Copper alloy material, resistive material for resistor, and resistor

Abstract

To provide a copper alloy material, a resistance material for a resistor, and a resistor which are excellent in formability and electrical characteristics.SOLUTION: The copper alloy material has an alloy composition comprising, by mass, 21.0 to 35.0% Mn and 6.5 to 17.0% Ni, and the balance Cu with inevitable impurities, wherein the ratio of the major axis to the minor axis of the crystal grain size in the cross section is 2.0 to 5.0, and the Vickers hardness (HV) is 160 to 250.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a copper alloy material, a resistive material for a resistor, and a resistor. [Background technology]

[0002] When copper alloy materials used for resistors contain high concentrations of Mn and Ni, the properties as resistor materials improve, and the strength and ductility also tend to increase due to solid solution strengthening.

[0003] Resistance materials are generally processed into plates and then punched using a press. As mentioned above, copper alloys containing high concentrations of Mn and Ni have high strength and ductility, so when punching copper alloys, the dies are prone to wear.

[0004] To address these problems, Patent Document 1 describes a resistance alloy containing predetermined amounts of manganese and nickel, with the balance being copper. In the resistance alloy of Patent Document 1, the mass fraction of the manganese and the mass fraction of the nickel are selected so that the resistance alloy has a low thermoelectric power relative to copper of less than ±1 μV / K at 20°C. Patent Document 2 describes a Cu alloy material containing a predetermined amount of Mn, with the balance being Cu and unavoidable impurities, having a Vickers hardness of 150 HV or more and an absolute value of a temperature coefficient of resistance of 50 ppm / K or less at 20°C to 150°C. However, Patent Documents 1 and 2 do not disclose or even consider any aspect of suppressing deformation that occurs during press working or etching of the copper alloy materials for resistors described in these documents. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6467408 [Patent Document 2] Patent No. 6471494 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a copper alloy material, a resistance material for a resistor, and a resistor that are excellent in formability and electrical properties. [Means for solving the problem]

[0007] [1] A copper alloy material having an alloy composition containing 21.0 mass% or more and 35.0 mass% or less of Mn, 6.5 mass% or more and 17.0 mass% or less of Ni, and the balance being Cu and unavoidable impurities, in which the ratio of the major axis to the minor axis of the crystal grain in the cross section is 2.0 or more and 5.0 or less, and the Vickers hardness (HV) is 160 or more and 250 or less. [2] The copper alloy material according to the above [1], having a work-affected layer having an average thickness of 0.2 μm or more and 2.0 μm or less on the rolled surface. [3] The copper alloy material according to [1] or [2] above, wherein the elongation measured in accordance with JIS Z 2241 is 3% or more and 15% or less. [4] The copper alloy material according to any one of the above [1] to [3], wherein the spring limit is 500 MPa or more. [5] The copper alloy material according to any one of the above [1] to [4], wherein the alloy composition further contains 0.01 mass % or more and 2.00 mass % or less of Co. [6] The copper alloy material according to any one of the above [1] to [5], wherein the alloy composition further contains at least one element selected from the group consisting of 0.01% by mass or more and 0.50% by mass or less of Fe, 0.01% by mass or more and 3.00% by mass or less of Sn, 0.01% by mass or more and 5.00% by mass or less of Zn, 0.01% by mass or more and 0.50% by mass or less of Cr, 0.01% by mass or more and 0.50% by mass or less of Ag, 0.01% by mass or more and 1.00% by mass or less of Al, 0.01% by mass or more and 0.50% by mass or less of Mg, 0.01% by mass or more and 0.50% by mass or less of Si, and 0.01% by mass or more and 0.50% by mass or less of P. [7] A resistive material for a resistor, comprising the copper alloy material according to any one of the above [1] to [6]. [8] A resistor, which is a shunt resistor or a chip resistor, comprising the resistive material for resistors according to [7] above. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a copper alloy material, a resistive material for a resistor, and a resistor that are excellent in formability and electrical properties. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of a work-affected layer provided on the surface of a copper alloy material. [Figure 2] FIG. 2 is an SEM image of a cross section of the copper alloy material produced in Example 1, the cross section including the direction parallel to the rolling direction and the normal direction to the rolling surface. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiments will be described in detail below.

[0011] As a result of extensive research into copper alloy materials, the present inventors have found that copper alloy materials have excellent formability and electrical properties when they have a predetermined alloy composition, a ratio of the major axis to the minor axis of the crystal grain size in a cross section that is within a predetermined range, and a Vickers hardness (HV) that is within a predetermined range, and have completed the present disclosure based on this finding.

