Coreless induction furnace

Fig. 8. Small coreless-induction furnace, 500-kg high, frequency furnace with insulating board housing and cmcible.

Frequency Selection. When estabhshing the specifications for a coreless induction furnace, the material to be melted, the quantity of metal to be poured for each batch, and the quantity to be produced per hour must be considered simultaneously. Graphs have been developed that combine these factors with practical experience to indicate possible solutions for a specific requirement. 

Induction Furnace. The high frequency coreless induction furnace is used in the production of complex, high quaUty alloys such as tool steels. It is used also for remelting scrap from fine steels produced in arc furnaces, for melting chrome—nickel alloys and high manganese scrap, and more recentiy for vacuum steelmaking processes. 

Core damage frequency (CDF), for nuclear power facilities, 17 540 Coreless induction furnaces, 12 309-311 Core level electron energy loss spectroscopy (CEELS), 24 74 Coremans, Paul, 11 398 Core-shell model, 14 464 Core-shell particles, in polymer blends, 20 354-355... 

High fidelity reproduction, lithographic resists and, 15 156 High flux dialyzers, 26 818 High frequency coreless induction furnace, 23 253... 

Cast steel is normally melted in electric arc furnaces (EAF) or in coreless induction furnaces (IF). Once melted, the liquid metal can be refined (i.e. removal of carbon, silicon, sulphur and or phosphorus) and deoxidised (i.e. reduction of metallic oxides), depending on the base material and the quality requirement of the finished product. Figure 2.3 gives process flow diagrams for the melting and metal treatment of cast steel in the different furnace types. 

Process scheme with the electric coreless Induction furnace... 

The coreless IF is a batch-melting furnace containing a water-cooled copper coil, the inside of which is internally refractory lined. The outside is insulated and enclosed in a steel shell. The furnace body is mounted in a frame equipped with a tilting mechanism. A coreless induction furnace is normally a refractory-lined bucket-shape refractory, the top of which is open for charging and deslagging operations (see Figure 2.13). 

Figure 2.13 General arrangement of coreless induction furnace [47, ETSU, 1992]... 

The coreless induction furnace is used for melting but cannot be used for refining. Therefore, in steel foundries the induction furnace has to be charged with raw materials of the correct chemical composition, i.e. that corresponding to the required composition of the melt hence steel scrap is mainly used. If necessary, the metal can be refined after melting in an AOD converter or in special treatment ladles (see Section 2.4.12). 

Induction furnaces are excellent melting units, but in general they are less efficient holders. When they are used for melting only, the molten metal is mostly moved to an efficient holding furnace as soon as it has reached the desired temperature. Many types of coreless induction furnaces are available, with fixed or removable cmcibles. For aluminium, both channel and coreless induction furnaces are available for melting and holding. However, the charmel type is seldom used, due to difficulties in keeping the channel open and due to the need to maintain a molten heel at all times. 

Thermal losses through the cooling water and the furnace wall are low compared to those in the coreless induction furnace. Equipping the furnace with pouring channels according to the teapot principle allows for a reduced oxidation of the melt and wearing of the refractory. 

Due to its batch character, the rotary furnace provides an equal flexibility as the coreless induction furnace in the cast iron foundry. The investment costs however are lower. A 5 tonne furnace costs EUR 500000 - 600000, of which 30 % are for the exhaust system and dedusting. The rotary furnace is also a good alternative for the small-scale cold blast cupola, due to its higher flexibility and lower environmental costs. Rotary furnaces are used for melting volumes of 2 to 20 tonnes, with production capacities of 1 to 6 tonnes per hour. 

Limiting the slag is very important for good operation of the coreless induction furnace. The operation is more affected by the scrap cleanliness than the other furnace types. 

Process optimisation options for coreless induction furnaces include ... 

The capture of smoke and dust is the most difficult problem to solve when installing an olT-gas collection system on a coreless induction furnace, since there is no exhaust shaft. Several methods have been developed in the past decade, each with advantages and disadvantages. 

ETSU (1992). "Guidance Notes for the Efficient Operation of Coreless Induction Furnaces (Good Practice - Guide 50)", Energy Efficiency Office - Department of the Environment. 

Table 10.4 summarises the costs of cast iron calculated for the 3 main cupola types compared with coreless induction furnace. Some items greatly depend on the melting device and the grade energies and fluids, metallic charge and ferro alloys. They are detailed in Table 10.5 and Table 10.6. 

The investment is less important than for eold blast, eokeless cupola and coreless induction furnace. 

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