Method for manufacturing cu-co-ni-si-cr-based copper alloy sheet having excellent strength, electrical conductivity and bendability, and copper alloy sheet manufactured thereby

Abstract

The present invention relates to: a method for manufacturing a copper alloy sheet containing, in wt%, 0.1-2.0 wt% of nickel (Ni), 0.1-2.0 wt% of cobalt (Co), 0.3-0.7 wt% of silicon (Si), and 0.05-0.3 wt% of chromium (Cr), with the remainder comprising copper (Cu) and inevitable impurities; and a copper alloy sheet manufactured thereby. The inevitable impurities are at least one element selected from the group consisting of Mg, Al, P, Ca, Sn, Fe, Zn, Zr, and Mn, and the total content of the inevitable impurities is 0.5 wt% or less.

Description

Method for manufacturing a CU-CO-NI-SI-CR copper alloy sheet having excellent strength, electrical conductivity, and bendability, and a copper alloy sheet manufactured therefrom

[0001] The present invention relates to a method for manufacturing a Cu-Co-Ni-Si-Cr-based copper alloy sheet having excellent strength, electrical conductivity, and bendability, and to a copper alloy sheet manufactured therefrom. The copper alloy sheet can be used as an automotive or electrical / electronic component, such as a connector, switch, relay, terminal, jack, lead frame, etc.

[0002] Copper alloy sheets used for automotive or electrical and electronic components, such as connectors, switches, relays, terminals, jacks, and lead frames, require high strength to withstand stresses generated during processing and operation, as well as excellent electrical conductivity to control Joule heating during current flow, depending on the application. Additionally, since these copper alloy sheets are formed into automotive or electrical and electronic components through bending, bendability is also required. Recently, due to the high integration and miniaturization of electronic components, there is a trend toward further reducing the thickness of materials used for electrical and electronic components.

[0003] To obtain excellent strength, electrical conductivity, and bendability, the use of precipitation-hardened copper alloys is increasing instead of solid solution-strengthened copper alloys. Precipitation-hardened copper alloys obtain alloy strength by aging a solution-treated supersaturated solid solution for a certain period of time to uniformly distribute fine precipitates, while simultaneously reducing dissolved elements within the copper matrix and improving electrical conductivity. As a result, required characteristics such as excellent strength, electrical conductivity, and springiness are obtained.

[0004] While Colson (Cu-Ni-Si) alloys are primarily used as precipitation-hardening copper alloys, it is known that adding cobalt (Co) to them further enhances their properties. When cobalt (Co) is added to Colson (Cu-Ni-Si) alloys, it is possible to form cobalt (Co) and silicon (Si) precipitates in which nickel (Ni) is substituted with cobalt (Co). Consequently, equivalent tensile strength and higher electrical conductivity can be achieved compared to Cu-Ni-Si alloys. Furthermore, due to the finer precipitates, bendability is also more favorable compared to Cu-Ni-Si alloys.

[0005] Korean registered patent No. 10-2021442 added chromium (Cr) to a Cu-Ni-Co-Si system and applied a thermal-mechanical precipitation process in the manufacturing method, thereby securing high strength of 720 MPa or more with a 0.2% yield strength, but the conductivity was 55% IACS to 60% IACS and did not exceed 60% IACS.

[0006] Korean Patent Publication No. 10-2007-0112868 is an invention regarding a Cu-Ni-Co-Si-Cr alloy, in which high strength, bendability, and solderability were secured by controlling the size, composition, and distribution of inclusions within the alloy, but the electrical conductivity was found to be at the level of 55% IACS.

[0007] Korean Patent Publication No. 10-2010-0113644 describes an invention regarding a Cu-Ni-Co-Si-Cr alloy, in which silicon (Si) is in excess compared to nickel (Ni) and cobalt (Co), and high strength and fatigue characteristics were secured by controlling the size and number density of Cr-Si compounds, but an electrical conductivity of 60% IACS or higher could not be secured.

[0008] The present invention provides a method for manufacturing a copper-cobalt-nickel-silicon-chromium (Cu-Co-Ni-Si-Cr)-based copper alloy sheet having a tensile strength of 700 MPa or more, an electrical conductivity of 60% IACS or more, and improved bendability, and a copper alloy sheet manufactured therefrom.

[0009] The present invention relates to a method for manufacturing a copper alloy sheet comprising nickel (Ni): 0.1 to 2.0 wt%, cobalt (Co): 0.1 to 2.0 wt%, silicon (Si): 0.3 to 0.7 wt%, chromium (Cr): 0.05 to 0.3 wt%, the remainder being copper (Cu) and unavoidable impurities, wherein the unavoidable impurities are one or more elements selected from the group consisting of Mg, Al, P, Ca, Sn, Fe, Zn, Zr, and Mn, and the unavoidable impurities are included in a total amount of 0.5 wt% or less, and the method comprises: (a) a step of melting the constituent elements to cast an ingot; (b) a step of hot rolling the obtained ingot at 900°C to 1050°C; and (c) a step of first cold rolling the product obtained in the previous step at a reduction rate of 70% or more. (d) a step of solution treatment of the first cold-rolled product at 800°C to 1050°C for 20 seconds to 300 seconds; (e) a step of rapid cooling of the solution-treated product at 20 to 300°C / s; (f) a step of first precipitation treatment of the rapid-cooled product at 400°C to 520°C for 30 minutes to 10 hours; (g) a step of second cold-rolling the first precipitation-treated product at a reduction rate of 10% to 50%; and (h) a step of obtaining a copper alloy sheet by performing a secondary precipitation treatment on the secondary cold-rolled product at 350°C to 450°C for 1 hour to 20 hours, wherein the content of nickel (Ni) and cobalt (Co) is 1.5 wt% ≤ Ni+Co ≤ 2.5 wt%, the weight ratio of nickel (Ni) and cobalt (Co) (Ni / Co or Co / Ni) is 3.0 ≤ Ni / Co or Co / Ni ≤ 6.0, and the value of the relationship (Ni+Co) / (Si-Cr / 3) of the content of nickel (Ni), cobalt (Co), silicon (Si), and chromium (Cr) is 4.0 ≤ (Ni+Co) / (Si-Cr / 3) ≤ 5.5.The copper alloy sheet has a tensile strength of 700 MPa or more and an electrical conductivity of 60% IACS or more, and an R / t value of 0.5 or less when subjected to a 180° bending workability test in the rolling parallel and rolling perpendicular directions. The average grain size in the cross-section parallel to the rolling direction of the product quenched in step (f) is in the range of 5 μm to 30 μm. The copper alloy sheet has a micro-metal structure containing (Co,Ni)2Si precipitates with an average size of 10 nm or less and chromium (Cr) precipitates with an average size of 150 nm or less, and the density of the precipitates is 1.0 x 10⁻¹⁰. 7 Pieces / cm² to 4.0*10 7 It is per square centimeter.

