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Induction Furnaces refractory lining


Induction furnaces are one of the most challenging of all refractory applications. The success of the assembly of high-volume induction steelmaking plants urgently needs to improve the performance of refractory materials, and as a result, the continuous improvement of the performance of refractory materials for induction steelmaking has been promoted.

Refractory materials for induction furnaces need to be selected according to the furnace type, furnace structure, type of steel to be smelted, smelting process and operating conditions, etc. At the same time, the phase and physical properties of the refractory material from room temperature to working temperature should also be considered. Change process and change mechanism, and application conditions of refractory materials, etc.

(1) When smelting cast iron and non-ferrous metals in a coreless induction furnace, SiO2, ZrO2·SiO2 and the complex phase refractories composed of them are generally selected. Since ZrO2·SiO2 is thermally decomposed at high temperature to generate f ZrO2 and fSiO2, which are uniformly distributed in the material, thereby giving the material high temperature plasticity and corrosion resistance, indicating that ZrO2 can prolong the SiO2 refractory material.

(2) The coreless induction furnace can adopt either the acid steelmaking method or the alkaline steelmaking method. Acid steelmaking refractories are the same as smelting cast iron, using acid refractories; basic steelmaking use neutral or alkaline refractories.

(3) When making steel in a small coreless induction furnace, magnesia refractory materials are usually used for lining, but this refractory material has poor thermal shock resistance, and is easily penetrated by slag, resulting in structural peeling and premature damage, so it is difficult to Adapt to the use environment of large capacity and intermittent operation.

(4) Refractory materials made of MgO-Al203 or MgO-Spinal mixtures are used in steelmaking of medium-sized coreless induction furnaces in normal operation, all of which belong to MgO-Spinel series refractories.

(5) The medium-sized coreless induction furnace that uses various scrap steels as raw materials for steelmaking uses Al203-MgO (about 10% MgO) refractory materials, which can achieve high service life.

(6) Medium-sized induction furnaces with direct reduced iron balls as additives should use MgO-Al203-Cr203 (chromium ore added) refractories. Due to the reaction of MgO, Al2O3, Cr2O3, etc. to form composite spinel when heated at high temperature, it has high refractory performance and strong corrosion resistance. long.

(7) Large-scale coreless induction furnaces use spinel refractories made of pre-synthesized Spinel pellets, and can also use spinel refractories composed of MgO (coarse particles, fine powder), Spinel (medium particles, fine powder) and Al203 particles Mixed materials, and MgO-Spinel based refractories made by carefully balancing the ratio of pre-synthesized Spinel and in-situ Spinel. Both types of refractories are compatible with the operating conditions of large coreless induction furnaces.

(8) The operating temperature for smelting gray iron and cast iron in a cored induction furnace is 1450-1550 °C, which is not very high. Although the temperature at the melting ditch and the water jacket of the inductor is as high as 1600-1700°C, the selection of refractory materials is not very difficult due to the implementation of water cooling.

(9) The coreless induction furnace mainly adopts the knotting method to build the lining, while the cored induction furnace mainly adopts the pouring method to build the lining. Knotted lined refractories form a sintered layer during the sintering process. In order to obtain high adaptability, it is desirable that the expansion of the sintered layer and the rise in strength proceed slowly. Therefore, the formula design and raw material selection of the refractory material should ensure that the working surface in contact with the high temperature melt can be sintered to form a sintered layer with a certain strength when the lining is working, while the non-working layer should maintain the bulk structure before sintering. The structure has the effect of preventing the migration of cracks in the working layer and absorbing cracks, and lays a good foundation for prolonging the service life of the lining.