Copper alloy and relay

Abstract

To provide a copper alloy which has high hardness and high electric conductivity, and in which the deterioration of hardness and electric conductivity caused by continuous use is suppressed.SOLUTION: 0.25 mass% or more and 1.0 mass% or less of Cr and 0.03 mass% or more and 0.10 mass% or less of Si, in which a CrSi-based compound is present, and a number ratio of a 100nm group-based compound having a mean particle size of 1000nm or more and 1CrSi or less, a 10nm group-based compound having a mean particle size of 100nm or more and less than 2CrSi, and a 1CrSi group-based compound is 1 * 104 pieces / 1mm2 or more and 1 * 107 pieces / mm2 or less per measuring area, mm2, the 2CrSi base compound has a number ratio of less than 1 * 104 pieces / 1mm2 in a measured region mm2, a Vickers hardness (HV) of 80 or more and 120 or less, and a conductivity (EC) of 80% IACS or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a copper alloy and a relay. [Background technology]

[0002] Copper alloys have traditionally been used for conductive components such as connectors, lead frames, relays, switches, and sockets in automotive components, primarily for electric vehicles (EVs) and hybrid vehicles (HEVs), as well as in industrial equipment such as peripheral infrastructure and solar power generation systems. In particular, in recent years, due to the miniaturization of circuit power supplies and electronic devices, conductive components are often subjected to high voltages and high current densities. Furthermore, they must be able to withstand a wide range of operating environments, including high temperatures and high humidity. Because high voltages cause resistance heating during use, materials are required to have high mechanical properties, such as high tensile strength and hardness, with repeated use, as well as high electrical conductivity.

[0003] Traditionally, relays (electrical relays) that switch electrical circuits on and off have been used to control high-voltage and high-current-density electrical circuits in automotive components and industrial equipment. Relays in automotive components, etc., require high hardness as a mechanical property because they open and close contacts between fixed and movable components. Furthermore, relays used as switches for high-current applications require high conductivity as an electrical property to suppress resistance heating and arc generation. Until now, age-hardened copper alloys have been used as contact materials for relay contacts, as they offer superior strength and conductivity in high-temperature environments, rather than pure copper, which has excellent conductivity in high-temperature environments but poor hardness. Among these, copper-chromium (Cu-Cr) copper alloys, which have finely controlled Cr-containing second phases (crystallized and precipitated phases), are often used.

[0004] For example, Patent Document 1 discloses a method for producing a crystalline silicon alloy containing at least one of Cr, Mg, Zr, and Ti and at least one of Zn, Sn, Ag, Si, and Fe, in which, when a cross section parallel to the processing direction is observed, the aspect ratio a / b, obtained by dividing the major axis a of the particle diameter by the minor axis b, is greater than 2 and less than 5, and the minor axis b is 100 nm or more, and the number of particles having this aspect ratio a / b is 100 nm or more. 1 ~1×10 3 pieces / mm 2 Existing copper alloy sheet materials are disclosed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-052143 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if the second phase in Patent Document 1 is finely controlled, it is necessary to maintain high strength and conductivity at high temperatures. For example, if the second phase is fine, it may coarsen at high temperatures, resulting in a decrease in strength. Furthermore, since pre-processing strain from the heat treatment that controls the microstructure remains, fine phases may precipitate due to recrystallization, resulting in a decrease in conductivity. As a result, the initial metal structure before use may not be maintained, and high strength and conductivity may not be maintained over time in high-temperature environments. Therefore, there has been a demand in recent years for copper alloys that have high strength, hardness, and electrical conductivity in the initial state before use, and that maintain their high strength, hardness, and electrical conductivity even in high-temperature environments during use over time, and that are less susceptible to change over time.

[0007] Therefore, the present invention aims to provide a copper alloy that has high Vickers hardness (HV) and high electrical conductivity (EC) by controlling precipitates, in particular by controlling two different types of precipitates, and that is excellent in Vickers hardness (HV) and electrical conductivity (EC) over time and that suppresses changes in these values, and a relay that uses this copper alloy as a contact material. [Means for solving the problem]

[0008] (1) A copper alloy containing Cr: 0.25% by mass or more and 1.0% by mass or less, and Si: 0.03% by mass or more and 0.10% by mass or less, with the balance being Cu (copper) and unavoidable impurities; When CrSi-based compounds are present in the copper alloy, and among the CrSi-based compounds, CrSi-based compounds having an average particle size of 100 nm or more and 1000 nm or less are referred to as first CrSi-based compounds, and CrSi-based compounds having an average particle size of 10 nm or more and less than 100 nm are referred to as second CrSi-based compounds, the first CrSi-based compounds have a particle size of 1 mm or more when observed under an electron microscope. 2 The percentage of pieces present per unit is 1 x 10 4 pieces / mm 2 More than 1×10 7 pieces / mm 2 or less, and the second CrSi-based compound has a thickness of 1 mm2 or less in a measurement area when observed with an electron microscope. 2 The percentage of pieces present per unit is 1 x 10 4 pieces / mm 2 A copper alloy having a Vickers hardness (HV1) of 80 or more and 120 or less, and an electrical conductivity (EC1) of 80% IACS or more. (2) The copper alloy further contains at least one component selected from the group consisting of Mg, Ti, Zr, Zn, Fe, and Sn in a total amount of 0.01% by mass to 3.0% by mass. (3) The copper alloy has a Vickers hardness (HV2) of 80 or more and 120 or less after being subjected to a heat history at 350°C for 0.5 hours. (4) The copper alloy has a Vickers hardness difference (HV1-HV2) of -10 or more and +10 or less, when the Vickers hardness (HV2) after being subjected to a thermal history at 350°C for 0.5 hours is subtracted from the Vickers hardness (HV1) in the initial state before being subjected to the thermal history. (5) The copper alloy has an electrical conductivity (EC2) of 80% IACS or more after being subjected to a heat history at 750°C for 15 seconds. (6) The copper alloy has a difference in conductivity (EC1-EC2) between the electrical conductivity (EC2) after being subjected to a thermal history at 750°C for 15 seconds and the electrical conductivity (EC1) in the initial state before being subjected to the thermal history, of -4 or more and +4 or less. (7) The copper alloy has a plate thickness of 1 mm or more and 10 mm or less. (8) A relay having a contact part using the copper alloy according to (1) or (2) as a contact material. [Effects of the Invention]

