Application of equivalent thermal circuits for calculation of thermal processes of induction cruel furnaces with a capacity of up to 1000 kg

The article describes new approaches to calculating the thermal regimes of induction crucible furnaces, as well as methods for calculating them using converted thermal circuits. The principles of constructing thermal models of structural parts and molten metal of induction crucible furnaces based on converted ETS and their use for the development of optimal systems for automatic control of the metal melting process are considered. The methodology for the development of ETS and the compilation of heat balance equations for induction crucible furnaces with a capacity of up to 1000 kg is presented..

The Peculiarities of Smelting of Wear-Resistant Cast Iron IChH28N2 in the Induction Crucible Furnace IChT10

Wear-resistant cast iron smelting is produced in electric arc furnaces, due to the use of steel scrap in metal charge, ferrochrome and refund if there is one. Scrap of cast iron with the necessary chemical composition is not present because the proportion of manufacturing parts from wear-resistant cast iron is very small. Thus, there is no opportunity to form castings of wear-resistant cast iron using foundries equipped only with induction crucible furnaces of industrial frequency (IChT), since the furnace is designed for melting temperatures not above 1500 °C. In addition, the lining of induction furnaces of industrial frequency is made of quartzite, which provides the necessary durability when operating at temperatures not above 1500 °C. The ability to manufacture blanks from wear-resistant cast iron gives an additional opportunity to expand the range of orders and prevent a reduction in production in factories equipped only with the smelting furnaces of the IChT. The article describes the peculiarities of smelting cast iron IChH28N2 in the furnace IChT10 with acid lining. The technology of conducting melting on pure charge materials without use of cast iron scrap and return is briefly described.

Cast Iron and Steel Smelting in Induction Crucible Furnaces of Industrial Frequency

A brief analysis of the cast iron and steel smelting in induction furnaces of industrial and medium frequency has been carried out. The analysis of the used metal scrap for the smelting of synthetic iron in induction melting furnaces with a padded lining of a lining mixture, based on quartzite, is carried out. The requirements for temperature melting modes, which are regulated by this type of melting furnaces developers, are reflected. The advantages and disadvantages of using induction crucible furnaces of industrial and medium frequency are considered. The features of smelting synthetic pig iron in Russia are noted, the main of which are the following: the absence of cast iron scrap, which makes it necessary to use a metal scrap from a single steel scrap, and use temperature melting conditions above 1450 ° C; use a lining based on quartzite, as the cheapest, but sharply reducing its resistance to the operation of the furnace at such melting temperatures (from 300-350 to 200-250 smelts). The actuality of the possibility of steel smelting in induction crucible furnaces of industrial frequency with the use of acid lining, based on the Pervouralsk quartzite, is substantiated. It is explained by the fact that existing foundries are equipped mainly with induction melting furnaces of industrial frequency, and the use of induction melting furnaces of medium frequency requires considerable material costs.

Effect of heat treatment of quartzite on the mechanism of destruction of the lining of induction furnaces

The mechanism of wear of quartzite lining of induction crucible furnaces during the smelting of iron and steel is presented. It has been established that the main cause of lining wear is a decrease in its strength caused by the transition of the tridimite joint into cristobalite, which is much easier to wash off the walls of the crucible with moving metal and slag. The second important factor of wear is the choice of quartzite raw materials, its material and granulometric compositions, the firing mode and the technology of melting during operation of the furnace. Silicon recovery from silica of carbonization lining by carburizer and cast iron, which is part of, is a secondary factor of crucible lining wear. Ill. 4. Ref. 5. Tab. 1.

WAYS TO IMPROVE INDUCTION CRUCIBLE FURNARES

Analysis of the main drawbacks caused by increased walls thickness of a lined crucible, presence of tubular copper single-layer inductor cooled from inside with standard water and absence or presence of core I-shaped magnetic circuits arranged around it forming a discrete ferromagnetic screen, was made for modern induction crucible furnaces. The first drawback is that a significant part of working electromagnetic flow Fwork is not used for effective heating, since it passes along the non-conductive lining of crucible, and not along the cage. Therefore, only 38.5 – 57.0 % of the flow Fwork is effectively used. The second drawback is increased cost and complexity of manufacturing of inductor coils from a special copper tube, which vibrate at twice the frequency, creating noise and weakening design of the furnace. Such inductors are characterized by reduced electrical efficiency and increased cost of preparation and cooling of conditioned water in systems that occupy an area several times greater than the area of furnace itself. The third drawback leads to the fact that a significant part of electromagnetic scattering flow of the Fconsupt does not participate in heating of charge and melt, but heats conductive elements of furnace, including surrounding magnetic inductor. Irrational use of total flow F, created by inductor, reduces its efficiency to almost 19 – 30 %, and the power factor cosφ to 0.03 – 0.10 and increases energy consumption. To reduce or eliminate disadvantages, three ways of improving these furnaces are proposed and justified: reducing thickness of crucible wall with its simultaneous hardening by installing a cylindrical shell between the crucible and the inductor, surrounding the inductor with an annular magnetic circuit and using a single or multiwire inductor instead of a tubular one. Combination of cylindrical shell, annular magnetic circuit, as well as the upper and lower plates of the furnace frame can form an annular closed cavity to accommodate wire inductor and circulating refrigerant, cooling the inductor and the magnetic circuit. As a result of the study, new design of induction crucible furnace with wire inductor and ring-type magnetic circuit developed at AltSTU is proposed, substantiated and patented. Based on experimental determination of effectiveness of the proposed structural elements, conclusion is made about the prospects for further research.

Specialty of Сarbon-Carbid-Silicic Mixture Using (UKKS) as Substitute of Re-Carburizing Agent and Ferrosilicon for Grey Iron Melting

In the transition to modern high intensive processes of smelting there had been reversed technologies structures to get carbon content in cast iron. A re-carburizing agent, that can be one of the most significant reasons of occurrence of defects of the cast, and deformed metal and decrease of the level of properties have been identified. There was not only made the decarburizing agent of modern technology of production of pig-iron essential element (particularly synthetic), but also resulted in many of variants of its realization from the standpoint of level decarburizing, type, using re-carburizing method of decarburizing technological phase, where enter of carbonaceous materials. Particularly sharply process of execution re-carburizing influences receipt of synthetic pig-iron in induction crucible furnaces of industrial frequency from metal works, which contained 80-90% of steel breakage. Then, it is necessary to raise the content of carbon from 0,3 to 3,0-3,8% (depending on the pig-iron mark). It forces foundry enterprises to approach with big care at a choice of existing materials, which it is possible to use as decarburizing and to verify carefully, which is appearing at the market. In work application there are considered variants of using carbon-carbide-silicon mixture UKKS-31 at melting of grey pig-iron in induction, crucible furnaces, intended for pig-iron melting. The cost comparison is presented between traditional technology and with using mix UKKS-31.