Products Description
Square and rectangular tubes are cold-formed (or hot-formed) welded structural hollow sections (SHS / RHS). Their core functions:
a. Load-bearing members - columns, beams, braces and truss members under axial and bending loads
b. Frame construction - main skeletons of equipment frames, racks, scaffolding and conveyor lines
c. Enclosure & protection - guardrails, fences, stair handrails and safety barriers
d. Ducting & protection - sleeves for cables/fire lines, supports for equipment housings
e. Architectural trim - door/window frames, curtain-wall mullions, furniture and display stands
Galvanizing enables these structures to serve long-term in outdoor, humid and salt-spray environments - a "strength + corrosion protection" two-in-one section.
| Square | 10×10mm-600×600mm |
| Length | customizable |
Application
· Building & structure - workshops, warehouses, gymnasiums, mobile houses, scaffolding, curtain-wall and canopy supports
· Municipal & traffic - road guardrails, light poles, traffic sign posts, bus shelters, bridge railings, noise barriers
· Energy - PV mounting frames, substation structures, wind-tower inner members
· Agriculture - greenhouse frames, livestock fencing, irrigation supports
· Industrial - storage racks, conveyor frames, equipment frames, work platforms
· Furniture & decoration - furniture frames, display stands, door/window frames, ceiling channels, outdoor landscape structures
Products Standards
| Market | Standard | Description |
| USA / Canada | ASTM A500 / A500M | Cold-formed welded & seamless carbon steel structural tubing - Gr. A / B / C / D |
| Europe | EN 10219-1/-2 | Cold-formed welded structural hollow sections (SHS / RHS / CHS) |
| Europe (hot-formed) | EN 10219-1/-2 | Hot-formed structural hollow sections |
| Japan | JIS G3466:2021 | Carbon steel square & rectangular tubes for general structure - STKR400 / STKR490 |
| China |
GB/T 6728 GB/T 3091 |
Cold-formed steel hollow sections for structural use Welded steel pipe for low-pressure fluid service (incl. galvanized pipe) |
Galvanizing / coating standards
| Standard | Scope |
| ISO 1461:2022 | Hot-dip galvanized coatings on iron & steel articles - requirements & test methods (≈ GB/T 13912) |
| ASTM A123/A123M | Specification for zinc (hot-dip) coatings on iron & steel products (US market) |
| ASTM A153 | Zinc coating on hardware / fasteners |
| GB/T 13912 | Metallic coatings - hot-dip galvanized coatings on fabricated iron & steel articles (China) |
Material Grades
| System | Standard | Common Grades | Yield Strength MPa | Tensile Strength MPa |
| USA | ASTM A500 | Gr. A / B / C / D | 270 / 315 / 345 / 250 | 310 / 400 / 425 / 400 |
| Europe | EN 10219 | S235JR / S275JR / S355JR | 235 / 275 / 355 | 360–510 / 410–560 / 470–630 |
| Japan | JIS G3466 | STKR400 / STKR490 | ≥245 / ≥325 | ≥400 / ≥490 |
| China | GB/T 1591 | Q235B / Q355B (ex-Q345B) | 235 / 355 | 370–500 / 470–630 |
| Australia | AS/NZS 1163 | C250 / C350 | 250 / 350 | ≥320 / ≥430 |
· Common cross-reference in inquiries: ASTM A500 Gr. B ≈ S355JR ≈ STKR490 ≈ Q355B; Gr. A ≈ S235JR ≈ STKR400 ≈ Q235B.
Surface Treatment
a. Batch Hot-dip Galvanizing (HDG) - the formed & welded tube is immersed in molten zinc (~450 °C), producing a Zn-Fe alloy layer + pure zinc layer on all surfaces. Coating thickness graded by base material thickness: steel ≥6 mm → mean coating ≥85 μm; 3–6 mm → ≥70 μm; 1.5–3 mm → ≥55 μm. b. Pre-galvanized - strip is continuously hot-dip coated before forming/welding; coating typically 20–275 g/m²; uniform and cost-effective, ideal for indoor light structures.
c. Electro-galvanizing - thin coating (approx. 5–15 μm), smooth finish; decorative/indoor/electronic uses.
d. Post-treatment - passivation / chromate (prevents white rust, prolongs storage), oiled finish, optional color painting or Galvalume (Al-Zn) substrate.
End Treatment
· Plain / square cut ends - standard as-delivered condition, square and dimensionally accurate
· Deburred / chamfered - burrs removed to prevent scratching and assembly interference
· Bevelled ends - prepared for butt welding, less field beveling work
· Plastic end caps - protect against dirt ingress and handling damage during shipment/storage
· End sealing paint - prevents moisture entering the bore
Key Advantages
· Corrosion resistance & long life - sacrificial (cathodic) zinc protection with self-healing at scratches; outdoor service life of 20–40 years, 3–5× that of black pipe (which needs periodic painting)
· Full-surface protection - inner & outer walls and corners fully covered, no coating blind spots
· Structural efficiency - closed sections offer high bending/torsional stiffness; higher load capacity per unit weight than angles, channels or solid bars - saves material
· Easy fabrication - weldable, drillable, bolt-connected; fast on-site installation
· Clean appearance - flat surfaces, tight tolerances, neat look for exposed structures
· Economical & green - lowest whole-life-cycle cost; zinc and steel both fully recyclable
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