Thermal treatment method of large die steel

Abstract

The invention belongs to the technical field of die steel and particularly relates to a thermal treatment method of large P20 plastic die steel. The method comprises the following steps: (a) heating, wherein the heating temperature is 860-920 DEG C, and the heating time is 9-24h; (b) quenching, wherein at least two of the four quenching media of air cooling, wind cooling, spray cooling and water cooling are adopted in the quenching thermal treatment; and (c) annealing, wherein the annealing temperature is 520-580 DEG C, the annealing time is 12-34h, and the cross section hardness is 33-35 / 33-36HRC. In the thermal treatment method of P20 die steel, a technology for performing repeated quenching by different media is adopted, the internal and external grain refinement levels of a workpiece are basically consistent, the structure and cross section hardness uniformity of P20 die steel can be improved, the temperature and time parameters can be adjusted according to the cross section size thickness, and relatively high performance and dimensional stability of the product can be maintained in practical production.

Description

technical field [0001] The invention belongs to the technical field of die steel, and in particular relates to a heat treatment method for large-scale P20 (3Cr2Mo) plastic die steel. 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 p...

AI Technical Summary

Problems solved by technology

The widely used plastic mold steel P20 has put forward new requirements, otherwise it can only be replaced by imported high-performance steel, so the heat treatment process of P20 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.