JP4431741B2 - Method for producing copper alloy - Google Patents

Description

  The present invention has strength, conductivity, stress relaxation resistance, bending workability, shearing workability, etc. suitable as a material for electrical and electronic parts such as connectors, lead frames, relays, switches, etc. The present invention relates to a copper alloy excellent in cost and a manufacturing method thereof.

  With the recent development of electronics, there is a strong demand for high integration, miniaturization, high reliability, and low cost of electrical and electronic parts such as connectors. In order to meet these requirements, the copper alloy material must have good strength, electrical conductivity, stress relaxation resistance, bending workability and shear workability.

Conventionally, brass has been used as a low-cost material and has excellent moldability, but it is not fully satisfactory in terms of tensile strength, and is inferior in corrosion resistance, stress corrosion cracking resistance and stress relaxation characteristics. ing. On the other hand, phosphor bronze is excellent in the balance of strength, bending workability, stress corrosion cracking resistance and stress relaxation resistance. In addition, it cannot be machined, and is inferior in shear workability, which is disadvantageous in terms of cost.
Moreover, the opportunity for Sn plating of the material for connectors increases, and the use of Sn in the alloy increases the utilization as a raw material. Further, as represented by brass, when Zn is contained, an alloy having an excellent balance of strength, workability, and cost is easily obtained. From such a viewpoint, the Cu—Zn—Sn alloy is a remarkable alloy system. However, in order to maintain the required properties, it is necessary to contain a certain amount of Zn and Sn. However, when the Zn content and Sn content increase, hot cracking is likely to occur, and there is a problem of cost increase due to a decrease in yield.

Under such circumstances, a Cu—Zn—Sn alloy having an excellent balance of various properties has been proposed by containing appropriate amounts of Zn and Sn and adopting an appropriate manufacturing method (see, for example, Patent Document 1). .) Further, in order to improve the stress corrosion cracking resistance, a Cu—Zn—Sn—Si alloy containing Si or the like has been proposed (for example, see Patent Document 2), and in order to further improve the punching workability. In addition, a Cu—Zn—Sn alloy in which Pb, Bi, Se, Te, Ca and the like are added and covered with a Pd layer has been proposed (for example, see Patent Document 3).
JP 2001-294957 A JP 2002-088428 A Japanese Patent No. 3014673

First, the tensile strength is required to be 700 N / mm ² or more. Moreover, in order to suppress generation | occurrence | production of the Joule heat by electricity supply, it is preferable that electrical conductivity is 20% IACS or more. Furthermore, it is necessary to be excellent in corrosion resistance and stress corrosion cracking resistance. Further, since a thermal load is applied, the stress relaxation resistance must be excellent. Specifically, the stress corrosion cracking life is at least three times that of a conventional brass, and the stress relaxation rate is not more than half that of a kind of brass at 150 ° C., preferably not more than 25%, more preferably not more than 20%. is necessary. Furthermore, in order to ensure shape and dimensional accuracy, bending workability and shear workability must be good.
In addition, it combines the features of brass and phosphor bronze, at a price close to brass, with a tensile strength of 700 N / mm ² or more, an electrical conductivity of 20% IACS or more, stress corrosion cracking resistance, stress relaxation characteristics, and shear processability. A good material is desired.
However, in the conventional method, control of Zn amount, Sn amount, impurity amount, and hot rolling conditions is very strict, and the yield may be reduced due to fine cracks, so that hot rolling property is also excellent. It is desirable to provide a copper alloy.
In particular, in recent years, a large amount of copper scrap has been used from the viewpoint of environmental consideration and resource saving, and accordingly, elements such as Bi, Se, Te, Sb, Pb, As, Ge, and S are mixed in the Cu—Zn—Sn alloy. The opportunity has grown. These elements have the effect of improving the alloy's shear workability (punching workability) and solderability, but tend to form a low melting point eutectic structure with Sn and promote the segregation of Sn to grain boundaries. However, there is a problem that even a very small amount (about several ppm) has a great influence on the hot workability of the alloy.
In view of such conventional problems, the present invention is a copper alloy that has the above-mentioned properties required for materials for electrical and electronic parts such as connectors with the development of electronics, that is, tensile strength, It is an object of the present invention to provide a copper alloy excellent in electrical conductivity, stress relaxation resistance, bending workability, shear workability, hot workability and cost, and a method for producing the same.