[0012] The copper alloy material according to the embodiment has an alloy composition containing 21.0 to 35.0 mass% of Mn, 6.5 to 17.0 mass% of Ni, and the balance being Cu and unavoidable impurities. In a cross section of the copper alloy material, the ratio of the major axis to the minor axis of the crystal grain is 2.0 to 5.0, and the Vickers hardness (HV) is 160 to 250.

[0013] First, the alloy composition of the copper alloy material will be described.

[0014] The copper alloy material of the above embodiment contains 21.0% by mass or more and 35.0% by mass or less of Mn and 6.5% by mass or more and 17.0% by mass or less of Ni, and the balance consists of Cu and unavoidable impurities.

[0015] <Mn: 21.0% by mass or more and 35.0% by mass or less> Mn (manganese) is an element that increases the volume resistivity ρ of the copper alloy material. In order to exert this effect and obtain a homogeneous copper alloy material, the content of Mn is 21.0% by mass or more. On the other hand, when the content of Mn exceeds 35.0% by mass, in terms of manufacturing, the melting point decreases, narrowing the temperature range in which hot working is possible. In addition, there is an increase in strength due to Mn solid solution, making rolling itself difficult. Therefore, for the content of Mn, the lower limit is 21.0% by mass or more, preferably 22.0% by mass or more, more preferably 23.0% by mass or more, further preferably 24.0% by mass or more, most preferably 25.0% by mass or more, and the upper limit is 35.0% by mass or less.

[0016] <Ni: 6.5% by mass or more and 17.0% by mass or less> Ni (nickel) is an element that adjusts the thermoelectromotive force (EMF) of the copper alloy material with respect to copper in the positive direction. Therefore, by containing Ni together with Mn, which has the property of making the thermoelectromotive force with respect to copper a negative value, the absolute value of the thermoelectromotive force of the copper alloy material can be reduced. In order to exert this effect, the content of Ni is 6.5% by mass or more. On the other hand, when the content of Ni exceeds 17.0% by mass, it becomes difficult to obtain a uniform metal structure, and there is a risk that the volume resistivity, thermoelectromotive force with respect to copper, etc. may change depending on the part of the copper alloy material. Therefore, for the content of Ni, the lower limit is 6.5% by mass or more, the upper limit is 17.0% by mass or less, preferably 12.0% by mass or less, and more preferably 9.0% by mass or less.

[0017] <Minor components of the copper alloy material> The alloy composition of the copper alloy material can further contain the following elements. That is, in addition to Mn and Ni which are essential basic components, the copper alloy material can further contain the following elements as optional components, i.e., sub-components.

[0018] <Co: 0.01 mass% or more and 2.00 mass% or less> Co (cobalt) is an element that adjusts the thermal electromotive force of the copper alloy material with respect to copper in the positive direction. In order to effectively exert this effect, the content of Co is preferably 0.01 mass% or more. On the other hand, since it is easier to obtain a more uniform metal structure and further suppress the variation in electrical performance, the content of Co is preferably 2.00 mass% or less. Thus, the alloy composition of the copper alloy material preferably further contains Co in an amount of 0.01 mass% or more and 2.00 mass% or less. Also, Co is an expensive element, but unlike Fe described later, if it is within the range of 2.00 mass% or less, there is an advantage that the electrical characteristics of the copper alloy material are less likely to vary over time.

[0019] <Fe: 0.01 mass% or more and 0.50 mass% or less> Fe (iron) is an element that adjusts the thermal electromotive force of the copper alloy material with respect to copper in the positive direction. In order to effectively exert this effect, the content of Fe is preferably 0.01 mass% or more. On the other hand, since it is easier to obtain a more uniform metal structure and further suppress the variation in electrical performance, the content of Fe is preferably 0.50 mass% or less. Thus, the alloy composition of the copper alloy material preferably further contains Fe in an amount of 0.01 mass% or more and 0.50 mass% or less. Further, from the viewpoint of suppressing the variation in electrical characteristics when the copper alloy material is used over a long period, enhancing the stability of the electrical characteristics of the copper alloy material against heat, etc., and thereby enhancing the reliability when the copper alloy material is used as a resistance material, etc., over a long period, the content of Fe is more preferably 0.30 mass% or less, and even more preferably 0.2 mass% or less.

[0020] <Sn: 0.01 mass% or more and 3.00 mass% or less> When the content of Sn (tin) is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the content of Sn is 3.00% by mass or less, it is possible to further prevent the deterioration of manufacturability due to embrittlement of the copper alloy material. Therefore, the content of Sn is preferably 0.01% by mass or more and 3.00% by mass or less.

