Description
Factory-Direct ERW Square Tube — Dedicated production lines covering 2,800+ specifications ship directly to your site with full mill test certificates and third-party inspection reports.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (Square Hollow Section / SHS) |
| Steel Grade | Gr.B, S235, S275, S355, STK400, Q235B, Q345B |
| Standard | ASTM A500, ASTM A53, GB/T 3091, EN 10219, EN 10210, JIS G3466 |
| 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 (Electric Resistance Welded) |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Processing Service | Bending, Cutting |
| Application | Steel structures / Construction frames / Curtain wall / Support tubes / Building structures / Machinery frames |
| MOQ | 5 Tons |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial warehouses and commercial buildings |
| Construction Companies | Curtain wall support systems and high-rise building structural frames |
| Machinery Manufacturers | Equipment base frames and conveyor system support structures |
| Infrastructure Developers | Bridge support columns and solar farm mounting structures |
What Wall-Thickness Tolerance Costs on an ASTM A500 Welded Square Steel Tube Order
Negative tolerance beyond specification limits triggers structural recalculation failures and customs rejection.
I once inspected a container of welded square tubes at a Southeast Asian port where the buyer’s third-party surveyor measured wall thickness consistently below the contract minimum. The entire shipment was rejected — not because the steel was weak, but because the actual cross-section could not meet the load calculations submitted to the local building authority. Replacing the material meant three months of delay and double freight costs. This is what happens when wall-thickness tolerance drifts beyond ±1%: the mill test certificate says one thing, but the physical product tells another story. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
Matching Load Requirements Across Structural Frame Applications
An ASTM A500 welded square steel tube in S355 grade carries significantly higher point loads than the same dimension in S235, which directly affects column spacing and beam sizing in steel frame design. For curtain wall support systems, the 19mm to 100mm size range with 1–3mm wall thickness provides adequate rigidity while keeping weight manageable for crane operations. When these tubes form part of conveyor structures in machinery plants, the ERW weld seam must pass ultrasonic testing to ensure no internal defects compromise fatigue resistance under continuous vibration. Our in-house physical and chemical laboratory tests every heat before the tubes leave the mill, so the mill test certificate matches what arrives at your job site.
Engineering Compliance and Certification Pathways
Structural frames designed under EN 1993 require hollow sections certified to EN 10219 or EN 10210, while North American projects specify ASTM A500 Grade B or C — mixing these standards on a single project creates inspection conflicts that delay handover. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 specifications] For projects in corrosive coastal environments, hot-dip galvanized surface treatment extends service life far beyond black painted or bare alternatives, though the zinc coating adds cost that must be justified by the exposure conditions. Custom cutting to exact lengths eliminates on-site welding for simple connections, but structural moment frames still require full-penetration welds prepared from plain ends. CE certification under EN 10210 and EN 10219 is mandatory for EU market entry, and missing this document at customs means the container sits at port until the paperwork catches up — or gets returned.
Steel Grade Selection and ERW Welding Process Fundamentals
The S-series grades (S235, S275, S355) follow European naming conventions where the number indicates minimum yield strength in MPa, making S355 the default choice for heavily loaded columns and transfer beams. Q235B and Q345B serve the same purpose in Chinese-standard projects, with Q345B offering roughly 50% higher yield strength than Q235B for applications where weight reduction matters. ASTM A500 Gr.B aligns closely with S275JR in mechanical properties, allowing cross-standard substitution when the engineer approves. The ERW process forms the tube by rolling steel strip into a square profile and passing high-frequency current through the open edges to forge them together — this creates a continuous weld seam along one face that must be inspected for lack of fusion or inclusions. [NEED_CITE: ERW weld seam quality inspection methods for structural hollow sections] For thickness above 10mm, some mills switch to submerged arc welding, but ERW remains cost-effective and dimensionally accurate for the 1–30mm range covered here. Surface treatment choice depends on the installation environment: bare tubes work for indoor, painted frames; galvanized tubes handle outdoor exposure without maintenance for decades; varnished surfaces provide temporary protection during transit and fabrication.
