Description
Factory-Direct ERW Square Tubes — Every ASTM A500 welded square steel tube rolls off our dedicated lines in Jinan, verified by in-house physical and chemical testing before shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square |
| Size Range | 19mm × 19mm – 800mm × 800mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | ERW (Welded) |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Curtain wall / Support tubes / Building structures |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Structural frames for industrial plants, pipe rack supports, equipment platforms |
| Construction Companies | Curtain wall mullions, building column sections, scaffolding uprights |
| Machinery Manufacturers | Conveyor frames, equipment bases, hoisting structure members |
| Infrastructure Developers | Sound barrier posts, signage gantries, solar mounting structures |
What Negative Tolerance Costs When the Inspector Arrives on Site
A 0.3mm wall shortfall on a 6mm spec turns a routine delivery into an air-freight replacement order.
Early in my career I watched a Dubai contractor’s third-party inspector reject an entire container of 30×30×2.5 square tubes because wall thickness drifted past −0.2mm. We air-freighted replacements at our cost. That single incident shaped how every ASTM A500 welded square steel tube leaving Jinan today passes through our own physical and chemical lab — not a borrowed report from a trading desk. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
How ERW Welded Square Tubes Fit Structural and Curtain-Wall Frameworks
An ASTM A500 welded square steel tube in S355 or Gr.B carries compressive and bending loads in portal frames, mezzanine decks, and curtain-wall mullion systems where flat bearing surfaces matter more than circular profiles can offer. The ERW seam runs along one face, allowing predictable load orientation when the engineer specifies weld direction. Our dedicated ERW lines hold ±1% tolerance across the 19×19 to 800×800mm range, so site crews receive consistent fit-up without on-site shimming.
Structural Codes, Surface Environments, and Certification Pathways
Load-bearing frames designed to EN 1993 or AISC 360 require traceable mill certificates tying each bundle to its heat number — a gap that stalls customs clearance in Rotterdam or Jebel Ali. [NEED_CITE: EN 10204 3.1 inspection document requirements for structural steel] For coastal or industrial atmospheres, hot-dip galvanized ASTM A500 welded square steel tubes resist corrosion without field painting, while black-painted or bare finishes suit indoor structural work where appearance is secondary. CE marking under EN 10219 opens EU markets; ASTM A500 Gr.B documentation satisfies North American specifiers. Fixed lengths of 5.8m and 12m align with standard container dimensions, reducing on-site cutting waste.
Steel Grade Selection and ERW Process Fundamentals
S235, S275, and S355 represent ascending minimum yield strength tiers in the EN system — choosing S355 over S235 allows thinner walls at equivalent load, cutting weight and transport cost. Gr.B under ASTM A500 serves a similar structural role in North American projects, while STK400 aligns with JIS G3466 for Japanese-spec infrastructure. [NEED_CITE: steel grade equivalence mapping between ASTM A500 and EN 10219] The ERW process forms flat skelp into square profile through progressive roll forming, then fuses the longitudinal seam via high-frequency electric current — producing a continuous weld suitable for structural applications up to moderate wall thickness. Surface treatment choice follows the service environment: galvanized coatings protect outdoor scaffolding and solar mounts; black painting or varnish suits indoor frames where corrosion risk is low. Wall thickness tolerance of ±1% means a specified 10mm wall measures 9.9–10.1mm — tight enough to satisfy structural calculators without triggering third-party rejection.
The Hidden Price of Unverified Mill Certificates and Off-Spec Tolerances
Material certificates forged or borrowed from unrelated heats fail EN 10204 scrutiny at EU ports, triggering container quarantine and demurrage charges that dwarf the original tube price. Undersized walls pass visual inspection but fail ultrasonic thickness gauging during structural acceptance — forcing member replacement after erection begins. [NEED_CITE: consequences of non-compliant structural steel documentation in international construction projects] An ASTM A500 welded square steel tube without proper CE EN 10219 marking cannot legally enter EU construction sites, regardless of actual material quality.
