| 摘要 |
PROBLEM TO BE SOLVED: To provide a high strength extra-thick H-steel having excellent fire resistance; and to provide a method for producing the same. SOLUTION: The H-steel has a composition comprising, by mass, 0.005 to 0.07% C, 0.005 to 0.1% Si, 0.005 to 0.3% Mn, 0.001 to 0.01% Al, 0.002 to 0.006% N, 0.01 to 5% Ni, 1.3 to 5% Cu, and the balance Fe with inevitable impurities. In its production method, a slab having prescribed components is heated at 1,100 to 1,300°C in such a manner that the thickness of a layer in which internal oxide is distributed in the surface layer part after the completion of the heating reaches≤100μm, and is thereafter subjected to hot rolling in one or more following conditions: (a) a water cooling and rolling cycle in which the surface of a flange is water-cooled to≤700°C, and is rolled in a heat recuperating stage are performed for one or more times; (b) after the rolling, the flange is cooled to 700 to 400°C by the average temperature at a cooling velocity of 0.1 to 5°C/s, and is let to cool; and (c) the flange is cooled to≤400°C by the average temperature, is reheated at 400 to 500°C, is held for 15 min to 5 hr, and is again cooled. COPYRIGHT: (C)2007,JPO&INPIT |
