JP5002768B2 - Highly conductive copper-based alloy with excellent bending workability and manufacturing method thereof - Google Patents

Description

  The present invention relates to a highly conductive copper-based alloy having excellent bending workability and a method for producing the same, and more particularly to a consumer product, for example, an information / communication narrow-pitch connector original plate, an automotive harness connector original plate, and a semiconductor lead. The present invention relates to a highly conductive copper base alloy excellent in bending workability suitable for constituting a frame original plate, a small switch, a relay original plate, and the like, and a method of manufacturing the same.

  With the recent development of mobile terminals and mobile devices, connectors mounted on personal computers, mobile phones, digital video, etc. have pin thicknesses and pin widths in the range of 0.10 to 30 mm. There is a tendency to become narrower and thinner due to downsizing. In this case, as a result of an increase in the amount of information input to and output from the pin terminals and an increase in speed, the Joule heat generated from the energized current increases the contact temperature and exceeds the allowable temperature of the insulator housing the contact. Sometimes it ends up. In addition, since a part of the pin terminal may be used for a power source, the material needs to have a reduced conductor resistance, that is, a high conductivity. Furthermore, it is indispensable to have both strength, springiness and bendability so that stable shape accuracy can be reproduced during high-speed press forming of pin terminals.

  On the other hand, connectors mounted on automobile electrical components are required to be lighter and space-saving by reducing the size of the connector in order to cope with the increase in the number of circuits and mounting density accompanying the increase in electronic control systems. The female terminal width has been downsized from 2.3 mm, which was 10 years ago, to 0.64 mm. Therefore, it goes without saying that high electrical conductivity is required as in the portable terminal. In addition, in order to maintain good connection characteristics after being molded into a box-type terminal, the plate thickness is not much different from the conventional one, but is about 0.25 mm, while strict shape accuracy is required. A state where the inner bending radius R of the portion is close to 0 or a state close to close contact bending is forced, and more severe processing is required compared to the conventional case.

  Conventionally, phosphor bronze or beryllium copper has been used as a material corresponding to these applications. However, for phosphor bronze, for example, in CDA 52100, the conductivity is decisively low at about 12% IACS. As for beryllium copper, although it satisfies the required performance, there are many problems in terms of inclusion of Be, lack of material supply, and price, and the development of a copper-based alloy to replace beryllium copper is eagerly desired.

A Cu—Ni—Si based copper-based alloy is known as the most promising alternative to beryllium copper. For example, Cu-Ni-Si-based copper-based alloys were added with 0.05 to 0.3 mass% Mg (Patent Documents 1 to 4), and Cu-Ni-Si-based copper-based alloys were added with Sn and Zn. Copper-based alloys (Patent Documents 5 to 6) and Cu-Ni-Si based copper-based alloys with Sn, Zn, Mg, etc. added to them (Patent Document 7), etc. have been developed, with high tensile strength and high heat resistance It is used for connectors, lead frames, and other applications as a copper-based alloy that combines high performance, high stress relaxation properties and relatively high electrical conductivity.
JP-A-61-250134 Japanese Patent Laid-Open No. 8-325681 Japanese Patent Laid-Open No. 11-217639 JP 2001-49369 A JP-A-5-279825 JP 2000-80428 A JP 2002-38228 A

  Recent copper-based alloys are used in increasingly severe environments. Even with the Cu-Ni-Si-based copper-based alloys described in the above-mentioned patent documents, while having various characteristics, further higher conductivity, higher strength and good bending work It is indispensable to balance with sex. Even in the alloys described in Patent Documents 1 to 7, when the electrical conductivity is 45% IACS or higher, the tensile strength and the bending workability are not sufficient, and on the other hand, when the tensile strength and the bending workability are good, the electrical conductivity is higher than that of 45% IACS. Therefore, it has been difficult to simultaneously achieve the required level of electrical conductivity of 45% IACS or higher, high tensile strength, and excellent bending workability.

  In addition, Cu—Ni—Si-based copper-based alloys have a problem in that various characteristic defects occur between the parallel direction and the perpendicular direction with respect to the rolling direction.

