凝固割れ発生時の限界歪の歪速度依存性と粒界すべりの相関性

動的直接観察測定法(MISO法)による溶接凝固割れ現象の解明(第4報)

抄録

The reason why the critical strain required for the initiation of solidification crack increases with an increase in strain rate is studied. Weld solidification cracking tests and simulated hot ductility test are carried out for stainless steels and Inconel alloy to observe grain boundary sliding. Under the low strain rate as critical strain rate below which the crack can not occur, grain boundary sliding occurs within brittleness temperature range during weld solidification. On the contrary, it hardly occurs under a high strain rate. The contribution ratio of the deformation due to grain boundary sliding to total deformation in weld metal is about 0.2 with simulated hot ductility test under the condition of low strain rate as critical strain rate. Therefore, it is considered that the grain boundary sliding has an important role to the solidification crack initiation in welding. Then, the reason why the critical strain increases with an increase in strain rate is explained from the view-point of contribution of grain boundary sliding to the total strain of weld metal.