| 摘要 |
PROBLEM TO BE SOLVED: To provide an H shape steel for tunnel support good in weld cracking resistance, extremely small in defects caused by hydrogen, furthermore good in toughness and bending workability and having >=440 N/mm2 yield strength in the cross-sectional average. SOLUTION: This H shape steel for tunnel support is composed of a steel having a compsn. contg., by weight, 0.04 to 0.25% C, 0.05 to 0.40% Si, 0.3 to 1.8% Mn and 0.005 to 0.10% Al, in which, as impurities, <=0.010% S, <=0.020% P and <=2.5 ppm H are controlled, and the contents of the other chemical components are controlled to be in prescribed ranges, in which both flange thickness and web thickness are 6 to 25 mm, the yield strength (σf) of the flange is lower than the yield strength (σw) of the web, also, the relation ofσw>1,900-3.5σf is satisfied, and the yield strength on the cross-sectional average is >=440 N/mm2. |
