Laser welded steel structural member and steel material used for the steel structural member

摘要

PROBLEM TO BE SOLVED: To provide a steel structural member having a laser welding part excellent in fatigue strength property and steel material used in its steel structural member. SOLUTION: In this laser-welded steel structural member, the value of weighted average of welding metal side vicat hardness in the region where the distance from the bonded part after laser welding is within 1.6 mm on the position of 1 mm depth from the surface of base material is =1.6 times of the value of weighted average of welding heat affecting part side vicat hardness in the region where the distance is within 1.6 mm. Therein, the value of weighted average of the vicat hardness in the region where the distance from the bonded part is within 1.6 mm denotes the value calculated by the following expression when the test is performed with a test force of =9.807N; 0.4HV10.4 +0.3HV10.8 +0.2HV11.2 +0.1HV11.6 , therein, the Vickers hardness on the position where the distance from the bonded part is L mm is HV1L.