COPPER ALLOY PLATE AND METHOD FOR ITS MANUFACTURING

Abstract

Copper alloy plate having a chemical composition comprising 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus, and the remainder being copper and unavoidable impurities, wherein the sum of the silicon content and six times the phosphorus content is 1 wt.% or more, and wherein the copper alloy plate has a crystal orientation that satisfies I{220} / I{420}≤2,0 under the assumption that the X-ray diffraction intensity at the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and that the X-ray diffraction intensity at the {420} crystal plane thereon is I{420}.

Description

Technical field

[0001] The present invention relates generally to a copper alloy plate and a method for its production. More specifically, the invention relates to a copper alloy plate, such as a plate made of a Cu-Zn-Sn alloy, which is used for electrical and electronic components, such as connectors, conductor frames, relays and switches, and to a method for its production. State of the art

[0002] The materials used for electrical and electronic components such as connectors, conductor frames, relays, and switches must possess good electrical conductivity to suppress the generation of Joule heat due to current flow, as well as sufficient strength to withstand the stresses exerted on them during the assembly and operation of the electrical and electronic devices that utilize these components. Materials used for electrical and electronic components, such as connectors, must also exhibit excellent bending properties, as these components are generally formed by bending. Furthermore, to ensure reliable contact between electrical and electronic components, such as connectors, the materials used for these components must possess excellent stress relaxation resistance.They must be resistant to such a phenomenon (stress relaxation) that the contact pressure between the parts deteriorates with increasing age.

[0003] In recent years, there has been a trend toward integrating, miniaturizing, and lightening electrical and electronic components, such as connectors. Consequently, the copper and copper alloy sheets used as the components must be thinned to achieve the required strength. In line with the miniaturization and increasingly complex shapes of electrical and electronic components like connectors, it is necessary to improve the dimensional accuracy and shape of products manufactured by bending copper alloy sheets. Furthermore, recent years have seen a growing trend toward reducing environmental impact, conserving resources, and saving energy.Accordingly, the copper and copper alloy plates used as material for the parts are increasingly needed to reduce raw material and production costs and to recycle the products made from them.

[0004] However, there are trade-offs between a plate's strength and electrical conductivity, its strength and machinability, and its machinability and stress relaxation resistance. Therefore, a relatively inexpensive plate with good electrical conductivity, strength, machinability, or stress relaxation resistance is chosen according to its intended use, such as for conventional plates for electrical and electronic components, like connectors.

[0005] Conventional general-purpose materials for electrical and electronic components such as connectors include brass, phosphor bronzes, and others. Phosphor bronzes exhibit a relatively excellent balance between the strength, corrosion resistance, stress corrosion cracking resistance, and stress relaxation resistance of a sheet. However, in the case of Class 2 phosphor bronze (C5191), for example, it is not possible to hot-roll a sheet of this material, and it contains approximately 6% expensive tin, thus increasing the cost of the sheet.

[0006] On the other hand, brass (Cu-Zn alloys) is widely used as a material with low raw material and production costs and excellent recycling efficiencies for its products. However, the strength of brass is lower than that of phosphor bronze. The hardness designation for brass with the highest strength is EH (H06). For example, the plate product of first-class brass (C2600-SH) typically has a tensile strength of about 550 MPa, which is comparable to the tensile strength of hardness designation H (H04) of second-class phosphor bronze. Furthermore, the plate product made of first-class brass (C2600-SH) does not exhibit excellent stress corrosion cracking resistance.

[0007] To improve the strength of brass, it is necessary to increase the finish reduction (to increase the hardness rating). Consequently, the machinability in directions perpendicular to the rolling directions (i.e., the machinability in directions where the bending axis runs parallel to the rolling directions) is significantly impaired. For this reason, even when using high-strength brass, there are some cases where it is not possible to machine the sheet to produce an electrical or electronic component such as a connector. For example, if the finish reduction of a sheet of premium brass is increased to raise the tensile strength above 570 MPa, it becomes difficult to press the sheet to produce a small product.

[0008] Particularly in the case of brass, which is a simple alloy of copper and zinc, it is not easy to improve its machinability while maintaining its strength. For this reason, improvements are being made to increase the strength level by adding various elements to brass. For example, there are proposals for copper-zinc alloys to which a third element such as tin, silicon, or nickel is added (see, for example, patent documents 1-3). State of the art document(s) Patent document(s) Patent document 1: Published Japanese patent application no. 2001-164328 (paragraph number 0013) Patent document 2: Published Japanese patent application no. 2002-88428 (paragraph number 0014) Patent document 3: Published Japanese patent application no. 2009-62610 (paragraph number 0019) Patent Document 4: JP 2012-255219 A. SUMMARY OF THE INVENTION Problem to be solved with the invention

[0009] But even when brass (a copper-zinc alloy) is mixed with tin, silicon, nickel or similar substances, there are some cases where it is not possible to sufficiently improve the bendability of a plate made of it.

[0010] It is therefore an object of the present invention to eliminate the aforementioned conventional problems and to provide a cost-effective copper alloy plate with excellent bending machinability, excellent stress corrosion cracking resistance and excellent stress relaxation resistance while maintaining its high strength, as well as a method for its production. Means to solve the problem

[0011] To solve the aforementioned problem, the inventors carefully investigated and determined that it is possible to produce a cost-effective copper alloy plate with excellent bending machinability, excellent stress corrosion cracking resistance, and excellent stress relaxation resistance while maintaining its high strength, if the copper alloy plate has a chemical composition comprising 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus, and the remainder copper and unavoidable impurities, wherein the sum of the silicon content and six times the phosphorus content is 1 wt.-% or more, and if the copper alloy plate has a crystal orientation that satisfies I{220} / I{420}≤2.0, assuming that the X-ray diffraction intensity at the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and that the X-ray diffraction intensity at the {420} crystal plane thereon is I{420}. Thus, the inventors have made the present invention.

[0012] According to the invention, a copper alloy plate is provided which has a chemical composition containing 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus, and copper and unavoidable impurities as the remainder, wherein the sum of the silicon content and six times the phosphorus content is 1 wt.% or more, and wherein the copper alloy plate has a crystal orientation that satisfies I{220} / I{420}≤2.0 under the assumption that the X-ray diffraction intensity on the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and the X-ray diffraction intensity on the {420} crystal plane thereon is I{420}.

