The furnace bottom is the main working layer of a sintering furnace and must meet strict requirements due to its exposure to high temperatures and heavy loads. Its design and construction are critical to furnace performance and longevity.
Requirements for the Sintering Furnace Bottom
- Load Bearing
- Must withstand dynamic loads during material charging without damage.
- Must endure the static load of all furnace materials without deformation.
- High-Temperature Stability
- Must resist physical and chemical action from molten steel and slag.
- Damage along the molten pool area should be uniform, ensuring proper metallurgical process control.
- Durability
- The lifespan, erosion resistance, and failure characteristics depend on material composition, fabrication quality, and sintering method.
Fabrication Conditions and Methods
- Material Composition
- Pure magnesia (MgO) alone cannot form a solid sintered layer because MgO grains cannot bond into a cohesive structure under furnace conditions.
- To create a durable furnace bottom, low-carbon steel or furnace slag is added to the magnesia.
- The amount depends on the MgO content in the magnesia.
- The addition reduces refractoriness slightly but improves plasticity, preventing cracking during rapid temperature changes.
- Temperature Control
- Older small-scale silicate brick furnaces limited furnace bottom temperatures to ≤1700°C.
- Modern large-scale furnaces require higher temperatures to form a more robust sintered layer, but care must be taken:
- Too high a temperature can melt added slag, causing it to flow to the steel tap and shorten the furnace bottom lifespan.
- Temperature regimes must balance complete sintering and material stability.
- Modern Adjustments
- With the use of basic refractory materials and changes in raw steel composition (e.g., low-silicon, low-manganese pig iron), furnace bottoms face high-silica slag attack.
- New methods, such as iron oxide-based sintering, have been successfully applied, improving furnace bottom strength and lifespan.
- Challenges in Adoption
- Advanced sintering methods are slower to be adopted due to a lack of widely accepted theory on sintered layer formation.
- Different plants have varying practices, leading to inconsistent material ratios and temperature schedules.
Summary
A sintering furnace bottom must combine:
- Mechanical strength for dynamic and static loads
- Thermal and chemical resistance to molten steel and slag
- Proper material composition and controlled sintering temperatures
- Uniform wear characteristics to ensure stable furnace operation
Correct design and fabrication conditions directly affect furnace life and performance.