500kW IGBT Medium Frequency Weld Seam Annealing Machine for ERW Tube Mills

Online Weld Seam Heat Treatment System for High-Quality Steel Pipe Production

AIS MACHINERY provides 500kW IGBT Medium Frequency Weld Seam Annealing Machines designed for online heat treatment of longitudinal weld seams in ERW steel pipe production lines.

Using advanced IGBT series-resonant inverter technology, the system delivers stable medium-frequency heating power for continuous weld seam annealing. It is suitable for carbon steel and common API pipe production, covering pipe diameters from 50mm to 127mm and wall thicknesses from 1.5mm to 7.5mm.

The system is designed to heat the welded seam and its surrounding heat-affected zone to the required temperature, helping improve weld seam microstructure, reduce hardness differences and achieve more consistent pipe quality.

AIS offers a two-unit configuration with two independent 500kW heating power supplies. Operators can select one or both units according to pipe specifications, production speed and heat-treatment requirements.

Key Specifications:

• Rated heating power: 500kW × 2 units

• Total installed power: 1,000kW

• Pipe diameter: 50–127mm

• Pipe wall thickness: 1.5–7.5mm

• Target heating temperature: 830–920°C

• Maximum annealing line speed: 30m/min

• Heating seam width: ≥25.4mm

• Power supply: 480V / 60Hz / Three-phase

• Inverter technology: IGBT series resonance

• Operating frequency: 1–2kHz

1. What Is an IGBT Medium Frequency Weld Seam Annealing Machine?

An IGBT Medium Frequency Weld Seam Annealing Machine is an online induction heating system installed downstream of the welding section of an ERW tube mill.

During ERW pipe production, the steel strip is formed into a tubular shape and welded longitudinally through high-frequency resistance welding. The welding process creates a heat-affected zone around the weld seam, where the microstructure and mechanical properties may differ from those of the parent material.

The seam annealing machine uses electromagnetic induction to heat the weld seam and adjacent areas to a controlled temperature. This heat treatment helps refine the weld seam microstructure, reduce excessive hardness and improve the consistency of the finished steel pipe.

Unlike batch heat treatment, online seam annealing is integrated into the continuous tube manufacturing process. Steel pipes can be heat-treated while moving along the production line, without requiring a separate batch furnace.

The system is particularly suitable for ERW carbon steel pipes, structural tubes and API pipe manufacturing applications where consistent weld seam quality is important.

2. Main Advantages of AIS IGBT Medium Frequency Seam Annealing System

2.1 Advanced IGBT Series-Resonant Inverter Technology

The heating power supply adopts three-phase full-wave rectification and IGBT series-resonant inverter technology.

This configuration offers:

• Stable medium-frequency heating output

• High power conversion efficiency

• Reliable electrical performance

• Convenient maintenance

• Flexible power adjustment according to production requirements

A specially designed matching transformer is used to optimize the coupling between the primary and secondary windings, improving energy transfer efficiency within the resonant circuit.

2.2 Two Independent 500kW Heating Units

The system consists of two independent 500kW heating power units, providing a total installed heating capacity of 1,000kW.

The operator can select the appropriate power configuration according to pipe diameter, wall thickness and production speed.

Available operating modes:

• Single-unit operation: 500kW

• Dual-unit operation: 1,000kW

This flexible configuration helps match heating power to different production requirements.

2.3 Accurate Weld Seam Heating and Temperature Control

The system uses a flat-type induction coil specifically designed for longitudinal weld seam heating.

The heating width is at least 25.4mm, covering the weld seam and its surrounding heat-affected zone.

An infrared temperature measurement instrument monitors the weld seam temperature. The temperature signal is transmitted to the PLC for monitoring and optional closed-loop power adjustment.

In automatic mode, the system can adjust heating power according to temperature feedback to help maintain the required process temperature.

2.4 Online Weld Seam Tracking

The mechanical adjustment system allows operators to adjust the induction coil position while the steel pipe is running.

The induction coil can be adjusted vertically and angularly to maintain proper alignment with the weld seam.

This design helps compensate for weld seam position deviations during production without stopping the tube mill line.

2.5 Automatic Lifting and Burr Avoidance

The mechanical system provides an automatic lifting function to move the induction coil away from the pipe when the production line stops.

An optional burr detection and avoidance mechanism can be installed in front of the induction coil.

When an abnormal burr is detected, the mechanism raises the induction coil to help prevent mechanical damage. After the burr passes, the coil can be returned to its working position.

This function requires the corresponding automatic detection and control equipment.

2.6 Intelligent PLC Control and Production Data Management

The central operator station uses a Siemens S7-series PLC and a 10-inch color touchscreen.

The system provides:

• Centralized control of the heating power supplies

• Real-time temperature and operating-status monitoring

• Manual and automatic temperature control modes

• Production recipe storage

• Historical production data recording

• Fault alarms and diagnostic information

• Remote operation and power adjustment

• Ethernet communication

• USB data backup

Up to 1,000 sets of process recipes can be stored according to material grade, pipe diameter, wall thickness, production speed and heating requirements.

