The quenching oil heats the metal material above the phase transition temperature, and after being kept for a period of time, it is quickly put into the medium to be cooled to obtain a martensite structure. This operation process is called quenching. The cooling of the steel in the medium is carried out in three different ways.
1. Vapor film stage. The cooling rate at this stage is very low. As the cooling time is extended, the temperature of the part is continuously decreased, and the stability of the vapor film is gradually lowered, and then the vapor film is broken and enters the boiling stage.
2. The boiling stage. When the vapor film breaks and disappears, the quenching medium is brought into direct contact with the surface of the part, and the quenching medium draws a large amount of heat from the part. The flow of the quenching medium is hindered, and the medium that absorbs heat continuously escapes a large number of bubbles, and the new medium continues to boil vigorously around the parts to form a boiling stage, at which time the cooling rate is large. As the temperature of the parts continues to drop, the boiling phenomenon gradually disappears. When the temperature of the part is lower than the boiling point of the quenching medium, the boiling phenomenon disappears immediately and then the convection heat transfer stage is transferred.
3. Convective heat transfer stage. When the part is in the boiling stage, the temperature of the surrounding quenching medium is close to the temperature of the part, and the temperature of the medium away from the part is lower. Since the quenching medium around the part is different from the temperature of the medium in other places, the quenching medium is convective.
The above is the quenching oil manufacturer’s cooling principle for quenching oil.
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