Niobium microalloyed high strength hot work die steel and preparation thereof

Abstract

The invention relates to niobium microalloyed high-strength hot working die steel, belonging to the alloy steel manufacturing process technical field. The compositions by weight percentage of the steel are: 0.3 to 0.6 percent of C, 0.1 to 0.5 percent of Si, 0.1 to 0.5 percent of Mn, 4.0 to 6.5 percent of Cr, 1.0 to 3.5 percent of Mo, 0.4 to 1.4 percent of V, 0.02 to 0.10 percent of Nb, less than 0.03 percent of P, less than 0.03 percent of S, and the balance being Fe. The process for preparing the hot working die steel comprises the following steps of: batching, smelting, secondary refining and electroslag remelting; homogenizing the mixture for 5 to 10 hours at a temperature of between 1210 and 1300 DEG C, and forging, annealing, quenching and tempering the mixture; heating up the mixture to a temperature of between 1000 and 1100 DEG C for austenization, after performing 'step heating' at a temperature of 650 DEG C and at a temperature of 800 DEG C, then performing secondary tempering to the processed mixture, and finally acquiring the hot working die steel. The die steel has the advantages of good thermal resistance, good thermal stability and good thermal fatigue performance.

Description

technical field [0001] The invention relates to a niobium micro-alloyed high-strength hot work die steel and a preparation method thereof. The die steel has high strength and high thermal stability, good toughness and thermal fatigue performance, and belongs to the technical field of alloy steel manufacturing technology. Background technique [0002] In the field of hot work die steel, the steel types widely used in China are 5CrNiMo, 5CrMnMo, 3Cr2W8V and H13 steel. Due to the particularity of the working conditions of hot work die steel, the performance requirements for hot work die steel are also very strict. Due to their low thermal strength, 5CrNiMo and 5CrMnMo are likely to cause the collapse of the working part of the mold, thermal wear and thermal fatigue under impact stress, and are not suitable for manufacturing hot-working molds with larger sizes and higher working temperatures. 3Cr2W8V has good thermal hardness, but its thermal fatigue resistance is poor, and the...

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Problems solved by technology

5CrNiMo and 5CrMnMo, due to their low thermal strength, are likely to cause the collapse of the working part of the mold and thermal wear and thermal fatigue under impact stress, so they are not suitable for manufacturing hot-working molds with large sizes and high working temperatures

3Cr2W8V has good thermal hardness, but its thermal fatigue resistance is poor, and the mold often fails due to cracks

If the amount of niobium added is too much, it is easy to produce more large-grained pseudoeutectic carbides during the solidification of molten steel, which will seriously affect the impact toughness of the steel. If the amount of niobium added is too small, the effect will not be obvious.

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