JPH05185247A - Material for resistance welding electrode - Google Patents

Abstract

(57) [Summary] [Objective] To provide a material for a resistance welding electrode having good thermal conductivity and conductivity, excellent high temperature strength and high temperature heat resistance, and dramatically improving the life of the electrode. [Constitution] Fe containing 4.5 to 20 wt% or further O
₂ / Fe ≦ 5 oxygen is contained, and the outer diameter of the rod-shaped electrode of the high-strength, conductive copper alloy containing the balance Cu and unavoidable impurities has an inner diameter / outer diameter ratio of 0.4 to 0.7. Coat with copper or copper alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance welding electrode material, and more particularly to a long-life electrode material used for spot welding surface-treated steel sheets or aluminum alloy sheets used in the automobile industry and the like. is there.

[0002]

2. Description of the Related Art Reduction of electrode life in spot welding of galvanized steel sheet or aluminum alloy sheet is a serious problem in automobile production, and development of a long-life spot welding electrode has been demanded. There is. In order to improve the life of the spot welding electrode, it is considered necessary to improve the characteristics of the electrode material such as conductivity, thermal conductivity and softening resistance. However, since these characteristics are in a mutually contradictory relationship, it is difficult to create an electrode material having all the characteristics. Further, in spot welding of a galvanized steel plate and an aluminum alloy plate, zinc and copper and aluminum and copper react with each other to form a brittle alloy layer, and this alloy layer peels off. For this reason, the problem that the electrode is worn down and the life of the electrode is shortened has been highlighted.

[0003]

As a result of various studies in view of this, the present invention has been found to have thermal conductivity required for a resistance welding electrode,
We have developed a long-life resistance welding electrode material that has good electrical conductivity and excellent high-temperature strength and high-temperature heat resistance.

That is, one of the materials of the present invention is Fe4.5 to 2
0 wt% (hereinafter wt% is abbreviated as%), and the outer circumference of a rod-shaped internal electrode of a high-strength conductive copper alloy containing the balance Cu and unavoidable impurities has an inner diameter / outer diameter ratio of 0.4 to 0. It is characterized in that it is coated with a copper or copper alloy outer shell of No. 7.

Another material of the present invention is Fe4.5.
˜20%, oxygen of O ₂ / Fe ≦ 5, and the outer diameter of the rod-shaped electrode of the high-strength conductive alloy containing the balance Cu and unavoidable impurities with an inner diameter / outer diameter ratio of 0.4 to 0.7. It is characterized in that it is coated with a copper or copper alloy outer layer.

[0006]

The present invention is to develop a resistance welding electrode material having good heat resistance and welding resistance, improved tip cracking, and long hitting life. Therefore, as a result of earnest studies, it was found that it is the diameter of the internal electrode that is involved in resistance welding, and the outer skin thickness must be controlled in order to prevent cracking of the internal electrode.

Therefore, one of the materials of the present invention is Fe4.5-
The outer circumference of the rod-shaped internal electrode of high-strength conductive copper alloy containing 20% and the balance Cu and unavoidable impurities is covered with a copper or copper alloy shell having an inner diameter / outer diameter ratio of 0.4 to 0.7. The inner electrode is a copper alloy containing 4.5% to 20% of Fe, and if Fe is crystallized and dispersed in the Cu matrix, the internal electrode has a high hardness without significantly lowering thermal conductivity and conductivity. It is possible to have high temperature heat resistance. Originally Cu-Fe
The Fe solid solution limit amount of the alloy is 4.0%, and addition of more than that does not contribute to precipitation hardening.
When e is added to the solid solution limit or more and Fe crystallized and dispersed in the Cu matrix is oxidized on the surface of the electrode by heat treatment and welding heat, Fe is oxidized in the Cu-Fe precipitation hardening alloy matrix on the surface. It is a composite material in which objects are dispersed. As a result, it was found that the reaction between the electrode and the material to be welded is prevented, and even if the oxide is desorbed during welding, Fe on the electrode surface is oxidized by the welding heat and has a regeneration function. However, if the added amount of Fe is less than 4.5%, it is used only for precipitation hardening, and the amount of Fe oxide formed is so small that the effect of the regeneration function becomes insufficient.
If it exceeds, the original thermal conductivity and electrical conductivity of Cu will be reduced.

