1. Product Overview
The HG76 ERW tube mill line is a high-frequency electric resistance welded (ERW) pipe production system designed to form and weld steel strip into round tubes with an outer diameter capacity up to 76 mm. The designation "HG76" indicates the maximum tube outer diameter the mill is configured to produce, expressed in millimeters.
ERW (Electric Resistance Welding) is a continuous forming and welding process in which a flat steel strip is progressively shaped into a tubular profile through a series of roll forming stations, then welded along the longitudinal seam using high-frequency electrical current. The resulting weld is achieved without filler material, producing a clean seam suitable for structural and mechanical tube applications.
Yangzhou SINOFORM Machinery Co., Ltd. manufactures ERW tube mill lines including the HG76 series as part of its welded pipe equipment range. The company has been producing tube mill machinery since 2010 and specializes in high-frequency welded pipe equipment, laser welded pipe equipment, and associated rolling mill tooling.
2. Key Technical Parameters
| Parameter |
Typical Specification |
| Maximum Tube Outer Diameter |
76 mm |
| Minimum Tube Outer Diameter |
Varies by configuration (typically 20 to 30 mm for HG76 class) |
| Wall Thickness Range |
0.8 to 3.5 mm (confirmed by order specification) |
| Tube Profile |
Round (square and rectangular with sizing section) |
| Welding Method |
High-frequency electric resistance welding (HF-ERW) |
| Strip Material |
Carbon steel, stainless steel (grade-dependent) |
| Mill Speed |
Varies by tube size and wall thickness; confirmed per order |
| Drive System |
AC variable frequency drive (standard configuration) |
3. Main Components of the HG76 Tube Mill Line
A complete HG76 ERW tube mill line consists of several sequential processing sections, each performing a defined function in the strip-to-tube conversion process:
3.1 Uncoiler
The uncoiler holds and feeds the steel strip coil into the line at a controlled tension. Cantilever or double-head uncoiler configurations are used depending on coil weight and production continuity requirements. Proper strip tension at the uncoiler prevents strip wander and forming defects downstream.
3.2 Accumulator and Strip Joining
A strip accumulator stores a loop of strip material to allow coil changes without stopping the mill. A butt welder or shear-and-weld unit joins the trailing end of one coil to the leading end of the next, maintaining continuous production.
3.3 Roll Forming Section
The roll forming section progressively bends the flat strip into an open tubular profile through a series of forming stands. Each stand applies incremental deformation. The number of forming passes and roll geometry is determined by the strip width, material grade, and target tube diameter. Rolling mill molds for the HG76 line are precision-machined to defined profile tolerances.
3.4 High-Frequency Welding Unit
The HF welding unit applies high-frequency current (typically 200 to 400 kHz) through contact shoes or an induction coil at the tube seam. The current heats the strip edges to forging temperature and the weld squeeze rolls apply pressure to form a solid-state forge weld. Weld quality is dependent on consistent speed, power, and edge preparation.
3.5 Weld Bead Removal
The external weld bead formed by the upset material at the seam is removed by a scarfing tool mounted immediately after the weld box. Internal bead management depends on tube end-use requirements and mill configuration.
3.6 Sizing and Straightening Section
The sizing section reduces the tube to its final outer diameter tolerance and corrects ovality introduced during forming. Straightening rolls ensure the finished tube meets linearity requirements. A square or rectangular profile can be produced by substituting round sizing rolls with profiled sets.
3.7 Cut-Off and Run-Out
A flying cut-off saw or cold saw cuts the continuous tube to defined lengths while the mill runs at production speed. The cut tubes are transferred to a run-out table for collection and bundling.
4. HG76 vs. Other ERW Tube Mill Sizes
| Mill Model |
Max OD |
Typical Wall Thickness |
Typical Application Segment |
| HG32 / HG38 |
32 to 38 mm |
0.5 to 2.0 mm |
Small precision tubes, furniture, bicycle frames |
| HG50 / HG60 |
50 to 60 mm |
0.8 to 3.0 mm |
Mechanical tubing, handrails, light structures |
| HG76 |
76 mm |
0.8 to 3.5 mm |
Structural tubing, scaffolding, automotive, HVAC |
| HG114 / HG127 |
114 to 127 mm |
1.5 to 6.0 mm |
Heavy structural, construction, fluid conveyance |
| HG165 and above |
165 mm and above |
2.0 to 10.0 mm |
Large diameter structural and pipeline applications |
5. Application Scenarios
Tubes produced on the HG76 ERW mill line fall within a size range used across several industries:
- Construction and structural steel: Round, square, and rectangular hollow sections used in building frames, supports, and modular structures.
- Scaffolding systems: Round tubes in the 48.3 mm and 60.3 mm OD range, both within HG76 capacity, are standard scaffold tube dimensions in multiple markets.
- Automotive components: Mechanical tubing for chassis components, seat frames, and exhaust system elements where dimensional consistency and weld integrity are required.
- Furniture manufacturing: Steel tube for chair and table frames, shelving systems, and display fixtures where surface finish and dimensional accuracy are important.
- HVAC and fluid conveyance: Tubes used in ducting, heat exchanger frames, and low-pressure fluid transfer systems.
- Agricultural and industrial equipment: Structural and mechanical tubing incorporated into machinery frames, guards, and handling systems.
6. Frequently Asked Questions (FAQ)
Q: What does the designation HG76 specifically refer to?
A: HG76 denotes the maximum outer diameter capacity of the tube mill line, which is 76 mm. The prefix "HG" is used in the SINOFORM product designation system to identify high-frequency welded pipe mill lines. The numeral indicates the upper limit of the tube OD range the mill is engineered to produce.
Q: Can the HG76 mill produce square and rectangular tubes in addition to round?
A: Yes. With the addition of a sizing section equipped with profiled rolls, the HG76 line can produce square and rectangular hollow sections within the dimensional range corresponding to the strip width and forming capacity of the mill. Profile-specific rolling mill molds are required for each target section size.
Q: What steel grades can be processed on the HG76 ERW tube mill line?
A: The HG76 mill is designed to process carbon steel strip as the primary material. Processing of stainless steel or other alloy grades depends on the specific mill configuration, roll materials, and welding system parameters. Material compatibility should be confirmed with SINOFORM at the specification stage.
Q: What are the rolling mill molds and how are they supplied?
A: Rolling mill molds (also referred to as tooling or roll sets) are the precision-machined roll assemblies mounted at each forming, welding, sizing, and straightening stand. SINOFORM manufactures its own rolling mill molds as part of its product range, allowing tooling to be specified and supplied alongside the mill line or as replacement sets for existing equipment.
Q: What commissioning and technical support does SINOFORM provide with the HG76 mill line?
A: Commissioning scope and technical support terms are agreed at the project stage. SINOFORM has accumulated experience across more than ten years of tube mill manufacturing. Customers should confirm installation supervision, operator training, and after-sales service terms directly with the company prior to order placement.
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