As a result of intensive studies to solve the above problems, the present inventor has made the present invention. That is, according to the present invention, first, Zn is 20 to 41% by weight, Sn is 0.5 to 1.9% by weight, and at least one of Bi, Se, Te, Sb, Pb, As, Ge, and S. A copper alloy containing 0.01 to 0.2% by weight of the total amount of elements, the balance being Cu and inevitable impurities; second, 20 to 41% by weight of Zn and 0.5 to 1.9 Sn The total amount of at least one element selected from wt%, Bi, Se, Te, Sb, Pb, As, Ge, and S is 0.01 to 0.2 wt%. Ti, V, Cr, Mn, Fe, Co A copper alloy containing at least one element of Ni, Zr in a total amount of 0.05 to 2.0% by weight with the balance being Cu and unavoidable impurities; third, 20 to 41% by weight of Zn Sn: 0.5 to 1.9% by weight, Bi, Se, Te, Sb, Pb, As, Ge, S Contains the above elements in a total amount of 0.01 to 0.2% by weight, and contains at least one element of B, C, Mg, Sc, Y, La, and Ce in a total amount of 0.005 to 0.5% by weight. A copper alloy consisting of Cu and inevitable impurities; fourth, Zn is 20 to 41% by weight, Sn is 0.5 to 1.9% by weight, Bi, Se, Te, Sb, Pb, As, A total amount of at least one element of Ge and S is 0.01 to 0.2% by weight, and a total amount of at least one element of Ti, V, Cr, Mn, Fe, Co, Ni, and Zr. 0.05 to 2.0% by weight, containing at least one element of B, C, Mg, Sc, Y, La and Ce in a total amount of 0.005 to 0.5% by weight, with the balance being Cu and Copper alloy composed of inevitable impurities; Fifth, the copper alloy has a tensile strength of 700 N / mm ² or more and a conductivity of 20%. The copper alloy according to any one of 1 to 4, wherein the IACS or more, the crack depth by hot rolling is 0.3 mm or less, the fracture surface ratio after shearing is 50% or more, and the stress relaxation rate is 20% or less. It is.

  Furthermore, as a method for producing a copper alloy according to the present invention, sixthly, a raw material of the copper alloy having the above composition is dissolved, and at a cooling rate of 50 ° C./min or more in a temperature range from the liquidus temperature to 600 ° C. After cooling to obtain an ingot, hot rolling is performed at a temperature of 900 ° C. or less, and then the cold-rolling and annealing in a temperature range of 300 to 650 ° C. are repeated to reduce the crystal grain size after annealing to 25 μm or less. Then, a method for producing a copper alloy according to any one of 1 to 5, wherein final cold rolling at a processing rate of 30% or higher and low temperature annealing at 450 ° C. or lower are performed; seventhly, in the hot rolling, The rolling reduction in the first pass hot rolling is 5-30%, the rolling reduction in the next pass hot rolling is 5-40%, and the rolling reduction in the final pass hot rolling is 25% or more. , Sixth manufacturing method; eighth, the first pass The manufacturing method according to 7, wherein the rolling reduction in hot rolling is 10 to 20%; ninth, the manufacturing method according to any of 6 to 8, wherein the crystal grain size after annealing is 15 μm or less. 10thly, the production method according to any one of 6th to 9th, wherein a processing rate of the final cold rolling is 60% or more.