[0010] The present invention also provides a copper alloy sheet for electrical, electronic, and automotive parts manufactured according to a method. The copper alloy sheet has a micro-metal structure comprising (Co,Ni)2Si precipitates with an average size of 10 nm or less and chromium (Cr) precipitates with an average size of 150 nm or less, wherein the density of the precipitates is 1.0 × 10⁻⁶ 7 Pieces / cm² to 4.0*10 7 It is per square centimeter.

[0011] According to the manufacturing method disclosed in this specification, a copper alloy sheet having excellent strength, electrical conductivity, and bendability can be manufactured.

[0012] Figure 1 is a field-emission transmission electron microscope (FE-TEM) image of the specimen of Example 1, in which orthorhombic (Co,Ni)2Si precipitates and cubic chromium (Cr) precipitates were identified. The red arrow indicates the (Co,Ni)2Si precipitate.

[0013] Figure 2 is a field-emission transmission electron microscope (FE-TEM) image of the specimen of Example 1, showing the composition and diffraction pattern of the orthorhombic (Co,Ni)2Si precipitate. In the lower left section of Figure 2, 1 and 4 are the analysis results of a general area, and 2 and 3 are the (Co,Ni)2Si precipitate.

[0014] Figure 3 is a field-emission transmission electron microscope (FE-TEM) image of the specimen of Example 1, showing an example of measuring the size of orthorhombic (Co,Ni)2Si precipitates.

[0015] Figure 4 is a field-emission scanning electron microscope (FE-SEM) image of the specimen of Example 1, showing an example of measuring the grain size by analyzing a cross-section parallel to the rolling direction.

[0016] The present invention relates to a method for manufacturing a copper alloy sheet comprising nickel (Ni): 0.1 to 2.0 wt%, cobalt (Co): 0.1 to 2.0 wt%, silicon: 0.3 to 0.7 wt%, chromium (Cr): 0.05 to 0.3 wt%, the remainder being copper (Cu) and unavoidable impurities, wherein the unavoidable impurities include one or more elements from the group consisting of Mg, Al, P, Ca, Sn, Fe, Zn, Zr, and Mn, in a total amount of 0.5 wt% or less.

[0017] The above manufacturing method comprises: (a) a step in which the above-mentioned constituent elements are melted and an ingot is cast (=melting and casting step); (b) a step in which the above-mentioned ingot is hot-rolled at 900°C to 1050°C (=hot-rolling step); (c) a step in which the product obtained in the previous step is first cold-rolled at a reduction rate of 70% or more (=first cold-rolling step); (d) a step in which the first cold-rolled product is solution-treated at 800°C to 1050°C for 20 seconds to 300 seconds (=solution treatment step); (e) a step in which the solution-treated product is rapidly-cooled at 20 to 300°C / s (=rapid cooling step); (f) a step in which the rapidly-cooled product is first-precipitated at 400°C to 520°C for 30 minutes to 10 hours (=first precipitation treatment step); (g) a step in which the product of the first precipitation treatment is secondarily cold-rolled at a reduction rate of 10% to 50% (= second cold-rolling step); (h) a step in which the product of the second cold-rolled is secondarily precipitated at 350℃ to 450℃ for 1 hour to 20 hours to obtain a copper alloy sheet (= second precipitation treatment step).

[0018] First, the compositional range of the constituent elements of the copper alloy sheet according to the present invention is described in detail. In this specification, where % is indicated alone in the description of the content of constituent elements, it refers to weight %.

[0019] (1) Nickel (Ni): 0.1 to 2.0 wt%

[0020] In the copper alloy sheet according to the present invention, the nickel (Ni) content is 0.1 to 2.0 weight%. Nickel (Ni) is a solid solution strengthening element and a precipitation hardening element that forms an intermetallic compound with silicon (Si). When the nickel (Ni) content is less than 0.1 weight%, it is difficult to secure strength, and when it exceeds 2.0 weight%, the electrical conductivity is not sufficiently increased.

[0021] (2) Cobalt (Co): 0.1 to 2.0 wt%

[0022] In the copper alloy sheet according to the present invention, the content of cobalt (Co) is 0.1 to 2.0 weight%. Cobalt (Co) combines with silicon (Si) to form a large amount of fine intermetallic compounds and is an element with excellent precipitation hardening effect. When the cobalt (Co) content is less than 0.1 weight%, it is difficult to secure strength, and when it exceeds 2.0 weight%, the precipitates become coarsened due to the reduction of the solution heat treatment temperature range, thereby reducing the precipitation hardening effect.

