Common sense of vacuum heat treatment
Common sense of vacuum heat treatment
Vacuum heat treatment means that all and part of the heat treatment process is carried out in a vacuum state, and the quality of the heat treatment is greatly improved. Compared with conventional heat treatment, vacuum heat treatment can achieve no oxidation, no decarburization, and no carburization. It can remove phosphorous chips on the surface of the workpiece, and has the functions of degreasing and degassing, so as to achieve the effect of surface bright purification.
Share some tips on vacuum heat treatment:
1. When disposing of titanium alloy in a vacuum furnace, it is not advisable to use nitrogen as the cooling gas, because titanium and nitrogen react at high temperatures to form golden yellow titanium nitride.
2. The vacuum furnace movable connection, some of which are all sealed and connected by O-shaped rubber rings, and some of them are cooled by water.
3. When the workpiece is quenched in a vacuum state, vacuum quenching oil should be used, which has a lower full vapor pressure.
4. The protection of the vacuum furnace should be in the state of vacuum or pure nitrogen to prevent inhalation and moisture absorption when not in use.
5. The pressure rise rate of the domestic vacuum furnace should not be greater than 1.33Pa/h, and the specification of some foreign companies is 0.67Pa/h.
6. Vacuum heating is mainly based on radiation, and the workpiece will probably maintain a distance in the furnace.
7. During the heating process, the workpiece and the materials in the furnace will outgas, which will reduce the vacuum degree.
8. The heating temperature for vacuum tempering, vacuum annealing, vacuum solution treatment and vacuum aging is usually the same as the heating temperature for conventional treatment.
9. The vacuum tempering furnace probably has fast cooling equipment. The pressure of the cooling water is probably greater than 0.2Mpa and the flow rate should be adjustable.
10. Cooling gas: Nitrogen with a purity of 99.995% is usually used for steel, nitrogen or argon with 99.999% for high temperature alloys, and argon with 99.995% for titanium alloys.
11. Heating up: After the workpiece is placed, it is usually pre-pumped to 6.67Pa before heating up.
After the parts are subjected to vacuum heat treatment, the distortion is small, the quality is high, and the process itself is flexible and pollution-free. Therefore, vacuum heat treatment is not only a necessary means for heat treatment of certain special alloys, but also used in the heat treatment of general engineering steels, especially tools, molds and precision couplings.
