Aluminiumprofil mit übergroßem Querschnitt – Extrusion 750 mm Breite

An ultra-large section looks like a simple proposition: buy a bigger press and push a bigger shape. In practice, the physics change. At a circumscribed circle above about 500 mm, three things happen at once — the extrusion ratio drops, the quench cannot reach the core, and the die has to distribute metal across a face so wide that flow balance becomes the dominant design problem rather than a detail.

We produce large sections on a 12,000 T line with a circumscribed circle of 600–700 mm class and a cross-sectional width up to about 750 mm, in 6061-T6, 6063-T5, 6005-T6 and 6082-T6. This page is about what changes at that size and where the process stops being reliable.

Pressure is not the constraint. Extrusion ratio is.

Buyers assume a bigger section needs a bigger press, and that a bigger press solves the problem. It does — up to a point. The binding constraint on quality at large size is the extrusion ratio, not the tonnage.

Extrusion ratio is the billet cross-section divided by the profile cross-section. A small section might run at a ratio of 60 to 150: a lot of deformation, a lot of work put into the metal, a fine recrystallised grain structure and good mechanical properties. A large section runs at 8 to 25. There is much less deformation, so the cast structure of the billet is broken up less, the grain stays coarser, and the mechanical properties are lower than the same alloy in a small section.

Extrusionsverhältnis	Profiltyp	Grain structure	Typical effect on properties
60–150	Small to medium profile	Fine, fully recrystallised	Full alloy properties, good toughness
25–60	Medium to large	Mixed, partly worked	Slightly lower elongation, still acceptable
10–25	Large section	Coarse, partly cast structure retained	Lower elongation and toughness; properties become position-dependent
Below 10	Very large or very thick	Largely cast structure	Mechanical properties may not reach the temper minimum; test location matters

The practical consequence is that "6061-T6, yield 240 MPa" is not a single number across all sizes. A 40 mm section and a 700 mm section of the same alloy are not interchangeable at the same temper. If your design allowables come from a handbook and your section is at the large end, ask for properties from a test coupon taken from the actual section, not from the billet.

Quenching a thick wall: the core problem

Quench rate falls off with thickness. The surface of a section can cool at hundreds of degrees per second while the core cools at a fraction of that, and the difference decides whether the core reaches the temper the drawing calls for.

For 6xxx alloys, this shows up as a drop in strength at mid-wall, and it is not visible from outside. A section can pass a surface hardness check and still have an under-tempered core. The larger the wall and the more closed the cavity, the worse it gets, because a closed cavity insulates itself — there is no surface inside for the quench to reach.

Three responses, in order of preference:

1. Design the section so the wall is quenchable. If a 30 mm solid wall is not required for function, a 2 × 12 mm ribbed wall carries similar load with a quenchable thickness. This is a die-stage conversation, and it is the cheapest fix by a wide margin.
2. Change the alloy or temper to match what the section can deliver. 6005A or 6082 in T5/T6 may give a better combination of extrudability and achieved properties than 6061 pushed beyond its quench limit. A slightly lower specified strength that is actually achieved beats a higher one that is not.
3. Accept a machined-from-solid solution. Where the load is genuinely concentrated and the section cannot be quenched, a plate-machined component may be the honest answer, even though it costs more material.

What we will not do is quote a T6 property that the section cannot reach. If the drawing calls for something the quench route cannot deliver, that goes in the quotation as a stated limitation.

Die design at 700 mm: flow balance takes over

A large section needs a large die, and a large die has to deliver metal evenly across a face measured in hundreds of millimetres. The levers are the same as on a small die — porthole layout, welding chamber volume, bearing length — but the sensitivity is much higher.

Porthole layout. Metal enters through ports and has to fill the whole die face before it exits. If the ports are too concentrated in the centre, the outer walls starve and come out thin. If they are too far out, the centre runs slow and the section has a seam down the middle.

Welding chamber volume. The chamber has to be large enough to build the pressure that closes the seam weld, and at large size the chamber is huge, which means the pressure has to be built over a longer flow path. Undersized chamber at large size is the most common cause of a weak seam.

Bearing length. The bearing controls how fast each part of the section exits. On a 700 mm face, a 0.2 mm difference in bearing length between one side and the other can produce a visible curve. Trial correction is iterative, and a large die takes longer to correct because each trial consumes a full billet.

Die strength. A die for a large hollow section is a large steel block with a lot of metal removed. Deflection under load is real, and it transfers directly into wall thickness variation. This is why die life at large size is shorter and why the correction budget is higher.

Spezifikationen

Element	Referenzwert
Extrusionspresse	12,000 T line
Maximum cross-sectional width	about 750 mm class
Maximaler Umkreis	600–700 mm
Maximale Masse pro Meter	up to about 80 kg/m
Tensile strength, reference	≥260 MPa (alloy and section dependent)
Maßtoleranz, kritische Positionen	Reference ±0.02 to ±0.04 mm
CNC-Bearbeitungsgenauigkeit	Reference ±0.005 to ±0.01 mm
Maximale bearbeitete Länge	6,500 mm
Legierungen	6061-T6, 6063-T5, 6005-T6, 6082-T6
Standard	GB/T 6892-2023 Hochpräzision
Oberflächenbehandlung	Anodising, hard anodising, powder coating, electrophoresis
Matrizenlieferzeit	10–15 days to sample for conventional structures
Loslieferzeit	15–20 days after sample approval
Mindestlosgröße	Small batches supported; large sections have a practical minimum per run

Straightness at length: why twist is worse than bow

On a large section, bow and twist behave very differently, and it is worth understanding which one your drawing actually limits.

Bogen is bending in one plane. It can be corrected by stretch straightening, and a large section with adequate wall can be pulled back to a local straightness of a fraction of a millimetre per metre without damage.

