Standard Operating Procedure (SOP) for Induction Furnace in Steelmaking

This detailed SOP covers all aspects of induction furnace operations, ensuring efficiency, safety, and consistent steel quality.

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1. Objective

To establish a standard procedure for operating an induction furnace in steelmaking, ensuring safe handling, efficient melting, and quality control.

2. Scope

Applicable to all personnel involved in induction furnace operations in steel plants, covering melting, refining, and tapping.

3. Responsibilities

• Furnace Operator: Conducts furnace charging, melting, and tapping.
• Shift Supervisor: Ensures SOP compliance and troubleshooting.
• Maintenance Team: Handles furnace upkeep, repairs, and safety checks.
• Quality Control (QC) Team: Monitors chemical composition and temperature.

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4. SAFETY PRECAUTIONS

4.1 Personal Protective Equipment (PPE)

• Heat-resistant gloves
• Face shield and safety goggles
• Fire-resistant clothing
• Safety boots with metatarsal protection
• Hearing protection (earplugs)

4.2 General Safety Measures

• Keep a safe distance from molten metal.
• Never add wet or rusted scrap to the furnace.
• Maintain proper ventilation to prevent gas accumulation.
• Ensure all personnel are trained in emergency response.
• Have fire extinguishers, sand buckets, and an emergency shutdown plan ready.

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5. OPERATIONAL PROCEDURE

5.1 Pre-Start Checks

Before operating the furnace, conduct the following checks:

5.1.1 Furnace Equipment Inspection

• Check refractory lining for cracks or wear.
• Inspect induction coil insulation for damage.
• Verify the furnace tilting mechanism (hydraulic/pneumatic).
• Ensure proper functioning of control panels and safety interlocks.

5.1.2 Cooling Water System Inspection

• Confirm adequate water flow rate (25-30 l/min per circuit).
• Check inlet temperature (30-35°C) and outlet temperature (< 55°C).
• Inspect cooling pipes and coil jackets for leaks.

5.1.3 Raw Material Preparation

• Ensure scrap steel is clean, dry, and free from coatings, oil, or rust.
• Preheat scrap if necessary to eliminate moisture.
• Sort materials based on chemical composition.

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5.2 Furnace Startup Procedure

1. Power On:

• Start main control panel and cooling water system.
• Check capacitor banks and power transformers.

1. Initial Charging:

• Add a small amount of scrap at low power (~40%) to form a melt pool.
• Gradually increase power and continue adding scrap uniformly.

1. Full-Power Melting:

• Increase power to 100% once a liquid bath is formed.
• Maintain a uniform temperature distribution by proper stirring (induced by electromagnetic forces).
• Monitor power input (kW), frequency (Hz), and melting time.

1. Temperature Monitoring:

• Use an optical pyrometer or thermocouple to check metal temperature:
  • Carbon Steel: 1,550–1,600°C
  • Alloy Steel: 1,600–1,650°C

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5.3 Refining & Alloying Process

1. Slag Removal:

• Skim off non-metallic impurities and oxidation slag.

1. Deoxidation:

• Add ferroalloys (FeSi, FeMn, FeCr, FeMo) as required.
• Use aluminum or silicon for oxygen removal.

1. Final Composition Adjustment:

• Conduct a spectrographic chemical analysis.
• Adjust alloy composition based on QC recommendations.

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5.4 Tapping the Molten Steel

5.4.1 Preparation for Tapping

• Preheat the ladle to ~800-1,000°C.
• Check refractory condition in the ladle.
• Apply coating on ladle walls to reduce steel contamination.

5.4.2 Pouring Process

1. Tilt the furnace slowly and smoothly to avoid splashing.
2. Control pouring rate to minimize turbulence.
3. Add final alloying agents in the ladle if required.
4. Conduct final chemical analysis before moving the ladle to the next stage (casting, refining, etc.).

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5.5 Furnace Shutdown Procedure

1. Reduce Power Gradually:

• Avoid sudden power cuts to prevent damage.

1. Keep Water Cooling System On:

• Run cooling water for at least 15-30 minutes after shutdown.

1. Slag & Dross Removal:

• Remove remaining slag to prevent hardening inside the furnace.

1. Inspect and Maintain Refractory Lining:

• Perform visual inspection for wear and cracks.

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6. EMERGENCY PROCEDURES

6.1 Power Failure

• Switch to backup generator (if available).
• Reduce furnace power in controlled steps once power is restored.

6.2 Water Leakage in Cooling System

• Immediately shut down power and stop furnace operation.
• Locate and repair leaks before restarting.

6.3 Metal Runout (Breakout)

• Alert all personnel and evacuate immediately.
• Use dry sand or fire extinguishers to control fire.

6.4 Explosion Risk (Wet Scrap Introduction)

• Evacuate area and isolate the furnace.
• Inspect and clean the furnace before restarting.

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7. DOCUMENTATION & REPORTING

Maintaining proper records ensures process efficiency and safety.

• Daily Log Sheet: Records power consumption, melting time, temperature, and production quantity.
• Maintenance Records: Logs of refractory lining condition, coil checks, and cooling system performance.
• QC Reports: Chemical composition and temperature at different melting stages.

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8. TROUBLESHOOTING GUIDE

Issue	Possible Cause	Solution
Slow Melting	Low power input, poor scrap conductivity	Increase power, use conductive scrap
High Power Consumption	Coil insulation failure, slag buildup	Check insulation, clean slag
Overheating	Poor water cooling, high power setting	Improve water flow, reduce power
Ladle Leakage	Lining wear, improper coating	Repair or replace ladle lining

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9. CONCLUSION

This detailed SOP ensures safe, efficient, and high-quality steel production in induction furnaces. Proper training, adherence to safety guidelines, and preventive maintenance are critical for optimal performance.

Tags: Meta TechX, Meta TechX Engineers, Steel Industry, Steel making, Steel Melt Shop