Evaluation of solidification cracking susceptibility in laser welds for type 316FR stainless steel

Abstract

Laser beam welding (LBW) transverse-Varestraint tests were performed to quantitatively evaluate the solidification cracking susceptibility of laser welds of type 316FR stainless steel with two kinds of filler metal (316FR-A and 316FR-B). This found that as the welding speed increased from 1.67 to 40.0 mm/s, the increase in the solidification brittle temperature range (BTR) was greater in the case of 316FR-B (from 14 to 40 K) than 316FR-A (from 37 to 46 K). Based on theoretical calculations for the temperature range over which both solid and liquid phases coexist, for which Kurz-Giovanola-Trivedi and solidification segregation models were used, the greater increase in BTR with 316FR-B was determined to be due to a larger decrease in δ-ferrite during welding solidification than with 316FR-A. This, in turn, greatly increases the segregation of impurities, which is responsible for the greater temperature range of solid/liquid coexistence when using 316FR-B.