Copper alloy material and resistor resistance material, resistor, heating element material, and heating element using said copper alloy material

Abstract

Provided are: a copper alloy material which has a volume resistivity ρ within a desired range, and in which the absolute value of the temperature coefficient of resistance (TCR) over a wide temperature range from normal temperature (e.g., 20°C) to high temperature (e.g., 150°C) is small and the change in resistance value when left in an environment at a higher temperature (e.g., 200°C) than the operating environment is small; and a resistor resistance material, a resistor, a heating element material, and a heating element using said copper alloy material. The copper alloy material has an alloy composition containing 9.0 mass% to 13.0 mass% Mn, more than 4.0 mass% to no more than 6.0 mass% Ni, and 0.25 mass% to 2.0 mass% Co, with the remainder comprising Cu and inevitable impurities.

Description

Copper alloy materials, and resistor materials, resistors, heating element materials, and heating elements using the same.

[0001] This invention relates to copper alloy materials, and to resistor materials, resistors, heating element materials, and heating elements using the same.

[0002] Conventionally, Cu-Mn-Ni alloys have been widely used as copper-based resistive materials for resistors. These Cu-Mn-Ni alloys are known to have a high volume resistivity ρ and a small absolute value of the temperature coefficient of resistance (TCR) due to their high manganese (Mn) content. Here, the temperature coefficient of resistance (TCR) is the magnitude of the change in resistance due to temperature, expressed in parts per million (ppm) per degree Celsius, and is represented by the following formula: TCR(×10⁻¹⁰) －６ ( / °C) = {(R - R ０ ) / R ０} × {1 / (T-T ０ )} × 10 ６ Equation (1): In Equation (1), T is the test temperature (°C), T ０ R is the reference temperature (°C), R is the resistance value (Ω) at the test temperature T, R ０ The reference temperature T ０ This shows the resistance value (Ω) at that point.

[0003] As an example of a Cu-Mn-Ni alloy, Non-Patent Literature 1 describes a copper alloy represented by the JIS symbol GCM44, which contains Mn in an amount of 10.0% to 13.0% by mass, Ni in an amount of 1.0% to 4.0% by mass, and the total amount of Cu + Mn + Ni is 98.0% by mass or more, and has a volume resistivity ρ of 44 [μΩ・cm].

[0004] Furthermore, Patent Document 1 discloses a copper alloy strip having an alloy composition containing 3% to 20% by mass of Mn, with the remainder being Cu and unavoidable impurities, wherein the average value of the KAM (small orientation difference map) calculated by measuring the KAM by backscattered electron diffraction (EBSD) is 1° or more and less than 4°, and the proportion of the area where the KAM value is 1° or more and less than 4° to the total area where the KAM was measured is 20% or more and less than 50%. Patent Document 2 discloses a Cu alloy material containing 7.0% to 20.0% by mass of Mn, with the remainder being Cu and unavoidable impurities, having a Vickers hardness of 150 HV or more, and an absolute value of the temperature coefficient of resistance (TCR) at 20°C to 150°C of 50 ppm / K or less.

[0005] Japanese Industrial Standard JIS C 2532; 1999

[0006] Patent No. 6961861 Patent No. 6471494

[0007] Thus, conventional copper alloy materials are used not only in resistors but also in heating elements such as heater wires. For example, in operating environments below 100°C, they are characterized by a small temperature dependence of volume resistivity ρ, resulting in a small positive temperature coefficient of resistance (TCR). However, in higher temperature operating environments, such as 150°C, the resistance value decreases significantly, causing the temperature coefficient of resistance (TCR) of the copper alloy to become a large negative number.

[0008] In recent years, there has been a demand for high-precision copper alloy materials that can withstand high currents and higher operating environments, and it has been desirable for these materials to exhibit minimal resistance fluctuations in a temperature range from room temperature (e.g., 20°C) to 150°C.

[0009] In contrast, conventional copper alloys were characterized by having a small positive temperature coefficient of resistance (TCR) in operating environments below 100°C, for example. However, metals commonly used in electrodes have a positive correlation with the temperature dependence of their volume resistivity ρ, resulting in a positive TCR. In this respect, even if a copper alloy with a small positive TCR were used in a resistor or heating element, the TCR would become a larger positive value when viewed as a whole due to the influence of the electrode material. Therefore, there was a need for a copper alloy with a small temperature dependence of volume resistivity ρ even when considering the presence of the electrode material, specifically one whose TCR is 0 or negative and has a small absolute value.

[0010] Furthermore, while a high volume resistivity ρ is preferable for copper alloy materials used in resistors and heating elements from the standpoint of improving resistor accuracy, increasing the resistance value unnecessarily increases the power consumption of the resistor or heating element, leading to a problem of significant energy loss, particularly due to heat generation. Therefore, there was a need for a copper alloy material with an appropriate volume resistivity ρ that could be used in resistors and heating elements while minimizing energy loss due to heat generation.

[0011] In particular, copper alloy materials used in resistors and heating elements achieve desired resistance and heat generation by changing the cross-sectional area. However, if the resistance is excessively high, the cross-sectional area of ​​the heating element must be increased, which can reduce the processability of the heating element and increase its weight. In addition, if the copper alloy material used in resistors and heating elements has a large positive temperature coefficient of resistance (TCR), the resistance increases within the operating temperature range, making temperature control difficult. Therefore, copper alloy materials used in resistors and heating elements were required to have an appropriate volume resistivity ρ and a small absolute value of the temperature coefficient of resistance (TCR). Furthermore, copper alloys used in resistors and heating elements are required to have stable resistance values ​​that can withstand long-term use. Accordingly, there was a need for copper alloys that exhibit little change in resistance even when left in environments hotter than the high temperature of the operating environment (e.g., 150°C) in accelerated testing (e.g., 200°C), that is, copper alloys with excellent oxidation resistance and heat resistance of the structure.

