Debasis, HCSI limit : safe limit : This depends on specific application and corrosion service needs. Delta ferrite improves hot cracking resistance in austenitc SS welds, better IGC /SCC resistance - no doubt. HCSI is not the only factor to be taken into account while welding austentic S.S. You have to also recognize that higher delta-ferrite in austenite may cause complex metallurgical reactions to include formation of secondary phases (precipitates) which will have adverse effect on corrosion resistance and also loss of mechanical properties (impact strength). With ferrite promoting elements Cr,Mo,W, a wide range of precipitates can form from 1000 deg cent to 300 deg cent during solidification from welding. These will have adverse effect on CR / Impact strength. User may have to consider or balance needs from C.R and Mechanical properties improvement also instead of only taking HCSI where a 3 FN or 3% delta ferrite would give improved HCSI /IGC resistance. For Ex: In Urea carbamate service, in fertilizer plants, for the same application of S.S. 316 L grade, a low delta-ferrite austenitic SS weld is preferred to improve C.R . Ferrite content of < 1.0% is preferred for this service. HCSI is not fully taken into consideraton. Another Ex: For dissimilar welding involviing -Inconel 600 / S.S 316 , a via media delta-ferrite limit in austenite would be preferable. 1% delta ferrite would improve mech properties and also C.R - especially in highly restrained weld design joints like tube to tube sheet groove weld designs. Trust this will help you C.V.Srinivasan Nishi Engineers Pvt Ltd India June 28, 2007 E-mail: nishi@vsnl.com >Hot Cracking in Aust SS Weld depends on >segregation/impurities and can be controlled by introduction >of >=3% delta ferrite. > >Like CE ( weldability) Hot Cracking Susceptibility often >derived by the formula as below : > >HCS Index = [%C x (%S + %P + 0.04Si + 0.01Ni ) ] / [ 3x%Mn >+ %Cr +%Mo + %V ] x 10 -3 > >Any idea for values below which safe ? >regards