The interface supports Chinese, English and Russian. Button labels can be customized according to customer requirements.

3. Technical Specifications of 500kW IGBT Seam Annealing Machine

Note: Actual heating power and achievable production speed depend on pipe material, wall thickness, initial weld seam temperature, target temperature, heating width and induction coil positioning. Final process parameters should be confirmed through technical evaluation and heating tests.

4. Main Components of the Online Weld Seam Annealing System

The complete system consists of the following major components.

4.1 IGBT Medium Frequency Heating Power Supply

The main power supply generates the medium-frequency electrical energy required for online weld seam heat treatment.

Main features:

• Three-phase full-wave rectification

• IGBT inverter technology

• Series-resonant circuit

• Digital power control

• LCD operating display

• Electrical and water-system protection

The power supply is designed for continuous operation in an industrial production environment.

4.2 Resonant Circuit Cabinet / Capacitor Cabinet

The resonant cabinet contains the resonant capacitors and impedance-matching transformer.

Together with the induction coil, these components form the resonant heating circuit.

The cabinet is installed on an adjustable mechanical positioning system to facilitate installation, adjustment and maintenance.

4.3 Flexible Medium-Frequency Cables

Flexible medium-frequency cables connect the main heating power supply to the resonant cabinet.

They provide the electrical connection required to transfer medium-frequency heating energy between the two units.

4.4 Flat-Type Induction Heating Coil

The induction coil is manufactured using oxygen-free copper tubing and is designed specifically for online ERW weld seam heating.

Key features include:

• Flat-type heating structure

• Heating width of at least 25.4mm

• Magnetic flux-concentrating material

• Water-cooled construction

• Adjustable guide and clamping rollers

• Optimized coil length of approximately 1.7m

Imported ultra-thin silicon steel sheets are used as the magnetic flux concentrator to reduce magnetic losses and improve heating efficiency.

The branch-return type flat induction coil is adopted based on the supplier's heating test experience.

The coil design aims to achieve more uniform temperature distribution across the weld seam while maintaining efficient energy transfer.

4.5 Mechanical Adjustment and Weld Seam Tracking System

The mechanical adjustment system is installed alongside the ERW tube mill production line.

It supports the resonant cabinet and induction coil and allows operators to adjust the coil position according to different pipe specifications.

The system includes:

Motorized Online / Offline Positioning

The mechanism moves the equipment between online and offline positions. During continuous carbon steel pipe production, the equipment is positioned in the working position.

Vertical Height Adjustment

The induction coil can be raised or lowered by a motorized adjustment mechanism to achieve the required gap between the coil and the steel pipe.

Angular Adjustment

An arc-shaped guide rail allows the induction coil to rotate around the center of the pipe.

Operators can make fine adjustments to follow the actual weld seam position while the pipe is running.

Automatic Lifting

When the production line stops, the mechanism can automatically lift the induction coil away from the pipe.

4.6 Burr Detection and Coil Protection Mechanism

An optional burr detection device can be installed ahead of the induction coil.

If a defective weld seam or abnormal burr is detected, the mechanism can raise the induction coil to reduce the risk of coil damage.

A position detection switch monitors the coil's return to its working position.

4.7 Central Operator Station

The central operator station is designed for convenient operation and monitoring of the complete annealing system.

Main configuration:

• Siemens S7-series PLC

• 10-inch color touchscreen

• Industrial PC for data acquisition

• Ethernet communication

• Recipe and parameter storage

• Temperature monitoring

• Production data recording

• Three-color alarm tower

• USB data backup interface

The system can store up to 1,000 sets of process parameters and automatically record important production information such as heating temperature, line speed and operating status.

4.8 Infrared Temperature Measurement System

The system uses an Inosun series infrared temperature measurement instrument to monitor weld seam temperature.

The instrument provides real-time temperature feedback to the PLC.

Main technical specifications:

The temperature measurement system can be integrated with the PLC to support automatic temperature closed-loop control.

4.9 Water Cooling System

The cooling system is designed to remove heat from the power supply, resonant capacitors, matching transformer and induction coil.

A closed-loop soft-water circulation system with a water-to-water heat exchanger is used to help prevent scale formation and reduce the risk of water circuit blockage.

Main cooling system components include:

• Water tank

• Plate heat exchanger

• Circulating water pump

• Filters

• Adjustment valves

• Pressure and temperature instruments

• Piping and accessories

Main operating requirements:

The external cooling water supply and required cooling capacity must be provided according to the equipment cooling requirements.

4.10 Electrical Control Cabinet

The control cabinet manages the mechanical adjustment functions of the flat-type induction heating system.

A one-to-one control configuration is adopted to simplify equipment operation, maintenance and troubleshooting.

5. Main Electrical Components

Component brands and specifications are subject to the final approved technical configuration.

6. Applications in ERW Tube Mill Production

The IGBT medium frequency weld seam annealing machine is designed for online heat treatment in longitudinally welded steel pipe manufacturing.

