Quartzites for crucibles and methods of lining crucible induction furnaces (Review)

Conclusions With observation of the requirements of chemical and grain-size compositions, progressive methods of lining work, and sintering of the crucible, domestic quartzites provide a long lining life of induction crucible furnaces in melting of iron and sufficient life in melting of carbon steel.Translated from Ogneupory, No. 6, pp. 48–52, June, 1985.     

Service of rammed crucibles for melting noble metals in induction furnaces

Conclusions We prepared and tested in service crucibles of fused magnesium oxide with special additions, having a considerably higher resistance in induction-furnace conditions at temperatures of about 2000°C. The additives guaranteed the necessary sintering of the working zone in the crucible, and helped to form a direct bond between the crystals of periclase.The structure of the used crucibles is described. The formation of the zone structure is connected with the temperature gradient, and in the hot zones is accompanied by intensive recrystallization and growth of periclase crystals.Translated from Ogneupory, No. 5, pp. 19–23, May, 1969.     

Highly refractory mixture for lining crucibles of induction furnaces for melting high-temperature steel

A dry corundum mixture for lining crucibles of induction furnaces of the powder metallurgy shop of the Dneprospetsstal' Plant that increases the durability of the lining in melting high-temperature powder steels is described. The economic effect of using the mixture amounts to 230,000 karb. per ton of melted steel.     

Development of a lining made from Karelian quartzites for crucible induction furnaces

Factors are considered that increase the service life of a lining for a crucible induction furnace. Results are provided for laboratory studies and industrial tests of Karelian quartzites of Jotnian age of the Shokshinsk formation and Jatulian age of the Metchang’yarvinsk formation. The effect of impurities is quartzites on crucible induction furnace lining wear resistance is studied. Brief characteristics of quartzites are provided. The possibility is established of using waste materials from quarry production of Shokshinsk quartzites for preparing quartzite mixes.     

Manufacture and service of induction furnace crucibles made of magnesite with sintering additives

Conclusions The use of rammed magnesite masses with sintering additives in the lining of induction furnace crucibles makes it possible to increase their strength by a factor of two or three. The sintering additives recommended are cheap and easy to obtain, and the procedure for ramming crucible linings is simple.     

Behaviour of spinel-forming DVM using crucible induction furnaces. A case study on material failure

This article contributes to the understanding of the sintering behaviour of spinel forming dry vibrating mixes (DVM) that are in common use in crucible induction furnaces (CIF) for metallurgic treatment. At present, an unwanted sintering of the DVM as far as to the cold face is reported from the industry. For safety reasons it is indispensable that an unaffected layer is remaining at the cold face of the lining. If not, the material becomes brittle and the risk of crack formation gets unacceptable. The access of liquid melt to the induction coil may cause severe accidents that destroy the furnace which bears the risk of industrial injury.Systematic research on breakout materials by means of SEM-supported microtextural and microanalytical investigations come to the result that a sintering occurs already in areas of the lining where the prevailing temperature could not have exceeded 300 °C. Furthermore, it can be carved out that the sintering at the cold face is caused by the formation of spinel. This result is in contradiction to the generally accepted opinion that the spinel formation is kinetically hampered at temperatures lower than 900 °C and should not occur. The increased MgO:Al2O3 ratios of the newly formed spinels indicate lower crystallization temperatures. The gradual transformation starts with marginal dissolution of the magnesia grains at the cold face and progrades with the development of skeleton structures of matrix spinels.The spinel formation is favoured of different components as chemical additives, a reduced atmosphere, hydration, and a momentary overheating. However, it is suspected that water and short-term overheating, respectively, play the key role since other known major agents as untypical oxides, and in particular fluorides and chlorides can be excluded by their erratic occurrence. We identified water as a primary unwanted additive which left typical microstructures in magnesia grains of the studied lining breakouts.     

Corundum-zircon crucibles for induction melting of nickel alloys

Refractories and Industrial Ceramics -     

Study of the properties of pure types of fused magnesite for service in vacuum induction furnaces

Conclusions As regards the degree of sintering, the extent of the shrinkage, the thermal-shock resistance and the stability in contact with graphite at temperatures of service, the best material consists of fused magnesite containing 98–99% MgO, and the maximum grain size of the batch should be no more than 2 mm.Translated from Ogneupory No. 1, pp. 51–55, January, 1972.