas atmosphere, and water cooling was performed (cooling rate of 150 ° C./min or more). Subsequently, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Invention Example 12, the gate and bottom of the ingot obtained were cut and heated to 750 ° C., held at that temperature for 1 hour, and then hot rolled. The rolling rate of each pass was set to 10 to 25%, 7 passes were performed, and the final 8th rolling pass was performed at 33%. The hot rolling was finished up to 600 ° C., and then water cooling was performed promptly. Both sides were cut 1.5 mm each to remove the oxide film. Thereafter, heat treatment was performed at 680 ° C. for 30 minutes in an argon gas atmosphere, and water cooling was performed (cooling rate of 150 ° C./min or more). Subsequently, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Invention Example 13, the gate and bottom of the resulting ingot were cut and heated to 750 ° C., held at that temperature for 1 hour, and then hot rolled. The rolling rate of each pass was 10 to 25%, 6 passes were performed, and the final 7th pass and 8th pass were executed at 8% and 9%, respectively. The hot rolling was finished up to 600 ° C., and then water cooling was performed promptly. Both sides were cut 1.5 mm each to remove the oxide film. Thereafter, heat treatment was performed at 680 ° C. for 30 minutes in an argon gas atmosphere, and water cooling was performed (cooling rate of 150 ° C./min or more). Subsequently, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Comparative Example 2, the test was stopped because the material was crushed at the time of cutting the pouring gate and the bottom of the resulting ingot.

  In Comparative Example 3, the pouring gate and the bottom of the resulting ingot were cut and heated to 750 ° C., held at that temperature for 1 hour, and then hot rolled. The rolling rate of each pass was 10 to 25%, and the thickness was reduced to 6 mm in 8 passes. The hot rolling was finished up to 600 ° C. and then cooled to room temperature by air cooling. Both sides were cut 1.5 mm each to remove the oxide film. Thereafter, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Comparative Example 4, the heat treatment up to 680 ° C. was the same as that of Invention Example 1, but the final heat treatment was performed at 300 ° C. for 5 minutes in an argon gas atmosphere and air-cooled to room temperature.

  In Comparative Example 5, the heat treatment up to 680 ° C. was the same as that in Invention Example 1, but the final heat treatment was performed at 280 ° C. for 600 minutes in an argon gas atmosphere and air-cooled to room temperature.

  In Comparative Example 6, the pouring gate and the bottom of the obtained ingot were cut and heated to 750 ° C., held at that temperature for 1 hour, and then hot-rolled. The rolling rate of each pass was 10 to 25%, and the thickness was reduced to 6 mm in 8 passes. The hot rolling was finished up to 600 ° C. and then cooled to room temperature by air cooling. Both sides were cut 1.5 mm each to remove the oxide film. Thereafter, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Comparative Example 7, the sprue and bottom of the resulting ingot were cut and heated to 850 ° C., held at that temperature for 1 hour, and then hot-rolled to generate cracks during hot rolling. Therefore, the test was stopped.

  In Comparative Example 8, the gate and bottom of the ingot obtained were cut and heated to 550 ° C., held at that temperature for 1 hour, and then hot rolled. When the final pass was performed at 450 ° C., cracks occurred during hot rolling, so the test was stopped.

  The machinability of each of the copper alloy sheet samples thus obtained was examined. As machinability, the cutting property of the cutting waste was evaluated using a general-purpose drilling machine. Cutting chips that are divided to 1 mm or less are excellent, cutting scraps that exceed 1 mm and 2 mm or less are good, cutting scraps that exceed 2 mm and 3 mm or less are acceptable, and those that exceed 3 mm are considered defective. . Usable levels are good, good and good, more preferred are good and good. In addition, although cutting scraps were at a usable level, those with chipping or the like around the hole after cutting were regarded as “chips” and could not be used. The cutting conditions were a 2 mmφ carbide drill, a rotation speed of 420 rpm, and no cutting oil.

The evaluation of the material structure was determined by observing the structure of each of three visual fields (corresponding to a total of nine visual fields) with respect to any three rolled surfaces of the plate-like sample using an optical microscope. The grain boundary inclusion rate f was defined by the following equation by measuring the grain boundary length of the β phase and the length of the γ phase formed on the grain boundary of the β phase in each field of view, and calculating the total sum.