[0021] <Zn: 0.01% by mass or more and 5.00% by mass or less> When the content of Zn (zinc) is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the content of Zn is 5.00% by mass or less, it is possible to further improve the stability of the electrical performance of the resistor, such as volume resistivity, temperature coefficient of resistance, and thermoelectromotive force against copper. Therefore, the content of Zn is preferably 0.01% by mass or more and 5.00% by mass or less.

[0022] <Cr: 0.01% by mass or more and 0.50% by mass or less> When the content of Cr (chromium) is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the content of Cr is 0.50% by mass or less, it is possible to further improve the stability of the electrical performance of the resistor, such as volume resistivity, temperature coefficient of resistance, and thermoelectromotive force against copper. Therefore, the content of Cr is preferably 0.01% by mass or more and 0.50% by mass or less.

[0023] <Ag: 0.01% by mass or more and 0.50% by mass or less> When the content of Ag (silver) is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the content of Ag is 0.50% by mass or less, it is possible to further improve the stability of the electrical performance of the resistor, such as volume resistivity, temperature coefficient of resistance, and thermoelectromotive force against copper. Therefore, the content of Ag is preferably 0.01% by mass or more and 0.50% by mass or less.

[0024] <Al: 0.01% by mass or more and 1.00% by mass or less> When the aluminum (Al) content is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the Al content is 1.00% by mass or less, it is possible to further reduce the occurrence of a decrease in productivity due to embrittlement of the copper alloy material. Therefore, the Al content is preferably 0.01% by mass or more and 1.00% by mass or less.

[0025] <Mg: 0.01% by mass or more and 0.50% by mass or less> When the magnesium (Mg) content is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the Mg content is 0.50% by mass or less, it is possible to further reduce the occurrence of a decrease in productivity due to embrittlement of the copper alloy material. Therefore, the Mg content is preferably 0.01% by mass or more and 0.50% by mass or less.

[0026] <Si: 0.01% by mass or more and 0.50% by mass or less> When the silicon (Si) content is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the Si content is 0.50% by mass or less, it is possible to further reduce the occurrence of a decrease in productivity due to embrittlement of the copper alloy material. Therefore, the Si content is preferably 0.01% by mass or more and 0.50% by mass or less.

[0027] <P: 0.01% by mass or more and 0.50% by mass or less> When the phosphorus (P) content is 0.01% by mass or more, the volume resistivity ρ of the copper alloy material can be efficiently adjusted. On the other hand, when the P content is 0.50% by mass or less, it is possible to further reduce the occurrence of a decrease in productivity due to embrittlement of the copper alloy material. Therefore, the P content is preferably 0.01% by mass or more and 0.50% by mass or less.

[0028] Thus, the alloy composition of the copper alloy material preferably further contains at least one element selected from the group consisting of 0.01% by mass or more and 0.50% by mass or less of Fe, 0.01% by mass or more and 3.00% by mass or less of Sn, 0.01% by mass or more and 5.00% by mass or less of Zn, 0.01% by mass or more and 0.50% by mass or less of Cr, 0.01% by mass or more and 0.50% by mass or less of Ag, 0.01% by mass or more and 1.00% by mass or less of Al, 0.01% by mass or more and 0.50% by mass or less of Mg, 0.01% by mass or more and 0.50% by mass or less of Si, and 0.01% by mass or more and 0.50% by mass or less of P. In this case, it is preferable that Co within the above range is further contained.

[0029] In addition, in order to fully achieve the above-mentioned effects, it is preferable that the alloy composition of the copper alloy material further contains at least one element selected from the group consisting of Fe, Sn, Zn, Cr, Ag, Al, Mg, Si, and P in a total amount of 0.01 mass% or more. On the other hand, in order to further improve the uniformity of the metal structure and further suppress the embrittlement of the copper alloy material, it is preferable that the alloy composition of the copper alloy material further contains at least one element selected from the group consisting of Fe, Sn, Zn, Cr, Ag, Al, Mg, Si, and P in a total amount of 5.00 mass% or less. In this case, it is preferable that Co be further contained within the above range.

[0030] <Remainder: Cu and unavoidable impurities> The remainder other than the above-mentioned components is Cu (copper) and inevitable impurities. The inevitable impurities are inevitably mixed in during the manufacturing process, and depending on the content, they can cause a deterioration in one or more of the formability and electrical properties of the copper alloy material. Therefore, the lower the content of the inevitable impurities, the better. Examples of inevitable impurities include elements such as S (sulfur), O (oxygen), and C (carbon). The upper limit of the content of the inevitable impurities is preferably less than 0.05 mass% for each of the elements, and preferably less than 0.10 mass% in total for the elements.