[0012] Therefore, an object of the present invention is to provide a copper alloy material having a volume resistivity ρ within a desired range, a small absolute value of the temperature coefficient of resistance (TCR) over a wide temperature range from room temperature (e.g., 20°C) to high temperature (e.g., 150°C), and a small change in resistance when left at a temperature higher than the operating environment (e.g., 200°C), as well as a resistor material, resistor, heating element material, and heating element using the same.

[0013] The inventors have discovered that by creating an alloy composition containing Mn: 9.0% to 13.0% by mass, Ni: greater than 4.0% to 6.0% by mass, and Co: 0.25% to 2.0% by mass, with the remainder being Cu and unavoidable impurities, a copper alloy material can be obtained that has a desired range of volume resistivity ρ and a small temperature coefficient of resistance (TCR) over a wide temperature range from room temperature (e.g., 20°C) to high temperature (e.g., 150°C) (for example, in the range of -40 ppm / °C to 0 ppm / °C), thus completing the present invention.

[0014] To achieve the above objectives, the gist of the present invention is as follows: (1) A copper alloy material having an alloy composition containing Mn: 9.0% by mass or more and 13.0% by mass or less, Ni: greater than 4.0% by mass and 6.0% by mass or less, and Co: greater than 0.25% by mass and 2.0% by mass or less, with the remainder being Cu and unavoidable impurities. (2) The copper alloy material according to (1) above, having a metallic structure with an average grain size of 40 μm or less, and an average KAM value of 2.0° or less measured by backscattered electron diffraction (EBSD). (3) The copper alloy material according to (1) or (2) above, wherein the alloy composition further contains, in place of a portion of Cu, one or more components selected from the group consisting of Fe, Sn, Zn, Cr, Ag, Mg, Si, and P, each in an amount of 0.01% by mass or more and 0.50% by mass or less. (4) A resistor material made of the copper alloy material described in (1), (2), or (3) above. (5) A resistor having the resistor material described in (4) above. (6) A heating element material made of the copper alloy material described in (1), (2), or (3) above. (7) A heating element having the heating element material described in (6) above.

[0015] According to the present invention, it is possible to provide a copper alloy material having a volume resistivity ρ within a desired range, a low temperature coefficient of resistance (TCR) over a wide temperature range from room temperature (e.g., 20°C) to high temperature (e.g., 150°C), and excellent long-term resistance stability, as well as a resistor material, resistor, heating element material, and heating element using the same.

[0016] Preferred embodiments of the copper alloy material of the present invention will be described in detail below. Note that in the composition of the alloy of the present invention, "mass%" may sometimes be simply expressed as "%".

[0017] The copper alloy material of the present invention has an alloy composition containing Mn: 9.0% by mass or more and 13.0% by mass or less, Ni: more than 4.0% by mass and 6.0% by mass or less, and Co: 0.25% by mass or more and 2.0% by mass or less, with the remainder being Cu and unavoidable impurities.

[0018] In the copper alloy material of the present invention, Mn is contained in the range of 9.0% by mass or more and 13.0% by mass or less, Ni is contained in the range of more than 4.0% by mass and 6.0% by mass or less, and Co is contained in the range of 0.25% by mass or more and 2.0% by mass or less. As a result, compared with the case where Co is not contained, the volume resistivity ρ is large, and the temperature coefficient of resistance (TCR) in a wide temperature range from room temperature (for example, 20°C) to high temperature (for example, 150°C) is, for example, in the range of -40 ppm / °C or more and 0 ppm / °C or less, becoming smaller. Therefore, even in a high-temperature environment, the high-precision of the resistor can be advanced. In addition, the high performance of the heating element can be advanced. Moreover, especially by containing Mn in the range of 9.0% by mass or more and 13.0% by mass or less, the volume resistivity ρ can be adjusted within a desired range, and by containing Ni in the range of more than 4.0% by mass and 6.0% by mass or less, the oxidation resistance and long-term reliability can be enhanced.

[0019] Regarding this, in the JIS symbol GCM44: Cu-Mn-Ni alloy, regarding the temperature dependence of the volume resistivity ρ, in the temperature range from 23°C to 100°C, the average temperature coefficient (TCR) is +50×10 －６ [°C －１ is described. However, in this Cu-Mn-Ni alloy, since the volume resistivity ρ significantly decreases at a high temperature close to 150°C, in the temperature range from 20°C to 150°C including a higher temperature range, the temperature coefficient of resistance (TCR) becomes a large negative number, and thus an error is likely to occur in the resistance value, particularly in the high-temperature range. In this regard, in the copper alloy material of the present invention, the temperature coefficient of resistance (TCR) in a wide temperature range from room temperature (for example, 20°C) to high temperature (for example, 150°C) can be made smaller.

[0020] Furthermore, as described in Patent Document 1 above, in a composition alloy containing 3% to 20% by mass of Mn, with the remainder being Cu and unavoidable impurities, it is possible to improve the temperature coefficient of resistance (TCR) and adjust the volume resistivity ρ by adding 0.01% to 0.5% by mass of Co. It also states that by specifying the average value and the proportion occupied by a specific area for KAM measured by backscattered electron diffraction, copper alloy strips with less variation in resistance values ​​between products and lots can be obtained. However, the absolute values ​​of the temperature coefficient of resistance (TCR) and volume resistivity ρ are not considered at all. In the copper alloy material of the present invention, it is possible to reduce KAM to suppress variation in resistance values ​​while simultaneously achieving a desired range for volume resistivity ρ and temperature coefficient of resistance (TCR).