[0009] The copper alloy of the present invention has excellent mechanical properties such as Vickers hardness (HV) and electrical conductivity (EC), and is capable of suppressing changes in Vickers hardness (HV) and electrical conductivity (EC) over time. It is also possible to provide a copper alloy and a relay using this copper alloy as a contact material. DETAILED DESCRIPTION OF THE INVENTION

[0010] The best mode for carrying out the present invention will be described below. However, it is easy for a person skilled in the art to modify or alter the present invention within the scope of the claims to create other embodiments, and these modifications and alterations are included in the scope of the claims. The following description is also an example of the best mode for carrying out the present invention and does not limit the scope of the claims.

[0011] The inventors have discovered a copper alloy with high Vickers hardness (HV) and electrical conductivity (EC) by appropriately distributing the second phase of fine and coarse precipitates throughout the copper alloy through a well-balanced control of fine and coarse precipitates, and have also discovered a relay using this copper alloy as a contact material.

[0012] (copper alloy) A copper alloy according to one embodiment of the present invention contains 0.25% by mass or more and 1.0% by mass or less of Cr and 0.03% by mass or more and 0.10% by mass or less of Si, with the remainder being Cu (copper) and unavoidable impurities. CrSi-based compounds are present in the copper alloy. Among these CrSi-based compounds, CrSi-based compounds having an average particle size of 100 nm or more and 1000 nm or less are referred to as first CrSi-based compounds, and CrSi-based compounds having an average particle size of 10 nm or more and less than 100 nm are referred to as second CrSi-based compounds. When the first CrSi-based compounds are observed under an electron microscope, the first CrSi-based compounds are those having an average particle size of 1 mm 2 The percentage of pieces present per unit is 1 x 10 4 pieces / mm 2 More than 1×10 7 pieces / mm 2 or less, and the second CrSi-based compound is found to be within a measurement area of ​​1 mm when observed with an electron microscope. 2 The percentage of pieces present per unit is 1 x 10 4 pieces / mm 2 The Vickers hardness (HV1) is 80 or more and 120 or less, and the electrical conductivity (EC1) is 80% IACS or more.

[0013] (Cr: 0.25 mass% or more and 1.0 mass% or less) The copper alloy of the present invention contains 0.25% by mass or more and 1.0% by mass or less of Cr. If the Cr content is less than 0.25% by mass, the amount of CrSi-based compounds is small, resulting in insufficient tensile strength, a mechanical property of the copper alloy, and in particular insufficient Vickers hardness (HV1). Insufficient Vickers hardness (HV1) makes the copper alloy susceptible to deformation in high-temperature environments where it is heated by resistance heating during use with current flow. This may result in plastic deformation exceeding the design tolerance during use as a contact material for a relay or the like, preventing the alloy from fulfilling its role as a contact material. If the Cr content exceeds 1.0 mass%, excessive CrSi compounds are produced, reducing the area of ​​the matrix, lowering electrical conductivity (EC1) and increasing contact resistance. This increases the amount of heat generated when current is applied, or the high temperature caused by arc discharge can cause Cr or Si to dissolve in the matrix at a level greater than equilibrium, resulting in a supersaturated solid solution, which reduces electrical conductivity (EC1) and thermal conductivity and may cause abnormal heat generation. Therefore, the copper alloy of the present invention contains Cr in the range of 0.25 mass % to 1.0 mass %, and preferably 0.30 mass % to 0.80 mass %.

[0014] (Si: 0.03 mass% or more and 0.1 mass% or less) The copper alloy of the present invention contains 0.03% by mass or more and 0.10% by mass or less of Si. If the Si content is less than 0.03% by mass, CrSi compounds are not formed, and a large amount of a second phase of simple Cr is formed. This makes it easier for Si to dissolve in the copper alloy at high temperatures, resulting in a decrease in electrical conductivity (EC1), an increase in electrical resistance, and a decrease in current efficiency. Furthermore, this may cause heat generation, which may lead to welding of copper alloys used in relay contacts. If the Si content exceeds 0.1 mass%, the proportion of elemental Si dissolved in the copper alloy other than the second phase of the CrSi compound increases, significantly reducing the electrical conductivity (EC1). This can result in current loss due to poor contact and heat generation due to contact resistance, potentially preventing the alloy from fulfilling its role as a contact material in a relay. Therefore, the copper alloy of the present invention contains Si in the range of 0.03 mass % to 0.1 mass %, and preferably 0.30 mass % to 0.80 mass %.

[0015] (Cr-Si compound) Cr-Si compounds are second phases in which Cr and Si form a solid solution in the Cu matrix. Cr-Si compounds in copper alloys contain a second phase that does not contain either Cr or Si, and cannot stably exist in high-temperature environments, resulting in coarsening. Furthermore, if the second phase dissolves in the matrix at a rate exceeding a certain level, the Vickers hardness (HV1) and electrical conductivity (EC1) will change, and the second phase will no longer function as a contact material in relays, so it is necessary for it to exist as a CrSi compound.

