JP6355672B2 - Cu-Ni-Si based copper alloy and method for producing the same - Google Patents

Description

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

  Conventionally, brass and phosphor bronze, which are solid solution strengthened alloys, have been used as materials for terminals and connectors. By the way, with the improvement in performance of electronic equipment, the copper alloy used is required to have a high current. Thus, precipitation-strengthened copper alloys that are superior in strength, electrical conductivity, and thermal conductivity have been used compared to conventional solid solution-strengthened copper alloys. Precipitation-strengthened copper alloys are obtained by aging the solution-treated supersaturated solid solution to disperse fine precipitates uniformly, increasing the strength of the alloy and reducing the amount of solid solution elements in copper. As a result, electrical conductivity is improved. For this reason, it is excellent in mechanical properties such as strength and springiness, and also has good electrical and thermal conductivity.

A Cu-Ni-Si based copper alloy has been developed as a precipitation strengthening type copper alloy (Patent Document 1). However, in general, the Cu—Ni—Si based copper alloy has a problem that the shear surface of the press punched surface is large and the amount of wear of the mold increases, and suppression of mold wear is desired.
Therefore, a Cu—Ni—Sn—P-based copper alloy in which precipitates having a particle size of 20 to 150 nm are dispersed has been proposed (Patent Document 2). According to this copper alloy, the precipitate functions as a generation source of cracks at the time of punching, and the wear of the press die is reduced in order to prevent an increase in sagging and burrs.
Similarly, a Cu—Co—Si based copper alloy in which precipitates are dispersed has also been developed (Patent Document 3).

International Publication No. WO 2011/068134 (Table 1) JP 2007-100111 A JP 2012-224922 A

However, when trying to reduce mold wear by precipitates of precipitation-strengthened copper alloy, the high hardness precipitates and the shear surface with high hardness due to the precipitates come into contact with the mold, and wear is reduced. May promote.
The present invention has been made 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, conductivity, and mold wear.

  The present inventor has found that when the elongation of the Cu—Ni—Si based copper alloy is low, sagging of the contact portion between the mold and the copper alloy material is suppressed, and the mold wear is improved. Further, if the copper alloy is easily softened by heat, the shear surface which is a contact surface with the press is softened due to heat generation during pressing, and this also improves the mold wear resistance.

Further, as an example of a method for imparting such characteristics, 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. This low-temperature annealing hardening increases the strength of the material and reduces the elongation. In addition, a material that has been subjected to low-temperature annealing hardening by strain relief annealing will soften as will be described later when heat is applied thereafter.
In the low-temperature annealing hardening, the degree of hardening varies depending on the degree of cold rolling after aging just before strain relief annealing and the degree of precipitation of solid solution elements during the cold rolling. For this reason, the softening characteristics of the product and the degree of processing and the degree of precipitation at the time of manufacture, which are indicators of mold wear, were defined.

  In order to achieve the above object, the Cu—Ni—Si based copper alloy of the present invention is, in mass%, at least one selected from the group of Ni and Co in a total amount of 3.0 to 4.5%, Si: 0.6 to Containing 1.0%, the balance consisting of Cu and inevitable impurities, tensile strength TS in the rolling parallel direction is 1000MPa or more, elongation in the direction is 2% or less, and the above-mentioned tensile force by atmospheric heating at 500 ° C for 60 seconds The amount of decrease TS1 in strength TS has an annealing softening property of 30 to 140 MPa.

The Cu—Ni—Si based copper alloy of the present invention preferably further contains at least one selected from the group of Mg, Mn, Sn, Zn and Cr in a total amount of 0.005 to 1.0 mass%.
The Cu—Ni—Si based copper alloy of the present invention preferably 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%.