The copper alloy according to the present invention is a copper alloy having various properties required for materials for electrical and electronic parts such as connectors, and 0.2% proof stress and tensile strength compared to conventional brass and phosphor bronze. Excellent balance of strength, electrical conductivity, bending workability and shear workability, stress relaxation resistance characteristics and stress corrosion cracking resistance, and good hot workability.
Moreover, according to the manufacturing method according to the present invention, by adding a component cheaper than copper, that is, by using a large amount of Sn plating scraps, free-cutting brass scraps, etc., while reducing costs, such as excellent connectors It is possible to provide a copper alloy that is optimal for materials for electric and electronic parts.

Embodiments of the copper alloy according to the present invention include 20 to 41 wt% Zn, 0.5 to 1.9 wt% Sn, at least one of Bi, Se, Te, Sb, Pb, As, Ge, and S. The total amount of elements of at least one species is 0.01 to 0.2% by weight. If necessary, the total amount of at least one element of Ti, V, Cr, Mn, Fe, Co, Ni, and Zr is included. 0.05 to 2.0% by weight and / or at least one element selected from B, C, Mg, Sc, Y, La, and Ce in a total amount of 0.005 to 0.5% by weight. The balance is made of Cu and inevitable impurities. The reason why the amount of the copper alloy component is limited is as follows.
When Zn is added, the strength and springiness of the copper alloy are improved, and Zn is cheaper than Cu. Therefore, it is desirable to add a large amount of Zn. However, if the amount of Zn exceeds 41% by weight, grain boundary segregation becomes severe in the presence of Sn, and the hot workability of the copper alloy is remarkably reduced. In addition, the cold workability, corrosion resistance and stress corrosion cracking resistance of the copper alloy are also reduced. On the other hand, if the amount of Zn is less than 20% by weight, the strength and springiness of the copper alloy are insufficient, and further, when the scrap with the surface treatment of Sn is used as the raw material, hydrogen gas occlusion during the dissolution of the copper alloy raw material is not possible. This increases the number of ingot blowholes. In addition, the amount of inexpensive Zn is small, which is economically disadvantageous. Accordingly, the Zn content is in the range of 20 to 41% by weight, preferably in the range of 24 to 35% by weight, and more preferably in the range of 24 to 30% by weight.

Sn has an effect of improving mechanical properties such as strength and elasticity. Moreover, it is preferable that a copper alloy contains Sn as an additive element also from the point of reuse of the material surface-treated with Sn, such as Sn plating. However, when Sn content increases, the electrical conductivity of a copper alloy will fall rapidly, and grain boundary segregation will become intense in coexistence with Zn, and hot workability will fall remarkably. In order to ensure hot workability, the Sn content must be in a range not exceeding 1.9% by weight. On the other hand, if the Sn content is less than 0.5% by weight, the effect of improving the mechanical properties of the copper alloy is small, and it becomes difficult to use press scraps and the like subjected to Sn plating as raw materials. Therefore, the Sn content is in the range of 0.5 to 1.9% by weight, and preferably in the range of 0.6 to 1.6% by weight.
Bi, Se, Te, Sb, Pb, As, Ge, and S have an effect of improving the shear workability. When the total amount is less than 0.01% by weight, the above effect cannot be obtained sufficiently, and it becomes difficult to use a large amount of brass scrap containing these elements as a raw material. On the other hand, when the total amount exceeds 0.2% by weight, these elements easily form a low melting point eutectic structure with Sn, promote the segregation of Sn to the grain boundary, and significantly reduce the hot workability. Therefore, the total amount is in the range of 0.01 to 0.2% by weight, preferably in the range of 0.01 to 0.1% by weight.

