JP2019167613A - Cu-Ni-Si BASED COPPER ALLOY STRIP EXCELLENT IN DIE WEAR RESISTANCE AND PRESS PUNCHABILITY - Google Patents

Abstract

To provide a Cu-Ni-Si based copper alloy that has an excellent strength and electrical conductivity, and an excellent die wear resistance and press punchability.SOLUTION: Provided is a Cu-Ni-Si based copper alloy, containing, in mass%, Ni: 3.0 to 5.0%, Si: 0.5 to 1.5%, the balance consisting of Cu and inevitable impurities, 0.2% yield stress YS in the rolling parallel direction is 950 to 1300 MPa, elongation EL in the rolling right-angle direction is 3% or less, conductivity is 25% IACS or more, and (0.2% yield strength YS in the rolling parallel direction)/(elongation EL in the rolling right-angle direction) is 317 to 1300 (MPa/%), and furthermore, the spring deflection limit value in the rolling right-angle direction is 850 MPa or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a Cu—Ni—Si based copper alloy strip suitable for conductive spring materials such as connectors, terminals, relays, switches, and the like, and a method of manufacturing the same.

Copper alloys used as current-carrying parts such as connectors, relays, and switches are required to have high conductivity in order to suppress the generation of Joule heat due to current flow, and during assembly and operation of electrical and electronic equipment. It is required to have a high strength that can withstand the applied stress.
In response to this demand, demand for precipitation strengthened copper alloys such as Corson alloys having high strength and conductivity is increasing instead of conventional solid solution strengthened copper alloys such as phosphor bronze and brass. A Corson alloy is an alloy in which an intermetallic compound such as Ni-Si, Co-Si, Ni-Co-Si is precipitated in a Cu matrix, and has high strength, high electrical conductivity, and good bending workability. .

  In recent years, with the progress of high integration, miniaturization, and weight reduction of electrical and electronic parts such as connectors, there has been an increasing demand for thinning of copper alloys as materials of such electrical and electronic parts. Yes. Furthermore, since these electric / electronic parts are generally formed by bending after press punching, they are also required to have excellent press punchability and mold wear resistance.

Conventionally, as a method for improving the press punchability of a Corson alloy, attention has been paid to chemical components such as addition of trace components such as Pb and Cd, or dispersion of a compound that is a starting point of fracture. However, such a method is difficult to control a trace amount component, deteriorates other characteristics, and leads to an increase in cost. Therefore, a method for improving press punchability by a method other than a chemical component has been studied. .
For example, Patent Documents 1 and 2 describe techniques for controlling the degree of integration of crystal orientations on the surface of a Cu—Ni—Si-based copper alloy, and Patent Documents 3 and 4 describe Cu—Ni—Co—Si. A technique for controlling the particle size and number density of precipitates of a copper alloy is disclosed.

In addition, many age-hardening copper-based alloys such as Corson alloys contain active elements, and tend to wear out press dies significantly compared to phosphor bronze, and suppression of mold wear is desired. . When the press die is worn, burrs and sagging occur on the cut surface of the workpiece, resulting in a decrease in the processed shape and an increase in manufacturing cost.
Therefore, Patent Document 5 discloses a technique for controlling the component composition of a Cu—Ni—Si based copper alloy. Patent Document 6 reports a technique for controlling the size and number density of second phase particles of a Cu—Ni—Si based copper alloy.

JP 2000-73130 A JP 2008-95185 A JP 2014-156623 A JP 2017-43789 A JP-A-11-256256 Japanese Patent No. 5189708

However, in the case of the techniques described in Patent Documents 1 and 2, the press punchability is improved, but the strength is not sufficient.
In the case of the techniques described in Patent Documents 3 and 4, although the press punchability is improved, since Co is added to the Cu—Ni—Si based copper alloy, there are many coarse second-phase particles and the mold wear resistance. Decreases.
In the case of the techniques described in Patent Documents 5 and 6, although the wear resistance of the mold is improved, the strength is not sufficient.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a Cu—Ni—Si based copper alloy that is excellent in strength and conductivity, excellent in mold wear resistance and press punchability.

The inventor of the present invention pays attention to reducing the shear plane ratio at the press fracture surface after pressing as a factor for improving the press punchability of the Cu—Ni—Si based copper alloy. The higher the strength, the smaller the shear plane ratio. I found out that
Further, it has been found that the mold wear resistance decreases as the elongation increases.
As a method for controlling strength and elongation, attention was paid to low-temperature annealing hardening in strain relief annealing. Low-temperature annealing hardening is a phenomenon in which when rolling strain is introduced into a structure by cold rolling after aging, solid solution elements are fixed to the strain by subsequent strain relief annealing and are strengthened by preventing dislocation.