Grain boundary inclusion rate f = total of γ phase length on β phase grain boundary / β phase grain boundary length × 100 (%)

The thickness of the γ phase formed on the β phase grain boundary was measured at 20 points in each field of view, and the average was taken as the γ phase thickness. The average crystal grain size of the β phase was measured based on the cutting method of JIS H 0501 and used as the average grain size. The ratio obtained by dividing the thickness of the obtained γ phase by the average particle size of the β phase was calculated by the following equation.

Average value of γ phase thickness on β phase grain boundary / β phase average crystal grain size x 100 (%)

  The number of γ phases in the β-phase grains was measured and summed up in each field, and was divided by the sum of the observation field areas to be normalized to obtain the number density of γ phases in the grains.

  Examples 1 to 13 of the present invention were excellent in machinability in the form of components and structures within the scope of the present invention. Inventive Examples 3, 8, and 9 in which the number density of γ phases in the β phase was particularly high were particularly excellent in machinability.

  In Comparative Examples 1 and 4, the machinability was inferior because the grain boundary coverage f and the number density of γ phases in the grains were smaller than the range of the present invention. In Comparative Examples 3 and 6, since the thickness ratio of the γ phase on the β phase grain boundary and the number density of the γ phase in the grain were larger than the range of the present invention, the cutting waste shape was “excellent” Since chipping occurred around the hole, it was not allowed to be used as “chipping”. During the cutting test, cracks propagated from the machined part and destroyed. In Comparative Example 5, the machinability was inferior because the grain boundary coverage ratio f and the thickness ratio of the γ phase on the grain boundary were smaller than those of the present invention. In Comparative Examples 2, 7 and 8, the test was stopped as described above.

(Example 2)
Ingots having a diameter of 200 mm × 500 mm were prepared from the copper alloys of the inventive examples and comparative examples having the compositions shown in Table 2 as alloy billets for hot extrusion.

  In Invention Examples 2-1 to 2-3, the pouring gate and the bottom of the ingot obtained were cut and heated to 750 ° C., held at that temperature for 1 hour, and then subjected to extrusion to obtain a thickness of 10 mm × A base plate having a width of 180 mm was obtained. Immediately after extrusion, it was rapidly cooled to room temperature (cooling rate of 150 ° C./min or more). Thereafter, a sample having a length of 100 mm was sampled, followed by heat treatment at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling to room temperature.

  In Invention Examples 2-4 to 2-6, the pouring gate and the bottom of the ingot obtained were cut and heated to 750 ° C., held at that temperature for 1 hour, and then subjected to extrusion to obtain a rod having a diameter of 20 mmφ. The material was obtained. Immediately after extrusion, it was rapidly cooled to room temperature (cooling rate of 150 ° C./min or more). Thereafter, a sample having a length of 100 mm was sampled, followed by heat treatment at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling to room temperature.

  In Invention Example 2-7, the sprue and bottom of the resulting ingot were cut and heated to 520 ° C., held at that temperature for 1 hour, and then subjected to extrusion to obtain a rod having a diameter of 20 mmφ. . Immediately after extrusion, it was rapidly cooled to room temperature (cooling rate of 150 ° C./min or more). Thereafter, a sample having a length of 100 mm was sampled, heat-treated at 680 ° C. for 30 minutes in an argon gas atmosphere, and water-cooled. Subsequently, heat treatment was performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling was performed to room temperature.

  In Comparative Example 2-1, the process is the same up to the hot extrusion of Invention Example 2-7, but after taking a sample of 100 mm length, heat treatment is performed at 450 ° C. for 60 minutes in an argon gas atmosphere, and air cooling is performed to room temperature. It was.

  In Comparative Example 2-2, the sprue and bottom of the resulting ingot were cut and heated to 450 ° C., held at that temperature for 1 hour, and then subjected to extrusion. As a result, cracking occurred in the material. The trial was discontinued.

  The machinability of each of the copper alloy sheet samples thus obtained was evaluated under the same conditions as in Example 1.

  For the evaluation of the material structure, both the plate sample and the rod sample should be observed in 3 visual fields (corresponding to 9 visual fields in total) using an optical microscope at any 3 locations in the plane perpendicular to the extrusion direction. Determined by The quantitative evaluation of the tissue is the same as in Example 1.

