Abstract: When SUS430 was used as the materials to manufacture chimney, the kinks and the cracks were observed. After chemical composition analysis, macro and micro structure examining and mechanical property testing on the fracture parts, the results showed that crystal grain coarsening in HAZ (heat affecting zone) accompanying with the brittle phase (α phase) precipitating, result the plasticity declining, of the material then the cracks happened in the cooling deformation. The heat treatment in welding of SUS 430 is also discussed in the paper.