JPH02108474A - Method for shaping copper alloy electrode tips for spot welding - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention A0 Object of the Invention (1) Industrial Application Field The present invention relates to a copper alloy electrode tip for spot welding, particularly a copper alloy electrode tip having a truncated conical tip, used for spot welding of mild steel plates. This invention relates to a method for shaping an electrode tip.

(2) Prior Art Conventionally, this type of electrode tip has been shaped by grinding the end face and tapered face of the truncated conical tip at approximately every 1000 points.

(3) Problems to be Solved by the Invention Normally, when spot welding mild steel plates using an electrode tip, the nugget diameter tends to increase in the range of 1 to 50 welds. This is because the electrode tip is softer than a mild steel plate, and further softens as the temperature rises during welding, and at the same time, the tip is crushed by the pressure applied.

On the other hand, after 50 points, a protrusion made of Fe--Cu alloy is formed and grows approximately at the center of the end face of the tip of the electrode tip due to the adhesion of Fe evaporated from the surface of the mild steel plate. This alloy has higher strength and a higher melting point than the copper alloy that makes up the electrode tip, so it does not deform even under high temperature pressure during welding work, so it has the ability to keep the nugget diameter approximately constant. It is possible to obtain an appropriate current density and perform stable welding. In this case, once the protrusion grows to a predetermined size, it does not grow any further and is consumed with each welding process.
This is compensated for by the diffusion of , so the size of the protrusion remains approximately constant.

Further, as the number of dots approaches 1000, a thick annular Cu coarse particle layer around the protrusion causes its outer periphery to protrude from the tapered surface due to softening recrystallization of the copper alloy due to high-temperature heating and growth of its crystals. As the nugget diameter increases and the current density decreases, welding defects are more likely to occur.

Therefore, conventionally, shaping work is performed every 1000 dots as described above, but according to this method, the end face of the tip of the electrode tip is also ground, so the protrusions that bring about good results in welding are removed. When welding is performed using the electrode tip after shaping, the nugget diameter increases in the range of 1001 to 1050 dots as in the range of 1 to 50 dots, and therefore However, there is a problem in that the ratio of the number of effective dots contributing to proper welding is low, resulting in poor work efficiency.

In addition, since the end face and tapered surface of the tip are ground for each shaping operation, the amount of grinding required for the total number of points is large, resulting in an increase in the amount of electrode tip wear, which is uneconomical, and furthermore, the shaping operation time is also reduced. There is also the problem of length.

An object of the present invention is to provide the above-mentioned shaping method that can solve the above-mentioned problems.

B0 Structure of the Invention (1) Means for Solving the Problems The present invention is a method for shaping a copper alloy electrode tip having a truncated conical tip used in spot welding of mild steel plates. When an annular Cu coarse particle layer grows around a protrusion made of a Cu-Fe alloy formed on the end face of the truncated conical tip so that its outer peripheral portion extends from the tapered surface of the truncated conical tip. , a partial shaping operation is performed in which the tapered surface is subjected to a grinding process to remove the outer periphery of the annular Cu coarsened particle layer, and then the disk-shaped Cu coarsened particle layer has its outer periphery protruding from the tapered surface. When the process has grown past the back surface of the protrusion, an overall shaping operation is performed in which the end face and tapered surface of the truncated conical tip are ground to remove the disk-like coarsened Cu particle layer together with the protrusion. Features.

(2) Effect In the process of shaping the electrode tip, a protrusion made of Cu-Fe alloy formed on the end face of the tip of the electrode tip remains, so when welding is performed using the shaped electrode tip, the first welding point is Proper welding is performed from

In the overall shaping work, the disk-shaped Cu coarse particle layer that has grown past the back surface of the protrusion is removed together with the protrusion, thereby avoiding the protrusion from falling off due to the breakage of the fragile layer, and therefore from causing welding defects. .

When welding is performed using the electrode tip after the partial shaping operation, the nugget diameter does not increase, so the ratio of the number of effective dots to the total number of dots from the start of welding to the entire shaping operation becomes high.

That is, if the number of dots from the start of welding to the partial shaping work is a, and the number of dots from the partial shaping work to the whole shaping work is b,
The ratio A1 of the effective number of hits (a+b)-50 to the total number of hits a+b is a+b.

On the other hand, in the case of the conventional example, since the total number of hits is the same as the number of hits a in the present invention, the ratio A2 of the effective number of hits a-50 to the total number of hits a is as follows.

In this case, since a+b>a, the ratio relationship is A
I>Az.

(3) Embodiment FIG. 1 shows an electrode tip 1 made of a copper alloy, and the electrode tip 1 has a truncated conical tip 2.

FIG. 2 shows a shaping device 3 used for shaping a pair of electrode tips 1 attached to a spot welding machine.
□, and a power section 5 that transmits power to both of the grinding sections 41°4□.

