MANUFACTURE OF NI-CONTAINING STEEL FOR LOW TEMPERATURE EXCELLENT IN CRACK TIP OPENING DISPLACEMENT

摘要

PURPOSE:To manufacture stably a steel plate that has a high crack tip opening displacement at liquid nitrogen temperature by hot-rolling and cooling Ni-steel in a specified condition. CONSTITUTION:A slab heated to 1,000-1,200 deg.C is rolled at =20% cumulative rolling reduction, and hot-rolled at roll finishing temperature of 750-950 deg.C. After completion of hot rolling, the steel plate is cooled to =350 deg.C at a cooling rate of 1 deg.C/sec. Then, the steel plate is heated at a temperature between Ac1-Ac3 and cooled to room temperature at a cooling rate greater than air cooling, and tempered at a temperature lower than Ac1.