  In the low-temperature annealing hardening, the degree of hardening varies depending on the degree of cold rolling work immediately before strain relief annealing and the degree of precipitation of the solid solution element during the cold rolling. However, if the strength is increased too much by cold rolling and low-temperature annealing hardening, pay attention to the degree of precipitation of solid solution elements that promote mold wear during pressing, and heat treatment is performed at a low temperature before strain relief annealing. By defining the relationship between the degree of processing at the time and the degree of precipitation (conductivity EC), we succeeded in improving the 0.2% yield strength to 950 MPa or more.

  In order to achieve the above object, the Cu—Ni—Si based copper alloy of the present invention contains, by mass%, Ni: 3.0 to 5.0%, Si: 0.5 to 1.5%, The balance is made of Cu and inevitable impurities, 0.2% proof stress YS in the rolling parallel direction is 950 to 1300 MPa, elongation EL in the perpendicular direction of rolling is 3% or less, conductivity is 25% IACS or more, and (rolling parallel direction 0.2% yield strength YS) / (elongation EL in the direction perpendicular to rolling) is 317 to 1300 (MPa /%), and the spring limit value in the direction perpendicular to rolling is 850 MPa or more.

In the Cu—Ni—Si based copper alloy of the present invention, the spring limit value is preferably 900 MPa or more.
The Cu—Ni—Si based copper alloy of the present invention preferably further contains 0.005 to 1.0 mass% in total of at least one selected from the group consisting of Mg, Mn, Sn, Zn and Cr.
The Cu—Ni—Si based copper alloy of the present invention further contains at least one selected from the group of P, B, Ti, Zr, Al, Fe and Ag in a total amount of 0.005 to 1.0 mass%. It is preferable.

  According to the present invention, it is possible to obtain a Cu—Ni—Si based copper alloy that is excellent in strength and electrical conductivity, excellent in mold wear resistance and press punchability.

It is a figure which shows the correlation with the electrical conductivity before strain relief annealing, and the processing rate RE of cold rolling. It is a figure which shows the evaluation method of metal mold | die wear resistance.

  Hereinafter, the Cu—Ni—Si based copper alloy according to the embodiment of the present invention will be described. In the present invention, “%” means “% by mass” unless otherwise specified.

(composition)
[Ni and Si]
The copper alloy contains Ni: 3.0 to 5.0% and Si: 0.5 to 1.5%. Ni and Si form an intermetallic compound by performing an appropriate heat treatment, and improve the strength without deteriorating the electrical conductivity.
When the content of Ni and Si is less than the above range, the effect of improving the strength cannot be obtained, and when the content exceeds the above range, the electrical conductivity is lowered and the hot workability is lowered.
In addition, since a large amount of solid solution element is required to develop the above-described low-temperature annealing hardening, the contents of Ni and Si are increased in the present invention.

[Other additive elements]
The alloy may further contain 0.005 to 1.0% by mass in total of at least one selected from the group consisting of Mg, Mn, Sn, Zn and Cr.
Mg improves strength and stress relaxation resistance. Mn improves strength and hot workability. Sn improves the strength. Zn improves the heat resistance of the solder joint. Since Cr forms a compound with Si like Ni, it improves the strength without deteriorating conductivity by precipitation hardening.
Moreover, you may contain 0.005-1.0 mass% of at least 1 sort (s) chosen from the group of P, B, Ti, Zr, Al, Fe, and Ag further in a total amount in an alloy. When these elements are contained, product characteristics such as conductivity, strength, stress relaxation characteristics, and plating properties are improved.
In addition, when the total amount of each element described above is less than the above range, the above effect cannot be obtained, and when it exceeds the above range, the conductivity may be lowered.

[0.2% yield strength]
The 0.2% yield strength of the Cu-Ni-Si based copper alloy in the rolling parallel direction is 950 to 1300 MPa. The reason for paying attention to the 0.2% yield strength in the rolling parallel direction is that the yield strength (strength) is generally represented by a value in the rolling parallel direction.
In order to improve the press punchability of the material, it is effective to reduce the shear plane ratio at the press fracture surface after pressing. However, the higher the strength, the smaller the shear plane ratio. Therefore, when the 0.2% proof stress is 950 MPa or more, the press punchability is improved.
However, if the 0.2% proof stress is too high, a precipitate with high hardness is generated, and the high shear surface comes into contact with the mold due to the precipitate and promotes mold wear. Is the upper limit.
The 0.2% proof stress is obtained at room temperature by preparing a JIS 13B test piece using a press and performing a tensile test according to JIS-Z2241.