[0013] The chemical composition of the copper alloy plate may further comprise 1 wt.% or less of nickel or cobalt and may further comprise one or more elements selected from the group consisting of iron, chromium, magnesium, aluminum, boron, zirconium, titanium, manganese, gold, silver, lead, cadmium, and beryllium, wherein the total amount of these elements is 3 wt.% or less. The copper alloy plate preferably has a mean crystal grain size of 3 to 20 µm. The copper alloy plate preferably has a tensile strength of not less than 550 MPa and preferably a 0.2% proof strength of not less than 500 MPa. The copper alloy plate preferably has an electrical conductivity of not less than 8% IACS.

[0014] According to the present invention, a method for producing a copper alloy plate is provided, the method comprising the steps of: melting and casting raw materials from a copper alloy having a chemical composition containing 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus, and as a remainder copper and unavoidable impurities, wherein the sum of the silicon content and six times the phosphorus content is 1 wt.-% or more; hot rolling of the cast copper alloy with a roll reduction of 90% or more in a temperature range of 900°C to 300°C, wherein the hot rolling with a roll reduction of 10% or more is carried out in a rolling path in a temperature range of 650°C or less; intermediate cold rolling of the hot-rolled copper alloy; intermediate annealing of the intermediate cold-rolled copper alloy at a temperature of 400 to 800°C; finish cold rolling of the intermediate annealed copper alloy with a roll reduction of 30% or less; and low-temperature annealing of the finish cold-rolled copper alloy at a temperature of 450°C or less.

[0015] In this process for producing a copper alloy plate, the rolling reduction in the rolling path is preferably 35% or less during hot rolling at temperatures of 650°C or lower. During intermediate annealing, heat treatment is preferably carried out by setting a holding time and a target temperature within a temperature range of 400°C to 800°C, so that the copper alloy has a mean crystal grain size of 3 to 20 µm after intermediate annealing.

[0016] In the process for producing a copper alloy plate, the chemical composition of the copper alloy plate may further comprise 1 wt.% or less nickel or cobalt and one or more elements selected from the group consisting of iron, chromium, magnesium, aluminum, boron, zirconium, titanium, manganese, gold, silver, lead, cadmium, and beryllium, the total amount of these elements being 3 wt.% or less. The intermediate cold rolling and intermediate annealing may be repeated several times alternately.

[0017] According to the present invention, a terminal block is provided, the material of which is the copper alloy plate described above. EFFECTS OF THE INVENTION

[0018] According to the present invention, it is possible to produce a cost-effective copper alloy plate with excellent bending machinability, excellent stress corrosion cracking resistance and excellent stress relaxation resistance while maintaining its high strength. embodiment of the invention

[0019] The preferred embodiment of a copper alloy plate according to the present invention has a chemical composition comprising 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus, and the remainder being copper and unavoidable impurities, wherein the sum of the silicon content and six times the phosphorus content is 1 wt.% or more, and has a crystal orientation that satisfies I{220} / I{420}≤2.0, assuming that the X-ray diffraction intensity on the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and the X-ray diffraction intensity on the {420} crystal plane thereon is I{420}.

[0020] The preferred embodiment of a copper alloy plate according to the present invention is a Cu-Zn-Sn-Si-P alloy, wherein Sn, Si and P are added to a Cu-Zn alloy containing Cu and Zn.

[0021] Assuming that the X-ray diffraction intensity at the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and the X-ray diffraction intensity at the {420} crystal plane on it is I{420}, the crystal orientation of the copper alloy plate satisfies I{220} / I{420}≤2.0 (preferably I{220} / I{420}≤1.8). If I{220} / I{420} is too large, the bending machinability is impaired.

[0022] Zinc serves to improve the strength and spring properties of copper alloy plates. Since zinc is cheaper than copper, a large amount of zinc is preferably added to the copper alloy. However, if the zinc content exceeds 32 wt.%, a beta (β) phase is formed, which significantly reduces the cold formability and stress corrosion cracking resistance of the copper alloy plate and impairs its cladding and brazing properties due to moisture and heating. On the other hand, if the zinc content is below 17 wt.%, the strength, such as the 0.2% yield strength and tensile strength, and the spring properties of the copper alloy plate are insufficient, and the plate's modulus of elasticity increases. Furthermore, the amount of hydrogen gas absorption during the melting of the copper alloy plate is increased, and cavities are easily formed in the copper alloy ingot.Furthermore, the amount of inexpensive zinc in the copper alloy plate is low, which increases the cost. Therefore, the zinc content is preferably 17 to 32 wt.%, more preferably 17 to 27 wt.%, and most preferably 18 to 23 wt.%.

[0023] Tin serves to improve the strength, stress relaxation resistance, and stress corrosion cracking resistance of the copper alloy plate. For the reuse of tin-surface-treated materials, such as tin-plated materials, the copper alloy plate preferably contains tin. However, if the tin content in the copper alloy plate exceeds 4.5 wt.%, the electrical conductivity of the copper alloy plate is suddenly reduced, and segregation at the grain boundaries of the copper alloy is significantly increased in the presence of zinc, noticeably reducing the hot formability of the copper alloy plate. On the other hand, at a tin content of less than 0.1 wt.%, the improvement in the mechanical properties of the copper alloy plate is diminished, and it becomes difficult to use pressed scrap, etc., coated with tin as raw materials for the copper alloy plate.Therefore, the tin content is preferably 0.1 to 4.5 wt.% and even more preferably 0.2 to 2.5 wt.%.

[0024] Silicon improves the stress corrosion cracking resistance of the copper alloy plate, even at low silicon content. To adequately maintain this function, the silicon content should preferably be at least 0.5 wt.%. However, if the silicon content exceeds 2.0 wt.%, the electrical conductivity of the copper alloy plate is slightly reduced. Furthermore, silicon is a readily oxidizable element, which slightly reduces the castability of the copper alloy, so the silicon content should preferably not be too high. Therefore, the silicon content is preferably 0.5 to 2.0 wt.% and even more preferably 0.5 to 1.9 wt.%.

[0025] Phosphorus improves the stress corrosion cracking resistance of the copper alloy plate, even when the silicon content is low. To adequately maintain this function, the silicon content should preferably be at least 0.01 wt.%. However, if the silicon content exceeds 0.3 wt.%, the electrical conductivity of the copper alloy plate is slightly reduced. Therefore, the phosphorus content is preferably 0.01 to 0.3 wt.% and even more preferably 0.01 to 0.25 wt.%.

