JPS63149082A - Butt welding method - Google Patents

Abstract

PURPOSE:To prevent the defective joining caused by the unevenness in heat input and to obtain a good joining by specifically dividing in the plate width direction the pressure electrode electrifying the end face of a thin steel plate by pressing it and welding it by making the pressure of the electrode at both side parts larger than that of the center part. CONSTITUTION:In the case of butt-welding the end face of a thin steel plate 2 each other, a pressure electrode is divided into >=three divisions in the plate width direction and the pressure by the pressure electrodes 1', 1' located at both side parts of the end face of the steel plate 2 is made larger by comparing it with the pressure by the pressure electrode 1'' of the center part. The rotary deformation of both side parts of the end face of a thin steel plate 2 while under butt welding is thus prevented and no gap is made to cause on the corresponding part. Consequently a good welding is performed by eliminating the lack of the heat input at both side parts of the plate end face.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of butt welding end faces of thin steel plates together.

(Conventional technology) For example, as a method for welding thin steel plates with high efficiency and high precision,
In recent years, butt welding has been widely adopted in place of Franche butt welding.

This butt welding method is as shown in Figure 3 (a) and (b).
A Flfl plate 2, which is a material to be welded, is held between electrodes 1.1 which are arranged oppositely and which also serve as a pressurizing device (hereinafter referred to as "pressure electrodes"), and a large current is applied while pressing these together. This is a type of pressure welding method that attempts to join the end faces of the thin steel plates 2 together in an extremely short time.

(Problems to be Solved by the Invention) However, when butt welding of thin steel plates and the like is performed by the above-mentioned butt welding method, there is a problem in that uneven heat input tends to occur in the width direction of the butt surfaces.

That is, heat input tends to be insufficient at both sides of the plate end face, and conversely, heat input tends to be excessive at positions slightly inward from both sides of the plate end face. In particular, if this tendency is remarkable, melting will drop or insufficient absorption will occur at positions where there is excessive heat input, as shown in FIG. 3 in FIG. 4 indicates a defective joint due to excessive heat input. On the other hand, if the heat input is lowered to prevent this phenomenon, there will be insufficient heat input (cold welding) on both sides of the plate end face, resulting in poor bonding on both sides of the plate end face.

Can the present invention solve these problems? ? This is intended to provide a j-contact method, and was established based on findings based on research and experiments by the present inventors, which will be described later.

(Means for Solving the Problems) First, the causes of the above-mentioned conventional problems will be explained.

In other words, the inventors investigated the mechanical and electrical behavior of the causes of uneven heat input through numerical analysis using the finite element method, etc., and also conducted experiments, and found that the conventional problem is as follows. It turned out that this was due to the cause.

In other words, during butt welding of thin steel plates, only the areas near the butt surfaces of the thin steel plates are rapidly heated. Due to the rotational deformation, the two sides of the end face of the plate are not brought into sufficient contact with each other, and a non-contact portion is formed at this portion.

However, if a large current continues to flow in this state, the current will concentrate in a very local part of the abutting surface adjacent to the non-contact part, resulting in a rapid concentration of heat generation (a reference diagram is attached for reference). . Moreover, on the contrary, heat generation is insufficient on both sides of the plate end face.

For this reason, in the current concentration area slightly inward from both sides of the plate end face, melt drips or there is insufficient absorption, resulting in poor bonding, and on both sides of the plate end face, bonding failure occurs due to insufficient heat input. be.

Therefore, the present invention attempts to solve the problem by varying the pressing force of the pressurizing electrode in the sheet width direction, based on the clarification of the cause of the occurrence of joint failures during butt welding as described above.

That is, in the present invention, the pressure electrodes that apply pressure and current to the end faces of the thin Wfll plate to be welded are divided into three or more parts in the width direction of the plate, and the pressure applied by the pressure electrodes located on both sides is applied to the center part. By increasing the pressure applied by the piezo electrode, it is attempted to eliminate the bonding failure caused by the uneven heat input described above.

That is, in the present invention, the pressurizing electrode 1 is divided into three or more parts in the plate width direction, as shown in FIGS.
The pressure applied by the pressure electrodes 1' and l' located on both sides of the end face of the thin steel plate 2 during butt welding is thicker than the pressure applied by the pressure electrode 1'' in the center.
This effectively prevents rotational deformation on both sides of the end face and prevents gaps from forming in these areas.

This eliminates the lack of heat input at the side portions of the plate end faces, and enables good welding of these portions as well.

When applying the method of the present invention, pressurizing electrodes 1' on both sides
, 1' can be made smaller, or the tip of the electrode can be made to protrude toward the plate end surface from the tip of the pressurizing electrode 1'' in the center as shown in Figure 1 (a), thereby reducing the increase in the pressurizing force. The same effect can be obtained.

(Example) The results of implementing the method of the present invention will be explained below.

First, the composition, dimensions, and mechanical properties of the sample material used in this example are shown in Table 1 below, and the welding conditions when butt welding was performed using this test material by the method of the present invention are shown below. Shown in Table 2.

Table 1 Table 2 1st place "f" [Separately, Table 3 below shows the results of butt welding using the sample materials shown in Table 1 and the welding conditions shown in Table 2 by the method of the present invention. Shown below.

The following matters were clarified from Table 3 above.

■ The cracking rate when applying conventional single pressure is 10% (1 patient
).

■ The wider the width of the pressure electrode at the end, the less effective it becomes (floor 4).
and 5).

(2) The effect becomes noticeable when the pressing force of the pressing electrode at the end is 1.5 times or more that of the electrode at the center (Arashi 2.3 and Ichi 6-9).

■ The 4-division method has the same improvement effect as the 3-division method (Magnetic 11).

■ If the length of the electrode at the end is extended, there is an improvement effect even under the same pressing force ((7 and 10)).

■ Based on the above results, increase the pressure force of the pressure electrode at the end.
The narrower the width (and the longer the protrusion length), the better the improvement effect will be, but since there are problems with electrode slippage and plate buckling, it is necessary to select conditions that will prevent this from occurring.

(Effects of the Invention) As explained above, the present invention provides a method for butt welding the end faces of three steel plates to each other, in which a pressure electrode for pressurizing and energizing the end face of a thin steel plate to be welded is divided into three or more parts in the width direction of the plate. Since the pressure electrodes located on both sides of the sheet are divided into two parts and the pressure applied by the pressure electrodes located on both sides is made larger than the pressure applied by the pressure electrode in the center during welding, the uneven heat input that conventionally occurs on both sides of the plate end face is eliminated. It is possible to prevent bonding defects caused by , and to achieve good bonding.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are schematic explanatory diagrams of the method of the present invention, Figures 2 and 4 are diagrams illustrating problems with the conventional method, and Figure 3 is an explanatory diagram of the butt welding method. . ■ is a pressure electrode, and 2 is a thin steel plate. Figure 3 Figure 4

Claims (1)

[Claims] (1) In a method of butt welding the end faces of thin steel plates together, a pressure electrode that applies pressure to the end face of the thin steel plate to be welded is divided into three or more parts in the width direction of the plate, and the pressure electrodes are placed on both sides. A butt welding method characterized by welding by making the pressure applied by an electrode greater than the pressure applied by a pressure electrode in the center.