[0021] Furthermore, the aforementioned Patent Document 2 describes a copper alloy strip containing 7.0% to 20.0% by mass of Mn, with the remainder being Cu and unavoidable impurities. By specifying the conditions for rolling and heat treatment, it is possible to obtain a Vickers hardness of 150 HV or higher and an absolute value of the temperature coefficient of resistance (TCR) of 50 ppm / K or less at temperatures between 20°C and 150°C. It also states that the change in volume resistivity ρ during high-temperature heating is reduced, but the relationship between volume resistivity ρ itself and the temperature coefficient of resistance (TCR) is not considered at all. With the copper alloy material of the present invention, the above composition makes it possible to achieve both a desired range of volume resistivity ρ and temperature coefficient of resistance (TCR).

[0022] Therefore, the present invention provides copper alloy materials that have a volume resistivity ρ within a desired range and a small absolute value of the temperature coefficient of resistance (TCR), as well as resistor materials, resistors, heating element materials, and heating elements using the same.

[0023] [1] Composition of copper alloy material <Essential components> The alloy composition of the copper alloy material of the present invention contains, as essential components, Mn: 9.0% by mass or more and 13.0% by mass or less, Ni: greater than 4.0% by mass and 6.0% by mass or less, and Co: 0.25% by mass or more and 2.0% by mass or less.

[0024] (Mn: 9.0% by mass or more and 13.0% by mass or less) Manganese (Mn) is an element that increases the volume resistivity ρ and adjusts the temperature coefficient of resistance (TCR) in the negative direction, making it easier to obtain a large negative absolute value for the temperature coefficient of resistance (TCR). For this reason, it is preferable to contain 9.0% by mass or more of Mn, and more preferably 10.0% by mass or more. In particular, the effect of making the temperature coefficient of resistance (TCR) negative is greatly influenced by increasing the Mn content. On the other hand, if the Mn content exceeds 13.0% by mass, the volume resistivity ρ becomes too high, and it becomes difficult to reduce the absolute value of the temperature coefficient of resistance (TCR). For this reason, it is preferable that the Mn content be 13.0% by mass or less. More specifically, it is preferable that the Mn content in the alloy composition be in the range of 9.0% by mass or more and 13.0% by mass or less.

[0025] (Ni: 4.0% by mass or more and 6.0% by mass or less) Ni (nickel) is an element that significantly increases the positive temperature coefficient of resistance (TCR), and can adjust the TCR, which has become a large negative number due to the addition of Mn, to a positive direction. Furthermore, it enhances oxidation resistance and allows for a stable resistance value to be obtained even after being left at high temperatures for a long time. To exhibit this effect, it is preferable that the Ni content be 4.0% by mass or more. On the other hand, if the Ni content exceeds 6.0% by mass, it becomes easier to form compounds with Mn, making it difficult to obtain a stable resistance value. For this reason, the Ni content is preferably in the range of 4.0% by mass or more and 6.0% by mass or less.

[0026] (Co: 0.25% by mass or more and 2.0% by mass or less) Co (cobalt) is an element that increases the volume resistivity ρ and, unlike Mn, does not cause a large negative value for the temperature coefficient of resistance (TCR). To fully exert the effect of this action, it is preferable to contain 0.25% by mass or more of Co. On the other hand, if the Co content exceeds 2.0% by mass, phase separation is more likely to occur, which may impair the long-term reliability of the resistance value. For this reason, the Co content is preferably in the range of 0.25% by mass or more and 2.0% by mass or less, and more preferably in the range of 0.6% by mass or more and 2.0% by mass or less.

[0027] <Optional Additives> The alloy composition may, in place of a portion of Cu, further contain one or more components selected from the group consisting of Fe, Sn, Zn, Cr, Ag, Mg, Si, and P, each in an amount of 0.01% by mass or more and 0.50% by mass or less.

[0028] (Fe: 0.01% by mass or more, 0.50% by mass or less) Fe (iron) is a component that can be used to adjust the volume resistivity ρ of the copper alloy material of the present invention. To exert this effect, it is preferable to contain 0.01% by mass or more of Fe. On the other hand, by limiting the Fe content to 0.50% by mass or less, it is possible to make changes in the resistance value less likely to occur during long-term use.

[0029] (Sn: 0.01% by mass or more, 0.50% by mass or less) Sn (tin) is a component that can be used to adjust the volume resistivity ρ. To exert this effect, it is preferable to contain 0.01% by mass or more of Sn. On the other hand, by limiting the Sn content to 0.50% by mass or less, it is possible to reduce the likelihood of a decrease in the manufacturability of the copper alloy material.

[0030] (Zn: 0.01% by mass or more, 0.50% by mass or less) Zinc (Zn) is an ingredient that can be used to adjust the volume resistivity ρ. To exert this effect, it is preferable to contain 0.01% by mass or more of Zn. On the other hand, since the Zn content may adversely affect the change in resistance value during long-term use, it is preferable to keep it at 0.50% by mass or less.

[0031] (Cr: 0.01% by mass or more, 0.50% by mass or less) Cr (chromium) is an ingredient that can be used to adjust the volume resistivity ρ. To exert this effect, it is preferable to contain 0.01% by mass or more of Cr. On the other hand, since the Cr content may adversely affect the change in resistance value during long-term use, it is preferable to keep it at 0.50% by mass or less.

[0032] (Ag: 0.01% by mass or more and 0.50% by mass or less) Silver (Ag) is a component that can be used to adjust the volume resistivity ρ. To exhibit this effect, it is preferable to contain Ag at 0.01% by mass or more. On the other hand, since the Ag content may affect the change in resistance value during long-term use, it is preferably 0.50% by mass or less.

[0033] (Mg: 0.01% by mass or more and 0.50% by mass or less) Mg (magnesium) is a component that can be used as a deoxidizer during casting. To exhibit this effect, it is preferable to contain Mg at 0.01% by mass or more. On the other hand, since the Mg content may adversely affect the change in resistance value during long-term use, it is preferably 0.50% by mass or less.

