Thermal treatment method for die steel

Abstract

The invention belongs to the technical field of die steel and particularly relates to a thermal treatment method for large CG738 plastic die steel. The method comprises the steps of a, heating at the temperature of 870-930 DEG C for 8-26h; b, quenching: carrying out quenching thermal treatment, namely firstly taking steel out of a furnace to carry out air cooling for 2-3min, and carrying out mist cooling for 2-4min, then, carrying out spray cooling until the surface temperature reaches 600 DEG C, then, carrying out air cooling for 3-5min, next, further carrying out spray cooling to 200 DEG C, and taking the steel out of a thermal treatment tank to carry out air cooling; and c, tempering at the temperature of 520-600 DEG C for 12-34h, wherein the hardness of a cross section is 33-35HRC. According to the thermal treatment method for large CG738 plastic die steel, disclosed by the invention, a different-medium multi-quenching process is adopted, so that the refining grades of grains inside and outside a workpiece are basically consistent, the structure and section hardness value uniformity of the CG738 plastic die steel can be improved, the temperature and time parameters can be regulated according to the size and thickness of a section, and a product can keep relatively high performance and dimensional stability in actual production.

Description

technical field [0001] The invention belongs to the technical field of die steel, and in particular relates to a large-scale CG738 die steel heat treatment method. Background technique [0002] The characteristics of large forgings are: large shape and heavy weight, high quality requirements during production, only single piece and small batch production, and long production cycle and strict technical conditions. In my country's current heavy equipment manufacturing industry, there is a great demand for large-scale forgings, and the quality requirements are also high, especially all kinds of high-strength and high-precision forgings still need to be imported, which has become the development trend of my country's heavy equipment manufacturing industry. one of the bottlenecks. [0003] The production of large forgings has to go through many processes from smelting, ingot casting, forging, post-forging heat treatment to performance heat treatment, and each process affects the ...

AI Technical Summary

Problems solved by technology

The widely used plastic mold steel CG738 has put forward new requirements, otherwise it can only be replaced by imported high-performance steel, so the heat treatment process of CG738 steel needs to be further optimized and improved

[0005] The publication number is "CN105695703A", and the title of the invention is "A Die Steel Heat Treatment Process". It discloses a two-fire direct heat treatment process method of 7Cr7Mo2V2Si high-strength and toughness cold-work die steel preparatory heat treatment and quenching and tempering. From the parameters introduced Look, only the hardness and wear resistance of the mold steel have some effect, but it is difficult to achieve the same cooling rate control in the internal and external heat treatment process of the material, and it is difficult to guarantee the uniformity of structure and performance

[0006] The application number is "200610049263.7", the title of the invention is "a new type of chromium steel mold steel and its heat treatment process", which discloses a manufacturing method of Cr8Mo2V1Si mold, and then briefly describes its heating temperature and heat preservation after three-fire heating Time parameters, it is difficult to reflect the control of quenching speed, and the guarantee of control uniformity is not reflected

[0007] The application number is "201410721290.9", and the title of the invention is "A 3Cr2Mo Die Steel Heat Treatment Process", which discloses a 3Cr2Mo die steel heat treatment process operation steps, which also utilizes the early high-temperature annealing plus quenching and tempering, and carburizing processes. Classified as a heat treatment process of two-fire or three-fire heating, the focus is to improve the surface thermal hardness and wear resistance, and the uniformity control and internal and external differences cannot be reflected and realized.