  The method for producing a Cu—Ni—Si based copper alloy according to the present invention is a method for producing the Cu—Ni—Si based copper alloy, wherein the total amount of at least one selected from the group of Ni and Co by mass%. 3.0 to 4.5%, Si: 0.6 to 1.0%, and if necessary, at least one selected from the group of Mg, Mn, Sn, Zn and Cr in a total amount of 0.005 to 1.0% by mass, and / Or hot rolling an ingot containing at least one selected from the group consisting of P, B, Ti, Zr, Al, Fe and Ag in a total amount of 0.005 to 1.0 mass%, the balance being Cu and inevitable impurities, Perform cold rolling, solution treatment, aging treatment, low temperature solution treatment, cold rolling after aging, strain relief annealing in this order, and processing rate RE of the cold rolling after aging is 50% or more, after the aging treatment In comparison, after the low temperature solution treatment, the low temperature solution treatment is set so that the conductivity is lowered by 2 to 4% IACS, and the strain relief annealing is performed at 200 to 500 ° C. for 1 to 1000 seconds.

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

It is a figure explaining the wear area of the punch for quantifying die wear.

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

(composition)
[Ni, Co and Si]
The total amount of at least one selected from the group of Ni and Co in the copper alloy is 3.0 to 4.5%, Si: 0.6 to 1.0%, and Si: 0.6 to 1.0%. Ni, Co, and Si form an intermetallic compound by performing an appropriate heat treatment, and improve strength without deteriorating conductivity.
If the content of Ni, Co and Si is less than the above range, the effect of improving the strength cannot be obtained, and if it exceeds the above range, the conductivity is lowered and the hot workability is also lowered.

[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. Cr forms a compound with Si in the same manner as Ni, and therefore improves the strength without deteriorating the conductivity by precipitation hardening.
Further, the alloy may further contain 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% by mass. 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.

[Strength]
The tensile strength TS in the rolling parallel direction of the Cu-Ni-Si copper alloy is 1000 MPa or more. Since a large amount of solid solution element is required to develop the above-described low-temperature annealing hardening, the contents of Ni (Co) and Si are increased in the present invention. As a result, the tensile strength TS in the rolling parallel direction becomes higher than 1000 MPa.
TS is obtained by a tensile test according to JIS-Z2241.

[Elongation]
The elongation in the rolling parallel direction of the Cu-Ni-Si copper alloy is 2% or less. When the elongation is reduced to 2% or less, resistance is reduced when the copper alloy material is punched with a mold, so that sagging of the contact portion between the mold and the copper alloy material is suppressed, and mold wear resistance is improved.
The lower limit of elongation is not particularly limited, but is, for example, 1%.
Elongation is the elongation at break, and was measured simultaneously with the above-described TS according to JIS-Z2241 using a tensile tester. Then, the difference between 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%.
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, a gauge length L = 50 mm, and a tensile test in the rolling direction of the copper foil.

[Softening properties]
As a softening characteristic of the Cu—Ni—Si based copper alloy of the present invention, the decrease amount ΔTS1 of the tensile strength TS due to atmospheric heating at 500 ° C. for 60 seconds is 30 to 140 MPa. The copper alloy once subjected to low-temperature annealing hardening is easily softened when heat is applied thereafter, and the shearing surface that is the contact surface with the die after punching is softened due to heat generated during pressing, Mold wear resistance is improved. Therefore, ΔTS1 is used as an index as the degree of softening due to the application of heat after low-temperature annealing hardening.
As described above, the low-temperature annealing hardening increases the strength of the material and decreases the elongation, thereby suppressing die wear (particularly during press-release). Further, as described above, the material subjected to the low-temperature annealing hardening tends to soften the sheared surface due to heat generated during pressing, and this also suppresses mold wear (particularly after pressing). And the grade of the low temperature annealing hardening which can suppress metal mold | die wear effectively is implement | achieved by managing a softening characteristic in the above-mentioned range.
ΔTS1 = (TS before heating at 500 ° C. × 60 seconds) − = (TS after heating at 500 ° C. × 60 seconds) −