[0016] (Density of the first CrSi compound) The CrSi-based compound having an average particle size of 100 nm or more and 1000 nm or less (hereinafter referred to as "first CrSi-based compound") is present in the copper alloy in an amount of 1×10 4 pieces / mm 2 More than 1×10 7 pieces / mm 2 The first CrSi-based compound is contained in the following amount: 1×10 4 pieces / mm 2 If the content is less than 100%, much of the added Cr and Si will dissolve in the Cu matrix, reducing the electrical conductivity (EC1) and increasing the electrical resistance. Therefore, when used in relays and other devices in continuous high-temperature environments, the temperature of the contacts may rise, increasing current loss and possibly causing the relay contacts to weld together, making it impossible to open or close the relay. On the other hand, the first CrSi compound is 1×10 7 pieces / mm 2 If the temperature exceeds this value, the area of ​​the matrix at the contact point will decrease, increasing the contact resistance of the relay contact point. When an arc discharge occurs, Cr or Si will dissolve in the matrix beyond the equilibrium state, creating a supersaturated solid solution state, which may reduce the electrical conductivity (EC1) and thermal conductivity and cause abnormal heat generation.

[0017] (Density of secondary CrSi compounds) In addition, the CrSi-based compound having an average particle size of 10 nm or more and less than 100 nm (hereinafter referred to as "second CrSi-based compound") is added to the copper alloy in an amount of 1×10 4 pieces / mm 2 Included in less than 1 x 10 4 pieces / mm 2 In addition to the above, because the average particle size is small, they often dissolve into the matrix of the copper alloy in high-temperature environments, which significantly reduces the electrical conductivity (EC1) and thermal conductivity of the copper alloy, reducing the current-carrying efficiency of the relay and causing abnormal heat generation. Therefore, if the Cr and Si contents and the distribution of the first and second CrSi-based compounds in the copper alloy are within the specified ranges, the presence of the CrSi-based compounds as a second phase will make it possible to keep the Vickers hardness (HV1) and electrical conductivity (EC1) within appropriate ranges, and since electrical conductivity (EC1) and thermal conductivity are maintained and heat dissipation is good, the initial current-carrying efficiency of the relay will be maintained and it will be possible to use it normally and continuously without problems such as abnormal heat generation.

[0018] (Selectively added elements: Mg, Ti, Zr, Zn, Fe, Sn) The copper alloy of the present invention further contains at least one component selected from the group consisting of Mg, Ti, Zr, Zn, Fe and Sn in a total amount in the range of 0.01 mass % to 3.0 mass %. Of these elements, Mg, Zn, Fe, and Sn tend to dissolve in the matrix of copper alloys. Furthermore, Ti and Zr tend to dissolve partially in the matrix, while partially forming a second phase. Ti and Zr improve the tensile strength of the mechanical properties and also contribute to strengthening the Vickers hardness (HV1). Some elements that dissolve in the matrix of copper alloys have a greater effect on mechanical properties when added simultaneously than when added alone. Adding Mg, Zn, Fe, and Sn simultaneously is particularly effective compared to adding each element individually. Furthermore, elements that dissolve in the matrix of copper alloys reduce electrical conductivity (EC1), so an upper limit is set to prevent degradation. Furthermore, these elements can provide a drag effect that prevents grain boundary migration when in a solid solution state, and can suppress the growth of the average grain size of the first and second CrSi-based compounds, thereby suppressing rapid grain coarsening and effectively contributing to the control of Vickers hardness (HV1) and electrical conductivity (EC1). Therefore, if the total amount of these additive elements is less than 0.01 mass%, no effect on Vickers hardness (HV1) can be obtained. Also, if the total amount of these additive elements exceeds 3.0 mass%, when the first and second CrSi-based compound distributions are formed, this has a significant adverse effect on manufacturability during melting, casting, and hot rolling.

[0019] The selectively added elements are added in the ranges of Mg: 0.01 to 0.5 mass%, Ti: 0.01 to 0.3 mass%, Zr: 0.1 to 0.3 mass%, Zn: 0.1 to 2.0 mass%, Fe: 0.1 to 0.5 mass%, and Sn: 0.1 to 0.5 mass%.

[0020] (Mg: 0.01 mass% or more and 0.5 mass% or less) The addition of Mg can strengthen the copper alloy by dissolving in the matrix and improve its heat resistance. Furthermore, strengthening the matrix increases the Vickers hardness (HV1). Addition of less than 0.01% by mass is ineffective, while addition of more than 0.5% by mass is unsuitable because it significantly reduces electrical conductivity (EC1).

[0021] (Ti: 0.01 mass% or more and 0.3 mass% or less) The addition of Ti makes it possible to strengthen the material through solid solution or precipitation, increase the Vickers hardness (HV1), and improve heat resistance. If the content is less than 0.01% by mass, no effect can be obtained, but if the content exceeds 0.3% by mass, electrical conductivity (EC1) drops significantly and manufacturability problems such as cracking during plastic working become more likely to occur, making this unsuitable.

[0022] (Zr: 0.1 mass% or more and 0.3 mass% or less) The addition of Zr makes it possible to strengthen the material through solid solution or precipitation, increase the Vickers hardness (HV1), and improve heat resistance. If the content is less than 0.1% by mass, no effect can be obtained, while if the content exceeds 0.3% by mass, the electrical conductivity (EC1) drops significantly and manufacturability problems such as cracking during plastic working become more likely to occur, making this unsuitable.

[0023] (Zn: 0.1% by mass or more and 2.0% by mass or less) The addition of Zn strengthens the material through solid solution, increases the Vickers hardness (HV), and improves heat resistance. If the amount is less than 0.1% by mass, no effect is obtained, and if the amount exceeds 2.0% by mass, the electrical conductivity (EC) drops significantly, which is unsuitable.

[0024] (Fe: 0.1 mass% or more and 0.5 mass% or less) Adding Fe strengthens the material through solid solution, increases the Vickers hardness (HV), and improves heat resistance. If the content is less than 0.1% by mass, no effect is obtained, and if the content exceeds 0.5% by mass, electrical conductivity (EC) drops significantly, which is unsuitable.

