1993 Volume 11 Issue 1 Pages 173-179
In the previous reports, the proportion between transformation superplasticity and transformation expansion on the amount of the stress releasement was examined. And then, the appropriate conditions (transformation temperature) which made most use of the stress releasement in welding by transformation superplasticity was obtained. During transformation, a speciemen was plastically distorted by a small stress of the order of 1 MPa. On the other hand, to decrease angular distorsion and residual stress is very important for welding design and fabrication. There are, as well-known, many countermeasures (weld heat-input, preheating, postheating, peening and so on) to reduce them.
In the present report, the trial welding rods with many kinds of transformation temperature were made and the effect of transformation temperature on angular distortion in welding was examined. The results are shown as follows;
1) Under the condition of a constant heat input, transformation temperature has an important effect on angular distortion in welding in spite of its weld length.
2) The transformation starting temperature which is most effective to reduce angular distortion is 250-300°C (in this case interpass temperature and preheating temperature is 150°C).
3) There is respectively the best interpass temperature and preheating temperature for each weld metal with transformation temperature to reduce angular distortion.
4) Transformation temperature was moved by the dilution with base metal or prepass weld. So, an effect of dilution is important for single pass welding and so on.