[0031] Furthermore, the ratio of the major axis to the minor axis of the crystal grain in the cross section of the copper alloy material (hereinafter also referred to as the aspect ratio) is 2.0 or more and 5.0 or less. The aspect ratio of the crystal grain in the cross section is the ratio of the major axis to the minor axis of the recrystallized grain of the alloy.

[0032] Here, when the copper alloy material is a plate strip, the cross section of the copper alloy material is a cross section including a rolling parallel direction and a rolling surface normal direction, and when the copper alloy material is a wire rod, the cross section of the copper alloy material is a parallel cross section passing through the wire center with respect to the wiredrawing direction.

[0033] If the aspect ratio of the crystal grain size in the cross section of the copper alloy material is less than 2.0, the copper alloy material is not sufficiently processed, and the copper alloy material warps during press working or etching, making it difficult to finish the copper alloy material into the desired shape. On the other hand, if the aspect ratio exceeds 5.0, a large amount of processing strain is introduced into the copper alloy material, which may make the copper alloy material more susceptible to material fracture during processing. Furthermore, when a resistor including a resistive material for resistors made of a copper alloy material is exposed to high temperatures, the release of the introduced strain causes a change in the shape of the copper alloy material, which causes the electrical properties of the copper alloy material to become unstable.

[0034] The major axis of the crystal grain size in the cross section of the copper alloy material, when the copper alloy material is a plate strip, corresponds to the long side dimension of a rectangle when one crystal grain is surrounded by a rectangle whose sides are a line parallel to the rolling direction of the copper alloy material and a line normal to the rolling surface of the copper alloy material, and when the copper alloy material is a wire rod, corresponds to the long side dimension of a rectangle when one crystal grain is surrounded by a rectangle whose sides are a line along the wiredrawing direction of the copper alloy material and a line perpendicular to the wiredrawing direction. Furthermore, the minor axis of the crystal grain size in the cross section of the copper alloy material, when the copper alloy material is a plate strip, corresponds to the short side dimension of a rectangle when one crystal grain is surrounded by a rectangle whose sides are a line parallel to the rolling direction of the copper alloy material and a line normal to the rolling surface, and when the copper alloy material is a wire rod, corresponds to the short side dimension of a rectangle when one crystal grain is surrounded by a rectangle whose sides are a line along the wiredrawing direction of the copper alloy material and a line perpendicular to the wiredrawing direction.

[0035] The major and minor axes of the crystal grain size in the cross section of a copper alloy material do not particularly contribute to the properties of the copper alloy material. However, when the average value of the major and minor axes of the crystal grain size in the cross section of the copper alloy material is considered to be the average crystal grain size, for example, if the average crystal grain size is less than 3.0 μm, processed structures are mixed into the copper alloy material, and if the average crystal grain size is more than 20.0 μm, the copper alloy material is susceptible to the adverse effects of grain coarsening. Furthermore, if the average crystal grain size is outside the above range, it becomes difficult to control the above aspect ratio and the processed-affected layer described below in terms of the structure, and the elongation and spring limit value (both described below) in terms of the properties. The crystal grain size is determined by the final heat treatment in the manufacturing method of the copper alloy material, but can usually be sufficiently controlled by adopting general manufacturing conditions.

[0036] Furthermore, the Vickers hardness (HV) of the cross section of the copper alloy material is 160 or more and 250 or less. If the Vickers hardness (HV) of the cross section of the copper alloy material is less than 160, the hardness of the copper alloy material is low, and the copper alloy material is likely to bend during press working or etching, making it difficult to finish the copper alloy material into a desired shape. If the Vickers hardness (HV) of the cross section of the copper alloy material is more than 250, the hardness of the copper alloy material is too high, and the amount of wear of the mold tends to increase.

[0037] FIG. 1 is a schematic cross-sectional view illustrating an example of a work-affected layer formed on the surface of a copper alloy material. Copper alloy material 1 preferably has a work-affected layer 2 having an average thickness of 0.2 μm to 2.0 μm on the rolled surface 1a. The work-affected layer 2, which is the outermost layer formed on the rolled surface 1a of copper alloy material 1, is a layer generated during rolling and, together with the interior of the copper alloy material, plays a role in maintaining the balance of residual stress in the copper alloy material. When the average thickness of the work-affected layer is 0.2 μm or more, deformation of the copper alloy material caused when the work-affected layer is mainly removed by press working, etching cutting, or half etching can be suppressed, which is caused by excessively low tensile residual stress and excessively high compressive residual stress throughout the copper alloy material. Furthermore, when the average thickness of the work-affected layer is 2.0 μm or less, deformation of the copper alloy material caused when the work-affected layer is mainly removed by press working, etching cutting, or half etching can be suppressed, which is caused by excessively high tensile residual stress.