[0026] Furthermore, there is a possibility that the function of improving the stress corrosion cracking resistance of the copper alloy plate cannot be sufficiently achieved if the sum of the silicon content and six times the phosphorus content is less than 1 percent by weight.

[0027] The chemical composition of the copper alloy plate may further contain 1% by weight or less (preferably 0.7% by weight or less) nickel or cobalt. The chemical composition of the copper alloy may further contain one or more elements selected from the group consisting of iron, chromium, magnesium, aluminum, boron, zirconium, titanium, manganese, gold, silver, lead, cadmium, and beryllium, wherein the total amount of these elements is 3% by weight or less (preferably 1% by weight or less, more preferably 0.5% by weight or less).

[0028] The mean crystal grain size of the copper alloy plate is preferably 20 µm or less, more preferably 18 µm or less, and most preferably 17 µm or less, since the bendability of the copper alloy plate is advantageously improved when the mean crystal grain size of the copper alloy plate is smaller. On the other hand, the mean crystal grain size of the copper alloy plate is preferably 3 µm or more, and even more preferably 4 µm or more, since there is a possibility that the stress relaxation resistance may be impaired if the mean crystal grain size of the copper alloy plate is too small.

[0029] The tensile strength of the copper alloy plate is preferably not less than 550 MPa and even more preferably not less than 580 MPa, in order to manufacture miniaturized and thinned electrical and electronic components, such as V-connectors. Furthermore, the 0.2% yield strength of the copper alloy plate is preferably not less than 500 MPa and even more preferably not less than 520 MPa.

[0030] The electrical conductivity of the copper alloy plate is preferably not lower than 8%IACS, and even more preferably not lower than 8.5%IACS, in order to suppress the generation of Joule heat due to the current flow corresponding to the high integration of electrical and electronic parts, such as connectors.

[0031] To evaluate the stress relaxation resistance of the copper alloy plate according to the cantilever bolt stress relaxation test prescribed in JEITA EMAS-1011, a test piece (60 mm long x 10 mm wide) is cut from the copper alloy plate such that the longitudinal directions of the test piece are the LD directions (the rolling directions of the copper alloy plate), while the lateral directions are the TD directions (directions perpendicular to the rolling and thickness directions of the copper alloy plate). One end section of the test piece is fixed in its longitudinal directions, and the other end section is fixed in a condition in which a load stress corresponding to 80% of its 0.2% proof strength is applied at a point corresponding to a span of 30 mm on its other end section, so that the thickness directions of the test piece are deflection directions.After the test specimen has been held at 150°C for 500 hours, its deflection is measured. A stress relaxation rate (%) is calculated from the deflection variability. The stress relaxation rate is preferably not higher than 25%, more preferably not higher than 23%, and most preferably not higher than 22%.

[0032] To evaluate the stress corrosion cracking resistance of the copper alloy plate, a bending stress corresponding to 80% of its 0.2% proof strength is applied to a test piece cut from the copper alloy plate, and the test piece is held at 25°C in a desiccator containing 3 wt% ammonia solution. With respect to the test piece taken hourly, the time during which cracks in the copper alloy plate are observed at a magnification of 100x using an optical microscope is preferably not less than 100 hours, more preferably not less than 110 hours, and most preferably not less than 120 hours. This time is preferably longer than twenty times (best, more preferably more than twenty-two times, and most preferably more than twenty-four times) the time (5 hours) in a plate made of commercially available first-class brass (C2600-SH).

[0033] To evaluate the bendability of the copper alloy plate, a bending test piece was cut from the copper alloy plate such that the longitudinal directions of the bending test piece were the directions TD (directions perpendicular to the rolling and thickness directions of the copper alloy plate). When the 90° W bending test (based on JIS H3130) of the bending test piece is performed such that the bending axis of the bending test piece runs in directions LD (the rolling directions of the copper alloy plate), the ratio R / t of the minimum bending radius R to the thickness t of the bending test piece in the 90° W bending test is preferably not higher than 0.7 and more preferably not higher than 0.6.

[0034] The copper alloy plate described above can be produced by a preferred embodiment of a method for producing a copper alloy plate according to the present invention. The preferred embodiment of a method for producing a copper alloy plate according to the present invention comprises: a melting / casting step for melting and casting raw materials from a copper alloy having the chemical composition described above; a hot rolling step for hot rolling the copper alloy with a rolling reduction of 90% or more in a temperature range of 900°C to 300°C after the melting / casting step, wherein the hot rolling is carried out with a rolling reduction of 10% or more (preferably 10% to 35%) in a rolling path in a temperature range of 650°C or less (preferably 650°C to 300°C); and an intermediate cold rolling step for cold rolling the copper alloy after the hot rolling step.An intermediate annealing step to anneal the copper alloy at a temperature of 400 to 800°C after the intermediate cold rolling step; a finish cold rolling step to finish cold rolling the copper alloy with a rolling reduction of 30% or less after the intermediate annealing step; and a low-temperature annealing step to anneal the copper alloy at a temperature of 450°C or less after the finish cold rolling step. These steps are described in detail below. In addition, facing can optionally be performed after the hot rolling step. Pickling, polishing, degreasing, etc., can optionally be performed after each heat treatment. (Melting and casting step)

[0035] After the raw materials of a copper alloy have been melted using the same process as in a conventional brass casting process, an ingot is produced by continuous casting, semi-continuous casting, or similar methods. This is also possible if the raw materials can be melted in the atmosphere (i.e., in an atmospheric environment at ordinary pressure). (Hot rolling step)

[0036] Hot rolling of a copper-zinc alloy is typically carried out at high temperatures of at least 650°C or 700°C to cause the destruction of the cast structure and the softening of the materials through recrystallization during rolling and between rolling passes. However, under such general hot rolling conditions, it is difficult to produce a copper alloy sheet with a specific texture as a preferred embodiment of a copper alloy sheet according to the present invention.This means that even if the conditions in subsequent steps are greatly changed under such general hot rolling conditions, it is difficult to produce a copper alloy plate with a crystal orientation that satisfies I{220} / I{420}≤2.0, assuming that the X-ray diffraction intensity on the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and the X-ray diffraction intensity on the {420} crystal plane thereon is I{420}. For this reason, in the preferred embodiment of a method for producing a copper alloy plate according to the present invention, hot rolling is carried out with a rolling reduction of 90% or more in a temperature range of 900°C to 300°C during the hot rolling step, while a rolling reduction in a rolling path in a temperature range of 650°C or less (preferably from 650°C to 300°C) is 10% or more (preferably 10% to 35%, and even more preferably 10% to 20%).Furthermore, when hot-rolling the ingot, if the first rolling pass is performed at a temperature higher than 600°C, where recrystallization can easily occur, it is possible to break up the cast structure of the ingot to unify its components and structures. However, if hot-rolling the ingot is performed at a high temperature above 900°C, there is a possibility that cracks may form in parts, such as segregated sections of alloy components, where the melting point is lowered. Therefore, hot-rolling the ingot at a high temperature above 900°C is not preferable. (Intermediate cold rolling step)

