| 摘要 |
PURPOSE:To obtain a steel plate of high strength and high yield ration excellent in machinability and cold toughness by heating and hot rolling steel composed of specified components such as C, Si etc. and taking up at a specified temperature and, at the same time, cooling at a specified cooling speed. CONSTITUTION:Steel composed of 0.01-0.08% C, 0.1-1% Si, 1.5-2.2% Mn, 0.2-0.6% Cr, 0.05-0.2% Ti, <=0.05% acid soluble Al, <=0.001% S, <=0.01% Ni, the rest iron and impurities is heated to >=1,200 deg.C and hot rolled at a finishing temperature of >=880 deg.C and taken up at 450-600 deg.C, making the average cooling speed from the hot rolling finishing temperature to taking up speed >=8 deg.C/sec. By this way, a seel plate of the type given in the titled which is suitable for construction machines, automobiles etc. can be obtained inexpensively. The cold toughness is raised and material quality is stabilized by adding a total of 0.005-0.01% of Ca or one or two of rare earth elements to said composition. |
