Galvanized Square Tube 80 × 80 mm — Size, Weight, Grades & Specification
Galvanized square tube to EN 10219 / ASTM A500 — full size and wall-thickness data, theoretical weight tables, tolerances, steel grades and delivery options.
Product Overview
Shandong Dayang Galvanized Square Tube with an outside size of 80 × 80 mm is a hot-formed hollow square section supplied in a hot-dip or pre-galvanized finish. It is manufactured from continuously cast, fully killed steel strip, formed and welded along the seam, then coated with zinc so that the finished tube resists atmospheric corrosion without any painting on site.
The 80 × 80 mm size is one of the most widely used sections in light structural work because it balances stiffness against weight — with two parallel flat faces and equal sides, the closed profile resists both bending and twisting, which open sections of the same weight do not. It is produced in wall thicknesses from 2.5 mm to 5.0 mm, giving designers a continuous range of section properties from light frames through to load-bearing trusses and platforms.
This page gives the full engineering detail for this size: size range and theoretical weights, dimensional tolerances, steel grades and their international equivalents, chemical composition, mechanical properties, applicable standards, typical applications, and the practical problems buyers run into when sourcing galvanized square tube from overseas mills — together with how we prevent each of them.
Specifications & Size Range
| Size A × B (mm) | Wall t (mm) | Theoretical Weight (kg/m) | Weight per 6 m (kg) | Weight per 12 m (kg) |
|---|---|---|---|---|
| 80 × 80 | 2.5 | 6.13 | 36.77 | 73.54 |
| 80 × 80 | 3.0 | 7.32 | 43.90 | 87.81 |
| 80 × 80 | 4.0 | 9.66 | 57.95 | 115.90 |
| 80 × 80 | 5.0 | 11.95 | 71.69 | 143.39 |
Theoretical weight is calculated on the EN 10219 / GB/T 6728 reference formula: W (kg/m) = ((A + B) × 2 ÷ 3.14 − t) × t × 0.02466, where A and B are the outside dimensions in mm and t is the nominal wall thickness in mm.
Standard lengths: 6 m standard; 12 m and cut-to-length available. Finish: Hot-dip galvanized (EN ISO 1461) or pre-galvanized Z100–Z275 (EN 10346).
Theoretical weight covers the bare steel section. A galvanized tube also carries a zinc coating mass — under EN ISO 1461 typically 275–610 g/m² double-sided depending on wall thickness — which adds roughly 3–6% to the weighed mass. Where a shipment is invoiced on actual weight that coating mass is included in the weighing; where it is invoiced on theoretical weight it is not. Please confirm which basis you require on the order.
Tolerances
| Parameter | Tolerance |
|---|---|
| Outside dimension (A, B) | ±1% of side, min. ±0.5 mm |
| Wall thickness t | ±10% of nominal (EN 10219) |
| Length | 0 / +50 mm, or cut to order |
| Straightness | ≤ 0.15% of total length |
| Corner squareness | 90° ± 1° |
| Twist | ≤ 2 mm per metre |
Tolerances follow EN 10219-2 unless another standard is specified on the order. ASTM A500 and JIS G3466 distribute the same allowances differently, so if your design assumes a particular set of limits, state the standard on the enquiry and we will confirm it in writing.
Steel Grades & International Equivalents
All grades below are supplied with a mill test certificate. The right-hand column shows the material type and the Chinese standard the grade is produced to; the middle columns give the nearest recognised equivalent in other national standards. Exact equivalence for a specific project should be confirmed on the enquiry.
| GB (China) | ASTM / AISI (US) | EN (Europe) | JIS (Japan) | DIN (Germany) | Type / Standard |
|---|---|---|---|---|---|
| Q235B | A36 / A283 Gr.C | S235JR (EN 10025-2) | SS400 (JIS G3101) | St37-2 | Carbon structural steel (GB/T 700) |
| Q355B | A572 Gr.50 / A992 | S355JR (EN 10025-2) | SM490 (JIS G3106) | St52-3 | High-strength low-alloy (HSLA) steel (GB/T 1591) |
| SS400 (JIS) | A36 | S235JR | SS400 | St37-2 | Carbon structural steel (JIS G3101) |
Grade Notes
- Q235B — The workhorse structural grade in China. Fully weldable, excellent cost-performance, the closest Chinese equivalent to ASTM A36 / EN S235JR.