[0037] In this cold rolling step, the rolling reduction is preferably not less than 50%, more preferably not less than 60%, and most preferably not less than 70%. (Intermediate annealing step)

[0038] In this intermediate annealing step, annealing is carried out at a temperature of 400°C to 800°C (preferably 400°C to 700°C). During this intermediate annealing step, the heat treatment is preferably performed by setting a holding time and a target temperature within a temperature range of 400°C to 800°C (preferably 400°C to 700°C and even more preferably 450°C to 650°C) such that the mean crystal grain size after annealing is not greater than 20 µm (preferably not greater than 18 µm and even more preferably not greater than 17 µm) and not less than 3 µm (preferably not less than 4 µm). Furthermore, the particle diameters of the recrystallized grains obtained by this annealing are varied according to the rolling reduction during cold rolling prior to annealing and according to their chemical composition.However, if the relationship between the annealing heat pattern and the mean crystal grain size has been previously determined experimentally with respect to each of the different alloys, it is possible to adjust the holding time and attainment temperature at a temperature of 400 to 800°C. In particular, in the case of the chemical composition of the copper alloy plate according to the present invention, it is possible to set suitable conditions for holding at a temperature of 400 to 800°C for a few seconds up to a few hours under heating conditions.

[0039] Furthermore, the intermediate cold rolling step and the intermediate annealing step can be repeated in this sequence. When repeating the intermediate cold rolling step and the intermediate annealing step, the final intermediate annealing (recrystallization annealing) step preferably involves heat treatment at a temperature no lower than that of other intermediate annealing processes. The heat treatment during the final intermediate annealing step is preferably carried out by setting a holding time and a target temperature within a temperature range of 400°C to 800°C (preferably 400°C to 700°C and even more preferably 450°C to 650°C), such that the mean crystal grain size after annealing is not greater than 20 µm (preferably not greater than 18 µm and even more preferably not greater than 17 µm) and not less than 3 µm (preferably not less than 4 µm). (Finishing cold rolling step)

[0040] Finish cold rolling is performed to improve the strength level of the copper alloy plate. If the roll reduction during finish cold rolling is too low, a rolling texture with the {220} orientation as the main orientation component develops as an increase in the roll reduction during finish cold rolling, even though the strength of the copper alloy plate is low. On the other hand, if the roll reduction during finish cold rolling is too high, the rolling texture on the {220} orientation is relatively too pronounced, making it impossible to obtain a crystal orientation that improves both strength and ductility. For this reason, the roll reduction during finish cold rolling must be 30% or less, preferably 5 to 29% and most preferably 10 to 28%. Such finish cold rolling makes it possible to maintain a crystal orientation that satisfies I{220} / I{420}≤2.0.Furthermore, the final thickness of the copper alloy plate is preferably in the range of about 0.02 mm to about 1.0 mm, more preferably in the range of 0.05 mm to 0.5 mm and most preferably in the range of 0.05 mm to 0.3 mm. (Low-temperature annealing step)

[0041] After cold rolling, low-temperature annealing can be performed to improve the stress corrosion cracking resistance and machinability of the copper alloy plate by reducing its residual stress, and to improve its stress relaxation resistance by reducing dislocations in vacancies and on the slip plane. Particularly in the case of a copper-zinc alloy, it is necessary to perform the low-temperature annealing at a temperature not exceeding 450°C, and this is preferably carried out at a heating temperature of 150 to 400°C (even more preferably at a temperature of 300 to 400°C) (a lower temperature than the annealing temperature used in the intermediate annealing step).This low-temperature annealing process improves the overall strength, stress corrosion cracking resistance, flexural ductility, and stress relaxation resistance of the copper alloy plate, and also increases its electrical conductivity. If the heating temperature is too high, the copper alloy plate softens quickly, leading to inconsistencies in properties, especially in batch or continuous systems. Conversely, if the heating temperature is too low, the desired improvement of the properties described above can still be achieved. The holding time at this temperature is preferably 5 seconds or more, and good results are generally obtained with a holding time of 1 hour. Examples

[0042] Examples of a copper alloy plate and a method for its manufacture according to the present invention are described in detail below. Examples 1-18 and comparative examples 1-5

