JPH0637700B2 - Method for producing copper alloy for resistance welding electrode - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a copper alloy used for an electrode for electric resistance welding, which has high conductivity and high hardness, has a small crystal grain, and has an appearance of a welded portion. The present invention relates to a method for producing a copper alloy for resistance welding electrodes, which prevents damage and a decrease in welding strength.

2. Description of the Related Art Electric resistance welding is a method for conducting welding through an object to be welded, that is, a contact portion of a member to be joined, heating by using resistance heat generated, and applying pressure to perform welding.
Lap resistance welding such as seam welding and butt resistance welding such as butt welding and butt seam welding are roughly classified.

In such resistance welding, an electrode that acts to apply pressure while in contact with a workpiece is indispensable, generally, copper or copper alloy material is used, depending on the welding species and applications, An electrode processed into a required shape is used.

As described above, the electrodes for resistance welding are required to have the functions of energization and pressurization. Therefore, the copper alloy material is required to have high conductivity and excellent wear resistance, that is, high hardness. ing.

For example, cold drawn copper electrodes are inexpensive and have the required hardness, but they tend to soften and deform during use, so a 0.5Cr-Cu alloy,
0.2Zr-Cu alloy or 0.5B-Cu alloy is used.

Furthermore, the copper alloy as the electrode material is required to have sufficiently small crystal grains. That is, if the crystal grains are large,
It is known that during use, cracks are generated from the crystal grain boundaries and the crystal grains are lost due to the cracks, which impairs the appearance of the surface of the workpiece to be welded and further causes a decrease in welding strength.

Generally, a Be-Cu-Co-Ni alloy for resistance welding electrodes is, after being melted, processed into a rod having a required diameter by hot working, for example, heating to 840 ° C, and liquefaction treatment (for example, 950 It is manufactured by subjecting it to age hardening treatment (for example, 425 ° C x 12h furnace cooling) after ℃ x 2h water cooling).

The electrode material obtained by such a manufacturing method satisfies the electrical and mechanical properties, but only the crystal grains in the vicinity of the surface become extremely coarse, for example, a coarsening phenomenon that reaches several mm occurs. was there.

Therefore, the material cannot be used with sufficiently increased hardness, and the yield is poor, and there is a problem of material loss.

Therefore, in the conventional manufacturing method, coarse crystals (diameter 1
mm or more), it was necessary to lower the liquefaction temperature as much as possible or to remove the region where coarse crystals were generated by cutting.

The cause of crystal grain coarsening on the surface of the electrode material is that the strain applied during hot working remains unreleased due to the temperature drop during working, and becomes the driving force for crystal grain coarsening during liquefaction processing. It can be estimated that

Particularly, the surface temperature of the electrode material is likely to decrease due to the contact with the tool, and this phenomenon is considered to occur easily.

OBJECT OF THE INVENTION The present invention prevents crystal grain coarsening on the surface of an electrode material used for resistance welding, has high conductivity and high hardness, and has a small crystal grain, which damages the appearance of the welded portion and reduces the welding strength. An object of the present invention is to provide a manufacturing method for obtaining a copper alloy for a resistance-welding electrode that does not have any defects.

SUMMARY OF THE INVENTION The present invention is produced by performing various studies for the purpose of a production method capable of preventing crystal grain coarsening on the surface of an electrode material, and performing required cold working after melting and hot working and before solution treatment. As a result, it was found that the coarsening of crystal grains can be prevented, and the present invention was completed.

That is, the present invention contains Be0.2wt% to 0.8wt%, Co0.5wt% to 1.5wt%, Ni0.5wt% to 1.5wt%, Mg0.0005wt% to 0.1wt% balance Cu and unavoidable impurities. The alloy is hot-worked at 600 ℃ -1000 ℃, then cold-worked at a surface reduction rate of 5% -50%, and solution heat-treated at 900 ℃ -1000 ℃ for 30 minutes-5 hours. After that, an aging treatment is performed at 370 ° C to 480 ° C for 30 minutes to 20 hours to obtain a copper alloy having a Rockwell C hardness of 20 or more, an electrical conductivity of 40% or more, and small crystal grains. It is a manufacturing method of a copper alloy for electrodes for resistance welding.

Structure of the Invention In the present invention, the reasons for limiting the components are as follows.

Be is added to have aging precipitation property, but 0.2 wt
If it is less than 0.1%, the strength of the material will be reduced, and if it exceeds 0.8% by weight, the electrical conductivity will be reduced, so 0.2 wt% to 0.8 wt% is added.

Co and Ni are added for the purpose of lowering the solid solubility limit of Be and increasing the precipitation ability, but if both are less than 0.5 wt%, the strength of the material will decrease, and if it exceeds 1.5 wt%, the conductivity will increase. Co or Ni is added in an amount of 0.5 wt.

Mg is added to prevent overaging, but if it is less than 0.0005 wt%, there is no overaging prevention effect, and if it exceeds 0.1 wt%, it deteriorates hot workability, so 0.0005 wt% to 0.
1wt% is added.

