Effect of Local Fluctuation of the High Temperature Strength Properties in Weld Metal on Creep Deformation Behavior of Multi-Layer Welded Joint
Hiromichi HONGO, Masayoshi YAMAZAKI, Takashi WATANABE, Masaaki TABUCHI, Tatsuhiko TANABE and Yoshio MON
Abstract:Evaluation of creep properties of the welded joint through taking local fluctuation of the properties into consideration is experimentally or analytically seldom carried out. In this context, the purposes of the present study are to examine the surface strain distribution in the weld metal of a full thickness welded joint specimen and subsequently to investigate the local variation in the properties of the all-weld metal part of the joint using miniature specimens. A welded joint was prepared for 316FR steel plates by gas tungsten arc welding process using Mod. 316 filler wire. Creep tests were conducted at 823K in air using full thickness large welded joint specimens, HAZ and all-weld metal miniature specimens. By interrupting the creep test for the full thickness welded joint specimen, we observed the change in the uniaxial creep strain distribution in the weld metal in the thickness direction of the plate. The last layer of weld metal showed considerably larger creep strain than the central layers of the weld metal. The elastic-plastic creep analysis of the welded joint specimen by FEM was performed using these data. Finite element simulation performed for full-thickness welded joints provided creep strain distribution that is consistent with measured values. From the results above, it is concluded that the creep properties of weld metal in multi-pass, multi-layer welded joints strongly depend on the location of specimen sampling. It is necessary to take the fluctuation of material properties of a weld metal part into consideration when we perform simulation of creep deformation of a welded joint with sufficient accuracy. Key Words:Creep properties, Weld metal, Welded joint, 316FR, Austenitic stainless steel, Multi-layer welding