Metal smelting is one of the main processes of casting. The quality of the casting material is determined by this process. This process is also an important part of the process of liquid metal casting and molding, and the quality, production cost, output, energy consumption, and environmental protection of castings. And so closely related. Smelting furnaces are necessary equipment for foundry production. The correct choice of smelting furnace can ensure the quality of metallurgy, save energy, reduce production costs, and increase labor productivity.
First, the classification of melting furnace Non-ferrous alloy melting furnace can be divided into two major categories of fuel furnace and electric furnace. The fuel furnace uses coal, coke, coal gas, natural gas, fuel oil, etc. as fuel, and the fuel furnace can be divided into two types, a citrus vortex furnace and a reverberatory furnace. Electric furnaces are usually categorized according to the method of conversion from electrical energy to thermal energy. They can be divided into resistance melting furnaces, induction melting furnaces, and electric arc furnaces. Resistance furnaces can be further subdivided into mandarin electric resistance furnaces, reflection resistance furnaces and box resistance furnaces; induction furnaces can be subdivided into intentional industrial frequency induction furnaces and unintentional industrial frequency induction furnaces, and the frequency can be fined according to the frequency. Divided into industrial frequency furnace, intermediate frequency furnace and high-frequency furnace three; arc furnace can be divided into non-consumable furnace and self-consumption furnace
Each smelting furnace has its alloy suitable for smelting. See Table 4-1. Commonly used smelting furnaces 1. Increased eddy resistance furnace Manganese resistance furnace is an electric furnace that uses electric current to heat through an electric heating element to melt metal. The capacity is generally 30--400kg. The electric heating elements are metal yttrium-chromium alloy or iron-chromium alloy and non-metallic silicon or silicon platinum element. The citrus vortex resistance furnace is mainly composed of electric furnace body and control rejection (including controller A). Citrus crush resistance furnace is divided into rotary type and fixed type. Figure 4-1 is a fixed-site eddy resistance furnace. The turbulence of the citrus vortex and the furnace body will cause the resistance wire to move, deform or even break, so as to reduce the service life of the resistance wire, so it is generally a fixed type. Pouring small and medium-sized castings directly from the pot A by using a hand-held pouring ladle to draw metal liquid, and when casting a large casting, the casting site A can be lifted for pouring.
Pic 4-1
This kind of electric furnace has a compact structure, and the electrical equipment is simple and inexpensive. Compared with the industrial frequency induction melting furnace, the equipment has less investment and is more suitable for melting small-capacity non-ferrous alloys. The biggest disadvantage of this type of furnace is that it takes a long time to smelt. For example, when smelting 150--200kg of molten aluminum, the first furnace needs 5-5.5h, consumes more power, and has low production efficiency. Judging from the development trend, a larger capacity citrus eddy resistance furnace will be replaced by an industrial frequency induction furnace.
2. Reflective Resistance Furnace The reflective heating element has a heating element at the top of the furnace. The fused metal is heated by radiant heating from the top down. In order to prevent the molten metal from being splashed onto the heating element and eroded, the heating element should normally be installed in the groove of the roof tile. The furnace chamber consists of a bath and one or two inclined front chambers. The front chamber is a sloped surface that slopes toward the bath. The molten raw material is placed on the slope first. As the melting progresses, the melt flows into the bath and the oxide is left on the bottom of the front chamber. This type of electric furnace can be subdivided into two types: fixed type and tilt type. The furnace body of the fixed electric furnace cannot be turned. During pouring, the molten metal flows out of the overflow port or is sucked out by a siphon device. Figure 4-2 is a schematic diagram of a furnace with a fixed reflection resistance furnace. Inclined electric furnace has a tilting mechanism at the bottom
Figure 4-2
Reflective resistance furnaces have the advantages of stable furnace gas, low oxidation and suction, clean melt, and large capacity ((1-100, good working conditions, suitable for the production of large castings and mass production casting workshops. However, such furnaces cannot The use of flux, can not be refined and modified in the furnace, its biggest drawback is that the long melting time, low production efficiency, large power consumption, there is, electric tiger, said, such as each smelting It aluminum alloy, need 600kW "h above The power of the battery is followed by the short life of the heating element. In order to increase the lifespan, the resistance wire can be changed to a silicon-platinum rod, but the top of the furnace must be replaced with a wedge-shaped ordinary firebrick to form a vault instead of a flat top composed of a special-shaped brick. The silicon platinum rods are installed on the holes of the original resistance wire lead bricks on the side of the furnace wall. During use, due to aging of the silicon platinum rods (increase in resistance value, the furnace power will decrease. In order to ensure that the power of the furnace is basically unchanged, it is best to use The transformer can increase the phase voltage, and it can also adopt the method of changing the wiring (from star to delta connection; A). The service life of silicon-platinum rod is longer than that of resistance wire, and the exchange is also more convenient. Practice proves that with Compared wire, platinum number of silicon rods and overhaul each overhaul work are much reduced, improving equipment utilization, reduction in power consumption per ton of metal is about 80% faster melting rate, increase in productivity nearly doubled
From the point of view of development trends, reverberatory furnaces are gradually being replaced by industrial frequency induction furnaces.
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