Method for medium sized or thin plate blank continuous casting and continuous rolling for producing superfine crystal grain steel plate and the steel plate

The invention discloses a manufacturing method of hyperfine crystal steel board through continuous rolling thin board, which comprises the following steps: allocating raw material with 0.12-0.18% C, 0.15- 0.35% Si, 0.65-1. 20% Mn, not more than 0.02% P, not more than 0.015% S and Fe; casting in the 100-200mm*1000-2000mm blank; setting the loading temperature over 800 deg. c; heating to 1100-1280 deg. c; reducing rough rolling of blank to 30-60 mm; setting refining rolling temperature between 920 and 1050 deg. c; exerting multi-channel and large-deforming strain accumulation with even deforming velocity at 1-10/s; setting the refining rolling outlet temperature at 750-900 deg. c; setting cooling speed of laminar flow at 10-45 deg. c/s; coiling at 400-620 deg. c; setting the norm of continuous heat rolling steel at 2-18mm with even crystal size at 3-7um and yielding strength over 400Mpa; making the extending proof strength between 510 and 580 Mpa and extending rate over 26%.