[0043] The following were tested: a copper alloy with 20 wt% zinc, 0.79 wt% tin, 1.9 wt% silicon, 0.05 wt% phosphorus and the remainder being copper (Example 1); a copper alloy with 20 wt% zinc, 0.80 wt% tin, 1.9 wt% silicon, 0.10 wt% phosphorus and the remainder being copper (Example 2); a copper alloy with 20 wt% zinc, 0.79 wt% tin, 1.9 wt% silicon, 0.20 wt% phosphorus and the remainder being copper (Example 3); a copper alloy with 20 wt% zinc, 0.78 wt% tin, 1.1 wt% silicon, 0.05 wt% phosphorus and the remainder being copper (Example 4); a copper alloy with 20 wt% zinc, 0.80 wt% tin, 1.0 wt% silicon, 0.10 wt% phosphorus and the remainder being copper (Example 5), a copper alloy with 20 wt% zinc, 0.79 wt% tin, 1.0 wt% silicon, 0.20 wt% phosphorus and the remainder being copper (Example 6),a copper alloy with 20 wt% zinc, 0.79 wt% tin, 0.5 wt% silicon, 0.10 wt% phosphorus and the remainder being copper (Example 7), a copper alloy with 20 wt% zinc, 0.80 wt% tin, 0.5 wt% silicon, 0.20 wt% phosphorus and the remainder being copper (Example 8), a copper alloy with 20 wt% zinc, 0.78 wt% tin, 1.0 wt% silicon, 0.02 wt% phosphorus and the remainder being copper (Example 9), a copper alloy with 30 wt% zinc, 0.20 wt% tin, 1.8 wt% silicon, 0.10 wt% phosphorus and the remainder being copper (Example 10), a copper alloy with 20 wt% zinc, 2.10 wt% tin, 1.7 wt% silicon, 0.10 wt% phosphorus and the remainder being copper (Example 11), a copper alloy with 20 wt% zinc, 0.80 wt% tin, 1.7 wt% silicon, 0.10 wt% phosphorus and the remainder being copper (Example 12),a copper alloy with 20 wt% zinc, 0.80 wt% tin, 1.8 wt% silicon, 0.10 wt% phosphorus, 0.5 wt% nickel, and wherein the remainder is copper (Example 13), a copper alloy with 19 wt% zinc, 0.78 wt% tin, 1.8 wt% silicon, 0.10 wt% phosphorus, 0.5 wt% cobalt and wherein the remainder is copper (Example 14), a copper alloy with 20 wt% zinc, 0.77 wt% tin, 1.9 wt% silicon, 0.10 wt% phosphorus, 0.15 wt% iron, 0.07 wt% chromium, 0.08 wt% manganese and wherein the remainder is copper (Example 15), a copper alloy with 20 wt% zinc, 0.80 wt% tin, 1.7 wt% silicon, 0.10 wt% phosphorus, 0.08 wt% magnesium, 0.08 wt% aluminum, 0.1 wt% zirconium, 0.1 wt% titanium and the remainder being copper (Example 16), a copper alloy with 20 wt% zinc, 0.80 wt% tin, 1.7 wt% silicon, 0.10 wt% phosphorus, 0,0.5 wt% boron, 0.05 wt% lead, 0.1 wt% beryllium and the remainder being copper (Example 17), a copper alloy with 21 wt% zinc, 0.79 wt% tin, 1.9 wt% silicon, 0.10 wt% phosphorus, 0.05 wt% gold, 0.08 wt% silver, 0.08 wt% lead, 0.07 wt% cadmium and the remainder being copper (Example 18), a copper alloy with 20 wt% zinc, 0.80 wt% tin, 0.20 wt% phosphorus and the remainder being copper (Comparative Example 1), a copper alloy with 20 wt% zinc, 0.80 wt% tin and the remainder being copper (Comparative Example 2), a copper alloy with 20 wt% zinc, 0.79 wt% tin, 0.5 wt% silicon and the remainder being copper (comparative example 3), a copper alloy with 19 wt% zinc, 0.77 wt% tin, 1.0 wt% silicon and the remainder being copper (comparative example 4) or a copper alloy with 20 wt% zinc, 0.80 wt% tin, 1,9 wt% silicon, 0.10 wt% phosphorus and the remainder being copper (comparative example 5), molten.

[0044] Then the molten copper alloys were cast to obtain ingots, and castings measuring 100 mm × 100 mm × 100 mm were each cut from the ingots. Furthermore, the sum (6P+Si) of the silicon (Si) content and six times (6P) the phosphorus (P) content in each of the copper alloy plates was 2.2 wt.% (Example 1), 2.5 wt.% (Examples 2, 15, 18 and Comparative Example 5), 3.1 wt.% (Example 3), 1.4 wt.% (Example 4), 1.6 wt.% (Example 5), 2.2 wt.% (Example 6), 1.1 wt.% (Examples 7 and 9), 1.7 wt.% (Example 8), 2.4 wt.% (Examples 10, 13 and 14), 2.3 wt.% (Examples 11, 12, 16 and 17), 1.2 wt.% (Comparative Example 1), 0 wt.% (Comparative Example 2), 0.5 wt.% (Comparative Example 3), respectively. 1.0 wt.% (Comparative example 4.

[0045] After each casting was heated to 750°C for 30 minutes, it was hot-rolled in a temperature range of 900°C to 300°C to achieve a thickness of 10 mm (roll reduction = 90%). In a temperature range of 650°C to 300°C, hot rolling was carried out with a roll reduction of 15% (Examples 1-18) and 5% (Comparative Examples 1-5), respectively.

[0046] Each piece was then cold-rolled with a rolling reduction of 84%, resulting in a thickness of 1.60 mm, and then intermediately annealed by holding it at 500°C for 1 hour.

[0047] Each piece was then cold-rolled with a reduction of 76% to obtain a thickness of 0.38 mm (Examples 1-3, 10 and 13-18), with a reduction of 75% to obtain a thickness of 0.40 mm (Examples 4-6 and Comparative Example 4), with a reduction of 74% to obtain a thickness of 0.42 mm (Examples 7-9, 12 and Comparative Example 3), with a reduction of 78% to obtain a thickness of 0.35 mm (Example 11), with a reduction of 72% to obtain a thickness of 0.45 mm (Comparative Examples 1-2), and with a reduction of 77% to obtain a thickness of 0.37 mm (Comparative Example 5). and then (finally) intermediate annealed (recrystallization annealed) by heating at 500°C (Examples 1-3, 5-10, 15-18, Comparative Examples 1 and 3-4), 550°C (Examples 4 and 11), 600°C (Examples 12-14), 525°C (Comparative Example 2) respectively.350°C (comparative example 5) is held for 10 minutes.

[0048] Each piece was then cold-rolled with a roll reduction of 21% to obtain a thickness of 0.30 mm (Examples 1-3, 10 and 13-18), with a roll reduction of 25% to obtain a thickness of 0.30 mm (Examples 4-6 and Comparative Example 4), with a roll reduction of 27% to obtain a thickness of 0.30 mm (Examples 7-9 and 12, Comparative Example 3), with a roll reduction of 15% to obtain a thickness of 0.30 mm (Example 11), with a roll reduction of 33% to obtain a thickness of 0.30 mm (Comparative Examples 1-2), and with a roll reduction of 15% to obtain a thickness of to obtain 0.31 mm (Comparison Example 5) and then low-temperature annealed by holding at 350°C (Examples 1-3, 7-8, 10-18 and Comparison Example 3), 300°C (Examples 4, 9, Comparison Examples 1-2 and 5) and 325°C (Examples 5-6 and Comparison Example 4) for 30 minutes.

[0049] Then, samples were cut from the copper alloy plates thus obtained in Examples 1-18 and the comparative examples 1-5, and the mean crystal grain size of the crystal grain structure, the X-ray diffraction intensity, the electrical conductivity, the tensile strength (0.2% yield strength and tensile strength), the stress relaxation resistance, the stress corrosion cracking resistance, and the machinability for bending were investigated as follows.

