First, Check the intermediate frequency melting furnace before starting
1.1 When entering the worksite, you must wear labor protective equipment correctly.
1.2 Before opening the furnace, check the corrosion of the furnace lining, confirm that the furnace lining is intact and reliable, and then add material for opening the furnace to melt.
1.3 Before the operation of the furnace, it is necessary to ensure that the worksite is free of water and sundries.
1.4 Before running the furnace, start the cooling water pump to open the cooling water valves of all channels and check whether the cooling water channels are smooth, whether there is leakage, and whether the pressure of the total inlet water pipe reaches the required value.
1.5 Check whether the driving is normal and the crane has no cracking and other phenomena to prevent accidents.
Two, The intermediate frequency melting furnace operation process
2.1 Add a part of raw materials (scrap steel) into the furnace.
2.2 The furnace change switch is closed.
2.3 Close the main circuit switch of the frequency conversion device.
2.4 Power the signal protection cabinet and tilting furnace control cabinet, and check whether the instruments and indicating signals are normal.
2.5 The inverter power supply of the IF furnace can increase the power of the IF furnace. At the same time, the working condition of the inductor and other charged equipment can be observed.
2.6 Feeding equipment shall be operated by special personnel, and other personnel shall not use it casually. Before feeding, check the electronic scale and pound scale, and check the feeding equipment.
2.7 In strict accordance with the batching list issued by the special worker of the branch, and in accordance with the prescribed feeding order.
2.8 Burden charging should be especially careful to avoid damage to lining.
2.9 In the first ten minutes of the power should be added a small power (generally 40 ~ 60% of the total power), in order to prevent the current fluctuation is too large. After this period of time, the current tends to be stable, can be high power melting, until the charge melt up.
2.10 Frequent charging should be carried out in the melting process, and attention should be paid to avoiding the phenomenon of “bridging” caused by the crowding of charge. When most of the charge is melted, slag-making materials should be added, and the slag is covered on the surface of molten steel for easy extraction.
2.11 The method of deoxidizing agent (ferromanganese, ferrosilicate) directly added to liquid steel for deoxidizing (precipitation deoxidizing method) is generally adopted in acid furnace non-oxidizing steelmaking. General addition of 0.5% ferromanganese and ferrosilicon respectively. Deoxidizer in bulk can sink into the molten steel for the best.
2.12 Melting temperature is 1600℃ (under normal circumstances). Specific time according to the specific process requirements.2.13 Final deoxidization must be carried out before steel drawing. Aluminum can be inserted into the furnace or aluminum can be added in ladle with 0.1% final deoxidization amount when conditions are available.
2.14 All slag in the furnace should be removed before drawing, and thermal insulation slag agent should be added to the surface of molten steel after drawing. The steel temperature is generally 1600℃. The pouring bag should be fully baked to ensure that the inside of the bag is clean and dry.
2.15 It should be noted that during the steelmaking process all materials added to the furnace must be dry. The slag-making materials and ferroalloys should be baked at high temperature so as not to bring gas into the molten steel.
2.16 Samples can be taken for pre-furnace analysis after all the charge is melted.
2.17 There must be an appropriate margin for each discharge of molten metal.
2.18 When stopping the furnace, the rapid cooling and rapid heating of the furnace lining should be minimized to make the furnace lining cool evenly and slowly.
2.19 Record melting.
2.20 When spheroidizing and inoculation is needed, inoculant and spheroidizing agent must comply with the Standard for Foundry Rraw Materials, and the amount and specification of inoculant shall be strictly in accordance with the process requirements.General 75 ferrosilicon is about: 0.5 ~ 0.3%.Grain-size before the furnace breeds 3 ~ 8㎜ and 5 ~ 12㎜.With the flow of 0.5 ~ 1.2㎜ and 1 ~ 3㎜ two. In the process of spheroidizing, the furnace temperature, the specification of spheroidizing agent, the amount of spheroidizing agent, the spheroidizing process, the type of spheroidizing agent and the selection of brand are strictly controlled according to the process requirements. The general addition amount varies according to the wall thickness, structure and material of the casting, and the general range is 1.0 ~ 1.8%. The temperature of molten iron treatment is 1450 ~ 1500℃, and the amount of inoculation (with flow) added is generally 0.4 ~ 0.7%.In order to obtain high casting temperature (1380 ~ 1450℃) in EPC production of ductile iron, the first thing to do is to increase the temperature of spheroidization, and the high temperature spheroidization is easy to produce poor spheroidization, strict standard operation and spheroidization process details control, to ensure the stability of the spheroidization.
