Compound microalloy hot die steel with high heat resistance and preparation method thereof

The invention relates to a compound microalloy hot die steel material with high heat resistance and a preparation method thereof, belonging to the technical field of the manufacture process of die steel. The invention is characterized by comprising the following components by weight percent: 0.25% to 0.4% of C, 1.0% to 1.8% of Si, 0.01% to 0.3% of Mn, 3.5% to 5.0% of Cr, 2.0% to 3.5% of Mo, 0.8% to 1.5% of V, 0.03% to 0.07% of Nb, 0.05% to 0.1% of rare earth element (Ce+La), less than 0.02% of P, less than 0.02% of S and the balance of Fe. The preparation method of the hot die steel comprises the process of: (1) adding rare earth after melting; (2) remelting electroslag; (3) homogenizing at high temperature; (4) forging and dissolving solid; (5) spheroidizing annealing; and (6) heating to finally prepare the hot die steel. The hot die steel has the advantages of high purity, high heat resistance, good heat stability and excellent heat fatigability.