JPH05135623A - Copper clad wire rod - Google Patents

Abstract

PURPOSE:To provide a copper clad wire rod whose strength, toughness and corrosion resistance are good. CONSTITUTION:The copper clad wire rod is a copper clad wire rod made up of a copper external layer and a copper core and the core contains C at 0.2-0.4-wt. %, Si at 0.2-0.4wt.%, Mn at 1.5-2.5wt.%, Cr at 9.0-11.0wt.%, and the remainder is made up of Fe and unavoidable impurities, and P and S as impurities are steels whose compositions are 0.015wt.% or less respectively. The wire rod is of high strength so that it can be used for cables to transfer power and signals of industrial machines, cars, etc., with a smaller diameter than those of conventional ones.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has high strength and high toughness, and is used for electric signal transmission wires, electric power transmission cables, etc. in the fields of automobiles, industrial machines, etc., copper clad wire (copper clad wire). Regarding

[0002]

2. Description of the Related Art A thin wire made of a copper alloy is conventionally used for transmission of electric signals and electric power in automobiles and industrial machines. However, although the copper alloy is excellent in electrical conductivity and corrosion resistance, it has a drawback of low strength.

Recently, in automobiles and industrial machines, the use of wires has been remarkably increased due to the significant progress in electronics and the accompanying increase in the amount of electric power and signals to be transmitted. Such wires are required to have a certain level of strength and toughness in order to withstand a dynamic load when assembling parts such as automobiles. Therefore, efforts were made to increase the strength and toughness of the wire itself so that a wire with a small cross-sectional area could be used in time so as to reduce the total amount of the wire used. It's coming.

For example, a copper clad wire rod for an automobile harness wire is manufactured by clad an element wire rod as shown in Table 1 with copper, drawing the wire, and then subjecting it to heat treatment such as annealing and tempering. ..

Table 1 summarizes the characteristics of the conventional core material and the copper clad wire using the core material. As shown, carbon steel (JISS45C) and austenitic stainless steel (SUS304) are often used as core materials, but none of them satisfy all of the target performances.

[0006]

[Table 1]

The clad wire used for the above-mentioned applications has a tensile strength of 150 kgf / mm ² or more,
Tensile absorbency energy of 10 kgf-mm / mm ³ or more (energy measured from tensile load-strain curve) is required for toughness, and corrosion resistance is required to prevent crevice corrosion from occurring with copper in the outer layer in a salt spray test. However, carbon steels such as S45C have completely insufficient corrosion resistance. The strength can be increased by wire drawing to achieve the target, but then the toughness becomes insufficient.

Austenitic stainless steels such as SUS 304 have sufficient corrosion resistance but insufficient strength. Although the strength can be increased by wire drawing, the work hardening deteriorates the toughness. In addition, austenitic stainless steel requires heat treatment (solution treatment) to recover corrosion resistance after wire drawing, but the temperature is 100
Since the temperature exceeds 0 ° C, there is a problem that the outer layer copper is deteriorated or melted.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to provide a copper clad wire rod having excellent strength, toughness and corrosion resistance, and its object is to carry out a heat treatment during the production of the copper clad wire rod as an outer layer. Assuming that the temperature is less than 950 ° C, the temperature of copper is less affected by heat,
An object of the present invention is to provide a copper clad wire rod in which the chemical composition of the material used as the core material is optimally selected.

[0010]

The feature of the present invention is that the core material of the copper clad wire is C: 0.2 to 0.4% by weight and Si: 0.2 to 0.4% by weight.
Steel containing 0.4%, Mn: 1.5 to 2.5%, Cr: 9.0 to 11.0%, the balance Fe and unavoidable impurities, and P and S as impurities each having a composition of 0.015% or less is there.

The material for the outer layer is copper or a copper alloy conventionally used. In this specification, these are collectively referred to as copper or a copper outer layer. The thickness of the clad wire is usually about 7 mm, and the ratio of the copper outer layer to the core (cladding ratio) is
It is about 0.15.

The wire rod of the present invention is formed by cladding the core material with copper by a method such as plating, casting, and fitting a pipe, and then drawing the wire to a predetermined wire diameter, followed by heat treatment such as quenching and tempering. Manufactured. The quenching temperature may be 900 to 950 ° C, and there is no concern that it will adversely affect the copper outer layer material.

[0013]

First, the function of the alloy components of the steel to be the core material of the copper clad wire of the present invention and the reasons for limiting their contents will be described. All% related to the content of alloy components are% by weight.

C: 0.2 to 0.4% C is an effective component for improving the strength of the core material. If the content is less than 0.2%, the target strength as the core material cannot be obtained. On the other hand, if C exceeds 0.4%, Cr carbides are likely to be formed in the tempering stage, which not only deteriorates corrosion resistance but also decreases strength.

Si: 0.2 to 0.4% Si is a component that forms a solid solution in ferrite to improve the strength of steel. If the content is less than 0.2%, the strength of the core material does not satisfy the target value. On the other hand, if it exceeds 0.4%, the ductility of the core material becomes insufficient and the tensile absorbed energy becomes 10k of the target value.
Achieving gf-mm / mm ³ becomes difficult. Therefore, the proper range of Si content is 0.2 to 0.4%.

Mn: 1.5 to 2.5% Mn is a component that enhances the hardenability of steel, improves the strength and uniform elongation in tensile deformation, and as a result, increases tensile absorbed energy. Figure 1
C: 0.3%, Si: 0.3%, Cr: 9.0%, balance Fe and unavoidable impurities added to the steel containing various amounts of Mn as a core material, and copper produced under the same conditions as in the examples described later. It is the result of examining the relationship between the Mn content of the core material and the tensile absorbed energy of the clad wire.

