Common weld molding defects in stainless steel pipes include incomplete penetration, unmelted table, burn through, undercut and weld. The cause of these defects is often caused by improper groove size, improper selection of welding process specifications, or misalignment of the weld wire to the center of the weld.
Incomplete penetration: The phenomenon that the joint root is not completely penetrated during welding is called incomplete penetration. Stainless steel water pipes can cause such defects in both single-sided and double-sided welding. The main reason for the formation of incomplete penetration is that the welding current is small or the welding speed is too high, or the groove size is not suitable and the welding wire is not aligned with the center of the weld.
Unfused: When welding, the part of the stainless steel pipe weld metal and the base metal or between the weld bead and the weld bead is not completely fused. Unfused can be divided into sidewalls that are not fused, layers that are not fused, and roots that are not fused. The molten pool metal is discharged to the tail under the action of the arc force to form a groove. When the arc moves forward, the groove is filled with liquid metal. If the liquid metal layer at the groove wall has solidified, the liquid is filled. The heat of the metal is not sufficient to cause it to melt again, resulting in unfused. In the case of submerged arc welding, slag inflow occurs in the fusion zone. In order to prevent such defects during high-speed welding, it is necessary to increase the melting width or use double arc welding.
- Burn through: When the stainless steel pipe is welded, the molten metal flows out from the back of the weld, and the phenomenon of forming a perforation is called burn through. Stainless steel pipe welding current is too large, the welding speed is too small or the groove gap size is too large, etc. may form such defects.
- Undercut: The phenomenon that the stainless steel water pipe is formed along the base material of the weld toe to form a depression or a groove is called a undercut. The undercut may be continuous or intermittent. Stainless steel water pipes may cause such defects during high current high speed welding. This type of defect can also occur if the mishandling is done while welding the butt joint.
- Welded metal: The metallurgy formed by the molten metal flowing into the unmelted base metal outside the weld when the stainless steel pipe is welded is called a weld bead. There is local fusion at the weld. The weld is caused by too much filler metal, which is related to the small gap and groove size, low welding speed, small voltage or large wire extension length.
- Unfilled: Stainless steel water pipes are formed by continuous or intermittent grooves on the weld surface due to insufficient filler metal during welding.
- Collapse: Excess metal that collapses through the root of the weld is called collapse.
Stainless steel water pipes, in addition to the above defects, in addition to the above defects, there are back shrinkage grooves, poor profile, super high, surface irregularities, surface pores, root pores, poor weld joints, arc scratches, splashes, etc. Weld molding defects, mostly due to improper welding processes. Therefore, the development of a suitable stainless steel pipe welding process, careful operation can fundamentally prevent the occurrence of weld molding defects. In addition, it is very important to take timely contingency measures when certain process conditions change during stainless steel pipe welding.
Source: China Stainless Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)