The requirements of the purity of molten steel make the refining furnace outside the furnace widely used, commonly used LF furnace, VD furnace, RH furnace.
The LF furnace is a ladle furnace, which is actually a ladle cover with electrodes. When the steel type and temperature have special requirements, the ladle car drags the ladle (molten steel tank) under the ladle cover. The electrodes installed on the ladle cover heat the molten steel. At the same time, argon is blown at the bottom of the ladle, and the molten steel is heated and boiled to remove inclusions. LF furnace generally adopts water-cooled structure, or the insulation layer is added with pouring and grouting construction.
The VD furnace puts the ladle into the furnace, blows argon through the bottom, and evacuates the upper part to make the molten steel tumbling to achieve the purpose of removing impurities. The structure of the VD furnace is simple. The furnace wall uses insulation bricks, and the high aluminum bricks below are used as cushions.
RH furnace is the molten steel under vacuum suction, through the ascending pipe, into the vacuum chamber, and then through the descending pipe, back to the ladle, circulating to achieve the purpose of purifying molten steel.