The processing technology of cryogenic treatment equipment
2023-01-03 14:42:02
The processing technology of cryogenic treatment equipment
For cryogenic treatment (cryogenic treatment equipment) technology, the treatment process is the key to determine the treatment effect. The key influencing factors in cryogenic treatment process mainly include: cryogenic treatment mode, rising and cooling speed, pre-tempering or post-tempering treatment, holding time, cryogenic frequency, etc.
It can be divided into liquid method and gas method. The liquid method is to place the workpiece directly into liquid nitrogen at a temperature of -150 ℃. The disadvantage of this method is that the heat impact is high and sometimes even causes the workpiece to crack. Gas method is through the latent heat of liquid nitrogen vaporization and low temperature nitrogen heat absorption to refrigeration, treatment temperature up to -196 ℃, the treatment effect is good.
3, rising and cooling speed
At present, there are two main views on the rise and fall rate of deep cooling. One view is that the rise and fall rate of deep cooling should not be too fast, that is, it is not in favor of immersing the workpiece directly in liquid nitrogen, because the intense cooling will lead to the increase of the stress inside the workpiece, easy to cause deformation or cracking of the workpiece. For example, in Japan's "cryogenic and rapid heating method", the workpiece is not cold-treated immediately after quenching, but is first put into a water bath and then into a treatment tank for cold treatment at -80℃ or -180℃. After holding for a period of time, the workpiece is immediately put into a 60C hot water bath to make the sample quickly return temperature to reduce the internal stress, and then tempering at different temperatures for 1h.
The other view is that it should be cooled or heated up quickly, which will make austenite more easily converted into martensite, and the cooling rate of direct immersion is slower than that of oil quenching, which is not easy to cause deformation or cracking of the material. For example, the "impact method" of the former Soviet Union, the processed workpiece is directly and quickly put into liquid nitrogen, cooled to the required temperature, held for 5~ 30min, and then taken out at room temperature, after it is restored to room temperature, and then tempered in oil at 200~ 500℃ for 1h. This method can obviously prolong the service life of high speed steel tool.
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