[0050] The mean crystal grain size of the copper alloy plate's crystal grain structure was measured using the sectioning method based on JIS H0501 by observing the surface (rolled surface) of the copper alloy plate with an optical microscope after polishing and etching. The results showed mean crystal grain sizes of 5 µm (Examples 1-10, 13-18 and comparison examples 1-4), 6 µm (Example 11), 15 µm (Example 12), and 2 µm (comparison example 5), respectively.

[0051] The intensity of X-ray diffraction (the integrated intensity of X-ray diffraction) was measured by measuring the integrated intensity I{220} of the diffraction peak on the {220} plate and the integrated intensity I{420} of the diffraction peak on the {420} plane with respect to the surface (rolled surface) of the sample using an X-ray diffractometer (XRD) (RINT 2000, manufactured by Rigaku Corporation) with a copper tube under conditions including a tube voltage of 40 kV and a tube current of 20 mA. These measured values ​​were used to obtain the X-ray diffraction intensity ratio I{220} / I{420}. As a result, the intensity ratio I{220} / I{420} of the X-ray diffraction was 1.6 (Examples 1-4, 6, 10-11, 13-14 and 17), 1.7 (Examples 5, 8 and 12), 1.8 (Examples 7 and 9), 1.5 (Examples 15-16 and 18), 2.6 (Comparison Example 1), 2.7 (Comparison Example 2), 2.5 (Comparison Examples 3-4) and 2.4 (Comparison Example 5).

[0052] The electrical conductivity of the copper alloy plate was measured according to the electrical conductivity measurement method based on JIS H0505. As a result, the electrical conductivity of the copper alloy plate was 10.1% IACS (Example 1), 9.6% IACS (Example 2), 9.3% IACS (Example 3), 14.2% IACS (Example 4), 13.4% IACS (Example 5), 13.0% IACS (Example 6), 16.0% IACS (Example 7), 15.8% IACS (Example 8), 14.2% IACS (Example 9), 14.0% IACS (Example 10), 8.9% IACS (Example 11), 9.6% IACS (Example 12), 10.4% IACS (Example 13), 10.1% IACS (Example 14), 9.6% IACS (Example 15), 9.8% IACS (Example 16), 9.5% IACS (Example 17), 9.6% IACS (Example 18), 24.1% IACS (Comparison Example 1), 25.5% IACS (Comparison Example 2), 16.0% IACS (Comparison Example 3), 13.0% IACS (Comparison Example 4) or 9.0% IACS (Comparison Example) 5.

[0053] To evaluate the tensile strength, which is one of the mechanical properties of the copper alloy plate, three test pieces (No. 5 test pieces based on JIS Z2201) were cut from each of the copper alloy plates for tensile testing in the LD (rolling) directions. The tensile test was then performed on each of the test pieces according to JIS Z2241 to determine the mean tensile strength in the LD directions and the mean 0.2% proof stress in the LD directions.As a result, the 0.2% yield strengths and tensile strengths in the LD directions were 524 MPa and 639 MPa (Example 1), 531 MPa and 640 MPa (Example 2), 535 MPa and 645 MPa (Example 3), 526 MPa and 585 MPa (Example 4), 532 MPa and 616 MPa (Example 5), 530 MPa and 600 MPa (Example 6), 545 MPa and 620 MPa (Example 7), 549 MPa and 612 MPa (Example 8), 576 MPa and 620 MPa (Example 9), 550 MPa and 650 MPa (Example 10), 620 MPa and 714 MPa (Example 11), 535 MPa and 610 MPa (Example 12), 534 MPa and 638 MPa (Example 13), 535 MPa and 640 MPa (Example 14), 532 MPa and 641 MPa (Example 15), 530 MPa and 635 MPa (Example 16), 530 MPa and 632 MPa (Example 17), 538 MPa and 640 MPa (Example 18), 533 MPa and 587 MPa (Comparison Example 1), 515 MPa and 600 MPa (Comparison Example 2), 570 MPa and 621 MPa (Comparison Example 3), 591 MPa and 645 MPa (Comparison Example 4) or 520 MPa and 639 MPa (Comparison Example 5).

[0054] The stress relaxation resistance of the copper alloy plate was evaluated by the cantilever bolt stress relaxation test prescribed in JEITA EMAS-1011. Specifically, a test piece (60 mm long x 10 mm wide) was cut from the copper alloy plate such that the longitudinal directions of the test piece were the LD directions (rolling directions of the copper alloy plate), while the transverse directions were the TD directions (directions perpendicular to the rolling and thicknessing directions of the copper alloy plate).One end section of the specimen was fixed in its longitudinal directions to a deflection load clamping device of the cantilever bolt type, and the other end section was fixed in its longitudinal directions in such a way that a load stress corresponding to 80% of its 0.2% proof strength was applied at a position corresponding to a span of 30 mm at its other end section (by means of a deflection load bolt), such that the thickness directions of the specimen were deflection directions. After this specimen was held at 150°C for 500 hours, the deflection of the specimen was measured. A stress relaxation rate (%) was calculated from the variability rate of the deflection to evaluate the stress relaxation resistance of the copper alloy plate.As a result, the stress relaxation rate was 20% (Examples 1-2, 5-6, 10 and 14), 19% (Examples 3 and 15-16), 21% (Examples 4 and 7), 18% (Examples 8-9, 12 and 17), 16% (Example 11), 17% (Examples 13 and 18), 40% (Comparison Examples 1 and 5) and 45% (Comparison Example 2).

