JPS62110872A - Butt welding method for steel plate - Google Patents

Abstract

PURPOSE:To improve the performance of a weld zone, and also to reduce the welding electric power and the use quantity of a welding material by butting each end part of a steel plate, executing its tack welding by a laser welding, and thereafter, executing its regular welding from both the surface and the reverse side. CONSTITUTION:As for a groove shape of base materials 1, 2 it is desirable that both a surface side groove angle alpha and a reverse side groove angle betabecome a range of 50-90 deg.. Also, surface side groove depth (a), a reverse side groove depth (c), and a butt surface thickness (b) are set so as to become almost equal to each other. That is, they are set so as to become 30-40% of a plate thickness. With respect to the groove of such a shape, tack welding is executed by a laser welding from the surface side. Thereafter, with respect to the side to which the tack welding has been executed, regular welding is started from the opposite side. In this way, a good weld junction part can be obtained.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method of butt welding steel plates or butt welding for manufacturing steel pipes from steel plates, and particularly a butt welding method in which temporary welding is performed in advance and then main welding is performed. It is about the method.

BACKGROUND OF THE INVENTION Conventionally, when butt welding thick steel plates or large steel plates or manufacturing steel pipes from thick steel plates, main welding is often performed after preliminary welding. In this case, manual welding, CO2 gas shield welding, etc. are used for plate welding, and submerged arc welding, etc. are often used for six-piece welding, so the welding methods for tack welding and actual welding are usually different. be.

By the way, the welded part formed by tack welding is different from the actual welding method as mentioned above, so its properties are different from the welded part by regular welding, and for tack welding, a welding method that is easy to work with is selected. Usually, performance is not considered important, so welds made by plate welding are often inferior to welds made by regular welding in terms of properties. Therefore, in the actual welding,
Generally, it is necessary to completely melt the plate weld.

Problems to be Solved by the Invention As mentioned above, when performing main welding after tack welding in butt welding of steel plates, it is necessary to completely melt the tack welded part during main welding. There was a problem like this. In other words, after tack welding, it is normal to first perform main welding from the side opposite to the tack welding side, and then perform main welding from the same side as the tack welding side. Even in actual welding, it is necessary to weld to a depth that reaches the tack welding part, but since the penetration depth is shallow in manual welding and CO2 gas shield welding that are conventionally used for tack welding, it is necessary to weld to a depth that reaches the tack welding part. On the other hand, in the main welding from the opposite side, it is necessary to deepen the penetration accordingly, which means that a large amount of welding power and welding material is used in the main welding from that side, and the performance of the welded part decreases due to the increase in heat input. The problem is getting worse. Also, manual welding and CO2
When plate welding is done by gas shield welding, a large amount of excess metal is generated, and usually the excess metal has a volume comparable to the amount of penetration, but when the main welding is performed from the same side as the tack welding, the excess metal is completely removed. Since it has to be melted, the heat input must be increased in the extra wall part even in the main welding from that side, so a large amount of welding power and welding material must be used, and the increase in heat input requires a large amount of heat input. There was a problem that caused deterioration of weld performance.

Among the above-mentioned problems, to deal with the latter problem of excess thickness during tack welding, it is possible to apply a method of removing only the excess thickness using a grinder, etc. after tack welding. Removal of the parts requires a large number of man-hours, which increases costs and significantly reduces overall work efficiency. Therefore, such means do not provide a fundamental solution.

This invention was made against the background of the above-mentioned circumstances, and in the butt welding of steel plates, it is possible to deepen the penetration of tack welding and at the same time reduce the generation of excess metal during tack welding, thereby improving the The purpose is to reduce the heat input during welding, thereby reducing the consumption of welding power and welding material during main welding, reducing costs, and improving the performance of the welded part. It is.

Means for Solving the Problems The butt welding method of the present invention is a butt welding method for steel plates in which the ends of the steel plates are brought together and tack welded, and then main welding is performed from both the front and back sides. It is characterized by being performed by laser welding.

Function: In the method of the present invention, laser welding is applied to tack welding as described above. Laser has extremely high energy density, so if you perform tack welding with laser welding,
The penetration is extremely deep, and there is no excess material at all. Therefore, in the first stage of main welding after tack welding (main welding from the opposite side to the tack welding side), the penetration is made to reach a depth that reaches the plate weld part (the penetration part by tack welding). The depth does not need to be as deep as in the conventional case, and the second stage of main welding (main welding from the same side as the tack welding side)
This eliminates the need for heat input, which was conventionally required to melt the excess metal due to tack welding. As a result, the heat input in both the first and second stages of main welding is lower than before, which reduces the consumption of welding power and welding material, and prevents deterioration in weld performance due to increased heat input. can.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A to 1D show examples of butt welding steel pipes using an X-shaped groove using the method of the present invention.

Figure 1 (A) shows the butt groove shape of the base material 1.2 before welding, and it is desirable that both the front side groove angle α and the back side groove angle β be within the range of 50 to 90'. , and the front side groove depth a, the back side groove depth C1, and the butt surface thickness b are determined so that they are approximately equal, that is, a, b, and c are each 30 to 40% of the main plate thickness. This is desirable.

In the method of the present invention, for example, for a groove having the above-mentioned shape, tack welding is first performed by laser welding from the front side as shown in FIG. Form part 3. As mentioned above, the temporary attachment portion 3 formed by laser welding has a large penetration depth, and no excess thickness is generated at all. In addition, this plate welding is
The entire length of the part to be welded may be continuously welded, or
Alternatively, the welding may be performed intermittently as long as the welding has sufficient strength to maintain the groove shape until the main welding is performed.

