Vacuum degassing furnace's principle and function

What is vacuum degassing furnace?

Vacuum degassing treatment is used to reduce dissolved gas components (e.g. hydrogen, oxygen, nitrogen) in steel to improve the performance of steel. Liquid steel comes from primary metallurgical production steps, and the capacity of ladle is usually 20-200 tons. The liquid steel is covered with slag to prevent reaction with the atmosphere. Some slag also has "activity". This means that they will also have a certain chemical reaction with liquid steel.

In the vacuum tank, the ladle is exposed to a vacuum environment usually less than 1 mbar. When the surface of molten steel is in contact with vacuum, the dissolved volatile gas will be removed. In order to contact the vacuum at the bottom of the molten steel, argon is used to stir the molten pool, and argon emerges upward from the "multi hole plug" at the bottom of the ladle. The rising argon bubble is filled with dissolved gas, which is very conducive to degassing.

Since the vacuum degassing system does not contain any heating equipment, the liquid steel will continue to cool. Therefore, degassing treatment must be carried out quickly and continuously.

The vacuum system must deal with high-speed air flow and a large amount of dust, which is generated by the condensation of liquid steel stripping gas.

Function of vacuum refining furnace

For the reasons such as slow vacuum pumping speed and poor product adhesion caused by water vapor and oil stain on the product surface, the vacuum degassing furnace removes the air, water vapor and oil stain in the vacuum chamber by filling nitrogen and heating the nitrogen, which can greatly shorten the vacuum pumping time before coating, reduce the aerobic corrosion in the vacuum coating system and prolong the service life of the equipment.

Process flow of industrial vacuum furnace

During operations at the VD, the liquid steel is stirred to promote homogenization by percolating argon gas through a single refractory stir plug arrangement in the bottom of the ladle. The argon connection to the ladle is established when the ladle is set in place inside the vacuum tank. The vacuum tank is evacuated to the required operating pressures by one of three ways: steam jet ejector, steam jet ejectors and a water ring pump, or, mechanical pumps. Emissions are evacuated through a vacuum pumping system and are collected prior to the pumps or they are discharged under water contained within a weir wall-equipped concrete hotwell. The process gases, including those entrained in the intercondenser discharge water, are exhausted from the hotwell via a motor driven fan to a vent stack equipped with a flare burner. Hotwell water is pumped to a cooling tower of the contact water system.