JPS63149085A - Butt welding method - Google Patents

Abstract

PURPOSE:To prevent the defective joining caused by the unevenness in heat input by welding the vicinity of the butt part on the end face of the thin steel plate to be welded with restraining both sides thereof or pressurizing from both sides in the case of performing a butt welding of the end face of the thin steel plate can other. CONSTITUTION:In the case of butt-welding a thin steel plate 2 each other, the high strength heat resistant insulation body 5 of a ceramics, etc., for instance, is used at the abutting side to the thin steel plate 2 in order to disturb no route of a main current for electric insulation and the strength of a jig 4 is reinforced by a steel 6. A lubricant 7 is coated on the surface of the high strength heat resistant insulation body 5. The deformation expanding in the plate width direction at the vicinity of the part abutting the end faces of the thin steel plate 2 is blocked by its pressing or restraining by using the jig 4 in order to perform the pressurizing or restraining like this and the gap is eliminated.

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.

In this butt welding method, as shown in Figures 4(a) and 4(b), a thin steel plate 2, which is the material to be welded, is held between electrodes 1.1, which also function as a pressurizing device, and are butted together. This is a type of pressure welding method in which the end surfaces of the thin steel plates 2 are joined together in a short time by applying pressure and applying a large current.

(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 at a position where there is excessive heat input, as shown in FIG. 5, or insufficient offset will occur. 3 in Figure 5 indicates a defective joint due to excessive heat input.On the contrary, 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 surface, resulting in insufficient heat input on both sides of the plate end surface. will result in poor bonding.

The present invention aims to provide a butt welding method that can solve these problems, and is based on the research and research conducted by the present inventors, which will be described later.
It is established based on experiments (knowledge).

(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 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 surface.

For this reason, in the current concentration area slightly inward from both sides of the plate end face, melt drops 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. .

Therefore, in the present invention, based on the clarification of the cause of the occurrence of joint failure during butt welding as described above, the present invention attempts to solve the problem by pressurizing or restraining the end face of the thin steel plate from both sides during welding.

In other words, the present invention attempts to eliminate the joint failure caused by the uneven heat input by welding the vicinity of the end face abutting portion of the thin steel plate to be welded while applying pressure from both sides or restraining both sides. be.

In other words, in conventional butt welding, as schematically shown in FIG. 4, pressurization by the electrode 1 was performed only from the longitudinal direction of the thin steel plate 2, so the heating area at the end face butt part of the thin steel plate 2 The material expanded freely in the width direction of the plate, creating a non-contact area or a gap.

In contrast, the method of the present invention, as schematically shown in FIG. 1, prevents the expansion deformation in the width direction of the thin steel sheet 2 by applying pressure or restraining it in the vicinity of the end face abutting portion, thereby preventing the gap from disappearing. This is what we aim to do.

FIG. 2 is an illustrative drawing of a jig 4 for applying pressure or restraint used when applying the method of the present invention. In order not to disturb the path, for example, a high-strength heat-resistant insulator 5 such as ceramics may be used on the side that contacts the thin steel plate 2 to provide electrical insulation, and the strength of the jig body may be reinforced with steel 6 or the like. desirable. The one shown in FIG. 2 (a) is used by applying a lubricant 7 on the surface of the high-strength heat-resistant insulator 5, and the one shown in FIG. A roller is formed of an insulator 5.

In addition, in order to effectively butt weld thin steel plates 2 having different widths, and to eliminate the influence of uneven plate widths, which depend on the accuracy of processing and attachment to the electrode 1, the method of the present invention is used. In application, it is preferable to apply pressure rather than restraint.

(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 (Unit: Weight %) Table 2 Table 3 below shows the results of butt welding using the method of the present invention using the test materials shown in Table 1 under the welding conditions shown in Table 2. Shown below.

Table 3 Note 1) Cracking rate = (Σ crack length/width of electrode) x 100 From Table 3 above, the following became clear.

■ The cracking rate of the conventional method that does not restrain or apply pressure in the width direction of the plate is 10
% (Patient 1).

■ When the pressure width by the jig is set to 1/3 of the initial electrode spacing, the cracking rate decreases as the jig pressure increases (Numbers 2.3 and 10 to 13); Even if pressure is applied above the value, the effect is the same (patient 4.5 and Nl113
．． 14).

■ If the width of pressure applied by the jig is increased while keeping the jig pressure constant, the cracking rate will decrease as the latter increases (see 6 to 8).
and 15.16), but the effects are the same over a certain width. (Magnetic 8.9 and NIL 16.17).

■ From the above implementation results, if the width of pressure applied by the jig is set to be approximately 1/3 or more of the distance between the electrodes, and the pressure applied by the jig is increased within a range that does not cause buckling, the effect of reducing the cracking rate by the present invention will be significant. appear.

(Effects of the Invention) As explained above, the present invention provides a method for butt welding the end faces of thin steel plates to each other by applying pressure from both sides or restraining the vicinity of the butted end faces of the thin steel plates to be welded. Since welding is carried out while welding, it is possible to prevent joint failures caused by uneven heat input, which conventionally occurred on both sides of the plate end face, and to achieve a good joint.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of the method of the present invention, Figure 2 (a) and (b)
1 is a diagram illustrating a pressurizing or restraining jig used in the method of the present invention, FIGS. 3 and 5 are diagrams illustrating problems in the conventional method, and FIG. 4 is a diagram illustrating a butt welding method. 1 is an electrode, 2 is a thin steel plate, and 4 is a jig. Figure 1 Figure 3

Claims (1)

[Claims] (1) A butt welding method for butt welding the end faces of thin steel plates to each other, which is characterized in that the welding is performed while applying pressure from both sides or restraining both sides of the area near the abutted end faces of the thin steel plates to be welded. .