1988 Volume 6 Issue 1 Pages 98-103
Diffusion-welded joints were made under welding atmosphere such as vacuum at 4 and 4×10-3 Pa, and Ar, H2 and air at 1×105 Pa. Better welding atmosphere for diffusion welding was investigated from the estimation of mechanical properties of diffusion-welded joints, defects such as void and inclusion, and residual gas in voids of diffusion-welded joints. The materials used were SUS304 stainless steel and Ti-6Al-4V alloy, and the results obtained are as follows:
1) The best welding atmosphere is vacuum at 4×10-3 Pa for both materials in five kinds of welding atmosphere used.
2) For the good selection of welding atmosphere, it is necessary to consider three items as follows.
a) Welding atmosphere which does not have influence on quality of base metal.
b) Welding atmosphere which does not oxidize the welding surface.
c) Welding atmosphere which does not remain in voids.
3) At diffusion-welded joints made under Ar atmosphere, Ar remains in voids of diffusion-welded joints. Ar does not diffuse into the base metal at all, and prevents the shrinkage of voids.