  Therefore, the present invention has a well-balanced characteristic having a conductivity of 45% IACS or more while satisfying both the high tensile strength and excellent bending workability of the Cu-Ni-Si-based copper-base alloy, and also in the rolling direction. Thus, an object of the present invention is to obtain a copper-based alloy having a small difference in characteristics between the parallel direction and the vertical direction.

According to the present invention made to achieve the above-mentioned problems,
Ni: 1.0 to 3.5 mass% (refers to mass%),
Si: 0.2-0.8 mass%,
B: 0.002 to 0.03 mass%,
The remainder (sometimes referred to as “Rem”): a copper-based alloy composed of Cu and inevitable impurities,
Tensile strength is 650 N / mm ² or more,
Conductivity is 45% IACS or higher,
The average crystal grain size a in the direction parallel to the rolling direction on the plate surface and the average crystal grain size b in the direction perpendicular to the rolling direction are both 10 μm or less and the ratio a / b is 0.5 to 2.0. A copper-based alloy is provided.

This copper-based alloy preferably has a ratio 100 × (Ecb) / (Eca) of 120% or less of the electrical conductivity after solutionization (Ecb) and the electrical conductivity (Eca) when the additive element is completely dissolved, The average crystal grain size D _AV after the solution treatment is more than 2 and not more than 20 μm.

  This copper-based alloy is composed of Ca: 0.0001 to 0.005 mass%, C: 0.0001 to 0.005 mass%, P: 0.01 to 0.3 mass%, and Fe: 0.01 to 0.3 mass%. 1 type or 2 types or more can be further contained in total 0.5 mass% or less. In some cases, Co: 0.05 to 0.5 mass%, Ag: 0.002 to 0.2 mass%, Sn: 0.02 to 2.0 mass%, Zn: 0.02 to 2.0 mass%, 1 It is possible to further contain 2.0 mass% or less in total of two or more species. And this copper-based alloy plate is good that S content is 15 ppm or less, and oxygen content is 30 ppm or less.

The copper-based alloy, conductivity is 45% IACS or more preferably an least 48% IACS, the tensile strength is 650 N / mm ² or more, preferably 700 N / mm ² or more and more preferably and having a 720N / mm ² or more The ratio of the tensile strength in the direction parallel to and perpendicular to the rolling direction is 95 to 105%, and the bending workability (maximum bending radius) is 0 to 1.0 (MBR / t), preferably 0 to 0.5 (MBR). / T) and the ratio of the maximum bending radius in the direction parallel to and perpendicular to the rolling direction is 95 to 105%.

In order to produce this copper-based alloy sheet, an intermediate product comprising a hot-rolled sheet or a cold-rolled sheet having the alloy composition is subjected to a solution treatment at a recrystallization temperature or higher, followed by an aging treatment, and a conductivity after solution ( Ecb) is 100% (Ecb) / (Eca) as a percentage of the electrical conductivity (Eca) when the additive element is completely dissolved, and the average grain size D _AV after solution treatment exceeds 2 By the above-mentioned solution treatment under a condition of ˜20 μm or less, and after the solution treatment and before or after the aging treatment, a finish cold rolling with a total rolling reduction of 60% or less is performed. It can be advantageously manufactured.

The present invention, high conductivity of 45% IACS or more (even 48% IACS or more), 650 N / mm ² or more (even 700 N / mm ² or higher) combines a well-balanced tensile strength and good bending workability, Furthermore, it is possible to provide a copper-based alloy having a uniform characteristic in which the characteristic difference between the direction parallel to the rolling direction and the direction perpendicular to the rolling direction is small with respect to characteristics such as average crystal grain size, tensile strength, and bending workability.

The present inventors have found that the above-mentioned problems can be achieved by appropriate balance of alloy components and regulation of manufacturing conditions. That is, first, in order to improve the bending workability of this material, both the average crystal grain size a in the direction parallel to the rolling direction on the plate surface and the average crystal grain size b in the direction perpendicular to the rolling direction on the plate surface are both used. It was found that it is effective to control the ratio a / b within the range of 10 μm or less and 0.5 to 2.0. In addition, the total reduction ratio from the heat treatment in the recrystallization temperature range such as solution treatment to the final product should be 60% or less, and the conductivity after solution treatment is the conductivity when the additive element is completely dissolved. The heat treatment temperature and the heat treatment time are controlled so that the average crystal grain size D _AV after the solution treatment is more than 2 μm and less than 20 μm, and the additive element is sufficiently solidified during the solution treatment. In order to dissolve and keep the crystal grain size fine, it becomes clear that B is effective as an element that is precipitated at the solution treatment temperature and does not become coarse. 45% IACS or more and a tensile strength of 650 N / mm ² or more can be stably compatible, better bending has workability, copper-based alloy is less characteristic difference in a direction parallel and perpendicular to the rolling direction Can get Kill.