[0025] (Sn: 0.1 mass% or more and 0.5 mass% or less) The addition of Sn strengthens the material through solid solution, increases the Vickers hardness (HV1), and improves heat resistance. If the content is less than 0.1% by mass, no effect can be obtained, and if the content exceeds 0.5% by mass, the electrical conductivity (EC1) drops significantly, which is unsuitable.

[0026] (balance: Cu and unavoidable impurities) The remainder other than the above-mentioned components is Cu and inevitable impurities. Cu forms the parent phase of the copper alloy of the present invention, and exists in a state of solid solution with the essential additive components Cr and Si or in a state of precipitated precipitates. Inevitable impurities are impurities that may be unavoidably contained in the manufacturing process of the copper alloy of the present invention. Depending on the content, inevitable impurities may be a factor in reducing electrical conductivity. Therefore, in consideration of the reduction in electrical conductivity, it is preferable to suppress the content of inevitable impurities. Examples of inevitable impurities include Pb, S, P, etc.

[0027] (Vickers hardness (HV1): 80 to 120) The copper alloy of the present invention has a Vickers hardness (HV1) in the range of 80 to 120. If the copper alloy of the present invention has a Vickers hardness (HV1) below the lower limit of 80 in its initial state before being subjected to thermal history, the hardness is insufficient and repeated contact movement will cause deformation, making it unable to fulfill its role as a contact material for a relay. On the other hand, if the copper alloy of the present invention has a Vickers hardness (HV1) above the upper limit of 120 in its initial state before being subjected to thermal history, the contact area between the contacts will be reduced and the electrical resistance will increase. Furthermore, if the copper alloy of the present invention is made to have a Vickers hardness exceeding 120 by precipitation strengthening or work hardening, when the contact material is subjected to a high-temperature environment, coarsening of second-phase precipitates will occur, and the Vickers hardness (HV1) will decrease due to reduced work strain, resulting in the same adverse effects as when the Vickers hardness is below the lower limit. Therefore, the Vickers hardness (HV1) must be at least 80 to 120 in the initial state before the thermal history is applied.

[0028] (Electrical conductivity (EC): 80 or more) The copper alloy of the present invention has an electrical conductivity (EC1) of 80% IACS or more. If the electrical conductivity (EC1) of the copper alloy of the present invention is less than 80% IACS in the initial state before being subjected to thermal history, resistance heating will increase in a high-voltage and high-current environment even during normal use, reducing the relay's current-carrying efficiency and causing abnormal heating. Therefore, the electrical conductivity (EC1) must be 80% IACS or more at least in the initial state before being subjected to thermal history.

[0029] (Vickers hardness (HV2) after thermal history) The copper alloy of the present invention has a Vickers hardness (HV2) of 80 to 120 after being subjected to a thermal history of 0.5 hours at 350°C. If the Vickers hardness (HV2) after being subjected to a thermal history is less than 80, the strength is insufficient and repeated contact movement as a contact material progresses, causing the alloy to no longer function as a relay. If the copper alloy of the present invention exceeds the upper limit of 120 for the Vickers hardness (HV2), the contact area of ​​the contact portion decreases and the electrical conductivity (EC2) increases. Furthermore, the copper alloy of the present invention needs to be precipitation strengthened or work hardened. During repeated discharge of the relay, the precipitates become coarse and the work strain is reduced, causing a decrease in the Vickers hardness (HV2). If the Vickers hardness (HV2) is below the lower limit, the alloy will no longer function as a relay contact material.

[0030] (Difference in Vickers hardness between the initial state and after thermal history (HV1-HV2)) Furthermore, the copper alloy of the present invention has a Vickers hardness difference (HV1-HV2) in the range of -10 to +10, obtained by subtracting the Vickers hardness (HV2) after thermal history at 350°C for 0.5 hours from the Vickers hardness (HV1) in the initial state. It is most preferable that the difference (HV1-HV2) between the Vickers hardness in the initial state and after thermal history does not change. It is even more preferable that the difference (HV1-HV2) between the Vickers hardness in the initial state and after thermal history is in the range of -5 to +5. This allows the copper alloy of the present invention to maintain the initial current-carrying efficiency of the relay and to be used normally and stably without problems such as abnormal heat generation, even when subjected to thermal history due to continuous use in a high-temperature environment.

[0031] (Electrical conductivity after thermal history (EC2)) The copper alloy of the present invention is required to have an electrical conductivity (EC2) of 80% IACS even after a specified thermal history is applied, specifically, after heat treatment at 750°C for 15 seconds. Relay contacts are exposed to high temperatures due to arcing when opening and closing circuits and heat generated when current is applied. Therefore, the contacts are required to maintain their initial characteristics even after undergoing a specified heat treatment as a substitute for these high temperatures. Therefore, if the electrical conductivity (EC2) falls below 80% IACS after heat treatment at 750°C for 15 seconds, the relay's current-carrying efficiency will decrease and abnormal heat generation will occur. Therefore, in the copper alloy of the present invention, the electrical conductivity (EC2) after a predetermined thermal history satisfies 80% IACS, and therefore the alloy can be used stably even when subjected to thermal history through continuous use.

[0032] (Difference in conductivity between the initial state and after thermal history (EC1-EC2)) The copper alloy of the present invention has a conductivity difference (EC1-EC2) in the range of -4 to +4, obtained by subtracting the conductivity (EC2) after heat history at 750°C for 15 seconds from the conductivity (EC1) in the initial state. It is most preferable that the difference (EC1-EC2) between the initial state and after heat history does not change. It is even more preferable that the difference (EC1-EC2) between the initial state and after heat history is in the range of -2 to +2, and the copper alloy of the present invention can be used continuously and stably even after heat history.

