0.75 ton medium frequency furnace

Furnace building and drying and maintenance technology

First, build the furnace

1, crucible refractory material

Crucible refractory confirmation: Choose Hubei Anaijie Lining Material Co., Ltd. neutral lining material, must be the material supplier's product name and model confirmation before use.

 Equipment inspection;

Before building the furnace, the electric furnace equipment should be tested for water and pressure, trial operation, and the furnace body tilting check, and the furnace can be laid and built after confirming that it is correct.

2. Install alarm system

3. Tie the bottom of the furnace

a Add 8 bags at one time and then flatten. Use the vibrating fork to fork 3-4 times from the outside to the inside, taking 12-15 minutes. Pay attention to the principle of orderly, crossed and even. Then use the circular flat hammer from the center to the outer circle in the form of spiral vibration 2 times, taking 3-6 minutes, the flat hammer requires the second hammer pressure... 1/3 of the hammer, not missing the hammer. After ramming, scrape the surface loosely with a fork for 5-10㎜ to facilitate the interlocking between layers and prevent delamination.

b Level the bottom of the furnace with a level and wooden board.

4. Place the crucible mold

a Crucible mold error ≤5mm. The circular shape of the crucible die will cause the wall thickness of the crucible to be uneven, and the crucible die must be re-trimmed to make it conform to the requirements of the drawing.

b Crucible mold exhaust hole diameter is 3-6mm, spacing is 150-200mm; If the mold is rusted, it can be used after grinding with sandpaper.

c When placing the crucible die, pay attention to ** the wall thickness of the crucible is consistent and concentric with the coil, and the weld is left in the back half and the front side. Thick.

d Fix the crucible mold with three wooden wedges.

5. Fill the crucible wall

a Be sure to loosen the material that is in contact with the wall of the crucible at the bottom by 5-10㎜!

    b Add refractory materials, must carefully check each layer, be careful not to let any packaging debris and other debris mixed into the lining material!

    c If the lining material enters between the laying materials, it must be completely removed. If it cannot be removed, all the lining materials must be removed.

    d Crucible wall... Layer 2 bags of feed, feed and then flatten. Then use the vibrating fork 3-4 times, taking 12-15 minutes, pay attention to the principle of order, cross and uniform. Use the side hammer to vibrate twice, which takes 3-6 minutes. When the side hammer vibrates, avoid damaging the asbestos cloth. After shaking, loosen the surface 5-10㎜.

    e From the second floor to the top of the furnace, repeat the above operation.

    f Knot to 1/2 height above, can remove wedge block.

    g The lining must be finished at one time, it is strictly prohibited to stop beating, because this material has strong moisture absorption, coupled with large dust and debris in the casting workshop, which affects the life of the lining.

    6. Construction of furnace nozzle

    A layer of 10-20mm lining material can be laid on the lower part of the burner, and other parts can be constructed by adding water glass and water to the lining material.

    Second, the oven

    1. Insert the K-type thermocouple by the crucible wall and make it. Lower end ** In the middle and lower part of the crucible die.

    2. Add 1/3 of the pulverized material to the furnace manually, and arrange steel bars all around.

    3. Cover the crucible mold with asbestos cloth or furnace cover, leaving only a row of pores, so that the entire furnace lining is heated evenly.

    4, must be full furnace sintering, liquid surface. The height reaches about 100㎜ from the furnace to facilitate the whole sintering.

    5, sintering specifications (refer to the oven diagram)

    a Heat the charge to 900℃ at 300℃/h.

    b Heat at 900℃ for 2 hours.

    When the c temperature reaches about 1050 ° C, be sure to take out the K-type thermocouple.

    d Continue to increase the power, so that the charge begins to melt, and the steel is quickly filled. When the temperature reaches 1500℃, remove the slag in time. Low power heating up to 1630℃(±20℃).

    e is insulated at 1630℃(±20℃) for 1h.

    f When the temperature of molten steel is greater than 1500℃, the temperature is generally monitored every 10 minutes.

    g Start charging when the initial charge melting reaches about 90%.

    h Each feeding should be carried out before the last material is completely melted, taking care not to produce the phenomenon of shed material, continue to add material to the full furnace.

    6. Occurrence and treatment of hanging materials in the smelting process:

    a The melting process should be carefully added, pay attention to observe the furnace condition, so as to avoid the phenomenon of hanging.

    b The temperature of molten metal in the molten pool under the hanging material is too high, which can cause rapid ablation of the furnace lining and the risk of explosion at any time.

    c After the occurrence of hanging material, the power supply should be reduced to 25% of the insulation power to prevent the molten metal from overheating.

    d At this time, the furnace body must be tilted so that the molten metal is in contact with the hanging material and a hole is melted.

    e Turn the furnace body so that it returns to the upright position, and feed through the holes so that the molten metal comes into contact with the hanging material and melts it. Note: Do not overheat the melted metal when performing this step.

