Description
Factory-Direct ERW Square Tubes — All ASTM A500 Gr.B and EN S355 welded square steel tubes roll out of our own mill with full chemistry and dimensional logs, cutting out trader markups on every ton.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Welded 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 | Construction structures / Curtain wall framing / Building frames / Support tubes / Fertilizer tubes |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & EPC | Building frames, column bracing, industrial platform supports |
| Facade & Curtain Wall | Mullion framing, architectural square hollow sections for glass curtain walls |
| Infrastructure | Bridge handrails, sound-barrier posts, solar mounting structures |
| Machinery & Equipment | Conveyor frames, equipment bases, fertilizer delivery tubes |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a 30mm wall is the difference between a beam that passes load calculation and one that fails site inspection.
Project engineers specifying ASTM A500 Gr.B welded square steel tubes often discover — after the container arrives — that the wall is running heavy negative tolerance. The mill cert looked perfect, but the caliper tells a different story. On a 20×20×1.5 section, a 0.15mm shortfall may seem trivial on paper; on a 40-meter curtain wall grid, it multiplies into rejected welds, re-cut members, and a customs hold if the CE file does not match the physical product [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements].
Matching the Tube to the Curtain Wall Grid
Facade contractors framing glass curtain walls need square sections that sit flush against mullion brackets — rounded corners from a standard ERW run create gaps that require shimming and extra weld passes. Our welded square steel tube is rolled to ±1% tolerance across the 19×19 to 800×800 range, so 50×50 and 100×100 architectural members land square against connection plates without field grinding. For galvanized finishes, the zinc coat is applied after forming, preserving corner coverage that pre-galvanized sheet cannot guarantee on heavy-wall sections.
Structural Compliance and Certification Path
Load-bearing frames for buildings and bridges must conform to EN 1993 or AISC design rules, which reference EN 10219 for cold-formed welded hollow sections and ASTM A500 for North American projects. Selecting S355 over S235 raises yield capacity for long-span bracing, while STK400 satisfies JIS-spec structural work in Southeast Asia. CE marking per EN 10210 / EN 10219 is mandatory for EU customs clearance; without it, the shipment sits at the port regardless of price [NEED_CITE: CE marking requirements for structural steel hollow sections in EU member states]. Wall thickness from 1 to 30 mm covers both light gauge purlin work and heavy column sections, and 6m / 12m定尺 lengths reduce on-site splicing.
Reading the Steel Grade Card
Gr.B, S235, S275, S355, and STK400 span three standard systems — ASTM, EN, and JIS — but they are not interchangeable without an equivalence check. S355 delivers higher yield than S235, making it the default for moment frames; Gr.B remains the workhorse for general construction in the Americas. ERW welding produces a longitudinal seam that is normalized online, giving a weld zone mechanical property close to the parent metal — suitable for static and moderate dynamic loads. Surface choice depends on environment: hot-dip galvanized for coastal or industrial corrosion, black painted or bare for projects where the contractor will apply intumescent fire coating or a multi-layer paint system themselves [NEED_CITE: steel grade equivalence between ASTM A500, EN 10219, and JIS G3466].
The Hidden Cost of a Cheap Mill Cert
Ordering welded square steel tube on price alone invites three failure modes: wall thickness below the ordered nominal, a mill test certificate that does not match the heat number stamped on the tube, and missing CE documentation that triggers a customs hold. Each failure stops the project — re-rolling costs the original price again, air-freighting replacement members wipes the margin, and a failed structural inspection can shut down an entire erection sequence [NEED_CITE: consequences of non-conforming structural steel in construction projects].
Why Buyers Return for the Next Project
Every welded square steel tube leaving our Jinan mill passes through an in-house physical and chemical laboratory — chemistry, tensile, flattening, and dimensional checks are logged per heat number before the pipe moves to the loading bay. We hold CE certification under EN 10210 and EN 10219, ISO 9001:2015, and Singapore FPC, so EU, Middle East, and Southeast Asian imports clear without document disputes. With 2,800+ specifications in stock and the ability to roll non-standard sizes, a single order can combine 50×50 curtain wall members and 300×300 column sections in one container, eliminating the need to split procurement across multiple mills. Third-party inspection by SGS or BV is arranged on request, and professional container loading with anti-damage measures prevents the bending and zinc scratching that plague poorly stuffed shipments.
Documentation & Compliance
- Mill Test Certificate documenting Gr.B / S355 chemical composition and yield strength per ASTM A500 or EN 10219, traceable by heat number
- CE certificate covering EN 10210 and EN 10219 for structural hollow section export to EU member states
- ISO 9001:2015 quality management certificate for the welded square steel tube production line
- SGS or BV third-party inspection report verifying wall thickness, dimension, and surface coating before shipment
- Material traceability tag linking each bundle to its heat number, steel grade, and size
- Full customs pack: packing list, bill of lading, and certificate of origin matching the commercial invoice
Packaging, Loading & Delivery
- Black painted and bare welded square steel tube bundled with steel strips and seaworthy wrapping; galvanized bundles include edge protectors to preserve the zinc coat during ocean transit
- 6m and 12m lengths loaded in dedicated 20ft or 40ft containers with timber chocks to prevent shifting and corner damage
- Random-length and cut-to-order tubes marked with heat number, steel grade (S355 / Gr.B), and size at both ends for site identification
- FOB Jinan / Qingdao, CIF destination port, or DDP door delivery arranged with forwarders experienced in structural steel
- Container loading plan provided before stuffing, optimized for the 19×19 to 800×800 size mix in the order
Securing Your Quote and Mill Test Certificate
Send the size schedule, steel grade, surface finish, tonnage, and destination port — we return a detailed offer with unit price, typical production lead time, and the applicable mill test certificate format within 12 hours. Non-standard sizes outside the 19×19–800×800 range are quoted against drawing, and third-party inspection slots are reserved before production starts.
Frequently Asked Questions
Q: Can ASTM A500 Gr.B be substituted with EN S355JR on the same project?
A: They belong to different standard systems and are not direct equivalents; substitution requires the project engineer to verify chemical and mechanical compatibility per EN 10219 or ASTM A500. We supply both grades and issue separate mill test certificates for each.
Q: How is wall thickness verified before shipment?
A: Every welded square steel tube is measured with calibrated ultrasonic gauges at four points per end; results are recorded in the mill test certificate and can be witnessed by SGS or BV on request.
Q: What is the minimum order quantity for non-standard sizes?
A: Standard sizes from 19×19 to 800×800 mm ship from stock with a 5-ton MOQ; custom non-standard sections require a production run, and the MOQ is confirmed after drawing review.
Q: Is CE marking mandatory for EU import?
A: Yes, structural hollow sections entering the EU must carry CE marking under EN 10210 or EN 10219, supported by a Declaration of Performance and factory production control certificate.
Q: Can galvanized and black painted tubes be mixed in one container?
A: Yes, with proper separation and edge protection to prevent zinc dust contamination on the painted surface; the loading plan is shared before stuffing.
Request Your Welded Square Steel Tube Quote
Submit your size schedule, steel grade, and destination port to receive a detailed offer with mill test certificate format and third-party inspection option within 12 hours.
Mobile / WhatsApp / WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