Cu forms the base of the alloy for this system electrode material, and is the balance of the additional elements.

In the present invention, the manufacturing conditions and the reasons for limitation are as follows.

The melting method and conditions are not particularly limited.

In the hot working process, the molten ingot is manufactured into a material with the required size and shape, but the temperature during processing such as forging is 60
If the temperature is below 0 ° C, the desired shape cannot be obtained, and 100
If the temperature exceeds 0 ° C, the heat generated during processing causes local overheating in the material, and the grain boundary part melts, making hot working impossible. Therefore, it is necessary to perform in the temperature range of 600 ° C to 1000 ° C. There is.

The cold working performed after the hot working and before the solution heat treatment, which is a feature of the present invention, does not allow hardening of crystal refinement when the area reduction rate is less than 5%, and the cold working exceeding 50%. It requires a very large work (workpiece) and cannot be used in practice, so it is necessary to perform cold working at 5% to 50%. Furthermore, it is preferably in the range of 10% to 30%.

If the solution heat treatment is less than 900 ° C, the required strength cannot be obtained even after the aging treatment, and if the temperature exceeds 1000 ° C, the crystal grains are coarsened, which is not preferable. Is required to be kept in the above temperature range for at least 30 minutes, but it is not preferable because the crystal grains become coarser if it exceeds 5 hours. After the heat treatment at 900 ° C. to 1000 ° C. for 30 minutes to 5 hours, it is cooled with water. . Further, the preferable liquefaction treatment temperature is 920 ° C to 980 ° C.

In the age hardening treatment, if the temperature is lower than 370 ° C, the precipitation hardening is insufficient and the required hardness cannot be obtained, and if it exceeds 480 ° C, overaging causes the required hardness to be not obtained. Further, if the holding time in the temperature range is less than 30 minutes, the precipitation hardening is insufficient,
370 ℃ -480 ℃ × 30
Processing time is from minutes to 20 hours.

Further, the Rockwell C hardness of the obtained copper alloy is limited to 20 or more and the electrical conductivity (JIS H 0505) is limited to 40% or more because it is unsuitable as an electrode material for resistance welding below the respective lower limits. .

EFFECTS OF THE INVENTION As described above, the present invention is characterized by performing cold working after hot working and before solution treatment.

However, it is generally said that if cold working is performed before the high temperature treatment, the growth rate of crystal grains is significantly increased by the subsequent heat treatment. The grains are extremely fine and uniform.

Further, since the solution treatment is performed after the cold working, the strain or the like applied by the cold working is released, and after the aging treatment is performed and the hardening is performed, an extremely stable strength can be obtained.

Since the production method according to the present invention does not generate coarse crystals at all, there is an advantage that the restriction on the solution temperature is greatly relaxed.

Example 1 A 250 mm square ingot was melted in the air so as to have the following composition.

Be0.42wt%, Co1.03%, Ni0.95%, Mg0.02wt%, balance Cu, and then hot forging at 600 ° C to 850 ° C to form a 60 mm diameter.

Furthermore, the surface reduction rate was 22% and cold working was performed to obtain a diameter of 53 mm.

After various solution treatments of water cooling at 880 to 1020 ° C for 2 hours, aging treatment at 425 ° C for 3 hours was performed.

The Rockwell C hardness of each of the obtained electrode materials, the electrical conductivity, and the state of coarse particles on the material surface were measured and observed, and the results are shown in Table 1 together with the solution treatment temperature.

As is clear from Table 1, the electrode material produced by the method of the present invention has a slightly higher electric resistance with an increase in the solution temperature, that is, the conductivity decreases, but the hardness increases and a wear-resistant factory is used. It turns out to be remarkable.

By the way, when the sectional structure of the electrode material at the solution treatment temperature of 1000 ° C. is shown, as shown in FIG. 1, no coarse crystal grains are found in the vicinity of the surface of the electrode material according to the present invention which has been cold worked. On the other hand, as shown in FIG. 2, it is apparent that a large number of coarse crystal grains (A) are generated near the cross section of the electrode material by the conventional method.

[Brief description of drawings]

FIG. 1 is a sectional structure diagram of an electrode material according to the method of the present invention, and FIG. 2 is a sectional structure diagram of an electrode material according to a conventional method. A: Coarse crystal grains

Claims (1)

[Claims] 1. Be 0.2 wt% to 0.8 wt%, Co 0.5 wt% to 1.5 wt
%, Ni 0.5 wt% to 1.5 wt%, Mg 0.0005 wt% to 0.1 wt% Alloy containing residual Cu and unavoidable impurities is hot-worked at 600 ℃ ~ 1000 ℃, then 5% reduction in area ~ 50% cold working, further solution heat treatment at 900 ℃ ~ 1000 ℃ for 30 minutes ~ 5 hours, then aging at 370 ℃ ~ 480 ℃ for 30 minutes ~ 20 hours, Rockwell A method for producing a copper alloy for a resistance welding electrode, which comprises obtaining a copper alloy having a C hardness of 20 or more, an electrical conductivity of 40% or more, and a small crystal grain.