Application of liquid nitrogen in vacuum heat treatment

Application of liquid nitrogen in vacuum heat treatment

Vacuum heat treatment is an advanced heat treatment method being used at home and abroad. Nitrogen is often used in vacuum heat treatment. For example, when steel parts are heated in a vacuum furnace, if the vacuum degree is too high, in order to prevent the alloy elements in the workpiece materials from volatilizing, it is necessary to recharge the furnace with an appropriate amount of nitrogen to lift off the pressure of trace gases in the furnace. For another example, in the vacuum quenching process of vacuum heating oil quenching, sometimes in order to ensure or improve the cooling capacity of quenching oil, it is necessary to recharge enough nitrogen into the vacuum furnace before the workpiece is cooled.

In the process of high-pressure gas quenching, it is necessary to quickly fill the vacuum furnace with nitrogen at a pressure higher than one atmosphere. When the steel is tempered in vacuum, it is necessary to recharge nitrogen after vacuumizing to realize the uniform heating of the protective gas circulation in the furnace and the rapid cooling after tempering.

There are various sources of nitrogen for vacuum heat treatment. Because the density of liquid nitrogen is much larger than that of nitrogen, the volume of liquid nitrogen is much smaller than that of nitrogen, so it is convenient for transportation and storage, and the price is cheaper when it is supplied in large quantities. Therefore, liquid nitrogen is one of the important sources of nitrogen used in vacuum heat treatment.