Ti, V, Cr, Mn, Fe, Co, Ni, and Zr have functions of increasing the alloy strength and reducing the stress relaxation, respectively. In particular, Bi, Se, Te, Sb, Pb, As, Ge, S and high melting point compounds are easily formed, and the hot workability is improved. When the total amount is less than 0.05% by weight, the above-described effect is not sufficiently exhibited, and when it exceeds 2.0% by weight, hot workability and cold workability are deteriorated. It is also economically disadvantageous. Accordingly, the total amount is in the range of 0.05 to 2.0% by weight, preferably in the range of 0.1 to 1.0% by weight, and more preferably in the range of 0.2 to 1.0% by weight.
B, C, Mg, Sc, Y, La and Ce have the effect of suppressing grain boundary precipitation and grain boundary oxidation of Sn and Bi, Se, Te, Sb, Pb, As, Ge, S, Has the effect of improving workability and cold workability. When the total amount is less than 0.005% by weight, the above-mentioned effect is not sufficiently exhibited, and when it exceeds 0.5% by weight, hot workability and cold workability are deteriorated. Therefore, the total amount is in the range of 0.005 to 0.5% by weight, preferably in the range of 0.01 to 0.2% by weight.

Further, if the limited component as described above, a tensile strength of 700 N / mm ² or more, preferably 800 N / mm ² or more, conductivity of 20% IACS or more, the stress relaxation ratio of 20% or less, preferably 15% or less, and other necessary characteristics, specifically, corrosion resistance, stress corrosion cracking resistance (crack life in ammonia vapor is more than three times that of brass), stress relaxation resistance (150 ° C. A copper alloy having a relaxation rate less than half of that of a kind of brass and equivalent to phosphor bronze), shear workability (press punchability), and the like can be produced.
The copper alloy further comprises 0.01 to 5 wt% Al, 0.01 to 1 wt% Ca, 0.01 to 3 wt% Si, 0.01 to 3 wt% Cd, 0.01. ~ 3 wt% Be, 0.01-1 wt% Ba, 0.01-5 wt% Au, 0.01-5 wt% Ag, 0.005-0.5 wt% P A total amount of at least one element may be 0.01 to 5% by weight.
These elements can further improve the strength without significantly impairing the electrical conductivity, Young's modulus, and moldability. Moreover, it is advantageous also when using various copper alloy scraps as a raw material. If it is out of the content range of each element, a desired effect cannot be obtained, or it is disadvantageous in terms of hot workability, cold workability, conductivity and cost.

Next, an embodiment of a method for producing a copper alloy according to the present invention will be described.
First, the copper alloy raw material according to the present invention is melted and cast. An atmospheric atmosphere is sufficient as the atmosphere, but sealing with an inert gas is preferable in terms of preventing oxidation. However, in a reducing gas atmosphere, when the temperature is high, it is disadvantageous due to absorption and diffusion of hydrogen due to decomposition of moisture.
Next, after melting the raw material, it is desirable to cast the ingot by continuous casting. This continuous casting may be either a vertical type or a horizontal type. However, cooling is performed at a cooling rate of 50 ° C./min or more in the temperature range from the liquidus temperature to 600 ° C. When the cooling rate is less than 50 ° C./min, segregation of Sn and Bi, Se, Te, Sb, Pb, As, Ge, S is likely to occur at the grain boundary, and the subsequent hot workability is deteriorated, resulting in a decrease in yield. cause. The temperature range that defines the cooling rate may be a temperature range from the liquidus temperature to 600 ° C. Even if the temperature range above the liquidus is defined, there is no effect. On the other hand, in the temperature range lower than 600 ° C., Sn and Bi, Se, Te, Sb, Pb, Since excessive segregation of As, Ge, and S does not occur, the temperature range that defines the cooling rate is the temperature range from the liquidus temperature to 600 ° C.

