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1. Preparation before opening the furnace
(1) Check the lining, the thickness of the lining (excluding the asbestos wrench) must be repaired when the wear is less than 65-80 mm;
(2) Check for cracks. Cracks of more than 3 mm shall be filled into the lining material for repair;
(3) Make sure that the cooling water is unblocked.
2. Adding instructions
(1) After placing the furnace cover, check whether the furnace block is actually placed on the bottom of the furnace;
(2) Do not let the damp charge be placed. When it is absolutely necessary, after putting the dry charge, put the wet material on it, and use the heat drying method in the furnace to evaporate the water before the furnace;
(3) The chip material should be placed on the residual iron liquid after the iron is discharged. One input is less than one tenth of the furnace volume, and must be evenly invested;
(4) Do not add tubular or hollow charge. This is due to the danger of explosion due to the rapid expansion of air;
(5) Regardless of the charge, the next melt is injected before the last charge is not melted.
(6) If the rust and sand-filled charge are used, or if too much cold material is added at one time, it is prone to “bridge”. When the liquid level is frequently checked to avoid “bridge”, the lower iron will overheat, causing the lower lining. Erosion and even leakage of molten iron.
3. Management of molten iron temperature
The tapping temperature should not exceed the required value. Too high a temperature of the molten iron greatly reduces the life of the lining. Since the reaction in the acid lining is as follows: SiO2 + 2 [C] [Si] + 2CO The reaction proceeds rapidly when the molten iron reaches 1500 ° C or higher, and the composition of the molten iron also changes. The carbon element is burnt and the silicon content is increased.
Third, the accident handling method
The accident is unpredictable. For a very serious accident that occurs suddenly, it must be calm, calm, and properly handled to avoid accident expansion and narrow the scope of influence. Therefore, it is necessary to be familiar with the accidents that may occur in induction furnaces and the correct treatment of these accidents.
1. power failure
The induction furnace is powered off due to an accident such as overcurrent or grounding of the power supply network or an accident of the induction furnace itself. When the control loop is connected to the same power source as the main circuit, the control circuit pump also stops working. If the power failure can be recovered within a short period of time and the power outage time does not exceed 10 minutes, you do not need to use the backup water source, just wait for the power to continue. However, at this time, the standby water source is ready for operation. In case the power outage is too long, the sensor can be connected to the standby water source immediately.
If the power is off for more than 10 minutes, you need to turn on the backup water source.
The heat conducted from the molten iron is large due to power failure and the supply of the coil is stopped. If water is not supplied for a long time, the water in the coil may become steam, destroying the coil cooling, and the insulation of the hose and the coil connected to the coil are burned out. Therefore, for long periods of power outages, the sensor can be turned to industrial water or a gasoline engine water pump. Since the furnace is in a power outage state, the amount of water passing through the coil can be 1/3 to 1/4 of the energization smelting.
The power outage time is less than 1 hour, cover the molten iron surface with charcoal to prevent heat dissipation, and wait for the power to continue. In general, there is no need to use other measures, and the temperature drop of the molten iron is also limited. A 6-ton holding furnace was powered down for one hour and the temperature dropped by only 50 °C.
The power outage time is more than one hour. For small capacity furnaces, the molten iron may solidify. It is best to switch the power of the oil pump to the backup power source when the molten iron is also fluid, or to pour the molten iron out with a manual backup pump. If the residual iron is solidified in the crucible. However, for various reasons, the molten iron can not be poured out temporarily, and some ferrosilicon can be added to lower the solidification temperature of the molten iron and delay the solidification speed. If the molten iron has begun to solidify, it should try to destroy the surface crust layer, make a hole, and open it to the inside to facilitate the gas to be re-melted to remove the gas and prevent the gas from expanding and causing an explosion accident.
If the power failure time takes more than one hour, the molten iron will completely solidify and the temperature will drop. Even if it is re-energized and melted, an overcurrent will occur and it may not be energized. Therefore, it is necessary to estimate as soon as possible, judge the power outage time, power outage for more than one day, and release the iron before the melt temperature drops as early as possible.
When the cold charge begins to melt, a power outage occurs. The charge has not completely melted. It is not necessary to tilt the furnace, and it will remain in its original state. Only the water will continue to flow, waiting for the next power-on time to re-melt.
2. Leakage
Leakage accidents can easily cause equipment damage and even endanger people. Therefore, it is necessary to do the maintenance and maintenance of the stove as much as possible to avoid leakage accidents.
When the alarm bell sounds, immediately cut off the power and inspect the area around the furnace to check if the molten iron leaks. If there is a leak, immediately tilt the furnace and pour the molten iron. If there is no leakage, check and handle according to the leak alarm check procedure. If it is confirmed that the molten iron leaks from the lining and hits the electrode, the iron liquid is poured out, the lining is repaired, or the furnace is rebuilt.
The leakage of molten iron is caused by the destruction of the lining. The thinner the thickness of the lining, the higher the electrical efficiency and the faster the melting rate. However, when the thickness of the lining is less than 65 mm, the thickness of the lining is almost always a hard sintered layer and a transition layer. Without a loose layer, the lining is slightly quenched and quenched to produce fine cracks. This crack can crack the entire interior of the lining, and it is easy to cause the molten iron to leak out.
For unreasonable methods of furnace building, baking, sintering, or improper selection of lining materials, a leaking furnace will be produced in the first few furnaces of melting.
3. Cooling water accident
(1) The temperature of the cooling water is too high due to the following reasons: the sensor cooling water pipe is blocked by foreign matter, and the flow rate of water is reduced. At this time, it is necessary to power off and use a compressed air blowing water pipe to remove foreign matter. The pump stop time should not exceed 15 minutes. Another reason is that the coil cooling water channel has scale. According to the water quality of the cooling water, it is necessary to block the scale on the coil water channel every 1-2 years, and it is necessary to pick it up in advance.
(2) The sensor water pipe suddenly leaks. The cause of water leakage is mostly caused by the insulation breakdown of the water yoke or the surrounding fixing bracket. When this accident is discovered, it should immediately stop power, strengthen the insulation treatment at the breakdown, and seal the surface of the leak with epoxy resin or other insulating glue to reduce the voltage. The furnace is hydrated, and the furnace is repaired after the completion. If the coil water channel is broken down in a large area and the gap cannot be temporarily sealed with epoxy resin, it is necessary to stop the furnace, complete the molten iron, and repair it.
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