[0034] (Si: 0.01% by mass or more and 0.50% by mass or less) Si (silicon) is a component that can be used as a deoxidizer during casting. To exhibit this effect, it is preferable to contain Si at 0.01% by mass or more. On the other hand, by setting the Si content to 0.50% by mass or less, it is possible to suppress the deterioration of the manufacturability of the copper alloy material.

[0035] (P: 0.01% by mass or more and 0.50% by mass or less) P (phosphorus) is a component that can be used as a deoxidizer during casting. To exhibit this effect, it is preferable to contain P at 0.01% by mass or more. On the other hand, when a large amount of P is contained, a low-melting-point intermetallic compound (Cu ３ P) is generated at the grain boundaries, and the strength of the grain boundaries decreases. Therefore, by setting the P content to 0.50% by mass or less, it is possible to suppress the deterioration of the manufacturability of the copper alloy material.

[0036] (Total amount of optional additive components: 0.01% by mass or more and 0.50% by mass or less) The optional additive components composed of one or more components selected from the group consisting of Fe, Sn, Zn, Cr, Ag, Mg, Si, and P preferably contain a total of 0.01% by mass or more in order to obtain the effects of these optional additive components. On the other hand, since the content of these optional additive components may adversely affect the change in resistance value during long-term use and may also deteriorate the manufacturability of the copper alloy material, it is preferably 0.50% by mass or less in total.

[0037] <Remainder: Cu and inevitable impurities>Other than the essential components and optional components described above, the remainder consists of Cu (copper) and inevitable impurities. Here, the "inevitable impurities" generally refer to those present in the raw materials or inevitably mixed in the manufacturing process in copper-based products, which are originally unnecessary but are permitted because they are in trace amounts and do not affect the properties of copper-based products. Examples of components listed as inevitable impurities include non-metallic elements such as sulfur (S), carbon (C), oxygen (O), and metallic elements such as antimony (Sb). The upper limit of the content of these components can be 0.05% by mass for each of the above components and 0.10% by mass for the total amount of the above components.

[0038] [2] Shape and metallic structure of the copper alloy material (metallic structure of the copper alloy material) The copper alloy material of the present invention has an average crystal grain size of 40 μm or less and an average value of KAM measured by the electron backscatter diffraction method of 2.0° or less.

[0039] (Shape of the copper alloy material) The shape of the copper alloy material of the present invention is not particularly limited and can take various forms such as plates, wires, flat wires, ribbons, tubes, etc. However, from the perspective of facilitating the subsequent hot or cold processing steps, it is preferably a plate material, bar material, strip material or wire material. Among these, for copper alloy materials formed by rolling, such as plate materials and strip materials, the rolling direction can be the stretching direction. Also, for copper alloy materials formed by wire drawing, drawing, or extrusion, such as wire materials like flat wires and round wires, and bar materials, any of the wire drawing direction, drawing direction, and extrusion direction can be the stretching direction.

[0040] (Average grain size) Furthermore, it is preferable that the copper alloy material of the present invention has a metal structure in which the average grain size is 40 μm or less. Here, by making the average grain size of the crystals contained in the metal structure of the copper alloy material 40 μm or less, the yield strength of the alloy can be increased, thereby making the copper alloy material less prone to breakage. If the average grain size of the copper alloy material of the present invention exceeds 40 μm, there is a risk that the properties will change, such as the volume resistivity ρρ becoming too small and the temperature coefficient of resistance (TCR) becoming too large, so it is set to 40 μm or less. By making the average grain size 40 μm or less, the temperature coefficient of resistance (TCR) can be stabilized. Note that if the crystals are not formed equiaxed and there is anisotropy in the size of the crystal grains due to processing such as rolling or drawing along the stretching direction, the average grain size of the crystals shall be measured on a plane perpendicular to the stretching direction.

[0041] (Measurement of average grain size) Here, the measurement of the average grain size in this specification can be carried out in accordance with the grain size test method for drawn copper products described in JIS H 0501. More specifically, the test can be carried out by preparing a test specimen by embedding the copper alloy material in resin so that the cross-section is exposed, polishing the cross-section perpendicular to the stretching direction, then performing wet etching with a chromic acid aqueous solution, and observing the exposed crystal grains with a scanning electron microscope (SEM) to measure the grain size (or grain size). In particular, when measuring the average grain size on a plane perpendicular to the stretching direction, the test specimen is prepared by embedding the copper alloy material in resin so that the cross-section perpendicular to the stretching direction is exposed.

[0042] <Crystal structure of copper alloy strip> Furthermore, the copper alloy material of the present invention has an average value of KAM (small orientation difference map) measured by backscattered electron diffraction (EBSD) of 2.0° or less.

[0043] (KAM (Micro-orientation Map)) It is desirable that the average KAM value of the alloy strip material of the present invention, measured by backscattered electron diffraction (EBSD method), be 2.0° or less. By having an average KAM value of 2.0° or less, the copper alloy strip material will have only slight distortion, and the change in resistance value during long-term use can be reduced. On the other hand, if the average KAM value exceeds 2.0°, the resistance value may fluctuate due to the effects of heat generated during use or mounting, for example, and there is a risk of variation in resistance values ​​between products or lots. Therefore, by setting the KAM value to 2.0° or less, the distortion of the copper alloy material is reduced, and the temperature coefficient of resistance (TCR) can be stabilized.

