In electric arc furnace (EAF) steelmaking, the furnace door and bottom are among the most vulnerable areas, frequently exposed to thermal shock, chemical erosion, and mechanical wear. As the number of heats increases, these areas often suffer damage that, if not properly repaired in time, can reduce furnace lifespan, increase energy consumption, and affect production safety.
This article introduces common refractory repair methods for both the furnace door and furnace bottom to help operators maintain safe and efficient EAF operations.
Repair Methods for Damaged Furnace Door
When the furnace door is partially damaged, the appropriate repair method should be selected based on the severity and operating conditions. The three main repair approaches are:
1. Hot Repair Using Unshaped Refractory Materials
After tapping, hot repair can be carried out using fast-setting refractory materials such as tar dolomite, tar magnesia, or ramming mix. These materials are applied directly to the damaged area while the furnace is still hot.
During the next melting stage, oxygen blowing should be delayed to allow the repair materials to sinter and bond effectively before resuming normal melting.
2. Spraying Repair with Unshaped Refractory Mix
Using spraying equipment, gunning mix is applied directly to the damaged door area. This method is efficient, minimizes downtime, and is suitable for small to medium-sized damage. It also helps extend the service life of the furnace door.
3. Structural Repair with Shaped Refractories
For more severe damage, shaped refractory bricks are recommended. Common materials include tar dolomite bricks, tar magnesia-carbon bricks, and magnesia-carbon bricks. These offer strong resistance to slag erosion and high thermal stability, ensuring the long-term integrity of the furnace door.
Repair Methods for Electric Arc Furnace Bottom
The furnace bottom is subject to erosion from molten steel, slag, and frequent charging, which may cause spalling, cracks, or collapse. Proper repair helps maintain furnace stability and reduces the risk of steel leakage. Repairs are typically done after tapping and include the following steps:
1. Complete Removal of Slag
Before any repair, all residual slag inside the furnace must be removed, including oxidizing slag from the refining phase. If slag cannot be fully tapped at once, it should be transferred into a dedicated slag ladle to ensure a clean working surface.
2. Adjustment of Tapping Conditions
To facilitate slag removal and furnace bottom exposure:
- Minimize scrap charging before the repair heat, and avoid adding dolomite;
- Raise tapping temperature by 30–70°C above normal to enhance slag fluidity;
- Ensure electrode connection is intact; extend electrodes if needed for holding or hot slag conditioning during waiting periods.
3. Application of Ramming Mix
Use furnace bottom ramming mix to fill damaged areas. Hoist the material into the furnace, distribute it evenly to the repair zone, and tamp it flat using tools.
4. Preheating and Residual Steel Removal
After repairing, follow the startup procedure used for the first heat in a new furnace to ensure proper sintering. If any molten steel remains, it can be absorbed using a steel billet to clean the surface thoroughly.
