Advantages of vacuum heat treatment
(1) bright quenching can be realized
The workpiece below atmospheric pressure heating, not exposed to air, the surface will not change, when the vacuum furnace is pumped to 1 ~ 10-1Pa, the surface of the workpiece to achieve no decarburization, carburization purposes, so as to achieve the purpose of light quenching.
When the vacuum is lower than the corresponding decomposition pressure of metal or alloy, its oxide will decompose, the free oxygen formed and immediately discharged out of the vacuum, so that the internal quality of the workpiece is improved. The billets of iron and steel parts will absorb a small amount of hydrogen, nitrogen, carbon monoxide and other gases in the atmosphere during smelting, resulting in tiny pores, which can easily lead to hydrogen embrittlement and other defects. The hard alloy will also enter air when it is pressed. So for the mould steel, the vacuum technology can be residual gas inside the workpiece she removed, the organization. For cemented carbide, the residual gas in the workpiece can also be removed by vacuum treatment.
(3) the machining allowance can be reduced after heat treatment
Vacuum heat treatment because no decarburization phenomenon, little distortion and clean the light, so that it is widely used in GCr15, W6Mo5Cr4V2, 27SiMnMoVA vacuum quenching fuel injection equipment and vacuum carburizing, this can avoid using salt bath furnace inner hole caused even sometimes because of the residual salt cleaning Bugan net or protective atmosphere caused by surface decarburization (black organization the phenomenon of needle valve) for 27SiMnMoVA steel for the 0.5 ~ 0.9mm layer with vacuum carburizing carburizing can be ensured, and controlled atmosphere furnace carburizing is difficult to be guaranteed. For piston pump and other precision hydraulic parts, vacuum quenching can reduce distortion, improve wear resistance, and ensure the quality stability of workpiece.
(4) cleaning process
Vacuum heat treatment is a clean heat treatment process, it plays an important role in the whole process of heat treatment, it can improve the quality of products, can change the face of the heat treatment workshop, improve the operating environment, is a worthy of popularization and application of technology.
Vacuum heat treatment medium
The auxiliary materials for vacuum heat treatment are loading rack (basket) and loading plate, nitrogen and quenching medium. The loading rack (basket) and the loading plate need to be made of heat-resistant steel, such as 40Cr25Ni20, and nitrogen is recommended to be better than liquid nitrogen with content > 99.995%, because liquid nitrogen can ensure the purity of nitrogen, and the operation and maintenance is convenient. Vacuum heat treatment with vacuum quenching oil specially, it is suitable for less than atmospheric conditions, the short range, saturated vapor pressure, strong antioxidant capacity, not volatile, easy vacuum. The light of easy cleaning, less oil consumption. The advantages of good thermal oxidation stability, stable cooling performance, long service life and so on. Therefore, after quenching the workpiece hardness uniformity is good, less distortion and clean bright.