[0033] (plate thickness) The copper alloy of the present invention has a plate thickness of 1 mm or more and 10 mm or less. If the plate thickness is less than 1 mm, the Vickers hardness (HV1) and electrical conductivity (EC1) may deviate from the appropriate range due to the influence of thermal history during continuous use. In particular, the difference between the initial Vickers hardness (HV1) and electrical conductivity (EC1) after thermal history becomes large, and similarly, they may deviate from the appropriate range. Furthermore, if the plate thickness exceeds 10 mm, it becomes difficult to use them as relay pieces, which are the movable components of relays. As a contact material, the thickness is 1 mm or more and 10 mm or less, and more preferably 2 mm or more and 4 mm or less.

[0034] (relay) The copper alloy of the present invention contains 0.25% by mass or more and 1.0% by mass or less of Cr and 0.03% by mass or more and 0.10% by mass or less of Si, and includes a first CrSi-based compound and a second CrSi-based compound. The copper alloy has high hardness and high electrical conductivity, with a Vickers hardness (HV1) of 80 to 120 and an electrical conductivity (EC1) of 80% IACS or more, making it suitable for use in electrical contact parts such as connecting terminals, connectors, and relay contacts in movable parts of relays. In particular, the copper alloy of the present invention is suitable for use as a contact material in relay contacts, since both the Vickers hardness (HV) and electrical conductivity (EC) are within appropriate ranges for the initial state and after thermal history, allowing for continuous use in high-temperature environments.

[0035] (Manufacturing method) In the method for producing the copper alloy of the present invention, after the ingot casting step, the ingot is finished to a thickness of about 10 to 20 mm by a hot rolling step, and then undergoes a cold rolling step, a heat treatment step, and a finish cold rolling step, but the overall process can be carried out in a manner that is typical for producing Cu-Cr-based copper alloys. In addition, a finish heat treatment step at the end of the production process to remove processing strain, or a surface treatment step to remove dirt and the like on the surface of the copper alloy sheet may be carried out. In the method for producing the copper alloy of the present invention, it is necessary to select conditions for the heat treatment step that are different from conventional conditions in order to control precipitates, and the heat treatment step will be described below.

[0036] (Heat treatment process) The heat treatment step in the method for producing the copper alloy of the present invention involves repeating aging treatment at least twice at a temperature in the range of 400° C. to 550° C. for 1 hour to 8 hours. When the heat treatment process is performed only once, as in the past, the following problems arise: If the heat treatment temperature is low or the holding time is short, CrSi-based compounds with an appropriate average particle size do not precipitate sufficiently, resulting in low electrical conductivity (EC). Alternatively, fine CrSi-based compound precipitates are formed, and when used in a high-temperature environment, the high temperature causes the fine CrSi-based compound precipitates in the copper alloy of the relay contacts or relay contacts to grow and coarsen, which makes it more likely that characteristics such as Vickers hardness (HV) and electrical conductivity (EC) will change. Furthermore, if the heat treatment temperature in the heat treatment process is high or the holding time is long, large amounts of coarse CrSi compound precipitates are generated that do not contribute to increasing the Vickers hardness (HV). The CrSi compounds are generated at high density, reducing the area ratio of the parent phase, which increases the electrical resistance of the contact area. At the same time, the dislocations introduced in the previous cold rolling process disappear, reducing the Vickers hardness (HV), and the Vickers hardness (HV) will be insufficient even in high-temperature operating environments.

[0037] Therefore, the heat treatment process in the manufacturing method of the copper alloy of the present invention includes a first aging heat treatment 1, in which the alloy is aged at a temperature ranging from 400°C to 550°C for 1 hour to 8 hours. Furthermore, a cooling treatment is performed after the first aging heat treatment 1, in which the alloy is cooled at a predetermined rate. During this aging heat treatment 1 and the cooling step, fine CrSi-based compounds precipitate. The cooling treatment is performed to a temperature below 200°C, at which point CrSi-based compounds do not precipitate. Next, a second aging heat treatment 2 is performed, in which the alloy is aged at a temperature ranging from 400°C to 550°C for 1 hour to 8 hours, thereby coarsening the fine CrSi-based compound precipitates. The aging heat treatment 2 can be performed after the aging heat treatment 1 and the cooling treatment are completed, or after cold working is performed after the aging heat treatment 1. If the aging heat treatment is performed only once, fine precipitates of CrSi-based compounds are formed during the cooling treatment. When the CrSi-based compound precipitates are used in a high-temperature environment, the Cr and Si dissolve in the matrix, which can cause a decrease in the fine CrSi-based compounds and further growth of coarse CrSi-based compounds. As a result of this change in the state of precipitation of the CrSi-based compounds, the properties of the copper alloy, such as Vickers hardness (HV) and electrical conductivity (EC), change, making continuous use difficult.

[0038] Therefore, fine CrSi compounds are precipitated in the first aging heat treatment 1 and cooling process, and the fine CrSi compounds are coarsened in the second aging heat treatment 2, and then cooling treatment is performed to create a metal structure in which fine CrSi compounds are precipitated again. As a result, since Cr and Si are hardly contained in the matrix, neither coarse nor fine CrSi compounds grow further even when used in a high-temperature environment, and a stable metal structure can be obtained. Furthermore, because the metal structure is stable, a copper alloy can be obtained with little change in properties such as Vickers hardness (HV1) and electrical conductivity (EC1). Therefore, in the heat treatment step in the method for producing the copper alloy of the present invention, aging heat treatment must be performed at least twice in order to obtain stable properties such as Vickers hardness (HV1) and electrical conductivity (EC1).

[0039] (cooling rate) In the cooling step after the first aging heat treatment 1, the cooling rate is set to a range of 0.5°C / sec to 10°C / sec, and the alloy is cooled to less than 200°C. If the cooling rate exceeds 10°C / sec, the time required to pass through the cooling temperature range is short, so precipitates do not appear, and coarsening does not progress in the second or subsequent aging heat treatments. For this reason, when copper alloys are used in high-temperature environments, changes in the metal structure occur due to precipitation and solid solution, and the state in which the Vickers hardness (HV), electrical conductivity (EC), and thermal conductivity become unstable cannot be resolved. If the cooling rate is less than 0.5°C / sec, there are no problems with properties such as Vickers hardness (HV) and electrical conductivity (EC) or with the metal structure of CrSi-based compounds, but this is not realistic from the perspective of a practical cooling process.

