The VD system (VD) is the most widely used degassing system in commercial applications. In this system, the bucket is located in a vacuum chamber and sealed with a vacuum cap. The bucket must be equipped with a porous stopper for mixing with inert gas. Vacuum is created using steam-jet or mechanical vacuum pumps. During vacuum processing, the content of carbon, oxygen, nitrogen and hydrogen may decrease at various stages depending on the smelting conditions. In addition, the VD system (VD) can be equipped with vacuum bins for alloying materials, so that during evacuation it is possible to carry out composition adjustments. The advantages of this system are good homogenization and a higher yield of the finished product.
Most production programs require a combination of VD and VOD operations. For this purpose, mechanical equipment was developed for both operations.
In general, the processing of VD and VOD provides the following advantages:
- increase furnace productivity
- the use of cheaper materials with a high carbon content (chromium filling)
- reduction in production costs
- quality improvement
- the possibility of producing ultra-low carbon grades (ELC) with minimal loss of chromium
- achieving tighter chemical tolerances. Composition
VOD (wok) — vacuum decarburization of oxygen
After moving the bucket into the vacuum tank, vacuum degassing is carried out using a steam jet pump. Argon is blown through the bottom to stir fluid. The hydrogen and nitrogen content can be removed, and the oxygen and sulfur content can be further reduced, as a result of which the molten steel has a higher purity and better properties.
VOD performs functions such as vacuum degassing, argon mixing, oxygen decarburization, measuring and sampling without vacuum, etc. It can process bearing steel, alloy structural steel, spring steel, stainless steel, ultra-low carbon stainless steel, etc. e. Due to the excellent ability of vacuum degassing, the content of hydrogen, oxygen and nitrogen is minimized, and the elements are precisely adjusted, the inclusions float enough and the purity is effectively increased is.
VC (VL) — vacuum casting
The VC vacuum pump pours molten steel smelted in the atmosphere into an ingot mold in a vacuum chamber. This is a vacuum blasting device. The molten steel is reduced in bundles in the casting device into the vacuum chamber. Fixation expands due to a rapid drop in pressure and decreases in fasciculation at a large angle, increasing the area of degassing, helping gases to escape and promoting a surface reaction.
The level of degassing depends on the spill rate, drop height and diffusion angle, as well as on gas content, gate shape, vacuum, fluidity of molten steel, etc.
Vacuum casting significantly reduces the production cycle, which contributes to an increase in the utilization rate of equipment and lower energy consumption. In addition to dehydrogenation, VC can prevent secondary oxidation, reduce non-metallic impurities, reduce the degree of segregation and improve the internal quality of the ingot.
Furthermore, in a vacuum casting with deoxygenated or semi-deoxygenated molten steel, carbon in the molten steel can remove oxygen during vacuum treatment. The result of deoxygenation is gaseous CO, therefore, complete deoxygenation is achieved and purity is increased. Impurities may drop below 0.01% after vacuum treatment.
