Using Vacuum Induction Furnace to Melt Better Products

Vacuum induction smelting furnace equipment itself is a comprehensive, involving a wide range of professional equipment. Its equipment and operation involve vacuum, induction power supply, hydraulic, pneumatic, mechanical structure, cooling water system, automatic control system, etc. Its operation also involves thermocouple, vacuum pump oil, refractory, lining knotting, sintering, baking temperature, ingot mould design, stripping die riser design, feeding, steelmaking, metallurgy and other fields of knowledge. There is no such a complete professional field in our school. Many of our knowledge is based on our own professional knowledge combined with our many years of experience.
Whether it is the production of master alloy rods or the production of electrode rods requiring further remelting or rolling. Vacuum induction smelting furnace, its operation has some basic and common processes, need professional personnel to fully understand the equipment, need years of production experience accumulation. In the production process, if we want to have a high qualified rate and reduce the operation cost, we need to do the best in the operation, maintenance, overhaul and daily preparation of the equipment. For example, the choice of lining crucible material, the knotting, sintering and baking temperature of crucible will affect the life of crucible; the design of nozzle and chute, knotting and baking will affect the smooth casting and the removal of scum; the preparation and installation of furnace charge will affect the power and time of smelting; the design of ingot riser and the selection of insulation material, the way of feeding will affect the ingot. The recovery rate, the use and maintenance of vacuum pumps, the replacement of vacuum oil and so on will also affect the cost. The introduction of automation control system and intelligent man-machine operation interface will make the repeatability of equipment operation, the optimization and stability of production quality, and the qualified rate of products to a higher level.
Here, based on our years of experience in the application of vacuum induction furnaces, we would like to share some of our experiences with you.
1 Equipment maintenance
1.1 First of all, the selection of lining crucible materials should be adapted to the different types of melting. Magnesia, quartz sand and other materials commonly used have their own characteristics. It is very important to select appropriate materials, not the higher the better. The selection of crucible materials depends on experience and experiment to obtain an economical and practical crucible formula. Besides, the temperature of knotting, sintering and baking of crucibles, and the system of knotting and sintering of crucibles are very important after the selection of crucibles'materials. A good crucible has a life span of dozens or even higher, while a poor crucible can only be used several times. The cost of smelting is obvious compared with the advantages and disadvantages (for example, a 500 kg vacuum induction furnace, a crucible needs 350 kg of materials). In addition, the cleaning and repairing of medium-term crucible are also indispensable. The selection and application of repairing agent are helpful for the improvement of crucible life.
1.2 Designing and knotting and baking of nozzle and chute, prefabricated nozzle bricks are good for use, but the parts connected with crucible materials should be handled properly. Steel leakage and penetration often occur here; manual knotting of nozzle with refractory materials will solve the problem of easy cracking of connection parts and also play the role of slag blocking; the use of chute is increasing, and its service life should also be paid attention to, using prefabricated chute. Or hand-made, has an impact on the cost. The baking of nozzle and chute before use should also be done well to ensure smooth pouring.
1.3 The preparation and charging of furnace charge are usually divided into return charge and new charge. The use of return charge can reduce the cost and is especially important for products with high alloy ratio. The returned materials of the next several processes can be collected and used directly after cleaning, which meets the conditions of furnace loading. If not, the returned materials should be prepared, packed and pressed, or melted in preparation and moulding. When charging, attention should be paid to the high and low temperature zone, which should be loaded separately according to the melting point of the charge, so as to avoid the inconvenience caused by intermediate charging.
The yield of 1.4 ingot is an important index. In addition to controlling volatile furnace charge in smelting process, ingot pouring is very important. For the smelting equipment using chute for multi-mode casting, the feeding during casting is uncontrollable, so the design of ingot riser and the selection of insulation material and feeding method are particularly important, which will directly affect the yield of ingot. Using heating riser or adiabatic riser and using feeding agent are all positive measures to ensure ingot yield. For different melting varieties, economic and practical ways and methods should be found through experiments. In addition, the connection between ingot moulds should be done well in multi-mode casting.
The life of 1.5 ingot mould also affects the cost. The proper ingot shape is very important for the next process. Whether round ingot or square ingot is used, the ratio of height to width and the slope should be carefully chosen. Whether the demoulding is successful or not will also affect the life of ingot mould, and when necessary, the demoulding agent should be selected. In addition, the choice of ingot mould materials and manufacturers should also be checked.
1.6 The use and maintenance of vacuum pumps as well as the replacement of vacuum oil, vacuum pumps, whether mechanical pumps, Roots pumps or oil booster pumps, are more sophisticated and even some delicate equipment. Correct use and maintenance of them is also a very important part of reducing costs. It is necessary to operate strictly in accordance with the requirements of the product specifications and not at will; the cleanliness of the melting furnace should be maintained and the dust and debris should be cleaned up in time, otherwise the oil quality in the vacuum pump will deteriorate, directly affecting the vacuum degree and then the melting quality; as shown in Figure 3. VACUUM EFFECT OF WATER VAPOR MOISTURE (AIR IN WET SUMMER SEASON)