Another aspect of the present invention is Fe4.5-20.
%, O ₂ / Fe ≦ 5 oxygen, and the outer circumference of the rod-shaped internal electrode of high-strength conductive copper alloy containing the balance Cu and unavoidable impurities has an inner diameter / outer diameter ratio of 0.4 to 0.7. The inner electrode is coated with Fe4.5-
It is a Cu alloy containing oxygen of 20% and O ₂ / Fe ≦ 5, and if Fe is crystallized and dispersed in a Cu matrix, it has high hardness and high temperature heat resistance without significantly lowering thermal conductivity and conductivity. It is possible to have Originally F of Cu-Fe alloy
e The solid solution limit amount is 4.0%, and addition of more than that does not contribute to precipitation hardening. However, the present inventors added Fe to the solid solution limit or more and crystallized and dispersed in the Cu matrix. The Fe thus oxidized is oxidized on the surface of the electrode by heat treatment and welding heat, and Fe is contained in the Cu-Fe precipitation hardening alloy matrix on the surface.
It is a composite material in which oxides are dispersed. As a result, it was found that the reaction between the electrode and the material to be welded is prevented, and even if the oxide is desorbed during welding, Fe on the electrode surface is oxidized by the welding heat and has a regeneration function. However, if the added amount of Fe is less than 4.5%, it is used only for precipitation hardening, and the effect of the regeneration function becomes insufficient due to the small amount of Fe oxide formed. Reduces conductivity and conductivity. On the other hand, as the oxygen content, if O ₂ / Fe exceeds 5, all the Fe crystallized substances become oxides, and the Cu base material and Cu—Fe precipitates are oxidized, which deteriorates the regeneration function characteristics.

However, during welding at the time of welding, cracks may occur at the tip of the electrode, and this causes the crack pattern to be transferred to the material to be welded, impairing the appearance of the material to be welded. It was Even if an electrode having such cracks is used, there is no problem in welding, but in order to improve the appearance,
It is necessary to re-grind the tip of the electrode and remove only the cracked depth. However, not only the number of steps is increased, but also the life of the electrode itself is shortened, so it is necessary to have excellent crack resistance and dot life. Therefore, as a result of various studies that proceeded various studies, in order to obtain a resistance welding electrode with good heat resistance and welding resistance, and with a long spot life without tip cracks, the diameter of the internal electrode and the thickness of the outer skin layer It turns out that I have to control. As a result, copper or a copper alloy is used for the outer skin layer, and the ratio of inner diameter / outer diameter thereof is 0.
It is coated so as to be 4 to 0.7. However, if the ratio of inner diameter / outer diameter is less than 0.4, the outer skin layer comes into contact with the material to be welded, and the reaction between the outer skin layer and the material to be welded proceeds, causing welding and making the nugget shape unstable. On the other hand, when it exceeds 0.7, the thermal conductivity is lowered and the effect of protecting the internal electrodes by the outer skin layer is weakened, and cracks are likely to occur.

As the method for producing the electrode of the present invention, the internal electrode is molded or melted by a melting method and hot extruded, and then inserted into a cylindrical copper or copper alloy, and hot extruded or drawn into a rod shape. Or prepare a powder body as an internal electrode material, and fill this into a cylindrical copper or copper alloy,
HIP (hot isostatic press) / hot extrusion / pulling or hot extrusion / pulling to form rods.

[0011]

EXAMPLES The present invention will be described below with reference to examples. Table 1
An electrode having an inner diameter / outer diameter ratio shown in Table 1 was produced by the following method using a copper alloy having the internal electrode composition shown in and the outer skin.

Inventive Example 1; Internal electrode composition Cu-
After creating a 4.5% Fe billet, insert it into a copper pipe that serves as an outer skin, and hot extrude at 700 ° C
A 16 mm diameter rod-shaped electrode having an outer diameter ratio of 0.55 was processed.

Inventive Example 2 Using a billet having an internal electrode composition of Cu-10%, a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.55 was processed in the same manner as in Inventive Example 1.

Inventive Example 3; A copper pipe as an outer shell was filled with a rapidly solidified powder having an internal electrode composition of Cu-15% Fe prepared by a gas atomizing method, HIP-treated at 800 ° C, and then hot-extruded at 700 ° C. The rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.55 was processed.

Inventive Example 4; Internal electrode composition Cu-20% F
Using the powder of e, in the same manner as in Example 3 of the present invention, a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.55 was processed.