As shown in the figure, when Mn exceeds 1.5%, the tensile absorption energy rises above the target value. However, if it exceeds 2.5%, on the contrary, the ductility deteriorates and the tensile absorbed energy falls below the target value. That is, the proper range of Mn content is 1.5 to 2.5%.

Cr: 9.0-11.0% Cr is a component which brings about a remarkable effect in improving the corrosion resistance.
However, if Cr becomes excessive, it becomes difficult to decompose and dissolve chromium carbide, and it becomes necessary to form a high temperature solution by heat treatment. In the case of a copper clad wire, since high temperature solution treatment cannot be performed as described above, the amount of solid solution Cr and solid solution C remains because the carbide remains as it is.
On the contrary, it decreases as the Cr content increases.

2 and 3, C: 0.3%, Si: 0.3%,
Mn: 2.0%, the balance of Fe and unavoidable impurities as a core material steel with a different Cr content was used as a core material, copper clad wire rod manufactured under the same conditions as in the examples described later, the Cr of the core material
It is the result of examining the relationship between the content and strength, and the Cr content and the tensile absorbed energy.

As shown in FIG. 2, the core material has a Cr content of 11.0.
If it exceeds%, the strength will not satisfy the target value. Also, looking at FIG. 3, here also, when the Cr content of the core material exceeds 11.0%, the tensile absorbed energy sharply decreases and falls below the target value.
From these results, it can be said that the upper limit of the Cr content is 11.0%.

FIG. 4 is the same as the test material of FIGS. 2 and 3.
It is the result of investigating the boundary rust depth of crevice corrosion by the test method described in the below-mentioned examples for those with only the Cr content changed. It can be seen that the Cr content needs to be 9% or more in order to reduce the boundary rust depth to the target value or less. For these reasons, the Cr content is 9.0-11.0%.

The core material of the clad wire of the present invention comprises, in addition to the above components, the balance of Fe and unavoidable impurities. Of these impurities, P and S in particular must be suppressed to 0.015% or less. Both P and S are components that impair the ductility of steel.
If each exceeds 0.015%, the ductility (tensile absorbed energy) cannot satisfy the target value.

[0023]

[Example] Steel having the chemical composition shown in Table 2 was melted in a 150 kg vacuum melting furnace to obtain a raw material, which was rolled into a wire rod having a diameter of 7.0 mm.

Steel Nos. 2, 3, 6, 7, 10, 11, 1 in Table 2
Nos. 6 and 17 are steels having a composition range defined in the present invention, and steel No.
1, 4, 5, 8, 9, 12, 13, 14, 15, and 18 are comparative examples in which the content of the alloy component marked with * is outside the range defined by the present invention.

Copper is clad with the above wire rod and drawn.
A copper clad wire having an outer diameter of 0.2 mm and a core material diameter of 0.17 mm was manufactured. After heating the obtained clad wire at 950 ℃,
After quenching with oil cooling and subsequent heat treatment at 300 ° C., tensile strength (TS) and tensile absorbed energy were measured.

Separately, the steel of Table 2 and the above copper material of the outer layer were combined and heat treated in the same manner to prepare a test piece as shown in FIG. 5, and crevice corrosion was investigated. The test conditions were a salt spray of 5% NaC1, a test temperature of 35 ° C., a test time of 100 hours, and the depth of rust generated at the boundary between the copper layer and the base material (steel core material). In this test, when the boundary rust depth was 0.05 mm or less, it was found that there was no problem in practical use, so this was set as the target value.

The above test results are summarized in Table 3.

[0028]

[Table 2]

[0029]

[Table 3]

As shown in Table 3, the copper-clad wire having a core material of steel having the chemical composition defined in the present invention (indicated as "Example of the present invention" in Table 3) has strength, tensile absorbed energy and corrosion resistance. In any case, the target value should be exceeded and it should be satisfied.

On the other hand, No. 1 among the comparative examples using steel having a composition outside the range defined in the present invention as the core material,
Both 5, 9 and 18 are inferior in both strength and tensile energy, and N
In o.8, 12, 13, and 14, the tensile absorbed energy does not satisfy the target value even if the strength satisfies the target value. In addition, No. 4 has low tensile absorption energy and poor corrosion resistance. Further, No. 15 is excellent in strength and tensile absorbed energy, but the corrosion resistance is poor because the Cr content of the core material is too low.

[0032]

The copper-clad wire of the present invention has high strength and toughness and high corrosion resistance.

This clad wire is useful as a cable for transmitting electric power and signals in industrial machines, automobiles, etc. Since it has high strength, it can be used with a smaller diameter than conventional ones.

[Brief description of drawings]

FIG. 1 is a result of investigating the relationship between the Mn content of steel as a core material and the tensile absorbed energy of a copper clad wire.

FIG. 2 is a result of investigating the relationship between the Cr content and the strength of the copper clad wire rod.

FIG. 3 is a result of investigating the relationship between the Cr content and the tensile absorbed energy of the copper clad wire.

FIG. 4 is a result of examining the boundary rust depth of crevice corrosion when copper and core steels having different Cr contents are combined.

FIG. 5 is a diagram showing the shape of a test piece for crevice corrosion.

Claims (1)

[Claims] 1. A clad wire rod comprising an outer layer of copper or a copper alloy and a steel core material, wherein the core material has a weight percentage of C: 0.2 to 0.4.
%, Si: 0.2 to 0.4%, Mn: 1.5 to 2.5%, Cr: 9.0 to 11.0%
And a balance of Fe and inevitable impurities, and P and S as impurities each having a composition of 0.015% or less, a copper clad wire rod.