[0040] (finishing cold rolling process) In the finish cold rolling process after the heat treatment process, the rolling reduction ratio is set to about 10 to 30%. Note that, to achieve this rolling reduction ratio range before the finish cold rolling process, the plate is subjected to hot rolling and cold rolling processes at the plate thickness stage. If the rolling reduction ratio in the finish cold rolling process is less than 10%, the Vickers hardness (HV) will be low, and if it exceeds 30%, the introduced dislocations will be highly dense, and when the copper alloy is used in a high-temperature environment, the metal structure will change and the electrical conductivity (EC) and thermal conductivity will likely decrease, making it unsuitable for practical use as a contact material. [Example]

[0041] The present invention will be described in detail based on the following examples, but the present invention is not limited to the examples shown below.

[0042] (Preparation of Examples 1-1 to 1-9, Examples 2-1 to 2-9, and Comparative Examples 1-1 to 1-9) An alloy containing the copper alloy composition shown in Table 1, with the remainder consisting of Cu and unavoidable impurities, was melted in a high-frequency melting furnace and cast to obtain an ingot. The melting and casting was carried out into a book mold (width: 110 mm, length: 130 mm, thickness: 35 mm). The obtained ingot was heated and held at 950°C for 1 to 5 hours, then hot-rolled to a thickness of approximately 12 mm, and then surface-ground 0.5 to 2 mm on one side. The hot-rolled copper alloy sheet was cold-rolled to a thickness of 3.75 mm, and then subjected to an aging treatment process in which the sheet was held at a temperature range of 400°C to 500°C for 1 to 8 hours in an inert gas environment, followed by a cooling process. The copper alloy sheet was then finished to a thickness of 3 mm by finish cold rolling. Table 1 below shows the composition of the copper alloy. Tables 2, 4, and 6 show the manufacturing conditions for the aging heat treatment process and the cooling process. Tables 3, 5, and 7 show the measurement and evaluation results.

[0043] The composition of the copper alloy is shown below. [Table 1]

[0044] (Examples 1-1 to 1-9) Examples 1-1 to 1-9 show the conditions of the first aging heat treatment 1, cooling treatment, and second aging heat treatment 2 in the heat treatment steps after cold rolling the copper alloy sheet material to 3.75 mm. In the first aging heat treatment 1, the copper alloy sheet material was held at 500°C for 2 hours, then cooled to below 200°C at 1.5°C / sec, and then held at 480°C for 2 hours in the second aging heat treatment 2.

[0045] (Aging heat treatment conditions for Examples 1-1 to 1-9) [Table 2]

[0046] (Performance evaluation) Examples 1-1 to 1-9 manufactured as described above were the first CrSi-based compound, and had a compound density (particles / mm 2 ), the density of the second CrSi-based compound, which is 10 nm or more and less than 100 nm (particles / mm 2 ) For the initial evaluation, the initial Vickers hardness (HV1) and conductivity (EC1), the Vickers hardness (HV2) and conductivity (EC2) after thermal history were applied, and for the characteristic evaluation, the difference in Vickers hardness (HV1-HV2) and the difference in conductivity (EC1-EC2) between the initial state and after thermal history were evaluated, as well as the contact characteristics.

[0047] (1) Compound density of CrSi-based compounds (particles / mm 2 ) Measurement For CrSi compounds (first CrSi compounds) between 100 nm and 1000 nm, a general-purpose SEM (scanning electron microscope) and a FE-SEM (field emission scanning electron microscope) were used, and the number of compounds presumed to be mainly composed of CrSi (analyzed concentrations greatly exceeding the concentrations of Cr and Si contained in the matrix) was measured using the attached EDX. At that time, the area of ​​the object was measured using a SEM (scanning electron microscope), and the diameter was calculated assuming that the particle was circular, and the size was taken as the average particle size.

[0048] (2) Compound density of CrSi-based compounds (particles / mm 2 ) Measurement For CrSi-based compounds (secondary CrSi compounds) of 10 nm or more but less than 100 nm, FE-SEM or TEM (transmission electron microscope) is used, and compounds that are presumed to be mainly composed of CrSi (analyzed concentrations significantly exceeding the concentrations of Cr and Si contained in the parent phase) are counted as target substances using the attached EDX. In this case, the area of ​​the object was measured using an SEM or TEM (transmission electron microscope), and the diameter was calculated assuming that the particle was circular, and the size was taken as the average particle size.

[0049] In either measurement, the measurement range is an area where 20 to 100 compounds can be confirmed, and the compound count is divided by the target area to determine the density. (If there are multiple fields of view, they are considered to be continuous.) The first CrSi compound having a particle size of 0.1 μm or more and 1.0 μm or less is 1×10 4 pieces~1×10 7 pieces / mm 2 If the second CrSi compound is contained within the range of 0.01 μm or more and less than 0.1 μm, it is regarded as appropriate and marked with a circle, and if it is outside the upper and lower limits, it is regarded as inappropriate and marked with a cross. 4 pieces / mm 2 Cases containing less than the lower limit were marked with an ◯, and cases exceeding the lower limit were marked with an X.

[0050] (Vickers hardness (HV1) measurement) The Vickers hardness (HV1) in the initial evaluation was measured by conducting five tests in accordance with the JIS standard (JIS Z 2241) on the surface of a copper alloy sheet material that had been finished to 3 mm by finish cold rolling, with the initial state being the surface of the copper alloy sheet material. The average value of the measurements was taken as the measured value. If the Vickers hardness (HV1) of the copper alloy sheet material was in the range of 80 to 120, it was considered to be good as a contact material, and if it was outside the range in any of the tests, it was considered to have insufficient performance.

