Description
Mill-direct Q235 tube supply — ERW square and rectangular steel tubes produced in-house from billet to finished section, eliminating third-party material gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Carbon Steel Square & Rectangular Steel Tube |
| Product Type | Square / Rectangular Steel Tube (SHS / RHS) |
| Steel Grade | Q195, Q215, Q235, Q345, 10#, 20# |
| Standard | BS EN, GB (GB/T 8162, GB/T 6728), ASTM (A500, A53), JIS (G3466, G3448), DIN |
| Section Shape | Square / Rectangular |
| Size Range (OD) | 10×10 mm – 500×500 mm |
| Wall Thickness | 0.9 – 25 mm |
| Length | 6 m / 9 m / 12 m (customized available) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Cold Rolled / Oiled / Customer’s Requirement |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures, construction frames, transmission towers, piling, municipal projects, mechanical industry, pipeline engineering |
| MOQ | 500 KG |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, column-beam assemblies, transmission tower members, piling supports |
| Industrial Facilities | Machinery frames, equipment platforms, conveyor structures, pipeline supports |
| Municipal & Civil Engineering | Water and gas pipeline engineering, road barrier posts, bridge auxiliary structures |
| Mechanical Industry | Hydraulic cylinder bodies, crane boom sections, structural brackets |
What Negative Tolerance Costs on a Q235 Square Steel Tube Order
A ±1% wall-thickness tolerance is not a marketing line — it is the difference between passing third-party inspection at destination or watching a full container get rejected.
I learned this the hard way years ago when a batch of Q235 tubes shipped to São Paulo came back flagged: actual wall thickness fell well below the negative tolerance limit allowed by GB/T 6728. The buyer’s third-party inspector caught it before erection, but the rework cost and schedule delay were entirely avoidable. When overseas fabricators source tubes from unrelated mills, the material traceability chain breaks at the first link. A Q235 square steel tube manufacturer that controls the entire process from raw steel to finished section removes that uncertainty — one heat number, one test certificate, one accountable source. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
How Q235 ERW Tubes Match Structural Frame Requirements
Structural frames in commercial buildings and industrial plants demand consistent section geometry and reliable weldability. Q235, as the most widely specified carbon structural grade in the GB system, offers balanced formability and strength for frame columns, beam assemblies, and bracing members. The ERW process produces a clean longitudinal weld seam that integrates well with standard MIG/MAG and SAW procedures used on-site. With outer dimensions spanning from 10×10 mm small-section tubes for bracing up to 500×500 mm heavy sections for main columns, a single Q235 square steel tube manufacturer can supply the full range without splitting orders across multiple vendors.
Engineering Compliance and Certification Pathways
Projects targeting EU markets require hollow sections conforming to EN 10219, while North American specifications typically call for ASTM A500 or A53 compliance. The Q235 grade maps directly to S235 in the EN system and approximates A53 Grade B in ASTM, but equivalence must be documented — not assumed. Customs authorities in multiple jurisdictions now request CE marking or third-party inspection reports alongside mill certificates. [NEED_CITE: steel grade equivalence mapping between GB, EN, and ASTM standards] Our fabrication division reviews shop drawings against the specified standard before production begins, ensuring that the Q235 square steel tube delivered meets both the dimensional and documentation requirements of the destination market.
