JPH05156387A - Copper alloy for resistance welding electrode - Google Patents

Abstract

PURPOSE:To improve the service life of an electrode in the spot welding for a surface treated steel sheet or an Al alloy sheet used in the automobile industry or the like by forming it of a Cu allay contg. a specified amt. of Fe. CONSTITUTION:This copper allay for a resistance welding electrode contains, by weight, 4.5 to 20% Fe and the balance Cu and contains oxygen in the ratio of <=5 O2/Fe. In this allay, precipitated Fe is oxidized on the surface of an electrode by heat treatment and welding heat to prevent its reaction with the material to be welded, and even in the case the oxide is dropped off in the process of welding, Fe on the surface of the electrode is oxidized by welding heat, and it has a reproducing function. In the case the content of Fe is less than 4.5%, it is used only for its precipitation hardening, and the effect of its reproducing function is made insufficient because the amt. of Fe oxide to be formed is very small; and in the case it exceeds 20%, the heat conductivity and electric conductivity characteristic of Cu are deteriorated. This allay is manufactured by subjecting a material to melting and casting or subjecting rapidly solidified powder to HIP, thereafter subjecting it to hot extruding or executing allaying by laser-electron beams by an electrode tip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy for resistance welding electrodes, and more specifically, a copper alloy for resistance welding electrodes having a long life used for spot welding of surface-treated steel sheets and aluminum alloy sheets used in the automobile industry and the like. It is about.

[0002]

2. Description of the Related Art A reduction in the service life of electrodes in spot welding of galvanized steel sheets and aluminum alloy sheets is a major problem in the production of automobiles and the like, and the development of long-life spot welding electrodes is desired. 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 electric conductivity, thermal conductivity and softening resistance.

[0003]

However, it is difficult to obtain an electrode having all the characteristics because the above characteristics are in a mutually contradictory relationship. Further, in spot welding of a galvanized steel plate or an aluminum alloy plate, Zn and Cu and Al and Cu react with each other to form a brittle alloy layer, and a phenomenon occurs in which the alloy layer is separated. Therefore, the consumption of the electrode is accelerated, and the problem of shortening the life of the electrode is highlighted.

[0004]

As a result of various investigations in view of the above, the present invention has been carried out as a result of various investigations, and has a long life resistance welding excellent in thermal conductivity and conductivity required for a welding electrode and excellent in high temperature strength and high temperature heat resistance. This is a developed copper alloy for electrodes.

That is, one of the copper alloys of the present invention is Fe4.5 to
It is characterized in that it contains 20 wt% and the balance is Cu and unavoidable impurities.

Another one of the copper alloys of the present invention is Fe4.
It is characterized by containing 5 to ₂₀ wt% and oxygen of O ₂ / Fe ≦ 5, and the balance Cu and unavoidable impurities.

[0007]

As described above, the present invention contains Fe of 4.5 to 20 wt% and the balance Cu and unavoidable impurities. The crystallized Fe is oxidized on the surface of the electrode due to heat treatment and welding heat to form a welded material. It is characterized by preventing the reaction of No. 1 and regenerating the Fe on the electrode surface by the welding heat even if the oxide is desorbed during welding.

The first aspect of the present invention is a Cu-based alloy containing 4.5 to 20 wt% of Fe, and if Fe is crystallized and dispersed in a Cu matrix, the thermal conductivity and the electrical conductivity are not lowered so much. It has been found that it is possible to have hardness and high temperature heat resistance. That is, originally Fe of Cu-Fe alloy
The solid solution limit is 4.0 wt%, and even if it is added more than that, it does not contribute to precipitation hardening. Therefore, the alloy of the present invention is
By adding e above the solid solution limit and crystallizing and dispersing Fe in the Cu matrix, this Fe oxidizes at the electrode surface due to welding heat, and therefore, Fe oxide in the Cu-Fe precipitation hardening alloy matrix on the surface. Are dispersed composite materials. Therefore, 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, the amount of Fe added is 4.5 to 20 wt%.
The reason is that if less than 4.5 wt%, it is used only for precipitation hardening, and the amount of Fe oxide formed is very small, so the effect of the regeneration function becomes insufficient. This is to reduce the rate. If desired, this alloy may be heat-treated in an oxygen atmosphere.

The second aspect of the present invention is Fe 4.5 to 20 wt%.
And a Cu alloy containing oxygen of O ₂ / Fe ≦ 5 as a necessary component, in which a Fe oxide and an Fe crystallized substance are dispersed using a Cu—Fe precipitation hardening alloy as a matrix. This composite material is produced by controlling the amount of oxygen during casting, and then heat-treated in an oxygen atmosphere if necessary. As a result, as in the first case of the present invention, 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 regenerating function. Is.

