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Analysis of the advantages and disadvantages of vacuum induction furnace smelting

1. What are the advantages of vacuum induction furnace smelting?
Vacuum induction furnace smelting is a steel-making method for heating, melting, refining, alloying and casting of charge under negative pressure conditions. Compared with methods such as electric arc furnace and intermediate frequency induction furnace, it has the following advantages.

(1) Precise control of the chemical composition of the alloy
Since the whole process of smelting is carried out in a vacuum isolated from the atmosphere, the oxidation loss of alloying elements is reduced, and the oxygen content in the molten steel is very low, which greatly improves the recovery rate of alloying elements. This allows precise control of the chemical composition.
(2) Since the smelting process is carried out under vacuum, the gas content in the smelting alloy is very low. Deoxidation of molten steel with carbon under vacuum and casting under vacuum avoid secondary oxidation. These superior conditions make the content of gas and inclusions in the smelted steel low, which greatly improves the purity of the steel.
(3) Reduce the content of trace harmful impurities in steel
Trace impurity elements such as lead, arsenic, tin, antimony, bismuth, etc., bring very obvious harm to the hot working plasticity and high temperature strength of superalloy. Taking advantage of the high vapor pressure of trace impurity elements, high temperature and high vacuum can effectively remove impurity elements and reduce their harmful effects.
(4) The process parameters of vacuum induction furnace smelting are highly adjustable
Through the coordination and adjustment of factors such as smelting vacuum degree, temperature, refining time and furnace atmosphere, many refining purposes can be achieved. In this respect, its process flexibility far exceeds that of medium frequency induction furnace smelting. For example, vacuum induction furnace smelting has advantages in decarburization, deoxidation, denitrification, volatilization and removal of impurity elements, reduction of burning loss of easily oxidizable elements, and reduction of inclusion content in molten steel.

2. What are the disadvantages of vacuum induction furnace smelting?

The shortcomings of vacuum induction furnace smelting are as follows.
(1) Contamination of molten steel by crucible refractories
Under the dual action of high temperature and high vacuum degree of vacuum smelting, the crucible refractory will undergo a decomposition reaction, which will produce oxygen transport to the molten steel, increase the oxygen content of the molten steel, thereby reducing the purity of the molten steel.
In addition, under the above conditions, the carbon in the molten steel will undergo a reduction reaction with A1203, B203, SiO2, etc. in the crucible refractory material, and the molten steel will increase Al, B, Si, etc.
In a word, the reaction between the molten steel and the crucible material contaminates the molten steel and reduces the purity of the steel.
(2) The crystal structure of the ingot is not improved
It has the same structure as the ingot casted by the intermediate frequency induction furnace and the electric arc furnace, but has the disadvantages of composition segregation, uneven grain size, deep shrinkage cavity, and poor surface quality of the ingot.
(3) High equipment investment cost and high production cost
The equipment cost of the vacuum induction furnace is about 25~30 times that of the intermediate frequency induction furnace, and the production cost is about 5~10 times.