Understanding Q235 Grade and ERW Process Selection
Q235 belongs to the Chinese GB carbon structural steel series, where the number indicates the minimum yield point in MPa. It sits between Q195 (lighter forming work) and Q345 (higher-strength structural applications), making it the default choice for general construction frames and non-pressure structural members. The ERW welding technique fuses the strip edges through resistance heating without filler metal, producing a uniform seam suitable for sections up to 25 mm wall thickness. Compared to seamless tubes, ERW offers tighter dimensional control on wall thickness across the full cross-section — critical when theoretical weight calculations drive project costing. Surface options include oiled finish for short-term transit protection or cold-rolled surface for applications requiring further painting or coating. [NEED_CITE: ERW versus seamless hollow section manufacturing process comparison]
Hidden Costs of Sourcing from Unverified Suppliers
Choosing a lower unit price from an unverified source often shifts cost downstream. Material certificates that cannot be traced to a specific heat number create problems during project handover. Wall thickness exceeding the permitted negative tolerance triggers rejection at the port of destination — and return shipping or local rework dwarfs any initial savings. Non-conforming end preparation or inconsistent surface treatment adds field-modification labor that erases procurement savings. [NEED_CITE: structural steel procurement quality failure cost implications]
Why Procurement Teams Choose Our Q235 Square Steel Tube Supply
We operate both the steel production facility and the fabrication workshop under one roof, meaning every Q235 square steel tube we ship carries full traceability from the original billet heat number through to the finished section. Our raw material inventory covers over 2,800 specifications, so standard and non-standard sizes ship from stock rather than waiting for a third-party mill to schedule a run. Every order includes a mill test certificate documenting chemical composition and mechanical properties per the specified standard, and we welcome SGS, BV, or TÜV third-party inspection at any production stage. For projects requiring both tubes and fabricated components — columns, beam assemblies, connection plates — our integrated supply eliminates the coordination gap between material supplier and fabricator.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition and mechanical properties per GB/T 6728 or EN 10219 as specified
- CE certificate for EN 10219 cold-formed structural hollow sections where EU market delivery is required
- ISO 9001 quality management certificate covering the full production and inspection process
- SGS or BV third-party inspection report available upon request for wall thickness, dimensional checks, and visual weld examination
- Full material traceability linking each tube bundle to its original heat number and rolling batch
- Export documentation package including packing list, bill of lading, and certificate of origin for destination customs clearance
Packaging, Loading & Delivery
- Q235 ERW square and rectangular tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Oiled surface treatment applied before bundling to prevent corrosion during extended shipping periods to Middle East and African ports
- Container loading optimized for 6 m and 12 m lengths with wooden crate packaging available for precision-cut sections
- Heat number and Q235 grade stenciled on each bundle for on-site identification and traceability verification
- FOB, CIF, and DDP delivery terms supported with professional oversized cargo loading plans for heavy-wall sections
Ready to Start Your Q235 Tube Procurement
Share your project drawings, required steel grades, section dimensions, and destination port — we respond within 24 hours with a detailed quotation including material, fabrication, coating, and logistics costs. Our engineering team will review shop drawings and confirm standard compliance before production begins.
Get Your Q235 Square Steel Tube Quote Today
Send your specifications and quantity to receive pricing with full mill test certification.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Website: www.xjystructure.com
Frequently Asked Questions
Q: How does Q235 compare to S235 and A53 Grade B for international projects?
A: Q235 is the Chinese GB standard equivalent of S235 in the EN system and closely matches A53 Grade B in ASTM. For projects requiring formal equivalence documentation, we provide cross-reference certificates and can supply material tested to multiple standards simultaneously.
Q: Can you arrange third-party inspection before shipment?
A: Yes. We welcome SGS, BV, or TÜV inspection at any production stage. Third-party reports covering wall thickness, dimensional accuracy, and visual weld examination are included in the documentation package.
Q: What is the minimum order quantity for non-standard sizes?
A: Our standard MOQ is 500 KG. For non-standard dimensions outside the 10×10 mm to 500×500 mm range, minimum quantities depend on the specific section required — share your drawing and we will confirm feasibility and quantity.
Q: How do you handle theoretical weight versus actual weight discrepancies?
A: We produce to ±1% tolerance on wall thickness per GB/T 6728 and EN 10219 standards. Each bundle is weighed and documented, and the mill test certificate states actual measured values alongside theoretical calculations.
Q: Do you supply both raw tubes and fabricated components?
A: Yes. As an integrated steel producer and fabricator, we supply Q235 square steel tube as raw material and also provide cutting, drilling, welding, and assembly services for finished structural components — all under one quality system.