[0038] Furthermore, the copper alloy material preferably has an elongation of 3% or more and 15% or less, as measured in accordance with JIS Z 2241. When the copper alloy material is a plate strip, the elongation is along the rolling direction, and when the copper alloy material is a wire, the elongation is along the wiredrawing direction. When the copper alloy material has an elongation of 3% or more, the occurrence of material fracture during processing of the copper alloy material can be suppressed. Furthermore, even when a resistor including a resistive material for resistors made of the copper alloy material is exposed to high temperatures, shape changes of the copper alloy material due to the release of induced strain can be further suppressed, and the electrical properties of the copper alloy material can be further stabilized. On the other hand, when the elongation of the copper alloy material is 15% or less, the occurrence of deflection in the copper alloy material during press working and etching processes can be further suppressed, making it easier to finish the copper alloy material into a desired shape. Furthermore, the reduction in shear deformation resistance of the copper alloy material can reduce the amount of die wear.

[0039] Furthermore, the copper alloy material preferably has a spring limit of 500 MPa or more. When the spring limit of the copper alloy material is 500 MPa or more, deformation in the thickness direction of the copper alloy material is suppressed, and the copper alloy material is not sub-annealed or over-annealed. If the copper alloy material is sub-annealed, the processing strain is not sufficiently removed, and when a resistor including a resistor material made of the copper alloy material is exposed to high temperatures, the release of the introduced strain may cause a change in shape of the copper alloy material, and the stability of the electrical properties of the copper alloy material may be slightly reduced. If the copper alloy material is over-annealed, the copper alloy material may bend during press working or etching, and it may not be easy to finish the copper alloy material into the desired shape.

[0040] The copper alloy material may be in the form of a plate, rectangular wire, ribbon, strip, or the like.

[0041] Copper alloy materials have a sufficiently high volume resistivity, a small absolute value of thermoelectric power relative to copper, a small absolute value of temperature coefficient of resistance, and can suppress deformation during punching and etching, making them extremely useful as resistance materials for resistors. Such resistance materials for resistors are made of the copper alloy material of the above embodiment and are used in resistors, preferably shunt resistors or chip resistors. In other words, the resistor is preferably a shunt resistor or chip resistor equipped with the resistance material for resistors made of the copper alloy material of the above embodiment.

[0042] Next, a method for producing the copper alloy material will be described.

[0043] As an example of a method for producing a copper alloy material, a copper alloy material having substantially the same alloy composition as the alloy composition of the above-mentioned copper alloy material is sequentially subjected to at least a casting step, a homogenization heat treatment step, a hot working step, a cold working step, an annealing step, a finish cold working step, and a finish annealing step.

[0044] In the casting process, a copper alloy material having the above-described alloy composition is melted and cast in an inert gas atmosphere or in vacuum using a high-frequency melting furnace to produce an ingot of a predetermined shape (e.g., thickness 150 mm, width 500 mm, length 3000 mm).

[0045] The homogenization heat treatment step performed after the casting step is a step for homogenizing the ingot structure. The heat treatment conditions in the homogenization heat treatment step are, from the viewpoint of suppressing grain coarsening, a heating temperature in the range of 750°C to 900°C, and after reaching a predetermined temperature range within the heating temperature range, the temperature is preferably maintained for 10 minutes to 10 hours. The homogenization heat treatment step can be performed using a known method, such as a batch heat treatment, high-frequency heating, resistance heating, or continuous heat treatment such as running heating.

[0046] The hot working step, which is performed after the homogenization heat treatment step, is a step in which the ingot that has been subjected to the homogenization heat treatment step is subjected to processing such as hot rolling or drawing until it reaches a predetermined thickness, thereby producing a hot-rolled material. The temperature during processing is preferably in the range of 700°C to 850°C, and may be the same as the heating temperature in the homogenization heat treatment step. Furthermore, while the higher the processing rate in the hot working step, the better the efficiency, from the viewpoint of obtaining a uniform metal structure, the processing rate is preferably 80% to 95%.

[0047] Here, the "processing rate" is a value obtained by subtracting the cross-sectional area after processing such as rolling or stretching from the cross-sectional area before processing, dividing the result by the cross-sectional area before processing, and multiplying the result by 100, and expressed as a percentage, and is expressed by the following formula.

[0048] [Processing rate] = {([Cross-sectional area before processing] - [Cross-sectional area after processing]) / [Cross-sectional area before processing]} x 100 (%)

[0049] The hot-rolled material is preferably cooled immediately after hot working. The cooling method for the hot-rolled material is not particularly limited, but it is preferable to use a method that increases the cooling rate as much as possible, for example, from the viewpoint of making it difficult for crystal grains to become coarse, and it is preferable to use a method such as water cooling at a cooling rate of 50°C / second or more.

