Free-cutting pre-hardened die steel plate with thickness of 201-300mm and manufacturing method thereof

The invention relates to a free-cutting pre-hardened die steel plate with the thickness of 201-300 mm and a manufacturing method of the free-cutting pre-hardened die steel plate. The steel plate comprises the following chemical components in percentage by mass: 0.35-0.45% of C, 0.20-0.40% of Si, 1.30-1.60% of Mn, 1.80-2.10% of Cr, 0.20-0.40% of Mo, less than or equal to 0.015% of P, 0.050-0.100% of S, 0.02-0.30% of V, Ti and B and the balance of Fe and inevitable impurities. A continuous casting plate blank with the thickness of 450 mm is rolled into a material, through a reasonable heating schedule and a rolling process, particularly a cooling mode of'water cooling rack + air cooling 'and tempering after normalizing, the free-cutting pre-hardening die steel plate with the thickness of 201-300 mm, the width of 2000-2300 mm and the length of 6000-12000 mm is obtained, the core hardness is not lower than 30 HRC, the section hardness difference is within 2.5 HRC, and the NB/T 47013.3 TI is qualified through flaw