[0051] (Measurement of electrical conductivity (EC1)) The conductivity (EC1) in the initial evaluation was measured by conducting conductivity measurements (two measurements) following the JIS standard (JIS H 0505). The average value of the measurements was taken as the measured value. A conductivity (EC1) of 80% IACS or higher was considered to be good for the contact material, and any test that fell outside the range was considered to have insufficient performance.

[0052] (Vickers hardness (HV2) measurement) The Vickers hardness (HV2) in the evaluation after thermal history was measured by holding the initial copper alloy sheet material, which had been finished to 3 mm by finish cold rolling, at 350°C for 0.5 hours, on its surface in five tests in accordance with the JIS standard (JIS Z 2241). The average value of the measurements was taken as the measured value. As with the initial evaluation, a contact material was deemed to be good if its Vickers hardness (HV2) was in the range of 80 to 120, and if any test result was outside the range, the performance was deemed to be insufficient.

[0053] (Measurement of electrical conductivity (EC2)) The electrical conductivity (EC2) in the evaluation after thermal history was measured by holding the initial copper alloy sheet material, which had been finished to 3 mm by finish cold rolling, at 750°C for 15 seconds, and then measuring the electrical conductivity (2 measurements) according to the JIS standard (JIS H 0505). The average value was taken as the measured value. A contact material was deemed to be good when the electrical conductivity (EC1) was 80% IACS or higher, and performance was deemed to be insufficient when any of the tests fell outside the range.

[0054] (Difference in Vickers hardness (HV1-HV2)) As a characteristic evaluation, the copper alloy of the present invention shows the difference in Vickers hardness (HV1-HV2) obtained by subtracting the Vickers hardness (HV2) after applying a thermal history at 350°C for 0.5 hours from the Vickers hardness (HV1) in the initial state. Here, if the difference in Vickers hardness (HV1-HV2) is between -10 and +10, it can actually be used, and if it is ±0, it is superior to the contact material. If it is outside this range, there is a possibility that problems may arise as an actual contact material, making it difficult to put into practical use.

[0055] (Difference in conductivity (EC1-EC2)) As a characteristic evaluation, the copper alloy of the present invention shows the difference in conductivity (EC1-EC2) obtained by subtracting the conductivity (EC2) after applying a thermal history at 750°C for 15 seconds from the conductivity (EC1) in the initial state. Here, if the difference in conductivity (EC1 - EC2) is between -4 and +4, it can actually be used, and if it is ±0, it is an excellent contact material. If it is outside this range, there is a possibility that problems may arise as an actual contact material, making it difficult to put into practical use.

[0056] (contact characteristics) In the copper alloy of the present invention, both the Vickers hardness (HV) and electrical conductivity (EC) contribute to the resistance characteristics of the contact. In particular, for continuous use in high-temperature environments, the contact material can function satisfactorily if both the Vickers hardness (HV) and electrical conductivity (EC) are within the appropriate range. Therefore, when both are within the appropriate range, the material is marked with "○", and when either the Vickers hardness (HV) or electrical conductivity (EC) is outside the range, the material exhibits insufficient characteristics and is marked with "×". In particular, when there is no change in performance before and after heat treatment, the material exhibits excellent performance as a contact material and is marked with "◎".

[0057] (Evaluation Results of Examples 1-1 to 1-9) Table 3 shows the evaluation results of Examples 1-1 to 1-9. [Table 3]

[0058] In Examples 1-1 to 1-9, the compound density of the first and CrSi-based compounds, the Vickers hardness (HV) and electrical conductivity (EC) of the initial evaluation, and the Vickers hardness (HV) and electrical conductivity (EC) after thermal history application are all within the specified ranges. Furthermore, in Examples 1-1 to 1-9, the difference in Vickers hardness (HV1-HV2) and the difference in conductivity (EC1-EC2) between the initial state and after the thermal history were applied were within the specified ranges, and the contact characteristics were evaluated as "good." In particular, in Examples 1-4 to 1-9, the difference in Vickers hardness (HV1-HV2) and the difference in conductivity (EC1-EC2) between the initial state and after the thermal history were both "0," which were particularly excellent, and the contact characteristics were evaluated as "excellent."

[0059] (Examples 2-1 to 2-9) Examples 2-1 to 2-9 show the conditions of the first aging heat treatment 1, cooling treatment, and second aging heat treatment 2 in the heat treatment steps after cold rolling a copper alloy sheet material having the composition of Sample 2 to 3.75 mm. In the first aging heat treatment 1, the copper alloy sheet material was held at 400 to 525°C for 1 to 4 hours, then cooled to less than 200°C at 1.0 to 9.0°C / sec, and then held at 400 to 525°C for 1 to 5 hours in the second aging heat treatment 2.

[0060] (Aging heat treatment conditions for Examples 2-1 to 2-9) [Table 4]

[0061] (Evaluation Results of Examples 2-1 to 2-9) Table 5 shows the evaluation results of Examples 2-1 to 2-9. [Table 5]

[0062] In Examples 2-1 to 2-9, the compound density of the first and second CrSi-based compounds, the Vickers hardness (HV) and electrical conductivity (EC) in the initial evaluation, and the Vickers hardness (HV) and electrical conductivity (EC) after thermal history application are all within the specified ranges. Furthermore, in Examples 2-1 to 2-9, the difference in Vickers hardness (HV1-HV2) and the difference in conductivity (EC1-EC2) between the initial state and after the thermal history were applied were within the specified range, and the contact characteristics were evaluated as "good." In particular, in Examples 2-5 to 2-9, the difference in Vickers hardness (HV1-HV2) and the difference in conductivity (EC1-EC2) between the initial state and after the thermal history were both "0," which were particularly excellent, and the contact characteristics were evaluated as "excellent."

