| 摘要 |
PURPOSE:To prevent breakage accident and also to increase quenching rate, by holding a diffusion-annealed sleeve roll at a temp. in a specific range until respective temps. in the inner and outer layers are equalized and then subjecting the above to rapid heating to apply temp.-rise to the outer layer alone so as to carry out hardening treatment. CONSTITUTION:After a sleeve roll stock for shape rolling whose outer-shell layer is composed of adamite is diffusion-annealed quench-and-temper treatment is applied. In the above heat treatment, the above sleeve roll stock after diffusion annealing is held at a temp. between 500 and 750 deg.C until respective temps. in the inner and outer layers are equalized. Subsequently, rapid cooling is applied to subject only the outer layer of the roll to temp.-rise up to 830-950 deg.C. Then, the roll stock is taken out of a furnace and cooled to undergo hardening treatment. By this method, the difference in temp. between the inner and outer layers is reduced in the hardening stage so as to reduce stress. As a result, the roll stock causes no occurrence of breakage accident in the hardening and subsequent annealing stages and is also increased in quenching rate, and high hardness can be provided by means of heat treatment alone.
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