Hidden Costs of Procuring the Wrong Specification
Ordering S235 when the structural engineer specified S355 means the tubes arrive with insufficient yield strength — the building passes visual inspection but fails the load test, requiring complete frame replacement. [NEED_CITE: consequences of steel grade substitution in structural engineering] Missing CE marks on an EU-bound shipment means customs holds the container for weeks while the importer scrambles for retroactive certification — if the mill cannot provide it, the steel becomes scrap at the port. Negative tolerance beyond the standard limit means you pay for theoretical weight but receive less material, reducing the actual load capacity below what the design assumed. These are not theoretical risks — they are daily realities for buyers who accept the lowest quote without verifying the mill test certificate against the physical product.
Why Structural Steel Buyers Source Welded Square Tubes From Our Mill
We operate three dedicated ERW production lines producing over 2,800 specifications of square and rectangular hollow sections, so your 120×120×4.0mm tubes come from the same facility that makes 800×800×30mm columns — no trading company markup and no quality gaps between small and large orders. Every heat of steel is tested in our in-house physical and chemical laboratory before production begins, and the resulting mill test certificate travels with the shipment so your inspector can verify chemical composition and mechanical properties against the standard. Our 41 patented technologies include proprietary sharp-corner rectangular tube manufacturing that fills specification gaps other mills cannot cover, giving your project access to dimensions outside standard catalogs. CE certification under EN 10210 and EN 10219, ISO 9001:2015 quality management, and third-party inspection through SGS or BV ensure your shipment clears customs and passes project acceptance without documentation delays. We handle custom cutting to your exact lengths, special packaging for galvanized surfaces, and professional container loading plans that maximize weight per shipment — reducing your per-ton freight cost to destinations across 50+ countries.
Documentation & Compliance
- Mill test certificate documenting S355JR chemical composition and yield strength per EN 10219 for each heat number
- CE certificate confirming compliance with EN 10210 and EN 10219 for EU market structural applications
- ISO 9001:2015 quality management system certificate covering the full production process
- SGS or BV third-party inspection report verifying dimensional accuracy and surface quality before shipment
- Material traceability documentation linking each tube to its heat number and production date
- Customs clearance package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- ERW welded square tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized tubes wrapped with waterproof paper and plastic film to preserve the zinc coating in humid port environments
- Container loading plans optimized for 6m and 12m lengths to maximize weight per 20ft or 40ft container
- Custom cutting service available to deliver tubes in exact project lengths, reducing on-site waste and cutting labor
- Heat number and steel grade stenciled on each bundle for site identification and inspection traceability
- FOB, CIF, and DDP shipping options with real-time tracking to ports across EU, North America, Southeast Asia, and Middle East
Start Your Welded Square Steel Tube Procurement
Submit your specification sheet — including outer dimensions, wall thickness, steel grade, total quantity, and destination port — and receive a detailed quotation with unit pricing, production lead time, and applicable certification documents within 12 hours. We will confirm whether your required dimensions fall within standard catalog or need custom tooling, and provide the mill test certificate format for your engineer’s approval before production begins.
Request Your ASTM A500 Welded Square Steel Tube Quotation
Send your specifications to admin@sdxjysteel.com or contact us via WhatsApp at +86 188 5315 7756 to receive pricing and mill test certificate samples.
Frequently Asked Questions
Q: Can you provide ASTM A500 Grade B welded square steel tubes with CE certification for EU projects?
A: Yes, our welded square steel tubes are produced to ASTM A500, EN 10219, and EN 10210 standards simultaneously, and we hold CE certification for both EN 10210 and EN 10219, allowing the same product to serve EU and North American projects with appropriate documentation.
Q: What is the minimum order quantity for custom-cut welded square steel tubes?
A: The minimum order quantity is 5 tons, which applies to both standard catalog sizes and custom-cut lengths — we can cut tubes to your exact project requirements within this quantity threshold.
Q: How do you ensure wall thickness tolerance meets the ±1% specification?
A: Our in-house physical and chemical laboratory conducts incoming material inspection, in-process dimensional checks during ERW forming, and final inspection before shipment, with full measurement records included in the mill test certificate.
Q: Can you supply hot-dip galvanized welded square steel tubes for coastal construction projects?
A: Yes, we offer hot-dip galvanized surface treatment for welded square steel tubes, with the zinc coating applied after ERW welding to ensure complete coverage including the weld seam, suitable for corrosive coastal and industrial environments.
Q: Do you provide third-party inspection reports from SGS or BV?
A: Yes, we arrange SGS or BV third-party inspection at our facility before shipment, covering dimensional verification, surface quality assessment, and witness testing — the inspection report is included in your shipping documentation package.