[0023] (3) Silicon (Si): 0.3 to 0.7 wt%

[0024] In the copper alloy sheet according to the present invention, the silicon (Si) content is 0.3 to 0.7 weight%. Silicon (Si) forms (Co,Ni)2Si precipitates with nickel (Ni) and cobalt (Co) to hinder the movement of dislocations, thereby improving strength, and contributes to improving electrical conductivity by reducing the elements dissolved in the copper matrix. If the silicon (Si) content is less than 0.3 weight%, the effect of improving strength cannot be fully exerted, and if it exceeds 0.7 weight%, it is difficult to sufficiently increase electrical conductivity due to the silicon (Si) elements remaining in the copper matrix, and it also has an adverse effect on hot rolling and cold rolling.

[0025] (4) Chromium (Cr): 0.05 to 0.3 weight%

[0026] The chromium (Cr) content in the copper alloy sheet according to the present invention is 0.05 to 0.3 weight%. Chromium (Cr) contributes to the nucleation of precipitates at grain boundaries, thereby forming fine precipitates and controlling the growth of fine two-phase precipitates. This increases the density of precipitates, significantly improving strength and fatigue resistance, and some of them are formed as coarse spherical chromium (Cr) precipitates in the cubic system phase. When the chromium (Cr) content is less than 0.05 weight%, the effect on the refinement and density increase of fine two-phase precipitates is excessively insignificant, and when it exceeds 0.3 weight%, the amount of chromium (Cr) remaining in the copper (Cu) matrix is ​​large, which leads to the excessive formation of coarse spherical chromium (Cr) precipitates. This hinders the flow of electrons, thereby reducing electrical conductivity, degrading strength, and lowering bendability.

[0027] (5) Total amount of nickel (Ni) and cobalt (Co) (Ni+Co): 1.5 to 2.5 weight%

[0028] Nickel (Ni) and cobalt (Co) are the main elements that form (Co,Ni)2Si precipitates together with silicon (Si). As the total amount of nickel (Ni) and cobalt (Co) increases, the (Co,Ni)2Si precipitates increase, thereby improving strength. If the total amount of nickel (Ni) and cobalt (Co) is less than 1.5 wt%, it is difficult to secure sufficient strength; if the total amount of nickel (Ni) and cobalt (Co) exceeds 2.5 wt%, the solution treatment temperature must be raised above 1050°C. Since this is close to the melting point of copper, a problem may occur where the material partially melts during solution treatment. Therefore, the total amount of nickel (Ni) and cobalt (Co) (Ni+Co) is 1.5 to 2.5 wt%. Within the above range, tensile strength improves as the total amount of nickel and cobalt increases without melting problems during hot rolling.

[0029] (6) Weight ratio of nickel (Ni) to cobalt (Co) (Ni / Co or Co / Ni): 3.0 to 6.0

[0030] In this specification, the weight ratio of nickel (Ni) and cobalt (Co) refers to the mutual weight ratio (Ni / Co or Co / Ni). In the copper alloy composition of the present invention, the weight ratio of nickel (Ni) and cobalt (Co) (Ni / Co or Co / Ni) is 3.0 to 6.0. If the weight ratio of nickel and cobalt (Ni / Co or Co / Ni) is less than 3.0, it becomes difficult to secure electrical conductivity, and if it exceeds 6.0, it becomes difficult to control the conditions for achieving the target physical properties.

[0031] (7) Relationship between nickel (Ni), cobalt (Co), silicon (Si) and chromium (Cr), (Ni+Co) / (Si-Cr / 3): 4.0 to 5.5

[0032] The relationship between nickel, cobalt, silicon, and chromium in the composition of the copper alloy of the present invention satisfies the following equation.

[0033] 4.0 ≤ (Ni+Co) / (Si-Cr / 3) ≤ 5.5

[0034] When the value of (Ni+Co) / (Si-Cr / 3) is less than 4.0, the silicon (Si) content is high, making it easy to obtain high strength, but the electrical conductivity is significantly reduced, and silicon oxide is formed during casting, which can cause cracking during hot rolling. When the value of (Ni+Co) / (Si-Cr / 3) exceeds 5.5, it becomes difficult to secure an electrical conductivity of 60% IACS or higher.

[0035] (8) Inevitable impurities

[0036] The copper alloy sheet according to the present invention may contain unavoidable impurities. Unavoidable impurities are residues present in the melting furnace. The unavoidable impurities may be one or more elements from the group consisting of Mg, Al, P, Ca, Sn, Fe, Zn, Zr, and Mn, and may be included in a total amount (=total amount) of 0.5 weight% or less. Since a total amount of the unavoidable impurities exceeding 0.5 weight% can cause lateral cracks during hot rolling and deteriorate bendability, it is necessary to control it to 0.5 weight% or less.

[0037] (9) Remaining amount of copper (Cu)

[0038] The copper alloy sheet according to the present invention contains a remainder of copper (Cu).

[0039]

[0040] Method for manufacturing a copper alloy sheet according to the present invention

[0041] A copper alloy sheet according to the present invention is manufactured by a method comprising the following steps.

