| 摘要 |
PROBLEM TO BE SOLVED: To provide a production method for easily obtaining a steel product at a low cost. SOLUTION: A forged material is obtained with a refining, casting and forging, and the forged material is charged into a heating furnace 8 and heated, and the temperature of the forged material is raised to the temperature of the A<SB>3</SB>point or higher by heating. A hot-rolling is applied to the forged material by a large-sized rolling machine 10 to obtain a round bar-shaped formed product by the rolling. The formed product is forcibly cooled on a cooling bed 12, and in such a state that the surface temperature of the formed product is 100°C or higher, the article is charged into a tempering furnace 14. In this stage, martensitic transformation is not completed in the center of the formed product. In the tempering furnace 14, the formed product is gradually cooled to obtain the round bar steel. COPYRIGHT: (C)2010,JPO&INPIT
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