How to deal with surface defects of the welds in stainless steel welded pipes

To handle the surface defects of stainless steel welded pipes, corresponding treatment methods should be adopted according to different defect types. Here are some common treatment methods:

Welding porosity

Surface grinding: For small and shallow porosity, if the impact on the weld performance is minor, the weld surface can be ground using sandpaper, sand wheels, etc. to smooth out the impurities and uneven areas around the porosity, making the surface smooth and reducing the possibility of stress concentration.

Repair welding: If the porosity is large or numerous, the weld metal at the porosity location needs to be removed. Carbon arc air cutting or mechanical processing methods can be used. Then, repair welding should be carried out. During the repair welding, the welding process parameters should be strictly controlled to ensure the welding quality and prevent the recurrence of porosity.

Welding crack

Crack removal: First, determine the length and depth of the crack. Use an angle grinder or other tools to completely remove the crack along the crack direction, forming a certain shape and size groove. The groove should have sufficient width and depth to ensure complete fusion during subsequent welding.

Welding repair: Select appropriate welding materials and welding processes for repair welding. For stainless steel welded pipes, generally, welding rods or wires that match the pipe material are used. During the welding process, the welding current, voltage, and welding speed should be controlled to avoid excessive welding stress that could cause the crack to reappear. At the same time, appropriate preheating and post-heating measures can be taken to improve the performance of the welding joint.

Stress elimination: After welding repair, to eliminate the residual welding stress, heat treatment methods such as local tempering can be used to reduce the stress level in the weld and the heat-affected zone, improving the crack resistance of the weld.

Welding undercut

Grinding transition: For minor undercut, the undercut area can be ground into a smooth transition surface using a sand wheel or polishing machine to ensure uniform stress distribution on the weld surface and reduce stress concentration. When grinding, control the depth and range of grinding carefully to avoid excessive grinding that could reduce the effective thickness of the weld.

Repair welding: When the undercut depth is deep or the length is long, repair welding is required. Before repair welding, clean the undercut area, then use the appropriate welding process to fill the weld, restoring the weld to the specified size and shape. After repair welding, appropriate grinding and polishing should be carried out to make the weld surface smooth and flat.

Welding bulge

Mechanical removal: For small weld bulges, they can be initially removed using a chisel, file, etc., and then finely ground using a sand wheel or polishing machine to make the weld surface smooth.

Cutting and trimming: If the weld bulge is large and difficult to remove by grinding, plasma cutting or gas cutting methods can be used to cut off the weld bulge. However, attention should be paid to not damaging the weld and the pipe body during the cutting process. After cutting, the cutting surface should be polished and trimmed to meet the surface quality requirements of the weld.

Welding spatter

Mechanical removal: For small weld spatters, they can be initially removed using a chisel, file, etc., and then finely ground using a sand wheel or polishing machine to make the weld surface smooth.

Cutting and trimming: If the weld spatter is large and difficult to remove by grinding, plasma cutting or gas cutting methods can be used to cut off the weld spatter. However, attention should be paid to not damaging the weld and the pipe body during the cutting process. After cutting, the cutting surface should be polished and trimmed to meet the surface quality requirements of the weld.