[0044] (Measurement of KAM) KAM is measured using the backscattered electron diffraction method with a JSM-7001FA manufactured by JEOL Ltd. For copper alloy strips, the cross section parallel to the rolling direction is used as the measurement sample. For round wires and rectangular wires, the cross section perpendicular to the drawing and extrusion directions is used. The cross section is mirror-finished by resin embedding, electropolishing, etc. For example, the surface of the sample can be mirror-finished by immersing the copper alloy strip in a phosphoric acid solution and electropolishing by applying an electric current for 60 seconds. Of the cross-sectional samples, the field of view is 100 μm × 100 μm in the center of the thickness for copper alloy strips, 100 μm × 100 μm in the center for round wires, and 100 μm × 100 μm in the center of both the thickness and width for rectangular wires. The measurement is performed with a step size of 0.2 μm. Using the OIM Analysis software from TSL Corporation, the average KAM (Kernel Average Misorientation) was calculated for all points, using the first neighbor measurement value with a crystal orientation difference of 15° or more as the boundary. This measurement was performed at five arbitrary locations, and the average value was calculated.

[0045] [3] Method for manufacturing copper alloy material The copper alloy material of the present invention can be realized by controlling the combination of alloy composition and manufacturing process, and the manufacturing process is not particularly limited. Among these, the following method can be given as an example of a manufacturing process that can obtain the copper alloy material of the present invention.

[0046] As an example of a method for manufacturing the copper alloy material of the present invention, a copper alloy material having substantially the same alloy composition as the copper alloy material of the present invention is subjected to at least the following steps in sequence: casting [step 1], homogenization heat treatment [step 2], hot working [step 3], cold working [step 4], and annealing [step 5]. Of these, in the casting [step 1], the copper alloy material is melted in an inert gas atmosphere or in a vacuum to produce an ingot. In the homogenization heat treatment [step 2], the heating temperature is set in the range of 750°C to 900°C, and the holding time at the heating temperature is set in the range of 10 minutes to 10 hours. In the annealing [step 5], the heating temperature is set in the range of 450°C to 700°C, and the holding time at the heating temperature is set in the range of 1 minute to 2 hours. Further details are described below.

[0047] (i) Casting process [Step 1] In the casting process [Step 1], a copper alloy material having the alloy composition of the present invention is melted in an inert gas atmosphere or vacuum using a high-frequency induction melting furnace, and cast to produce an ingot of a predetermined shape (for example, 30 mm thick, 50 mm wide, and 300 mm long). Note that the alloy composition of the copper alloy material may not be exactly the same as the alloy composition of the copper alloy material produced in each manufacturing process, as some of the added components may adhere to the melting furnace or volatilize, but it has substantially the same alloy composition as the copper alloy material.

[0048] (ii) Homogenization heat treatment process [Step 2] The homogenization heat treatment process [Step 2] is a process in which the ingot after the casting process [Step 1] is subjected to heat treatment for homogenization. Here, the conditions for the heat treatment in the homogenization heat treatment process [Step 2] are preferably such that the heating temperature is in the range of 750°C to 900°C and the holding time at the heating temperature is in the range of 10 minutes to 10 hours, from the viewpoint of suppressing grain coarsening.

[0049] (iii) Hot working process [Process 3] The hot working process [Process 3] is a process in which a hot-rolled material is produced by hot-rolling or drawing the ingot that has undergone homogenization heat treatment until it reaches a predetermined thickness and dimensions. Here, the hot working process [Process 3] includes both a hot-rolling process and a hot-drawing (wire drawing) process. Furthermore, the conditions for the hot working process [Process 3] are that the processing temperature is preferably in the range of 750°C to 900°C, and may be the same as the heating temperature in the homogenization heat treatment process [Process 2]. Furthermore, the processing rate in the hot working process [Process 3] is preferably 10% or more.

[0050] Here, the "processing rate" is calculated by subtracting the cross-sectional area after processing from the cross-sectional area before processing (such as rolling or drawing), dividing this value by the cross-sectional area before processing, multiplying by 100, and expressing it as a percentage. It is expressed by the following formula: [Processing Rate (%)] = {([Cross-sectional area before processing] - [Cross-sectional area after processing]) / [Cross-sectional area before processing]} × 100

[0051] It is preferable to cool the hot-rolled material after the hot working process [Step 3]. Here, the means of cooling the hot-rolled material are not particularly limited, but from the viewpoint of making grain coarsening less likely to occur, for example, it is preferable to use a means that increases the cooling rate as much as possible, and it is preferable to make the cooling rate 10°C / second or more by means such as water cooling.

[0052] Here, surface milling may be performed on the cooled hot-rolled material to remove surface deposits. Surface milling can remove surface oxide films and defects generated in the hot working process [step 3]. The surface milling conditions can be any conditions that are normally used and are not particularly limited. The amount removed from the surface of the hot-rolled material by surface milling can be appropriately adjusted based on the conditions of the hot working process [step 3], for example, to about 0.5 mm to 4 mm from the surface of the hot-rolled material.

[0053] (iv) Cold working process [Process 4] The cold working process [Process 4] is a process in which the hot-rolled material after the hot working process [Process 3] is subjected to cold rolling, drawing, or other processing at an arbitrary processing rate according to the plate thickness, wire diameter, or dimensions of the product. Here, the cold working process [Process 4] includes both a cold rolling process and a cold drawing (wire drawing) process. In addition, the conditions for rolling and wire drawing in the cold working process [Process 4] can be set according to the size of the hot-rolled material. In particular, from the viewpoint of promoting the generation of uniform crystal grains by recrystallization in the annealing process [Process 5] described later, it is preferable to set the total processing rate in the cold working process [Process 4] to 50% or more.

[0054] (v) Annealing process [Process 5] The annealing process [Process 5] is an annealing process in which the cold-rolled material after the cold working process [Process 4] is subjected to heat treatment to recrystallize it. Here, the heat treatment conditions in the annealing process [Process 5] are that the heating temperature is in the range of 450°C to 700°C, and the holding time at the heating temperature is in the range of 1 minute to 2 hours. On the other hand, if the heating temperature is less than 450°C or the holding time is less than 1 minute, it becomes difficult to recrystallize the copper alloy material. Also, if the heating temperature exceeds 700°C or the holding time exceeds 2 hours, there is a risk that the electrical properties will vary due to grain coarsening.

