Evaluating Hot Cracking Susceptibility of Ni-Base SAW Consumables for Welding of 9% Ni Steel

Abstract

A study of Ni-base weld metal hot cracking resistance was made comparing results from Modified Varestraint-Transvarestraint Testing (MVT), metallographic evaluation and mechanical testing. Submerged arc weld metals were produced with Alloy 625, Alloy 59 and Alloy C-276 filler wires at two levels of heat input. Welds were subjected to MVT testing, three-point and wrap-around bend testing as well as metallographic inspection of weld cross-sections. All test methods generally ranked the lower heat input welds as more crack resistant than those produced with a higher heat input. However, MVT testing ranked alloy types in a different order than mechanical testing and metallographic evaluation. Alloy 59 type weld metals were judged most crack resistant with MVT testing and C-276 welds were ranked as slightly better than those produced with Alloy 625 wires. Mechanical testing and metallographic evaluation, on the other hand, ranked the Alloy 625 type weld metals as most crack resistant and Alloy C-276 weld metals as least resistant. Discrepancies between results of the different test methods and practical experience can most likely be attributed to a number of factors including metallurgical aspects and test procedures. It is concluded that test methods simulating actual application welding conditions as closely as possible are most likely to accurately predict hot cracking susceptibility of real weldments. An assessment of the hot cracking susceptibility of welding consumables should therefore preferably be based on results from a combination of test methods.