| 摘要 |
PROBLEM TO BE SOLVED: To obtain wide flange shapes having a specified web thickness, the web thickness/flange thickness ratio and yield strength by rolling the wide flange shape using a rectangular billet or rough shape billet having a specific composition and specific carbon equivalent as a base stock by water-cooling only the upper surface of the web as compaired to the outside of the flange in the intermediate rolling process and rolling the back surface of the web without pouring water. SOLUTION: In the rolling process of the wide flange shape which is made by using the rectangular billet or the rough shape billet which consists of, by weight, 0.1-0.2% C, 0.05-0.5% Si, 0.6-1.6% Mn, 0.01-0.06% Nb, 0.005-0.1% Al, 0.002-0.01% N and the balance Fe with inevitable impurities and whose carbon equivalent Ceq., which is expressed by the equation, is <=0.42 as the base stock, only the upper surface in addition to the outsides of the flanges is water-cooled before and behind or either before or behind an intermediate rolling mill and the web is rolled one or more times in a recuperation process with the intermediate rolling mill. The wide flange shape having a web thickness of >=23 mm, the web thickness/flange thickness ratio of >=1.0 and yield strength of >=430 N/mm2 is obtained.
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