[0042] (a) Melting and casting steps

[0043] First, the constituent elements of the copper alloy sheet according to the present invention are melted, and an ingot is cast. Melting is carried out by heating to approximately 1200°C to 1350°C so that all the constituent elements of the raw material can be melted. If the melting temperature is excessively low, the fluidity of the molten metal decreases, and if it is excessively high, there is a risk that the quality of the ingot will deteriorate due to the inclusion of oxygen and hydrogen. After the melting is completed, the molten metal is stabilized at 1150°C to 1250°C for 30 minutes to 2 hours, and then the ingot is cast. The molten metal stabilization conditions can be appropriately set by a person skilled in the art based on their knowledge in the relevant field. After casting, the ingot is slowly cooled at a rate of 20°C / s or less. If rapid cooling occurs after casting, stress is generated due to the temperature difference between the inside and the surface of the casting, which can cause internal cracks and cracks during hot rolling.

[0044] The above melting and casting steps may be carried out in a general atmospheric melting furnace, such as a high-frequency atmospheric melting furnace, and in order to prevent oxidation of highly oxidizable elements such as chromium (Cr) and silicon (Si), it may be more suitable to carry out the steps in an inert gas atmosphere such as helium (He) or argon (Ar), or in a vacuum melting furnace.

[0045] (b) Hot rolling step

[0046] Next, the ingot is hot-rolled at 900°C to 1050°C. Below 900°C, precipitates may exist at the grain boundaries, which can cause hot cracking. Above 1050°C, the ingot may partially melt, potentially causing red shortness. In the present invention, to prevent the formation of precipitates during hot rolling, the product is rapidly cooled after hot rolling.

[0047] Additionally, depending on the purpose of the final copper alloy sheet obtained after hot rolling, surface grinding may be performed, and acid-washing, polishing, or degreasing may be carried out after each heat treatment.

[0048] (c) 1st cold rolling stage

[0049] Next, the product obtained in the previous step is cold-rolled with a reduction rate of 70% or more. If the reduction rate is less than 70%, it is difficult to obtain the desired physical properties in the solution treatment step (d) described later, and it is difficult to secure the target thickness for the intended use in the final product.

[0050] (d) Solution treatment step

[0051] Subsequently, the product of the first cold rolling is subjected to solution treatment at 800°C to 1050°C for 20 to 300 seconds. If the temperature of the solution treatment is below 800°C, the solubility of the solute element becomes insufficient, and if it exceeds 1050°C, a decrease in physical properties and bendability occurs due to grain coarsening. Consequently, when the solution-treated product is rapidly cooled in a subsequent stage, deformation problems of the resulting sheet material occur, making the subsequent rolling process difficult.

[0052] (e) Rapid cooling step

[0053] The solution-treated product is rapidly cooled at a rate of 20 to 300°C / s. The grain size is determined during the solution treatment and rapid cooling steps. When the solution-treated product is cooled at a rate of less than 20°C / s, dissolved cobalt (Co) elements are reprecipitated, making it difficult to secure sufficient strength during the precipitation treatment. Furthermore, as the average grain size increases, the possibility of microcracks occurring at the grain boundaries increases due to reduced strength and durability. Additionally, when the cooling rate exceeds 300°C / s, there is a risk of plate warping and deterioration of the plate shape due to internal stress in the product plate. Moreover, despite the fine grain size, there is a possibility of cracking due to sudden grain growth during the subsequent precipitation treatment step caused by thermal instability.

[0054] (f) 1st precipitation treatment step

[0055] Subsequently, the quenched product is subjected to a primary precipitation treatment at a temperature ranging from 400°C to 520°C for 30 minutes to 10 hours. In this step, Ni-Si precipitates and Co-Si precipitates are formed. At temperatures below 400°C, Co-Si precipitates do not appear effectively, and at temperatures above 520°C, the precipitates coarsen, making it difficult to secure strength.

[0056] (g) Second cold rolling step

[0057] Subsequently, the product of the first precipitation treatment is cold-rolled with a reduction rate of 10% to 50%. If the reduction rate is less than 10%, sufficient strength cannot be secured in the second precipitation treatment stage because the precipitation driving force is insufficient, and if the reduction rate exceeds 50%, bendability and electrical conductivity are significantly reduced.

[0058] (h) Secondary precipitation treatment step

[0059] Subsequently, the product of the second cold rolling is subjected to a second precipitation treatment at 350°C to 450°C for 1 to 20 hours to obtain a copper alloy sheet. When the second precipitation treatment temperature is below 350°C, the productivity is low because the second precipitation treatment must be performed for a long time due to ineffective Ni-Si precipitation, and when it exceeds 450°C, Co-Si precipitation is dominant over Ni-Si precipitation, which reduces the rate of increase in electrical conductivity and strength.

[0060] The copper alloy sheet obtained according to the manufacturing method of the present invention can then be processed in a subsequent process according to the final purpose of use.

[0061]

[0062] Characteristics of the copper alloy sheet obtained according to the manufacturing method of the present invention

[0063] The copper alloy sheet obtained according to the manufacturing method of the present invention has a tensile strength of 700 MPa or more, an electrical conductivity of 60% IACS or more, and a 180° bending workability in the rolling parallel direction and the rolling perpendicular direction with an R / t value of 0.5 or less. In addition, the copper alloy sheet obtained according to the manufacturing method of the present invention can be used as a part requiring spring properties by improving fatigue resistance through an increase in the density of precipitates due to the addition of chromium (Cr).

[0064] In copper alloy sheets, strength, electrical conductivity, and bendability are characteristics that are difficult to achieve simultaneously. Since components of small electronic products currently used in the electrical and electronic fields require the simultaneous attainment of these characteristics, copper alloy sheets possessing all of these properties are particularly excellent as materials for electronic components.

[0065] The copper alloy sheet material manufactured according to the present invention has improved strength, so when used, for example, as a support within an electronic component module, it can increase the number of semiconductor chips that can be supported. In addition, because it has excellent electrical conductivity, it can be used in high-current transport components, etc. Furthermore, it can be applied to electronic components such as switches and connectors that require excellent bendability. In addition, it can be applied to USB terminals, mobile SIM sockets, etc., that require a combination of these characteristics.

