Precise heat treatment and quenching technology of precision part of high-purity hot-work die steel

Abstract

The invention discloses a precise heat treatment and quenching technology of a precision part of high-purity hot-work die steel, and belongs to the field of special steel heat treatment. The high-purity hot-work die steel ASSAB 8407 material imported from Sweden is aimed, wherein the material mainly comprises the following components of 0.39% of C, 5.2% of Cr, 0.1% of Si, 1.4% of Mo, 0.9% of V, and the precise heat treatment and quenching technology is provided. In the heat treatment process, different tempering temperatures are adopted to obtain accurate hardness; different heat treatment time is adopted for workpieces with different thicknesses, so that crystal grain changes inside the material can be accurately controlled, grain refinement can be kept, the structure is uniform, the workpiece of a die can obtain high impact toughness and high wear resistance; according to the technical scheme, the method comprises the following steps that (1) the workpiece with the thickness difference smaller than 5 mm is placed into a quenching furnace, and the workpiece is preheated to 150 DEG C in a heating rate of less than 75 DEG C per hour; (2) two level heating is carried out in the quenching furnace to the quenching temperature of 1020 DEG C and the temperature is kept according to heating preservation time t2; (3) the workpiece is discharged out of the furnace and is air-cooled andquenched; and (4), the workpiece is put into a tempering furnace two times for tempering, and tempering temperature T DEG C is carried out according to tempering heat preservation time t3 and t4 (FIG.1).

Description

Technical field [0001] The invention belongs to the field of heat treatment of special steel materials, and specifically relates to a precise heat treatment quenching process for precision parts of high-purity hot work die steel. Background technique [0002] With the upgrading of China's manufacturing industry, some precision equipment has more and more stringent requirements for parts and components. Domestic materials cannot meet their requirements in certain performances, so relevant advanced imported materials have to be used; ASSAB 8407 is a Swedish brand and belongs to hot work. Die steel, its main alloy composition is 0.39%C 5.2%Cr 0.1%Si 1.4%Mo 0.9%V. After vacuum degassing and electroslag remelting, the steel has high purity, finer structure and better toughness. Heat treatment Uniform hardness, high thermal strength and thermal wear resistance, good thermal conductivity, thermal fatigue resistance, insensitive to thermal cracking, high hardenability and high toughness,...

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Problems solved by technology

[0004] The alloy composition of ASSAB 8407 hot work die steel has a great influence on the heat treatment process, which leads to complicated heat treatment process. If the heat treatment is improper, it is not only difficult to exert its excellent performance, but also difficult to control the quality. Therefore, the inventor has declared a hot work die The heat treatment and quenching process patent for steel precision parts (application number 2017112188284) has achieved good results;

[0005] The cavity mold parts in the precision mold are made of ASSAB 8407 material. Due to the complex force of the mold during use, some working parts are required to have some special mechanical properties, precise hardness requirements and high-temperature working dimensional stability; but the material’s The volume, especially the thickness of the workpiece, has a great influence on the grain growth, size distribution, uniformity and hardenability of the heat treatment. The empirical formula t=αКН is often used to estimate the holding time in the heat treatment process according to the thickness of the workpiece. Not only It is difficult to accurately and reliably control its quenching hardness, and it is also difficult to accurately and reliably control the change of crystal phase structure inside the material. A small amount of retained austenite is unstable when heated, resulting in creep of the parts during the working process, and the ideal working performance and mold cannot be achieved. Optimum working condition; this requires precise heat treatment temperature and time process parameters according to different workpiece thicknesses and different hardness requirements to precisely control the internal structure changes, carbide precipitation, and grain growth of the material to ensure minimal The retained austenite and residual stress

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