JPH0321275B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resistance welding method, and particularly to a resistance welding method suitable for preventing peeling of a plating layer when welding plated steel plates.

In seam welding of plated steel plates, the edges of the plated steel plates are overlapped, and the overlapped surfaces are pressed with a disk electrode while power is supplied to obtain a welded part. However, in the seam welds of such galvanized steel plates, the plating layer that comes into contact with the disc electrode temporarily melts due to resistance heat generation during welding, and is peeled off by picking up the disc electrode, exposing the iron base. The surface becomes uneven. In particular, for automotive fuel tanks, plated steel plates 1 and 2 are used as shown in Figures 1 and 2.
Seam welding is used as a joining method for the flange part, but the plating layers 3 and 4 peel off, exposing the base of the iron 5 and 6 in the welded part, and the surface becomes uneven, so it is difficult to use after welding. A general black paint treatment gives it a beautiful appearance and corrosion resistance.

However, in recent years, the mounting location of automobile fuel tanks has tended to move from inside the vehicle to outside the vehicle, under the rear floor, making it easy for water, mud, etc. to accumulate on the top surface of the fuel tank, which can cause rust, and seam welding Even if black paint is applied to the surface of the part, it is insufficient in cold regions, and corrosion tends to progress. Therefore, it is possible to repair the seam weld by applying a corrosion-resistant paint such as a chip-resistant material to the seam weld, or by coating the seam weld with a corrosion-resistant material such as solder. However, with these methods, it is difficult to repair both sides of the seam weld at the same time, and in particular, methods that coat with corrosion-resistant materials such as solder require countermeasures against fumes that occur, and treatment of flax that adheres to the surface of the weld after repair. As a result, there is a problem that the working environment and productivity deteriorate. In addition, methods of using a back bar and wire seam welding to prevent the plating layer from separating during welding are also used. However, although these methods are easy to operate on only one side, it is extremely difficult to simultaneously operate on both sides of a galvanized steel plate.

An object of the present invention is to provide a resistance welding method that can prevent the plating layer of the weld from peeling off and obtain a weld with excellent corrosion resistance.

The present invention focuses on the fact that projection welding in lap resistance welding causes less surface burn of the welded part and less peeling of the plating layer. However, if the plate is made of a thin sheet and is seam welded with a projection formed around the entire circumference of the flange of the fuel tank, the portion of the projection corresponding to the unwelded part is easily exposed to heat due to continuous energization and pressurization. In addition, not only a large current and high pressure are required, but also sufficient welding strength cannot be obtained.

The present invention forms a projection on one of the plated steel plates to be joined, interposes a conductive material in a concave portion of the projection, and has a size that prevents the electrode from coming into contact with the plating layer of the plated steel plate during welding. A joint is obtained by intensively supplying power from a conductive material.

Embodiments of the present invention will be described below with reference to the drawings.

In Fig. 3 and Fig. 4, the plated steel plate 7,
8 has plating layers 9A, 9B and 1 on both sides, respectively.
0A and 10B are formed, and these plated steel plates 7 and 8 are seam welded while being pressed by the rotation of a pair of electrode wheels 11 and 12. At this time,
One plated steel plate 8 is pre-installed with projection 1.
3 is formed. This project 13
is formed into a concave shape with a relatively gentle slope,
They are continuously provided along the welding direction during seam welding.

During seam welding, a conductive material 14 is interposed within the recess of this projection 13. As the conductive material 14, for example, a copper wire of about 1.0φ can be used. Here, when the conductive material 14 is interposed in the recess of the projection 13, it is necessary that it protrudes slightly outward from the recess. The conductive material 14 may be drawn into the recess of the projection 13 as the electrode wheels 11 and 12 rotate, or may be forcibly fed. In this state, when seam welding is performed with the conductive material 14 interposed between the electrode wheels 12 and the electrode wheels 12, electricity is supplied from the electrode wheels 11 and 12 through the conductive material, and a joint 15 is obtained.