  Hot rolling is performed after melt casting. The heating temperature of hot rolling is 900 ° C. or less. If the temperature exceeds 900 ° C., hot cracking occurs due to the eutectic structure of Sn and Bi, Se, Te, Sb, Pb, As, Ge, and S, and the yield decreases. The rolling reduction during the first pass hot rolling at a temperature of 900 ° C. or lower is preferably 5 to 30%. If the rolling reduction exceeds 30%, cracks are likely to occur along the cast grain boundaries. On the other hand, if the rolling reduction is less than 5%, dynamic recrystallization or static recrystallization between passes hardly occurs, and hot cracking may occur during the second pass rolling. In addition, the number of rolling passes increases, which is not efficient. By dynamically recrystallizing after 2 to 3 passes, a microscopic segregation at the time of casting and disappearance of the cast structure makes it possible to obtain a structurally homogeneous material even if the amount of Zn and Sn of the composition of the copper alloy according to the present invention is included. Obtainable. More preferably, the rolling reduction of the first pass is 10 to 20%. In the next pass, the rolling reduction is preferably 5 to 40%, and it is possible to prevent the occurrence of hot cracking and subsequently to efficiently roll. Further, it is preferable that the rolling reduction of the final pass is as large as possible, and specifically, a rolling reduction of 25% or more is preferable. Thereby, the crystal grain size after hot rolling can be controlled to preferably 35 μm or less, and more preferably 15 μm or less. If the crystal grain size after hot rolling exceeds 35 μm, the subsequent cold work rate and the control range of annealing conditions are narrow, and if it deviates even a little, the crystal grains tend to be mixed and the characteristics deteriorate.

The surface is chamfered as necessary after hot rolling. Then, cold rolling and annealing in a temperature range of 300 to 650 ° C. are repeated, and the crystal grain size after annealing is set to 25 μm or less. If the temperature is less than 300 ° C., the time required for controlling the crystal grains becomes long and uneconomical, and if it exceeds 650 ° C., the crystal grains become coarse in a short time. When the grain size after annealing exceeds 25 μm, mechanical properties such as 0.2% proof stress and workability deteriorate. The crystal grain size after annealing is preferably 15 μm or less, more preferably 10 μm or less.
The annealed material thus obtained is subjected to final cold rolling at a processing rate of 30% or more and low temperature annealing at 450 ° C. or less, so that the 0.2% proof stress is 650 N / mm ² or more and the tensile strength is A copper alloy having 700 N / mm ² or more, electrical conductivity of 20% IACS or more, and stress relaxation rate of 20% or less is obtained. If the final cold work rate is less than 30%, the strength improvement by work hardening is insufficient, and the mechanical properties are not sufficiently improved, and the work rate is preferably 60% or more. Low temperature annealing is necessary to further improve the 0.2% yield strength, tensile strength, spring limit and stress relaxation resistance. When the temperature exceeds 450 ° C., it softens in a short time, and in both the batch type and the continuous type, characteristic variations easily occur in the work. Therefore, the temperature condition of the low temperature annealing is set to 450 ° C. or less.
After the material thus obtained is pressed on a terminal, it may be heat-treated at a temperature of 100 to 280 ° C. for 1 to 180 minutes. By this heat treatment, the spring limit value and the stress relaxation resistance lowered by the press working are improved, and further, whisker countermeasures can be realized. If the temperature is lower than 100 ° C., such an effect is not sufficient. If the temperature exceeds 280 ° C., contact resistance, solderability, and workability deteriorate due to diffusion and oxidation. Further, if the heat treatment time is less than 1 minute, the effect is not sufficient, and if it exceeds 180 minutes, the above-described characteristics are deteriorated due to diffusion or oxidation, and it is not economical.

  Hereinafter, although the copper alloy by this invention and its manufacturing method are demonstrated in detail, the technical scope of this invention is not limited to this.

