Description
Direct Mill Supply, No Middlemen — Every Q235B ERW welded square steel tube ships from our own production lines in Jinan, backed by in-house lab testing and full mill test certificates.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q195, Q235, Q235B, Q345, Q345B, S235JR, S275JR, S355JR, St37, St37-2, St35, St35.4, St42, St52.4 |
| Standard | ASTM |
| Section Shape | Square |
| Size Range | 40x40mm, 40x60mm, 40x80mm |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Black (Non-oiled) |
| Length | 6m, 6.4m, 12m |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building column frames, roof truss systems, warehouse structural supports |
| Machinery Manufacturing | Equipment base frames, conveyor support structures, crane boom sections |
| Scaffolding & Temporary Works | Scaffold uprights, cross bracing, shoring tower legs |
| Industrial Piping | Low-pressure fluid transfer, gas distribution lines, chemical fertilizer feed pipes |
When ±1% Tolerance Decides Whether Your Frame Goes Together
Dimensional drift on ERW square tubes costs more in rework than the price difference between suppliers.
I have watched site crews spend half a day grinding weld prep becausethe flanges on a 40x80mm tube were out of square by 2mm over 6 meters. On a structural frame with 40 connection nodes, that adds up to days of lost labor. Standard welded tubes from mills running high-speed lines often push tolerance to the edge — or past it. Our Q235B ERW welded square steel tube holds ±1% across the full 6m and 12m length because we control the forming roll gap and weld seam temperature in-house. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching 40–80mm Square Sections to Structural Load Paths
The 40x40mm to 40x80mm size range covers the light-to-medium structural members used in warehouse mezzanines, equipment platforms, and curtain wall sub-frames. Q235B grade delivers adequate yield for non-critical load paths, while Q345B steps up for heavier point loads. The hot rolled black surface accepts primer and topcoat without additional blast cleaning, which matters when you are coating on-site in Southeast Asia or the Middle East where blasting crews are scarce.
Engineering Compliance and Grade Substitution on Site
Projects specifying ASTM A500 Gr.B often accept Q235B as a functional equivalent, but customs and third-party inspectors need documentation that maps chemistry and mechanicals correctly. [NEED_CITE: steel grade equivalence between GB Q235B and ASTM A500 standards] Our Q235B ERW welded square steel tube ships with mill test certificates that list carbon, manganese, silicon, sulfur, and phosphorus content alongside yield and tensile results — so your EU or Middle East inspector signs off without requesting a re-test. For projects in Australia or Singapore, we can supply to AS1163 C350 on request.
Why ERW Welding Works for Square Hollow Sections
Electric resistance welding fuses the strip edges under pressure without filler metal, producing a weld seam that matches the parent metal in strength when the process is controlled. For square tubes in the 40–80mm range, ERW offers tighter dimensional accuracy than seamless at lower cost, with consistent wall thickness around the perimeter. The hot rolled black finish you see on our Q235B ERW welded square steel tube means no oil film — the surface is ready for welding, painting, or galvanizing without solvent degreasing first. That saves a step on every connection joint.
The Real Cost of Buying Cheap Square Tubes Without Certificates
A 40x80mm Q235B tube priced 8% below market often means wall thickness is running at the negative tolerance limit — or the chemistry is off-grade. When that tube goes into a scaffold upright or a mezzanine beam, the structural engineer’s calculations no longer hold. [NEED_CITE: consequences of sub-standard steel tube wall thickness on structural safety] Customs in the EU and GCC countries increasingly reject hollow sections without valid EN 10219 or ASTM A500 test reports. You pay for the tube, pay for return freight, and pay for the replacement — three times the original cost.
