As a core piece of equipment in steelmaking, the lifespan of a converter directly impacts production efficiency and costs. Industry data shows that advanced converters in China can last for over 15,000 heats, while some companies, due to poor management, have a lifespan of less than 5,000 heats. Behind this gap lie seven key influencing factors. This article will provide an in-depth analysis from four dimensions: materials, process, operation, and maintenance.
Furnace lining materials: the “genetic code” of refractory bricks
Furnace lining material is the cornerstone of converter lifespan. Traditional magnesia bricks have a lifespan of only 200-300 heats, while modern magnesia-carbon bricks, through their carbon skeleton structure, extend this lifespan to over 2000 heats. European companies use magnesia-carbon bricks with a carbon content of 10%-15%, balancing thermal shock resistance and erosion resistance; domestically, high-carbon bricks with 14%-18% carbon content are commonly used to enhance resistance to molten slag penetration.
A typical case: After a steel plant adopted imported magnesia-carbon bricks, the furnace life jumped from 8,000 heats to 12,000 heats, but the cost per ton of refractory material increased by 12%. This reveals the paradox of balancing lifespan and cost in material selection.
Smelting process: a dual test of temperature and time
Steel tapping temperature control: For every 50°C increase, the furnace life is shortened by 10%. When the temperature exceeds 1650°C, the carbon in the furnace lining material begins to oxidize rapidly, forming honeycomb-like erosion holes.
Smelting time management: For every 10-minute increase in smelting time, the furnace lining erosion rate increases by 3%. A domestic 300-ton converter reduced the average blowing time from 28 minutes to 22 minutes by optimizing the oxygen supply system, thus increasing the furnace life by 15%.
Intermittent operation shock: The thermal stress generated by alternating hot and cold temperatures is the main cause of furnace lining cracks. Experiments show that the furnace lining life is 40% longer during continuous operation than during intermittent operation.
Slag composition: The “invisible killer” of chemical corrosion.
The composition of slag has an exponential effect on the erosion of the furnace lining:
Iron oxide (FeO): For every 1% increase in content, the furnace life decreases by 18-20 cycles. When FeO exceeds 25%, the erosion rate increases exponentially.
Magnesium oxide (MgO) saturation: Maintaining the MgO content in the slag at 10%-12% can form a protective magnesian slag layer. A steel plant increased its furnace life from 6,000 heats to 9,000 heats by adding magnesite to adjust the slag system.
Alkalinity balance: The erosion rate is lowest when the alkalinity (CaO/SiO₂) is controlled between 2.8 and 3.2. Excessive alkalinity will make the slag sticky, which will intensify mechanical erosion.
Loading system: the “first line of defense” against mechanical impact.
Charge control: Overloading the furnace lining will increase the mechanical stress by 30%. One company experienced premature structural spalling of the furnace cap due to long-term overloading by 10%.
Optimized material distribution method: The layered material distribution method of “large blocks in the center and small blocks around the perimeter” can improve the uniformity of furnace lining wear by 25%.
Scrap steel pretreatment: Crushing long strips of scrap steel to below 300mm reduces direct impact on the furnace wall. After implementation, a steel plant saw a 40% reduction in mechanical damage to the furnace lining.
Slag splashing furnace protection: a technological innovation that “multiplies lifespan”.
Final slag adjustment: Control the MgO content of the final slag to 10%-12% and the TFe content to 14%-16%, and the thickness of the splashed slag layer can reach more than 50mm.
Gun position control: The “low-high-low” three-stage gun position operation can increase the splatter coverage of the trunnion from 60% to 90%.
Additive optimization: Adding 3%-5% carbon powder can improve the bonding strength between the slag splash layer and the furnace lining. After implementation, a steel plant extended its furnace life from 8,000 heats to 12,000 heats.
Equipment Maintenance: The “Golden Rule” of Preventive Maintenance
Furnace lining thickness measurement technology: Using a laser thickness gauge, thickness changes can be accurately detected at the 0.1mm level. After establishing a furnace lining thickness database, a certain company can predict replacement locations 30 days in advance, avoiding unplanned furnace shutdowns.
Repair process: Using aluminum-magnesium spray material, it can be directly repaired at a high temperature of 800℃, and the strength recovery rate of the furnace lining after repair reaches 85%.
Steel tapping port management: Adopting a quick-change steel tapping port reduces the replacement time from 4 hours to 1 hour, minimizing heat shutdown losses.
Production rhythm: The “art of balancing” efficiency and lifespan.
Impact of converter reblowing: For every 1 m³/h increase in bottom-blowing argon flow rate, the furnace life is shortened by 3%. A steel plant optimized its gas supply system to control the reblowing intensity at 0.15 m³/(t·min), achieving a win-win situation for both quality and lifespan.
Multi-furnace continuous casting technology: By adopting the “three-furnace continuous casting” mode, the temperature fluctuation range of the furnace lining can be reduced from 300℃ to 150℃, and thermal shock damage can be reduced by 50%.
Intelligent scheduling system: Optimizes production sequences through AI algorithms to avoid frequent start-ups and shutdowns. After implementation, one company saw its furnace life standard deviation decrease from 1200 heats to 400 heats.
