High-heat-resistance and high-impact-toughness hot-work die steel for hot forging and preparation method

Abstract

The invention discloses high-heat-resistance and high-impact-toughness hot-work die steel for hot forging and a preparation method thereof, and belongs to the technical field of die steel. The die steel comprises the following chemical components, by weight ratio: 0.40-0.50% of C, 0.30-0.60% of Si, less than or equal to 0.006% of S, less than or equal to 0.01% of P, 0.60-0.9% of Mn, 1.80-2.80% ofMo, 3.00-3.80% of Cr , 0.40-0.60% of V, 0.80-1.40% of Ni, 0.3-0.6% of Al, 0.50-1.10% of Co, 0.002-0.008% of rare earth elements and the balance Fe and inevitable impurities. The preparation method comprises the steps that steel is subjected to smelting and ingot casting, after a prepared steel ingot is subjected to high-temperature diffusing heat treatment, multi-directional forging and hot working are carried out, controlled cooling after forging is carried out, microstructure homogenization is carried out, refining heat treatment is carried out, and isothermal annealing treatment is carriedout. The die steel has the advantages of being relatively high in heat resistance, impact toughness and hardenability and particularly suitable for manufacturing a hot-work die with high heat resistance and impact toughness and with the large cross section with the thickness of 400mm or larger.

Description

technical field [0001] The invention belongs to the technical field of die steel, in particular to a hot work die steel with high thermal strength and high impact toughness for hot forging and a preparation method thereof. It is suitable for the manufacture of large cross-section hot forging dies that require high thermal strength, high temperature tempering stability, high hardenability and impact toughness. Background technique [0002] Hot work die steel is an important part of die steel. Among them, hot forging die steel is used for solid metal forming above the recrystallization temperature, and occupies a considerable proportion in hot work die steel. At present, almost all major stress-bearing components are produced by hot forging, especially in various fasteners, standard parts, automobile engines, aircraft and other manufacturing industries, which rely heavily on the hot forging process sex. With the widespread application of high-speed, high-load, high-precision...

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Problems solved by technology

5CrNiMo steel has a certain advantage in impact toughness due to the small amount of alloy elements, but due to insufficient hardenability, high temperature heat strength is generally insufficient, and the service temperature of the mold cannot be higher than 500 ° C, which affects the overall thermal fatigue resistance of the mold Therefore, the general service life of most 5CrNiMo hot forging dies is only 6000-7000 times, which seriously affects the production efficiency and economic effect of die users; the hardenability and strength of 5CrNiMoV steel are slightly higher, but still Unable to meet the thermal strength and service life requirements of large cross-section hot forging dies

Small and medium-sized hot forging dies (section thickness less than 400mm) have slightly lower toughness requirements. At present, more than 80% of H13 steels are generally used. Although H13 steels are widely used, but the service temperature is lower than 600°C, there is still the problem of insufficient thermal strength. In the actual application process, it still cannot meet the performance requirements of the precision forging die with strict cavity size requirements for the die material

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