EVALUATION OF BENDING LIMIT OF 9CR-1MO-V STEEL BY MASTER CURVE AND FAILURE ASSESSMENT DIAGRAM METHOD -EVALUATION OF WELDED METAL

摘要

In this study, the bending and rolling limit of 9Cr-1Mo-V steel plate welded using submerged arc welding (SAW) was investigated. Hereafter in this report, the bending limit refers to bending by press or by roller. Since heat treatment after welding and before the bending process may be effective in preventing brittle fracture during bending, the effect of postweld heat treatment (PWHT) for improving toughness was evaluated by Larson-Miller parameter (LMP). Charpy impact tests of SAW welded parts made of 9Cr-1Mo-V steel plates were performed, and the absorbed energy of the weld metal was lower than that of the heat affected zone (HAZ) and the base metal, however the absorbed energy was recovered by PWHT. The absorbed energy increased as LMP increased. The reference temperature T_0 for the master curve method was estimated by the results of Charpy impact tests. The bending limit was estimated by the method proposed in the previous study. The fracture probability during the bending process seems to decrease as LMP increases.