Extending the service life of medium-frequency lò cảm ứng linings is critical for reducing foundry operating costs and ensuring safety. Achieving this requires full-lifecycle management, from material selection and lining installation to sintering and daily operation.
1. Material Matching and Standardized Installation
- Lựa chọn vật liệu: Select dry ramming mixes strictly based on the chemical properties of the metal being melted. Quartz-based acidic linings are commonly used for cast iron and carbon steel, whereas basic or neutral linings are required for high-alloy steels to prevent severe chemical reactions between slag and the lining.
- Phân bố kích thước hạt: Ensure a balanced ratio of coarse, trung bình, and fine particles in the ramming mix to achieve maximum dry bulk density. Perform thorough magnetic separation and drying before installation.
- Uniform Layered Ramming: When using a pneumatic rammer, ram in alternating layers. Keep layer thickness controlled and thoroughly scarify the interface between layers to prevent delamination, ensuring uniform lining density.
2. Strict Compliance with Baking and Sintering Curves
- Stepped Heating: Sintering is crucial for forming the lining’s “three-tier structure” (lớp thiêu kết, lớp chuyển tiếp, and loose layer). Strictly adhere to the principle of “slow heating and staged holding,” avoiding rushed heating rates.
- Low-Temperature Dehydration: Allow sufficient holding time between 200°C and 400°C to completely evacuate internal moisture, preventing cracks or spalling at higher temperatures.
- High-Temperature Full-Furnace Sintering: In the final sintering stage, hold at high temperature with a full furnace of liquid metal to ensure the dense sintered layer reaches approximately 30% of the total lining thickness.
3. Optimizing Daily Melting Operations
- Standardized Charging to Prevent Impact: Cushion the furnace bottom with small, non-sharp scrap first. Lower heavy scrap gently using cranes rather than dropping it from height to prevent mechanical damage to the lining wall and bottom.
- Avoid Overheating: Strictly control tapping temperatures and avoid prolonged holding at high temperatures. Every 100°C increase in molten metal temperature exponentially accelerates chemical erosion and physical scour.
- Slag Control and Removal: Minimize the use of low-quality charge materials contaminated with excessive sand or rust. Deslag promptly during melting to prevent severe localized erosion along the slag line.
4. Shutdown Management and Daily Maintenance
- Controlled Cooling Rate: Keep the furnace lid closed after shutdown to allow the lining to cool slowly and naturally to room temperature. Avoid rapid forced air or water cooling, which causes through-thickness thermal stress cracks.
- Crack Repair: Inspect lining condition thoroughly before each heat. Coat minor hairline cracks with patching mix when cold; for deep cracks, clean out loose material completely and perform localized ramming repair.