[0055] To assess the stress corrosion cracking resistance of the copper alloy plate, a 10 mm wide test piece cut from the copper alloy plate was bent into an arc such that the surface tension in the central part of the test piece, in its longitudinal directions, was 80% of the 0.2% yield strength. In this state, the test piece was kept at 25°C in a desiccator containing 3 wt% ammonia solution. Cracks were observed on the 10 mm wide test piece hourly using an optical microscope at 100x magnification to evaluate the stress corrosion cracking resistance.As a result, cracks appeared after 160 hours (Example 1), 199 hours (Example 2), 324 hours (Example 3), 135 hours (Example 4), 165 hours (Example 5), 250 hours (Example 6), 124 hours (Example 7), 150 hours (Example 8), 135 hours (Example 9), 185 hours (Example 10), 201 hours (Example 11), 189 hours (Example 12), 190 hours (Example 13), 200 hours (Example 14), 190 hours (Example 15), 205 hours (Example 16), 192 hours (Example 17), 199 hours (Example 18), 40 hours (Comparison Example 1), 30 hours (Comparison Example 2), 92 hours (Comparison Example 3), 95 hours (comparative example 4) or 180 hours (comparative example 5) were observed.The time during which cracks were observed in the copper alloy plate was 32 times (Example 1), 40 times (Example 2), 65 times (Example 3), 27 times (Example 4), 33 times (Example 5), 50 times (Example 6), 25 times (Example 7), 30 times (Example 8), 27 times (Example 9), 37 times (Example 10), 40 times (Example 11), 38 times (Example 12), 38 times (Example 13), 40 times (Example 14), 38 times (Example 15), 41 times (Example 16), 38 times (Example 17), 40 times (Example 18), 8 times (Comparison Example 1), 6 times (Comparison Example 2), 18 times (Comparison Example 3), 19 times (Comparison example 4) or 35 times (Comparison example 5) as long as the time (5 hours) in a plate of commercially available first-class brass (C2600-SH).

[0056] To evaluate the bendability of the copper alloy sheet, a bending test piece (width = 10 mm) was cut from the copper alloy sheet, such that the longitudinal directions of the bending test piece were the directions TD (directions perpendicular to the rolling and thickness directions of the copper alloy sheet). Then, with respect to the bending test piece, the 90° W bending test according to JIS H3130 was performed, such that the bending axis of the bending test piece ran in the directions LD (the rolling directions of the copper alloy sheet) (Bad Way bending (BW bending)). With respect to the bent part after this test, the surface and cross-section of the bent piece were observed at a magnification of 100x using an optical microscope to determine a minimum bending radius R at which no cracks were observed. The minimum bending radius R was then divided by the thickness t to derive the ratio R / t.As a result, the ratio R / t was 0.3 or less (Examples 1 and 9), 0.6 (Examples 2-3, 5-6, 8, 11-12, 14, 18 and Comparative Example 5), 0.3 (Examples 4, 7, 10, 13 and 15-17), 1.0 (Comparative Examples 1-2) and 0.8 (Comparative Examples 3-4), respectively.

[0057] The manufacturing conditions and properties of the copper alloy plates in these examples and comparative examples are shown in Tables 1 to 4. Table 1 Chemical composition (wt.%) Cu Zn Sn Si P Other elements 6P+Si Example 1 rest 20 0,79 1,9 0,05 - 2,2 Example 2 rest 20 0,80 1,9 0,10 - 2,5 Example 3 rest 20 0,79 1,9 0,20 - 3,1 Example 4 rest 20 0,78 1,1 0,05 - 1,4 Example 5 rest 20 0,80 1,0 0,10 - 1,6 Example 6 rest 20 0,79 1,0 0,20 - 2,2 Example 7 rest 20 0,79 0,5 0,10 - 1,1 Example 8 rest 20 0,80 0,5 0,20 - 1,7 Example 9 rest 20 0,78 1,0 0,02 - 1,1 Example 10 rest 30 0,20 1,8 0,10 - 2,4 Example 11 rest 20 2,10 1,7 0,10 - 2,3 Example 12 rest 20 0,80 1,7 0,10 - 2,3 Example 13 rest 20 0,80 1,8 0,10 Ni0.5 2,4 Example 14 rest 19 0,78 1,8 0,10 CO0.5 2,4 Example 15 rest 20 0,77 1,9 0,10 Fe0.15,Cr0.07,Mn0.08 2,5 Example 16 rest 20 0,80 1,7 0,10 Mg0.08, Al0.08, Zr0.1, Ti0.1 2,3 Example 17 rest 20 0,80 1,7 0,10 B0,05,Pb0,05,Be0,1 2,3 Example 18 rest 21 0,79 1,9 0,10 Au0.05,Ag0.08,Pb0.08,Cd0.07 2,5 See 1 rest 20 0,80 0 0,20 - 1,2 See 2 rest 20 0,80 0 0 - 0 See 3 rest 20 0,79 0,5 0 - 0,5 See 4 rest 19 0,77 1,0 0 - 1,0 See 5 rest 20 0,80 1,9 0,10 - 2,5 Table 2 Rolling reduction (%) at 650°C or lower during hot rolling Final intermediate annealing (°Cx min,) Roll reduction (%) during finish hot rolling Temperature (°C) during low-temperature annealing Example 1 15 500×10 21 350 Example 2 15 500×10 21 350 Example 3 15 500×10 21 350 Example 4 15 550×10 25 300 Example 5 15 500×10 25 325 Example 6 15 500×10 25 325 Example 7 15 500×10 27 350 Example 8 15 500×10 27 350 Example 9 15 500×10 27 300 Example 10 15 500×10 21 350 Example 11 15 550×10 15 350 Example 12 15 600×10 27 350 Example 13 15 600×10 21 350 Example 14 15 600×10 21 350 Example 15 15 500×10 21 350 Example 16 15 500×10 21 350 Example 17 15 500×10 21 350 Example 18 15 500×10 21 350 See 1 5 500×10 33 300 See 2 5 525×10 33 300 See 3 5 500×10 27 350 See 4 5 500×10 25 325 See 5 5 350×10 15 300 Table 3 Average crystal grain size (µm) Ratio of X-ray diffraction intensity I{220} / I{420} Example 1 5 1,6 Example 2 5 1,6 Example 3 5 1,6 Example 4 5 1,6 Example 5 5 1,7 Example 6 5 1,6 Example 7 5 1,8 Example 8 5 1,7 Example 9 5 1,8 Example 10 5 1,6 Example 11 6 1,6 Example 12 15 1,7 Example 13 5 1,6 Example 14 5 1,6 Example 15 5 1,5 Example 16 5 1,5 Example 17 5 1,6 Example 18 5 1,5 See 1 5 2,6 See 2 5 2,7 See 3 5 2,5 See 4 5 2,5 See 5 2 2,4 Table 4 Conductivity (%IACs) 0.2% yield strength (MPa) Tensile strength (MPa) Voltage relaxation rate (%) Stress crack corrosion resistance Bending processability (R / t) Time (h) ratio to C2600 Example 1 10,1 524 639 20 160 32 0.3 orless Example 2 9,6 531 640 20 199 40 0,6 Example 3 9,3 535 645 19 324 65 0,6 Example 4 14,2 526 585 21 135 27 0,3 Example 5 13,4 532 616 20 165 33 0,6 Example 6 13,0 530 600 20 250 50 0,6 Example 7 16,0 545 620 21 124 25 0,3 Example 8 15,8 549 612 18 150 30 0,6 Example 9 14,2 576 620 18 135 27 0.3 or less Example 10 14,0 550 650 20 185 37 0,3 Example 11 8,9 620 714 16 201 40 0,6 Example 12 9,6 535 610 18 189 38 0,6 Example 13 10,4 534 638 17 190 38 0,3 Example 14 10,1 535 640 20 200 40 0,6 Example 15 9,6 532 641 19 190 38 0,3 Example 16 9,8 530 635 19 205 41 0,3 Example 17 9,5 530 632 18 192 38 0,3 Example 18 9,6 538 640 17 199 40 0,6 See 1 24,1 533 587 40 40 8 1,0 See 2 25,5 515 600 45 30 6 1,0 See 3 16,0 570 621 - 92 18 0,8 See 4 13,0 591 645 - 95 19 0,8 See 5 9,0 520 639 40 180 35 0,6