[0055] Here, a cold working process [step 6] and an annealing process [step 7] may be added to the cold-rolled material after the annealing process [step 5]. For example, a second cold working process and annealing process may be performed on the cold-rolled material after the annealing process [step 5]. Furthermore, recrystallization is not necessarily required in the heat treatment after the final processing, and the temperature at that time may be, for example, 450°C or lower. On the other hand, in order to improve the long-term stability of the resistance value, it is necessary to adjust the strain so that the average value of the KAM value is 2.0° or less. As a result, the copper alloy material becomes a plate, rod, strip, or wire with the desired shape, and coarse crystal grains are less likely to form, so a copper alloy material exhibiting the desired properties can be obtained.

[0056] [4] Applications of Copper Alloy Material The copper alloy material of the present invention can take the form of plates, rods, strips such as ribbons, and wires such as rectangular wires and round wires, and is extremely useful as a resistive material for resistors, such as shunt resistors and chip resistors. In other words, it is preferable that the resistive material for resistors be made of the above-mentioned copper alloy material. Furthermore, it is preferable that resistors such as shunt resistors or chip resistors have a resistive material for resistors made of the above-mentioned copper alloy material. In addition, because the copper alloy material of the present invention has a relatively high resistance value, it is also suitable as a material for heating elements, such as heater wires. In other words, it is preferable that the material for heating elements be made of the above-mentioned copper alloy material. Furthermore, it is preferable that heating elements such as heater wires have a material for heating elements made of the above-mentioned copper alloy material.

[0057] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and includes all aspects included in the concept and claims of the present invention, and can be modified in various ways within the scope of the present invention.

[0058] Next, examples and comparative examples will be described to further clarify the effects of the present invention, but the present invention is not limited to these examples.

[0059] (Examples 1-13 and Comparative Examples 1-14) A casting process [Step 1] was performed in which a copper alloy material having the alloy composition shown in Table 1 was melted and cast to obtain an ingot with a thickness of 30 mm. A homogenization heat treatment process [Step 2] was performed on this ingot, in which it was heated to a temperature of 800°C and held for 5 hours. Then, a hot working process [Step 3] was performed in which it was rolled along the longitudinal direction at a temperature of 800°C to a total processing rate of 67%, to obtain a hot-rolled material with a thickness of 10 mm. After that, it was cooled to room temperature by water cooling and then surface milling was performed to remove the oxide film formed on the surface.

[0060] Next, the hot-rolled material was subjected to a cold working process [Step 4] in which it was rolled along the longitudinal direction with a total processing rate of 90% to obtain a cold-rolled material with a thickness of 1 mm. Subsequently, the cold-rolled material was subjected to an annealing process [Step 5] in which it was heat-treated by holding it at a heating temperature of 500°C to 750°C for 1 minute.

[0061] After performing the annealing process [Step 5], a second cold working process [Step 4] was performed, in which the material was rolled along the longitudinal direction with a total processing rate of 70%, to obtain a cold-rolled material with a thickness of 0.3 mm. After the second cold working process [Step 4], a second annealing process [Step 5] was performed, in which heat treatment was carried out at a heating temperature in the range of 500°C to 750°C for a holding time of 1 minute to 2 hours. In this way, copper alloy sheet materials of Examples 1 to 13 and Comparative Examples 1 to 14 with adjusted grain sizes were produced.

[0062]

[0063] In Table 1, a horizontal line "-" is indicated in the column for components not included in the alloy composition of the copper alloy material, indicating that the component is either not present or, if present, is below the detection limit.

[0064] (Examples 14-21 and Comparative Examples 15-22) A casting process [Step 1] was performed in which a copper alloy material having the alloy composition shown in Table 2 was melted and cast to obtain an ingot with a diameter of 30 mm. A homogenization heat treatment process [Step 2] was performed on this ingot, in which it was heated to a temperature of 800°C and held for 5 hours. Then, a hot working process [Step 3] was performed in which it was extruded at a temperature of 800°C to a total processing rate of 67% to obtain a hot-rolled rod with a diameter of 10 mm. After that, it was cooled to room temperature by water cooling and then surface milling was performed to remove the oxide film formed on the surface.

[0065] Next, a cold working process [Step 4] was performed on the rod material, in which it was drawn using a circular die to obtain a round wire with a diameter of 1.95 mm. Subsequently, an annealing process [Step 5] was performed on the round wire, in which it was heat-treated at a heating temperature in the range of 500°C to 750°C for a holding time of 1 minute to 2 hours. In this way, copper alloy round wires of Examples 14 to 21 and Comparative Examples 15 to 22, with adjusted grain sizes, were produced.

[0066]

[0067] (Examples 22-26 and Comparative Examples 23-30) In the same manner as in Example 14, the rod material obtained after the hot working process [Step 3] was drawn using a flat die with a radius of curvature of 0.1 mm at the four corners to obtain a flat wire with a thickness of 1 mm and a width of 3 mm, in a cold working process [Step 4], to obtain a flat wire. Subsequently, the flat wire was subjected to an annealing process [Step 5], in which heat treatment was performed at a heating temperature in the range of 500°C to 750°C for a holding time of 1 minute to 2 hours. In this way, copper alloy flat wires of Examples 22-26 and Comparative Examples 23-30 with adjusted grain sizes were produced.

[0068]

[0069] [Method for measuring metal structure and performance] The copper alloy materials (copper alloy sheets, copper alloy round wires, and copper alloy rectangular wires) according to the above examples and comparative examples were used to evaluate the properties shown below. The evaluation conditions for each property are as follows.