Next, as shown in FIG. 1C, a first stage main welding by submerged arc welding or the like is performed from the side opposite to the side where the tack welding was performed to form the welded part 4. This first
In the staged main welding, it is necessary that the welded portion 4 has a penetration depth such that at least the bottom overlaps the welded portion 3 of the previously performed plate welding. In other words, if the penetration depth is such that the welded part 4 of the first stage main welding does not overlap with the penetrated part 3 of the tack welding, the air in the remaining part of the melt will be absorbed by the welding heat, as shown in Fig. 2, for example. This is because the bubbles 6 may be formed in the welded portion 4 by the first stage main welding due to the expansion, resulting in a welding defect. As mentioned above, the penetration depth of the penetration part 3 due to tack welding is much deeper than that when tack welding is performed by conventional CO2 gas shield welding, etc. The penetration depth required to overlap the welded portion 4 with the tack welding reservoir 3 is much smaller than in the past, and therefore the heat input can also be less than in the past.

Thereafter, as shown in FIG. 1 (D>), a second stage main welding is performed by submerged arc welding or the like from the same side as the tack welding to form a welded part 5. During welding, the weld 5 overlaps the weld 4 of the first stage main welding, that is, the weld 3 of the tack weld is completely melted and the weld matches the weld 4 of the first stage main weld. Here, since there is no excess metal at all in the penetration part 3 of the tack welding, there is no need for heat input to melt the excess metal as in the past, and the amount of heat input is much smaller than in the past. be able to.

The reason why it is desirable to set the front side groove angle α and the back side groove angle β to 50 to 90° as described above is as follows. In other words, if each groove angle is made smaller than 50', part of the arc will occur on the sides of the groove during main welding at each stage, resulting in shallow penetration even under the same welding conditions, making it difficult to achieve the required penetration. The welding heat input required to obtain this amount becomes large. Conversely, if each groove angle is set to a large angle exceeding 90°, the cross-sectional area of the groove becomes large, and more weld metal is required to fill it, resulting in an increase in welding heat input.

The reason why it is desirable to make the groove dimensions a, b, and c almost equal is to make the welding heat input approximately equal in the first stage main welding and the second stage main welding, so that the performance of the welded part is uniform. This is for the purpose of

Example plate thickness 12.7. When butt welding the steel plates with an X-shaped groove, laser welding was used as tack welding according to the method of the present invention, and the welding was performed under the conditions shown in the column of "Method of the present invention" in Table 1. For comparison, steel plates of the same thickness were welded under the conditions shown in the "Conventional Method" column of Table 1 using conventional CO2 gas shield welding as tack welding. In addition, in the method of the present invention and the conventional method, the first stage and the second stage
The submerged arc welding method was used for all the main welding steps. The groove shape and penetration shape in the method of the present invention are shown in FIGS. 3(A), (B), and (C), and the groove shape and penetration shape in the conventional method are shown in FIG. ), (
Shown in C).

Table 1'-10- In the case of plate welding by conventional CO2 gas shield welding, the penetration depth of the plate weld pool 3 is only about 2 sides, as shown in Fig. 4 (A>), and The extra thickness was about 2 mm.Therefore, in the first stage main welding, as shown in Fig. 4(B), in order to sufficiently align the welded part 4 with the tack welding penetration part 3, it was necessary to ~ 4 It was necessary to insert the weld into the weld.In addition, in the second stage main welding, as shown in Figure 4 (C), in order to sufficiently match the weld part 4 of the first stage main welding, it was necessary to insert the plate weld. It was often necessary to melt more than 4# including the excess metal.

On the other hand, in the case of the method of the present invention, the depth of the penetration part 3 of the tack welding by laser welding is about 3 mm, as shown in Fig. 3 (A> In (B)), the penetration of the welded part 4 was sufficient at 2 to 3#.In addition, since no excess metal was generated during tack welding, the second stage main welding (Fig. 3 (C)) was also carried out. By welding the welded part 5 by 3 to 4 degrees, it was possible to sufficiently match the welded part 4 of the first stage main welding.

= 11- As described above, in the method of the embodiment of the present invention, the conventional CO
Compared to the conventional method using 2-gas shield welding for tack welding, penetration is small in both the first and second stages of main welding, so the welding heat input for main welding is lower than that of the first stage. It was possible to reduce this by about 10% in the second stage, and by about 12% in the second stage.

Effects of the Invention As is clear from the above explanation, according to the butt welding method of the present invention, the welding heat input during main welding after plate welding can be significantly reduced compared to the conventional method, and therefore the amount of welding power and welding material used can be reduced. It is possible to reduce the cost compared to the conventional method, and also to improve the performance of the welded part by reducing the welding heat input.

[Brief explanation of drawings]

FIGS. 1(A) to (D> are schematic diagrams showing stepwise groove shapes and penetration shapes in the butt welding method of the present invention,
Fig. 2 is a schematic diagram showing the defect occurrence situation when the weld penetration is too shallow in the actual welding, and Fig. 3 (A) to (C) show the groove shape and the weld penetration shape in the embodiment of this invention. FIGS. 4(A) to 4(C) are schematic diagrams showing the groove shape and penetration shape in a stepwise manner in the conventional method. 1.2... steel plate, 3... penetration part of welding with plate,
4... Welded part of the first stage main welding, 5... Welded part of the second stage main welded.

Claims (1)

[Scope of Claims] A steel plate butt welding method in which the ends of the steel plates are brought together and tack welded, and then main welding is performed from both the front and back sides, characterized in that the tack welding is performed by laser welding. butt welding method.