Assessment of Weld Embrittlement in A516 Steel Due to Multiple Repair Welds

Abstract

A 3-million gallon petroleum storage tank was fabricated in the Midwest using A516 steel. The initial fabrication schedule had become compressed; welders worked hurriedly and did not produce good welds. Numerous welds had to be repaired via grinding and rewelding. The quality of the steel near the welds were questioned regarding their ductility; it was thought that the material had become embrittled and would fail prematurely in a catastrophic manner and be more susceptible to poor performance during the winters (−25 °F) because of welds being repaired up to six (6) times. The contracting company requested that the repair welds be evaluated and compared to the base metal and the original welds. The repair welds could not be removed from the structure. Therefore, the welding vendor was requested to provide mock-up welds and mock-up repair welds that simulated the welding process used during fabrication. The welding vendor provided base metal, mock-up of in-service weld, and mock-up of in-service repair weld for metallographic evaluation and mechanical testing. The vendor also provided hardness data for in-service weld and in-service repair weld along with hardness data for mock-up of in-service weld and mock-up of in-service repair weld. The mock-up welds adequately represent the production welds (original welds and repaired welds). All the test results indicate that the repaired welds are of similar quality as the original weld.