Direct forming tube mill line 325×12

The HG325×12 is a high-performance tube mill machine for producing ERW (Electric Resistance Welded) steel tubes from Φ168 mm to Φ325 mm OD and 2.0–12.0 mm wall thickness. Built on direct forming technology, it also manufactures square and rectangular hollow sections, giving producers a single, flexible line for a broad product mix. As the flagship direct forming tube mill machine in our range, it combines reliable mechanical design with servo-driven automatic adjustment for economical, high-quality pipe manufacturing.

1. Product Overview of the Tube Mill Machine

The tube mill machine is the core equipment of any ERW steel pipe production line, converting flat steel coil into welded tubes through continuous forming, welding, sizing, and cutting. The HG325×12 is designed for medium-to-large diameter welded pipe production, serving manufacturers who supply tubes to the construction, structural, energy, and water transportation sectors. Its Φ168–Φ325 mm range and up to 12.0 mm wall thickness cover the most commercially demanded sizes in the global welded pipe market.

What sets the HG325×12 apart from conventional roll-forming tube mill machines is its electric non-changing roll technology - also called direct or flexible forming. Instead of replacing the full roller set for every size change, operators adjust roller positions via a servo-driven system, so a single rough forming roller set covers the entire size range. This dramatically cuts roller inventory cost and changeover time, making the tube mill machine economical for high-mix, medium-volume production.

2. Key Features & Technical Advantages

The HG325×12 tube mill machine integrates three core advances - flexible forming, a quick-change roller system, and a servo-and-PLC control system - that together address the most common pain points of tube mill operators: long changeover time, high roller cost, inconsistent weld quality, and dependence on skilled labor.

2.1 Flexible Forming Technology

The rough forming section adopts flexible forming, the defining innovation of the direct forming concept. Adjustable rollers bend the strip through point contact rather than linear contact, which reduces friction, improves surface quality, and lowers the forming load. When switching sizes within the Φ168–Φ325 mm range, operators adjust roller positions instead of replacing rollers, achieving a 100% rough forming roller sharing rate that eliminates the need to purchase and store dozens of roller sets.

2.2 Quick-Change Roller System

The precise forming and sizing sections still require profile-specific rollers for tight tolerances. To minimize downtime, the HG325×12 uses a quick-change structure: horizontal shafts and universal joints disassemble rapidly, and two modular roller systems alternate - one online in production while the other is prepared offline - so roller replacement happens without stopping the line, maximizing overall equipment effectiveness.

2.3 Advanced Servo & PLC Control System

The control system has two layers: a servo-motor adjustment layer for rough forming and a centralized PLC layer for the whole line. After operators input product specifications, the servo system automatically adjusts and records roller positions, lowering the skill requirement and reducing labor. The core PLC controls all drive units and distributed I/O via the control data bus, supporting automatic and manual modes and making the tube mill machine easy to integrate into a smart factory or Industry 4.0 system.

3. Production Process Workflow

Loading → Uncoiling → Flattening → Leveling → Shearing strip head and tail → Aligning and welding → Accumulating → Feeding → Guiding → Rough forming → Precise forming → High frequency welding → Scraping inner and outer burrs → Weld seam flattening → Water cooling → Sizing → Ultrasonic flaw detecting → Rough straightening → Cutting → Conveying → Hydrostatic testing → Stacking → Bundling.

The entry section (loading through accumulating) joins coil into a continuous strip; the forming and welding section (guiding through water cooling) progressively forms the strip into a round shape and welds the edges with the 1000 kW solid-state HF welder; the finishing section (sizing through bundling) brings the tube to final dimensions, verifies quality via ultrasonic and hydrostatic testing, and prepares it for shipment. The centralized PLC monitors every stage for consistent quality.

4. Technical Specifications

The table below summarizes the main technical specifications of the HG325×12 tube mill machine, defining its production capacity, product range, and equipment footprint for facility planning.

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