[0066] As described above, the copper alloy sheet of the present invention has excellent strength and electrical conductivity and secures excellent bendability by controlling the average size of the crystal grains and the micro-metal structure through the control of conditions in the solution treatment, rapid cooling treatment, first precipitation treatment, second precipitation treatment, and second cold rolling steps of the manufacturing method of the present invention.

[0067] In the method for manufacturing a copper alloy sheet according to the present invention, the average size of the crystal grains can be confirmed by analyzing the microstructure of the cross-section parallel to the rolling direction of the product after the rapid cooling step. In the present invention, the average size of the crystal grains in the cross-section parallel to the rolling direction after the rapid cooling step is related to the strength and bendability of the copper alloy sheet to be achieved in the present invention. In the method for manufacturing a copper alloy sheet according to the present invention, the average size of the crystal grains in the microstructure of the cross-section parallel to the rolling direction of the product after the rapid cooling step is in the range of 5㎛ to 30㎛. If the average size of the crystal grains is smaller than 5㎛, the elasticity of the material is reduced, resulting in poor spring characteristics and making it difficult to apply to parts; if it is larger than 30㎛, a decrease in strength occurs due to grain coarsening, and bendability is reduced as it becomes a crack initiation point during bending.

[0068] A copper alloy sheet produced by the method for producing a copper alloy sheet according to the present invention has a micrometal structure comprising (Co,Ni)2Si precipitates with an average size of 10 nm or less and chromium (Cr) precipitates with an average size of 150 nm or less, and the density of the precipitates is 1.0 x 10⁻⁶ 7 Pieces / cm² to 4.0*10 7 The number of pieces / cm². In the copper alloy sheet produced by the method for manufacturing a copper alloy sheet according to the present invention, analysis by field emission transmission electron microscopy (FE-TEM) reveals that (Co,Ni)2Si precipitates with an average size of 10 nm or less in the orthorhombic phase and spherical chromium (Cr) precipitates with an average size of 150 nm or less in the cubic phase are uniformly distributed within the copper matrix. In this specification, (Co,Ni)2Si precipitates is a collective term for Ni-Si precipitates and Co-Si precipitates. The precipitate that plays an important role in securing the properties of the copper alloy sheet according to the present invention is the (Co,Ni)2Si precipitate.

[0069] The above (Co,Ni)2Si precipitates are in an orthorhombic system phase, and the average size of the above (Co,Ni)2Si precipitates is 10 nm or less, and they play a role in increasing the strength of the final product by increasing the precipitation strengthening effect. In addition, the above chromium (Cr) precipitates are in a cubic system phase, and the average size of the above chromium (Cr) precipitates is 150 nm or less, which is advantageous for securing strength while suppressing the formation of discontinuous (Co,Ni)2Si precipitates.

[0070] The precipitate density of the copper alloy sheet according to the present invention is 1.0*10 7 Pieces / cm² to 4.0*10 7 It is in the range of pieces / cm². Here, the density of the precipitates of the copper alloy sheet according to the present invention substantially refers to the density of (Co,Ni)2Si precipitates, since the density of chromium (Cr) precipitates is relatively very low compared to (Co,Ni)2Si precipitates. The above precipitate density is 1.0*10 7 If it is lower than pieces / cm², the concentration of solute elements in the copper matrix is ​​high, making it difficult to secure strength and electrical conductivity, and the precipitate density is 4.0*10 7 If the value is higher than per cm², the brittleness of the final product increases due to excessive precipitation formation, which increases the likelihood of cracking during bending and reduces bendability.

[0071] Next, the present invention is explained in more detail through examples. The examples are intended to aid in understanding the invention and are not intended to be limiting.

[0072]

[0073] Examples

[0074] Examples 1 to 13

[0075] To manufacture a copper alloy sheet according to the present invention, constituent elements were melted in a general atmosphere melting furnace with the chemical compositions described in Examples 1 to 13 disclosed in Table 1 below, and ingots were prepared for each. Then, the ingots were heated at 1000°C for 1 hour in a box-type induction furnace and hot-rolled. The hot-rolled product was subjected to primary cold rolling with a reduction rate of 98% to obtain a sheet of 0.29 mm. The obtained sheet was subjected to solution treatment at 950°C for 30 seconds, and subsequently, the product was rapidly cooled at a rate of 100°C / s to 250°C / s as disclosed in Table 2.

[0076] Subsequently, as disclosed in Table 2, a first precipitation treatment was performed at 480°C for 5 hours or at 500°C for 4 hours, and a second cold rolling was performed at a reduction rate of 31% to produce a plate with a thickness of 0.2 mm. The plate subjected to the second cold rolling was again subjected to a second precipitation treatment at 380°C for 8 to 12 hours, as disclosed in Table 2. The specific conditions for each step according to each example are as disclosed in Table 2.

[0077] The obtained copper alloy plates were cut into several pieces with a width of 60 mm and a length of 300 mm and used as specimens in various test examples. The example numbers according to the composition in Table 1 were used as specimens.

[0078] Comparative Examples 1 to 19

[0079] The specimens of Comparative Examples 1 to 19 were also manufactured in the same manner as the manufacturing method of Examples 1 to 13 described above, except for the component element composition disclosed in Table 1 and the process conditions in Table 2, respectively. However, if cracks occurred during hot rolling, the process was not carried out to the next step. The Comparative Example numbers according to the composition in Table 1 were used for the specimens as they were.