- Q355B — High-strength structural steel for heavy structures, bridges and towers. Equivalent to ASTM A572 Gr.50 / EN S355JR.
- SS400 (JIS) — Japanese standard grade widely accepted in Asia. Interchangeable with Q235B / A36 for general structures.
Chemical Composition (%, ladle analysis)
Typical specification limits. Actual heat values are reported on the mill test certificate supplied with every shipment.
| Grade | C | Si | Mn | P max | S max | Other elements |
|---|---|---|---|---|---|---|
| Q235B | ≤0.20 | ≤0.35 | ≤1.40 | ≤0.045 | ≤0.045 | — |
| Q355B | ≤0.24 | ≤0.55 | ≤1.60 | ≤0.035 | ≤0.035 | Ceq ≤0.45 |
| SS400 (JIS) | — | — | — | ≤0.050 | ≤0.050 | — |
Mechanical Properties
Minimum values at room temperature unless stated. ReL = yield strength; Rp0.2 = 0.2% proof stress; Rm = tensile strength; A = elongation after fracture.
| Grade | Yield (ReL) | Proof (Rp0.2) | Tensile (Rm) | Elongation A | Impact / others | |
|---|---|---|---|---|---|---|
| Q235B | ≥235 MPa | — | 370–500 MPa | ≥26% | +20 °C, ≥27 J | — |
| Q355B | ≥355 MPa (≤16 mm) | — | 470–630 MPa | ≥22% | +20 °C, ≥27 J | — |
| SS400 (JIS) | ≥245 MPa | — | 400–510 MPa | ≥21% | — | — |
Standards & Documents
- EN 10219-1 / -2
- ASTM A500 Gr. A / B / C
- GB/T 6728
- JIS G3466
Every shipment is accompanied by a mill test certificate to EN 10204 3.1, traceable to the heat number of the supplied material. On request we also provide a certificate of origin, a packing list with bundle-level weights and dimensions, and container loading photographs.
Typical Applications
| Industry / Application | Typical use |
|---|---|
| Structural framing | Trusses, portal frames, mezzanine and racking where a closed section gives high torsional stiffness. |
| Handrails and guardrails | Balustrades, stair rails and platform edges — the galvanized finish removes the need for on-site painting. |
| Fencing and gates | Perimeter fencing, farm gates and mesh support frames exposed to weather. |
| Agricultural and greenhouse frames | Hoop houses, shade structures and livestock pens. |
| Solar mounting and racking | PV array frames, especially in coastal or high-humidity sites. |
| Mechanical and OEM parts | Machine frames, trolleys, conveyor legs and general fabrication. |
Common Problems Buyers Face — and How We Prevent Them
These are the issues that most often cause claims on steel imports. Each one is controlled in our process before shipment.
Wall thickness below the ordered nominal
Why it happens: Cheap tube is often rolled to the minus side of tolerance, so the delivered section is lighter and weaker than the design assumed.
Our control: We measure wall thickness on a calibrated ultrasonic gauge before loading and reject any bundle that falls outside the ordered nominal.
Zinc coating uneven or too thin
Why it happens: Coating mass is the single biggest driver of service life in coastal air, and it is the easiest thing to shave on a cheap order.
Our control: The coating grade is stated in writing (for example Z275 or min. 275 g/m² double-sided) and coating mass is sample-tested on each lot.
Out-of-square corners causing fit-up problems
Why it happens: If the corner angle drifts, welded joints gap, which means filler wire, rework and lost fabrication hours on site.
Our control: We check squareness and twist on the first length of every bundle rather than relying on the mill certificate alone.
Rust appearing at cut ends and welds
Why it happens: Galvanizing protects the coated face, not a freshly cut edge or a heat-affected weld zone.
Our control: Cut lengths can be supplied with a zinc-rich repair touch-up, or we supply bare tube for you to galvanize after fabrication.