[0070] [1] Method for measuring average grain size For the prepared copper alloy material, a test specimen was prepared by embedding it in resin so that a cross section perpendicular to the stretching direction of the copper alloy material (longitudinal direction, which is the rolling direction of the sheet material, and the drawing and extrusion directions of the rectangular wire and round wire) was exposed. Then, the cross section perpendicular to the stretching direction was polished. Next, the polished test specimen was wet-etched using an aqueous chromic acid solution. Then, the exposed crystal grains were observed in three fields of view at magnifications ranging from 50x to 2000x depending on the average grain size using a scanning electron microscope (SEM) (Shimadzu Corporation, model number: SSX-550). The crystal grain size was measured using the cutting method of the test method for crystal grain size of drawn copper products described in JIS H 0501, and the average grain size was calculated as the average value of the crystal grain sizes in the three fields of view. The measurement results for the plate materials of Examples 1 to 13 and Comparative Examples 1 to 14, the round wire materials of Examples 14 to 21 and Comparative Examples 15 to 22, and the rectangular wire materials of Examples 22 to 26 and Comparative Examples 23 to 30 are shown in Tables 4 to 6.

[0071] [2] Method for measuring the average value of KAM The cross-sections of the test materials from Examples 1 to 26 and Comparative Examples 1 to 30 were mirror-finished by electropolishing to prepare the measurement samples. A 100 μm × 100 μm field of view of the mirror-finished measurement sample was used as the measurement target, and crystal orientation data was continuously measured using an EBSD detector attached to a high-resolution scanning analytical electron microscope (JEOL Ltd., JSM-7001FA) with a step size of 0.2 μm. Crystal orientation analysis data was calculated from the crystal orientation data obtained from the measurement using analysis software (TSL Corporation, OIM Analysis). Using the analysis software, the percentage of the area with KAM of 2° or less in the 100 μm × 100 μm field of view that was the measurement target was determined, with a crystal orientation difference of 15° or more as the boundary. Such measurements were performed at five arbitrary locations, and the average value was calculated.

[0072] [3] Method for measuring volume resistivity ρ For Examples 1 to 13 and Comparative Examples 1 to 7 and 9 to 12, which obtained plate material, the obtained 0.3 mm thick plate material was cut to a width of 10 mm and a length of 300 mm to prepare test specimens. For Examples 14 to 21 and Comparative Examples 15 to 18 and 20, which obtained round wire, and for Examples 22 to 26 and Comparative Examples 23 to 27, which obtained rectangular wire, the obtained round wire or rectangular wire was cut to a length of 300 mm to prepare test specimens.

[0073] The volume resistivity ρ was measured using the four-terminal method according to JIS C 2525, with a voltage terminal distance of 200 mm and a measurement current of 100 mA, at room temperature of 20°C. The volume resistivity ρ [μΩ・cm] was then determined from the obtained values.

[0074] [4] Method for measuring the temperature coefficient of resistance (TCR) For Examples 1 to 13 and Comparative Examples 1 to 14, which obtained plate material, the obtained 0.3 mm thick plate material was cut to a width of 10 mm and a length of 300 mm to prepare test specimens. For Examples 14 to 21 and Comparative Examples 15 to 18 and 20, which obtained round wire, and for Examples 22 to 26 and Comparative Examples 23 to 27, which obtained rectangular wire, the obtained round wire or rectangular wire was cut to a length of 300 mm to prepare test specimens.

[0075] The temperature coefficient of resistance (TCR) is measured using the four-terminal method in accordance with JIS C 2526, with a voltage terminal distance of 200 mm and a measurement current of 100 mA. The voltage is measured when the test material is heated to 150°C, and the resistance value R at 150°C is calculated from the obtained value. １５０℃ The resistance [mΩ] was determined. Next, the voltage was measured when the temperature of the test material was cooled to 20°C, and the resistance value R at 20°C was obtained from the obtained value. ２０℃ The value [mΩ] was calculated. Then, the resulting resistance value R １５０℃ and R ２０℃ From the value, TCR = {(R １５０℃ [mΩ]-R ２０℃ [mΩ]) / R ２０℃ [mΩ]}×{1 / (150[℃]-20[℃])}×10 ６ The temperature coefficient of resistance (ppm / °C) was calculated from the following formula.

[0076] [5] Measurement Method for Changes in Resistance for Long-Term Reliability In order to examine the reliability of copper alloy materials when used for long periods as resistive materials, particularly the stability of electrical properties against heat, an accelerated test was conducted on the stability of electrical properties against heat and oxidation by heating the test material in an atmospheric environment at 200°C for 300 hours after the volume resistivity ρ had been measured. After the accelerated test by heating, the volume resistivity ρ of the test material was measured using the same method as the measurement of volume resistivity ρ, and the difference in volume resistivity ρ was calculated by subtracting the volume resistivity ρ after heating from the volume resistivity ρ before heating.

[0077] [Method for Evaluating Metal Structure and Performance] The copper alloy materials (copper alloy sheets, copper alloy round wires, and copper alloy rectangular wires) related to the above examples and comparative examples were used to evaluate the properties shown below. The evaluation conditions for each property are as follows. The evaluation results are shown in Tables 4 to 6.

