SOME FACTORS AFFECTING THE WELDED JOINT FRACTURE IN HOT-ROLLED SILICON STEEL COIL

An investigation of the relationships between cold bending plasticity and micro-structures of welded joints in hot-rolled silicon steel coil in welded and heat-treatedconditions has been carried out by optical microscopy, TEM, SEM, and stressanalysis. It is shown that the martensite and carbide formed in weld junctionsand overheated zones as well as the coarse grains in the overheated zones are themain factors responsible for the welded joint fracture. The intersection of numerousdeforming twins in the overheated zones during deformation and their impactagainst phase boundaries also leads to an initiation of cracks. thus promoting thebrittle fracture of the welded joints.