equipment electrical principle common sense

Reasons for damage to the induction furnace lining

Time: 2019-08-13

Reasons for damage to the induction furnace lining

The shedding phenomenon is a phenomenon in which the sintered layer lining material suddenly breaks and falls from the furnace wall. The cause is mainly caused by improper furnace or sintering, but sometimes it is caused by improper cold or heat cycle or mechanical stress.

1) The lining loss caused by water vapor often occurs in the lining material with too much water. When the lining is heated too fast, the water vapor generated inside the lining will be pressurized due to nowhere to discharge, and finally the surface of the sintered layer will be broken to cause the lining to fall off. In addition, coil coating or upper coil curing treatment and baking caused by castables may also cause water vapor to enter the furnace lining, causing the hot surface of the lining to burst and fall off. The bursting of the lining will also occur in the special case of leakage of the furnace cooling system. Usually this phenomenon occurs in the sintering phase of the lining. Due to the excessive water content of the lining material (should be controlled below 0.5%), the lining temperature rises too fast in the oven (the recommended heating rate when boric acid is used as the bonding agent is 100 °C/h, and the material using boronic anhydride as the bonding agent) The recommended heating rate is 150 ° C / h), the sintering process is not reasonable and the die has no venting holes. In addition, the dry lining material (still 3% moisture) is not cleaned to form bubbles in the lining.

2) The lining of the lining due to mechanical damage is usually caused by the addition of large blocks to the furnace wall. This phenomenon is particularly likely to occur in the case where the sintered layer is not thick shortly after the lining is sintered.

3) The lining loss due to different expansion ratio occurs when the hot surface of the lining is seriously wetted by molten iron. In the alternating hot and cold cycle, the hot surface lining which is heavily infiltrated by molten iron has a large expansion rate, so that it is infiltrated by molten iron and is not separated by the hot metal infiltration at the junction of the hot surface charge.

4) When the furnace lining is too severely squeezed, the lining will fall off due to extrusion, which often occurs at the bottom of the furnace. When the lining of the lining is uneven or slightly concave, the expansion of the refractory of the furnace bottom causes the compressive stress in the refractory of the furnace to accumulate, and finally causes the lining material to crack or fall off.

5) Although the siliceous dry material has good thermal shock resistance and crack bridging ability, the sharp temperature change still causes the development of the stress in the lining, and finally the lining is detached and must be avoided.

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