Therefore, when ΔTS1 is less than 30 MPa, it indicates that the amount of the solid solution element in the material before the strain relief annealing (before the low temperature annealing hardening occurs) 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 reduced, and the degree of curing in the low temperature annealing hardening is reduced or is not cured. That is, ΔTS1, which is the degree of softening due to heating after strain relief annealing, decreases. Therefore, since the degree of softening of the shear surface due to heat generation during pressing is small, it is difficult to suppress mold wear.
When ΔTS1 exceeds 140 MPa, it indicates that the amount of solid solution elements in the material before strain relief annealing (before low-temperature annealing hardening) is too large. When there is a large amount of solid solution elements during strain relief annealing, the amount of solid solution elements that adhere to dislocations increases as described above, and because it is hardened too much by low-temperature annealing hardening, softening by heating after strain relief annealing , That is, ΔTS1 increases. In addition, the increase in the amount of solid solution elements that do not contribute to the strength decreases the tensile strength of the material, and accordingly, the elongation increases beyond 2%. As a result, resistance when the material is punched with a mold increases, sagging occurs and the mold wear resistance is poor.
On the other hand, if ΔTS1 exceeds 140 MPa, the tensile strength of the material decreases and the elongation increases, so that it becomes difficult to ensure the desired tensile strength and elongation, and the mechanical properties are inferior.

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

<Cold rolling after aging>
Here, the processing rate RE of cold rolling after aging is set to 50% or more. In order to improve the strength of the Cu—Ni—Si based copper alloy in the rolling parallel direction, it is important to improve the strength by strain relief annealing, which is the final annealing. For this purpose, it is necessary to increase the working rate of post-aging cold rolling immediately before strain relief annealing and increase the amount of solid solution elements (Ni (Co) and Si) immediately before strain relief annealing. This is because when a rolling strain is introduced into the structure by cold rolling after aging, a mechanism (low temperature annealing hardening) in which solid solution elements are fixed to this strain and strengthened as dislocation obstacles by subsequent strain relief annealing. This is to cause it to occur.
Accordingly, when the processing rate RE is less than 50%, the low-temperature annealing hardening is insufficient.
The processing rate RE is the rate (%) of the change in the thickness of the alloy before and after cold rolling after aging.

<Low temperature solution treatment>
Moreover, in order to increase the amount of solid solution elements immediately before the strain relief annealing, a low temperature solution treatment is performed. The low temperature solution treatment is performed at a temperature lower than the initial solution temperature and not less than the aging temperature. In the low-temperature solution 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 conductivity after the aging treatment (that is, before the low temperature solution treatment) and after the low temperature solution treatment is used. ΔEC = (conductivity after aging treatment) − (conductivity after low-temperature solution treatment). The low temperature solution treatment is performed at 550 to 800 ° C. for 1 to 250 seconds so that ΔEC = 2 to 4% (IAC).
If the amount of the solid solution element is increased by the low-temperature solution treatment just before the strain relief annealing as compared with that after the aging treatment, the conductivity is lowered.

When ΔEC is less than 2% IACS, the amount of solid solution elements in the material after low-temperature solution treatment (before strain relief annealing) is small, and low-temperature annealing hardening is insufficient.
On the other hand, when ΔEC exceeds 4% IACS, it indicates that the amount of solid solution elements in the material is too large after the low-temperature solution treatment (before strain relief annealing), as in the case where ΔTS1 exceeds 140 MPa. For this reason, for the same reason as when ΔTS1 exceeds 140 MPa, the degree of hardening in low-temperature annealing hardening during strain relief annealing increases too much, and the tensile strength of the material after strain relief annealing decreases, Along with this, the growth increases. As a result, the mold wear and the mechanical properties of the product are inferior as described above.

<Strain relief annealing>
Thereafter, strain relief annealing is performed at 200 to 500 ° C. for 1 to 1000 seconds. If the temperature or annealing time of the stress relief annealing is less than the above range, the stress relief annealing becomes insufficient, the strength is improved by the low temperature annealing hardening described above, and the softening due to heating after the stress relief annealing becomes insufficient, and the shear plane Since the degree of softening is small, it is difficult to suppress mold wear.
If the temperature or annealing time of strain relief annealing exceeds the above range, the above-described low temperature annealing hardening due to strain relief annealing becomes excessive and the alloy is softened, and the strength cannot be improved.

