How to choose proper quenching medium when forging?
2022-06-20
According to the material, mechanical properties and shape and size of the forgings, choose the appropriate quenching medium and reasonable quenching operation method, and have the appropriate cooling characteristics. On the premise of ensuring the quenching effect, the quenching medium with slow cooling capacity is selected to prevent the quenching deformation and quenching cracking caused by the rapid cooling capacity of the quenching medium. During quenching cooling, proper cooling speed and cooling time should be controlled.
Because the quenching temperature of forging waste heat is higher than that of ordinary quenching temperature, quenching immediately after high temperature deformation, so the hardenability of forging waste heat quenching parts is good, so carbon steel and alloy steel forging waste heat quenching generally use N22~N32 oil as quenching medium. The oil outlet temperature of quenching parts is generally between 100℃ and 110℃.
As mentioned before, oil is easy to aging, smoke, impact on environmental protection, can use polymer quenching medium, polyalkylene glycol (PAG) quenching medium is used more, its cooling performance is good, forging cooling uniformity is good, in long-term use performance is stable.
The quenching tank should have sufficient volume and be equipped with continuous transmission belt. The operation speed can be adjusted to ensure the necessary cooling time. In addition, quenching medium mixing system, cooling system and heating device, quenching medium temperature automatic control, in order to strictly control the quenching medium temperature fluctuation range. If it is oil, it should also be equipped with quenching fume exhaust device.
The quenching medium should be monitored, maintained and maintained regularly to ensure that the quenching medium has the required cooling performance. For quick-quenching oil, the cooling capacity of oil should be measured regularly, and the proportion of oil should be adjusted accordingly. It is strictly forbidden to bring water into the quick-quenching oil in any way, and regularly precipitate, filter and clean the impurities such as oxide scale in the oil tank and circulation system to keep the quenching oil clean.
For water-based quenching fluid (polymer quenching medium), in long-term batch production, the cooling characteristics of the quenching fluid should be controlled according to the following methods.
The viscosity method must be used to measure and control the concentration of quenchants used for a long time. Once a week, the viscosity of its movement should be measured with a viscosity meter, and the concentration coefficient can be converted. In the production process, the refractive index of the quench solution is measured on time, and the concentration of the quench solution is obtained by multiplying the index by the concentration coefficient measured in the week.
It is important to measure the cooling capacity of the quench fluid regularly. Because with the growth of the use time, the impurities in the quenching medium increase, the medium aging and even metamorphism. Inevitably, the ground high cooling rate and 300℃ cooling rate of quench liquid are increased, and the temperature corresponding to the highest cooling rate is reduced, thus increasing the tendency of forging cracking. The technical personnel should adjust the quench solution concentration according to the measurement results and the actual situation.
Periodically precipitate, filter and clean the tank liquid and the impurities in the circulation system such as dust, rust and gasification skin to keep the quenching medium clean. Do not mix oil with the quenching liquid tank in any way. If oil is mixed with the quenching liquid, the quenching agent will fail. When not in use for a long time, the quenching agent circulation system should be run regularly to prevent anaerobic bacteria in the quenching system. When bacteria are produced in the quenching agent, the quenching liquid will stink and blacken. If the quenching liquid is found to be smelly and black, germicide should be added in time to remove bacteria.
Because the quenching temperature of forging waste heat is higher than that of ordinary quenching temperature, quenching immediately after high temperature deformation, so the hardenability of forging waste heat quenching parts is good, so carbon steel and alloy steel forging waste heat quenching generally use N22~N32 oil as quenching medium. The oil outlet temperature of quenching parts is generally between 100℃ and 110℃.
As mentioned before, oil is easy to aging, smoke, impact on environmental protection, can use polymer quenching medium, polyalkylene glycol (PAG) quenching medium is used more, its cooling performance is good, forging cooling uniformity is good, in long-term use performance is stable.
The quenching tank should have sufficient volume and be equipped with continuous transmission belt. The operation speed can be adjusted to ensure the necessary cooling time. In addition, quenching medium mixing system, cooling system and heating device, quenching medium temperature automatic control, in order to strictly control the quenching medium temperature fluctuation range. If it is oil, it should also be equipped with quenching fume exhaust device.
The quenching medium should be monitored, maintained and maintained regularly to ensure that the quenching medium has the required cooling performance. For quick-quenching oil, the cooling capacity of oil should be measured regularly, and the proportion of oil should be adjusted accordingly. It is strictly forbidden to bring water into the quick-quenching oil in any way, and regularly precipitate, filter and clean the impurities such as oxide scale in the oil tank and circulation system to keep the quenching oil clean.
For water-based quenching fluid (polymer quenching medium), in long-term batch production, the cooling characteristics of the quenching fluid should be controlled according to the following methods.
The viscosity method must be used to measure and control the concentration of quenchants used for a long time. Once a week, the viscosity of its movement should be measured with a viscosity meter, and the concentration coefficient can be converted. In the production process, the refractive index of the quench solution is measured on time, and the concentration of the quench solution is obtained by multiplying the index by the concentration coefficient measured in the week.
It is important to measure the cooling capacity of the quench fluid regularly. Because with the growth of the use time, the impurities in the quenching medium increase, the medium aging and even metamorphism. Inevitably, the ground high cooling rate and 300℃ cooling rate of quench liquid are increased, and the temperature corresponding to the highest cooling rate is reduced, thus increasing the tendency of forging cracking. The technical personnel should adjust the quench solution concentration according to the measurement results and the actual situation.
Periodically precipitate, filter and clean the tank liquid and the impurities in the circulation system such as dust, rust and gasification skin to keep the quenching medium clean. Do not mix oil with the quenching liquid tank in any way. If oil is mixed with the quenching liquid, the quenching agent will fail. When not in use for a long time, the quenching agent circulation system should be run regularly to prevent anaerobic bacteria in the quenching system. When bacteria are produced in the quenching agent, the quenching liquid will stink and blacken. If the quenching liquid is found to be smelly and black, germicide should be added in time to remove bacteria.
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