[Elongation]
The elongation in the direction perpendicular to the rolling direction of the Cu—Ni—Si based copper alloy is 3% or less. Electronic materials such as terminals and connectors are often manufactured by being punched so that their longitudinal direction is parallel to the direction perpendicular to the rolling direction of the copper alloy strip, and the elongation in the direction perpendicular to the rolling evaluates the press punching property. It is effective for.
When the elongation becomes small, the shear surface ratio in the press fracture surface after pressing tends to be small, and when the elongation in the direction perpendicular to the rolling is reduced to 3% or less, the press punching property is improved. Further, when the copper alloy material is punched with a mold, the resistance is punched out with little resistance, so that the contact between the mold and the copper alloy material is suppressed, and the mold wear resistance is improved.

The lower limit of elongation is not particularly limited, but is, for example, 1%.
Further, the elongation is elongation at break, and was measured simultaneously with the above-described 0.2% proof stress according to JIS-Z2241 using a tensile tester. And the difference of the length L (gauge length) between the gauge points when the test piece broke and the gauge distance L0 before the test was obtained in%.

[(0.2% yield strength in the rolling parallel direction) / (elongation in the direction perpendicular to the rolling)]
As described above, in order to improve the press punchability, it is effective to reduce the shear plane ratio in the press fracture surface after pressing, the higher the strength in the rolling parallel direction, the smaller the elongation in the direction perpendicular to the rolling. The shear plane ratio becomes small. However, if the strength is increased too much, the wear resistance of the mold decreases.
Therefore, by defining the ratio of 0.2% proof stress YS in the rolling parallel direction and the elongation EL in the direction perpendicular to the rolling (YS / EL), it is considered that it becomes a better index of press punchability and die wear resistance. . When the ratio (YS / EL) satisfies 317 to 1300 (MPa /%), press punchability and die wear resistance are improved.

  When the ratio (YS / EL) is less than 317 (MPa /%), the shear surface at the press fracture surface after pressing becomes large, and the press punchability is deteriorated. If the ratio (YS / EL) is greater than 1300 (MPa /%), the strength becomes too high, so that the precipitate with high hardness and the shear surface with high hardness due to the precipitate are in contact with the mold, Mold wear resistance is reduced.

[Spring limit value]
The spring limit value in the direction perpendicular to the rolling of the Cu—Ni—Si based copper alloy is 850 MPa or more. As described above, electronic materials such as terminals and connectors are often manufactured by stamping so that their longitudinal direction is parallel to the direction perpendicular to the rolling direction of the copper alloy strip, and the spring limit value in the direction perpendicular to the rolling direction is often produced. It is effective for evaluating press punchability.

In general, by performing strain relief annealing, the spring limit value is improved. However, in the alloy of the present invention, when low temperature annealing hardening is performed during strain relief annealing, the 0.2% proof stress is improved and the spring limit value is increased. It becomes higher than 850 MPa.
When the spring limit value is less than 850 MPa, the resistance increases when the material is punched with a die, and the press punching property is deteriorated.
The upper limit of the spring limit value is not particularly limited, but is, for example, 1250 MPa or less.
The spring limit value in the direction perpendicular to the rolling direction is determined by the moment type test specified in JIS-H3130. The maximum surface stress was measured from the bending moment to be generated.

[Average crystal grain size]
By refining the crystal grain size, high strength can be obtained, so that the shear surface at the press fracture surface after pressing is reduced, and the press punchability is improved. Since the crystal grain size of the final product is the same as that after the solution treatment, it is preferable that the average crystal grain size of the rolled parallel section after the solution treatment is 20 μm or less. When the average crystal grain size exceeds 20 μm, the press punchability may be lowered because the strength is lowered.
On the other hand, when the average crystal grain size is smaller than 10 μm, a part of the metal structure becomes non-recrystallized, and when the non-recrystallized part remains, the press punching property decreases, so the average crystal grain size is set to 10 to 20 μm. Is preferred.
The average crystal grain size is measured based on JIS-H0501 (cutting method).

<Manufacturing method>
The Cu—Ni—Si based copper alloy of the present invention is usually obtained by performing an ingot in the order of hot rolling, cold rolling, solution treatment, aging treatment, low temperature heat treatment, cold rolling after low temperature heat treatment, and strain relief annealing. Can be manufactured. Cold rolling and recrystallization annealing before solution treatment are not essential, and may be performed as necessary.

<Solution treatment>
The solution treatment may be performed at a temperature of 800 to 950 ° C. Thereby, the solid solution of Ni and Si advances. When this temperature is less than 800 ° C., recrystallization of the mother phase and the above solid solution do not sufficiently proceed, and the press punchability may be deteriorated. On the other hand, when the temperature exceeds 950 ° C., the grain size becomes coarse and the strength improvement due to the strengthening of the crystal grain boundary becomes small, so the strength is lowered and the press punchability may be lowered. The heating time can be 15 to 300 seconds.
The average crystal grain size of the copper alloy increases as the solution treatment temperature increases, and decreases as the temperature decreases. Further, the average crystal grain size increases as the heating time increases and decreases as the heating time decreases. Therefore, by adjusting the temperature of the solution treatment and the heating time, the average crystal grain size after the solution treatment (same as the average crystal grain size of the final product) can be controlled to 10 to 20 μm.

