JPS6120665A - Preventive method of terminal crack in automatic one-side welding - Google Patents

Abstract

PURPOSE:To prevent surely the generation of a crack at the terminal of a joint by subjecting the terminal of the joint and the front side of tab plates formed with slits to one-side welding by preliminary continuous sealing welding and subjecting the unwelded part of the tab plates to heating prior to welding of the terminal. CONSTITUTION:The tab plates 3a, 3b provided with slits 4a, 4b are joined by welding to reinforcement of weld over a distance B from the rear end edges and thereafter the front edgesf are pressed to base metals 1a, 1b and both grooves 6a, 6b are welded to the reinforcement of weld. The rear edge C of the joint 2 and the front end edge of the joint part 5 are then subjected to continuous sealing welding by a distance A and thereafter the one-side welding of the joint 2 is started. The unwelded part near the central part of the joint part 5 is further heated to about 600 deg.C and the arc is shifted at the distance A from the terminal of the joint 2 to the part 5, by which the welding is ended. The one-side welding which can prevent surely the cracking at the terminal of the joint is thus made possible.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a method for preventing cracking at the end of a welded joint in one-sided automatic welding, which prevents the occurrence of cracking at the end of the joint when automatically welding two base materials on one side. [Prior art related to method] In general, single-sided automatic welding is widely adopted in order to streamline the construction of ships.

However, in this single-sided automatic welding, there is a problem that the terminal end rotational deformation of the base material forming the welded joint is likely to occur due to welding thermal stress, and cracks occur at the terminal end of the joint due to the rotational deformation.

Therefore, various methods have been considered in the past to prevent the occurrence of end cracks as described above, one of which is a method called the slit tab method, which reduces the displacement speed of the joint end due to rotational deformation. It seeks to alleviate
For example, a welded joint of two base materials is temporarily welded leaving a terminal end (usually about 1 m long), and a pair of slits are made on one side of the welding line parallel to the welding line of the joint at the edge of the terminal end. By firmly welding the edge of the one side of the tab plate on which the tab plate is formed, when the arc generated from the welding torch moves along the joint and reaches the tough plate during welding, , the heat generated by the arc is retained in both the slits to prevent thermal expansion of the entire tab plate, and the binding force of the tab plate on the joint end portion is not significantly weakened due to thermal expansion of the tab plate, and the joint end portion is prevented from thermally expanding. rotational deformation is suppressed and the occurrence of terminal cracks is prevented.

Note that when the end of the joint is tack welded, when the welding progresses and the arc reaches the end of the joint, the weld bead of the tack at the end is fused by the arc, and until then the tack is welded. The terminal end portion, which had been restrained by the weld bead, is released all at once, causing rapid rotational deformation in the terminal end portion, and the effect of moderating the displacement speed by the tab plate is reduced. As a general rule, no welding is required for temporary attachment.

However, in this case, as described above, since the end portions of the joint are not tack welded, there is a drawback that misalignment is likely to occur in the materials on both sides forming the joint, resulting in an undeniable deterioration in quality.

Furthermore, if the thickness of the material on both sides is thin or the size of the tab plate is small, the rigidity of the tab plate becomes small and rotational deformation of the joint end cannot be sufficiently suppressed, resulting in end cracking. There is.

[Purpose of the invention]

This invention was made with the above points in mind,
The purpose is to reliably prevent the occurrence of cracks at the end of the joint when automatically welding a weld joint between two base materials on one side.

[Structure of the invention]

In this invention, two tab plates are joined, and a slit is formed in parallel on both sides of one side of the joint between the two tab plates, each opening at one end edge of the both tab plates, and a slit is formed in the other side of the joint between the two tab plates. one side of the joint is continuous with the welded joint of the two base metals, and the one end edge of both tab plates is welded to the edge of the both bank members, and the end of the joint and The end of one-sided automatic welding, characterized in that the one side of the joint is subjected to continuous seal welding in advance, and the unwelded part near the center of the joint is heated in advance before welding the end of the joint. This is a method to prevent cracking.

〔Effect of the invention〕

Therefore, according to the method for preventing end cracking in single-sided automatic welding of the present invention, two tab plates each having a slit and joined to each other are welded to both bank members, and the ends of the welded joint and the joint of both tab plates are welded to each other. By performing continuous seal welding on one side in advance and preheating the unwelded part near the center of the joint before welding the end of the joint, the rolling bead at the end of the joint will not be temporarily attached during welding. Because it melts gradually instead of rapidly like the heat caused by welding,
The end of the joint can be sufficiently restrained, and rotational deformation of the end of the joint can be reliably suppressed, and rapid expansion due to welding heat of both tab plates can be suppressed by preheating. This makes it possible to prevent sudden deformation of the joint, reliably prevent cracking at the end of the joint, and improve welding quality.

