Description
Factory-Direct ERW Supply — Own steel mill and fabrication workshop eliminate third-party sourcing gaps for every welded square steel tube order.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Welded Square Steel Tube |
| Product Type | Square Hollow Section (SHS) |
| 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 / Building frames / Curtain walls / Support structures / Structural pipe applications |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Steel frame structures, building columns, beam-to-column connections |
| Industrial Facilities | Platform support structures, mezzanine frames, equipment bases |
| Architectural Engineering | Curtain wall support systems, facade structural sections, canopy frames |
| Infrastructure | Stairway handrails, walkway supports, bridge access structures |
Where Negative Tolerance on Welded Square Steel Tube Can Cost You an Entire Shipment
Wall thickness tolerance is not a rounding detail — it is the first line of defense at customs and on-site inspection.
I still remember a batch of 50×50 square tubes heading to Dubai. The wall thickness drifted past the negative tolerance limit, and the client rejected the entire container on the spot. We paid for rework, return freight, and — worse — lost credibility with a buyer who had trusted us for three years. Since then, every welded square steel tube we ship carries a ±1% tolerance guarantee backed by in-house dimensional inspection before loading. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed structural hollow sections]
When procurement teams source ERW square tubes from fragmented suppliers, material certificates often arrive with gaps. Heat numbers do not match the bundles. Wall thickness readings vary across the same lot. These inconsistencies trigger re-inspection delays, customs holds, and — in the worst case — structural rejection at the job site. A welded square steel tube supplier operating an integrated mill-to-fabrication chain closes every one of those gaps at the source.
How 19×19 to 800×800 ERW Square Tubes Fit Structural Frame Design
A welded square steel tube covering 19mm×19mm up to 800mm×800mm with wall thickness from 1 to 30 mm lets engineers specify one supplier for everything from light curtain-wall purlins to heavy column sections. The flat faces of square hollow sections simplify bolted and welded connections, reducing gusset plate complexity on building frames. For EPC contractors managing multi-discipline procurement, consolidating these sizes under a single welded square steel tube supplier cuts coordination overhead and keeps heat-number traceability intact from first cut to final bundle.
Structural Compliance and Surface Protection for Site Conditions
Load-bearing columns and frame members must conform to recognized engineering standards — ASTM A500 for North American projects, EN-compliant grades for European and Middle East tenders, GB/T 3091 for domestic-spec jobs. The welded square steel tube range covering Gr.B through S355 and STK400 gives specifiers cross-standard flexibility without switching mills. For outdoor or high-humidity environments, hot-dip galvanized coating extends service life far beyond black painted or bare finish. [NEED_CITE: ASTM A500 structural tubing specification requirements] Surface treatment choice should be locked before fabrication begins, since post-fabrication galvanizing adds cost and risks weld-zone coating damage.
Steel Grade Selection and ERW Weld Integrity Explained
Gr.B under ASTM A500 serves light structural work where moderate yield strength suffices — typical for non-load-bearing frames and support brackets. Stepping up to S235, S275, and S355 increases yield capacity progressively, matching heavier column and beam demands in multi-story construction. STK400 under JIS standards covers Japanese-spec infrastructure projects common across Southeast Asia. The ERW welding process produces a longitudinal seam with consistent fusion quality across the full 1–30 mm wall range, and the ±1% tolerance on the welded square steel tube ensures that theoretical weight calculations match actual delivered weight — critical when billing is by tonnage. Negative tolerance beyond specification limits reduces load capacity and triggers inspection failure, which is why our in-house lab checks every heat before the tube leaves the line. [NEED_CITE: steel grade equivalence between ASTM A500 Gr.B and EN S235/S355]
Hidden Costs of Sourcing Welded Square Steel Tube Without Verified Certification
Buying from a trading company that sources raw tubes from unknown mills means the mill test certificate may not match the delivered material. Heat numbers on the MTC might belong to a different batch entirely. When the client’s third-party inspector pulls random samples and finds chemistry outside the S355 range, the entire lot gets quarantined. Customs authorities in the EU and Middle East increasingly demand EN 10219 or equivalent documentation at the port of entry — without it, containers sit in bonded warehouses accruing demurrage. [NEED_CITE: EN 10219 cold-formed structural hollow section compliance for EU import]
Why Procurement Teams Choose an Integrated Mill and Fabrication Source
Our own steel production facility feeds the fabrication workshop directly, so every welded square steel tube carries traceable chemistry from the melt shop to the finished bundle. With over 2,800 specifications in stock, buyers sourcing mixed sizes for a single project avoid splitting orders across multiple suppliers. Certified welding procedures and qualified welders handle any custom fabrication — shop drawing review, cutting, drilling, and assembly — under one quality system. Third-party inspection through SGS or BV is available before shipment, and the complete documentation package travels with every container. Professional loading teams plan oversized cargo stowage to prevent transit damage on long ocean routes.