[0080] Classification CuNiCoSiCr Unavoidable Impurities Ni+CoNi / Co (Indicated separately only for Co / Ni cases)(Ni+Co) / (Si-Cr / 3) Example 1 Remainder 1.60.50.480.1-2.13.24.7 Example 2 Remainder 1.60.50.480.1-2.13.24.7 Example 3 Remainder 1.60.50.480.1-2.13.24.7 Example 4 Remainder 1.60.50.480.1-2.13.24.7 Example 5 Remainder 1.60.50.480.10.05Fe2.13.24.7 Example 6 Remainder 1.60.50.480.10.1Sn2.13.24.7 Example 7 Residue 1.60.50.480.10.05P2.13.24.7 Example 8 Residue 1.60.50.480.10.05Mn2.13.24.7 Example 9 Residue 1.60.50.480.10.1Zn2.13.24.7 Example 10 Residue 1.60.50.480.1-2.13.24.7 Example 11 Residue 1.60.50.480.1-2.13.24.7 Example 12 Residue 0.51.60.480.1-2.1Co / Ni 3.24.7 Example 13 Residue 0.51.60.480.2-2.1Co / Ni 3.25.08 Comparative Example 1 Remaining part 1.60.50.480.1-2.13.24.7 Comparative Example 2 Remaining part 1.60.50.480.1-2.13.24.7 Comparative Example 3 Remaining part 1.60.50.480.1-2.13.24.7 Comparative Example 4 Remaining part 1.60.50.480.1-2.13.24.7 Comparative Example 5 Remaining part 1.60.50.60.1-2.13.23.7 ​​Comparative Example 6 Remaining part 1.60.50.480.5-2.13.26.7 Comparative Example 7 Remaining part 1.51.10.450.1-2.61.366.24 Comparative Example 8 Remaining part 0.70.60.480.1-1.31.172.91 Comparative Example 9 Remaining part 1.60.50.480.10.6Fe2.13.24.7 Comparative Example 10 Remaining part 1.60.50.480.10.6Sn2.13.24.7 Comparative Example 11 Remaining part 1.60.50.480.10.6P2.13.24.7 Comparative Example 12 Remaining part 1.60.50.480.10.6Mn2.13.24.7 Comparative Example 13 Remaining part 1.60.50.480.10.6Zn2.13.24.7 Comparative Example 14 Remaining part 1.60.50.480.1-2.13.24.7 Comparative Example 15 Remaining part 1.60.50.480.1-2.13.24.7 Comparative Example 16Janbu1.60.50.480.1-2.13.24.Comparative Example 17 Residue 0.5 2.1 0.48 0.2 -2.6 Co / Ni 4.2 6.29 Comparative Example 18 Residue 0.05 2.05 0.48 0.2 -2.1 Co / Ni 41 5.08 Comparative Example 19 Residue 0.8 1.6 0.48 0.2 -2.4 Co / Ni 2.05 8.1.

[0081] Old Splitting Rolling (°C * 1hr) 1st Cold Rolling (Reduction Rate, %) Solution Treatment (°C, s) Rapid Cooling Treatment (°C / s) 1st Precipitation Treatment (°C, hr) 2nd Cold Rolling (Reduction Rate, %) 2nd Precipitation Treatment (°C, hr) Example 1 100098950, 30200480, 531380, 8 Example 2 100098950, 30200480, 531380, 10 Example 3 100098950, 30200480, 531380, 12 Example 4 100098950, 30200460, 731380, 10 Example 5 100098950, 30200480, 531380, 10th Example 6100098950, 30200480, 531380, 10th Example 7100098950, 30200480, 531380, 10th Example 8100098950, 30200480, 531380, 10th Example 9100098950, 30200480, 531380, 10th Example 10100098950, 30100480, 531380, 10th Example 11100098950, 30250480, 531380, 10th Example 12100098950, 30200500, 431380, 10 Example 13100098950, 30200500, 431380, 10 Comparative Example 1820 (Do not proceed to the next process due to crack occurrence during hot rolling) Comparative Example 2100098770, 50200480, 531380, 10 Comparative Example 3100098820, 350200480, 531380, 10 Comparative Example 4100098950, 30200550, 331380, 10 Comparative Example 5100098950, 30200480, 531380, 10 Comparative Example 6100098950, 30200480, 531380, 10 Comparative Example 7100098950, 30200480, 531380, 10 Comparative Example 8100098950, 30200480, 531380, 10 Comparative Example 9100098950, 30200480, 531380, 10 Comparative Example 10100098950, 30200480, 531380, 10 Comparative Example 11100098950, 30200480, 531380, 10 Comparative Example 12100098950, 30200480, 531380,Comparative Example 10 13100098950, 30200480, 531380, Comparative Example 10 14100098950, 30200650, 0.0131380, Comparative Example 10 15100098950, 3015480, 531380, Comparative Example 10 16100098950, 30350480, 531380, Comparative Example 10 17100098950, 30200500, 431380, Comparative Example 10 18100098950, 30200500, 431380, Comparative Example 10 19100098950, 30200500, 431380, 10,

[0082] Test example

[0083] The average grain size of the cross-section parallel to the rolling direction after quenching treatment obtained according to each of the above examples and comparative examples, and the tensile strength, electrical conductivity, bendability, and density of precipitates of the specimens of the examples and comparative examples were measured (excluding Comparative Example 1, in which cracks occurred).

[0084] Tensile strength was tested according to the tensile test (ISO 6892) after machining the specimens. The results are shown in Table 3.

[0085] Electrical conductivity was measured using a SIGMATEST from FOERSTER at a frequency of 480 kHz after polishing the specimen surface to remove all oxide scale. The results are shown in Table 3.

