The IF electric furnace inspection should be done in several points:
(1) Observe the cooling water (temperature, water pressure, flow) on the internal and external circulating water system at any time.
If it is found that the water flow of a certain branch is small, seepage, blocked, or the temperature is too high, the power should be reduced, or the machine should be shut down for processing; Immediately stop melting and;
A. Start the pump with the backup power supply;
B, or start the emergency diesel generator to start the emergency cycle cooling system;
C, or open the tap water (or emergency water tank) directly into the cooling (while opening the drain), and directly discharge the water after cooling the furnace body;
D, can not be processed for a short time, the water cycle is difficult to recover, you should empty the molten iron in the furnace to avoid iron molten iron due to long-term cooling of the molten iron, difficult to remove from the furnace;
(2) Observe the various indicators on the power cabinet door of the intermediate frequency furnace at any time, and adjust the input of the intermediate frequency power in time to obtain the best melting effect and avoid low-power operation for a long time.
(3) Pay close attention to the current indication value of the leakage current indicator to grasp the change of the thickness of the furnace lining. When the pointer reaches the alarm limit value, the furnace should be stopped and rebuilt.
(4) If the protection indication appears suddenly during normal operation, first turn the power knob to the minimum position, and immediately press "Inverter stop" to find out the cause, and then start after removing it.
(5) If there is an emergency or abnormal situation, such as abnormal sounds, odors, smoke, sparks, or a sharp drop in output voltage, the output current rises sharply, and the intermediate frequency is higher than during normal operation, and the leakage current (furnace lining alarm The value fluctuates greatly. It may be that the furnace lining becomes thinner, leaks the molten iron, and the arc gate of the induction coil is short-circuited. It should be stopped immediately by pressing the "inverter stop" button and dealt with in time to prevent the accident from expanding.
(6) The power should be adjusted down when feeding and slag removal, and the variable frequency power supply must be set to the "inverter stop" position when pouring molten iron out of the furnace.
7 (7) When the cold material of the hot furnace lining is melted, it can only be charged to 50% of the height of the crucible. When the current drops to a voltage that can increase the voltage to the rated value, continue to charge the crucible. (This is because the resistance of the cold charge is small and the current is large. The regulated voltage is limited by the current and affects the power input.)
(8) During the production process, one-time charging is not allowed to be full or even beyond the furnace mouth. Because the magnetic field of the charging material above the upper end surface of the induction coil is weak, it is mainly heated by the transfer of heat from the iron liquid below, so the melting speed is slow. At the same time, because the furnace cannot be covered, a large amount of heat energy is radiated through the furnace mouth, which reduces productivity.
In addition, the crucible at the upper end of the induction coil and the furnace lining of the joint with the furnace nozzle are not easy to tamp, the furnace is not perfect, and the sintering is not good, but the mechanical vibration stress is the largest, so the furnace leakage is easy to occur in this section. Therefore, the solution surface in the crucible should be controlled to be flush with the upper end surface of the induction coil.
(9) Although the molten iron in the intermediate frequency furnace can be emptied, it is good for smelting different materials. However, if the material is not changed, it is better to leave residual liquid in the furnace. This is because the molten iron in the furnace makes it easy to join the charged materials into many large pieces, and the single pieces of material will be bridged and welded together to form a large piece, thereby increasing the melting rate. The speed of arc bridging between small pieces of charge depends on the frequency. The frequency is low, and the welding speed is low. If it is not emptied, a small part of the molten iron is left at the bottom of the furnace, and the disadvantages of using a lower frequency can be easily overcome (the frequency of the intermediate frequency furnace is not relatively high). In addition, since the residual liquid has a small load change at the initial stage of power-on, high power can be input from the beginning, and at least the melting time of the metal charge can be shortened.
10 (10) When feeding, the highest surface of the molten iron shall be prevented from exceeding the limit of 80% of the capacity, so as to prevent the molten iron from overflowing the furnace mouth during the feeding accident.
11 (11) Add the small charge first and then increase the charge.
(12) Frequently observe the melting situation in the furnace. Before the furnace material is completely melted, it should be refilled in time. It is found that the shed should be treated in time to avoid the furnace passing through because the temperature of the molten iron rises sharply and exceeds the melting point of the furnace material (quartz sand 1704 ℃).
13 (13) Slag should be picked up and temperature measured in time after the molten iron is melted.
14 (14) Under normal circumstances, the furnace should be dismantled and rebuilt when the crucible wall is 1/3 of the original furnace lining thickness.
15 (15) The molten iron shall be emptied once a week to measure the size of the furnace lining and observe its surface condition, to grasp the actual situation of the furnace lining in time, and to deal with problems if found.
(16) C-increasing agent is preferably added little by little during the process of adding the metal charge. If it is added too early, it will adhere to the bottom of the furnace and will not easily dissolve in the molten iron. Adding too late will extend the melting and heating time, which will not only cause a delay in composition adjustment, but may also cause excessive temperature. The addition of ferrosilicon (increasing Si), for medium-frequency furnaces with weak stirring power, because the high Si content in the molten iron will cause poor C-increasing properties, it is better to add Si iron later, but it will cause molten iron in the furnace. Delay in composition analysis and adjustment.
(17) Leaving liquid metal in the furnace during the melting process helps to improve the electrical efficiency of some electric furnaces and improve the power factor during the melting process. However, these molten irons may endanger the quality of the metal due to being overheated in the furnace for a long time, so the residual metal liquid should be 15% of the furnace capacity. Too little molten iron is overheating, and too much will reduce the effective use of molten iron and increase unit energy consumption.
(18) The thickness of the charge is preferably 200-300mm. The larger the thickness, the slower the melting.