Grinding part for partial shaping4. is constructed as follows.

That is, a pair of bearing tubes 8.
．． 8. are mounted, and a cylindrical grinding cutter holder 9 is rotatably fitted into the bearing tubes 88 and 82. The holder 9 is the third one. The cylindrical body 10 as shown in FIG.
and a pair of annular lids 111 polymerized and bonded to both end faces thereof.
．． It consists of 11g. The cylindrical body lO has tapered holes 12. which are open at both ends thereof. ．． 12g, each tapered hole 12+, 12
A long hole 13 that crosses g. ．． 13g, and a gear portion 14 protruding from the middle portion of the outer peripheral surface. Each tapered hole 12, . 1
2□ has an inclination between the taper surface a of the tip portion 2 of the electrode tip 1 and the path.

As clearly shown in FIG. 5, the grinding cutter 15+ has a pair of grinding blades 16 that are inclined to follow the tapered surface a of the electrode tip 1, and between the ends of both grinding blades 16 there are four parts 17. It is formed. This recess 17 can prevent the end face of the electrode tip 1 from being ground. Each grinding cutter 15. are each long hole 131. of the holder 9. '13g, and each grinding blade 16 slightly protrudes from the opening edge of each elongated hole 13+, x3z.

Each cover body 11. , 11□.

A re-grinding cutter 15 is attached to the device housing 6. Electrode tip insertion hole facing 18. ．． 1B is formed.

The grinding section 4□ for whole shaping is the grinding section 4□ for partial shaping except for the cutter for grinding. The structure is the same as that of the 2000, and therefore the same parts are given the same reference numerals.

As clearly shown in FIG. 6, the grinding cutter 15□ used for overall shaping includes a pair of first grinding blades 19 that are inclined to follow the tapered surface a of the electrode tip l, and both grinding blades 19. It has a pair of horizontal second grinding blades 192 that are located between the ends of the electrode tip l and follow the end surface of the electrode tip l.

The power unit 5 includes an electric motor (not shown), and a drive gear 21 attached to a drive shaft 20 of the electric motor, and a first intermediate gear 22 .
meshes with the intermediate gear 221, and the overall shaping grinding section 4.
The gear portions 14 of the two mesh with each other.

Further, a second intermediate gear 22□ meshes with the gear portion 14, and the gear portion 14 of the grinding portion 41 for partial shaping is engaged with the intermediate gear 22□.
mesh together. When the electric motor is thereby driven, the re-grinding cutter 151.15□ rotates together with both holders 9 via each gear 21, 221.22□ and both gear parts 14.

Next, the shaping operation of the electrode tip l will be explained.

FIG. 7(a) shows the shape of the tip of the electrode tip 1 (only one is shown in the figure) up to 50 dots after the start of welding. In this case, the vicinity of the end face of the tip part 2 is softer than the mild steel plate, and is further softened by the temperature rise during welding, and is crushed by the pressure at the same time, and as a result, the nugget diameter tends to increase. be. The crushed portion C contains coarsened CU particles due to softening and recrystallization caused by high-temperature heating.

FIG. 7(b) shows the shape of the tip of the electrode tip 1 up to 1000 dots after the start of welding. After the 50th point, a protrusion d made of Fe--CU gold alloy is formed and grows approximately at the center of the end face of the tip due to the adhesion of Fe evaporated from the surface of the mild steel plate. This alloy has higher strength and melting point than the copper alloy that makes up the electrode tip l, so
Since it does not deform even under high-temperature heating during welding work, it has the function of keeping the nugget diameter approximately constant, thereby making it possible to obtain an appropriate current density and perform stable welding. in this case,
Once the protrusion d has grown to a predetermined size, it will not grow any further and will be consumed with each welding process, but the amount of consumption will be compensated for by the diffusion of Fe from the soft iron plate, so the size of the protrusion d will remain approximately constant. Become.

When the 1000 dots approach, a thick annular Cu coarse grain layer e is formed around the protrusion d due to softening recrystallization due to high-temperature heating of the copper alloy and growth of its crystals, and its outer periphery f overhangs the tapered surface a. As the layer e comes into contact with the mild steel plate, the nugget diameter increases, the current density decreases, and welding defects are more likely to occur.

Therefore, when 1000 dots are reached, a partial shaping operation is performed using the shaping device 3. That is, as shown by solid lines in FIG.
．． are inserted into the re-insertion holes 181 and 182 respectively, and each tapered surface a is ground by each rotating grinding cutter 15I as shown by the line 1I in FIG. The outer periphery f of the particle layer e is removed.

As a result, the distal end portion 2 is partially shaped as shown in FIG. 7(C).

In the partial shaping work, the protrusion d formed on the end face of the tip portion 2 remains, so when welding is performed using the shaped electrode chimble l, proper welding must be performed from the 1001st welding point. Can be done.

