What should be paid attention to to ensure safety during the smelting process of the induction melting furnace?
1. Routine operation of induction melting furnace
(1) The on-site personnel should wear labor protection products in strict accordance with the company's regulations, and use special filters when observing high-temperature metals.
(2) The furnace lining should be checked frequently at certain time intervals to prevent "exhaustion". Check the furnace lining after cooling: if the thickness of the furnace lining (excluding asbestos board) is less than 65mm～80mm after burning, the furnace must be repaired. If there is no abnormality, about 250 furnaces are forcibly removed. Feeding should be careful and meticulous, so as to avoid the occurrence of "bridge" and "cap" of the material. The ultra-high temperature of the metal below will cause the corrosion of the furnace lining to accelerate.
(3) The charge should be dry, free of combustibles, airtight containers, and not excessively rusty. The violent boiling of liquid or combustibles in the charge can cause molten metal to overflow or even explode.
(4) There should be no accumulated water in the pit in front of the furnace to prevent the molten iron from splashing and exploding after being poured.
2. Feeding method of induction melting furnace
(1) Regardless of the charge, put the next melt slowly before the previous charge is melted. If the charge with a lot of rust and sticky sand is used incorrectly, the block size and shape of the charge are not good, the charge is not packed tightly and the build-up is serious, or if too much cold charge is added at one time, "bridging" is likely to occur. The liquid level must be checked frequently, and the bridge should be dealt with as soon as there is a bridge, and the "bypass" must be smashed to avoid the formation of the "bypass". Otherwise, the molten iron at the lower part will overheat, causing corrosion of the lower furnace lining, and even leakage or explosion of the molten iron.
(2) Bridge treatment method: reduce the melting current to below 500A; poke it with an iron rod; if it is not disposed, turn the electric furnace appropriately and keep the melting at low power until the molten iron breaks the bridge or the capping layer;
(3) After the furnace charge is completely melted, the slag should be removed immediately to prevent the formation of "slag caps". If a "slag cover" is formed, power off immediately and break the "slag cover" out of the furnace, otherwise the molten iron at the lower part will overheat, causing erosion of the lower furnace lining, and even leakage or explosion of the molten iron
3. Emergency treatment of smelting in induction melting furnace
1. The power went out
(1) Emergency treatment of cooling water
1) The dual power switch in the main power distribution cabinet of the electric furnace control room should be kept in the self-switching position. When the main power supply fails, the security power supply will automatically cut in, and then immediately restart the furnace water pump;
2) When the main power supply and the security power supply are cut off at the same time, immediately notify the electrician on duty, and prepare to start the emergency generator to ensure that the small water pump of the furnace body is powered and the furnace body cooling water is run. Therefore, diesel generators must be guaranteed to have a certain amount of diesel oil, and run together with the equipment once a month;
3) When the diesel generator cannot be started, tap water into the furnace body immediately;
4) Due to the power failure, the water supply of the coil is stopped, and the heat conducted from the molten iron is very large. If there is no water flow for a long time, the water in the coil may turn into steam, destroying the cooling of the coil, and the hose connected with the coil and the insulation of the coil will be burned out.
(2) Emergency treatment of molten iron in the furnace
1) A power outage occurs during the period when the cold charge starts to melt, and the charge has not been completely melted, do not need to be dumped, keep it as it is, just continue to flow water, and wait for the next time the power is turned on to restart;
2) Due to the failure of the intermediate frequency power supply, the molten iron has melted, but the amount of molten iron is not large and cannot be poured (the temperature is not reached, the composition is unqualified, etc.), you can consider turning the furnace to a certain angle and then solidify naturally. If the quantity is large, consider dumping the molten iron;
3) Due to the sudden power failure, the molten iron has melted, try to insert a pipe in the molten iron before the molten iron solidifies to facilitate the removal of gas when it is remelted, and to prevent the gas from expanding and causing an explosion;
4) When the solidified charge is energized and melted for the second time, it is best to tilt the furnace forward at a certain angle, so that the molten iron underneath can flow out part of the inclined lower part to prevent explosion.
2. Hot metal leaking from induction melting furnace
Liquid iron leakage accidents can easily cause equipment damage and even endanger humans. Therefore, it is necessary to do the maintenance and maintenance of the furnace as much as possible to avoid liquid iron leakage accidents.
(1) When the alarm bell of the furnace lining thickness measuring device rings, the power supply should be cut off immediately, and the surroundings of the furnace body should be inspected to check whether the molten iron leaks. If there is any leakage, dump the furnace immediately and finish pouring the molten iron.
(2) If the molten iron has been found, evacuate the personnel immediately and pour the molten iron directly into the pit in front of the furnace;
(3) The molten iron leakage is caused by the destruction of the furnace lining. The smaller the thickness of the furnace lining, the higher the electrical efficiency and the faster the melting speed. However, when the thickness of the furnace lining is less than 65mm after wear, the entire thickness of the furnace lining is almost always a hard sintered layer and a very thin transition layer. There is no loose layer, and small cracks will occur when the lining is slightly subjected to rapid cooling and heating. The crack can penetrate the entire furnace lining and easily cause the molten iron to leak out.
(4) When furnace leakage occurs, the safety of personnel should be ensured first. When considering equipment safety, the equipment mainly considers the protection of induction coils. Therefore, if furnace leakage occurs, the power supply should be turned off immediately and the cooling water should be kept unblocked;
3. The cooling water temperature is too high
(1) The sensor cooling water pipe is blocked by foreign matter, which causes the water flow to decrease and the cooling water temperature is too high. At this time, it is necessary to cut off the power first, and then use compressed air to purge the water pipe to remove foreign objects. It is best not to stop the pump for more than 8 minutes.
(2) The coil cooling water channel has scale, which causes the water flow to decrease and the cooling water temperature is too high. According to the water quality of the cooling water, the obvious scale on the coil waterway must be pickled in advance every one to two years.
(3) The sensor water pipe suddenly leaks. This water leakage is mostly caused by the insulation breakdown between the inductor and the water-cooled yoke or the surrounding fixed support. When this accident is discovered, the power should be cut off immediately, the insulation treatment of the breakdown area should be strengthened, and the surface of the leakage area should be sealed with epoxy resin or other insulating glue to reduce the voltage for use. The hot metal in this furnace should be hydrated, and the furnace can be repaired after it is poured. If the coil channel is broken down in a large area, the gap cannot be temporarily sealed with epoxy resin, etc., so the furnace has to be shut down, molten iron is poured, and repaired.