[0086] The bending workability was disclosed in Table 3 according to the test method JIS H 3130, where the bending axis was in full contact for 180° (R / t≤0.5) in the direction perpendicular to the rolling direction (Good way) and in the same direction as the rolling direction (Bad way), and was marked as O if no crack occurred in the bent portion, and X if a crack occurred.

[0087] The average grain size was determined by analyzing the microstructure of a cross-section parallel to the rolling direction after the quenching step using a field emission scanning electron microscope (FE-SEM). After cold mounting, surface polishing, and etching each specimen with a cross-section parallel to the rolling direction, the grain boundaries and shape were precisely analyzed by observing them with an SEM at an acceleration voltage of 20 kV and a magnification of 2,000x. Subsequently, the average grain size was evaluated by assuming the grains within the observation area to be circles and determining their diameters. The results are shown in Table 3 and Figure 4.

[0088] The size and density of the precipitates were determined by analyzing the specimens using a field emission transmission electron microscope (FE-TEM). Each specimen was observed with a TEM at an acceleration voltage of 200 kV and a magnification of 100,000x, and the number of secondary phase particles, which are the precipitates, was counted. The density of the precipitates (particles / cm²) was calculated by dividing the total number by the total area of ​​the observation region. The results are shown in Table 3.

[0089] Images obtained for the specimen of Example 1 are disclosed in FIGS. 1 to 4.

[0090] Figure 1 is a field-emission transmission electron micrograph (FE-TEM) of the specimen of Example 1, in which (Co,Ni)2Si precipitates in an orthorhombic system and chromium (Cr) precipitates in a cubic system were identified. The red arrow indicates the (Co,Ni)2Si precipitate.

[0091] FIG. 2 is a field-emission transmission electron microscope (FE-TEM) image obtained by varying the scale of the specimen of Example 1, and the diffraction pattern and composition of the orthorhombic (Co,Ni)2Si precipitate were confirmed. In the figure disclosed at the bottom left of FIG. 2, the results of analyzing the compositions of 1, 2, 3, and 4 are presented at the bottom right, where 1 and 4 are general regions, and 2 and 3 are (Co,Ni)2Si precipitates.

[0092] Figure 3 is a field-emission transmission electron microscope (FE-TEM) image of the specimen of Example 1, showing an example of measuring the size of orthorhombic (Co,Ni)2Si precipitates. The size of the precipitates in the specimen of Example 1 was determined to be 10 nm or less.

[0093] Figure 4 is a field-emission scanning electron microscope (FE-SEM) image of the specimen of Example 1, showing an example of measuring the grain size by analyzing a cross-section parallel to the rolling direction. The average grain size of the specimen of Example 1 was determined to be approximately 11 μm.

[0094] Average grain size (㎛) and precipitate density (*10) after cracking and non-cracking during inter-rolling treatment 7Pieces / cm²) Tensile Strength (MPa) Electrical Conductivity (%IACS) Bending Workability (180°, R / t≤0.5) Good way Bad way Example 1 X 112.475162OO Example 2 X 132.274861OO Example 3 X 141.873963OO Example 4 X 132.174961OO Example 5 X 101.972864OO Example 6 X 92.175560OO Example 7 X 112.375261OO Example 8 X 102.076460OO Example 9 X 131.774364OO Example 10 X 171.673362OO Example 11 X 82.376261OO Example 12X192.375363OO Example 13X202.275264OO Comparative Example 10 Do not proceed to the next process due to cracking during hot rolling Comparative Example 2X130.965468OO Comparative Example 3X520.975951XX Comparative Example 4X130.663171XX Comparative Example 5X100.975850XX Comparative Example 6X131.174946XX Comparative Example 7X171.582146XX Comparative Example 8X70.5662461OO Comparative Example 9X122.185535OX Comparative Example 10X142.282343OX Comparative Example 11X152.380546OX Comparative Example 12X132.186039OX Comparative Example 13X90.877452OO Comparative Example 14X320.5260273XX Comparative Example 15X360.659869XX Comparative Example 16X42.476059XX Comparative Example 17X112.279055OO Comparative Example 18X121.060053OO Comparative Example 19X114.585055XX

[0095] As can be seen in Table 3 above, the copper alloy sheets of Examples 1 to 13 of the present invention have a tensile strength of 700 MPa or more and an electrical conductivity of 60% IACS or more, and the bendability is an R / t value of 0.5 or less when fully bonded at 180° in the rolling parallel direction and the rolling perpendicular direction.

[0096] In Comparative Example 1, the hot rolling temperature was low, causing lateral and surface cracks along the grain boundaries, so the process after hot rolling could not be carried out.

[0097] Comparative Example 2 had a low solution temperature of 770℃, which did not sufficiently generate a supersaturated solid solution, and the total amount of Co and Ni was insufficient, so fine two-phase precipitates were not easily formed after precipitation treatment, resulting in insufficient tensile strength.

[0098] Comparative Example 3 had an excessively long solution treatment time of 350 seconds, so the average size of the crystal grains formed after rapid cooling was coarse, and the bendability and electrical conductivity did not meet the standards.

[0099] Comparative Examples 4 and 14 were subjected to long-term and short-term precipitation treatments, respectively, at a temperature higher than the primary precipitation treatment temperature of 520℃, causing the precipitates to grow and form coarsely. As a result, the density of the precipitates was low and the tensile strength was insufficient.

[0100] Comparative Example 5 had a (Ni+Co) / (Si-Cr / 3) value lower than that presented in the present invention. Consequently, it failed to form (Co,Ni)2Si precipitates, and the residual Si was high, resulting in low electrical conductivity and failure to meet the standards for bendability.

