Corner cracking associated with the production of square tubing from low carbon ferritic stainless steel

Low carbon 11.5% chromium stainless steels are finding increasing use in industry as square or rectangular shapes. During this process longitudinal cracks can sometimes develop at one of the inner corners of the section. An investigation has shown that the processing of round into square tubing with very sharp corners can cause excessive cold working at the inner corners of the squared tube. This, together with the high tensile residual stresses and a susceptible microstructure due to the presence of grain boundary carbides, can result in brittle cleavage cracking. Measures that can be used to reduce the problem are described.