Furthermore, in order to improve the 0.2% yield strength and conductivity of the copper alloy, the cooling rate after the solution treatment is about 10 ° C./second or more, preferably about 15 ° C./second or more, more preferably about 20 ° C. / Second or more, and may be cooled to about 400 ° C. to room temperature.
If the cooling rate is less than 10 ° C. per second, the amount of solid solution elements (Ni and Si) may decrease, and the 0.2% yield strength may decrease.
However, if the cooling rate is too high, the 0.2% proof stress is difficult to improve. Therefore, the cooling rate is about 30 ° C./second or less, preferably about 25 ° C./second or less.
Here, the “cooling rate” is measured by measuring the cooling time from the solution treatment temperature (800 ° C. to 950 ° C.) to 400 ° C. and calculated by (solution treatment temperature−400) (° C.) / Cooling time (seconds). Value (° C./second).

<Aging treatment>
The aging treatment is preferably performed at a temperature of 400 to 550 ° C. When this temperature is lower than 400 ° C., the conductivity is lowered, and when it is higher than 550 ° C., the strength may be lowered. The heating time can be performed in the range of 1 to 15 hours.

<Cold rolling after low temperature heat treatment>
As a technique for increasing the 0.2% proof stress of the Cu—Ni—Si based copper alloy in the rolling parallel direction and decreasing the elongation in the direction perpendicular to the rolling, low temperature annealing hardening in strain relief annealing is used. Low-temperature annealing hardening is a phenomenon in which when rolling strain is introduced into a structure by cold rolling after aging, solid solution elements are fixed to the strain by subsequent strain relief annealing and are strengthened by preventing dislocation.
For this purpose, it is necessary to increase the working rate of cold rolling after low-temperature heat treatment immediately before strain relief annealing and increase the amount of solid solution elements (Ni and Si) immediately before strain relief annealing.
In order to further increase the amount of the solid solution element immediately before the strain relief annealing, the “low temperature heat treatment” described later in detail is performed before the cold rolling after the low temperature heat treatment.

  In the low-temperature annealing hardening, the degree of hardening varies depending on the degree of cold rolling after low temperature heat treatment just before strain relief annealing and the degree of precipitation of solid solution elements during the cold rolling. However, if the strength is increased too much by cold rolling and low-temperature annealing hardening, there is a risk of accelerating die wear during pressing, so pay attention to the degree of solid solution element precipitation just before strain relief annealing. Heat treatment is performed at a low temperature before annealing, and the 0.2% proof stress is improved to 950 MPa or more by defining the relationship between the degree of processing during manufacture and the degree of precipitation (conductivity EC).

Specifically, the processing rate RE of the cold rolling after the low-temperature heat treatment is set to 70% or more and less than 90%, and the processing rate RE of the cold rolling after the low-temperature heat processing is expressed by the formula (1): RE ≧ −0.3074 × (EC ) It is preferable to satisfy ² + 11.986 × EC-18.934. EC (% IACS) is the electrical conductivity before strain relief annealing (after low temperature heat treatment and cold rolling).
If the processing rate RE is less than 70%, the low-temperature annealing hardening may be insufficient and the 0.2% yield strength may be less than 950 MPa. If the processing rate RE is 90% or more, the sample may be cracked during cold rolling, and the final product may not be manufactured.
The processing rate RE is the rate (%) of change in the plate thickness of the alloy before and after cold rolling after low-temperature heat treatment.

  In addition, since the minimum processing rate required also changes depending on the degree of precipitation strengthening (solid solution) of the alloy during cold rolling after low-temperature heat treatment, it is necessary to set the processing rate according to the degree of solid solution . And as the degree of this solid solution, the electric conductivity EC (% IACS) in the rolling parallel direction after low-temperature heat treatment, cold-rolling and before strain relief annealing is used as an index, and it is necessary in the formula (1) calculated from the above-mentioned conductivity. By defining a low processing rate, the strength of the alloy can be stably improved.

Here, by setting the above-mentioned conductivity EC (% IACS) to 25% or more and less than 40%, the conditions of aging treatment and strain relief annealing are both appropriate, and the strength increases in both treatments, resulting in high strength. Is obtained. When the electrical conductivity EC is 40% or more, the strength increases by aging treatment, but the amount of solid solution decreases, so even if the processing rate RE is increased, the strength is not sufficiently increased by strain relief annealing, and the desired strength is increased. It may not be obtained. On the other hand, when the electrical conductivity EC is less than 25%, the strength is increased by strain relief annealing, but the strength is not increased by aging treatment, and a desired strength may not be obtained.
Note that the electrical conductivity EC (% IACS) of the final product after strain relief annealing is about 25 to 40%.

