Abstract: The thermal simulation experiment process of SUMITEN 950-TMCP highstrength steel was introduced. The experiment data were verified. It was clear that the second thermal cycle has the function to improve the toughness of the welded coarse grained region of this type steel. According to this, the necessity to adopt the multiplayer and multipass welding in construction was proposed. Based on material test result, a conclusion was obtained that third time thermal cycle has not obvious function to improve the toughness of the coarse grained region in welded joints of the material.

Key words: high-strength steel, coarse grained region, thermal simulation, second thermal cycle