HG325 Tube Mill Line for Φ165–325 mm Pipe

HG325 is the model step covering Φ165 to 325 mm on our high-frequency welded pipe range. It runs round, square and rectangular section on one line, and it is sized against your pipe rather than sold as a fixed configuration.

Φ165 – Φ325 mmOutside diameter

4.0 – 10.0 mmWall thickness

600 kWHF welder

130×130 – 250×250 mmSquare section

Send EnquiryBack to Large-Diameter Tube Mills

Technical Specification Table

Model step: HG325 Outside diameter: Φ165–325 mm Section shapes: round, square, rectangular Welding process: high-frequency induction welding Forming technology: conventional roll forming, or direct forming square Automation grade: semi-automatic, or full-automatic under PLC control Series wall range: 0.5–16 mm across HG32–HG630 Series welder power:

150–1500 kW, stepped with diameter Material yield: 93% or better by line design

Two of the rows above are worth a sentence, because they are the rows a buyer at this diameter tends to check first. Section shape matters because a plant buying at Φ325 mm is often producing structural section as well as round pipe, and most model steps run all three.

Forming technology matters because it decides what a size change costs, and it is a choice made at quotation rather than a fixed property of the step.

Line Configuration and Scope of Supply

• Coil car and expanding-mandrel uncoiler, tensioning the coil.
• Five-roller leveller, flattening the strip before forming.
• Automatic shear-welder, joining coil to coil.
• Spiral accumulator, buffering strip so forming continues through the join.
• Forming and sizing mill, the core unit for shape, weld position and dimension.
• High-frequency induction welder, sized to the pipe range.
• Flying saw, cutting to length at speed.
• PLC and variable-frequency control, holding speed and repeat cut length.

The process those units perform: rolls form the strip progressively into an open tube; high-frequency current concentrates at the open edges through skin and proximity effect and heats them to welding temperature; squeeze rolls press the edges together to form the seam under pressure; the tube is cooled, sized and straightened.

Because the rating for this step is quoted rather than published, it is worth being concrete about what a sizing actually needs from a buyer. Four inputs settle it: target outside diameter, wall thickness, section shape, and required output.

Diameter and wall come from the finished-pipe specification; section shape matters because round and square are formed differently; and output converts into line speed, which is what turns a heating requirement into a power number.

A published per-step table would be quicker to read and would answer none of those four questions, because welder rating is set by the combination rather than by the diameter alone. That is the practical reason the range is stated and the step value is quoted — not merely the documentary one.

The twelve steps do not tile the diameter axis end to end; they overlap. HG273 covers Φ114–273 mm, HG325 covers Φ165–325 mm, and HG426 covers Φ165–426 mm. A plant whose pipe list runs to 300 mm therefore sits inside two steps at once, and the choice between them is not made by looking up a diameter.

What settles it is the rest of the list: where the smallest pipe in the programme sits, how much of the range will actually be used, and what the output requirement is at each end. A step chosen only against the largest pipe can turn out to be a poor fit for the smallest one, and the smallest pipe is often the one a plant runs most.

We flag the overlap so the question gets asked at enquiry rather than after a line is quoted.

One boundary is worth drawing at this diameter, because both lines exist in our range. An API line-pipe mill is built on the high-frequency mill and adds medium-frequency annealing, straightening, end facing, hydrostatic testing, ultrasonic and eddy-current inspection on top of it, to produce pipe to API 5L.

Its documented model steps are API 219, 406, 426 and 508, covering OD 114–508 mm with wall 6–24 mm by step. needs line pipe rather than general welded pipe is buying a different configuration, and the difference is post-weld heat treatment plus a full inspection chain — not a larger welder.

At this diameter the strip is wide, which makes the upstream step worth naming. Our slitting and cut-to-length line handles strip 1–12 mm thick and 800–2000 mm wide in coils up to 32 t, holding slit width to ±0.2 mm and camber to 0.5 mm per 1000 mm — and camber is the property a forming mill cannot correct once it is there.

