Key Takeaways
- Dephosphorization rate improved from <50% to 63.2%—a 13+ percentage point gain
- Less slag smelting ratio increased from 0% to 83.7% (2012–2019)
- Lime consumption per ton of steel reduced from 53.3 kg to 23.2 kg—down 56.5%
- Optimal bath temperature: 1,370–1,420°C for dephosphorization endpoint
- Slag basicity control at 1.3–1.8 with FeO maintained at 18%–28%
- Bottom-blowing holes: 8 minimum, with bottom-blow gas intensity 0.03–0.10 m³·t⁻¹·min⁻¹
- Scrap ratio: 12%–16% of total charge for thermal balance
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Converter Steelmaking Process Parameters
| Parameter | Unit | Value | Notes |
| Bath Temperature (dephosphorization) | °C | 1,370–1,420 | Optimal endpoint |
| Slag Basicity (R) | – | 1.3–1.8 | CaO/SiO₂ ratio |
| FeO in Slag | % | 18–28 | During dephosphorization |
| Bottom-blowing Holes | count | ≥8 | Gas intensity 0.03–0.10 |
1. Overview
Less slag steelmaking is a critical advancement in modern converter steel production. By optimizing smelting parameters, this process significantly reduces lime and other slag-forming material consumption while maintaining effective dephosphorization performance.
Compared with traditional converter steelmaking, less slag steelmaking delivers substantial cost savings, minimizes solid waste disposal, and improves both economic efficiency and environmental performance.
Why this matters to steel mill operators: The 56.5% reduction in lime consumption directly translates to lower raw material costs and reduced environmental compliance burden—key competitive advantages in today’s steel market.
2. Key Process Parameters
2.1 Temperature Control
Dephosphorization stage bath temperature: 1,370–1,420°C
Hot metal charging temperature: 1,200–1,450°C
2.2 Slag Composition Control
Slag basicity (R): 1.3–1.8
FeO content in slag: 18%–28%
2.3 Blowing System
Oxygen blowing volume during dephosphorization: 24%–28% of total oxygen flow
Scrap ratio: 12%–16%
Number of bottom-blowing holes: 8 or more
3. Performance Results
Industrial practice at a 250-ton converter has demonstrated the following improvements after process optimization:
4. Key Takeaways
Dephosphorization rate improved from <50% to 63.2%—a 13+ percentage point gain
Less slag smelting ratio increased from 0% to 83.7% (2012–2019)
Lime consumption per ton of steel reduced from 53.3 kg to 23.2 kg—down 56.5%
Optimal bath temperature: 1,370–1,420°C for dephosphorization endpoint
Slag basicity control at 1.3–1.8 with FeO maintained at 18%–28%
Bottom-blowing holes: 8 minimum, with bottom-blow gas intensity 0.03–0.10 m³·t⁻¹·min⁻¹
Scrap ratio: 12%–16% of total charge for thermal balance
5. Operational Guidelines
5.1 Pre-Smelting Preparation
Hot metal composition testing: Confirm C, Si, Mn, P, and S content before charging
Scrap preheating: Prepare scrap according to the required ratio (12%–16%)
Bottom-blow system inspection: Ensure ≥8 bottom-blowing holes with gas intensity 0.03–0.10 m³·t⁻¹·min⁻¹
5.2 Dephosphorization Stage Operation
Temperature control: Maintain moderate heating rate to avoid temperature spikes that reduce dephosphorization efficiency
Slag-forming material addition timing: Adjust lime and ore additions based on slag basicity and FeO content
Oxygen blowing regime: Strictly control oxygen flow and blowing time per process specifications
5.3 Endpoint Control
Endpoint carbon control: Affects manganese recovery from manganese ore reduction
Endpoint temperature: Maintain within 1,370–1,420°C range
Slag-steel separation: Ensure good separation for clean steel tapping
6. Key Slag-Forming Materials
Quality specifications for primary slag materials used in less slag steelmaking:
7. Critical Precautions
Less slag steelmaking has specific requirements for hot metal quality. Process parameters must be adjusted based on incoming hot metal composition.
Bottom-blow performance directly impacts dephosphorization efficiency. Bottom-blowing hole quantity and quality must be guaranteed.
Real-time slag composition monitoring is essential. Adjust slag-forming material additions based on slag condition.
Endpoint control precision is critical. Avoid over-blowing or under-blowing, which compromise steel quality.
8. Technical Advantages
Cost reduction: Lime consumption per ton of steel cut by 56.5%, significantly lowering slag material costs
Environmental compliance: Reduced solid waste volume aligns with green steel development requirements
Efficiency gains: Dephosphorization rate improved from <50% to 63.2%
Process stability: Less slag smelting ratio can reach 83.7%, demonstrating reliable process performance
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Frequently Asked Questions
Common questions about converter steelmaking techniques and process optimization.
Q1. What is less slag steelmaking in a converter?
A: Less slag steelmaking is a process optimization technique that reduces lime and slag-forming material consumption by 56.5% while maintaining or improving dephosphorization efficiency. The key is precise control of slag basicity (1.3–1.8), FeO content (18%–28%), and bath temperature (1,370–1,420°C).
Q2. What is the optimal dephosphorization temperature in converter steelmaking?
A: The optimal bath temperature at the dephosphorization endpoint is 1,370–1,420°C. Temperatures above this range reduce dephosphorization efficiency, while lower temperatures can cause incomplete reactions and poor steel quality.
Q3. How much lime can be saved with less slag steelmaking?
A: Industrial data shows lime consumption per ton of steel can be reduced from 53.3 kg to 23.2 kg—a 56.5% reduction. This translates to significant cost savings and reduced environmental burden for steel mills.
Q4. What controls slag basicity in converter steelmaking?
A: Slag basicity (R = CaO/SiO₂) should be maintained at 1.3–1.8 during the dephosphorization stage. This is achieved by careful control of lime additions and the balance of SiO₂ from hot metal and scrap.
Q5. Why is bottom-blowing important in less slag steelmaking?
A: Bottom-blowing provides intensive stirring that enhances mass transfer between slag and molten steel. With ≥8 bottom-blowing holes and gas intensity of 0.03–0.10 m³·t⁻¹·min⁻¹, dephosphorization efficiency improves from <50% to 63.2%.
Q6. What is the scrap ratio for less slag converter steelmaking?
A: The recommended scrap ratio is 12%–16% of total charge. This provides the correct thermal balance while maintaining good dephosphorization conditions in the 250-ton converter operation.
Q7. How does less slag steelmaking improve environmental performance?
A: By reducing lime consumption by 56.5% and increasing the less slag smelting ratio to 83.7%, the process significantly cuts solid waste generation. This supports steel mills in meeting environmental regulations and achieving green manufacturing goals.
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For more details on global steel industry standards, visit the World Steel Association.
Learn about BOF steelmaking process fundamentals and equipment specifications.
For technical standards on steel industry quality management, refer to ISO standards.
