Steel SS400 is a kind of new steel with superfine grain and super purity, and has an excellent mechanical property. Study
of
welding structure characteristics is essential for its promotion and application. The method of numerical analysis was used to evaluate the
fracture properties of the actual weld joints in reference to SS400 parent material properties. With the help of a MSC. MARC commercial software, the fracture mechanics parameters of the parent material and the actual weld joint with various central transverse crack lengths were computed, and the tensile process of that model was simulated with the three-dimension finite element method. MIG was used in the welding process. The central crack was in the fusing zone between the weld and heat affection zone(HAZ). The crack size and position, the plotting of the mesh and the boundary condition of the parent material panel used for comparison were entirely the same as those of the welding panel. With the help of the results of the computation, the effect of the weld joint mechanical heterogeneity on stress-strain field was analyzed. Furthermore, based on the theory of full-scale yielding, the fracture parameter CTODs, was analyzed and compared. The result shows that the CTOD value of each weld joint is invariably lower than that of the pure parent material with the same crack size. Consequently, the fracture-resistant ability of the weld joint is superior to that of the all parent material.