And, as the electrical conductivity EC before strain relief annealing is lower, the increase in strength due to the aging treatment is smaller. Therefore, unless the processing rate RE is increased and a larger number of rolling strains are introduced, the required strength cannot be improved. Therefore, it is preferable to set the processing rate RE so as to satisfy the formula (1): RE ≧ −0.3074 × (EC) ² + 11.986 × EC-18.934. This equation (1) is obtained from preliminary experiments as shown in Table 1 and FIG.

In this preliminary experiment, an ingot having the composition shown in Table 1 was subjected to hot rolling, cold rolling, solution treatment, aging treatment, low-temperature heat treatment, cold rolling after low-temperature heat treatment, and strain relief annealing in the order of sheet thickness of 0. A 05 mm sample was manufactured and its characteristics were evaluated. Hot rolling was performed at 1000 ° C. for 3 hours, and solution treatment was performed at 800 to 950 ° C. The aging treatment was performed at 400 ° C. to 550 ° C. for 1 to 15 hours.
The low-temperature heat treatment was performed in the range of 550 to 800 ° C., and the heating time was adjusted in the range of 1 to 250 seconds so that ΔEC described later was 2.0%. Then, prior experiments 1 to 8 were performed by changing the electrical conductivity EC before strain relief annealing and the cold rolling after-low temperature heat treatment ratio RE as shown in Table 1.

Next, the relationship between the processing rate RE and the electrical conductivity EC shown in Table 1 is plotted in FIG. 1, and for Experiments 1 to 3 in which the 0.2% proof stress YS in the rolling parallel direction is 950 MPa or more, the least square method is used. A quadratic curve passing through each plot was obtained to obtain Equation (1).
On the other hand, in Experiments 6 and 7, the 0.2% proof stress was less than 950 MPa, and the RE was lower than that in the formula (1). Experiments 5 and 8 are on the formula (1) or in a region where the RE is higher than the formula (1). However, the experiment 5 has a processing rate RE of less than 70% and a 0.2% proof stress of less than 950 MPa. In No. 8, the processing rate RE was 90% or more, and cracks occurred in the sample during cold rolling, and the final product could not be manufactured.

In Experiment 4, the processing rate RE was almost the same (70%) as in Experiment 1, the conductivity EC was increased, and the 0.2% proof stress was 1000 MPa or more. Experiment 4 is data for indicating that the region where the RE is higher than that of the formula (1) is a preferable range of the present invention.
From the above results, in order to achieve the targets of 0.2% proof stress and die wear resistance, the processing rate RE of cold rolling after low-temperature heat treatment should be 70% or more and less than 90% and satisfy the formula (1). There is a need to.

  When the processing rate RE does not satisfy the formula (1), the processing rate RE is too small with respect to the strength after the aging treatment, and thus the required strength may not be improved.

<Low temperature heat treatment>
Further, the above-described low-temperature heat treatment is performed in order to increase the amount of the solid solution element immediately before the strain relief annealing. The low-temperature heat treatment is performed at a temperature lower than the solution temperature and higher than the aging temperature. In the low-temperature heat treatment, the solid solution element precipitated by the aging treatment is again dissolved in the matrix, so that the amount of the solid solution element immediately before the strain relief annealing increases.
Then, as an index representing the amount of the solid solution element immediately before the strain relief annealing, the change amount ΔEC of the conductivity after the aging treatment (that is, before the low temperature heat treatment) and after the low temperature heat treatment is used. ΔEC = (conductivity after aging treatment) − (conductivity after low-temperature heat treatment). Low temperature heat treatment may be performed at 550 to 800 ° C. for 1 to 250 seconds so that ΔEC = 2 to 4% (IACS).
If the amount of the solid solution element is increased by the low-temperature heat treatment immediately before the strain relief annealing as compared with that after the aging treatment, the conductivity is lowered.

When ΔEC is less than 2% IACS, it indicates that the amount of solid solution elements in the material after low-temperature heat treatment (before strain relief annealing) is small. When the amount of the solid solution element is small during the strain relief annealing, the amount of the solid solution element fixed to the dislocation by the strain relief annealing is decreased, and the degree of curing in the low temperature annealing hardening may be reduced or may not be cured.
When ΔEC exceeds 4% IACS, it indicates that the amount of the solid solution element in the material is too large after the low-temperature heat treatment (before strain relief annealing). For this reason, the degree of hardening in low-temperature annealing hardening at the time of strain relief annealing increases excessively, and the 0.2% proof stress of the material after strain relief annealing may decrease due to an increase in solid solution elements that do not contribute to strength. is there. Further, along with the decrease in 0.2% proof stress, the elongation in the direction perpendicular to the rolling increases beyond 3%. As a result, the resistance when the material is punched with a mold increases, and sagging may occur, resulting in a decrease in mold wear resistance.