Why Buyers Choose SD XJY Pipe for ERW Square Tubes
We run three dedicated production lines covering over 2,800 specifications, so your 40x60mm Q235B order does not get bundled into someone else’s off-standard run. Every Q235B ERW welded square steel tube passes through our in-house physical and chemical lab before it leaves the mill — dimensional checks, tensile tests, and chemistry analysis are done on-site, not outsourced. We hold ISO 9001:2015, Lloyd’s CE certification for EN 10219, and Singapore FPC, so your project documentation is covered from Dubai to Dusseldorf. Custom lengths up to 12m, cut-to-size, and professional container loading with anti-damage measures are standard — not extras.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition and mechanical properties per ASTM standards
- CE certificate confirming EN 10219 compliance for structural hollow sections exported to EU markets
- ISO 9001:2015 quality management certificate covering the full ERW welding and forming process
- SGS or BV third-party inspection report available upon request for destination customs clearance
- Heat number traceability from steel strip coil to finished Q235B ERW welded square steel tube bundle
- Full export documentation set: packing list, bill of lading, certificate of origin, and commercial invoice
Packaging, Loading & Delivery
- Q235B hot rolled black square tubes bundled with steel strips and edge protectors to prevent surface scratching during transit
- Non-oiled black finish requires no special wrapping — bundles are stacked with timber spacers for ventilation and moisture control
- 6m and 12m lengths loaded in 20ft and 40ft containers with optimized nesting for 40x40mm to 40x80mm sections to maximize payload
- Cut-to-length service available for 6.4m or other project-specific lengths, with each piece marked by heat number and steel grade
- FOB Jinan or Qingdao port standard; CIF and DDP terms arranged to 50+ countries with full tracking until arrival
Getting Your Q235B Square Tube Quote Right the First Time
Send us the size (40×40, 40×60, or 40x80mm), wall thickness, length, steel grade, and quantity — along with your destination port. We respond within 12 hours with unit pricing, production lead time, and the mill test certificate format your inspector expects. If you need custom sizes outside the standard range or third-party inspection arranged before loading, we confirm that in the same quotation.
Frequently Asked Questions
Q: What is the difference between Q235B and S235JR steel grades?
A: Both are mild carbon structural steels with similar yield strength levels. Q235B follows the Chinese GB/T 700 standard, while S235JR follows the European EN 10025 standard. The main difference lies in impact testing requirements — S235JR requires Charpy impact testing at 20°C, while Q235B does not mandate impact testing unless specified. For most structural applications in non-cold environments, they are functionally interchangeable.
Q: Can you provide third-party inspection certificates for EU customs clearance?
A: Yes. We arrange SGS or BV inspection at our mill before shipment. The inspection covers dimensional checks, visual surface quality, wall thickness measurement, and witness of mechanical testing. The third-party report is issued alongside our mill test certificate and CE document, which together satisfy EU customs requirements for structural hollow sections under EN 10219.
Q: What is the minimum order quantity for custom sizes?
A: Standard sizes in the 40x40mm to 40x80mm range have a 1 ton MOQ. For non-standard dimensions outside our regular production schedule, the MOQ depends on the specific size and wall thickness — typically 5 to 10 tons to justify a dedicated mill run. We confirm the exact MOQ and lead time once we receive your size specification.
Q: How do you ensure dimensional accuracy during ERW welding?
A: Our ERW lines use precision forming rolls that control the tube perimeter within ±1% tolerance. The weld seam is monitored for penetration and consistency using inline sensors. After welding, each tube passes through a sizing stand that corrects any ovality before cutting to length. Final dimensional inspection includes side length, wall thickness at four points, and straightness check over the full 6m or 12m length.
Q: What surface treatment options are available for corrosion protection?
A: The standard finish is hot rolled black (non-oiled), which is suitable for indoor structural use or as a base for painting and galvanizing. We also supply galvanized square tubes (pre-galvanized or hot-dip galvanized) for outdoor or corrosive environments. If your project requires powder coating or epoxy primer, we can arrange that through our coating partners before delivery.
[Request Your Q235B ERW Square Tube Quotation]
Submit your size, grade, quantity, and destination port to receive pricing and mill test certificate samples within 12 hours.
Contact: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