  An outline of the alloy components in the copper-based alloy of the present invention and the reasons for regulating their contents is as follows.

Ni and Si: Ni and Si are subjected to an aging treatment under appropriate conditions to form Ni ₂ Si precipitates. This precipitate can not only greatly increase the strength of the material, but also the presence of these elements in the deposited state can maintain the thermal conductivity of the master alloy (Cu) at a high level. When the amounts of Ni and Si are too large, the coarsening of precipitates at grain boundaries is likely to occur, which adversely affects workability such as bending workability. If the Ni content is less than 1.0 mass% and the Si content is less than 0.2 mass%, the required strength cannot be obtained, while the Ni content exceeds 3.5 mass% and the Si content exceeds 0.8 mass%. In this case, workability deteriorates. Therefore, the Ni content is 1.0 to 3.5 mass%, preferably 1.5 to 2.5 mass%, and the Si content is 0.2 to 0.8 mass%, preferably 0.3 to 0.6 mass%. %.

  B: B has the property that the precipitation state is maintained even at the solution temperature in this alloy. For this reason, coarsening of the crystal grain size can be prevented, and the solid solution of other additive elements can be made compatible with the refinement of the crystal grain size. In addition, since the crystal grains at the time of casting can be made fine, it is effective in preventing casting cracks and segregation of solid solution elements. When B is added in an amount of 0.002 mass% or more, the effect of preventing the coarsening of crystal grains during solution treatment is exhibited. However, even if added more than 0.03 mass%, an effect commensurate with the amount added cannot be obtained. For this reason, B is set to 0.002 to 0.03 mass%, preferably 0.004 to 0.01 mass%.

  Ca and C: Ca and C also have a crystal grain refining effect, and by adding them in combination with B, crystal grain control becomes easier and more effective. Ca also has a deoxidizing effect during casting. The amount of Ca and C necessary for crystal grain refinement is 0.0001 mass% or more, but the effect is saturated even if the amount exceeds 0.005 mass%.

  Fe and P: Fe and P are elements that are likely to be mixed as impurities, but if they are contained, the material strength can be improved by solid solution strengthening. If the Fe and P contents are both less than 0.01 mass%, sufficient solid solution strengthening cannot be obtained, and if more than 0.3 mass%, the electrical conductivity of the alloy is significantly lowered. Therefore, the ranges of Fe and P are both 0.01 to 0.3 mass%, preferably 0.03 to 0.2 mass%.

  Co and Ag: Co substitutes Ni to produce an intermetallic compound with Si, and has the effect of improving the strength of the material. Ag has the effect of stabilizing the solution treatment and the aging treatment. In order to obtain such an effect, it is desirable that Co is 0.05 to 0.5 mass%, and Ag is 0.002 to 0.2 mass%.

  In addition to being able to improve the strength and response relaxation characteristics by adding Sn: Sn, it is possible to use Sn plating scrap, which is advantageous in terms of cost. If the Sn content is less than 0.02 mass%, the effect of improving the characteristics cannot be sufficiently obtained. If the Sn content is more than 2.0 mass%, the electrical conductivity and the bending workability decrease greatly, so the Sn content is 0.02. It is good to set it to -2.0mass%, Furthermore, it is good to be 0.05-0.3mass%.

  Zn: Zn has the effect of improving the solder heat resistance and migration resistance, but if it is less than 0.02 mass%, the effect is not sufficient. On the other hand, when the amount is more than 2.0 mass%, the solderability and the decrease in conductivity become large. Therefore, the Zn content is preferably 0.02 to 2.0 mass%, and is preferably in the range of 0.05 to 0.3 mass%.