    3. Maintenance process

    1, the crucible early use, the sintered layer is thin, should try to avoid high-power power, produce excessive electromagnetic stirring, so that the furnace lining damage, usually within the first 48h does not exceed 60-80% of the total power.

    2, when feeding, should try to avoid the material hit the crucible, so that the crucible is damaged. Especially after the cold furnace, the strength of the crucible is very low, and mechanical feeding is strictly prohibited. Artificial feeding should also be particularly careful to prevent the increase of cracks, resulting in increased infiltration of metal liquid, resulting in furnace leakage accidents.

    3, after the furnace sintering is completed, the operator is required to have a strong sense of responsibility, always pay attention to check the lining condition, and keep the whole system in good condition.

    4, after the completion of the intermediate frequency furnace, regardless of any reason, the cooling water system should be recycled for about 12h, while the temperature in the furnace is below 200 ° C, otherwise it will lead to damage and even scrap of the furnace lining and induction coil.

    5, in the operation process or empty furnace, the crucible temperature is still very high, should reduce the opening times and time of the furnace cover, in order to reduce heat loss and furnace lining cracking.

    6, normal production should be full furnace, prohibit half furnace production. Lest the temperature difference is too large to crack.

    7, normal melting should be the side of the material melting, do not allow the molten steel after clearing and then add material. In particular, the amount of scrap added is too large, resulting in large fluctuations in the liquid level of molten steel, and the molten steel is easy to penetrate into the unhealed lining above the liquid level, causing accidental penetration.

    8, the newly rammed lining should be used continuously at least 3-6 furnaces, which is conducive to the formation of a sintered layer of sufficient strength.

    9, lining cooling method:

    a After the molten steel, immediately put in a number of fragments, so that the furnace lining natural cooling.

    b The molten steel is emptied and cooled naturally.

    c Molten steel is emptied and drained, and cooled quickly with fans and air pipes.

    Suggestion: Use method a for cooling.

    10. The furnace lining should be managed by special personnel

    a Before starting the furnace, someone must confirm and agree before starting the furnace.

    b After melting a furnace, someone needs to check the degree of erosion of the furnace lining in time to determine whether the furnace lining can continue to be used and to repair it in time. Once it is found that the furnace condition is poor, affecting the safety of production, the furnace should be stopped immediately, and the relevant authorities should be notified in time.

    c furnace nozzle and furnace lining joint, easy to crack, easy to leak, each time before opening the furnace should be carefully observed, take remedial measures in time.

    d. The furnace collar and lining materials made with KS-01 have cracks due to different expansion coefficients, which should be repaired in time to avoid puncture caused by delamination.

    e. When cooling, cracks ≥2㎜ to be repaired in time.

    11. Determine whether the furnace lining is removed:

    a When the thickness of the lining is less than 30-40㎜, it must be removed.

    b When the furnace lining alarm current is too large, confirm the alarm device to operate without error, at this time need to disassemble the furnace.

    c When under a certain rated DC voltage, the weight of molten steel in the early and late stages is equal, the lining has no obvious local erosion, and the DC current rises by 15-20%, the lining must be removed. In the process of use, if the DC ammeter and DC voltmeter are shaken greatly, or it is found that the DC ammeter continues to rise and the DC voltmeter continues to fall, it is proved that the furnace lining has leaked, and emergency measures need to be taken immediately.

    12 If the smelting is finished, the furnace is not allowed to leave liquid steel, to avoid large temperature difference between the furnace body and the crucible strain, resulting in cracks.

    13, crucible cold lining is not... Smelting operation requirements (cold furnace startup depends on shutdown time) :

    a. Add 1/3 of the crushed material in the furnace, and arrange steel bars all around.

    b Cover the furnace and heat the metal charge in the furnace to 900℃/h.

    c Heat at 900℃ for 1h. During this time, no liquid metal is allowed!

    d After the end of insulation, it can be melted normally.

    e Adding order of various charges in the melting process: first add the charge with low melting point and small element burning loss, and then add the charge with high melting point and large element burning loss, ferroalloy. Then join.

    f Special attention should be paid to the charging: cold wet charge and galvanized charge should be added to other charges to slowly enter the liquid steel to avoid splashing of the liquid steel. It is strictly forbidden to mix shell cases, sealed tube heads and other explosive items in metal charge.