Many people don't know the induction melting furnace and think it is just a casting electric furnace. However, is this really the case? Although it is indeed an intermediate frequency electric furnace for foundry, there is still a lot of information you need to know, such as: features, accessories, advantages and common sense of maintenance. The following editor will take you into the induction melting furnace .
First, the characteristics of induction melting furnace
Induction melting furnace refers to an induction melting furnace with a working frequency in the range of 150 to 10000 Hz . It has the advantages of fast melting speed, high productivity, strong adaptability, flexible use, good electromagnetic stirring, convenient start-up operation, and so on.
Induction melting furnaces are not suitable for large, medium and small furnaces with a capacity of 10 kg and dozens of tons. They are used for smelting steel and cast iron as well as non-ferrous metals such as copper and aluminum, as well as heat preservation of liquid metals. For intermittent operation, the furnace structure and usage are similar to the power frequency centerless induction melting furnace. Since the 1970s , with the increasing power and reliability of thyristor intermediate frequency power supplies with high rate, static type and saving metal materials, induction melting furnaces have developed rapidly inside and outside, not only with obvious advantages in small and medium capacity, but also in large Capacity is also replacing the power frequency centerless induction melting furnace.
Second, induction melting furnace accessories
The induction melting furnace uses a single layer of copper tube to make an induction coil, and a crucible knotted with refractory material is used in the water-cooled induction coil to contain the molten metal. Induction melting furnace usually consists of four parts: power supply, furnace body (mainly induction coil and crucible made of refractory material inside the induction coil), capacitor bank (used to improve power factor), control and operating system.
1 . Body part of induction melting furnace
(1) Induction coil of induction melting furnace: The induction coil is the heart of the induction melting furnace. The induction coil converts electromagnetic energy into thermal energy, which melts the metal charge in the crucible. Multi-turn coils made of rectangular copper tubes are spiral. , The surface is sprayed with high-strength edge paint, and bound with a band. The induction melting furnace turns are also coated with refractory cement. The induction ring is provided with a water cooling ring above and below.
Induction coil of induction melting furnace
(2) The yoke of the induction melting furnace: The yoke is made of high-quality silicon steel sheets and is distributed around the induction coil to support the skeleton. At the same time, it also plays a role of restraining the magnetic flux leakage outside the induction coil to prevent metal components from heating.
(3) Water-cooled cable for induction melting furnace: The flexible wire of the water-cooled cable is likely to be broken due to the frequent tilting of the furnace, and the loosening of the connection bolts at the wiring may cause the current imbalance. Generally, the life of the water-cooled cable is three years based on the number of tilting furnaces. After three years, it needs to be replaced. If the bolt changes color, it needs to be updated and tightened in time.
(4) Furnace lining of induction melting furnace: Induction melting furnace has high temperature during production, changes in furnace temperature, and also suffers from slag erosion and electromagnetic stirring. High-temperature molten iron directly flushes the crucible lining. The lining is easily damaged, and the furnace construction cost is high and prolonged. Induction melting furnace lining life, reducing the frequency of furnace construction is very important to reduce costs.
(5) Crucible furnace leakage alarm device for induction melting furnace: In order to ensure safe production and prevent the occurrence and expansion of furnace leakage accidents, it is helpful to judge the use of furnace linings and extend the age of the furnace. It is necessary to set a crucible furnace leakage alarm system. Generally, a DC alarm device is used, and the stainless steel wire bottom electricity (electricity) in contact with the molten iron and the stainless steel plate (grid) side electricity (secondary electricity) of the induction coil of the furnace lining are respectively installed.
2 ．Hydraulic system of induction melting furnace
It is composed of hydraulic device, console, tilting cylinder hydraulic cylinder, furnace cover hydraulic cylinder and so on. The seals of the hydraulic system should be checked regularly for leaks. If seals are found to be replaced, the rotating parts should be regularly lubricated with oil (rotary self-lubricating spherical bearings for tilting furnaces, which must be added to the old ones when filling with grease). Until the oil overflows), otherwise it is easy to cause damage.
