1 Industry Application Background
In short-process continuous casting and rolling, hot charging rolling lines, steel billets lose heat rapidly at edges, corners and head-tail sections after continuous casting cutting and roller conveying, resulting in obvious temperature difference on cross-section and axial direction, which easily causes dimensional fluctuation, surface cracks and uneven metallography during rolling.
Yuantuo IGBT induction heating system for steel billet temperature compensation is installed at the station before rolling mill to precisely compensate temperature for cooled billets, reach standard temperature required by rolling process. It supports online temperature equalization transformation for square and round billets, acting as core supporting equipment for energy saving and quality improvement of metallurgical rolling lines.
2 Core Working Principle
The temperature compensation system operates based on electromagnetic eddy current heating and skin effect, consisting of IGBT medium frequency power supply, segmented induction coils, infrared thermometers and PLC linked conveying racks to form full closed loop:
- IGBT medium frequency power supply converts industrial three-phase power into controllable alternating medium-frequency current, fed into customized multi-section induction coils to generate high-density alternating magnetic field.
- Steel billets with normal or reduced temperature move uniformly through magnetic field. Eddy currents are induced inside metal substrates by cutting magnetic lines, and self-heating occurs via Joule heat from metal resistance to realize uniform heating from inside out.
- Working frequency is matched according to billet cross-section size: low frequency for thick large billets to realize deep through-heating, medium frequency for medium & small billets to balance heating speed.
- Multi-point infrared thermometers collect inlet & outlet temperature of billets in real time, transmit data to PLC console, automatically adjust power output and conveying speed within millisecond level to complete precise compensation, controlling overall billet temperature deviation within ±5℃.
- Coils adopt combined transverse & longitudinal magnetic structure to target low-temperature corners of billets, eliminate temperature gradient on cross-section and head-tail, meeting stable temperature window of rolling mill.
The heating mode is non-contact and flameless, only directional heat transfer to billets without invalid heat loss of furnace body, different from integral heat storage of traditional gas soaking furnaces.
3 Core Advantages vs Traditional Furnace Compensation
1 Precise temperature control to eliminate rolling defects
Traditional gas furnaces heat integrally with slow temperature rise and hard to compensate cold corners. Induction system conducts targeted compensation on low-temperature zones, greatly reduces cross-section & head-tail temperature difference, improves dimensional accuracy and lowers reject rate of cracks & lamination. Closed-loop temperature control accuracy reaches ±5℃ to stably lock rolling temperature range.
2 Energy saving & low operation cost
Energy utilization of induction heating exceeds 70%, while gas furnaces only reach 25%–35%. No continuous heat preservation energy consumption, nearly zero power consumption during standby. Short compensation time shortens high-temperature exposure of billets, oxide scale ≤0.5% to reduce metal burning loss, cutting comprehensive energy & raw material cost per ton billet.
3 Embedded online installation without breaking original rolling rhythm
Modular compact layout occupies far less space than large heating furnaces, can be directly installed on roller table between caster and rolling mill, matching original conveying rhythm. Multi-axis synchronous variable-frequency conveyors transport billets stably, support PLC signal interconnection with rolling mill for full-automatic continuous compensation without extra stacking & transfer, suitable for hot direct rolling short process.
4 High automation to cut labor cost
Built-in database of process parameters for different billet materials & sizes, one-click switching. Full-process data including temperature, power and line speed is stored for traceability, with automatic fault early warning. Only remote monitoring required without on-site temperature adjustment staff.
5 Eco-friendly low pollution for low-carbon metallurgy
No gas combustion, flue gas and noise pollution. IGBT power supply features high power factor and low harmonic, without extra reactive power compensation, meeting steel plant environmental renovation standards.
4 Core Technical Characteristics
- Segmented composite induction coil
Main heating coil + auxiliary corner compensation coil with magnetic yoke for magnetic concentration to solve low-temperature corners of square billets. Independent closed cooling water circuit extends service life under long-term continuous operation. - Full digital self-adaptive IGBT medium frequency power supply
Self-developed Yuantuo IGBT power supply with power range 1000–12000kW, frequency 0.5–10kHz auto tracking resonance. Automatically matches power & frequency under load fluctuation and variable inlet temperature, stable output for mixed production of multi-spec billets. - Multi-point infrared closed-loop temperature regulation
Infrared sensors arranged at inlet, middle and outlet collect full-range temperature signals. PLC dynamically adjusts heating power to avoid over-compensation or insufficient heating without manual intervention. - Synchronous stable conveying system
Non-magnetic stainless steel guide rollers & multi-motor synchronous variable-frequency idlers transport billets without scratch or offset, smoothly passing through coils to prevent surface damage. - Full-process data storage & traceability
Touch HMI displays real-time temperature, power, line speed and alarm curves. Production records auto-saved for export & printing, supporting quality audit and process optimization.
5 Main Application Fields
- Online temperature compensation & equalization for hot direct rolling lines of continuous casting square & round billets;
- Energy-saving transformation of traditional heating furnaces in long & short flow steel plants, replacing secondary gas reheating;
- Pre-rolling temperature compensation for rebar, bar, wire rod and seamless pipe billets;
- Special rolling production lines with strict temperature requirements for alloy & special steel billets;
- Rapid temperature rising for billets cooled during intermittent production & waiting.
6 Daily Maintenance Tips
- Inspect cooling water pressure, flow and leakage of induction coils daily to prevent burnout from overheating;
- Regularly clean dust on power cabinet & coil surface, calibrate infrared thermometer accuracy;
- Check IGBT power modules and transmission parts per maintenance cycle, replace vulnerable parts in advance;
- Analyze historical process data periodically, optimize matching of compensation power & line speed according to finished rolling quality for stable long-term effect.
Website：yuantuoinduction.com
WhatsApp：+86-15226757228
Email：yuantuo38@gmail.com