[Examples 1 to 15 and Comparative Examples 1 to 14] After each copper alloy raw material having the chemical composition (wt%) shown in Table 1 was melted at a temperature 70 ° C higher than the liquidus temperature, a vertical compact continuous Using a casting machine, it was cast into an ingot of 30 × 70 × 1000 (mm, initial thickness is 30 mm). However, by adjusting the primary cooling by the mold and the secondary cooling by the water shower, the cooling rate from the liquidus to 600 ° C. was a condition that greatly exceeded 50 ° C./min (the cooling rate was obtained by casting a thermocouple). It was measured while casting together in the lump, specifically the cooling rate range was 70-90 ° C./min).
Then, after heating each ingot to 800-860 degreeC, it hot-rolled to thickness 5mm, and evaluated hot workability by the crack of the surface or edge. However, hot rolling was performed for 10 passes, and the reduction rate per pass was 15%, and the reduction rate of the final pass was 25%. Those with no cracks confirmed by an optical microscope of 50 times after pickling, with crack depth of 0.3 mm or less (that is, no cracks are confirmed after chamfering or milling at 0.3 mm on one side) ◯, and those having a crack depth exceeding 0.3 mm were evaluated as x. Furthermore, the hot rolling end temperature was set to 600 ° C., and the crystal grain size was controlled to about 20 μm by rapid cooling after hot rolling.
Next, it was rolled to a thickness of 1 mm by cold rolling, heat-treated at a temperature of 450 to 520 ° C., and adjusted so that the crystal grain size was about 10 μm. After pickling, it was finally cold-rolled to a thickness of 0.25 mm, and subjected to low-temperature annealing at 230 ° C. in the final step. A test piece was collected from the strip thus obtained.

Using the strips obtained as described above, tensile strength, electrical conductivity, stress relaxation rate, shear workability, and stress corrosion cracking life were measured. Tensile strength was measured according to JIS-Z-2241 and conductivity was measured according to JIS-H-0505. The stress relaxation test was performed by applying a bending stress equivalent to 80% of 0.2% proof stress to the sample surface, holding the sample at 150 ° C. for 500 hours, and measuring the bending distortion. The stress relaxation rate was calculated by the following formula.
Stress relaxation rate (%) = [(L1-L2) / (L1-L0)] × 100
[L0: Jig length (mm), L1: Length of sample at start (mm), L2: Horizontal distance between sample ends after processing (mm)]
Evaluation of shear workability was performed in accordance with JCBA-T310 (Copper Society Standard Standard, Shear Test Method for Copper and Copper Alloy Sheet Strips). This is done by observing the fracture surface after shearing. The greater the fracture surface ratio (fracture thickness / plate thickness x 100), the better the shearing workability.
The stress corrosion cracking test was performed by applying a bending stress equivalent to 80% of 0.2% proof stress and holding it in a desiccator containing 12.5% ammonia water. The exposure time was 10 minutes and tested up to 150 minutes. After the exposure, the test piece at each time was taken out, the film was pickled and removed as necessary, and cracks were observed with an optical microscope at a magnification of 100 times. The time 10 minutes before the crack was confirmed was defined as the stress corrosion crack life.
These results are shown in Table 1.

From the results shown in Table 1, the copper alloys of Examples 1 to 15 within the specified component range are excellent in hot workability, advantageous in production, and have shear workability, tensile strength, and conductivity. The balance is excellent, and the stress relaxation resistance and stress corrosion cracking resistance are also good. Therefore, the copper alloys of Examples 1 to 15 are copper alloys having extremely excellent characteristics as electrical and electronic materials such as connectors.
On the other hand, all the copper alloys of Comparative Examples 1 to 5 having a small content (or not contained) such as Bi, Se, Te, Sb, Pb, As, Ge, and S have a fracture portion ratio of less than 50%. Therefore, shear workability is inferior. Moreover, the copper alloys of Comparative Examples 4 and 5 having a high Sn content have poor hot workability, and the copper alloys of Comparative Examples 1 and 2 having a low Sn content are not inferior in hot workability. However, the tensile strength and stress relaxation resistance are inferior, and the shear processability is also inferior as described above.

