Titanium and niobium carbides are formed at temperatures above 1219°C, whereas chromium carbides are formed in the range 787-1219°C. Steels 321 and 347 contain either chromium or titanium carbides as received from the mill. Intergranular corrosion would develop in these steels if

a) material is heated below 400° C

b) metal is heated to 1310°C, quenched in water and reheated for 30min to 500° C and cooled

c) the material is heated after welding to above 1055°C and cooled rapidly

d) metal is heated between 505 and 760° C.