[0050] Furthermore, the cooled hot-rolled material may be subjected to a surface chamfering process in which the surface is scraped off. By performing the surface chamfering process, it is possible to remove oxide films and defects that have formed on the surface during the hot working process. The amount of the surface of the hot-rolled material that is scraped off during the surface chamfering process can be adjusted appropriately based on the conditions of the hot working process. For example, chamfering is performed to a depth of 0.4 mm to 2.6 mm from the surface of the hot-rolled material.

[0051] The cold working process performed after the hot working process (surface grinding process) is a process in which the hot-rolled material after the hot working process (surface grinding process) or the annealed material after the subsequent annealing process is subjected to cold drawing, rolling, or other processing at a total working ratio of 40% to 80%. If the total working ratio is less than 40%, the driving force for recrystallization in the subsequent heat treatment tends to be insufficient, making it difficult to obtain a uniform metal structure. On the other hand, if the total working ratio exceeds 80%, there is a risk of material destruction progressing due to the working limit. The cold working process can be performed using a known method, for example, using a rolling roll. The cold working process may be performed multiple times until the desired thickness is obtained.

[0052] The annealing process, which follows the cold working process, is a process for adjusting the strength of the cold-rolled material by heat treatment. The heat treatment conditions in the annealing process are a heating temperature in the range of 560°C to 640°C, and the temperature is maintained for 1 hour to 2 hours after reaching a predetermined temperature range. If the heating temperature in the annealing process is below 560°C, softening does not proceed, while if the heating temperature exceeds 640°C, crystal grains become coarse, resulting in insufficient hardness and elongation. Other heat treatment conditions equivalent to the effects obtained under the above heat treatment conditions may include a heating temperature of 700°C to 800°C and a holding time of 10 seconds to 5 minutes. The annealing process can be performed using known methods, such as batch heat treatment, high-frequency heating, resistance heating, and continuous heat treatment such as running heating. The above cold working process may also be performed again after the annealing process. In this case, the cold working process and the annealing process may be repeated in one cycle or multiple cycles.

[0053] The final cold working process, which is carried out after the annealing process, involves cold drawing, rolling, and other processes to finish the plate to its final thickness. The difference from the previous cold working process is that the final cold working process aims to reduce the burden on the die during pressing by appropriately reducing ductility, and to restore the spring limit value through subsequent heat treatment.

[0054] When the total working ratio is less than 20%, the working is insufficient, and as a result, the aspect ratio of the crystal grain size in the cross section of the copper alloy material becomes smaller than the above-mentioned specified range, and the work-affected layer is not sufficiently formed, and the average thickness of the work-affected layer becomes smaller than the above-mentioned specified range. As a result, as a characteristic, the elongation becomes larger than the above-mentioned specified range, and the spring limit value recovery after the subsequent finish annealing process occurs insufficiently. On the other hand, when the total working ratio is more than 40%, as a result, the aspect ratio of the crystal grain size in the cross section of the copper alloy material becomes larger than the above-mentioned specified range, and the average thickness of the work-affected layer becomes larger than the above-mentioned specified range. As a characteristic, as a result, the accumulation of working strain becomes large, and the changes in ductility and spring limit value after the subsequent finish annealing process become large, making them difficult to control.

[0055] The finish cold working step may be performed multiple times until the target thickness is obtained. The working rate per step is preferably less than 10%. If the working rate per step exceeds 10%, the aspect ratio near the surface layer will change significantly, and the work-affected layer may develop significantly in the thickness direction or irregularly. The lower limit of the working rate per step is not particularly limited, but from the viewpoint of productivity, it is preferably 3% or more.

[0056] The final annealing process, which is performed after the final cold working process, is a process in which the cold-rolled material is recrystallized by heat treatment after the final cold working process. The purpose of the final annealing process is to control the balance between material hardness and elongation and to improve the spring limit value.

[0057] The heat treatment conditions in the finish annealing step are that the heating temperature is in the range of more than 410°C and not more than 600°C, and after reaching a predetermined temperature range within the heating temperature range, the temperature is maintained for 30 seconds to 2 hours. The finish annealing step can be performed using a known method, for example, a batch type heat treatment, or a continuous heat treatment such as high frequency heating, resistance heating, or running heating.