  The electrical conductivity EC (% IACS) before strain relief annealing is preferably 25% or more and less than 40%. The reason for this is as already described.

<Strain relief annealing>
The strain relief annealing is preferably performed at 200 to 500 ° C. for 5 to 100 seconds. If the temperature of the stress relief annealing is less than the above range, the stress relief annealing becomes insufficient, so that the improvement in strength due to the low-temperature annealing hardening described above becomes small, and the 0.2% proof stress in the rolling parallel direction becomes 950 MPa or more. May be difficult to do. When the temperature of strain relief annealing exceeds the above range, the above-mentioned low temperature annealing hardening due to strain relief annealing becomes excessive and the alloy is softened, and the 0.2% yield strength may not be improved.
When the time for strain relief annealing is less than the above, low temperature annealing hardening is exhibited, but the spring limit value is 850 MPa or less, and the press punchability may be lowered. When the time for strain relief annealing exceeds the above range, low-temperature annealing hardening is developed and the 0.2% proof stress is improved, but the elongation exceeds 3%, and the press punchability may be lowered.

The electrolytic copper was melted in an atmospheric melting furnace, and a predetermined amount of the additive elements shown in Table 2 was added as necessary, and the molten metal was stirred. Thereafter, the molten metal was poured into a mold at a casting temperature of 1200 ° C. to obtain a copper alloy ingot having the composition shown in Table 2. The ingot was hot rolled to a plate thickness of 10 mm. Thereafter, chamfering, cold rolling, solution treatment, aging treatment, low temperature heat treatment, cold rolling after low temperature heat treatment were performed in this order to obtain a sample having a plate thickness of 0.03 to 0.2 mm. Stress relief annealing was performed after cold rolling after low temperature heat treatment.
In addition, hot rolling was performed at 1000 degreeC for 3 hours, and the solution treatment was performed at 800-950 degreeC. The aging treatment was performed at 400 ° C. to 550 ° C. for 1 to 15 hours, the low temperature heat treatment was performed at 550 to 800 ° C., and the stress relief annealing was performed at 200 to 500 ° C. for 5 to 100 seconds. The aging treatment and the strain relief annealing were performed at a temperature and a time at which the 0.2% yield strength after each treatment was maximized.

<Evaluation>
The following items were evaluated for the obtained samples.
[conductivity]
Volume resistivity obtained by a four-terminal method using a double bridge apparatus in accordance with JISH0505 for samples in the rolling parallel direction after aging treatment and low-temperature heat treatment, and samples in the rolling parallel direction of the final product after strain relief annealing. From this, the conductivity (% IACS) was calculated.
[Strength]
For the final product after strain relief annealing, a JIS No. 13B specimen was prepared using a press so that the tensile direction was parallel to the rolling parallel direction and the rolling perpendicular direction. The test piece was subjected to a tensile test according to JIS-Z2241, and 0.2% yield strength YS was measured.
The tensile test conditions were a test piece width of 12.7 mm, room temperature (15 to 35 ° C.), a tensile speed of 5 mm / min, and a gauge length L = 50 mm.

[Elongation]
For the final product after strain relief annealing, a JIS13B test piece is prepared using a press so that the tensile direction is parallel to the rolling parallel direction and the perpendicular direction of rolling, and the above 0.2% yield strength is measured. It was measured at the same time. And the difference of the length L (gauge length) between the gauge points when the test piece broke and the gauge distance L0 before the test was obtained in%.

[Average crystal grain size]
The average crystal grain size was obtained by chemical corrosion after a mirror polishing of a cross section parallel to the rolling direction and a cutting method (JIS-H0501).

[Spring limit value]
For the final product after strain relief annealing, a strip-shaped test piece (test piece width 10 mm) that is long in the direction perpendicular to the rolling direction is held in a cantilevered manner by a moment type test specified in JIS-H3130. The maximum surface stress was measured from the bending moment that produced the specified amount of permanent deflection, and the spring limit value in the direction perpendicular to the rolling direction was determined.
The test conditions are the material plate thickness t (mm), the distance l (mm) from the fixed end of the material to the load point, and the permanent deflection amount δ (mm). When the material plate thickness t is 0.03 to 0.05 mm When l ² = 1300 t, δ = 0.0325, and the material plate thickness t is 0.051 to 0.07 mm, l ² = 2000 t, δ = 0.050, and the material plate thickness t is 0.071 to 0.09 mm. In this case, l ² = 3000 t and δ = 0.075, and when the material plate thickness t is larger than 0.09 mm, l ² = 4000 t and δ = 0.1.

