Abstract: A die steel with a high thermal diffusion coefficient includes 0.30-0.40 wt. % of C, 0.05-0.10 wt. % of Si, 2.50-3.40 wt. % of Mo, 0.01-0.05 wt. % of Nb, 0.30-0.50 wt. % of Co, 0.01-0.05 wt. % of RE, the rest is Fe and unavoidable impurities, wherein in the die steel, P?0.15 wt. %, S?0.025 wt. %. A preparation method of the die steel includes steps of melting, electroslag remelting, electroslag ingot annealing, forging, spheroidizing annealing, quenching and tempering.

Abstract: A method for preparing a Bainite hot-working die, includes: 1) weighing and mixing alloy raw materials including: C: 0.50-0.60%, Si: 0.20-0.25%, Mn: 1.00-1.50%, W: 2.10-3.00%, Mo: 3.50-5.00%, V: 0.50-1.00%, Co: 0.60-1.10%, P?0.02%, rare earth (RE): 0.01-0.10%, (RE)/(S)>3.0, (RE)×(S)<0.004%, the balance being Fe and impurities; smelting, casting, annealing the alloy raw materials, to yield steel billets; 2) forging the steel billets to obtain Bainite die billets; 3) mechanically roughening the Bainite die billets, to yield die inserts; 4) tempering the die inserts, to yield hardened Bainite die inserts through secondary strengthening of Bainite; 5) mechanically machining the hardened Bainite die inserts to yield precisely sized die inserts; 6) nitriding the precisely sized die inserts; and 7) assembling the die inserts to yield a Bainite hot-working die.