JPH0318987B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for preventing cracking at the end of a welded joint of two base metals, which prevents the occurrence of cracking at the end of the joint when automatically welding a welded joint on one side. [Prior Art] 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 in 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.
As described in , one of these methods is the slit tab method, which attempts to moderate the displacement speed of the joint end due to rotational deformation.
For example, when welding a welded joint between two base metals,
1m), and then tack-weld the end edge of the tab plate, which has a pair of slits parallel to the welding line of the joint, on one side of the terminal edge, and firmly secure the end edge of the tab plate. By welding to, when welding,
When an arc generated from a welding torch moves along the joint and reaches the tab plate, heat from the arc is retained in both the slits to prevent thermal expansion of the entire tab plate; The restraining force of the tab plate on the end of the joint is not significantly weakened due to thermal expansion of the tab plate, and rotational deformation of the end of the joint is suppressed, thereby preventing the occurrence of end cracking. 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 arc causes the tack weld bead at the terminal end to melt, and the terminal end, which had been restrained by the tack weld bead, is released all at once, causing rapid rotational deformation in the terminal end, causing the tab plate to deform. As a general rule, tack welding at the end of the joint is not performed because the effect of moderating the displacement speed will be diminished. However, in this case, as described above, the end portion of the joint is not tack-welded, so that the two base materials forming the joint are likely to be misaligned, resulting in an undeniable deterioration in quality. Furthermore, if the thickness of both base materials 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.
It has the disadvantage that end cracks occur. [Object of the Invention] The present invention has been made with the above-mentioned points in mind, and provides an object to reliably prevent the occurrence of cracks at the end of the joint when automatically welding one side of a welded joint of two base materials. The purpose is to [Structure of the Invention] This invention temporarily welds a welded joint formed by two base metals in the front-rear direction except for the front end, and attaches a tab plate having two parallel slits in the front-rear direction to the base metals. In the method for preventing end cracking of the joint in single-sided automatic welding, the tab plate is welded by positioning both slits on the front side of the material on both sides of the joint to prevent end cracking of the joint when performing single-sided automatic welding of the joint. divided into symmetrical left and right tab plates, welded the front part of the joint of the left and right tab plates, aligned the joint with the joint, and attached the left and right tab plates to both base materials. the left and right tab plates are welded to the base metals, seal welding is performed from the front end of the joint to the rear of the joint, and the end welding part at the center of the joint is pre-welded. This is a method for preventing end cracking in one-sided automatic welding, characterized by heating and then welding continuously from the joint to the center of the joint. [Effects of the Invention] Therefore, according to the method for preventing end cracking in single-sided automatic welding of the present invention, the left and right tab plates, each having a slit and welded at the front, are welded to both base materials, and the welded joint is welded. The front end and the rear part of the joint between the left and right tab plates are pre-continuously seal welded, and the unwelded part near the center of the joint is preheated before welding the end of the joint, which is similar to the conventional slit tab method. In addition, by not tack welding the end of the joint, it is possible to prevent misalignment between the two base metals, and the sealing bead at the end of the joint can be melted gradually during welding instead of melting suddenly like the bead caused by tack welding. Because it is melted, the end of the joint can be sufficiently restrained, and even if the base material is thin or both tab plates are small, rotational deformation of the end of the joint can be reliably restrained. Since the rapid expansion of the tab plate due to welding heat can be suppressed, it is possible to prevent sudden deformation of the joint end, which reliably prevents cracking of the joint end and improves welding quality. It becomes possible to achieve this goal. [Embodiment] Next, the present invention will be described in detail with reference to drawings showing one embodiment thereof. In the drawing, 1a and 1b are two flat base materials of the same thickness, 2 is a welded joint in the front and back direction formed by both base materials 1a and 1b, and 3a and 3b are joined to each other so that the front part of the joint is Left and right tab plates with the same thickness and length D as the welded base metals 1a and 1b, 4a and 4b are lengths formed on both left and right sides of the rear part of the joint 5 of both tab plates 3a and 3b. A longitudinal slit, 6
a, 6b are slits 4a on the rear edge of the left tab plate 3a
and to the right of the slit 4b on the rear end edge of the right tab plate 3b.
a, 3b are arranged, both grooves 6a, 6b are welded, and both tab plates 3a, 3b are welded to both base materials 1a, 1b. After welding both tab plates 3a and 3b by over-welding the joint portion 5 over a distance B from the front edge, both base materials 1a and 1b and both tab plates 3a and 3b are placed on the temporary mounting surface plate. The joint 5 is brought into contact with the base metals 1a, 1b so that the joint 5 is aligned with the joint 2, and both grooves 6a, 6b are welded together, and the ends of the grooves 6a, 6b are The part R is square-wound welded, and the terminal end of the joint 2 extending a distance C from the front edge of the joint 2, and the rear part of the joint 5 extending approximately a distance A from the rear edge of the joint 5 are continuously sealing welded to form a multilayer seal. Form a bead. Furthermore, the welding of the joint 2 is started, and the arc from the welding torch is moved along the joint 2 to weld the joint 2, and before the arc welds the end of the joint 2, the arc is moved around the central part of the joint 5. If the unwelded part of the joint 5, that is, the shaded part in Fig. 3, is heated to about 600°C and the joint 5 is welded from the end of the joint 2 to a point at a distance A from the front edge of the joint 5, welding is completed. end. Then, according to the procedure described above, the plate thickness is 7 mm to 17 mm.
As a result of experimental welding of welded joints with joint lengths of 7 m to 16.5 m, the number of end cracks occurring is as shown in the table below.

[Table] No terminal cracks occurred at all. Therefore, according to the above embodiment, since the terminal end of the joint 2 and the front side of the joint 5 are continuously seal-welded in advance, the sealing bead at the terminal end of the joint 2 melts rapidly during welding like a bead formed by tack welding. It is possible to sufficiently restrain the terminal end of the joint 2 by melting in stages without slitting, and it is possible to suppress rotational deformation of the terminal end of the joint 2. Moreover, unlike the conventional slit tab method, both base materials 1a , 1b will not be misaligned at the end. Furthermore, since the unwelded part near the center of the joint 5 is preheated before welding the end of the joint 2,
To suppress rapid expansion of both tab plates 3a and 3b due to arc heat, to prevent rapid deformation of the terminal end of the joint 2, and to reliably prevent the occurrence of cracks at the terminal end of the joint 2. This makes it possible to improve welding quality. In addition, when the center part of the joint 5 was welded, the occurrence rate of end cracks was about 5%, but since the center part of the joint 5 is not welded, the occurrence of end cracks can be reliably prevented. became possible.

[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 tab plate. 1a, 1b...Base metal, 2...Welded joint, 3a,
3b...Tab plate, 4a, 4b...Slit, 5...
...junction.

Claims (1)

[Scope of Claims] 1. Temporarily weld the welded joint formed by the two base materials in the front-rear direction except for the front end, and attach a tab plate having two parallel slits in the front-rear direction to the back of the base metals. In the method for preventing end cracking of the joint when welding the joint by positioning both slits on both sides of the joint on the front side to prevent end cracks of the joint when automatically welding the joint on one side, Divide into symmetrical left and right tab plates, weld the front part of the joint of the left and right tab plates, align the joint with the joint, and connect the left and right tab plates to the front sides of both base materials. The left and right tab plates are welded to the base metals, seal welding is performed from the front end of the joint to the rear of the joint, and the end welding part at the center of the joint is preheated. . A method for preventing end cracking in single-sided automatic welding, characterized in that the welding is then carried out continuously from the joint to the center of the joint.