[0063] (Comparative Examples 1-1 to 1-9) Comparative Examples 1-1 to 1-9 show the conditions of the first aging heat treatment 1, cooling treatment, and second aging heat treatment 2 in the heat treatment steps after the copper alloy sheets having the compositions of Samples 1 to 9 were cold rolled to 3.75 mm. In the first aging heat treatment 1, the copper alloy sheet material was held at 250 to 650°C for 0.4 to 10 hours, and then cooled to less than 200°C at a cooling rate of 2.0 to 20.0°C / sec., and then the second aging heat treatment 2 was either not carried out or held at 250 to 700°C for 0.4 to 12 hours. In Table 6, "-" indicates that the item was not implemented, and an underline "_" indicates that the item is outside the scope of the present invention.

[0064] (Aging heat treatment conditions for Comparative Examples 1-1 to 1-9) [Table 6]

[0065] (Evaluation Results of Comparative Examples 1-1 to 1-9) Table 7 shows the evaluation results of Comparative Examples 1-1 to 1-9. [Table 7]

[0066] In Comparative Examples 1-1, 1-3, and 1-5, the second aging heat treatment 2 was not performed, and therefore the compound density of the first and CrSi-based compounds is outside the specified range. Furthermore, although the initial evaluation is within the specified range, the Vickers hardness (HV2) and the electrical conductivity (EC2) after the thermal history are both outside the specified range. In particular, Comparative Example 1-1 has a large difference in electrical conductivity (EC1-EC2) between the initial state and after the thermal history, and Comparative Example 1-3 has a large difference in Vickers hardness (HV1-HV2) and electrical conductivity (EC1-EC2) between the initial state and after the thermal history, both of which are outside the specified range, resulting in a contact characteristic rating of "x." In Comparative Examples 1-2 and 1-8, the first aging heat treatment 1 and the second aging heat treatment 2 were performed at temperatures below 400°C. As a result, the compound density of the CrSi-based compound was within the specified range, but either or both of the Vickers hardness (HV2) and electrical conductivity (EC2) after the thermal history were outside the specified range. In particular, in Comparative Example 1-2, the difference in Vickers hardness (HV1 - HV2) and the difference in electrical conductivity (EC1 - EC2) between the initial state and after the thermal history were large, and in Comparative Example 1-8, the difference in Vickers hardness (HV1 - HV2) between the initial state and after the thermal history were large, falling outside the specified range, resulting in a contact characteristic rating of "x."

[0067] In Comparative Example 1-4, the cooling rate in the aging heat treatment process was fast, and the compound densities of the first and second CrSi-based compounds were outside the specified range. In addition, the electrical conductivity (EC2) after applying the thermal history was outside the specified range. As a result, the contact characteristics were evaluated as "×". In Comparative Examples 1-6 and 1-7, the first aging heat treatment 1 and the second aging heat treatment 2 were performed at temperatures outside the specified range. As a result, the compound density of the CrSi-based compound was outside the specified range, and furthermore, the electrical conductivity (EC1, EC2) in the initial evaluation and after the thermal history were both outside the specified range. As a result, the contact characteristics were marked "x." In Comparative Example 1-9, the aging temperature in the aging heat treatment step was low, so the compound densities of the first and second CrSi-based compounds were outside the specified range. In addition, the electrical conductivity (EC2) after applying thermal history was outside the specified range. As a result, the contact characteristics were evaluated as "x."

Claims

1. A copper alloy containing Cr: 0.25% by mass or more and 1.0% by mass or less, Si: 0.03% by mass or more and 0.10% by mass or less, and the balance being Cu (copper) and unavoidable impurities, a CrSi-based compound is present in the copper alloy, Among the CrSi-based compounds, a CrSi-based compound having an average particle size of 100 nm or more and 1000 nm or less is defined as a first CrSi-based compound, and a CrSi-based compound having an average particle size of 10 nm or more and less than 100 nm is defined as a second CrSi-based compound. The first CrSi-based compound has a measurement area of ​​1 mm when observed with an electron microscope. ２ The percentage of the number of pieces present per ４ pieces / mm ２ 1x10 or more ７ pieces / mm ２ is less than or equal to, and The second CrSi-based compound has a measurement area of ​​1 mm when observed with an electron microscope. ２ The percentage of the number of pieces present per ４ pieces / mm ２ is less than Vickers hardness (HV1) is 80 or more and 120 or less, A copper alloy having an electrical conductivity (EC1) of 80% IACS or more.

2. The copper alloy according to claim 1, further containing at least one component selected from the group consisting of Mg, Ti, Zr, Zn, Fe, and Sn in a total amount of 0.01% by mass or more and 3.0% by mass or less.

3. 2. The copper alloy according to claim 1, wherein the copper alloy has a Vickers hardness (HV2) of 80 or more and 120 or less after being subjected to a heat history at 350°C for 0.5 hours.

4. The copper alloy has a Vickers hardness difference (HV1-HV2) obtained by subtracting a Vickers hardness (HV2) after applying a thermal history at 350°C for 0.5 hours from the Vickers hardness (HV1) in an initial state before applying the thermal history, of -10 or more and +10 or less. The copper alloy according to claim 3.

5. 3. The copper alloy according to claim 1, wherein the copper alloy has an electrical conductivity (EC2) of 80% IACS or more after being subjected to a heat history at 750°C for 15 seconds.

6. The copper alloy has a conductivity (EC1-EC2) obtained by subtracting the conductivity (EC2) after applying a thermal history at 750°C for 15 seconds from the conductivity (EC1) in an initial state before applying the thermal history, and the difference in conductivity is -4 or more and +4 or less. The copper alloy according to claim 5.

7. The copper alloy according to claim 1 or 2, wherein the copper alloy has a plate thickness of 1 mm or more and 10 mm or less.

8. A relay having a contact portion using the copper alloy according to claim 1 or 2 as a contact material.

Images