As an index for optimizing the above-mentioned degree of low-temperature annealing hardening by strain relief annealing, it is preferable to manage the low-temperature annealing hardening amount ΔTS2 to 20 to 50 MPa. ΔTS2 = (TS after strain relief annealing) − (TS before strain relief annealing)
When ΔTS2 is less than 20 MPa, the above-described ΔTS1 is less than 30 MPa, and as described above, the stress relief annealing is insufficient.
When ΔTS2 exceeds 50 MPa, the above-described ΔTS1 exceeds 140 MPa, and the mold wear and mechanical properties are inferior as described above.

Further, the elongation of the material is lowered by the low-temperature annealing hardening. Elongation reduction amount ΔEl2 (%) = (El after stress relief annealing) − (El before stress relief annealing)
As an index for optimizing the above-described low-temperature annealing hardening degree by strain relief annealing, it is preferable to manage ΔEl2 to be −0.3 to −1.4%.

Electrolytic copper was melted in an air melting furnace, and a predetermined amount of additive elements shown in Table 1 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 1. The ingot was subjected to hot rolling, chamfering, first cold rolling, solution treatment, aging treatment, low temperature solution treatment, and cold rolling after aging in this order to obtain a sample having a thickness of 0.2 mm. After cold rolling after aging, strain relief annealing was performed under the conditions shown in Table 1.
In addition, hot rolling was performed at 1000 degreeC for 3 hours, and the solution treatment was performed at 800-1000 degreeC. The aging treatment was performed at 400 ° C. to 550 ° C. for 1 to 15 hours at a temperature and a time at which the tensile strength after aging was maximized.
The low temperature solution treatment was performed at 650 ° C.

<Evaluation>
The following items were evaluated for the obtained samples.
[conductivity]
The samples in the rolling parallel direction after the aging treatment and the low-temperature solution treatment, and the samples in the rolling parallel direction of the final product after the strain relief annealing were obtained by a four-terminal method using a double bridge apparatus in accordance with JISH0505. The conductivity (% IACS) was calculated from the volume resistivity.
[Strength]
About the final product after strain relief annealing, the JIS13B test piece was produced using the press so that the tension direction might become parallel to the rolling direction. The test piece was subjected to a tensile test according to JIS-Z2241, and the tensile strength TS was measured.
In addition, TS was measured in the same manner after subjecting the final product to atmospheric heating at 500 ° C. for 60 seconds.
[Elongation]
The elongation at break was determined by the tensile test. The difference between the length L between the gauge points when the test piece broke and the gauge distance L0 before the test was determined in% to obtain the elongation.

[Mold wearability]
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. A cylindrical punch was used, the clearance was 5% of the plate thickness, the press speed was 290 shots / min, and the punch indentation depth was set to 50% of the plate thickness. In addition, punches and dies having different hardnesses were used, and the punch hardness was set to 60 to 80% of the die hardness.
As shown in FIG. 1, the wear amount of the punch blade is an area S1 in which a height difference is generated 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. A symbol D in FIG. 1 indicates a pressing direction. The mold wear was evaluated according to the following criteria. If evaluation is (circle), metal mold | die abrasion property is excellent.
○: Wear area is less than 4000 μm ² ×: Wear area is 4000 μm ² or more

  The obtained results are shown in Table 1. “0.5Zn” in Table 1 means that 0.5% by mass of Zn is contained.

  As is apparent from Table 1, in each of the examples in which the tensile strength TS in the rolling parallel direction was 1000 MPa or more, the elongation was 2% or less, and ΔTS1 was 30 to 140 MPa, the mold wear was excellent.

