Vacuum Hardening Stainless Steel

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Vacuum heat treatment of martensitic stainless steel

Martensitic stainless steel has good vacuum heat treatment performance, and various mechanical properties such as strength and hardness can be obtained through vacuum heat treatment, and the adjustable range is extremely large. Vacuum heat treatment processes such as vacuum annealing, vacuum hardening and vacuum tempering are mainly used.

(1) Vacuum annealing

The purpose of vacuum annealing of martensitic stainless steel is to soften the structure and facilitate processing and forming. During vacuum annealing, in order to prevent deformation, the heating rate should not be too fast. The usual heating rate is 150~200°C/h, and the holding time is calculated according to the thickness or diameter of the material (about 1 hour per 25mm). There are two kinds of complete vacuum annealing and low temperature vacuum annealing. During complete vacuum annealing, the heating temperature is 800~900°C, and the cooling rate should be as small as possible, generally lower than 20°C/h. During low-temperature vacuum annealing, the heating temperature is about 750°C, and continuous air cooling is generally carried out.

(2) Vacuum hardening

The purpose of vacuum hardening of martensitic stainless steel is to improve strength and hardness. It is to heat the stainless steel above the phase transition temperature, generally 1000~1100°C, and usually the heating rate is 150~200C/h. The heat preservation time is calculated according to the thickness or diameter of the material, about 1 hour per 25mm. It is then rapidly cooled in a vacuum hardener.

(3) Vacuum tempering

The purpose of vacuum tempering of martensitic stainless steel is to improve toughness and eliminate internal stress. It is to heat the stainless steel below the phase transition temperature, the heating rate is usually 150~200°C/h, the holding time is calculated according to the thickness or diameter of the material (about 25mm for 1h), and then air cooling is used.

In fact, the vacuum heat treatment of martensitic stainless steel is the same as that of structural steel. For example: when used in high-strength structural parts, quenching and tempering treatment is required; when used in spring components, vacuum hardening and medium temperature vacuum tempering are required.

Ferritic stainless steel vacuum heat treatment

The most important steel type of ferritic stainless steel is Cr17 steel. Since the chromium content increases to about 17%, there is no a-v transformation when heated, but the ferrite single-phase state is always maintained. This type of stainless steel cannot be strengthened by martensitic transformation. That is, vacuum hardening-vacuum tempering cannot be performed. Therefore, the strength is low and the plasticity is relatively good. Sometimes in order to eliminate the processing stress, soften the structure and eliminate the tendency of intergranular corrosion, appropriate vacuum annealing treatment can also be carried out. Generally, the heating temperature is 750~800°C, the holding time is 1~2h, or the holding time is calculated according to the thickness of 1.5min/mm, and the cooling method is air cooling.

Vacuum furnace selection: SIMUWU’s vacuum hardening furnace is an industrial furnace for heat treatment of metal parts. They operate at reduced atmospheric pressure, providing a controlled environment for the heat treatment process. Vacuum hardening is used to improve the mechanical properties of metal parts, including their strength, toughness, and resistance to wear and corrosion. SIMUWU company focuses on the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum tempering furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.

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