Assessment of Weld Embrittlement in A516 Steel Due to Multiple Repair Welds
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CASE HISTORY—PEER-REVIEWED
Assessment of Weld Embrittlement in A516 Steel Due to Multiple Repair Welds Wayne Reitz
Submitted: 10 March 2011 / in revised form: 5 July 2011 / Published online: 1 September 2011 Ó ASM International 2011
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. Keywords Brittle Embrittlement Evaluation Ferrous metals Fracture toughness Heat-affected zone Weld repair
Introduction It is a well known fact that weld metal tends to be strong and brittle, while heat-affected-zones (HAZ) tend to be weak and ductile. However, we should know what happens when welds are repaired numerous times: does the structure develop brittle regions that could fail when impacted at cold temperatures, or does the ductile-brittle-transitiontemperature (DBTT) increase? How can these repairs be evaluated if samples cannot be removed? This article has two (2) focuses: weld assessment to confirm integrity of tank, and how to develop samples for testing along with correlating the fabricated samples with the production unit. 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.
Analysis The base plate, mock-up original weld, and a mock-up repair weld were metallographically inspected, and characterized via mechanical testing (hardness, tensile, and Charpy V-notch), and the vendor-supplied hardness data were overchecked.
Results Hardness Overchecks
W. Reitz (&) Reitz Consulting, 96 Meadowlark Lane, Fargo, ND 58102, USA e-mail: [email protected]
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The welding vendor provi
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