Inventive Example 5: A billet having an internal electrode composition of Cu-10% Fe-5% O ₂ was prepared in an oxygen atmosphere by a melting method, inserted into a copper pipe as an outer shell, and hot extruded at 700 ° C. 16mm diameter with inner / outer diameter ratio of 0.55
Processed into a rod-shaped electrode.

Inventive Example 6; Internal electrode composition Cu-10% F
Using a billet of e-25% O ₂ , a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.55 was processed in the same manner as in Example 5 of the present invention.

Inventive Example 7; Cu-10% Fe powder was prepared in an oxygen atmosphere in an attritor to prepare an internal electrode composition Cu-
10% Fe-45% O ₂ was filled in a copper pipe serving as an outer shell, HIP-treated at 800 ° C., and then hot extruded at 700 ° C. to form a rod-shaped electrode having a diameter / outer diameter ratio of 0.55 and a diameter of 16 mm. Processed into.

Inventive Example 8; Internal electrode composition Cu-
After forming a billet of 10% Fe, the billet was inserted into a copper pipe as an outer shell, and hot extruded at 700 ° C. to form a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.4.

Inventive Example 9: In the same manner as in Inventive Example 8, a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.7 was processed.

Inventive Example 10; Internal electrode composition Cu by melting method
After making a billet of -10% Fe, Cu which is the outer skin
It was inserted into a pipe made of -0.8% Cr alloy and hot extruded at 700 ° C to form a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.55.

Comparative Example 11: Internal electrode composition Cu-3% Fe
Using the above billet, a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.55 was processed in the same manner as in Example 1 of the present invention.

Comparative Example 12: Internal electrode composition Cu-25% F
Using the powder of e, in the same manner as in Example 3 of the present invention, a rod-shaped electrode having an inner diameter / outer diameter ratio of 0.55 and a diameter of 16 mm was processed.

Comparative Example 13: Internal electrode composition Cu-10% F
Using a powder of e-60% O ₂ , a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.55 was processed in the same manner as in Example 7 of the present invention.

Comparative Example 14: In the same manner as in Example 8 of the present invention, a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.3 was processed.

Comparative Example 15: In the same manner as in Example 8 of the present invention, a rod-shaped electrode having a diameter of 16 mm and an inner diameter / outer diameter ratio of 0.3 was processed.

Using the above electrodes, a galvanized steel plate having a plate thickness of 0.8 mm and an aluminum alloy plate having a plate thickness of 1.0 mm (JIS505
2 (Al-2.5% Mg-0.25% Cr alloy)) was continuously spot welded and the life thereof was examined. The results are also shown in Table 1. The welding conditions were: galvanized steel sheet, welding current 12,500 A, applied pressure 200 kg, energization time 5 cycles, and aluminum alloy, welding current 20000 A, applied pressure 200 kg, energization time 5 cycles. The life is evaluated by measuring the nugget diameter and measuring the diameter 4.
The life was defined as the time when the length became 5 mm or less.

[0028]

[Table 1]

As is clear from Table 1, the electrodes in the examples of the present invention have a life (number of dots) of 50 with respect to the galvanized steel sheet.
0 to 6500, and the life (spot number) of the aluminum alloy plate is 4000 to 5500, which shows that it is remarkably excellent as a resistance welding electrode. On the other hand, if the internal electrode composition or the inner diameter / outer diameter ratio deviates from the conditions of the present invention, the life (number of dots) is inferior to both the galvanized steel sheet and the aluminum alloy sheet. In Table 1, the crack of Comparative Example 15 indicates a crack on the surface of the internal electrode.

[0030]

As described above, according to the present invention, thermal conductivity,
It has excellent electrical conductivity, excellent high-temperature strength and high-temperature heat resistance, and can significantly improve the life of the electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomiharu Okita 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Co., Ltd.

Claims (2)

[Claims] 1. A balance of Fe containing 4.5 to 20 wt% and a balance of C
A resistance characterized by coating the outer circumference of a rod-shaped internal electrode of a high-strength conductive copper alloy composed of u and unavoidable impurities with a copper or copper alloy skin having an inner diameter / outer diameter ratio of 0.4 to 0.7. Materials for welding electrodes. _2. Fe 4.5 to 20 wt%, O ₂ / Fe ≦ 5
The outer periphery of the rod-shaped inner electrode of high-strength conductive copper alloy containing oxygen and the balance Cu and unavoidable impurities is covered with a copper or copper alloy shell having an inner diameter / outer diameter ratio of 0.4 to 0.7. A material for a resistance welding electrode characterized by being coated.