Induction Furnace Melting Cast Iron

The process of iron melting in induction furnace is relatively stable, the composition is easy to adjust, the temperature is easy to control, and the burning loss in the melting process is less. In particular, compared with cupola, the consumption of nodular cast iron is conducive to obtaining low-sulfur liquid iron, reducing environmental pollution, improving working conditions, the quality of castings is relatively stable, and low-cost raw materials can also be applied. But everything always has duality. In the consumption theory of iron melting by induction furnace, there are also some casting defects, which are the common and easy-to-produce specificity of induction furnace.

(1) With the increase of whiteness and undercooling, the number of nuclei in liquid iron of induction furnace is less than that of cupola. It is concluded that with the prolongation of holding time and the improvement of melting (superheating) temperature, the root structure of cast iron varies, the number of eutectic clusters decreases, and the whitening depth increases gradually.

(2) The structure of D-type and E-type graphite presents. When the molten iron is superheated to a higher temperature and kept warm for a long time, the number of A-type graphite is easily reduced in the obtained hypoeutectic gray iron. The proportion of D-type and E-type graphite increases and the degree of supercooling increases in the obtained cast iron structure. This kind of undercooled graphite affects the cutting performance of mechanical processing. The strength and hardness of cast iron will be affected by the prolongation of holding time when the amount of ferrite in the root structure of cast iron increases and the graphite of D and E type appears.

(3) Shrinkage and external shrinkage of iron castings. As the molten iron keeps warm for a long time, casting defects will appear in cast iron. In addition to the increase of whiteness tendency and the dissimilation of matrix structure mentioned above, shrinkage holes and external shrinkage defects will also occur during solidification. Thin-walled castings (single cast piston rings) are prone to excessive edge hardness or whiteness defects; mechanical parts with large wall thickness difference are prone to produce unfamiliar looseness, shrinkage or shrinkage holes at the thick wall of castings. Create defects. In addition to the effect of long-term heat preservation of molten iron, it is also related to the heavy oxidation of metal burden which takes part in rusting.

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