Laser Weldability of 21Cr-6Ni-9Mn Stainless Steel: Part 2-Weldability Diagrams

In this second part of the study, weldability diagrams developed to relate solidification crack susceptibility and chemical composition for laser-welded Type 21Cr-6Ni-9Mn (21-6-9) stainless steel are presented. Sigmajig testing on 14 commercial 21-6-9 alloys, 20 experimental 21-6-9 alloys, and seven other high-N, high-Mn austenitic stainless steels was used to develop weldability diagrams for solidification crack susceptibility for laser welding of Type 21-6-9. Three travel speeds were used to show the changes in minimum Cr-eq/Ni-eq for primary ferrite solidification as solidification rate increased with travel speed. Primary austenite solidification was observed below 1.55 Cr-eq/Ni-eq (Espy equivalents) at 21 mm/s travel speed. At 42 mm/s travel speed, a mix of solidification modes were displayed for alloys from 1.55 to 1.75 Cr-eq/Ni-eq. Primary ferrite solidification was observed above 1.75 Cr-eq/Ni-eq at both 42 and 85 mm/s travel speeds. No solidification cracking was observed for alloys with primary ferrite solidification. Variable cracking behavior was found in alloys with primary austenite solidification(,) but in general, cracking was observed in alloys with greater than 0.02 wt-% combined impurity content according to (P + 0.25).