Description
Factory-Direct ERW Welded Square Steel Tube — Every Q235B and Q345B tube shipped with in-house lab test reports and CE/ISO documentation, eliminating middleman markups and certification gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B ERW Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, SS400, SGCC, CGCC |
| Standard | ASTM, JIS, ISO 9001, API, TISI |
| Section Shape | Square |
| Size Range | 20×20–200×200 mm |
| Wall Thickness | 0.5–40 mm |
| Length | 1–12 m (standard: 6 m / 6.4 m / 12 m) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled / Galvanized Coating |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Structure Pipe, Construction Structure, Bridge, Boiler, Fluid Pipe, Hydraulic Pipe, Gas Pipe, Mining |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Construction | Building structural frames, scaffolding systems, bridge support columns |
| Machinery Manufacturers | Hydraulic cylinder bodies, conveyor support structures, equipment bases |
| Oil & Gas / Industrial | Gas distribution pipelines, chemical fertilizer transport lines, boiler systems |
| Mining | Underground support structures, ventilation ducting frames, ore processing platforms |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on ERW welded square steel tube means the difference between passing third-party inspection and watching a full container get held at port.
I have seen projects delayed for weeks because wall thickness drifted beyond acceptable limits. When you order Q345B square tubes for load-bearing frames, even 0.3mm negative deviation can trigger re-inspection at destination. Structural engineers specify EN 10219 or ASTM A500 for a reason — those standards define what “acceptable” actually means. Without real-time lab verification during production, you are gambling on paper certificates that may not reflect the steel sitting in your container. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
How ERW Welded Square Steel Tube Matches Structural Engineering Demands
ERW welded square steel tube in Q235B and Q345B grades delivers the dimensional precision that structural connections require. The electric resistance welding process produces a clean, consistent weld seam that handles load transfer at beam-column joints without stress concentration. When your design calls for 100×100 mm or 150×150 mm sections with 6–12 mm walls, ERW technology maintains ±1% tolerance across the full length — critical for bolted or welded connections in scaffolding and building frames. Our in-house physical and chemical lab tests every heat before the tube leaves the mill, so the mill test certificate you receive matches the steel you install.
Engineering Compliance and Certification for Global Projects
Structural applications demand more than just the right dimensions. Q235B and Q345B grades conform to Chinese GB standards, but international projects often require cross-reference to EN 10219 (S235/S355) or ASTM A500 (Grade B/C). We provide material equivalence documentation so your engineer can verify compliance without guessing. For EU markets, CE certification under EN 10210/EN 10219 is mandatory — our factory holds this certification along with ISO 9001:2015 and Singapore FPC. Third-party inspection by SGS or BV is available before shipment, giving you independent verification that the Q345B tubes meet your project’s structural specifications. [NEED_CITE: steel grade equivalence between GB Q series and EN S series standards]
Understanding ERW Process and Steel Grade Selection for Square Tubes
ERW (Electric Resistance Welded) square tubes are formed from steel coil and welded along the seam using electrical resistance heat — no filler metal, just pressure and current. This process works well for structural applications where the weld seam does not face extreme bending or internal pressure. Q235B offers good formability and weldability for general construction, while Q345B provides higher yield strength for heavier load requirements. The choice between cold rolled and galvanized surface depends on your environment: cold rolled gives a clean finish for indoor structural work, while galvanized coating protects against corrosion in outdoor or humid conditions. Wall thickness from 0.5 mm to 40 mm covers everything from light gauge framing to heavy industrial supports. Our ±1% tolerance control means you get what you specify — no surprises when the inspector pulls out the caliper.