However, the reason why the amount of Fe added is limited to 4.5 to 20 wt% is that if it is less than 4.5 wt%, it is used only for precipitation hardening, and the formation of Fe oxide is so small that the regeneration function effect becomes insufficient. This is because if it exceeds 20 wt%, the original thermal conductivity and electrical conductivity of Cu are reduced. The oxygen content is O
_The limitation of ₂ / Fe to 5 or less is that when O ₂ / Fe exceeds 5, all Fe crystallized substances become oxides and the Cu base material and Cu-Fe precipitates are oxidized. This is because the characteristics are deteriorated.

The alloy of the present invention can be produced by hot-extrusion after melt-casting, HIP (hot isostatic pressing) of rapidly solidified powder, and then hot-extrusion, or laser or electron at an electrode tip. Beam alloying or the like is used.

[0013]

EXAMPLES The present invention will be described below with reference to examples. Table 1
A resistance welding electrode having a tip shape diameter of 16 mm and a diameter of 150 mm was manufactured by the following method using the alloy having the composition shown in FIG.

Inventive Example 1; Cu-4.5 wt% F by melting method
After producing an ingot of the e alloy, it was hot extruded at 700 ° C. to obtain a bar material having a diameter of 16 mm.

Inventive Example 2; Cu in the same manner as in Inventive Example 1
A bar material of -10 wt% Fe alloy with a diameter of 16 mm was used.

Inventive Example 3 A rapidly solidified powder of a Cu-15 wt% Fe alloy produced by the gas atomizing method was HI at 800 ° C.
After P treatment, the diameter is 16mm by hot extrusion at 700 ℃.
It was used as a bar material.

Inventive Example 4; Cu in the same manner as in Inventive Example 3
A bar material of -20 wt% Fe alloy with a diameter of 16 mm was used.

Inventive Example 5: An ingot of Cu-10 wt% Fe-0.5 wt% O ₂ alloy was prepared in an oxygen atmosphere by a melting method and then hot extruded at 700 ° C. to obtain a bar material having a diameter of 16 mm. ..

Inventive Example 6; Cu in the same manner as in Inventive Example 5
A bar material of -10 wt% Fe-15 wt% O ₂ alloy with a diameter of 16 mm was used.

Inventive Example 7: Cu-10 wt% Fe alloy produced in the same manner as in Inventive Example 2 has a diameter of 16 mm-150 mmR.
Laser irradiation was performed on the central portion of the contact surface of the resistance welding electrode while blowing an O ₂ assist gas to form a rapidly solidified portion (Cu-10 wt% Fe-30 wt% O ₂ ) having a diameter of 5 mm and a depth of 2 mm.

Inventive Example 8: A rapidly solidified portion (Cu-10 wt% Fe-50 wt% O ₂ ) was formed in the same manner as in Inventive Example 7.

Comparative Example 9: Cu-
A rod material having a diameter of 16 mm and made of a 3 wt% Fe alloy was used.

Comparative Example 10: Cu was prepared in the same manner as in Example 3 of the present invention.
A bar material of -25 wt% Fe alloy with a diameter of 16 mm was used.

Comparative Example 11: Cu was prepared in the same manner as Example 7 of the present invention.
A rapidly solidified part of -10 wt% Fe-60 wt% O ₂ was formed.

Using the electrode manufactured by the above method, a thickness of 0.
8mm galvanized steel plate and 1.0mm thick aluminum alloy plate (JIS5052 (Al-2.5wt% Mg-0.25wt
% Cr)) was subjected to continuous spot welding, and the life (number of dots) of the electrode was examined. The results are also shown in Table 1. As for the welding conditions, for galvanized steel sheet, the welding current is 12,500 A, the applied pressure is 200 kg, the energization time is 5 cycles,
The aluminum alloy plate was welded at a current of 20000 A, a pressure of 200 kg, and an energization time of 5 cycles. In addition, the electrode life was evaluated by measuring the nugget diameter and determining the life when the diameter was less than 4.5 mm.

[0026]

[Table 1]

From Table 1, according to the example of the present invention, the life is 3300 to 3700 for galvanized steel sheets and 3 for aluminum alloy sheets.
The number of hit points is 100 to 3,400, which is extremely excellent. On the other hand, according to the comparative example which is out of the composition range of the present invention, the galvanized steel sheet is 1500 to 180.
It can be seen that the life of the aluminum alloy plate is inferior because the aluminum alloy plate has 1400 to 1600 hit points.

[0028]

As described above, according to the present invention, high temperature strength,
A resistance welding electrode excellent in high temperature heat resistance can be obtained, and a remarkable effect that the life of the electrode can be dramatically improved is exhibited.

Front page continuation (72) Inventor Tomiharu Okita 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Aluminum Industry Co., Ltd.

Claims (2)

[Claims] 1. A balance of Fe containing 4.5 to 20 wt% and a balance of C
A copper alloy for a resistance welding electrode, which comprises u and unavoidable impurities. _2. Fe 4.5 to 20 wt% and 0 ₂ / Fe ≦
A copper alloy for a resistance welding electrode, which contains oxygen of 5 and is composed of the balance Cu and unavoidable impurities.