3 ．Water cooling system for induction melting furnace
Ensure the cooling water quality and regularly check for scale. If there is scale, it should be cleaned immediately to ensure cooling fruit. Cooling water quality requirements as frequency furnace: the pH value of 6 ~ 9 , the hardness of <10mg equivalent / L , the total solids of not more than 250 mg of / L , the coolant temperature rise <25 deg.] C; cooling water for a water supply IF : PH value is 7 to 8 , hardness is less than 1.5mg equivalent / L , suspended solids: 50mg / L , resistivity is more than 4000 Ω · cm . The circulating water in the circulating pool should be tested regularly. When the hardness of the circulating water exceeds 2 mg equivalent / L , the circulating water in the system should be emptied and replaced again. The cooling water tower should be drained regularly and replaced with new soft water to prevent the pipes and nozzles from being blocked, which will affect the life of the cooling fruit and the furnace lining.
4 . Electric control system of induction melting furnace
The main circuit and the induction coil should regularly clean the surface of the dust. The conductive metal dust and iron beans splashed during the tapping on the foundry workshop will fall on the surface of the main copper bar or the induction coil, which will cause its edge capacity to decrease, causing sparks and ignition, which may cause Electrical components are damaged. It can be blown off with compressed water that does not contain water. The main circuit copper bar connection screws also need to be inspected and fastened regularly, otherwise, due to the increase in contact resistance, a large amount of heat will be generated at the connection, causing the edge material to carbonize and cause leakage.
Third, the advantages of induction melting furnace
Compared with power frequency centerless induction melting furnace, induction melting furnace has the following advantages.
(1) At the same capacity, the input power of the induction melting furnace is high, which can be 2 to 3 times that of the power frequency furnace , thereby greatly improving the melting rate of the furnace and reducing the power consumption.
(2) No residual melt and large frit are needed, and it can be melted at any time to reduce power consumption.
(3) The pouring part or part of the melt can be poured each time, so the operation flexibility is greater.
(4) The power is convenient, and it can meet the different requirements for power during melting, heat preservation and oven.
(5) During operation, the operating frequency changes with the resonance frequency of the load circuit, and automatically maintains the load circuit with a high power factor. It is not necessary to adjust it by increasing or decreasing the load capacitance like a power frequency furnace.
(6) Three-phase balance of power frequency input. It is not necessary to set LC three-phase balance device like the power frequency furnace .
(7) With the same output, the capacity of the induction melting furnace is small, so the area is greatly reduced, infrastructure investment is reduced, and space utilization is improved.
Fourth, the maintenance of induction melting furnace
The maintenance work of the induction melting furnace is very important. It can discover various hidden dangers in time, avoid major accidents, prolong service life, ensure safe production, improve casting quality and reduce costs. Regularly record the relevant electrical parameters, cooling water temperature and the temperature of the shell (furnace bottom, furnace side, induction coil shell, copper bar, etc.) of the key parts of the furnace body, and can monitor the use of the electric furnace at any time. Start diesel generators regularly to ensure reliable operation.
1) Periodically maintain, lubricate and tighten the electric furnace according to the prescribed time (for example, use system of dry compressed air to remove dust from induction coil, copper bar, electric control cabinet, etc .; lubricate all lubricating parts; tighten bolts).
2) Observe the water pressure gauge, water temperature gauge and the aging degree of the water delivery hose every day; regularly check the flow of each cooling water branch to ensure that the pipeline is not blocked and the pipe joints are not leaking, especially the cooling water joints in the solid power cabinet. If water leakage is not allowed, you can tighten the pipe joint clamps or replace the clamps; regularly check the amount of water stored in the water spray tank, expansion tank, power cabinet, and water tank, and replenish the water in time; often Check the status of the standby pump, and use the standby pump every 3 to 5 days to ensure the reliable operation of the standby pump.
3) Check if the capacitor is leaking oil. If oil leaks from the capacitor terminals, use a wrench to tighten the nuts on the bottom of the terminals.
4) Mid-term maintenance. Use ethanol to grind the porcelain edge of the AC incoming line, the bracket, the second tube of the rectifier section, the bracket, the capacitor porcelain edge, the IGBT (triac) main contact part, the inverter and the intermediate frequency AC copper bar, etc .; replace the electrical cabinet part Aging water delivery pipe, dredging the neck of the water nozzle, IGBT (triac) water cooling block, replacing the AC copper drain board, individual capacitors, etc.