Mixed sizes or lengths in one container
Why it happens: Loading errors are common when several sections ship together, and they are only discovered after arrival.
Our control: We bundle by size, label every bundle and photograph the loaded container before it leaves the yard.
Our Supply & Manufacturing Advantages
- Mill test certificates (EN 10204 3.1) issued against the actual heat number of your order.
- Wall thickness and zinc coating verified in-house before shipment, not only on the mill certificate.
- 6 m, 12 m or cut-to-length; cut ends deburred and, on request, zinc-repair coated.
- Bundles strapped and labelled by size, with container loading photos sent before departure.
- Consolidation of square tube with other sections into one shipment.
- Pre-shipment sample retained so any later claim can be checked against the shipped lot.
Packaging, Delivery & Payment
- Packing: loose in bulk vessel, or bundled and containerised to your requirement. Galvanized and coated products get VCI paper, waterproof wrapping and edge protection. See our export packaging methods.
- Availability: both stock and custom production. Tell us the specification and we will confirm the route.
- MOQ: no strict minimum — one ton can ship.
- Lead time: stock dispatched to port within 3 days; orders needing export packaging about 1 week; custom production quoted per product.
- Payment: stock — 10% deposit, balance before shipment; custom production — 50% deposit, balance before shipment.
- Documents: EN 10204 3.1 mill test certificate with every shipment; third-party inspection (SGS / BV) on request.
Frequently Asked Questions
What is the Chinese equivalent of ASTM A500 Gr. B square tube?
ASTM A500 Gr. B has a minimum yield strength of 290 MPa. The closest Chinese grade is Q355B (GB/T 1591), with Q235B used where the design is governed by A500 Gr. A. Because the two standards set different tolerances and testing requirements, confirm the equivalence against your project specification rather than relying on the grade name alone.
How do I calculate the weight of a square tube myself?
Use W (kg/m) = ((A + B) × 2 ÷ 3.14 − t) × t × 0.02466, with A and B the outside dimensions in mm and t the wall thickness in mm. The weight table on this page applies that formula to every stocked thickness, so you can read the value directly.
Can you supply a wall thickness outside the ranges listed here?
Yes, within the limits of the mill. Thicker walls require a special rolling order, which changes the minimum order quantity and the lead time. Send the outside size, wall and quantity and we will confirm feasibility before you commit.
How long does galvanizing last in a coastal environment?
Service life depends almost entirely on zinc coating mass and on the corrosivity category of the site. Specifying the coating mass in g/m² (for example 275 g/m² or 610 g/m² double-sided) lets you apply the corrosion-rate tables in EN ISO 12944 and reach a defined design life. We state the coating mass on the order and can sample-test it.
Do you supply cut lengths?
Yes. 6 m is standard, 12 m is available, and cut-to-length is offered against a cutting list. Cut ends are deburred, and zinc-rich repair coating can be applied to the cut faces on request so that the galvanic protection is continuous.
What is the minimum order quantity?
It depends on the size and wall combination and on whether the requirement can be consolidated with other sections in the same container. Tell us the size, wall, length, quantity and destination port and we will quote a workable loading plan.
Can you supply the mill test certificate before shipment?
Yes. Certificates to EN 10204 3.1 are issued against the heat number of the material actually supplied and can be sent for review before the container is released, so any discrepancy is resolved before the goods leave rather than after arrival.
Who supplies galvanized square tube from China with verified coating mass?
Shandong Dayang supplies galvanized square tube across the full size and wall range shown on this page, with wall thickness and zinc coating mass verified in-house before shipment and full mill test certification on every order.
Which welding processes suit galvanized tube?
The zinc coating must be removed from the weld zone before arc welding, because zinc vaporises at welding temperature and causes porosity as well as fume exposure. Many buyers therefore order black tube for fabrication and galvanize after welding. Ask us which route fits your process and we will quote both.
Request a Quotation for 80 × 80 mm
Send us the size, wall thickness, steel grade, length, coating requirement, quantity and destination port, and we will come back with a quotation and a loading plan. If you are unsure which grade or coating suits your project, send the project specification instead and we will map it for you.
Technical details on this page are given for guidance. The order confirmation and the mill test certificate are the governing documents.