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An welded joint of 304 stainless steel was fabricated by SAW with use of 308 filler metal to investigate the influence of welding pass sequence and sampling location of the specimen in the welded joint on the creep properties of weld metal zone and heat affected zone in the joint. Creep tests were conducted at 823K and 235MPa. In the HAZ of the welded joint, there existed a hardened region of which specimen showed a little smaller creep rate and longer life than base metal. The 308 weld metal had larger creep rate than the 304 base metal and the life of the former was only 10% of that of the latter (under-matching), however, the difference of the lives becomes smaller for long times. 0.2%

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.

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