| 摘要 |
PURPOSE:To improve the reduction effect in the central part of a steel stock by starting rolling of the stock heated to a temp. higher than the Ac3 point, cooling the stock so that temps. at the surface and in the central part down to respectively specific temps., then reheating the stock up to a prescribed temp. range, and continuing the rolling. CONSTITUTION:A cast steel stock is heated to a temp. higher than the Ac3 point and rolling of the stock is started. At that time, the stock is cooled so that a surface temp. is at a temp. lower than the Ar1 point and a central part temp. keeps a temp. higher than Ar3 point. Then, the stock is reheated so that the surface temp. is at a temp. in the range higher than the Ac1 point + 20 deg.C and lower than the Ac3 point and the rolling is continued. Hence, the stock surface layer part transforms from ferrite to austenite during the temp. rising and the central part is an austenitic phase or is in a state where the part is transforming to ferrite. Therefore, the central part bears a strong draft and the drafting effect is improved because a large difference between deformation resistances of the surface layer and central parts is generated. |