Documentation & Compliance
- Mill Test Certificate documenting Gr.B, S235, S275, or S355 chemical composition and mechanical properties per ASTM A500 or EN standard
- Material traceability report linking each welded square steel tube bundle to its original heat number from our own steel mill
- SGS or BV third-party inspection report covering dimensional checks, weld seam quality, and coating thickness verification
- ISO 9001 quality management certificate covering the integrated production and fabrication process
- Full customs document set including packing list, bill of lading, and certificate of origin for destination-country clearance
- Coating certificate for galvanized or painted welded square steel tube specifying surface treatment type and application standard
Packaging, Loading & Delivery
- Welded square steel tubes bundled with high-tensile steel strips and edge protectors to maintain ±1% dimensional tolerance during ocean transit
- Galvanized finish protected with anti-scratch separators between layers to preserve zinc coating integrity at connection points
- Mixed-size container loading optimized for 5.8m, 6m, and 12m lengths to maximize payload per 20ft and 40ft open-top or standard container
- Plain ends capped or wrapped to prevent moisture ingress on bare and black painted welded square steel tube during storage
- Heat number and steel grade stenciled on each bundle for on-site identification and inspection traceability
- FOB, CIF, and DDP shipping terms available with door-to-door tracking for EPC project sites across the Middle East, Southeast Asia, and Africa
Getting a Quote Starts With Your Drawing
Send your project drawings in PDF or DWG format along with the required steel grade, size range, surface treatment, and destination port. Our engineering team responds within 24 hours with a detailed quotation covering material, fabrication, coating, packing, and freight — plus a shop drawing timeline and production schedule. For welded square steel tube orders requiring custom lengths or non-standard sizes, we confirm MOQ flexibility and lead time before you commit.
Frequently Asked Questions
Q: How do ASTM A500 Gr.B, EN S235/S355, and GB Q235/Q345 compare for welded square steel tube specification?
A: These grades belong to different national standards but serve similar structural roles. Gr.B under ASTM A500 is common in North American projects, S235 and S355 under EN standards cover European and Middle East tenders, and Q235/Q345 under GB standards apply to Chinese-spec jobs. Our integrated mill produces welded square steel tube across all these grades, and we provide cross-reference documentation to help specifiers confirm equivalence for their project requirements.
Q: Can third-party inspection be arranged before shipment of welded square steel tube?
A: Yes. SGS and BV inspection services are available for dimensional verification, weld seam quality checks, coating thickness measurement, and material sampling. The inspection report is included in the shipping documentation package.
Q: What surface treatment options are available for different project environments?
A: Hot-dip galvanized coating suits outdoor and high-corrosion environments, extending service life significantly. Black painting provides basic rust protection for indoor or temporary applications. Varnish and bare finish serve projects where the buyer handles coating on-site or where the tube will be enclosed in a protected structure.
Q: What is the minimum order quantity for custom-length welded square steel tube?
A: The standard MOQ is 5 Tons. For non-standard lengths or sizes outside the regular 19mm×19mm to 800mm×800mm range, we confirm feasibility and MOQ adjustment based on the specific order requirements.
Q: How is theoretical weight versus actual weight handled for billing?
A: Orders can be billed by theoretical weight based on standard density calculations or by actual weighbridge weight at the mill. Our ±1% wall thickness tolerance ensures the variance between theoretical and actual weight stays within acceptable limits, and the billing method is confirmed before contract signing.
Secure Your Welded Square Steel Tube Supply With Verified Documentation
Send your project specifications, steel grade, and destination port to receive a detailed quotation and mill test certificate sample within 24 hours.
Mobile/WhatsApp/WeChat: +86 188 5315 7756 | Email: admin@xjystructure.com
