Die steel with a high thermal diffusion coefficient and its preparation methods

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.

1 . A die steel with a high thermal diffusion coefficient, the die steel comprising 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. %. 
     
     
         2 . The die steel with the high thermal diffusion coefficient according to  claim 1 , wherein a mass percentage content of RE and S in the die steel meets conditions of [RE]/[S]>2.0, [RE]×[S]<0.005 wt. %. 
     
     
         3 . A preparation method of the die steel with the high thermal diffusion coefficient according to  claim 1 , the method comprising steps of melting, electroslag remelting, electroslag ingot annealing, forging, spheroidizing annealing, quenching and tempering. 
     
     
         4 . The preparation method according to  claim 3 , wherein melting is performed in a range of 1450-1600° C. 
     
     
         5 . The preparation method according to  claim 4 , wherein melting is performed at 1530° C. 
     
     
         6 . The preparation method according to  claim 3 , wherein the step of electroslag ingot annealing comprises performing heat preservation on electroslag ingots obtained by electroslag remelting in a range of 750-800° C. for 8-10 h and then cooling to room temperature with an electric furnace. 
     
     
         7 . The preparation method according to  claim 6 , wherein the step of electroslag ingot annealing comprises performing heat preservation on electroslag ingots obtained by electroslag remelting at 780° C. for 9 h and then cooling to the room temperature with the electric furnace. 
     
     
         8 . The preparation method according to  claim 3 , wherein the step of forging comprises heating annealed ingots to 1150-1180° C., performing heat preservation for 30 min, and multi-directionally forging above 950° C. with a forging ratio no less than 6. 
     
     
         9 . The preparation method according to  claim 3 , wherein the step of spheroidizing annealing comprises performing heat preservation on forged ingots in a range of 650-750° C. for 12-16 h, and then cooling to room temperature with an electric furnace. 
     
     
         10 . The preparation method according to  claim 9 , wherein the step of spheroidizing annealing comprises performing heat preservation on the forged ingots at 700° C. for 14 h, and then cooling to the room temperature with the electric furnace. 
     
     
         11 . The preparation method according to  claim 3 , wherein the step of quenching comprises performing heat preservation on a die steel blank after spheroidizing annealing in a range of 1050-1150° C. for 1 h, and then performing oil-cooling to room temperature, and then tempering. 
     
     
         12 . The preparation method according to  claim 11 , wherein the step of quenching comprises performing heat preservation on the die steel blank after spheroidizing annealing at 1100° C. 
     
     
         13 . The preparation method according to  claim 11 , wherein the step of tempering comprises performing heat preservation on a die steel material after quenching in a range of 570-630° C. for above 2 h, and then performing oil-cooling to room temperature. 
     
     
         14 . The preparation method according to  claim 12 , wherein tempering is performed for twice. 
     
     
         15 . The preparation method according to  claim 12 , wherein the step of tempering comprises performing heat preservation on a die steel material after quenching at 600° C.