The Ladle Refining Furnace (LF Furnace) is a pivotal secondary refining device in the metallurgical industry, primarily used for post-treatment of molten steel (or molten alloys) after primary smelting (e.g., electric arc furnaces, converters). It enables precise control of molten steel temperature, homogenization of chemical composition, deep removal of impurities (S, P, H, O), and accurate alloying—critical for producing high-grade steel and special alloys. The 20-150t specification range covers medium-to-large-scale production needs, from small-batch special steel manufacturing (20-50t) to large-scale industrial steel production (80-150t), widely serving industries such as new energy, automotive, aerospace, and heavy machinery. Below is a detailed breakdown of its core structure, working principle, technical parameters, application scenarios, and operational advantages.
The LF Furnace structure is centered on the ladle as the reaction vessel, integrating heating, stirring, atmosphere control, and auxiliary systems. While the overall design is standardized, key components are scaled and optimized for different tonnages to ensure efficiency and stability.
The LF Furnace’s operation follows a "heating-refining-homogenization" cycle, with 5 key stages (taking a 100t LF Furnace for automotive alloy steel production as an example):
- Ladle Transfer: After primary smelting (e.g., 100t electric arc furnace), molten steel (temperature ~1550°C, S content ~0.02%) is transferred to the LF ladle via a crane.
- Arc Ignition & Temperature Adjustment: Lower the 3 graphite electrodes to 25-50mm above the molten steel surface, apply 15-35kV voltage to ignite the arc. The arc (2500-3000°C) heats the molten steel to the target temperature (1600-1720°C) at a rate of 8-15°C/min (controlled by adjusting electrode current).
- Slag Formation & Impurity Removal: Add slag formers (CaO + CaF₂) to form a high-alkalinity slag (basicity ≥3.0), which reacts with sulfur (S) to form CaS (low solubility in molten steel) that floats to the slag layer. For deep desulfurization, the slag layer is maintained at 50-100mm thick, reducing S content to ≤0.005%.
- Alloying & Homogenization: Add alloying agents (e.g., Cr for stainless steel, Mo for high-strength steel) via the automatic feeder. The bottom-blowing argon system stirs the molten steel (stirring intensity: 0.5-1.0 m/s), ensuring alloy elements dissolve uniformly (composition uniformity error ≤0.05%).
- Final Inspection & Discharge: After holding for 30-60 minutes (depending on tonnage), sample the molten steel for spectral analysis (composition) and thermocouple temperature measurement. If qualified, tilt the ladle to transfer the molten steel to continuous casting equipment (e.g., slab caster) for further processing.
Parameters vary by tonnage to match production scale and product requirements. The table below lists typical specifications for mainstream tonnage segments:
The 20-150t LF Furnace is widely used in high-quality metallurgical production, with tonnage selection tailored to product type and batch size:
Compared with primary smelting equipment (converters, electric arc furnaces) and other secondary refining devices (RH degassers), the 20-150t LF Furnace offers unique advantages:
- Strong Process Flexibility: Supports atmospheric refining, vacuum degassing, and alloying; can be customized for different steel grades (e.g., low-carbon steel, high-alloy steel) without major equipment modifications.
- High Refining Precision: Achieves strict control of temperature (±2-5°C) and composition (uniformity error ≤0.05%), reducing impurities (H ≤2ppm, S ≤0.003%) to meet high-end material standards (e.g., aerospace steel).
- Energy Efficiency & Environmental Friendliness: Compared with re-smelting in electric arc furnaces, LF Furnaces save 30-50% energy; the closed dust removal system ensures dust emission ≤10mg/m³, complying with national environmental protection regulations (e.g., China’s GB 28664-2012).
- Cost-Effectiveness: For medium-to-large batches, the 80-150t LF Furnace enables continuous production, reducing unit energy consumption and labor costs; the 20-50t model is cost-efficient for small-batch special steel, avoiding overcapacity waste.
To ensure long-term stable operation of the 20-150t LF Furnace, regular maintenance and safety measures are critical:
- Refractory Lining: Check the ladle working layer thickness every 5-10 batches; replace magnesia-carbon bricks when thickness is reduced by 50% (to prevent molten steel leakage). For 80-150t models, use ultrasonic thickness meters for non-destructive testing.
- Electrodes: Monitor electrode wear; replace electrodes when length is less than 1/3 of the original (to avoid unstable arc and electrode breakage). Clean electrode holders weekly to remove oxide deposits.
- Water Cooling System: Flush cooling water pipelines every 3 months to remove scale; install flow meters and temperature sensors (trigger emergency shutdown if flow drops by 20% or temperature exceeds 60°C).
- Safety Interlocks: Equip with multiple safety protections:
- Electrode over-lowering protection (stops descending if electrode touches molten steel).
- Ladle tilting overload protection (prevents tilting beyond safe angle).
- Gas leakage alarm (for argon/vacuum systems) with automatic cut-off valves.
Main uses: ladle refining furnace can be used for refining molten steel of primary refining furnace (electric arc furnace, open hearth furnace, converter), which is an important metallurgical equipment to meet continuous casting and continuous rolling.
Application:
Ladle Refining Furnace is used to refining the molten steel from the primary melting furnace (electric arc furnace, induction furnace, converter and etc.), meanwhile have the function of adjusting molten steel temperature, and be a
buffer of the whole process. It is described to be the soul of the best production line ( primary melting furnace + LF+ CCM). It is widely used in the refining of kinds of steel grade, such as Ball bearing steel, alloy structural steel, tool steel, spring steel, carbon steel and etc.
Equipment features: equipment with atmospheric arc heating, vacuum degassing, blowing argon stirring, blowing oxygen feed wire, atmospheric pressure or vacuum feeding, temperature measurement, sampling, TV camera, frequency observation and other functions.
Equipment composition:
1. Ladle and ladle car;
2. Heating device (electrode control mode: manual control or microcomputer automatic control. Energy-saving short mesh and conductive cross arm are used);
3. Vacuum and detection system;
4. Hydraulic and control valve system:
5. Argon, oxygen, compressed air and cooling water systems;
6. Electrical control system (PLC control and CRT image imitation display)
7. High voltage and strong current system;
8. Large current lines.
Specification:
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