2.21 In the process of melting, when the furnace is found to have a fault or stop the furnace, it is necessary to adjust the power adjustment knob of the IF inverter power supply to make the power back to zero before disconnecting the main circuit switch and the main switch of the control power supply. It is strictly prohibited to suddenly disconnect the main circuit switch and the main switch of the control power supply before the power is back to zero.
2.22 During the melting process, the backwater temperature of the circulating water distributor should not be higher than 35℃.
2.23 After the steel and molten iron are released, the furnace must be tilted back and reset.
2.24 In the smelting process, the furnace shell has certain inductive electricity, so the furnace workers should wear insulating gloves, insulating shoes, insulating pads on their feet and protective masks on their heads. It is strictly prohibited to operate with wet hands, so as to ensure safe production.
2.25 After smelting, the molten iron, and impurities in the furnace shall be cleaned up, and then the furnace shall be cut off, and the induction coil shall reduce the water pressure to supply water. When the furnace is completely cooled to room temperature, the circulating water shall be stopped and the power supply of the water pump shall be disconnected.
2.26 Check the condition of equipment at any time during work, stop the machine immediately if any abnormal situation is found, and inform the relevant team to carry out maintenance and treatment.(The equipment defect notice formalities need to be handled, you can work first, and then go through the formalities.)
2.27 In case of failure that cannot be recovered within 10 minutes, the emergency plan formulated by the Company shall be started to ensure the safety of equipment (large furnace, etc.) and prevent accidents.
2.28 After the work is completed, turn off the power of all devices.2.29 Clean up the work site and keep the site clean and tidy.
Third，routine maintenance and overhaul of intermediate frequency melting furnace
3.1 Regularly check whether the sealing of the water cooling pipe joint of the intermediate frequency furnace is firm
When tap water and well water are used as the cooling water source of induction heating equipment, scale is easy to accumulate, which affects the cooling effect. When plastic pipe aging produces crack, should be replaced in time. When the medium frequency electric furnace unit is running in summer, the condensation phenomenon often occurs when the tap water well water is used for cooling, so the closed water circulation cooling system should be considered. The operation should be stopped when the condensation is serious.
3.2 Regularly check whether the wiring of intermediate frequency furnace load is good and whether the insulation is reliable.
Clean the dust in the IF power cabinet regularly, especially the outside of the SCR tube core, and wipe it clean with alcohol. The frequency conversion device in operation generally has a special room, but the actual operating environment is not ideal. In the smelting and forging process, the dust is very large and the vibration is strong. In the diathermy quenching process of medium frequency furnace, the device is often close to the operation equipment such as pickling and phosphating, and there are more corrosive gases, which will damage the components of the device and reduce the insulation strength of the device. When the dust accumulation is large, the surface discharge phenomenon often occurs. Therefore, attention must be paid to frequent cleaning of the original surface dust, to prevent the occurrence of failure.
3.3. Periodic maintenance of the intermediate frequency furnace device
Check and tighten the pressing of bolts and nuts in all parts of induction heating equipment and devices. If the contact of the contactor relay is loose or has bad contact, it should be repaired and replaced in time. Do not avoid strong use to prevent more accidents.
3.4. Test the rated voltage and current of the intermediate frequency furnace
This periodic inspection can prevent circuit failure. To be very good for the medium frequency electric furnace regular care, this maintenance is the key to increase the service life of the medium frequency electric furnace and is an important premise to ensure the personal safety of the operator. Because the whole working environment of the medium-frequency electric furnace is carried out under the conditions of high temperature, high pressure and strong current, it is necessary to regularly clean and clean the room of the medium-frequency electric furnace.
Four, Safety precautions:
4.1 Before the operation of the furnace, it is necessary to ensure that the working site is free of water and sundries.
4.2 It is strictly prohibited to suddenly disconnect the main circuit switch of the furnace and the main switch of the control power supply before the power is back to zero.
4.3 In the steelmaking process, all materials added to the furnace must be dry. The slag-making materials and ferroalloys should be baked at high temperature so as not to bring gas into the molten steel. All kinds of metal charge according to the process requirements, unqualified charge is not allowed to use.
4.4 In case of any change in pig iron, ferrosilicon, ferromanganese and scrap steel, the technician shall be informed in time and the user shall be allowed.
4.5 All kinds of materials transported to the site shall be stacked neatly according to the requirements. Materials with different components shall be labeled and shall not be mixed.
4.6 When preparing materials, check carefully. Any suspicious items should be dealt with in time and reported to relevant personnel. It is strictly prohibited to add explosives and other harmful substances into the furnace.