Typical applications include:

• ERW carbon steel tube production

• API steel pipe manufacturing

• Structural steel tube production

• Mechanical steel tubing

• Industrial welded pipe production

For manufacturers producing different pipe diameters and wall thicknesses, the two-unit 500kW configuration provides flexibility in selecting the required heating power.

The system can be integrated into an existing ERW tube mill line or included as part of a new tube production line, subject to production layout and technical compatibility.

7. How to Select the Right Weld Seam Annealing Machine

Selecting the correct annealing power supply requires more than considering the maximum pipe diameter.

The following factors should be evaluated:

1. Pipe Diameter and Wall Thickness

Larger pipe diameters and thicker walls generally require greater heating power.

2. Production Line Speed

Higher production speeds require sufficient heating power to achieve the target temperature within the available heating time.

3. Initial Weld Seam Temperature

The temperature of the weld seam entering the annealing section directly affects the additional energy required.

4. Target Annealing Temperature

Different steel grades and heat-treatment processes may require different temperature settings.

5. Heating Width

The heating zone must cover the weld seam and the required surrounding heat-affected zone.

6. Induction Coil Design and Position

The coil structure, distance from the pipe and alignment with the weld seam all affect heating efficiency and temperature uniformity.

AIS MACHINERY can evaluate the required configuration based on your pipe specifications, steel grade, production speed and heat-treatment objectives.

8. Frequently Asked Questions (FAQ)

Q1: What is the difference between high-frequency and medium-frequency seam annealing?

High-frequency and medium-frequency induction heating systems operate at different frequencies and have different electromagnetic heating characteristics.

The appropriate frequency depends on the pipe specifications, heating requirements, induction coil design and production process.

Medium-frequency systems are used for online weld seam heat treatment where the required heating depth and temperature distribution must be considered.

Q2: Can this machine be used with an existing ERW tube mill?

Yes. The system can be designed for integration with an existing ERW tube mill.

Before installation, the production line layout, pipe specifications, line speed, electrical supply, cooling conditions and available installation space should be evaluated.

Q3: Can the machine operate with only one 500kW power supply?

Yes. The system has two independent 500kW heating units.

Operators can use one 500kW unit or two units operating simultaneously, depending on the required heating power and production conditions.

Q4: What is the maximum production speed?

The specified maximum annealing line speed is 30m/min.

The actual achievable speed depends on pipe diameter, wall thickness, material grade, initial temperature and target annealing temperature.

Q5: What temperature can the machine achieve?

The specified target heating temperature for this application is 830–920°C.

The final temperature should be determined according to the steel grade and required heat-treatment process.

Q6: How is the weld seam temperature controlled?

An infrared temperature measurement instrument monitors the weld seam temperature and sends the signal to the PLC.

In automatic closed-loop mode, the system adjusts the heating power according to the temperature feedback to help maintain the required temperature.

Q7: Can the induction coil follow the weld seam automatically?

The mechanical adjustment system allows vertical and angular adjustment of the induction coil.

Operators can adjust the coil position while the pipe is running, helping maintain alignment with the weld seam without stopping production.

Q8: Does the machine require a separate cooling system?

Yes. The equipment requires a suitable cooling water arrangement.

A water-to-water heat exchanger and closed-loop soft-water circulation system can be used to cool the heating power supply, resonant cabinet and induction coil. The external cooling water source must meet the equipment's specified flow, temperature and heat-removal requirements.

Q9: Can the machine record production data?

Yes. The operator station can record important operating parameters, including temperature, line speed and power-related information.

Up to 1,000 process recipes can be stored, and production data can be backed up through a USB interface.

Q10: Can AIS customize the annealing system for different pipe sizes?

Yes. AIS MACHINERY can evaluate the required power supply, induction coil, mechanical adjustment system and control configuration according to the customer's pipe specifications and production requirements.

9. Why Choose AIS MACHINERY?

AIS MACHINERY specializes in supplying ERW tube mills, slitting lines, roll forming machines and related steel pipe production equipment.

We understand that stable production, consistent product quality and reliable equipment operation are essential for steel pipe manufacturers.

When working with AIS, customers benefit from:

• Equipment solutions based on actual production requirements

• Practical technical support during equipment selection

• Customized mechanical and electrical configurations

• Siemens and Schneider electrical component options

• Factory testing and inspection

• Photos and videos before shipment

• Remote technical assistance

• Installation and commissioning support according to project requirements

Our goal is not simply to supply a heating machine, but to provide a practical solution that integrates with your complete ERW tube mill production process.

10. Contact AIS MACHINERY for a Customized Weld Seam Annealing Solution

Are you looking for a reliable IGBT medium frequency weld seam annealing machine for your ERW tube mill?

Contact AIS MACHINERY to discuss your production requirements.

To help us recommend the right configuration, please provide:

• Pipe diameter range

• Pipe wall thickness

• Steel grade

• Existing or planned production line speed

• Required annealing temperature

• Existing ERW tube mill specifications

Our technical team will evaluate your requirements and provide a suitable equipment configuration.

AIS MACHINERY — Assistance · Integrated Solutions · Support

Website: www.aistubemill.com
Website: www.aismachinery.com