  S content and oxygen content: Increasing the S content tends to cause grain boundary cracking during hot rolling or solution treatment. Further, when the oxygen content is increased, the plating adhesion and solder bonding properties are deteriorated, and oxides such as Si are generated. Therefore, the S content is preferably 15 ppm or less, and the oxygen content is preferably 30 ppm or less.

  In producing the copper-based alloy sheet of the present invention having such a component composition, a slab obtained by casting a molten metal adjusted to such a component composition by semi-continuous casting or continuous casting is hot-rolled or cold-rolled. After rolling, solution treatment is performed at a temperature above the recrystallization temperature, followed by aging treatment. After aging treatment, finish rolling to the desired thickness, and if necessary, perform strain relief and annealing.

The solution treatment is a heat treatment whose main purpose is to bring precipitate-generating elements such as Ni and Si into a solid solution state, but is performed at a temperature higher than the recrystallization temperature. Here, the recrystallization is performed because the crystal grains are not substantially controlled in the subsequent steps, so that the crystal grain state of the final plate is controlled as much as possible during the solution treatment. That is, in this solution treatment, solid solution of the precipitate-generating element and crystal grain control are performed simultaneously. The former solid solution state can be evaluated by measuring conductivity. In the present invention, the solution ratio is such that the 100% (Ecb) / (Eca) ratio of the conductivity (Ecb) after solution treatment and the conductivity (Eca) when the additive element is completely dissolved is 120% or less. The temperature and time are controlled so that recrystallization is performed so that the average crystal grain size D _{AV of} the final product plate is 2 μm to 20 μm.

  Here, the electrical conductivity (Eca) when the additive element is completely dissolved means that the electrical conductivity no longer changes even when the solution temperature of the alloy is raised. To illustrate this, FIG. 1 is shown. FIG. 1 shows an alloy of Ni = 2.0 mass%, Si = 0.4 mass%, and remaining Cu (shown by ▲) and an alloy of Ni = 3.0 mass%, Si = 0.6 mass%, remaining Cu (■ The measurement result of the conductivity of the material obtained by changing the heat treatment temperature every 50 ° C. from 550 ° C. to 900 ° C. is shown as an example. The holding time at each heat treatment temperature is 5 minutes. According to FIG. 1, the curves of both samples substantially overlap each other between 550 ° C. and 750 ° C., but the conductivity of both samples decreases as the heat treatment temperature (solution treatment temperature) increases (precipitation element concentration). It can be seen that, when the conductivity decreases to a certain value for each alloy, the conductivity shows a constant value and no longer changes even if the temperature rises. In this specification, this constant conductivity is referred to as “conductivity when the additive element is completely dissolved (Eca)”. Further, the electric conductivity (Ecb) after solution treatment refers to the electric conductivity of a sample collected from a material immediately after solution treatment.

  After solution treatment and recrystallization treatment, aging treatment, finish rolling, and strain relief annealing as necessary are performed. In the aging treatment, high strength can be expressed by generating uniform and fine precipitates. At that time, by precipitating the intermetallic compound from the state where Ni and Si are in solid solution without excess and deficiency, and by coexisting with B coexistence, it is fine and uniform while suppressing the coarsening of the precipitate at the grain boundary. Such precipitates can be produced. The aging treatment temperature is 400 to 550 ° C., preferably 420 to 470 ° C., and the treatment time is 30 to 1200 minutes, preferably 120 to 420 minutes.

  Finish rolling and strain relief annealing must be performed under conditions such that the state of the crystal grains of the final product is within the range defined by the present invention. That is, the average crystal grain size a in the direction parallel to the rolling direction on the plate surface and the average crystal grain size b in the direction perpendicular to each other are both 10 μm or less and the ratio a / b is 0.5 to 2.0. It is important to obtain a product board. For this purpose, the finish rolling rate should be 60% or less, and if the strain relief annealing is performed, it should be light for the purpose of strain removal. Finish rolling and strain relief annealing to the desired thickness can be repeated several times, but in this case as well, the total rolling reduction needs to be 60% or less. Finish rolling can be performed before and / or after the aging treatment, but if the finish rolling is performed after the aging treatment, the rolling reduction should be 30% or less, and the strain relief annealing should be omitted or annealed at a low temperature. It is desirable to do it.

