Production process of stainless steel vacuum heat treatment

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The vacuum heat treatment of stainless steel can be used for annealing, solid solution, quenching, tempering, stress relief and other treatments according to different steel grades.

(1) Selection of equipment. There are different types of vacuum heat treatment furnaces (vertical, horizontal, combined, etc.), different heating sources (resistance heating, induction heating, electron beam heating, plasma heating, etc.), different heating methods (external heating, internal heating, etc.). It can be divided into low temperature furnace (≤ 700 ℃), medium temperature furnace (> 700-1000 ℃), high temperature furnace (> 1000 ℃), low vacuum (1.33 × 103-13.3pa), medium vacuum (13.3-1.33 × 10-2Pa), high vacuum (1.33 × 10-2-1.33 × 10-4Pa), ultra-high vacuum (above 1.33 × 10-4Pa).

For the vacuum heat treatment of stainless steel, it is mainly considered that the equipment is easy to operate, the system is safe and reliable, and the limit vacuum degree can reach 13.3-1.33 × 10-2Pa to meet the use requirements. Higher limit vacuum will increase the cost of equipment. The pressure rise rate shall not be greater than 0.6pa/h, the temperature uniformity shall be high, and the temperature difference shall not be greater than ± 5 ℃ generally, with air-cooled or oil-cooled devices that can meet the cooling needs.

(2) Key points of stainless steel vacuum heat treatment operation.
① Considering the heating characteristics of vacuum heat treatment, some gaps need to be reserved for stainless steel workpieces placed in the vacuum furnace to ensure that all surfaces of workpieces can be heat treated in place.

② As the heating process temperature of stainless steel workpiece is relatively high, usually above 1000 degrees, it is necessary to preheat the workpiece in the vacuum heat treatment furnace for a period of time at 800 degrees. After the stainless steel body gets a buffer to adapt to the high temperature, it will slowly rise to the temperature required by the process.

③ According to the process requirements, the stainless steel workpiece is heated in the vacuum heat treatment furnace for a certain time.

④ The adjustment of vacuum degree is also very important to the quality of heat treatment of workpieces, so it is necessary to select the vacuum degree reasonably according to the operation experience.

⑤ In order to improve the toughness of the workpiece, it is necessary to temper in the low temperature zone for a period of time after high temperature heat treatment.

⑥ After the vacuum heat treatment of stainless steel workpiece is finished and discharged from the furnace, appropriate methods such as air cooling, oil cooling and furnace cooling shall be adopted for cooling treatment.

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