Principle and Realization of Droplet Control in Vacuum Consumable Arc Furnace

Vacuum consumable arc furnace (abbreviated as consumable arc furnace) can melt active or refractory metals such as titanium, molybdenum, zirconium, niobium, tungsten and their alloys. Since the end of 1950s, it has been used to melt stainless steel, abrasive tool steel, bearing steel, superalloy and other materials. The materials melted in consumable furnaces have the advantages of high homogeneity, good compactness, no macrosegregation and almost no micro-segregation, so they are widely used in material production in aviation, aerospace, energy, transportation and other fields.
1. Melting Principle of Vacuum Consumable Furnace
As shown in Fig. 1, the vacuum consumable furnace melts the prefabricated metal consumable electrodes rapidly and the real cash is remelted under the condition that the vacuum degree is less than 60 umbar and the arc discharge produced by DC generates high temperature. Vacuum remelting is an industrial refining process under completely inert conditions.
Refining occurs between the metal bath (anode) at the bottom of the electrode (cathode) and the top of the spindle. The molten steel solidifies and recrystallizes in a water-cooled copper crucible. The gradual formation of ingots.
The main advantage of self-consuming furnace is controlled solidification of spindles in water-cooled copper crystallizer, resulting in high quality and uniform materials with excellent metallurgical properties. Degassing and removal of non-metals from raw materials are achieved by vacuum extraction in furnace and decomposition of oxides at 4000 - 5000oC arc temperature. The material remelted by consumable furnace has low residual gas content, high cleanliness, excellent cold and hot working performance, and greatly improved transverse mechanical properties.
2. Constant Melting Rate Melting in Vacuum Consumption Furnace
Controlled solidification of spindles is necessary to obtain high quality materials by vacuum consumable remelting. One of the important parts is the controlled constant melting rate of consumable electrodes.
The results show that when the temperature of arc discharge is high enough, a 1-2 mm thick molten metal film will be formed at the bottom of the consumable electrode (cathode). Under the action of surface tension and gravity, droplets will be formed gradually. Then a short circuit will be formed between the cathode and the anode by bridging the gap between the cathode and the anode. The strong current flowing through the short-circuit droplets will produce Lorentz force, and the effect of high density current and Lorentz force will be produced. The droplets burst and the tiny droplets are sprayed in all directions, and most of the droplets are transferred to the molten pool.