| 摘要 |
PURPOSE:To improve sand burning hardenability by continuously annealing a cold- rolled steel plate of a low carbon steel contg. a specific amount of nitrogen at temps. above its recrystallization temp. CONSTITUTION:A steel slab contg. 0.004-0.02% C, 0.05-0.70% Mn, 30-200 ppm free nitrogen amount and 0.05% soluble Al is hot-rolled to make a hot-rolled coil. In this case, the hot rolling finish temp. is kept at 850-900 deg.C and the coiling temp. at 450-700 deg.C. After the coil is pickled, it is cold-rolled to a steel plate of about 1.2mm. thickness, following to which it is continuously annealed at 650-900 deg.C temps., and is further subjected to overaging treatment for 3min then to skin pass rolling of 0.8%, whereby it is made into a steel plate of the final product. The high strength steel plate having 12-18kg/mm.<2> sand burning hardenability is produced. |
