| 摘要 |
The present invention relates to a steel plate with low yield-tensile ratio and high toughness, comprising the following chemical compositions, by weight, C: 0.05-0.08%, Si: 0.15-0.30%, Mn: 1.55-1.85%, P‰¤0.015%, S‰¤0.005%, Al: 0.015-0.04%, Nb: 0.015-0.025%, Ti: 0.01-0.02%, Cr: 0.20-0.40%, Mo: 0.18-0.30%, N:‰¤0.006%, O‰¤0.004%, Ca: 0.0015-0.0050%, Ni‰¤0.40%, wherein, the ratio Ca/S is ‰¥ 1.5, other compositions being Ferrum and unavoidable impurities. The steel plate is fabricated by the following method: heating a continuous casting slab or billet at temperature of 1150-1220°C, then multi-pass rolling it, with the total reduction ratio being ‰¥80% and the rolling finishing temperature being ‰¥850°C; water-cooling rapidly the rolled steel plate at speed of 15-50°C/s to the temperature range from Bs-60°C to Bs-100°C, then air-cooling it for 5-60s; after the cooled steel plate entering an online induction heating furnace, heating it at speed of 1-10°C/s to Bs+20°C, tempering it for 40-60s, then air-cooling it outside the furnace. The steel plate has a thickness of 10-25mm, a yield strength of ‰¥500MPa, a yield-tensile ratio of ‰¤0.75, an elongation A 50 of‰¥20%, and A kv at -60°C of ‰¥ 200J. |