[0058] If at least one of the heating temperature and holding time is below the above range, heating is insufficient, the hardness is too high, and adequate recovery of the spring limit does not occur. On the other hand, if at least one of the heating temperature and holding time exceeds the above range, recrystallization is likely to occur, the aspect ratio of the crystal grain size in the cross section of the copper alloy material becomes smaller than the above specified range, the average thickness of the work-affected layer becomes smaller than the above specified range, or the work-affected layer disappears. As for characteristics, the Vickers hardness becomes smaller than the above specified range, elongation increases, increasing the burden on the mold during pressing and causing insufficient control of the deformation rate of the press-punched fracture surface and the etched fracture surface. Furthermore, since the spring limit decreases, insufficient control of the press shape occurs, as with other characteristics.

[0059] According to the embodiment described above, the copper alloy material has a predetermined alloy composition, the ratio of the major axis to the minor axis of the crystal grain size in a cross section of the copper alloy material is within the above range, and the Vickers hardness (HV) is within the above range, so that the copper alloy material can have excellent formability and electrical properties.

[0060] Although the embodiments have been described above, the present invention is not limited to the above embodiments, but includes all aspects encompassed by the concept and scope of the claims of the present disclosure, and can be modified in various ways within the scope of the present disclosure. [Example]

[0061] Next, examples and comparative examples will be described, but the present disclosure is not limited to these examples.

[0062] (Examples 1 to 9, Comparative Examples 1 to 5) A copper alloy material was melted and cast in an inert gas atmosphere using a high-frequency melting furnace to obtain the alloy composition shown in Table 1. The ingot obtained by casting was subjected to a homogenization heat treatment process at a heating temperature of 750°C to 900°C and a temperature holding time of 10 minutes to 10 hours. The ingot that had undergone the homogenization heat treatment process was hot-rolled at a processing temperature of 700°C to 850°C and a processing rate of 80% to 95% to obtain a hot-rolled material. The hot-rolled material immediately after hot rolling was cooled at a cooling rate of 50°C / sec or more. The cooled hot-rolled material was subjected to a surface grinding process to grind off the surface. Subsequently, each process was performed under the manufacturing conditions shown in Table 1. Specifically, under the conditions shown in Table 2, under manufacturing conditions a to f, a cold working step, an annealing step, a finish cold working step, and a finish annealing step were sequentially performed, under manufacturing condition g, a cold working step, an annealing step, and a finish cold working step were sequentially performed, and under manufacturing condition h, a cold working step and an annealing step were sequentially performed. In this way, copper alloy materials having the compositions and properties shown in Table 1 were obtained.

[0063] In Table 1, the data that forms the basis of the comparative examples are underlined and italicized.

[0064] [evaluation] The copper alloy materials obtained in the above Examples and Comparative Examples were subjected to the following measurements and evaluations. The results are shown in Table 1.

[0065] [1] The major and minor diameters of the crystal grain size, the average crystal grain size, and the ratio of the major and minor diameters (aspect ratio) A copper alloy material was embedded in resin, and a cross-section including the rolling direction of the copper alloy material and the rolling surface normal direction was produced by mechanical polishing. This cross-section sample was observed under a microscope, and various values ​​were calculated based on the resulting micrographs at 200x to 400x magnification. The major axis of the crystal grain size was defined as the long side dimension of a rectangle with sides parallel to the rolling direction of the copper alloy material and lines normal to the rolling surface, surrounding one crystal grain. The minor axis of the crystal grain size was defined as the short side dimension of the rectangle. 30 crystal grains were measured, and their average values ​​were calculated. The major and minor axes were averaged to calculate the average crystal grain size. The ratio was calculated by dividing the major axis by the minor axis.

[0066] [2] Vickers hardness (HV) The Vickers hardness (HV) of the copper alloy material was measured in accordance with the Vickers hardness test method described in JIS Z2244 (2009). First, the copper alloy material was embedded in resin, and a cross-section including the rolling parallel direction and the rolling surface normal direction of the copper alloy material was produced by mechanical polishing. Next, the Vickers hardness (HV) of the copper alloy material was measured when the diamond indenter was pressed into this cross-section sample with a load (test force) of 0.049 N and the indenter pressing time was 15 seconds. The measurement was performed five times, and the average value was taken as the Vickers hardness of the cross section.

[0067] [3] Average thickness of the processing-affected layer Cross-sectional specimens of copper alloys were prepared by embedding the copper alloy in resin and mechanically polishing a cross section containing the direction parallel to the rolling and the direction normal to the rolling surface. The rolled surface of these cross-sectional specimens was observed using a scanning electron microscope (SEM). Based on the obtained SEM images at 10,000x to 30,000x magnification, the cross-sectional area of ​​the work-affected layer within a surface length range of 30 μm to 50 μm was calculated, and the value obtained by dividing by the length was used as the average thickness of the work-affected layer. The work-affected layer can be a grain formation layer (including refinement) different from the internal grains, a melt-solidified layer, or a layer with significant deformation. However, taking into account the alloy composition and manufacturing conditions of the copper alloy, the thickness of the work-affected layer was determined as the thickness of the surface structure consisting of a series of grains less than 1 μm in size, which are significantly different in size from the grain size of the internal structure.