[Mold wear resistance]
A sample of the final product was punched using a turret punch press, and the wear amount of the punch blade after punching 200,000 shots was measured based on the pre-press. The punch used was a cylindrical one, the clearance was 5% of the plate thickness, the press speed was 290 shots / min, and the indentation depth of the punch was set to 50% of the plate thickness. Further, punches and dies having different hardnesses were used, and the punch hardness was set to be 60 to 80% of the die hardness.
As shown in FIG. 2, the wear amount of the punch blade is determined by the area S1 in which the height difference occurs between the cross-sectional profile P1 of the punch blade before pressing and the cross-sectional profile P2 of the punch blade after pressing, as shown in FIG. The area was calculated as the worn area. 2 indicates the pressing direction. The mold wear was evaluated according to the following criteria. If the evaluation is ○, the mold wear resistance is excellent.
○: Wear area is less than 4000 μm ² ×: Wear area is 4000 μm ² or more

[Press punchability]
Displacement of the punch toward the die at a speed of 0.1 mm / min with the final product after strain relief annealing placed between a square punch with a side of 10 mm and a die with 5% clearance. And pressed. The press fracture surface after pressing was observed with an optical microscope, and when the width of the shear surface in the thickness direction was S (mm) and the width of the fracture surface was H (mm), the press punchability was evaluated by S / H. . The shear surface width S and the fracture surface width H were calculated from the photograph of the observation surface using image analysis software, and evaluated by the following indices. If evaluation is (double-circle) and (circle), press punching property is excellent.
A: S / H ≦ 1.0
○: 1.0 <S / H ≦ 1.5
×: S / H> 1.5

  The obtained results are shown in Tables 2 to 4. “0.5Zn” in Tables 2 and 3 means that 0.5% by mass of Zn is contained.

  As shown in Tables 2 to 4, in each Example, YS is 950 MPa or more, EL is 3% or less, conductivity is 25% IACS or more, and the ratio (pressure YS / EL) is 317 to 1300 (MPa). Further, the spring limit value in the direction perpendicular to the rolling was 850 MPa or more. As a result, the mold wear resistance and press punchability were good.

In the case of Comparative Example 1 in which the solution treatment temperature is too higher than the example and the average crystal grain size after the solution treatment exceeds 20 μm, the 0.2% proof stress in the rolling parallel direction is less than 950 MPa, and the spring in the direction perpendicular to the rolling The limit value was less than 850 MPa, and the press punchability was reduced.
In the case of Comparative Example 2 in which the solution treatment temperature was too lower than the example and the average crystal grain size after solution treatment was less than 10 μm, a part of the metal structure became non-recrystallized, and 0. The 2% proof stress was less than 950 MPa, the spring limit value in the direction perpendicular to the rolling was less than 850 MPa, and the press punchability was reduced.

  In the case of Comparative Example 3 in which the cooling rate after the solution treatment was too high compared to the Examples and Comparative Example 4 in which the cooling rate after the solution treatment was too low than the Examples, the 0.2% yield strength in the rolling parallel direction was 950 MPa. The spring limit value in the direction perpendicular to the rolling was less than 850 MPa, and the press punchability was reduced.

In the case of Comparative Example 5 in which the aging temperature is too higher than the Examples, the electrical conductivity before strain relief annealing is less than 25%, the processing rate RE does not satisfy the formula (1), and the 0.2% yield strength in the rolling parallel direction is 950 MPa. The spring limit value in the direction perpendicular to the rolling was less than 850 MPa, and the press punchability was reduced.
In the case of Comparative Example 6 in which the aging temperature was too lower than the examples, the 0.2% yield strength in the rolling parallel direction was less than 950 MPa, the spring limit value in the direction perpendicular to the rolling was less than 850 MPa, and the conductivity was less than 25% IACS, Decreased. Further, the elongation exceeded 3%, and the mold wear resistance and also decreased. This is presumably because low temperature annealing hardening was insufficient due to insufficient aging treatment.

In the case of Comparative Example 7 in which ΔEC is less than 2% IACS, the 0.2% yield strength in the rolling parallel direction is less than 950 MPa, the spring limit value in the direction perpendicular to the rolling is less than 850 MPa, the elongation exceeds 3%, and the mold wear resistance In addition, the press punchability was lowered. The reason why the wear resistance of the mold was lowered is thought to be due to insufficient low-temperature annealing hardening.
In the case of Comparative Example 8 in which ΔEC exceeded 4% IACS, the 0.2% yield strength in the rolling parallel direction was less than 950 MPa, and the spring limit value in the direction perpendicular to the rolling was less than 850 MPa. This is presumably because the strength was not sufficiently improved during strain relief annealing. Further, the elongation exceeded 3%, and the mold wear resistance also decreased.