On the other hand, in Comparative Example 1 in which ΔEC was less than 2% IACS and ΔTS2 was less than 20 MPa, ΔTS1 was less than 30 MPa, and the product TS was less than 1000 MPa, and the elongation exceeded 2%. This is thought to be due to insufficient low-temperature annealing hardening.
In the case of Comparative Example 2 in which ΔEC exceeded 4% IACS and ΔTS2 exceeded 50 MPa, ΔTS1 exceeded 140 MPa, the product TS was less than 1000 MPa, and the elongation exceeded 2%. The mold wear was inferior.

  In the case of Comparative Example 3 in which the reduction rate RE of cold rolling after aging is less than 50%, ΔTS1 was less than 30 MPa, the product TS was less than 1000 MPa, and the elongation exceeded 2%. . This is thought to be due to insufficient low-temperature annealing hardening.

  In Comparative Example 4 in which ΔEC was less than 2% IACS and ΔTS2 was less than 20 MPa, ΔTS1 was less than 30 MPa as in Comparative Example 1, and the mold wear was inferior. However, in the case of Comparative Example 4, since the processing rate RE of the cold rolling after aging was significantly higher than that of Comparative Example 1, the product TS was 1000 MPa or more and the elongation was 2% or less.

In the case of Comparative Example 5 in which the total content of Ni and Co is less than 3.0%, since the amount of solid solution is small, the low-temperature annealing hardening is insufficient in the first place, and the strength and mold wear resistance are inferior.
In Comparative Examples 6 and 8 in which the total content of Ni and Co exceeded 4.5%, cracking occurred during hot rolling, and the alloy could not be produced.

  In the case of Comparative Example 7 containing Mg, Mn, Sn, Zn, Co and Cr in a total amount exceeding 1.0%, cracks were generated by hot rolling, and an alloy could not be produced.

  In Comparative Examples 1, 3, 4, and 5 in which the low temperature annealing hardening amount ΔTS2 by strain relief annealing was less than 20 MPa, ΔTS1 was less than 30 MPa. In Comparative Example 2 where ΔTS2 exceeded 50 MPa, ΔTS1 exceeded 140 MPa.

Claims (4)

In a mass%, it contains at least one or more selected from the group of Ni and Co in a total amount of 3.0 to 4.5%, Si: 0.6 to 1.0%, the balance consisting of Cu and inevitable impurities,
The tensile strength TS in the rolling parallel direction is 1000 MPa or more, and the elongation in the direction is 2% or less,
And the Cu-Ni-Si type copper alloy which has the annealing softening characteristic of the fall amount (DELTA) TS1 of the said tensile strength TS by 30 to 140 MPa by the atmospheric heating of 500 degreeC x 60 second.   The Cu-Ni-Si based copper alloy according to claim 1, further comprising 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 according to claim 1 or 2, further comprising 0.005 to 1.0 mass% in total of at least one selected from the group consisting of P, B, Ti, Zr, Al, Fe and Ag. It is a manufacturing method of the Cu-Ni-Si system copper alloy according to any one of claims 1 to 3,
Contains at least one or more selected from the group of Ni and Co by mass% in a total amount of 3.0 to 4.5%, Si: 0.6 to 1.0%, and if necessary, from the group of Mg, Mn, Sn, Zn and Cr Contains at least one selected from 0.005 to 1.0% by mass in total and / or at least one selected from the group of P, B, Ti, Zr, Al, Fe and Ag in total from 0.005 to 1.0% by mass Containing, the remainder of the ingot made of Cu and inevitable impurities, in the order of hot rolling, cold rolling, solution treatment, aging treatment, low temperature solution treatment, cold rolling after aging, strain relief annealing,
The processing rate RE of the cold rolling after aging is 50% or more,
Set the low temperature solution treatment so that the conductivity is 2-4% IACS lower after the low temperature solution treatment than after the aging treatment,
A method for producing a Cu—Ni—Si based copper alloy, wherein the strain relief annealing is performed at 200 to 500 ° C. for 1 to 1000 seconds.