[0058] Tables 1-4 show that it is possible to supply a copper alloy plate with excellent bending machinability, excellent stress corrosion cracking resistance, and excellent stress relaxation resistance while maintaining its high strength if the copper alloy plate has a chemical composition containing 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus, and the remainder being copper and unavoidable impurities, where the sum of the silicon content and six times the phosphorus content equals 1 wt.-% or more, and if the copper alloy plate has a crystal orientation that satisfies I{220} / I{420}≤2.0, assuming that the X-ray diffraction intensity at the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and that the X-ray diffraction intensity at the {420} crystal plane on it is I{420}, as with the copper alloy plates in Examples 1 - 18.

[0059] It can also be seen that the stress corrosion cracking resistance, the stress relaxation resistance and the machinability of a copper alloy plate are deteriorated when the copper alloy plate does not contain silicon and has a crystal orientation that satisfies I{220} / I{420}>2.0 by hot rolling with a rolling reduction of less than 10% in a rolling path in a temperature range of 650°C or less, as with the copper alloy plates in comparison examples 1 and 2.

[0060] It can also be seen that the stress corrosion cracking resistance and the machinability of a copper alloy plate are deteriorated when the copper alloy plate does not contain phosphorus and has a crystal orientation that satisfies I{220} / I{420}>2.0 by hot rolling with a rolling reduction of less than 10% in a rolling path in a temperature range of 650°C or less, as with the copper alloy plates in comparison examples 3 and 4.

[0061] Furthermore, it can be seen that the stress relaxation resistance of a copper alloy plate deteriorates when the copper alloy plate has a crystal orientation that satisfies I{220} / I{420}>2.0 by hot rolling with a rolling reduction of less than 10% in a rolling path in a temperature range of 650°C or less, and when the copper alloy plate has a mean crystal grain size of 2 µm by performing the finish intermediate annealing at a temperature of less than 400°C, as with the copper alloy plate in Comparative Example 5.

Claims

[1] Copper alloy plate having a chemical composition comprising 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus and the remainder being copper and unavoidable impurities, wherein the sum of the silicon content and six times the phosphorus content is 1 wt.% or more, and wherein the copper alloy plate has a crystal orientation that satisfies I{220} / I{420}≤2,0 under the assumption that the X-ray diffraction intensity at the {220} crystal plane on the plate surface of the copper alloy plate is I{220} and that the X-ray diffraction intensity at the {420} crystal plane thereon is I{420}. [2] Copper alloy plate according to claim 1, wherein the chemical composition of the copper alloy plate further comprises 1 wt.% or less nickel or cobalt. [3] Copper alloy plate according to claim 1, wherein the chemical composition of the copper alloy plate further comprises one or more elements selected from the group consisting of iron, chromium, magnesium, aluminium, boron, zirconium, titanium, manganese, gold, silver, lead, cadmium and beryllium, wherein the total amount of these elements is 3 wt.% or less. [4] Copper alloy plate according to claim 1, having a mean crystal grain size of 3 to 20 µm. [5] Copper alloy plate according to claim 1, having a tensile strength of not less than 550 MPa. [6] Copper alloy plate according to claim 1, having a 0.2% proof strength of not less than 500 MPa. [7] Copper alloy plate according to claim 1, having an electrical conductivity of not less than 8%IACS. [8] Method for producing a copper alloy plate, the method comprising the steps: Melting and casting of raw materials of a copper alloy having a chemical composition containing 17 to 32 wt.% zinc, 0.1 to 4.5 wt.% tin, 0.5 to 2.0 wt.% silicon, 0.01 to 0.3 wt.% phosphorus and, as a remainder, copper and unavoidable impurities, wherein the sum of the silicon content and six times the phosphorus content is 1 wt.% or more; Hot rolling of the cast copper alloy with a rolling reduction of 90% or more in a temperature range of 900°C to 300°C, wherein the hot rolling with a rolling reduction of 10% or more is carried out in a rolling path in a temperature range of 650°C or less; Intermediate cold rolling of the hot-rolled copper alloy; Intermediate annealing of the cold-rolled copper alloy at a temperature of 400 to 800°C; Finish cold rolling of the intermediate annealed copper alloy with a rolling reduction of 30% or less; and Low-temperature annealing of the finished cold-rolled copper alloy at a temperature of 450°C or lower. [9] Method for producing a copper alloy plate according to claim 8, wherein the rolling reduction in the rolling path in the temperature range of 650°C or less during hot rolling is 35% or less. [10] Method for producing a copper alloy plate according to claim 8, wherein the intermediate annealing is carried out by a heat treatment in which a holding time and a target temperature are set in a temperature range of 400°C to 800°C such that the copper alloy has a mean crystal grain size of 3 to 20 µm after the intermediate annealing. [11] Method for producing a copper alloy plate according to claim 8, wherein the chemical composition of the copper alloy plate further comprises 1 wt.% or less nickel or cobalt. [12] Method for producing a copper alloy plate according to claim 8, wherein the chemical composition of the copper alloy plate further comprises one or more elements selected from the group consisting of iron, chromium, magnesium, aluminium, boron, zirconium, titanium, manganese, gold, silver, lead, cadmium and beryllium, wherein the total amount of these elements is 3 wt.% or less. [13] Method for producing a copper alloy plate according to claim 8, wherein the intermediate cold rolling and the intermediate annealing are repeated alternately several times. [14] Terminal block, the material of which is a copper alloy plate according to claim 1.