In this way, in the B-added Cu-Ni-Si-based copper-based alloy, the conductivity (Ecb) after solution treatment in the solution solution / recrystallization process is the conductivity (Eca) when the added element is completely dissolved. 100 × (Ecb) / (Eca) is controlled to be 120% or less, and the condition that the average crystal grain size D _AV after the solution treatment is 2 to 20 μm or less is adopted. By regulating the conditions of aging treatment and finish rolling / strain relief annealing, the electrical conductivity is 45% IACS or more, the tensile strength is 650 N / mm ² or more, and the direction parallel to the rolling direction on the plate surface A highly conductive copper-based alloy plate excellent in bending workability in which the average crystal grain size b in the direction perpendicular to the average crystal grain size a is 10 μm or less and the ratio a / b is 0.5 to 2.0. Obtainable.

  A copper-base alloy having the composition shown in Table 1 was melted using a high-frequency melting furnace, and an ingot having a thickness of 20 mm was obtained in the atmosphere and covered with charcoal. The ingot was heated and held at 910 ° C. for 2 hours, then hot-rolled to a thickness of 3 mm, and water-cooled from 700 ° C. Next, the surface was chamfered to a thickness of 2 mm, and then cold-rolled to 0.5 mm.

Each of the obtained cold-rolled sheets was subjected to a solution treatment for less than 10 minutes at a certain temperature (temperature shown in Table 1) within a range of 650 to 900 ° C., which varies depending on the composition. Then, cold rolling → aging treatment (4 hours at a temperature of 450 to 500 ° C. shown in Table 2) → finish rolling → distortion annealing (both 350 ° C.) was performed. The cold rolling after the solution treatment was performed so that the reduction ratio shown in Table 2 was obtained in total. The rolling reduction (total rolling reduction) of the cold rolling after solution treatment was calculated according to the following formula.
Reduction ratio (%) = 100 × [(Thickness during solution treatment) − (Thickness of product)] / (Thickness during solution treatment)

Various characteristics of each alloy plate thus obtained are shown in Tables 1-2. The measurement of each characteristic is as follows.
Tensile strength: The metal material tensile test method of JIS-Z2241 was followed.
Conductivity: According to the volume resistivity and conductivity measuring method of non-ferrous metal material of JIS-H0505.
Hardness: The Vickers hardness measurement method of JIS-Z2244 was followed.
Bending workability (W-bending): A bending test in which the bending axis is parallel (GW) and perpendicular (BW) to the rolling direction by the W-bending test method according to JCBA T307 (Japan Copper and Brass Association Standard). Each was carried out and indicated by the maximum bending radius (MBR / t).
Average crystal grain size: Evaluated using the cutting method of JIS-H0501. The grain size in the direction parallel to and perpendicular to the rolling direction was determined by using a cutting method in each direction.

  As is apparent from Tables 1 and 2, the alloy plates of Nos. 1 to 12 of the examples of the present invention have excellent tensile strength and bending workability while maintaining an electrical conductivity of 45% or more, Their mechanical properties have a very small difference between the direction parallel to and perpendicular to the rolling direction.

On the other hand, in Comparative Examples 13 and 14 with no B added, the crystal grains are coarsened even under the same solution conditions as in the Examples, and the bending workability is deteriorated.
In Comparative Examples 15, 16 and 17, since the solution treatment conditions are low, the conductivity after solution treatment is higher than that in the case where the additive element is completely dissolved, and 100 × (Ecb) / ( Eca) is over 120%. Therefore, the tensile strength of the final product is low.

  Comparative Examples 18 and 19 are examples in which B and Si are outside the range defined in the present invention. In Comparative Example 18 in which B is excessive, cracks occur during annealing and cold rolling, and Comparative Example in which Si is excessive. In No. 19, the electrical conductivity after the final process is low and the bending workability is also poor.

