| 摘要 |
PURPOSE:To obtain a cast steel for low temp. use ensuring toughness at low temp. by heating and cooling a 9% Ni steel under specified conditions, heating and cooling it again under specified conditions, and carrying out tempering at a specified temp. CONSTITUTION:A steel consisting of 0.01-0.10% C, <=0.15 Si, <=0.90% Mn, 7.5-12.0% Ni, <=0.50% Mo and/or W and the balance Fe with impurities including <=0.015% P and <=0.005% S is heated to the Ac3 point -950 deg.C, held at the temp., and cooled at a higher cooling rate than the air cooling rate. The steel is heated again to the Ac1 point - the Ac3 point, held at the temp., and cooled at a higher cooling rate than the air cooling rate. The steel is then tempered at 560 deg.C- the Ac1 point. Thus, the toughness of the 9% Ni cast steel at low temp. is improved to such a degree that the toughness is not deteriorated at all when the cast steel is rolled. |
