JP2892508B2 - High strength copper alloy with good hot workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy excellent in strength, spring property and conductivity, suitable for use in electrical and electronic equipment parts such as connectors, terminals and lead frames.

[0002]

2. Description of the Related Art Conventionally, copper alloy strips used for electrical and electronic equipment parts such as connectors, terminals, lead frames, etc.
Sn-containing copper and Fe-containing copper such as C194 have been used, but as electrical and electronic equipment has become smaller, lighter, and more dense, a high balance of strength, springiness, and conductivity is required. It is becoming difficult to deal with such copper alloys. Therefore, recently, a so-called Corson-based copper alloy of a Cu-Ni-Si system (Ni: 2.0 to 4.0%, Si: 0.4
~ 1.0%, balance Cu. % Is% by weight, the same applies hereinafter).

[0003]

However, although the Corson-based copper alloy is excellent in practical properties such as strength, spring property and conductivity, it has a remarkable drawback in ease of production. Has not yet been widely used.

[0004] In other words, in order to produce copper alloy strips industrially at low cost, an ingot having a large cross-sectional area is produced at the time of melting and casting, and this is hot-rolled at a high temperature of 700 ° C or more to produce a rolled material. It is necessary. However, in the heating process for hot rolling, corson-based copper alloys generate brittle cracks due to the action of residual stress during solidification, which adversely affects subsequent hot rolling and significantly reduces the yield. It has become.

[0005] Since the brittle cracks occur more remarkably in a cast material having a large residual area with a large residual stress, conventionally, the brittle crack in the heating step is avoided by reducing the sectional area of the cast material. However, in this method, productivity is low and manufacturing cost is high.

[0006] In order to solve these problems, measures have been published to improve the hot rolling property by adding Mn, Mg, etc. to the Corson-based copper alloy. The effect of reducing cracks in the preceding heating step is not always sufficient, and has little effect on reducing manufacturing costs.

[0007] Therefore, the present invention is to prevent cracking of a Cu-Ni-Si alloy excellent in strength, spring property and conductivity in a heating step prior to hot rolling, and to enhance hot workability. An object is to provide a high-strength copper alloy that can be manufactured at low cost.

[0008]

The high-strength copper alloy having good hot workability according to the present invention comprises Ni: 2.0 to 4.0% and Si: 0.4 to 4.0%.
1.0%, P: 0.01 to 0.05%, the balance being Cu and unavoidable impurities, and the grain size of the cast material is 10 mm or less. In addition, in some cases, Zn: 0.05 to 1.0% is added to the alloy to improve solderability.

[0009]

In the case of hot rolling a cast material of a Cu-Ni-Si alloy, the hot working temperature is desirably 700 to 1000 ° C, and the cast material is heated to this temperature in a heating furnace. At this time, 40
Various studies have shown that when passing through the temperature range of 0-700 ° C., the cast material becomes brittle at the grain boundaries and cracks.

As a result of a detailed study of this cracking phenomenon, Cu-
In a cast material of a Ni-Si alloy, a large residual stress is generated during solidification of the molten metal, and this is relaxed in a temperature region of 400 to 700 ° C. At this time, a void-like defect is generated at a crystal grain boundary. It was found that the void-like defects were connected to form brittle cracks.

Conventionally, it has been known that in a copper alloy containing a large amount of Ni, the sulfur contained in the raw material Ni significantly deteriorates the hot workability. This is an attempt to improve hot workability.

On the other hand, Ni: 2.0-4.0%, Si: 0.4-
In the case of a Cu-Ni-Si alloy casting material containing 1.0%, unlike ordinary Ni-containing copper alloys such as cupronickel, the presence of P used for deoxidation of molten metal decreases the grain boundary strength of the casting material. It was clarified that it significantly reduced and accelerated the generation of cracks when passing through the temperature range of 400-700 ° C. From these research results, the present inventors have found that cracking in the heating step can be prevented by suppressing the P content to 0.01% or less.

However, if the content of P is set to 0.01% or less, it is necessary to purify the raw material industrially, which raises a problem of an increase in raw material cost.

Therefore, in order to find a measure for preventing cracking in a region where the P content is 0.01% or more, various studies were made on the relationship between the crystal grain size of the cast material and brittle cracking. As a result, as described above, since cracks in the cast material are caused by connection of the void-like defects generated at the crystal grain boundaries of the cast material, even if the defects occur, they do not grow into cracks, and if they are small, It has been found that even if a crack is formed, brittle cracking does not occur if the propagation of the crack is prevented. That is, in order to enhance the effect of improving cracks, it is only necessary to reduce the crystal grain size during solidification of the cast material and suppress the propagation of cracks.

According to the examination results, in order to prevent cracking at a P content of 0.01% or more, it is necessary to reduce the crystal grain size of the cast material to 10 mm or less, and if it exceeds 10 mm, the effect of preventing cracking appears sufficiently. Absent. Also, even if the grain size is 10 mm or less,
If the content exceeds 0.05%, the sensitivity of P to brittle cracking increases, and the effect of improving cracking by adjusting the crystal grain size does not sufficiently appear. Therefore, the content of P needs to be 0.05% or less.