In the case of Comparative Example 9 in which the electrical conductivity before strain relief annealing exceeds 40%, the 0.2% proof stress in the rolling parallel direction is less than 950 MPa, the spring limit value in the direction perpendicular to the rolling is less than 850 MPa, and the elongation exceeds 3%. In addition, the wear resistance of the mold and the press punchability were lowered. This is presumably because low-temperature annealing hardening did not occur.
In the case of Comparative Example 10 in which the electrical conductivity before strain relief annealing is less than 25% and the processing rate RE does not satisfy the formula (1), the 0.2% proof stress in the rolling parallel direction is less than 950 MPa, and the spring limit value in the direction perpendicular to the rolling direction. Was less than 850 MPa, the conductivity was less than 25% IACS, the elongation exceeded 3%, and the wear resistance of the mold and the press punching property were lowered. This is thought to be due to insufficient low-temperature annealing hardening.

In the case of Comparative Example 11 in which the processing rate RE is less than 70%, the 0.2% proof stress in the rolling parallel direction is less than 950 MPa, the spring limit value in the direction perpendicular to the rolling is less than 850 MPa, the elongation exceeds 3%, and the mold wear resistance And press punchability were reduced. This is presumably because low-temperature annealing hardening did not occur.
In the case of Comparative Example 12 in which the processing rate RE was 90% or more, the sample was cracked during cold rolling, and the final product could not be manufactured.

In the case of Comparative Example 13 in which the heating time for strain relief annealing was too short compared to the examples, the spring limit value was less than 850 MPa, and the press punching property was lowered.
In the case of Comparative Example 14 in which the heating time for strain relief annealing was too long compared to the examples, the elongation exceeded 3%, the (YS / EL) ratio was less than 317, and the mold wear resistance and press punchability were reduced. .

In the case of Comparative Example 15 in which ΔEC exceeds 4% IACS, the electrical conductivity before strain relief annealing is less than 25%, and the processing rate RE does not satisfy the formula (1), the 0.2% proof stress in the rolling parallel direction is less than 950 MPa. The spring limit value in the direction perpendicular to the rolling was less than 850 MPa, the electrical conductivity was less than 25% IACS, the elongation exceeded 3%, and the die wear resistance and press punchability were reduced. This is thought to be due to insufficient low-temperature annealing hardening.
In the case of Comparative Example 16 in which ΔEC is less than 2% IACS and the processing rate RE is less than 70%, the 0.2% yield strength in the rolling parallel direction is less than 950 MPa, the elongation exceeds 3%, and the spring limit value in the direction perpendicular to the rolling direction. Was less than 850 MPa, and the mold wear resistance and press punchability were reduced.

  In the case of Comparative Example 17 where the electrical conductivity before strain relief annealing exceeds 40% and the processing rate RE is less than 70%, the 0.2% proof stress in the rolling parallel direction is less than 950 MPa, the elongation exceeds 3%, and the direction perpendicular to the rolling direction. The spring limit value was less than 850 MPa, and the die wear resistance and the press punching property were deteriorated.

In the case of Comparative Example 18 in which the Ni content exceeded 5.0%, cracking occurred during hot rolling, and the alloy could not be produced.
In the case of Comparative Example 19 in which the Ni content exceeds 5.0% and the Si content exceeds 1.5%, the 0.2% proof stress in the rolling parallel direction exceeded 1300 MPa. Decreased. This is considered to be because the shear surface became hard due to the precipitate having high hardness and the precipitate.

In the case of Comparative Example 20 containing Mg, Mn, Sn, Zn and Cr in a total amount exceeding 1.0%, cracks were generated by hot rolling, and an alloy could not be produced.
In the case of Comparative Example 21 in which the total content of Ni was less than 3.0%, the 0.2% yield strength in the rolling parallel direction was less than 950 MPa, the spring limit value in the direction perpendicular to the rolling was less than 850 MPa, and the press punchability was deteriorated.

Claims (4)

In mass%, Ni: 3.0-5.0%, Si: 0.5-1.5% contained, the balance consists of Cu and inevitable impurities,
0.2% proof stress YS in the rolling parallel direction is 950 to 1300 MPa, elongation EL in the direction perpendicular to the rolling is 3% or less, conductivity is 25% IACS or more,
And (0.2% yield strength YS in the rolling parallel direction) / (elongation EL in the direction perpendicular to the rolling) is 317 to 1300 (MPa /%),
A Cu—Ni—Si based copper alloy having a spring limit value in the direction perpendicular to the rolling of 850 MPa or more.   The Cu-Ni-Si based copper alloy according to claim 1, wherein the spring limit value is 900 MPa or more.   Furthermore, the Cu-Ni-Si type copper alloy of Claim 1 or 2 which contains 0.005-1.0 mass% of at least 1 sort (s) chosen from the group of Mg, Mn, Sn, Zn, and Cr in a total amount.   Furthermore, 0.005-1.0 mass% of at least 1 sort (s) chosen from the group of P, B, Ti, Zr, Al, Fe, and Ag is contained in a total amount as described in any one of Claims 1-3. Cu-Ni-Si based copper alloy.