Procurement Confidence Built on Verified Capability
Every ASTM A500 welded square steel tube we ship carries an original mill test certificate generated by our in-house lab — chemical composition, tensile strength, and dimensional checks recorded per heat number. Our 2,800+ specification range covers non-standard sizes that force competitors to quote extended lead times or reject orders outright. CE certification under EN 10219/EN 10210, ISO 9001:2015 registration, and SGS/BV third-party inspection availability remove certification gaps before they become customs delays. Professional loading plans optimize container utilization for 6m and 12m lengths, while door-to-door logistics coordination handles FOB, CIF, and DDP terms across 50+ destination countries.
Documentation & Compliance
- Mill test certificate documenting Gr.B / S235 / S275 / S355 / STK400 chemical composition and mechanical properties per ASTM A500 or EN 10219
- CE certificate under EN 10219 / EN 10210 for welded square steel tubes entering EU construction markets
- ISO 9001:2015 quality management system certificate covering ERW production and inspection processes
- SGS or BV third-party inspection report available upon request for ASTM A500 welded square steel tube shipments
- Full material traceability linking each bundle to heat number, production date, and test results
- Customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- ERW welded square tubes bundled with high-tensile steel strips, separated by timber dunnage to prevent surface damage during ocean transit
- Galvanized ASTM A500 welded square steel tubes wrapped with waterproof paper and edge protectors to preserve zinc coating integrity
- Container loading plans optimized for 5.8m and 12m lengths, maximizing 20ft and 40ft GP utilization for 19×19 through 800×800mm profiles
- Plain ends capped or wrapped per customer specification to prevent deformation during handling and transport
- Heat number and steel grade stenciled on each bundle for site identification and traceability verification
- FOB Jinan/Qingdao, CIF, or DDP terms available with real-time shipment tracking to 50+ countries
Start Your ASTM A500 Welded Square Steel Tube Inquiry
Submit your specification sheet — including side length, wall thickness, steel grade, quantity, and destination port — and receive a detailed quotation with mill test certificate preview within 12 hours. Non-standard sizes outside the 19×19–800×800mm range are available for review with typical MOQ of 5 tons.
Request Quotation & Mill Test Certificate
Email: admin@sdxjysteel.com | WhatsApp: +86 188 5315 7756 | Tel: +86 531 8573 6315
Frequently Asked Questions
Q: How do ASTM A500 Gr.B, S275, and S355 steel grades compare for structural applications?
A: Gr.B under ASTM A500 serves North American structural specifications, while S275 and S355 follow EN 10219 for European projects. S355 offers higher minimum yield strength than S275, allowing thinner wall sections at equivalent load capacity. We supply all three grades on our ERW lines with full mill test certification.
Q: Can you supply non-standard square tube sizes outside the 19×19–800×800mm range?
A: Yes. Our 2,800+ specification range includes custom non-standard sizes beyond standard catalogs. Minimum order quantity for custom profiles is 5 tons. Submit your drawing or dimension sheet for feasibility review and lead time confirmation.
Q: What is the difference between hot-dip galvanized and pre-galvanized surface treatment?
A: Hot-dip galvanizing immerses finished tubes in molten zinc, producing a thicker coating suitable for outdoor and corrosive environments. Pre-galvanized tubes use coated strip before forming, offering lower cost for indoor applications. We supply both options for ASTM A500 welded square steel tubes.
Q: Which certifications are required for square steel tube import into the EU?
A: EU construction projects typically require CE marking under EN 10219 (cold-formed) or EN 10210 (hot-finished), plus mill test certificates per EN 10204 3.1. We provide CE certification, ISO 9001 documentation, and SGS/BV third-party inspection reports for EU-bound shipments.
Q: How do you calculate theoretical weight and what is your tolerance policy?
A: Theoretical weight is calculated from outer dimension, wall thickness, and steel density per standard formulas. Our tolerance policy holds ±1% on wall thickness and outer dimension, verified by in-house lab measurement before shipment. Actual weight may vary slightly within tolerance bounds.