When the content of P is in the range of 0.01 to 0.05%, the cost of the raw material is low because the raw material does not need to be refined, and the crystal grain size of the cast material is reduced to 10 mm or less to prevent cracking during hot working. The processing cost can be reduced because it can be prevented. Therefore, a high-strength copper alloy having a low production cost can be obtained as a whole.

[0017]

The present invention will be described below in more detail with reference to examples. A copper alloy having the composition shown in Table 1 was melted and cast to a thickness of 200 m.
m, a cast material having a width of 1200 mm was manufactured. Also thickness 1 for comparison
Casting materials with a small cross section of 20 mm and a width of 500 mm were also manufactured. At the same time, at the time of melt casting, casting materials having various crystal grain sizes were obtained by changing the temperature of the mold into which the molten metal was poured.

Each cast material was placed in a heating furnace at 950 ° C., heated to 950 ° C. and maintained for 5 hours, and then hot-rolled to a thickness of 30 mm. The state of cracking was evaluated for the rolled sheet material. The evaluation was A for those that could be processed soundly, C for those that had cracks and could not be processed during hot rolling, and had a thickness of 30 mm.
The sample that was able to be processed to the point where cracks occurred and the yield was 80% or less was designated as B.

Next, the sheet material after the hot rolling is worked by repeating cold rolling and annealing to obtain a sheet material having a thickness of 0.3 mm. The sheet material is heated at 950 ° C. for 15 minutes, and then quenched in water. Thereafter, the sheet was subjected to cold rolling of 40% to a sheet thickness of 0.2 mm, and further subjected to aging treatment at 450 ° C. for 2 hours.

A tensile test was performed on the sheet material thus obtained, and the tensile strength (TS), 0.2% proof stress, and elongation were measured. In addition, conductivity (EC% IACS), spring limit (Kb
Value) was measured. In addition, the production cost was quantitatively evaluated in terms of raw material cost and processing cost, and the copper alloy according to the present invention was cast with a small cross-sectional area to a thickness of 0.2 m.
Based on the sum of raw material costs and processing costs when manufacturing m products, the rankings were large, medium, and small. The results are shown in Table 1.

[0021]

[Table 1]

As is apparent from Table 1, the embodiment of the present invention is shown.
No. In Nos. 1 to 3, even if the size of the cast material is large, no cracking occurs during hot rolling, the content of P is large, and the size of the cast material is large, so that the production cost is small.

On the other hand, Comparative Example No. Nos. 4 to 8 have no cracks during hot rolling even if the size of the cast material is large,
Since the content of P is small, the raw material cost is high, and the production cost is medium. In Comparative Example No. No. 9 has the same P content as that of the present invention, but since the grain size of the cast material is large, even if the size of the cast material is reduced, cracks may occur during hot rolling, and the production cost is low. Inside. In Comparative Example No. In Nos. 10 to 12, the content of P and the size of the cast material are the same as those of the present invention, but since the crystal grain size is large, cracks are generated during hot rolling and processing is impossible. Further, Comparative Example No.
No. 13, cracks during hot rolling are improved by the addition of Mn and Mg, but the effect is insufficient, and the production cost increases.

The copper alloy of the present invention has a Ni: 2.0
~ 4.0%, Si: 0.4 ~ 1.0%, P: 0.01 ~ 0.05%,
The balance is made up of Cu and unavoidable impurities, and is characterized in that the crystal grain size of the cast material is 10 mm or less. Zn may be further added to this composition in an amount of 0.05 to 1.0%. Addition of zinc is effective for improving solderability. Table 2 shows Examples and Comparative Examples in which Zn was added.

[0025]

[Table 2]

[0026]

As described above, according to the present invention, a Corson-based copper alloy having strength, spring property and conductivity suitable for electric and electronic equipment parts such as connectors and lead frames can be produced during hot working. Since cracks can be prevented, the product yield is improved, and manufacturing with a large cast material is possible, so that manufacturing efficiency is greatly improved. For this reason, the production cost of Corson-based copper alloy can be significantly reduced,
An industrially remarkable effect that the range of use can be expanded is obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22F 1/00 661 C22F 1/00 661A 681 681 (72) Inventor Koichi Yoshida 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Kogyo Co., Ltd. (56) References JP-A-63-130739 (JP, A) JP-A-2-290936 (JP, A) JP-A-59-74251 (JP, A) Nittsuka Rensei, “Copper lead frame Materials Development Trends and Some Problems ”, Metals, Agne Co., Ltd., July 1989, Vol. 59, No. 7, pp. 77-85 (58) Fields surveyed (Int. Cl. ⁶ , (DB name) C22C 9/00-9/10 C22F 1/08

Claims (2)

(57) [Claims] 1. Ni: 2.0 to 4.0% (% by weight, the same applies hereinafter);
High strength copper with good hot workability, characterized in that Si: 0.4-1.0%, P: 0.01-0.05%, the balance consists of Cu and unavoidable impurities, and the grain size of the cast material is 10 mm or less. alloy. 2. Ni: 2.0-4.0%, Si: 0.4-1.0%, P:
A high-strength copper alloy containing 0.01 to 0.05% and Zn: 0.05 to 1.0%, with the balance being Cu and unavoidable impurities, and having a cast material having a grain size of 10 mm or less.