Copper alloys having a large content of Bi, Se, Te, Sb, Pb, As, Ge, S, etc. in Comparative Examples 6 to 10 are excellent in shear workability, but are inferior in hot workability, resulting in a decrease in yield. There is a problem of cost increase.
Further, the copper alloys of Comparative Examples 11 to 13 having a large content of Ti, Mn, Fe and B are not inferior in tensile strength, stress relaxation resistance and shear workability, but cracks are caused during hot rolling. In the balance with the subsequent cold working, it was not possible to manufacture with good yield up to the final thickness. Further, the copper alloy of Comparative Example 14 having a small Sn and B content is inferior in tensile strength, shear workability, stress relaxation resistance, and stress corrosion cracking life.

  [Example 16, Comparative Examples 15 and 16] The same copper alloy as Example 11 shown in Table 1 (Example 16), commercially available brass (C26000-H08, Comparative Example 15), and spring For phosphor bronze (C52100-H08, Comparative Example 16), tensile strength, electrical conductivity, fracture surface ratio, stress relaxation rate, and stress corrosion cracking life were measured by the same methods as in Examples 1-15. These results are shown in Table 2. In addition, these commercially available materials are classified into H08 (for spring material), and are of high strength among the same components.

  From the results shown in Table 2, the copper alloy of Example 16 is higher in tensile strength, stress relaxation resistance, breakage than brass (Comparative Example 15), which is a conventional material for electrical and electronic use such as a connector. It can be seen that the cross-sectional ratio, stress corrosion cracking resistance, etc. are improved. Moreover, it is excellent in electrical conductivity even compared with phosphor bronze for spring (Comparative Example 16). Moreover, the phosphor bronze for spring contains 8% of expensive Sn, the raw material cost is likely to increase rapidly, and it cannot be hot-rolled, so the manufacturing method is limited and the total cost including the manufacturing cost is inferior. . Therefore, it can be said that the copper alloy of Example 16 is sufficiently superior to conventional brass and phosphor bronze.

  [Examples 17, 18, 19 and Comparative Examples 17 and 18] By changing the heating temperature during hot rolling of the copper alloys of Examples 1 and 11 shown in Table 1, the surface and edge after hot rolling were changed. The cracking situation was observed. As a result, no hot cracking occurred at the heating temperature of 860 ° C. or lower (specifically, 800 to 850 ° C.) (Examples 17 and 18). In particular, the copper alloy of Example 11 containing 0.12% B exhibited no hot cracking even when the hot rolling temperature was raised to 900 ° C. (Example 19). On the other hand, even in the copper alloys of Examples 1 and 11 shown in Table 1, hot cracking occurs at a heating temperature of 920 ° C. (Comparative Examples 17 and 18), and even in an appropriate component range. It has been found that depending on the heating temperature, hot cracking may occur and yield may be reduced.

[Example 20, Comparative Examples 19 and 20] An ingot of a copper alloy having the same composition as that of Example 11 shown in Table 1 was heated to 840 ° C, and hot rolling was performed for two passes. Samples obtained by water cooling immediately after rolling in each pass were corroded by electrolytic polishing in a solution of phosphoric acid and distilled water (1: 1), and then the crystal grain structure was observed with an optical microscope at a magnification of 300 times. . However, the rolling reduction in the first pass was 15% (Example 20), 4% (Comparative Example 19), and 35% (Comparative Example 20), respectively, and the rolling reduction in the second pass was 25%.
In the structure of the copper alloy of Example 20, dynamic recrystallized grains were generated along all crystal grain boundaries after rolling in the first pass, and dynamic recrystallized grain structures were observed over almost the entire area after rolling in the second pass. It was. On the other hand, in the structure of Comparative Example 19, almost no dynamic recrystallized grains were observed after the first pass rolling, and cracks were observed along some crystal grain boundaries after the second pass rolling. Further, in the structure of Comparative Example 20, the dynamic recrystallized grains are unevenly distributed after the first pass rolling, and cracks are observed along some crystal grain boundaries. The crack further expanded. Therefore, it has been found that hot rolling cracks may occur depending on the rolling reduction ratio in the first pass, which may lead to a decrease in yield.

