To meet the process requirements for fast and uniform heating of square bars and billets before forging and rolling, Hebei Yuantuo Electromechanical Equipment Manufacturing Co., Ltd. has developed a non-standard, custom induction heating system dedicated to square bar and square billet heating. The line can be configured according to the user’s size range and process parameters, and is suitable for square bar heating before forging as well as billet heating before rolling.

Because square bars have sharp corners on the cross-section, an improper coil design may easily cause corner overheating and insufficient core temperature. The Yuantuo engineering team has carried out special optimization on the induction coil structure and guiding system, so that the temperature of the square bar remains uniform during high-temperature heating, laying a solid foundation for subsequent forging and rolling quality.

I. Working Principle: Fast Through-Heating by Electromagnetic Induction

The square bar heating system adopts medium-frequency electromagnetic induction heating. The medium-frequency power supply outputs alternating current to a square-shaped (helical) induction coil made of rectangular copper tube, generating an alternating magnetic field inside the coil.

When square bars or billets are placed inside the coil, the alternating magnetic field induces closed-loop currents (eddy currents) inside the workpiece. Due to the inherent resistance of the metal, these eddy currents are converted into Joule heat within the workpiece, causing the temperature of the square bar to rise rapidly. In a short period of time, the bar can be heated to the required forging or rolling temperature, achieving effective through-heating from surface to core.

By optimizing the coil structure and matching of electrical parameters, together with a properly designed guiding system, the equipment effectively reduces the risk of corner overheating and improves overall temperature uniformity.

II. Heating Parameters and Applicable Workpieces

The line can be customized to the user’s process; typical application ranges include:

• Heating materials: 65Mn, B2, B3, U71Mn, GCr15 and other square steels and billets

• Cross-section size: approx. □25×25 to □300×300, with no limit on bar length (continuous feeding)

• Heating temperature: 1150 ± 5 °C (set point and control accuracy can be adjusted according to process requirements)

III. System Composition: Integrated Induction Heating Unit

A complete square bar heating line mainly consists of:

• Loading machine, billet conveyor and intermediate transfer system

• Medium-frequency power supply and induction heating coil

• Temperature measurement and closed-loop control system

• Cooling-water system and water-circuit monitoring unit

• Variable-frequency drive system

• PLC control system and industrial PC monitoring system

All subsystems operate in coordination to form an automated production unit from loading, heating to discharge, and can be connected to the user’s existing forging or rolling line.

IV. Key Auxiliary Systems and Control Solutions

1. Feeding and Drive System
Each roller shaft is driven by an independent motor and reducer. Multiple rollers are grouped into multi-axis drives controlled by a single frequency inverter, ensuring synchronized operation. This design facilitates section-by-section speed control and allows matching heating time and production pace in different process zones.

2. Guiding System
The guiding section uses 304 non-magnetic stainless steel guide rollers. Axial elasticity is reserved on the roller shafts to adapt to the permissible bending of square bars and billets, reducing mechanical interference between the workpiece and the coil and ensuring smooth running.

3. Temperature Closed-Loop Control System
The equipment is equipped with an infrared pyrometer and Siemens S7 PLC to form a temperature closed-loop control system. Based on the billet’s initial temperature and feeding speed when entering the inductor, the system automatically adjusts the medium-frequency power output to keep the discharge temperature within the set range and improve process stability and product consistency.

4. Industrial PC Monitoring and Management System
The industrial PC system displays real-time working status and key process parameters, and provides:

• Storage, recall and printout of workpiece and process parameters

• Fault alarm and fault record

• Automatic power reduction under abnormal conditions with temperature holding

This offers strong data support for on-site operation and later process traceability.

V. Application Advantages: Energy-Saving, Efficient and Environment-Friendly

Compared with traditional flame furnaces, Yuantuo’s square bar induction heating line offers the following advantages:

1. Shorter Heating Time, Better Surface Quality
   Induction heating has a very high heating rate. The residence time of square bars in the furnace is significantly reduced, which helps lower metal loss during heating and improve surface quality during rolling.

2. Less Oxidation and Decarburization, Better Environmental Performance
   There is no open-flame combustion in the heating zone, and almost no flue gas is generated. Surface oxidation and decarburization of the workpiece are greatly reduced, resulting in cleaner surfaces on square bars and billets, which is beneficial to subsequent machining and final properties.

3. Accurate Temperature Control and Energy Saving
   With the closed-loop temperature control system, fast and precise automatic temperature regulation is easily achieved, avoiding overheating and repeated heating that cause energy waste. Overall energy efficiency is significantly better than that of traditional flame furnaces.

4. Lower Maintenance Cost
   The system features a modular, easy-maintenance design. Without complex combustion systems, daily maintenance and operation costs are generally lower than those of flame furnaces.

5. Support for Long Billets and Semi-Endless Rolling
   The line can handle extra-long billets for continuous heating, enabling semi-endless rolling and helping to improve overall rolling efficiency and automation level.

Hebei Yuantuo Electromechanical Equipment Manufacturing Co., Ltd. will continue to focus on heating and heat-treatment requirements for square bars, billets and various long products. We provide customized induction heating solutions for forging plants, rolling mills and other users, including process evaluation, equipment selection, on-site commissioning and training services.

For more detailed information and configurations of square bar induction heating systems, please feel free to contact Hebei Yuantuo and discuss your specific process and capacity requirements.