[0101] Comparative Example 6 had a chromium (Cr) content of 0.5 wt%, and the (Ni+Co) / (Si-Cr / 3) value exceeded 6.7. As a result, effective (Co,Ni)2Si precipitates were not formed, and due to the influence of residual chromium (Cr), the precipitates grew coarsely, and the electrical conductivity and bendability were measured to be outside the standard.

[0102] Comparative Example 7 had a Ni+Co value of 2.6 wt%, which exceeded the range defined in the present invention. As a result, although the strength of the obtained specimen increased, the electrical conductivity was significantly lower at 46% IACS, making it impossible to secure 60% IACS or higher.

[0103] Comparative Example 8 had a Ni+Co value of 1.3 wt%, which did not reach the lower limit of the range defined in the present invention, which is 1.5 wt%. As a result, a supersaturated solid solution was not effectively formed, and the precipitate density of the specimen of Comparative Example 8 was low, so the tensile strength did not reach 700 MPa.

[0104] Comparative Examples 9 to 13 had a total amount of 0.5% by weight, which is the range limited by the present invention, in which the content of unavoidable impurities was poor, or coarse intermetallic compounds were formed, resulting in reduced bendability.

[0105] Comparative Examples 15 and 16 had cooling rates of 15℃ / s and 350℃ / s, respectively, during the rapid cooling treatment step. In Comparative Example 15, the rapid cooling rate was slow, so coarse grains were formed after solution treatment, and the tensile strength and bendability of the copper alloy sheet obtained deviated from the standard values. In Comparative Example 16, the rapid cooling rate was excessively fast, so the grain size was excessively small, and cracks occurred during bending, failing to satisfy 180° and R / t≤0.5.

[0106] Comparative Example 17 had a cobalt content that exceeded the upper limit, a total amount of nickel and cobalt that exceeded the upper limit, and a value of the relationship formula for nickel, cobalt, silicon, and chromium of the present invention that exceeded the upper limit, so the electrical conductivity was insufficient.

[0107] Comparative Example 18 had an excessively low nickel (Ni) content of 0.05 wt%, resulting in a low density of (Co,Ni)2Si precipitates, and both strength and electrical conductivity did not reach the target values.

[0108] Comparative Example 19 had a Co / Ni value of less than 3, and the precipitate density was excessively high, resulting in poor electrical conductivity and bendability.

Claims

1. A method for manufacturing a copper alloy sheet comprising nickel (Ni): 0.1 to 2.0 wt%, cobalt (Co): 0.1 to 2.0 wt%, silicon (Si): 0.3 to 0.7 wt%, chromium (Cr): 0.05 to 0.3 wt%, the remainder being copper (Cu) and unavoidable impurities, wherein the unavoidable impurities are one or more elements selected from the group consisting of Mg, Al, P, Ca, Sn, Fe, Zn, Zr, and Mn, and the unavoidable impurities are included in a total amount of 0.5 wt% or less. The above method is, (a) A step in which the above-mentioned component elements are melted and an ingot is cast; (b) a step of hot rolling the obtained ingot at 900°C to 1050°C; (c) A step in which the product obtained in the previous step is first cold-rolled with a reduction rate of 70% or more; (d) a step in which the above-mentioned first cold-rolled product is solution-treated at 800°C to 1050°C for 20 seconds to 300 seconds; (e) a step in which the solution-treated product is rapidly cooled at 20 to 300℃ / s; (f) a step in which the above-mentioned rapid-cooled product is subjected to a first precipitation treatment at 400℃ to 520℃ for 30 minutes to 10 hours; (g) a step of secondarily cold rolling the product subjected to the first precipitation treatment at a reduction rate of 10% to 50%; and (h) A step in which the above secondary cold-rolled product is subjected to secondary precipitation treatment at 350°C to 450°C for 1 to 20 hours to obtain a copper alloy sheet. Includes, A method wherein the content of nickel (Ni) and cobalt (Co) is 1.5 wt% ≤ Ni+Co ≤ 2.5 wt%, the weight ratio of nickel (Ni) and cobalt (Co) (Ni / Co or Co / Ni) is 3.0 ≤ Ni / Co or Co / Ni ≤ 6.0, and the value of the relationship (Ni+Co) / (Si-Cr / 3) of the content of nickel (Ni), cobalt (Co), silicon (Si), and chromium (Cr) is 4.0 ≤ (Ni+Co) / (Si-Cr / 3) ≤ 5.

5.

2. In Paragraph 1, The above copper alloy sheet has a tensile strength of 700 MPa or more and an electrical conductivity of 60% IACS or more, and a method in which the R / t value is 0.5 or less when subjected to a 180° bending workability test in the rolling parallel direction and the rolling perpendicular direction.

3. In Paragraph 1, (f) A method in which the average grain size in a cross-section parallel to the rolling direction of the product quenched in step (f) is in the range of 5 μm to 30 μm.

4. In Paragraph 1, The above copper alloy plate has a micro-metallic structure containing (Co,Ni)2Si precipitates with an average size of 10 nm or less and chromium (Cr) precipitates with an average size of 150 nm or less, and the density of the precipitates is 1.0 * 10 7 Pieces / cm² to 4.0*10 7 Method of one / cm².

5. Copper alloy sheet for electrical and electronic and automotive parts manufactured according to the method disclosed in any one of claims 1 to 4.

6. In Paragraph 5, The above copper alloy plate has a micro-metallic structure containing (Co,Ni)2Si precipitates with an average size of 10 nm or less and chromium (Cr) precipitates with an average size of 150 nm or less, and the density of the precipitates is 1.0 * 10 7 Pieces / cm² to 4.0*10 7 Copper alloy sheet material with a thickness of 1 / cm².

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