40 tons medium frequency furnace

Furnace building and drying and maintenance technology

First, build the furnace

1, crucible refractory material

Crucible refractory confirmation: to purchase acidic furnace lining materials from Hubei Anaijie Furnace Lining Materials Co., LTD., it is necessary to confirm the product name and model of the material supplier.

 Equipment inspection;

Before building the furnace, the electric furnace equipment should be tested for water and pressure, trial operation, and the furnace body tilting inspection; The new paste should be dried and baked permeable, and the furnace can be laid and built after confirmation.

2. Install alarm system.

3. Tie the bottom of the furnace.

a.. Layer 25cm, then flatten. Use a vibrating fork to fork 3-4 times from the outside to the inside, taking 25-30 minutes. After compaction, scrape the surface loosely with a fork for 5-10㎜ to facilitate the mutual bite between layers and prevent delamination.

b Add 20cm to the second layer, same method as above.

c Lift the vibrating plate into the furnace and slowly lower it so that it is centered on the bottom of the furnace, and relax the hook downward to completely press the vibrating plate into the bottom of the furnace. Open the air valve and check again whether the pneumatic vibrator is secure. Adjust the air valve to make the vibrator work normally, and the continuous supply pressure of compressed air is ≥0.6Mpa. The vibration time is about 20-30min. Vibrate in four directions for about 5 minutes in each direction. During the period, the air pressure should be alternately changed several times to change the vibration frequency, so that the whole furnace bottom can obtain satisfactory vibration effect. During the vibration period, the furnace construction personnel should strictly prevent the vibration plate from running off.

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

d Near the end of the vibration, turn on the vibrator at a low speed. Then close the air valve, slowly lift the vibration plate of the furnace bottom, and check the furnace density of the furnace bottom lining material.

Note: (If there is no vibration plate at the bottom of the furnace, use a hammer hammer to screw around to the middle, repeat twice).

e Use a trowel to scrape off the excess height of the lining material, and use a level and wooden board to level the bottom of the furnace.

4. Place the crucible mold

a crucible mold error ≤5㎜. 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, when placing the crucible mold, pay attention to the crucible wall thickness is consistent and concentric with the coil, and the weld is left in the back half and the front side. Thick.

c. Fix the crucible mold with three wooden wedges.

5. Fill the crucible wall

a, be sure to loosen the bottom of the material in contact with the crucible wall 5-10㎜!

b, add refractories, 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 needs to be completely removed. If it cannot be removed, all lining materials must be removed.

d. Add 12cm material to each layer of the crucible wall, and scrape flat after adding material. Then use the vibration fork 3-4 times, taking 12-15 minutes, and then use the flat hammer to hammer twice, the next hammer to press half of the previous hammer, pay attention to the principle of order, cross, uniform.

e, from the second layer to the top of the furnace, repeat the above operation.

f, knot to 1/3 height, can remove the wedge block.

g, the lining must be completed 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. Burner

The lower part of the furnace nozzle can be laid with a layer of 10-20㎜ lining material dry material, and other parts can be constructed with water glass and water lining material.

7. Promote the crucible mold, the crane hook is in the middle of the crucible, and the point type pulls up the crucible.

8. After the crucible mold is pulled out, the furnace wall is diluted with 1/3 water glass and 2/3 water and evenly sprinkled in the furnace wall.

Second, the oven

1, the furnace wall is covered with color steel tiles, so as not to scratch the furnace wall.

2. Add shavings and scraps into the furnace.

3. Cover the furnace 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 specification:

a. Slowly increase the power until the shavings and scraps in the furnace are red, which takes one and a half hours.

b. Continue to increase the power, so that the charge begins to melt, about 2 hours to make the electric furnace completely melt into the full furnace state, when the temperature reaches 1430℃, the slag in time off. Low power heating up to 1600 ° C (±20 ° C).

C. Heat at 1600℃(±20℃) for 1h.

d, when the hot metal temperature is greater than 1600 ° C, the temperature is generally monitored every 10 minutes.

e, each feeding should be carried out before the last material is completely melted, be careful not to produce shed material phenomenon, continue to feed to the full furnace.

6, the 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 it is strictly prohibited to increase the block material. 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, the normal melting should be the side of the material melting, do not allow the hot metal after clearing and then add material. In particular, the amount of waste iron is too large, resulting in large fluctuations in the liquid level of hot metal, and the hot metal 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 hot metal, immediately put in a number of scraps, so that the furnace lining natural cooling.

    b Empty the hot metal and cool it naturally.

    c Empty and exhaust the hot metal, and quickly cool down 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 GS-01 have cracks due to different expansion coefficients, which need to 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 70㎜, 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 hot metal 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 iron, to avoid large temperature difference between the furnace body and the crucible strain, resulting in cracks.