Repair Welding

If not properly controlled, it is possible for a weld repair to be more detrimental than the original defect, due to adverse microstructural effects in the HAZ, especially on high Ceq% materials, therefore separate repair welding procedures are normally required.

Some specifications may not permit the same weld area to be repaired more than once, again due to adverse metallurgical effects.

Some specifications may limit the length of repairs, taking into consideration resulting metallurgical changes and stresses acting on the rest of the unopened weld.

Removal of defective areas

The specification or procedure will govern how the defective areas are to be removed. At least one of the following removal methods will be used:

• grinding,
• gouging using an arc process,
• gouging using a fuel gas process,
• chipping,
• machining,
• filing.

Prior to repair welding, the defective area would normally be removed or blended without impinging onto the parent material, i.e. the original weld joint profile would normally have to be maintained. If unacceptable defects exist in the parent material, e.g. surface laminations, arc strikes, gouges etc., the action to be taken will again depend on the specification requirements. Some specifications will allow grinding and re-welding, whilst others will require the defective area to be cut off if the material thickness is reduced below certain limits after grinding/blending.