2019 年 37 巻 4 号 p. 200-207
Varestraint test is one of the most-used methods to evaluate weld solidification cracking susceptibility. However, standard about the detailed test method and the evaluation method has not been clearly defined. Thus, it is required to standardize the methods of Varestraint test and the evaluation indexes in order to compare the results tested by each researcher.
In this study, round-robin test of transverse-Varestraint test with GTAW was carried out under identical specimens and test conditions using five test machines to clarify the influence of test machine and human factor on the test result. Crack number and crack length were measured using a scanning electron microscope (SEM) and an optical microscope. 6 evaluators measured the crack number and the length.
The maximum crack lengths measured by the evaluators were nearly the same. In contrast, there were big differences in the crack numbers and the total crack lengths. Thus, the influence of the human factor on the maximum crack length was relatively low and that on the crack number and the total crack length was high. This should be caused by different judgment depending on the evaluators for the crack opening and the propagated crack tip. Using SEM was an adequate measuring method for the crack length since the measurement using an optical microscope tended to cause false judgment of wrinkle as cracks. Maximum crack length must be appropriate evaluation index for solidification cracking susceptibility compared to the total crack length and the crack number.