Description
Factory-Direct Q235 Tube Supply — Every batch priced from our Jinan mill with original mill test certificates attached before container sealing.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Customised Square Steel Tube and Rectangular Metal Pipe |
| Product Type | Square / Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q235 |
| Standard | ASTM |
| Section Shape | Square |
| Size Range | Outer Diameter 10–100 mm |
| Technique | Welded (ERW) |
| Surface Treatment | Hot Rolled (Black) |
| Tolerance | ±1% |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Delivery Time | 8–14 days |
| Invoicing | By Actual Weight |
| Application | Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Steel Structures, Construction Frames, Machinery |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, scaffolding uprights, roof truss members |
| Industrial Piping | Fluid transport lines, gas distribution headers, hydraulic manifolds |
| Machinery Manufacturing | Equipment base frames, conveyor support structures, drill rig columns |
| Energy & Utilities | Boiler support tubes, solar mounting structures |
What Negative Tolerance Costs When You Invoice by Theory
Invoicing by actual weight eliminates the hidden surcharge built into theoretical-weight billing.
I once shipped a container of Q235 square tubes to a Ho Chi Minh City warehouse project. The consignee weighed the entire lot at port and found nearly one ton short against the invoice. The wall thickness had been rolled to the extreme negative end of tolerance — technically within spec, but the buyer was paying for steel that never arrived. He pulled a caliper and measured every single piece. That kind of friction destroys repeat business. When a Q235 customised square steel tube supplier invoices by actual weight, both sides see the same number on the scale and the same number on the invoice. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
Matching Structural Frames and Machinery Bases to Q235 ERW Welded Tubes
Q235 ERW welded square tubes in the 10–100 mm outer diameter range sit at the intersection of light structural framing and machinery support. The hot rolled black surface accepts shop primer or galvanizing after fabrication, so procurement teams can order raw tubes, let the fabricator cut, punch, and bend to drawing, then finish on-site. For a Q235 customised square steel tube supplier running three production lines, the ±1% tolerance holds consistently across small-batch trial orders and full-container loads alike.
Engineering Compliance and Certification Pathways
Structural frames carrying vertical and lateral loads must satisfy the governing building code — EN 1993 in Europe, AISC in North America, or local equivalents in Southeast Asia and the Middle East. Q235 maps broadly to S235JR in the EN system and roughly to ASTM A500 Grade B in the US system, though exact equivalence depends on chemical composition and elongation requirements that vary by standard edition [NEED_CITE: steel grade equivalence mapping between GB Q series and EN S series]. For projects requiring CE marking under EN 10210 or EN 10219, the mill test certificate must document heat-by-heat chemistry and mechanical results. Customs authorities in the EU and GCC increasingly reject shipments lacking traceable mill certificates, turning a pricing win into a port-side demurrage bill. [NEED_CITE: CE marking requirements for structural hollow sections under EN 10210]
Understanding Q235 Steel Grade and ERW Welding Process
Q235 is a Chinese carbon structural steel with a minimum yield strength of 235 MPa, widely specified across domestic infrastructure and exported as a cost-effective alternative to S235JR or A36. In the ERW (Electric Resistance Welding) process, a steel strip is cold-formed into a square or rectangular profile and the longitudinal seam is fusion-welded under pressure without filler metal. ERW tubes offer tighter dimensional accuracy and smoother surface finish compared to SSAW, at lower cost than seamless — making them the default choice for structural frames, furniture, and low-to-medium pressure fluid conveyance. The hot rolled black surface retains a mill scale layer that provides short-term rust resistance during storage and transit but requires removal before painting or galvanizing. Wall thickness tolerance of ±1% means a 3.0 mm nominal wall measures between 2.97 mm and 3.03 mm — tight enough to keep structural calculations reliable without inflating weight-based pricing.