Hidden Costs of Incorrect Steel Grade or Missing Certification
Ordering the wrong steel grade or accepting tubes without proper certification creates costs that appear long after delivery. A Q235B tube substituted for Q345B in a load-bearing frame may pass visual inspection but fail under design loads — or worse, pass inspection today and fail during the building’s service life. Missing CE documentation for EU projects means customs holds, demurrage charges, and potential rejection at port. Inconsistent wall thickness forces your fabrication shop to rework connections or scrap material. These are not theoretical risks — they are the reason experienced procurement teams demand mill test certificates with chemical composition and mechanical properties for every heat, verified by third-party inspection when the order value justifies it. [NEED_CITE: consequences of material certification gaps in structural steel procurement]
Why Procurement Teams Choose Our ERW Welded Square Steel Tube Supply
We operate three dedicated production lines with in-house physical and chemical laboratories, so every ERW welded square steel tube is tested before it ships — not just sampled. Our 41 patents include proprietary sharp-corner rectangular tube technology, but for standard square tubes, we focus on what matters: consistent wall thickness, accurate dimensions, and documentation that clears customs. With 2,800+ specifications in stock or short production runs, we handle full-range procurement so you do not need to source pipes, plates, and sections from five different suppliers. Factory-direct pricing means no trading company markup, and our export team manages logistics to 50+ countries with professional container loading plans that maximize weight per shipment. CE, ISO, SGS, and BV certifications are standard, not optional extras.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition and mechanical properties per GB standards, with heat number traceability
- CE certificate under EN 10210/EN 10219 for EU market compliance, covering structural hollow sections
- ISO 9001:2015 quality management certificate covering the full production and inspection process
- SGS or BV third-party inspection report available upon request, verifying dimensions, wall thickness, and surface quality
- Material traceability by heat number from steel coil to finished tube, recorded in mill test documentation
- Customs documents including packing list, bill of lading, and certificate of origin for import clearance
Packaging, Loading & Delivery
- ERW welded square steel tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized coated tubes wrapped with waterproof paper and plastic film to preserve zinc layer integrity
- Container loading optimized for 20ft and 40ft shipments based on tube dimensions (20×20 to 200×200 mm) and length (6 m / 12 m standard)
- Custom cutting to project-specific lengths available, reducing on-site waste and handling
- Heat number and steel grade marked on each tube for site identification and traceability
- FOB, CIF, and DDP shipping options with door-to-door logistics coordination to 50+ countries
How to Request a Quote for ERW Welded Square Steel Tube
Submit your specifications including outer dimensions, wall thickness, steel grade (Q235B or Q345B), quantity, and destination port. We respond within 12 hours with unit pricing, delivery timeline, and available certifications. For non-standard sizes or custom lengths, we provide feasibility confirmation and production scheduling. All quotes include mill test certificate and third-party inspection options so you can verify compliance before committing to production.
Frequently Asked Questions
Q: Can you provide mill test certificates for Q235B and Q345B ERW welded square steel tubes?
A: Yes, every shipment includes original mill test certificates documenting chemical composition and mechanical properties for each heat number. Third-party inspection by SGS or BV is available upon request for additional verification.
Q: What is the tolerance on wall thickness for your ERW welded square steel tubes?
A: We maintain ±1% tolerance on wall thickness across the full range from 0.5 mm to 40 mm. Our in-house laboratory conducts incoming, in-process, and final inspections to ensure compliance with your specifications and applicable standards.
Q: Do you stock Q235B and Q345B square tubes, or is everything made to order?
A: We maintain inventory of common sizes in Q235B and Q345B grades for fast delivery. Non-standard dimensions or large quantities are produced to order with typical production lead times confirmed at quotation stage.
Q: Can you supply CE-certified ERW welded square steel tubes for EU projects?
A: Yes, our factory holds CE certification under EN 10210/EN 10219 for structural hollow sections. We provide CE documentation along with ISO 9001:2015 certificate and can arrange third-party inspection for EU customs compliance.
Q: What surface treatment options are available for ERW welded square steel tubes?
A: We offer cold rolled (bare) surface for indoor applications and galvanized coating for corrosion protection in outdoor or humid environments. Surface treatment choice depends on your project environment and design specifications.
Q: How do you handle container loading for mixed-size orders?
A: Our logistics team creates professional loading plans that maximize container weight capacity based on your specific tube dimensions and lengths. We coordinate FOB, CIF, or DDP shipping with real-time tracking to destination port.
Get Your ERW Welded Square Steel Tube Quote with Mill Test Certificate
Send your specifications to admin@sdxjysteel.com or contact us via WhatsApp at +86 188 5315 7756. We respond within 12 hours with pricing, certification options, and delivery timeline for your project.
