RESEARCH ON TREATING PROCEDURE OF EQUIAXED GRAIN CRYSTALLIZING FOR AUSTENITIC STAINLESS STEEL WELDING

In order to improve the corrosion-resistance and the mechanical properties of the welded pipe, the austenitic stainless steel butt welded pipe has been made to undergo a diameter reduction pre-deformation drawing and an annealing treatment at proper temperature. As a result of these, the welding seam structure recrystallization has occurred, ie the equiaxed grain structure has replaced the strongly directional columnar grain stucture (or columnar branch grain), namely, equiaxed grain crystallization. The results also show, equiaxed grain crystallized weld not only becomes consistent with the matrix in microstructure appearance on the whole, but also becomes improved in corrosion-resistance. For the purpose of insuring the welding structure to be changed into fine equiaxed grain completely, the pre-deformation amount of the reduction diameter rate must be great than 9.40%, and the optimum annealing temperature zone should be within 980~1 000℃.