Vacuum arc refining degassing furnace new system VAD designed recently by Austria Inteco special smelting technology is better in the aspect of simple structure and steel quality than LF(ladle furnace)+VD(vacuum degasser furnace which is widely used at present. Besides, one VAD equipment could complete both work of LF and VD. It is a new step in vacuum arc refining degassing technology.
Conventional vacuum arc degassing refining furnace
Conventional vacuum arc degassing refining furnace (VHD) is designed by an American A. Finkl & Sons in 1964 and got a US patent in 1970 after years of researches and experiments. Then VHD equipment is used more and more widely in metallurgy. During the time from 1970 to 1990, VHD technology can fully meet product quality and treatment requirements of special steel factories.
However, it couldn’t reply to demands of modern special steel smelting in latest 20 years, and is replaced gradually by ladle furnace(LF)and vacuum degasser(VD). This new processing is currently widely used at home and abroad, but its The disadvantage is that the arc heating and vacuum degassing apparatus needs to be done in 2 separate equipments.
Vacuum arc degassing refining furnace VAD
Liquid steel gets out of steel tank by primary arc furnace, and is poured into the ladle at head-room clearance 500-800mm. Then the ladle is transported by a crane in the workshop to the vacuum vessel, which is supported by three hydraulic cylinders on lifting frames. After the vacuum vessel is covered, vacuum arc degassing refining furnace multi-stage steam jet vacuum pumps start to extract the air (it is alo ok to use vacuum arc degassin refining furnace mechanical vacuum pumps). While the vacuum degassing is in process, inert gases like argon or nitrogen is blew into furnace hearth through the ladle bottom to make sure liquid metal mixing and circulating.
In the central position of the vacuum vessel cover stall three electrodes which are sealed in the dynamic way and move down and up. Graphite electrodes are mounted in a vacuum sealed telescopic tube . The distance between the electrode and the bath surface generally does not require frequent adjustment because the arc length can be maintained for a long time in a vacuum state. Electrodes touch neither liquid steel surface nor steel slag surface, and they aren’t oxidized easily when exposed in air, which reduces greatly electrode consumption. A shielding layer is installed above the arc in the vacuum chamber in order to prevent radiation heat from the arc furnace cover, and reduce heat loss. The arc energy towards bath surface blow away slag. As a result, gas escapes easily from the pool. Refining treatment is continuous until gas content is reached as metallurgy requires.