The Hidden Cost of Unverified Wall Thickness and Missing Certificates
Ordering structural tubes without independent verification invites three failure modes: wall thickness at the extreme negative tolerance reduces load-bearing capacity below design assumptions; missing or forged mill certificates trigger customs holds and project rejection; and mixed heat numbers in a single bundle create inconsistent weldability during fabrication. Engineering inspectors referencing EN 10219 or ASTM A500 will reject entire shipments if even one test piece fails chemistry or tensile requirements. [NEED_CITE: consequences of non-compliant hollow sections in structural applications]
Why Global Buyers Source Q235 Tubes From Our Jinan Mill
We run three ERW production lines in Jinan producing over 2,800 stock specifications, so standard sizes ship from ready inventory while custom lengths and non-standard dimensions roll within typical production lead times. Every heat carries an original mill test certificate generated by our in-house理化实验室, and we welcome SGS or BV third-party inspection at the factory before container loading. Our export team consolidates multi-product orders — square tubes, rectangular tubes, H-beams, plates — into single containers with optimized loading plans that maximize weight utilization and minimize ocean freight cost per ton. Volume buyers trading above $500K annually receive tiered pricing reviews every six months, and our documentation package covers commercial invoice, packing list, bill of lading, and certificate of origin formatted for the destination country’s customs requirements.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition (C, Si, Mn, P, S) and mechanical properties (yield strength, tensile strength, elongation) per heat number
- CE certificate covering EN 10210 hot-finished and EN 10219 cold-formed structural hollow sections for EU market access
- ISO 9001:2015 quality management certificate covering the full production and inspection workflow
- SGS or BV third-party inspection report available upon request, covering dimensional checks, visual examination, and witness testing
- Material traceability linking every tube to its heat number, rolling date, and test certificate
- Customs documentation package including packing list, bill of lading, certificate of origin, and fumigation certificate where required
Packaging, Loading & Delivery
- Q235 hot rolled black square and rectangular tubes bundled with steel strips and padded at contact points to prevent surface scoring during transit
- Bundles sized to match the 10–100 mm outer diameter range, with outer diameter and wall thickness stenciled on each bundle tag alongside heat number
- Container loading plans optimized for 20ft and 40ft containers, nesting smaller square tubes inside larger rectangular profiles to maximize weight per container
- Custom cutting to fixed lengths available before shipment, with cut ends deburred and bundled separately for fabrication-ready delivery
- Ocean freight FOB Jinan/Qingdao or CIF to destination port, with door-to-door DDP options available for project sites requiring inland delivery
Requesting a Quote With Mill Test Certificates
Submit your specification sheet — outer diameter, wall thickness, length, quantity, steel grade, and destination port — and receive a bulk quotation with volume-based pricing within 12 hours. We attach sample mill test certificates for the relevant Q235 heat before you commit to a deposit, so your engineering team can verify chemistry and mechanical properties against project requirements. For custom processing including bending, punching, or cutting to drawing dimensions, share the fabrication drawing and we return a processed-price quote alongside raw tube pricing.
Frequently Asked Questions
Q: What is the difference between Q235 and ASTM A500 steel grades?
A: Q235 is a Chinese carbon structural steel grade with 235 MPa minimum yield strength, commonly used as a cost-effective alternative to S235JR in EN standards or ASTM A500 Grade B. Chemical composition and elongation requirements differ slightly between standards, so projects specifying ASTM A500 should confirm equivalence with their engineer before substituting Q235.
Q: Can you provide third-party inspection certificates for customs clearance?
A: Yes, we arrange SGS or BV inspection at our factory before container loading. The inspection covers dimensional verification, visual examination, and witness testing, with the report issued directly to the buyer for customs and project compliance.
Q: What is the MOQ for customised square and rectangular tubes?
A: Trial orders start from 1 ton, allowing buyers to test material quality and fabrication compatibility before committing to full-container bulk orders. Standard sizes ship from ready stock, while custom dimensions and processing require typical production lead times.
Q: How do you handle non-standard sizes and special processing requirements?
A: Our three production lines cover over 2,800 specifications in stock, and we roll custom outer diameters, wall thicknesses, and lengths to drawing. Processing services include welding, punching, cutting, and bending — share your fabrication drawing and we return a processed-price quote.
Q: What is the delivery time for bulk orders and container loading optimization?
A: Standard sizes ship within 8–14 days from ready inventory. Custom orders and processed tubes follow typical production lead times, with our export team optimizing container loading to maximize weight utilization and minimize freight cost per ton.
Get Your Q235 Tube Quote With Mill Certificates Today
Send your specification sheet and destination port to receive bulk pricing and sample mill test certificates within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
