Detailed explanation of the risks and countermeasures for cracks in induction furnace linings

Causes and Solutions for Cracks in induction furnace Linings

During long-term use, induction furnace linings inevitably suffer various forms of damage, with lining erosion and slagging being two common phenomena. This damage not only affects the production efficiency of the induction furnace but also shortens the service life of the lining. To help you better understand the causes of cracks in induction furnace linings and take effective preventative measures, we will explore related issues in depth.

Repair Methods for Lining Cracks

During use, induction furnace linings may develop cracks due to various reasons. These cracks not only affect the furnace's production efficiency but may also lead to more serious safety problems. Therefore, understanding and mastering the repair methods for lining cracks is crucial. Next, we will introduce several commonly used lining crack repair techniques.

1. Generation and Repair of Transverse Cracks

The primary cause of transverse cracks is the failure to loosen the material between the front and rear sections using a degassing fork during lining lining assembly, leading to material delamination. Secondly, if the upper lining cools too quickly during furnace cooling, the large temperature difference between the upper and lower lining causes uneven shrinkage during rapid cooling, resulting in transverse cracks. Furthermore, physical factors causing loosening of the furnace structure can also loosen the mica backing, leading to lining delamination.

Preventing transverse cracks is crucial by maintaining consistent charge weight, ensuring lining density, and using a flat shovel to loosen the surface. During furnace construction, the weight of charge consumed each time should be consistent to ensure uniform lining density and compaction. After each layer is compacted and before adding another layer, the compacted surface should be loosened by about 20mm using a flat shovel to promote proper interlocking between layers. Simultaneously, the charge must be thoroughly mixed before construction to prevent impurities from contaminating it.

2. Longitudinal Cracks

Longitudinal cracks are often caused by improper cold melting leading to unreasonable and rapid thermal cycling, resulting in multiple longitudinal cracks in the lining.

Immediate furnace drying is crucial for forming a thick sintered layer to resist tensile stress during cooling. After the furnace lining is sealed, drying should begin immediately, ensuring continuous melting and holding for the first week or two to allow for the formation of a thick sintered layer, effectively resisting tensile stress caused by cooling contraction.

3. Random Cracks

During charging, excessively large charge blocks can impact the cold furnace lining, causing cracks. Furthermore, instability in the furnace structure and coil displacement during tilting can also cause tensile damage to the lining. Additionally, in 20-ton electric furnaces, melting only half a furnace of molten iron at a time results in a low molten metal level and prolonged molten iron residence time, leading to excessive temperature differences between the top and bottom of the lining and making it prone to random cracks when the furnace cools.

Random cracks can be prevented by maintaining a high molten metal level, controlling the melting rate, and ensuring concentricity between the coil and the crucible mold. A high level of usable molten metal should be maintained to ensure uniform erosion of the furnace wall. Before pouring, short-term stirring at full power is required, and the furnace temperature should be maintained at approximately 1300℃ during normal operation. When melting cold materials, the temperature should be controlled below 1400℃ as much as possible, and a stable melting rate should be maintained. Frequent slag skimming allows the metal to quickly enter the molten flow, thus reducing slag erosion of the furnace lining. Furthermore, ensure the crucible mold is placed concentrically with the induction coil to maintain uniform furnace lining thickness; the error should be controlled within 3mm.

Strategies for Preventing Furnace Lining Cracks

During charging, the size of the charge pieces should be controlled to prevent excessive impact on the cold furnace lining. Simultaneously, the furnace steel structure must be stable to prevent coil displacement and damage to the furnace lining during tilting. In addition, for a 20-ton electric furnace, the molten metal level in the furnace lining should be maintained at a moderate level to avoid excessive temperature differences caused by prolonged residence time of molten iron. During maintenance, a series of operating guidelines should be followed, such as maintaining the required molten metal level, proper stirring, and temperature control, to prevent random cracking.

Silica Ramming Mass

During furnace construction, strict management by designated personnel is essential to ensure consistent lining quality at each stage. Debris must be prevented from falling into the lining during lining to avoid furnace penetration.

Before each charge, the furnace lining must be carefully inspected. Any cracks, perforations, or other potential furnace penetration hazards must be addressed immediately.

If smelting is impossible for an extended period due to equipment malfunction or other reasons, molten iron should be removed from the furnace to prevent slagging.

During smelting, slag should be skimmed promptly to strictly control the formation of a black slagging layer.

Furnaces should be saturated as much as possible to minimize temperature differences between the top and bottom of the lining, thus reducing the tendency to crack.

Charging should be done cautiously, minimizing impacts, and using a frequent, small-batch charging method.

Optimize the furnace lining cold start-up and cooling processes to prevent lining cracks and extend its service life.

Regularly inspect and tighten the furnace's fixing devices to ensure the coils and connections are securely fastened.