NEWS & EVENTS
Aogang Machinery Co., Ltd.
Aogang Machinery Co., Ltd.
Sep. 10, 2026
The welding section is a key part of an ERW tube mill. After the steel strip is gradually formed into a tubular shape, its edges are heated and joined by high-frequency welding to create a continuous welded tube.
Stable welding depends on more than the HF welder. The impeder, squeeze rolls, strip edge condition, welding power, production speed and cooling system all affect the welding process and final tube quality.
This guide explains the main components of a tube mill welding section, how HF welding works, and the key factors that influence ERW weld quality.
The welding section is positioned after the forming section of an ERW tube mill. As the formed strip approaches the welding point, its two edges are brought close together.
High-frequency electrical energy heats the edges, and squeeze rolls then apply pressure to join them into a continuous longitudinal weld.
A typical welding section may include:
HF welder
Impeder
Induction coil or contact system
Squeeze rolls
Cooling system
Weld bead removal equipment
Welding parameter monitoring system
The exact configuration depends on the tube diameter, wall thickness, steel grade, production speed and required product quality.
HF welding uses high-frequency electrical energy to heat the edges of the formed steel strip.
The basic process is:
The steel strip passes through the forming section.
Forming rolls gradually shape the strip into a tubular profile.
The two strip edges approach the welding point.
High-frequency current generates heat near the edges.
Squeeze rolls bring the heated edges together under pressure.
The edges are joined to form a continuous weld.
Excess weld bead can be removed according to product requirements.
The welded tube continues to the sizing and finishing sections.
The purpose of HF welding is to concentrate heating around the strip edges rather than heating the entire tube. This allows continuous and efficient tube production at relatively high speeds.
The HF welder supplies the high-frequency electrical energy required to heat the strip edges before they are joined.
The required welding system depends on several production factors, including:
Tube diameter
Wall thickness
Steel grade
Production speed
Material properties
Required output
The HF welder should therefore be matched with the complete Tube Mill Line rather than selected independently.
The impeder is positioned inside the formed tube close to the welding point. It helps influence the high-frequency current path and concentrate electrical energy around the strip edges.
Proper impeder positioning is important for welding efficiency and stability. Its performance can be affected by tube diameter, wall thickness, material, welding conditions and cooling.
Because the impeder operates close to the welding area, adequate cooling is also important for continuous production.
Squeeze rolls apply mechanical pressure to bring the heated strip edges together.
HF energy provides the necessary heating, while the squeeze rolls provide the pressure required to complete the joining process.
The heating and squeeze conditions need to be properly matched. Incorrect settings may result in an unstable weld, excessive weld bead or insufficient joining.
After welding, excess material may form along the weld line. Depending on the tube application and surface requirements, external weld bead removal can be used to achieve the required finish.
The bead removal configuration should be selected according to the final tube specification and downstream processing requirements.
Consistent weld quality requires the electrical, mechanical and material conditions to remain properly matched.
The HF welding power needs to match the material, wall thickness and production speed.
Insufficient energy may result in inadequate heating, while excessive energy can cause overheating and undesirable effects around the weld area.
Production speed affects the time available to heat the strip edges.
When production speed increases, the welding system must provide sufficient energy to maintain suitable heating conditions at the welding point.
Clean and consistent strip edges are important for stable welding.
Surface contamination, edge defects or dimensional variation can affect the welding process. Good incoming material quality helps reduce process variation.
Squeeze rolls must provide suitable pressure to join the heated edges.
The correct pressure depends on the material, wall thickness and welding conditions. Electrical heating and mechanical pressure should be considered together rather than adjusted separately.
The impeder should remain in a suitable position relative to the welding point. Its cooling condition should also be monitored during continuous production.
Improper positioning or insufficient cooling may affect welding stability and component service life.
A weak weld may be related to unsuitable welding power, excessive production speed, poor strip edge condition or insufficient squeeze pressure.
The complete welding process should be checked before changing individual parameters.
Excessive heating may occur when welding conditions are not properly matched with the material, wall thickness or production speed.
It can result in excessive weld bead or undesirable conditions around the weld area.
Welding instability may be caused by fluctuations in welding power, inconsistent strip edges, forming problems, impeder positioning or unsuitable process parameters.
Stable strip feeding and coordinated forming and welding conditions can help reduce these problems.
An excessive weld bead can occur when heating and squeeze conditions are not properly balanced.
Operators should check the welding parameters, forming condition and squeeze roll setup together.
Good weld quality control starts before the strip reaches the welding point.
The incoming strip should meet the required steel grade, thickness, width and surface condition.
Consistent raw material helps maintain stable production conditions.
The forming section should guide the strip smoothly toward the welding point.
Poor forming can change the position and angle of the strip edges, making the welding process less stable.
Welding power, production speed and other relevant process conditions should be monitored during production.
Keeping these parameters within the appropriate operating range helps maintain consistent weld quality.
The HF welding system, impeder, squeeze rolls and cooling system should be checked regularly according to the machine's operating and maintenance procedures.
Early detection of abnormal conditions can help reduce production interruptions.
Depending on the application and applicable standards, finished tubes may require dimensional, surface, mechanical or other quality inspections.
The inspection method should be selected according to the final product requirements.
When selecting an HF welding system, manufacturers should first define the intended production range.
Important information includes:
Tube diameter
Wall thickness
Steel grade
Tube shape
Production speed
Required output
Product application
Applicable standards
The HF welder, impeder and related components should then be matched with the complete tube mill configuration.
A welding system designed for thin-wall, high-speed tube production may differ from one designed for thicker-wall structural tubes. A customized configuration can help ensure that the welding section matches the actual production requirements.
The welding section directly affects the continuity and quality of ERW tube production.
A properly configured welding system can help achieve:
Stable continuous production
Consistent weld quality
Suitable production speeds
Efficient energy use
Reduced production interruptions
Easier process monitoring
Consistent finished tube quality
However, welding performance also depends on forming stability, raw material condition, operating parameters and maintenance.
For this reason, the welding section should be designed as part of an integrated tube mill rather than treated as an independent machine.
The HF welder supplies high-frequency electrical energy to heat the edges of the formed steel strip before they are joined under pressure.
An impeder helps control the high-frequency current path inside the formed tube and concentrates energy around the welding area. Proper positioning and cooling are important for stable operation.
Squeeze rolls apply pressure to bring the heated strip edges together and complete the welding process.
Important factors include welding power, production speed, strip edge condition, forming stability, squeeze pressure, impeder position, cooling and raw material consistency.
The HF welding system should be selected according to tube diameter, wall thickness, steel grade, production speed and overall production requirements.
Yes. The welding section can be configured according to tube specifications, material, wall thickness, production speed and other project requirements.
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