On 2018-08-08 14:48:54
Heat treatment techniques
Do you know the vacuum furnace? Vacuum furnace plays an irreplaceable role in mold production, mainly used in ceramic firing, vacuum smelting, degassing of electric vacuum parts, annealing, brazing of metal parts, and ceramic metal sealing. The vacuum heat treatment of vacuum furnace can realize almost all the heat treatment processes, such as quenching, annealing, tempering, carburizing, nitriding. In the quenching process, it can realize air quenching, oil quenching, nitrate quenching, water quenching, etc. it can also carry out vacuum brazing, sintering, surface treatment, etc. The vacuum furnace has high thermal efficiency, can realize rapid temperature rise and temperature drop, can realize no oxidation, no decarburization, no carburization, can remove the phosphorus chips on the surface of the workpiece, and has the function of degreasing and degassing, so as to achieve the effect of surface bright purification.
Generally speaking, the workpiece to be processed is heated slowly in the furnace, the internal temperature difference is small, the thermal stress is small, and therefore the deformation is small. The qualified rate of products is high. The utility model can reduce the cost and has the function of degassing, thereby improving the mechanical performance and service life of the work. Good working environment, safe operation, no pollution and public hazards. There is no danger of hydrogen embrittlement in the treated workpieces. It can prevent hydrogen embrittlement on the surface of titanium and refractory metal shell. The vacuum heat treatment process has good stability and repeatability. This series of advantages, the development of vacuum heat treatment equipment and technology has been more and more attention and application more and more widely.
Vacuum heat treatment is a comprehensive technology combining vacuum technology and heat treatment, which means that all and part of the heat treatment process are carried out in vacuum state. China divides vacuum into low, medium, high and ultra-high vacuum.
Vacuum furnace and medium frequency electric furnace have a good development prospect in the field of hot working. They are used for induction heating of diathermy, rolling, forging, bending, heat treatment (quenching), welding and other processes. So what are the heat treatment skills of vacuum furnace and medium frequency electric furnace?
1. When titanium alloy is treated in vacuum furnace, nitrogen should not be used as cooling gas, because titanium and nitrogen react at high temperature to form golden titanium nitride.
2. The movable connection part of the vacuum furnace is all sealed with O-ring, and this part is cooled by water.
3. When the workpiece is quenched in vacuum, vacuum quenching oil shall be used, which has low saturated vapor pressure.
4. The maintenance of the vacuum furnace shall be in the state of vacuum or pure nitrogen filling to avoid air absorption and moisture absorption when not in use.
5. The pressure rise rate of domestic vacuum furnace shall not be greater than 1.33pa/h, and that of some foreign enterprises shall be 0.67pa/h
6. Vacuum heating is mainly based on radiation, and the distance between workpieces in the furnace should be kept.
7. During the heating process, the workpiece and furnace materials will be deflated to reduce the vacuum.
8. The heating temperature of vacuum tempering, vacuum annealing, vacuum solution treatment and vacuum aging is generally the same as that of conventional treatment.
9. The vacuum tempering furnace shall be equipped with quick cooling device. The pressure of cooling water shall be greater than 0.2MPa, and the flow shall be adjustable.
10. Cooling gas: generally, 99.995% pure nitrogen is used for steel, 99.999% nitrogen or argon is used for superalloy and 99.995% argon is used for titanium alloy.
11. Temperature rise: after the workpiece is put in, it can be heated only when it is pre pumped to 6.67pa.