The line is the standard eight-unit high-frequency train, sized to this diameter step.

Size Change, Roll Wear and Running Cost

A conventional build changes size by changing rolls; a direct-forming square build adjusts a combined die set by servo instead, with a documented roll saving above 90% because contact is point contact rather than full face. Running cost at this diameter is dominated by tooling and by changeover, as it is across the series. One exception is worth stating: making 100 × 100 mm tube needs the upper roll on the final open stand changed.

Rolls are machined in-house on our own CNC equipment, which is why replacement rolls remain obtainable years after handover.

Changeover behaves differently by forming technology. Operator practice is the third variable: quick changeover and a trained change crew keep scrap during a size change down.

Consumables and wear parts on this line are the standard four groups — saw blades and cutting tools; impeders and induction coils; cooling water, emulsion, hydraulic oil and grease; and forming and sizing rolls as replacement items. tonnage or piece-count figure is stated.

Ten factors decide whether the line holds quality across a run, and they apply at this step as at any other: incoming strip grade, thickness tolerance and flatness; roll material and heat treatment; welding power, frequency and speed; squeeze and seam alignment; sizing and straightening; impeder and coil condition; control and servo stability;

operator setup and changeover; final inspection; and post-weld cooling matched to welding speed.

Forming and sizing rolls determine shape accuracy, roundness and squareness, edge definition and dimensional consistency; roll material and heat treatment decide how long that accuracy holds. When either is wrong, the symptoms are early wear, diameter drift, uneven corner lines and repeated re-machining at every size change.

Applications and Output Examples

At Φ165–325 mm the two application families of the series both apply, and the balance between them shifts with diameter.

Fluid transport pipe — carbon-steel welded pipe for oil and gas transport, municipal water and drainage, gas distribution, and chemical and heating pipework. Weld pass rate, diameter and wall coverage, non-stop coil change, and energy and yield per tonne are what those buyers measure.

Responsibility divides as across the series. The mill controls welding power, seam alignment and squeeze; sizing and straightening set dimensional accuracy and straightness; line design supports material yield above 93%. Incoming strip grade, thickness tolerance and flatness, and day-to-day operation, remain the buyer’s side.

One further point matters at this diameter. Buyers at this diameter often arrive having already decided that they want the largest step they can afford, on the assumption that a wider range is always better.

In practice, each step covers a defined diameter band, and the line is configured against the pipe actually being made. The useful question is therefore not which step is biggest but which step contains the whole of the intended product list with the least unused range.

Structural and scaffolding tube — square, rectangular and round sections for load-bearing steelwork, scaffolding and general machinery components, measured on corner definition and straightness, changeover efficiency and electricity per unit.

Delivery, Installation and Training

Lead time is 50–90 days.

Five operating steps need different levels of training: coil loading and threading, and shear-welding a coil join in time with the accumulator, need operator training; setting a new size needs a trained change crew; setting welder power, welding speed and squeeze and then running the process needs process-level training; cutting and collecting is routine.

After handover, support is a first reply through a single named point of contact, all-hours online support, on-site dispatch when required, and direct spare-part shipment. Behind that sits in-house CNC roll machining, an engineering team of twenty averaging twenty years each, and an owned production base open to factory audit.

Certifications: GB/T 19001-2016 / ISO 9001:2015 (quality management system, certificate No. 18524Q11269R2S); CE for welded pipe equipment, UDEM No. M.2022.206.C72171. The product standard the finished pipe is made to depends on the destination market and the buyer’s specification.

Export packing is specified per item. Control cabinets, impeders and induction coils, forming rolls and cutting tools travel in moisture-protected wooden cases with a spare-parts pack; heavy frames at this diameter ship bare, braced on cradles with designated lifting points and rust protection.

Large diameter tube mill for 325mm pipe

Tube mill for 325mm pipe