Heat Treatment Process for Improving Spheroidized Structure of Large Die Flat Steel Forgings

Abstract

The invention discloses a heat treatment process for improving the spheroidized structure of a large-sized die flat steel forged material. The purpose is to improve the spheroidized microstructure of the forged material. The process combination of post-forging red sending annealing material waiting+superfine treatment+isothermal spheroidizing annealing treatment is designed. Precipitation of secondary net carbide can be reduced through post-forging red sending annealing material waiting, and preparation is made for subsequent superfine treatment and isothermal spheroidizing annealing. During superfine treatment, normalizing heating adopts one time of preheating, complete burning of steel is ensured, inner and outer temperatures are uniform, normalizing cooling adopts water and air alternate cooling, cooling intensity is improved, thus coarse grains produced by high-temperature forging are refined, the net carbide structure is eliminated, and then small and uniform globular pearlites and a few of dispersively distributed granular carbide are obtained through isothermal spheroidizing annealing. The heat treatment process has the following beneficial effects that with the adoption of the treatment process, the coarse structure of the steel is eliminated, structure uniformity is improved, the carbide level is improved, and the microstructure reaches the AS1-AS4 level.

Description

technical field [0001] The invention relates to the field of post-forging heat treatment of large-size die flat steel, in particular to a heat treatment process for improving the spheroidized structure of large-size die flat steel forgings, and in particular to 1.2344 die flat steel. technical field [0002] The invention relates to the field of post-forging heat treatment of large-scale mold flat steel, in particular to a heat treatment process for improving the spheroidized structure of large-scale mold flat steel 1.2344 forging. Background technique [0003] 1. 2344 hot work die steel has good thermal strength, red hardness, high toughness, thermal fatigue resistance and thermal crack resistance, and is mainly used in forging dies, hot extrusion dies, die-casting dies and other fields. The spheroidized microstructure of 1.2344 mold flat steel produced by Fushun Special Steel Co., Ltd. is between AS8-AS9 according to the rating of NADCA#207 of the North American Die Cast...

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Problems solved by technology

The spheroidized microstructure of 1.2344 mold flat steel produced by Fushun Special Steel Co., Ltd. is between AS8-AS9 according to the rating of NADCA#207 of the North American Die Casting Association, such as figure 2 , image 3 ;With the development of the mold industry, the demand for large-size molds is increasing day by day, and the environment in which the molds are used is becoming more and more harsh, and the service life of the molds has attracted more and more attention from users. Equally seriously affect the service life of the mold

At present, the ways to improve the spheroidizing structure of 1.2344 series hot work die steel are normalizing after forging + isothermal spheroidizing annealing, but due to the low cooling intensity of normalizing, the effect is not bad for small-sized bars or modules, but for large-sized forged As for the forged material, due to the large size and the current cooling method, the core is prone to precipitate network carbides, and the spheroidized structure level is poor, resulting in uneven structure of the forged material, which affects later use.

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