High-performance hot work die steel and manufacturing technology thereof

Abstract

The invention relates to high-performance hot work die steel and manufacturing technology thereof. The high-performance hot work die steel comprises, by mass percent, 0.20%-0.30% of C, 0.40%-0.80% ofSi, 0.40%-0.80% of Mn, 3.10%-4.00% of Cr, 1.60%-2.00% of Mo, 0.5%-1.00% of W, 0.10%-0.30% of V, smaller than 0.010% of P, smaller than 0.005% of S and the balance Fe. The manufacturing process of thedie steel includes the following steps that burdening, smelting and pouring are conducted; then electroslag remelting is conducted; high-temperature diffusion heat treatment is conducted, then multidirectional forging hot working is conducted, and controlled cooling is conducted after forging; then secondary carbide refining heat treatment and isothermal annealing treatment are conducted; and finally, quenching and tempering heat treatment are conducted. The high-performance hot work die steel and manufacturing technology thereof have the beneficial effect that the quenching degree, the heat stability, the impact toughness and the thermal fatigue performance of the hot work die steel are superior to H13 steel, the hot work die steel can be machined into large die casting dies with the weight of the single piece reaching 5 tons or higher, and the good use performance is achieved; and in addition, the steel ingot smelting cost can be reduced, and the service life of dies is prolonged.

Description

technical field [0001] The invention belongs to the technical field of alloy steel, relates to a hot work die steel, in particular to a [0002] A high-performance hot work die steel and its manufacturing process. Background technique [0003] Hot work die steel is a die steel used at higher temperatures (generally higher than 500 ° C), in which the alloying elements that play high temperature thermal strength and thermal stability are usually Cr, Mo, V and other alloying elements, so the current Some of the research work is mainly on the adjustment of these alloying elements. This study found that the addition of a higher content of Mo element can improve the thermal fatigue resistance and temper softening resistance of steel, and the addition of a certain amount of W element can greatly improve the thermal stability and thermal fatigue resistance of steel, so that The service temperature of the steel is greatly increased, so it is used to manufacture hot-work die steel w...

AI Technical Summary

Problems solved by technology

4Cr5MoSiV1 steel is the most widely used hot work die steel, but its high temperature strength is not very high, the general use temperature can not exceed 540 ℃, and the thermal fatigue resistance and thermal stability are not high

This manufacturing process has the following problems: 1) The size of the electroslag ingot is small, and the small ingot size reduces the yield and manufacturing capacity of the product; 2) The original structure of the electroslag ingot has a large number of large particles or large blocks of liquefied carbonization 3) The grain size of the material after forging is coarse, resulting in low impact toughness of the material after quenching and tempering, and the product grade is low, which cannot meet the market demand for large cross-section, high toughness, and high heat. The need for strong hot work die steel; 4) The hydrogen expansion annealing time after forging is long, and it is prone to flaw detection defects such as white spot cracks

[0006] In view of the above phenomenon, the patent CN 107557667 A discloses a high-performance hot-working die steel for large die-casting molds and its manufacturing process. The composition and mass percentages of the high-performance hot-working die steel are as follows: C 0.20~ 0.30%, Si≤0.40%, Mn 0.30~0.60%, Cr 4.10~4.50%, Mo 2.10~2.30%, W0.10~0.20% , V 0.40~0.80%, P<0.01%, S<0.005%, Nb 0.02~0.04%%, Fe balance; the manufacturing process of the mold steel of the present invention is as follows: Ingredients , smelting, pouring, and then electroslag remelting; high temperature diffusion heat treatment, then multi-directional forging heat processing, and controlled cooling after forging; then secondary carbide refining heat treatment and isothermal annealing treatment; finally quenching and tempering Pyrothermal treatment; the hardenability, thermal stability, impact toughness and thermal fatigue performance of the hot work die steel of this invention are superior to H13 steel, and can be processed into large die-casting molds with a single piece weight of more than 5 tons, with good performance But this invention patent still has certain defects: the content of Cr, Mo and V alloy elements is relatively high in this invention, so that the content of MC type carbide in the steel grade is low; Under the action of mechanical stress, etc., it is easy to aggregate and grow, leading to early thermal fatigue failure of the mold, thereby reducing the service life of the mold; in addition, the price of vanadium-ferroalloy is as high as 500,000 yuan per ton, which makes the cost of ingot smelting high

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