  Providing copper alloys with tensile strength, electrical conductivity, stress relaxation resistance, bending workability, shear workability, hot workability and cost, etc., and applied to materials for electrical and electronic parts such as connectors can do.

Claims (2)

Zn is 24 to 30% by mass , Sn is 0.5 to 1.9 % by mass , Bi, Se, Te, Sb, Pb, As, Ge, and at least one element among S in a total amount of 0.01 to containing 0.2 wt%, the balance Ri Do Cu and inevitable impurities, tensile strength of 700 N / mm ² or more, conductivity of 20% IACS or more, 0.3mm or less crack depth by hot rolling, fracture surface ratio after shearing is at least 50%, stress relaxation ratio of 20% or less der Ru copper alloy,
Zn is 24 to 30% by mass , Sn is 0.5 to 1.9 % by mass , Bi, Se, Te, Sb, Pb, As, Ge, and at least one element among S in a total amount of 0.01 to 0.2 % by mass , containing at least one element of Ti, V, Cr, Mn, Fe, Co, Ni, Zr in a total amount of 0.05 to 2.0 % by mass with the balance being Cu and inevitable Ri Do from impurities, tensile strength of 700 N / mm ² or more, conductivity of 20% IACS or more, cracking depth by hot rolling 0.3mm or less, fracture surface ratio after shearing is at least 50%, stress relaxation rate of 20% or less der Ru copper alloy,
Zn is 24 to 30% by mass , Sn is 0.5 to 1.9 % by mass , Bi, Se, Te, Sb, Pb, As, Ge, and at least one element among S in a total amount of 0.01 to 0.2 mass% , containing at least one element of B, C, Mg, Sc, Y, La, and Ce in a total amount of 0.005 to 0.5 mass%, with the balance being Cu and inevitable impurities Do Ri, a tensile strength of 700 N / mm ² or more, conductivity of 20% IACS or more, 0.3mm or less crack depth by hot rolling, fracture surface ratio after shearing is at least 50%, stress relaxation rate than 20% der Ru copper alloy,
Zn is 24 to 30% by mass , Sn is 0.5 to 1.9 % by mass , Bi, Se, Te, Sb, Pb, As, Ge, and at least one element among S in a total amount of 0.01 to 0.2 % by mass , Ti, V, Cr, Mn, Fe, Co, Ni, Zr, 0.05 to 2.0 % by mass in total of at least one element selected from B, C, Mg, Sc, Y, La, containing 0.005 to 0.5 wt% in total of at least one element of Ce, the balance Ri Do Cu and inevitable impurities, tensile strength of 700 N / mm ² or more, conductive rate is 20% IACS or more, cracking depth by hot rolling 0.3mm or less, shearing after fracture surface ratio of 50% or more, Ru der stress relaxation rate more than 20% copper alloy, or copper An alloy manufacturing method comprising:
After melting the raw material of the copper alloy having the above composition and cooling at a cooling rate of 50 ° C./min or more in the temperature range from the liquidus temperature to 600 ° C., an ingot is obtained, and then hot at a temperature of 900 ° C. or less. Rolling is performed, and then cold rolling and annealing in a temperature range of 300 to 650 ° C. are repeated to reduce the crystal grain size after annealing to 15 μm or less , then final cold rolling with a processing rate of 60% or more and 450 ° C. or less. This is a manufacturing method for performing low-temperature annealing, in which the rolling reduction in the hot rolling of the first pass in the hot rolling is 10 to 20% , the rolling reduction in the hot rolling of the next pass is 5 to 40%, and the final pass A method for producing a copper alloy, wherein the rolling reduction in hot rolling is 25% or more. The manufacturing method of Claim 1 whose Zn content of the said copper alloy is 24.3-28.6 mass% .