Repairing the bottom of induction furnace typically employs the cold patching method. The main steps include inspection, cleaning, material preparation, placing the crucible mold, layered compaction, and sintering by electric heating.
Repair Steps:
Inspection and Decision: Repair should be performed when the furnace wall thickness decreases by 50-60mm compared to the original thickness or when the furnace has been in use for more than 200 heats.
Thorough Cleaning: Clean the furnace thoroughly of residual iron, oxide scale, and slag, ensuring the repair surface is smooth and free of debris.
Material and Mold Preparation: Prepare repair materials such as acidic dry vibrating material, and fabricate a crucible mold using a steel plate (approximately 5mm thick). Its outer diameter should be 50-60mm smaller than the furnace diameter, and its height should extend approximately 100mm beyond the damaged area.
Mold and Filler Placement: Use hoisting equipment to place the crucible mold into the furnace, ensuring it is centered and has uniform gaps around its edges. Then, fill the gap between the mold and the furnace wall with repair material. **Layered Compaction:** After each layer of repair material is filled, it must be compacted and vented using a vibrator or wooden stick. Each layer should be compacted to a thickness of approximately 20-30mm. After compacting one layer and roughening the surface, proceed with the next layer until the repair material height is 10mm higher than the mold.
*Electrical Baking and Sintering: After repair, baking is required. For example, power can be supplied sequentially at 200kW·h, 500kW·h, and 800kW·h for 30 minutes each, raising the molten iron temperature to approximately 1500℃, and then held at that temperature for 1-2 hours.
Key Precautions:
Cleanliness is Crucial: Before repair, slag and residual metal must be thoroughly removed from pits or damaged areas on the furnace bottom; otherwise, the adhesion between the new and old materials will be affected.
Dense Compaction is Essential: During the compaction process, it is crucial to ensure the repair material is dense, especially at the joints near the original furnace lining, to prevent gaps during use. Baking should follow the specified process: The baking (sintering) process should follow the curve or process specified by the equipment, gradually increasing the temperature to form a solid sintered layer.
