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How to select the refractory for induction furnace
Jan 05, 2018

1.       How to select the refractory for induction furnace?


A:When refractory material is applied to the induction furnace, not only will we consider the profile design, the structure and the melting process, but also take the refractory material and its mineral phase from normal temperature to work temperature, the changing process and mechanism of the physical properties into consideration. In addition, refractory materials will be selected and improved according to the application requirements, especially the requirements of innovative equipment.


2.How to select the refractory for cored induction furnace?


A: When the coreless induction furnace is used to smelt cast iron (ductile iron, gray iron and malleable iron) and non-ferrous metals, for the lining of refractories we usuallyadopt quartz sand or zircon, or a mixture of both dry knotting , and boric acid or borax as a sintering agent.


When using acidic steel-making method, the main lining of the furnace is made of quartz sand and sometimes also zircon. Andits lining method, baking system and sintering process are almost the same withthose of the smelting of cast iron.

When using alkaline steel-makingmethod, the lining is made of neutral or alkaline refractory materials and graphite crucible. Magnesia can be added to the proper amount of AL2O3 powder, after heated its mineral phase wouldturn into magnesium Stone and spinel with excellent high temperature performance.

For medium-sized coreless induction furnace, refractories mainly adopt white corundum, and meanwhile increase the content of MgO fine powder. If high purity and high quality corundum raw materials are used as the main material, fine powder will be MgO-AL2O3 mixed fine powder made of spinel. In another case, chrome ore may be added to the Al2O3-MgO mixture so as to form all-in-place Al2O3 composite spinel refractory in the form of composite spinel of magnesium, aluminum and chromium when in use.

For large coreless induction furnace, the lining refractories were designed by MgO-Spinel program, that is, magnesia as the coarse particles, pre-synthesized spinel as the particles and fine particles with Al2O3 and MgO fine powder, the mixture formed spinel in place at high temperatures.


3.How to select the refractory for coreless induction furnace?


A: Refractory for Core-fired furnace chamber have to be corrosion resistance, anti-erosion, anti-infiltration, high chemical stability. We usually select fused alumina corundum, with appropriate amount of sintered alumina powder, and high aluminum Low binder cement and super low cement refractory castables. In order to improve the thermal shock resistance of the lining, and considering that the reducing gas is mostly in the furnace, a certain amount of iron-containing SiC can be added to the castable to obtain a Sic-containing high-tech Al2O3-Sic refractory . This high-tech refractory castable as a core-fired furnace refractory material, it can get a very high life.

The refractories for the sensor of the core induction furnace include refractories for melting grooves, sealing and insulation. The melting grooves are generally made of refractory castables or knotted materials using fused magnesia or Al2O3-MgO sand as raw materials. Sealing materials can select Al2O3 as sealing material, and high-alumina cement or H3PO4 as a binding agent, and Cr2O3 powder as separator.

Furnace cover is generally composed of thermal insulation layer and hot surface layer. The former is made of high aluminum light brick masonry or Al2O3 hollow spherical particles as the main raw material, and is made of refractory castable with high aluminum cement as binder. The latter is made of AS-85 / 80 clinker aggregate and fine powder, and with the proper amount of magnesia powder as well as high alumina cement as a binder castable.

For melting Cu core induction furnace, the refractory materials for the melting groove of the sensor select dense bauxite clinker as the main raw material. Considering the strong permeability of Cu, fine-grained Sic can be added to the ingredients to improve the resistance to wettability. Lining methods include masonry knot and dry vibration molding.

When the furnace is melting Al and Zn, the lining is generally made of refractory materials used bauxiteas raw material, and usually made by casting.