Verdrehung is rotation along the axis, and it is harder. Stretch straightening does not remove twist; it can lock it in. Twist comes from asymmetric flow or asymmetric cooling, and once the section is cold the only correction is mechanical twisting, which introduces stress and can open a seam.

So for a large section, the specification should limit twist explicitly and separately from bow, and it should state the measurement length. A 0.2 mm/m local straightness on a 6 m part does not mean 1.2 mm total — it means the local deviation over any one metre, with a separate total allowance for the delivered length. If your drawing only gives the local figure, the total is undefined and will be argued about at goods-in.

A related point on weight. A large section has thermal mass, and it stays hot for a long time after the press. Handling it while it is still cooling, or stacking it before it has stabilised, sets a bow that no straightener will fully remove. This is a plant discipline issue, and it is why two suppliers with the same die and the same press can deliver measurably different straightness.

Where large sections are the right answer

Anwendung	Typical part	What large size buys you
Heavy machinery	Load-bearing beam, equipment base	One-piece forming replaces a welded fabrication; fewer joints, fewer stress risers
Rail vehicle body	Car body structural profile	Fewer longitudinal welds, lower weight, better fatigue behaviour
Large conveyor lines	Main beam, heavy-duty track	Long spans without splicing, higher rigidity per kilo
Energy storage	Large battery rack frame	Integral structure with slots formed in, not welded on
Marine structures	Cabin partition, deck profile	Corrosion resistance plus large stiffened panel in one part
Building envelope	Large-span curtain wall member	Long spans, clean visible surface, fewer joints

The common thread is that large size replaces a weld. That is the real economic argument — not the extrusion cost, but the fabrication cost it removes. A single 700 mm section that replaces four welded plates eliminates three welds, three inspection points, three distortion corrections and the labour to do them.

Wo es nicht passt

• You need a thick solid wall with full T6 properties. The quench cannot reach the core. Redesign as a ribbed section, change temper, or machine from plate.
• Your annual volume is small. A large die is a significant investment and a large press run has a practical minimum. Below a few tonnes a year, the economics do not close.
• The part is short. If the finished part is 800 mm long, you are paying for a 700 mm die and a large run to cut it into short pieces. Machining or a smaller section with a joint may be cheaper.
• You need a tolerance tighter than ±0.02 mm on the as-extruded surface. At this size, machining is not optional for critical features.
• The section has a closed undercut or a very deep narrow cavity. Large dies cannot form features that a small die can; the tooling has to reach further and deflects more.
• You are still changing the design. A large die is the most expensive thing in this process to get wrong. Freeze the interfaces before cutting.

Was für ein Angebot zu senden ist

Send the section drawing with wall thicknesses, the alloy and temper, the delivered length, the mass per metre if you have a target, and the application. Tell us the load case if the part is structural — a large section that carries bending is a different design conversation from one that carries only its own weight. Mark the critical dimensions and the surfaces that must remain visible.

We will reply with the achievable extrusion ratio, the quench route and its limits on your wall thickness, the die layout with the seam position, and a written statement of the tolerances we can confirm. If the section is beyond a reliable process window, we will say so and propose an alternative rather than quote a number we cannot hold.

FAQ

How is a large section different from a normal one?

Three ways. The extrusion ratio is lower, so the grain stays coarser and achieved mechanical properties are below the same alloy in a small section. The quench cannot reach the core of a thick wall, so temper has to be verified mid-wall, not just at the surface. And the die has to distribute metal across a face measured in hundreds of millimetres, which makes flow balance the dominant design problem and lengthens trial correction.

What accuracy is possible at this size?

Reference ±0.02 to ±0.04 mm on critical assembly positions and ±0.005 to ±0.01 mm after CNC finishing, with local straightness around 0.2 mm/m. Those are capability references. The value on your order is set by your drawing, and we confirm in writing what we can hold on each critical dimension before you commit. At this size, critical features should be machined, not left as extruded.

What does the 12,000 T line give me over a smaller press?

It gives you the circumscribed circle and the width — without that tonnage the section simply cannot be pushed. It does not automatically give better properties: a large press running a large section has a low extrusion ratio, which is a materials consequence, not a press consequence. The press opens the size window; it does not close the metallurgy problem.

What are the lead time and the minimum batch?

Reference 10–15 days to first sample for a conventional structure and 15–20 days for the batch after you approve it. Large sections have a practical minimum per run because each run consumes a full billet and the die has to reach thermal equilibrium, so a very small order carries a high cost per kilo. Small batches are quoted; the price will tell you the truth about the economics.

How do you control twist?

By designing flow symmetry into the die and by controlling cooling symmetry, then measuring twist separately from bow on a surface plate. Twist is corrected at the die, not after extrusion — stretch straightening removes bow but does not remove twist. That is why the die review looks at mass distribution before anything else.

Can I get a large section in 7075?

Generally no, and it is better to know why. 7075 has a narrow extrusion window and high flow stress; at large cross-sections the pressure required exceeds what the process can deliver reliably, and the quench sensitivity is worse than 6xxx. If you need high strength at large size, 6082-T6 or 6005A-T6 is the realistic route. If you genuinely need 7075 properties, the part is usually machined from plate.

What surface treatments work at this size?

Anodising, hard anodising, powder coating and electrophoresis are all available, with the caveat that anodising tanks have a length and width limit and very large parts may need to be anodised in a purpose-built line. For visible large sections, seam weld position has to be agreed before anodising, because the seam shows as a colour line.

Senden Sie Ihre Zeichnung

Email the section drawing, the alloy and temper, the length, the mass target and the load case to linjunbing@truetrustlv.com, or send it on WhatsApp at +86 136 6644 0600. You will get an extrusion ratio assessment, a quench limit statement and a written tolerance list before you commit to a die.