〔Example〕

Next, the present invention will be described in detail with reference to drawings showing one embodiment thereof.

In the drawings, (Ia) and (lb) are two flat base materials of the same thickness, (2) are welded joints formed by both side materials (la) and (lb), and (3a) and (3b). ) are base materials (la) that are mutually joined.

(lb),! : Same thickness and length D (7) left and right tab plates,
(4a) and (4b) are placed on both the left and right sides of the front side of the joint (5) of both tab plates (3a) and (3b), parallel to the joint (2), respectively. 3b) A slit of length A opened at the front edge of (6a), (6b)
are to the left of the slit (4a) on the front edge of the left tab plate (3a), and to the left of the slit (4b) on the front edge of the right tab plate (31).
) are V-shaped grooves formed on the right side of each tab plate (3), and the front side of the joint (5) continues to the joint (2).
a) and (3b) are arranged, and the groove (6) is welded so that the front edges of both tab plates (3a) and (31)) are connected to both bank members (la).
, (lb).

Then, after welding the joint part (5) over a distance B from the rear edge to join both tab plates (3a) and (3b),
Both banks (la), (lb) and both tab plates (3a) are placed on the temporary mounting surface plate.

(3b) is placed, and the front edge of the joint (5) is the joint (2).
The front edges of both tab plates (3a) and (3b) are brought into contact with both bank members (la) and (lb) so that they are continuous with each other.
6a) and (6b) are welded, and the groove (6a)
), , (6b) are square-wound welded to form a joint (2
] The terminal end of the joint (2) extending a distance C from the rear edge, and the joint (5) extending a distance A from the front edge of the joint (5)
5) Continuous sealing welding is performed on the front side to form a multilayer sealing bead.

Furthermore, start welding the joint (2), move the arc from the welding torch along the joint (2) to weld the joint (2), and before said arc welds the terminal end of the joint (2). , the unwelded part near the center of the joint (5), that is, the shaded area in Figure 3, is heated to about 600°C, and the joint (5) is welded from the end of the joint (2) to form a joint ( Welding is completed by welding to a point within the distance from the front edge of 5).

Then, according to the above-described procedure, the plate thickness was 7 mm to 17 fins.

As a result of experimental welding of welded joints with joint lengths of 7 m to 165 m, the number of end cracks that occurred was as shown in the table below, and no end cracks occurred.

Therefore, according to the above embodiment, since the terminal end of the joint (2) and the front side of the joint (5) were continuously seal-welded in advance, the sealing bead at the terminal end of the joint (2) was temporarily attached during welding due to the heat generated by welding. It is possible to melt in stages without melting suddenly, and to sufficiently restrain the terminal end of the joint (2), making it possible to suppress rotational deformation of the terminal end of the joint (2). Unlike the slit tab method, there is no mismatch between the ends of both base materials (la) and (lb).

Furthermore, since the unwelded part near the center of the joint (5) is preheated before welding the end of the joint (2), both tab plates (3a) and (3b) expand rapidly due to arc heat. This makes it possible to prevent sudden deformation of the end of the joint (2), reliably prevent the occurrence of cracks at the end of the joint (2), and improve welding quality. The ratio was about 596, but since the center of the joint (5) was not welded, it became possible to reliably prevent the occurrence of end cracks.

[Brief explanation of the drawing]

The drawings show an embodiment of the method for preventing end cracking in single-sided automatic welding according to the present invention, in which Fig. 1 is an isolated perspective view of the base material and the tab plate, and Fig. 2 is a cutting diagram when welding the base material and the tab plate. The left side view and FIG. 3 are plan views of the welded base material and tough plate. (la), (11)) Base metal, +21 ・=welded joint, (3a), (3b) Tough plate, (4a), (4,1
)) Slit, (5)... joint.

Claims (1)

[Claims] (1) Two tab plates are joined, and slits are formed in parallel on both sides of one side of the joint between the tab plates, each opening at one edge of the tab plates, and on the other side of the joint. one side of the joint is continuous with the welded joint of the two base metals, and the one end edge of both tab plates is welded to the edge of both base metals, and the end of the joint and the End cracking of one-sided automatic welding, characterized in that the one side of the joint is continuously sealed welded in advance, and the unwelded part near the center of the joint is preheated before welding the end of the joint. How to prevent it.