In medium frequency quenching, the commonly used cooling media, i.e. quenching liquid, are as follows:
Water is suitable for parts with simple shape made of low hardenability steel for spray cooling.
(2) Polyvinyl alcohol aqueous solution
Polyvinyl alcohol aqueous solution is used for spray cooling, and its cooling capacity decreases with the increase of concentration. Usually, the concentration used in production is 0.05% - 0.3%. If the concentration is greater than 0.3%, the best use temperature is 32-43 degrees, generally not less than 15 degrees. Polyvinyl alcohol forms a film on the surface of parts during quenching, thereby reducing the cooling rate of water. In use, the concentration of PVA aqueous solution continues to decrease, and it needs to be supplemented frequently to maintain its required concentration.
The cooling capacity of polyvinyl alcohol aqueous solution is low, which is suitable for parts made of low alloy steel and parts made of carbon steel with complex shape, and has an effect on preventing the cracking of these parts
(3) Polyacrylamide aqueous solution
Polyacrylamide aqueous solution (commonly used components are 0.35% - 0.45% polyacrylamide, 0.1% triethanolamine, 0.1% sodium nitrite, and the rest are water) is used for spray cooling. Its cooling capacity is low, and the concentration of polyacrylamide aqueous solution continues to decline during the application process. It should be supplemented frequently to maintain the required concentration. Polyacrylamide aqueous solution is suitable for parts made of low alloy steel and parts made of carbon steel with complex shape, and has a good effect on preventing the cracking of these parts.
Emulsion (usually 3% concentration emulsion) is used for spray cooling. Its cooling capacity is low. It is suitable for parts made of low alloy steel and parts made of carbon steel with complex shape to prevent these parts from cracking.
Oil is generally used for alloy steel immersion cooling. When using oil, good ventilation and fire-fighting conditions must be provided, and it can also be used for spray cooling. When oil quenching is adopted, oil injection device or oil agitator is generally set in the oil to forcibly cool the oil.