[0068] [4] Elongation The average value of the elongation values ​​(elongation along the direction parallel to the rolling, number of measurements N2) measured under the tensile test conditions of the copper alloy material in accordance with JIS Z 2241 was taken as the elongation.

[0069] [5] Spring limit Using a moment-type testing machine, a copper alloy material 10 mm wide and 80 mm to 100 mm long was subjected to bending deformation in the thickness direction, and the maximum surface stress at the time when a permanent deflection of 0.1% occurred was taken as the spring limit value.

[0070] [6] Formability The shape dimensions of the copper alloy material after press punching and etching were evaluated. For press punching, general processing conditions used in general mass production were selected. For etching, a general copper etching solution such as iron chloride and copper chloride solution was used, and half etching was performed under conditions that removed 5% of the copper alloy material's thickness. For each of the press punching and etching processes, if the change in shape in the thickness direction of the copper alloy material before and after treatment was less than 1%, it was evaluated as ◎, if it was 1% to less than 2%, it was evaluated as 〇, and if it was 2% or more, it was evaluated as ×.

[0071] [7] Electrical characteristics For the samples that had been subjected to press punching and etching in the above item [6] formability, resistivity was measured at room temperature in accordance with JISH 0505. Variation in absolute values ​​was evaluated as follows: less than 1% (◎), 1% to less than 2% (○), and 2% or more (×).

[0072] [Table 1]

[0073] [Table 2]

[0074] As shown in Tables 1 and 2, the copper alloy materials produced in Examples 1 to 9 had a predetermined alloy composition, a ratio of the major axis to the minor axis of the crystal grain size in the cross section within the above range, and a Vickers hardness (HV) within the above range, and therefore had excellent formability and electrical properties. FIG. 2 shows an SEM image of a cross section of the copper alloy material produced in Example 1, including the direction parallel to the rolling and the direction normal to the rolling surface. As shown in FIG. 2, the copper alloy material produced in Example 1 had the best formability and electrical properties because the average thickness of the work-affected layer was within the above range. On the other hand, the copper alloy materials produced in Comparative Examples 1 to 5 did not satisfy at least one of the following: having a predetermined alloy composition, a ratio of the major axis to the minor axis of the crystal grain size in the cross section within the above range, and a Vickers hardness (HV) within the above range. Therefore, at least one of the formability and electrical properties was poor. [Explanation of symbols]

[0075] 1 Copper alloy material 1a Rolled surface 2. Process-affected layer

Claims

1. An alloy composition containing 21.0 mass% or more and 35.0 mass% or less of Mn, 6.5 mass% or more and 17.0 mass% or less of Ni, and the balance being Cu and unavoidable impurities, In a cross section, the ratio of the major axis to the minor axis of the crystal grain is 2.0 or more and 5.0 or less, and the Vickers hardness (HV) is 160 or more and 250 or less. Copper alloy material.

2. The copper alloy material according to claim 1, having a work-affected layer having an average thickness of 0.2 μm or more and 2.0 μm or less on the rolled surface.

3. 2. The copper alloy material according to claim 1, wherein the elongation measured in accordance with JIS Z 2241 is 3% or more and 15% or less.

4. The copper alloy material according to claim 1, wherein the spring limit is 500 MPa or more.

5. The copper alloy material according to claim 1, wherein the alloy composition further contains 0.01 mass % or more and 2.00 mass % or less of Co.

6. The alloy composition further contains 0.01% by mass or more and 0.50% by mass or less of Fe, 0.01% by mass or more and 3.00% by mass or less of Sn, 0.01% by mass or more and 5.00% by mass or less of Zn, 0.01% by mass or more and 0.50% by mass or less of Cr, 0.01% by mass or more and 0.50% by mass or less of Ag, 0.01% by mass or more and 1.00% by mass or less of Al, 0.01% by mass or more and 0.50% by mass or less of Mg, 0.01% by mass or more and 0.50% by mass or less of Si, and 0.01% by mass or more and 0.50% by mass or less of P. The copper alloy material according to claim 1, further containing at least one element selected from the group consisting of: 0.01% by mass or more and 0.50% by mass or less of P.

7. A resistive material for resistors, comprising the copper alloy material according to any one of claims 1 to 6.

8. A resistor, which is a shunt resistor or a chip resistor, comprising the resistive material for resistors according to claim 7.

Images