Next, when the welding operation is continued, an annular Cu coarsened particle layer e grows near the 2000 welding point as described above, so a partial shaping operation is performed in the same manner as described above.

After that, as we continued welding work, we reached the 7th point near 3000 dots
As shown in Figure (d), the disk-shaped coarsened Cu particle layer g makes its outer peripheral portion protrude from the tapered surface a and grows past the back surface of the protrusion d, making it easier for the protrusion d to fall off.

Therefore, when 3000 dots are reached, the entire shaping operation is performed using the shaping device 3. That is, as shown by the chain lines in FIG.
7 (d) line! , each tapered surface a is cut by each rotating first grinding blade 191 as shown in FIG. 7(d). As shown in , each end face is similarly ground by each rotating second grinding blade 19□ to remove the disk-shaped Cu coarsened particle layer g and the protrusion d.

As a result, the tip portion 2 is shaped as shown in FIG. 7(e).

In the overall shaping operation, the disk-shaped coarse Cu particle layer g that has grown past the back surface of the protrusion d is removed, so that the protrusion d falls off due to the breakage of the fragile layer g, thereby avoiding welding defects. Can be done.

When welding is performed using the electrode tip l after the partial shaping operation, the nugget diameter does not increase, so the ratio of the number of effective dots to the total number of dots from the start of welding to the entire shaping operation increases.

That is, since the number of dots from the start of welding to the two partial shaping operations is 2000 dots, and the number of dots from the partial shaping operation to the entire shaping operation is 1000 dots, the effective number of dots is 3000-50 for the total number of dots of 3000 dots. The ratio A of =2950 is 98%.

On the other hand, in the case of the conventional example, since the total number of RBIs is 1000 RBIs, the effective number of RBIs is 100 for the total number of RBIs of 1000 RBIs.
The ratio At of 0-50=950 is 95%.

Therefore, the relationship A+>Az holds true.

The partial shaping work may be performed every 500 dots, and the overall shaping work may be carried out after 4000 dots, 5000 dots, or more dots have been reached depending on the diameter of the nugget.

C9 Effects of the Invention According to the present invention, when shaping the tip of a copper alloy electrode tip for a mild steel plate, a partial shaping operation is performed before the entire shaping operation,
In this partial shaping work, Cu-F, which provides good welding results, is used.
Since the protrusions made of e-alloy remain, it is possible to increase the ratio of the number of effective dots contributing to proper welding to the total number of dots from the start of welding to the overall shaping work, thereby improving work efficiency.

Further, in the overall shaping operation, the disk-shaped Cu coarse particle layer that has grown past the back side of the protrusion is removed together with the protrusion, so it is possible to avoid welding defects due to the protrusion falling off.

Furthermore, in the partial shaping operation, only the tapered surface of the tip of the electrode tip is ground, and in the whole shaping operation, the end surface and the tapered surface of the tip of the electrode tip are ground. It is possible to reduce the amount of grinding for all points, thereby reducing the amount of wear of the electrode tip and improving economic efficiency. Moreover, the time required for shaping the entire number of dots can be shortened.

[Brief explanation of drawings]

Fig. 1 is a front view of the main part of the electrode tip, Fig. 2 is a longitudinal sectional front view of the main part of the shaping device, and Fig. 3 is a longitudinal sectional front view of the grinding cutter holder, which corresponds to the sectional view taken along the line ■-■ in Fig. 4. Fig. 4 is a broken view of the main part in Fig. 3 ■ arrow direction, Fig. 5 is a perspective view of a grinding cutter for partial shaping, Fig. 6 is a perspective view of a grinding cutter for whole shaping, and Fig. 7 is a welding cutter. FIG. 6 is an explanatory diagram showing changes in shape of the tip of the electrode tip due to work and shaping work. a...Tapered surface, b...End face, e...Annular Cu coarse particle layer, r...Outer periphery, g...Disc-shaped Cu coarse particle layer, 1...Electrode chip, 2...Patent applicant for truncated conical tip

Claims (1)

[Claims] A method for shaping a copper alloy electrode tip having a truncated conical tip used for spot welding of mild steel plates, the method comprising Cu-F formed on the end face of the truncated conical tip during welding work.
When an annular Cu coarse particle layer has grown around the protrusion made of e-alloy in such a way that its outer periphery protrudes from the tapered surface of the truncated conical tip, the tapered surface is ground to form the annular shape. A partial shaping operation is performed to remove the outer periphery of the Cu coarsened particle layer, and then the disk-shaped Cu coarsened particle layer is
When the outer periphery thereof is made to protrude from the tapered surface and has grown past the back surface of the protrusion, the end face and tapered surface of the truncated conical tip are ground, and together with the protrusion, the disk-shaped coarsened Cu particles are grown. A method for shaping a copper alloy electrode tip for spot welding, which comprises performing an entire shaping operation to remove a layer.