Single and multi-layer welding of butt welding flange

Because people are in an unnatural position during the overhead welding of the butt welding flange, it is difficult to operate stably. At the same time, the heavy welding torch and cable must be lifted to increase the difficulty of the operation. In addition, the molten iron in the molten pool is prone to sag during overhead welding, and it is easy to form a convex weld bead, which causes the molten iron to flow in severe cases. Therefore, the welding parameters should be strictly controlled to get a good weld formation.

　　 Butt welding flange single pass overhead welding

　　Thin butt-welded flanges are often single-sided welding. In order to be able to penetrate through, the butt-welded flange should have a gap of 1.4~1.6mm.

　　 Use thin wire (0.8~1.2mm in diameter) for short-circuit transfer welding, the welding current is 120~130A, and the arc voltage is 18~19V.

　　 When operating the welding torch, aim at the center of the groove, similar to the right welding method.

　　 At this time, the molten pool should be maintained in a straight line or slightly swinging by the arc force and surface tension. When the welding speed is too slow, the molten pool metal sags, and the surface of the weld bead appears uneven. In severe cases, the molten pool metal is lost. Therefore, you should always pay attention to the state of the molten pool during welding, and adjust the welding speed and swing mode in time. If the torch angle is too large, it will cause convex weld bead and undercut.

　　 Butt welding flange multilayer overhead welding

When the butt welding flange is thick, multilayer welding is required. When there is no backing plate, the first layer of welding bead is similar to single-sided welding. When there is a backing plate, there should be a certain gap between the butt welding flanges, and the current can be slightly larger, but it is still a short-circuit transition.

　　At this time, the welding current is 130~140A, and the arc voltage is 19~20V.

　　 During operation, the welding torch should be aligned with the center of the groove and move at a constant speed with the right welding method.

　　At this time, it must be noted that the backing plate and the root of the groove should be fully penetrated, and there should be no convex weld. To this end, a small swing should be used and a little stay on both sides of the weld bead in order to obtain a flat surface weld bead, and create good conditions for the subsequent fill weld bead.

　　The 2nd and 3rd layers are welded in the form of a uniform weaving torch, but a short stay should be made at the interface between the previous place and the groove surface to ensure sufficient penetration and prevent undercut.

　　 The welding parameters used at this time are the welding current 120~130A, and the arc voltage is 18~19V.

　　 After the 4th layer, because the width of the welding seam is too large, it is easy to produce incomplete penetration and pores when the swing is too large. Therefore, it is best to use the deposition method shown in Figure 3, that is, from the fourth layer onwards, each layer is welded with two weld passes.

　　The first bead of these two welds should not be too wide, otherwise it will cause the weld bead to sag and the groove left for the second pass is too narrow, and it is easy to make the second pass form an incomplete and convex weld. So the first weld bead skips the center, and the second weld bead should overlap with the first weld bead.

　　The butt welding flange cover weld bead is a modified bead, which should be beautiful.

　　 First, ensure that the surface of the previous layer of the cover weld bead is flat, and make the weld bead be about 1~2mm away from the surface of the butt welding flange.

The butt welding flange cover welding bead is also completed by two weld passes; when welding these two welds, a little stay on both sides of the arc groove to prevent undercut and insufficient reinforcement. When welding the second weld pass Pay attention to the uniform overlap with the first weld bead to prevent irregular weld bead height and width.

　　 At this time, the welding parameters used for the butt welding flange are relatively small, the welding current is 120~130A, and the arc voltage is 18~19V.