[0078] [Evaluation of Volume Resistivity ρ] The measured volume resistivity ρ was evaluated as follows: "◎": If the volume resistivity ρ is 40 μΩ·cm or more and 60 μΩ·cm or less, the amount of heat generated due to energy loss is small and the value of volume resistivity ρ is sufficiently large, making it suitable for use as a resistive material or a material for a heat-generating element. "○": If the volume resistivity ρ is 35 μΩ·cm or more and less than 40 μΩ·cm, the amount of heat generated due to energy loss is small and the value of volume resistivity ρ is sufficiently large, making it usable as a resistive material or a material for a heat-generating element. "○": If the volume resistivity ρ is greater than 60 μΩ·cm and 65 μΩ·cm or less, the amount of heat generated due to energy loss is somewhat high within the acceptable range, but the value of volume resistivity ρ is sufficiently large, making it usable as a resistive material or a material for a heat-generating element. "×": If the volume resistivity ρ is less than 35 μΩ·cm, the value of volume resistivity ρ is insufficient, making it unsuitable as a resistive material or a material for a heat-generating element. "×": If the volume resistivity ρ exceeds 65 μΩ·cm, the amount of heat generated due to energy loss is too high, making it unsuitable as a resistive material or a material for a heat-generating element. In this example, "◎" and "○" were evaluated as acceptable levels.

[0079] [Evaluation of Temperature Coefficient of Resistance (TCR)] The measured temperature coefficient of resistance (TCR) was evaluated as follows: "◎": If the temperature coefficient of resistance (TCR) is between -40 ppm / °C and 0 ppm / °C, the resistance value fluctuates little over a wide temperature range from 20°C to 150°C, indicating excellent performance as a resistor. "○": If the temperature coefficient of resistance (TCR) is between -50 ppm / °C and less than -40 ppm / °C, the resistance value fluctuates reasonably little over a wide temperature range from 20°C to 150°C, indicating good performance as a resistor. "×": If the temperature coefficient of resistance (TCR) is less than -50 ppm / °C, the resistance value fluctuates greatly over a wide temperature range from 20°C to 150°C, indicating poor performance as a resistor. "×": If the temperature coefficient of resistance (TCR) exceeds 0 ppm / °C, the resistance value fluctuates significantly over a wide temperature range from 20°C to 150°C, and the resistor is considered defective.

[0080] [Evaluation of Long-Term Reliability Based on Resistivity Changes] The long-term reliability of the measured resistance changes was evaluated as follows: "◎": If the difference in volume resistivity ρ obtained by subtracting the volume resistivity after heating from the volume resistivity ρ before heating is 1% or less compared to the volume resistivity ρ before heating, the decrease in volume resistivity ρ due to heating is sufficiently small, and the reliability is excellent. "○": If the difference in volume resistivity ρ obtained by subtracting the volume resistivity ρ after heating from the volume resistivity ρ before heating is more than 1% but 1.5% or less compared to the volume resistivity ρ before heating, the decrease in volume resistivity ρ due to heating is small, and the reliability is good. "×": If the difference in volume resistivity ρ obtained by subtracting the volume resistivity ρ after heating from the volume resistivity ρ before heating is more than 1.5%, the decrease in volume resistivity ρ due to heating is large, and the reliability is poor.

[0081] [Overall Evaluation] An overall evaluation was conducted on three evaluation results from these: volume resistivity ρ, temperature coefficient of resistance (TCR), and long-term reliability. "◎": If all three evaluation results (volume resistivity ρ, temperature coefficient of resistance (TCR), and long-term reliability) are rated "◎", the overall evaluation is excellent. "○": If one or two of the three evaluation results are rated "◎" and the rest are rated "○", the overall evaluation is good. "×": If any one of the three evaluation results is rated "×", the overall evaluation is insufficient.

[0082]

[0083]

[0084]

[0085] From the results in Tables 4 to 6, the copper alloy materials of Examples 1 to 26 had alloy compositions within the appropriate range for the present invention, and all three evaluation results regarding volume resistivity ρ, temperature coefficient of resistance (TCR), and long-term reliability were rated as "◎" or "○," resulting in an overall evaluation of "◎" or "○."

[0086] Therefore, as shown in Tables 4 to 6, all of the copper alloy materials of Examples 1 to 26 were evaluated as "◎" or "〇" in the overall evaluation. As such, they possessed a volume resistivity ρ within the desired range, and their temperature coefficient of resistance (TCR) over a wide temperature range from room temperature (e.g., 20°C) to high temperature (e.g., 150°C) was either 0 or a small negative number in absolute value. Furthermore, even when heated for a long period of time in a high-temperature atmospheric environment (e.g., 200°C for 300 hours), the rate of change in volume resistivity ρ was small.

[0087] On the other hand, as shown in Tables 4 to 6, the alloy compositions of all the copper alloy materials in Comparative Examples 1 to 30 were outside the appropriate range for the present invention. Therefore, the copper alloy materials in Comparative Examples 1 to 30 were evaluated as "×" in at least one of the following: volume resistivity ρ, temperature coefficient of resistance (TCR), and long-term reliability, and were also evaluated as "×" in the overall evaluation.

Claims

1. A copper alloy material having an alloy composition containing Mn: 9.0% by mass or more, 13.0% by mass or less, Ni: 4.0% by mass or more, 6.0% by mass or less, and Co: 0.25% by mass or more, 2.0% by mass or less, with the remainder being Cu and unavoidable impurities.

2. The copper alloy material according to claim 1, wherein the copper alloy material has a metallic structure with an average grain size of 40 μm or less, and the average value of KAM measured by backscattered electron diffraction (EBSD) is 2.0° or less.

3. The copper alloy material according to claim 1, wherein the alloy composition further contains, in place of a portion of Cu, one or more components selected from the group consisting of Fe, Sn, Zn, Cr, Ag, Mg, Si, and P, each in an amount of 0.01% by mass or more and 0.50% by mass or less.

4. A resistor material comprising the copper alloy material described in claim 1, 2, or 3.

5. A resistor having the resistor material for a resistor as described in claim 4.

6. A heating element material comprising the copper alloy material described in claim 1, 2, or 3.

7. A heating element having the heating element material described in claim 6.

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