That is, the conductive material 14 serves to increase the current density during seam welding by concentrating the power feeding points to form the joint 15, and to suppress the deformation of the projection 13 formed on the plated steel plate 8. In addition, by preventing the electrode ring 12 from directly contacting the plated steel plate 8 in the final stage of forming the joint portion 15 and eliminating a significant drop in current density, sufficient jointing can be achieved even with a relatively low current. You can gain strength. Therefore, during seam welding, a relatively low current and low pressure can be used, so even on the surface side of the plated steel plate 7, peeling of the plated layer surface is prevented and a substantially smooth surface can be obtained. .
After the conductive material 14 passes through the power supply point, it is detached from the concave portion of the projection 13 while in a red-hot state due to energization, so the detachment of the plating layer of the plated steel plate 8 on which the projection 13 is formed is extremely small. Moreover, the outer projection shape remains almost unchanged from before seam welding. Therefore, by the method of the above embodiment, a flange portion of an automobile fuel tank as shown in FIG. 5 can be obtained.

The present invention can be applied not only to welding the flange portion of a fuel tank as shown in FIG. 5, but also to welding the flange portion of a fuel tank shown in FIG. In this case, as shown in FIG. 7, when seam welding a flat plated steel plate 16 and a plated steel plate 17 having a step, a projection 18 is formed at the step of the plated steel plate 17 along the welding direction. Then, a conductive material (not shown) is interposed in the recessed portion of the projection 18. Furthermore, the present invention is also effective for projection joints made of extremely thin plates.
Generally, in the case of an extremely thin plate of 1 mm or less, even if a projection joint is formed, the projection is easily deformed by the pressure and heat during welding because it is an extremely thin plate, and it is difficult to form a joint. However, even in the case of such a projection joint, by interposing a conductive material in the recess of the projection, it is possible to easily obtain joint strength while avoiding deformation.

In the present invention, the shape of the projection is
When the shape of the joint is a ring, it is preferable to join a circumferentially continuous ring-shaped conductive material into the recess of the projection and take it out from the recess after welding.

Example Using a turn sheet with a thickness of 1 mm, the length is approximately 300 mm.
A long and narrow projection of mm was formed and seam welded using the method shown in Figures 3 and 4. The turn sheets used in the experiment had a thickness of 1.0 mm and two types of plating weights on both sides: 107 g/cm ³ and 145 g/cm ³ . The shape of the projection was approximately 4 mm in width and approximately 1 mm in height, and a copper wire with a diameter of 1.0 mm was used as the conductive material, and a flat electrode ring with a tip width of 10 mm was used. The welding conditions are: current value of approximately 14KA, pressure of approximately 400Kg, and speed of approximately 3.
The energization/deactivation cycle was 2-2 m/min.
As a result of the experiment, we were able to obtain a welded part with sufficient joint strength, and we were also able to confirm that the plating layer had a sufficient thickness (more than 30% of the original plating layer thickness) on both the upper and lower surfaces. Incidentally, by increasing the basis weight of the plating on the turn sheet, the remaining of the plating layer can be made more reliable.

As a comparative example, when seam welding was performed in the same manner as above without using a conductive material, sufficient joint strength could not be obtained even when the current value was increased to about 23 KA, and the groove of the projection showed abnormal deformation. ,
Furthermore, most of the plating layer had come off, and the appearance of the welded area was poor.

As described above, according to the present invention, the plating layer remains on both sides of the seam weld, one side is almost smooth, and the other side has little protrusion deformation and both sides are free from water, mud, etc. Since it does not adhere easily, corrosion does not progress easily.

[Brief explanation of the drawing]

FIG. 1 is a partially cross-sectional perspective view of a fuel tank obtained by conventional seam welding, FIG. 2 is an enlarged view of the main parts of FIG. 1, and FIG. 3 is a front view showing an example of the present invention. 4 is a side view of FIG. 3, FIG. 5 is a partially sectional perspective view of the fuel tank obtained by the present invention, and FIG. 6 is a perspective view of another example of the tank obtained by the present invention. FIG. 7 is an enlarged view of the main part of FIG. 7, 8...Plated steel plate, 9A, 9B, 10A,
10B... Plating layer, 11, 12... Electrode ring, 1
3... Progeexion, 14... Conductive material,
15... Joint part, 16, 17... Plated steel plate, 1
8...Projexion.

Claims (1)

[Claims] 1 In a method of resistance welding two plated steel plates by pressing them with a pair of electrodes, a projection is formed along the welding direction of one plated steel plate,
A resistance welding method characterized in that a conductive material of a size such that the electrode and the plating layer of the plated steel plate do not come into contact with each other during welding is interposed in the recess of the projection.