  Inventive Examples 2-1 to 2-7 were excellent in machinability in the form of components and structures within the scope of the present invention.

  In Comparative Example 2-1, the grain boundary coverage ratio f and the number density of γ phases in the grains were larger than the range of the present invention, so that the shape of the chip was “excellent”, but chipping occurred around the hole. For this reason, it could not be used as a “chip”. In Comparative Example 2-2, the test was stopped as described above.

1 β phase grain 2 γ phase on β phase grain boundary 3 γ phase in β phase 4 Thickness of γ phase on β phase grain boundary

Claims (12)

A copper alloy material containing Zn in an amount of 48 to 54 mass%, the balance being Cu and inevitable impurities,
The γ phase is formed on the grain boundary of the β phase so as to cover the periphery of the β phase, and when the ratio of the γ phase included in the total grain boundary length of the β phase is evaluated by cross section, the grain boundary The coverage rate is 60% or more,
A copper alloy material excellent in machinability, wherein the ratio of the average value of the thickness of the γ phase to the average particle size of the β phase is 0.5% or more and 10% or less. The γ phase is dispersed in the β phase grains, and the number density of the γ phases in the β phase grains is 250 / mm ² or more and less than 1000 / mm ² , A copper alloy material having excellent machinability as described in 1.   The copper alloy material according to claim 1 or 2, wherein the shape is a plate material.   The process according to claim 1, further comprising a treatment in which a heat treatment for dispersing the γ phase is performed at 300 ° C. or more and less than 600 ° C. for 10 to 600 minutes after the heat treatment for forming a β single phase is performed at 600 ° C. or more and 840 ° C. or less for 10 to 120 minutes The manufacturing method of the copper alloy material of any one.   A heat treatment for forming a β single phase at 600 ° C. or higher and 840 ° C. or lower for 10 to 120 minutes and then forming a γ phase so as to cover the β phase grain boundaries at a temperature of 500 ° C. or higher and lower than 600 ° C. for 10 to 120 minutes The process according to any one of claims 1 to 3, comprising a process of forming a γ phase in grains of a β phase at a temperature of 300 ° C or higher and lower than 500 ° C for 120 to 600 minutes in any order. A method for producing a copper alloy material.   A process including a hot working step before the heat treatment to form a β single phase, including a manufacturing step in which the material heating before the hot working is performed at 600 ° C. or higher and 840 ° C. or lower and the hot working is finished at 470 ° C. or higher. Item 6. The manufacturing method according to Item 4 or 5.   The manufacturing according to claim 6, wherein the hot working is hot rolling, and includes a manufacturing process in which material heating before hot rolling is performed at 600 ° C. or higher and 840 ° C. or lower and hot rolling is ended at 470 ° C. or higher. Method.   The manufacturing according to claim 6, wherein the hot working is hot extrusion, and includes a manufacturing process in which material heating before hot extrusion is performed at 600 ° C. or higher and 840 ° C. or lower and hot extrusion is ended at 470 ° C. or higher. Method.   Including the hot working process, material heating before hot working is performed at 600 ° C. or more and less than 840 ° C., and the hot working is finished at 600 ° C. or more and rapidly cooled to make β single phase simultaneously with hot working. The manufacturing method of the copper alloy material according to any one of claims 1 to 3, further comprising a manufacturing step including a process of performing a heat treatment for dispersing the γ phase at 300 ° C or higher and lower than 600 ° C for 10 to 600 minutes.   Including the hot working process, material heating before hot working is performed at 600 ° C. or more and less than 840 ° C., and the hot working is finished at 600 ° C. or more and rapidly cooled to make β single phase simultaneously with hot working. Later, heat treatment is performed at 500 ° C. or more and less than 600 ° C. for 10 to 120 minutes so that the γ phase is formed so as to cover the β phase grain boundaries, and γ phase is formed at 300 ° C. or more and less than 500 ° C. for 120 minutes. The manufacturing method of the copper alloy material of any one of Claims 1-3 including the process which implements the heat processing performed for -600 minutes in arbitrary orders.   The manufacturing method according to claim 9 or 10, wherein the hot working is hot rolling.   The manufacturing method according to claim 9 or 10, wherein the hot working is hot extrusion.

Images