Tilting melting furnaces

Vacuum and Atmosphere Melting. A coreless high frequency induction furnace is enclosed in a container or tank which can be either evacuated or filled with a gaseous atmosphere of any desired composition or pressure. Provision is made for additions to the melt, and tilting the furnace to pour its contents into an ingot mold also enclosed in the tank or container without disturbing the vacuum or atmosphere in the tank (Fig. 2). 

Figure 2. Skull melting furnace positioned for (a) tilt pouring (top) and (b) centrifugal casting. (After Ref. 1.)...

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). 

Fig. 5.28. Tilting batch aluminum melting furnace with a pair of Integral regenerator-burners for heat recovery. Courtesy of Degulsa S.A.

The metallurgical equipment of cast houses at secondary A1 plants is melting furnaces, stationary or tilting holding furnaces, degassing units, crucible- or channel-type induction furnaces for remelting of disposal or wastes and preparation of alloys, and gas-fired furnaces for remelting of disposal and wastes. 

FIGURE 14.4 Schematic design of a direct arc electric furnace for steelmaking. The whole unit may be tilted to the side for emptying the finished steel melt. 

To better expose solid loads for melting, it is preferable not to cover them with molten liquid, but of course that is the ultimate objective of the furnace A step in the direction of faster, more productive melting is to completely drain the furnace before charging new solid loads—in other words, to leave no heel either liquid or solid. A tilting melter or holding furnace such as shown in figure 3.31 is very helpful in this effort. 

Fig. 3.31. Sectional view of a tilting aluminum melting and holding furnace in Hungary that tips either left or right to fully drain its liquid load. This avoids the problem of the bottom portion of the next charged load of solids being shielded from furnace gas convection and radiation. Two burners in diagonally opposite corners are tilted downward 3.5 degrees from horizontal. (See also fig. 5.28.)...

Rotary Smelter. A batch-type cylindrical furnace which can be rotated about its horizontal axis while frit is being melted in it when the process of melting is complete the furnace is tilted so that the... 

When it was evident that most of the free water had been expelled from the phosphates in the melt preparation of [Ca(P03)2]n above, the furnace temperature was increased slowly to perhaps 1000 °C. At this temperature the melt is an almost white hot liquid with a viscosity similar to syrup, as judged by the way it flows in a platinum dish when the dish is tilted. After perhaps 30 minutes at 1000 °C it was judged that the product was sufficiently free of water of composition to lower the temperature of the furnace. The furnace temperature was lowered to about 900 °C, where the melt was seeded with crystals from a previous preparation if these seed crystals were available or existed anywhere. Crystallization usually commenced immediately, unless the temperature was still too high or the melt had not yet reached the desired composition. 

In stationary melting and holding furnaces, the distance between anchor bolts should not exceed 500 mm in the walls in the vertical direction and should not be less than 1,200 mm in the horizontal direction. In the roof, the distance between anchor bolts should be within 450 mm. For tilting furnaces, these distances should be smaller. 

The roof in contemporary melting and holding furnaces is flat and made from preshaped castable blocks. The precast blocks consist of two or three layers with heat insulation and are hung on anchor bolts. The pads between the preshaped blocks are fiber materials. In tilting furnaces, the roofs are usually not from preshaped blocks and are made by gunning. If there is a chance that a temperature at the roof will exceed 1,200 °C, the refractory anchor bricks are used. 

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