In Comparative Examples 20 and 21, oxygen and S are larger than the ranges specified in the present invention, respectively. However, in Comparative Example 20 with a large amount of oxygen, cracking occurs in the annealing and cold rolling processes, and in Comparative Example 21 with a large amount of S, hot rolling is performed. Sometimes ruptures occur, both of which are not manufacturable.
In Comparative Example 22, the solution treatment temperature is high, and the crystal grains after solution treatment are coarsened. Therefore, bending workability is extremely bad. In Comparative Example 23, since the rolling reduction after solution treatment is high, not only the bending workability is poor, but the difference in the crystal grain size between the parallel direction and the perpendicular direction with respect to the rolling direction increases, and the characteristic difference also increases accordingly. It has become.

It is a figure which shows the relationship between solution treatment temperature and electrical conductivity for demonstrating electrical conductivity (Eca) when an additional element carries out complete solid solution.

Claims (7)

Ni: 1.0~3.5mass%, Si: 0.2~0.8mass %, B: 0.002~0.03mass%, the balance: a Cu and copper-based alloy inevitable impurities, solution 100% (Ecb) / (Eca) of the conductivity (Ecb) after crystallization and the conductivity (Eca) when the additive element is completely solid solution is 120% or less, and the average crystal grain size after solution treatment D _AV is more than 2 to 20 μm or less, the tensile strength is 700 N / mm ² or more, the ratio of the tensile strength in the direction parallel to and perpendicular to the rolling direction is 95 to 105%, the conductivity is 45% IACS or more, bending The workability is 0 to 1.0 (MBR / t), the ratio of the MBR / t value in the direction parallel to and perpendicular to the rolling direction is 95 to 105%, the average in the direction parallel to the rolling direction on the plate surface The average crystal grain size b in the direction perpendicular to the crystal grain size a is 10 μm or less. In and the ratio a / b is 0.5 to 2.0 copper-based alloy. Ni: 1.5-3 mass% , Si: 0.32-0.57 mass% , B: 0.003-0.02 mass% , balance: Cu-based alloy composed of Cu and inevitable impurities , after solutionization The ratio 100% (Ecb) / (Eca) of the electrical conductivity (Ecb) of the alloy and the electrical conductivity (Eca) when the additive element is completely dissolved is 102 to 106%, and the average grain size D after the solution treatment _AV is 4 to 9 μm, tensile strength is 701 to 803 N / mm ² , the ratio of tensile strength in the direction parallel to and perpendicular to the rolling direction is 98 to 103%, and conductivity is 45.8 to 53.8%. IACS , the bending workability is 0 to 0.8 (MBR / t), the ratio of the MBR / t value in the direction parallel to and perpendicular to the rolling direction is 100%, and the direction parallel to the rolling direction on the plate surface The average crystal grain size b in the direction perpendicular to the average crystal grain size a is 1. A copper-based alloy having 9 to 4.9 μm and a ratio a / b of 0.9 to 1.8 .   Ca: 0.0001-0.005 mass%, C: 0.0001-0.005 mass%, P: 0.01-0.3 mass%, Fe: 0.01-0.3 mass%, one or more The copper base alloy according to claim 1, further containing a total of 0.5 mass% or less.   Co: 0.05 to 0.5 mass%, Ag: 0.002 to 0.2 mass%, Sn: 0.02 to 2.0 mass%, Zn: 0.02 to 2.0 mass%, or one or more types The copper base alloy according to claim 1, further comprising 2.0 mass% or less in total.   The copper-based alloy according to any one of claims 1 to 4, wherein the S content is 15 ppm or less and the oxygen content is 30 ppm or less. When the copper-based alloy according to any one of claims 1 to 5 is manufactured, an intermediate product comprising a hot-rolled sheet or a cold-rolled sheet having the alloy composition is subjected to a solution treatment at 680 to 850 ° C and then 450 to 500. The aging treatment at 0 ° C. , and after the solution treatment and before or after the aging treatment, a finish cold rolling with a total rolling reduction of 60% or less is performed . A method for producing a copper-based alloy. 6. After manufacturing the copper-based alloy according to any one of claims 1 to 5, after subjecting an intermediate product comprising a hot-rolled sheet or a cold-rolled sheet having the alloy composition at a temperature of 680 to 850 ° C. for less than 10 minutes. 450 to 500 ° C. in 30 to 1200 minutes aging treatment can be, and the total rolling reduction before or after the after aging treatment solution treatment for 60% or less of the finish cold rolling, claims 1, characterized in A method for producing the copper-based alloy according to any one of 5 .

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