Description
Factory-direct pricing with no middlemen — As a manufacturer with 3 dedicated production lines and in-house quality control, we supply Q195-Q345 welded square rectangular steel tube directly to your project site, eliminating distributor markups on every ton.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195/Q235/Q345 Welded Square / Rectangular Steel Tube |
| Product Type | Welded Square / Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, GR.A, GR.B, S235, S355 |
| Standard | ASTM A213, DIN EN 10217-1 |
| Section Shape | Square / Rectangular |
| Size Range | Customized (OEM/ODM) |
| Wall Thickness | 0.8–30 mm |
| Length | 500 mm / 1000 mm / 4000 mm / 5800 mm / 11800 mm (customizable) |
| Technique | ERW (Welded) |
| Surface Treatment | Pre-galvanized / Hot-dipped galvanized / Bare / Oiled / Black original |
| Tolerance | ±1% |
| Ends | Plain / Beveled (per requirement) |
| Application | Steel structures, Steel fences, Steel posts, Warehouse construction, Building construction |
| MOQ | 10 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Warehouse frames, industrial building columns, portal steel structures |
| Construction Companies | Steel fences, post supports, infrastructure boundary markers |
| Steel Structure Fabricators | Beam-to-column connections, bracing members, mezzanine floor supports |
| Machinery Manufacturers | Equipment base frames, conveyor support structures, machine guards |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on 0.8–30 mm wall thickness determines whether your frame passes load calculation or fails inspection.
When a 6 mm Q235 welded square rectangular steel tube arrives at site with actual wall thickness measuring 5.2 mm, the structural engineer recalculates the moment of inertia and discovers the member cannot carry the design load. The entire batch gets rejected. I have seen containers held at port for three weeks because the mill test certificate showed yield strength values that did not match the physical samples tested by the site laboratory. Material traceability by heat number is not optional — it is the difference between customs clearance and return shipment. [NEED_CITE: EN 10219 cold-formed hollow section requirements]
How ERW Welded Tubes Match Structural Frame Requirements
The ERW welding process produces a continuous longitudinal seam that runs the full length of each Q235 Q345 welded square rectangular steel tube, creating a closed section with uniform torsional resistance. For warehouse frames and building columns, this means predictable deflection behavior under vertical and lateral loads. The ±1% wall thickness tolerance ensures that section modulus calculations remain valid across the entire batch, while the 0.8–30 mm range covers everything from light gauge fence posts to heavy-duty industrial column members. Our in-house physical and chemical laboratory tests every heat before the tube leaves the mill, so the MTC you receive matches the material in your container.
Structural Code Compliance and Corrosion Environment Selection
Load-bearing structures in the EU must conform to EN 1993 design rules, which reference EN 10219 for cold-formed welded hollow sections. [NEED_CITE: steel grade equivalence between EN and ASTM standards] The Q235 grade maps approximately to S235 in the EN system, while Q345 corresponds to S355 — both available in our production range with CE certification under EN 10210/EN 10219 for European market compliance. For outdoor applications such as steel fences and infrastructure posts, hot-dipped galvanized coating provides decades of corrosion protection without maintenance, while pre-galvanized or oiled finishes suit indoor warehouse construction where appearance and cost matter more than atmospheric exposure. Custom cut-to-length services at 500 mm to 11800 mm eliminate secondary cutting on site, reducing labor costs and material waste.
Steel Grade Selection and ERW Process Fundamentals
Q195 and Q215 are low-carbon mild steels with excellent formability, suitable for light structural applications where welding and bending are required. Q235 offers higher yield strength for general building construction, while Q345 provides increased load capacity for heavy industrial frames and crane runway beams. The GR.A and GR.B grades meet ship classification society rules for marine and offshore structures. ERW welding uses high-frequency current to fuse the steel strip edges without filler metal, producing a weld seam that matches the base metal strength when properly controlled. Our 3 dedicated production lines cover over 2,800 specifications in square and rectangular sections, with wall thickness up to 30 mm and proprietary sharp-corner rectangular tube technology that achieves tight radius corners for improved connection fit-up and aesthetic appearance. Surface treatment selection depends on the service environment: bare or black original tubes receive field-applied paint systems, pre-galvanized coatings suit moderate corrosion conditions, and hot-dipped galvanizing provides the thickest zinc layer for harsh outdoor or industrial atmosphere exposure.
Hidden Costs of Unverified Material and Missing Certification
Purchasing welded square rectangular steel tube without original mill test certificates creates risk at every project stage. Customs authorities in the EU and North America routinely detain shipments lacking proper CE marking or material traceability documentation, causing demurrage charges and schedule delays. [NEED_CITE: third-party inspection requirements for structural steel imports] Negative tolerance exceeding the specified ±1% limit reduces the actual section modulus, forcing structural engineers to reject the material or redesign the connection details — both options cost more than the price difference between verified and unverified suppliers. Weld seam quality in ERW tubes requires ultrasonic testing to detect lack of fusion or inclusions that could propagate cracks under cyclic loading, but many traders skip this inspection to reduce costs.
Why Project Procurement Teams Choose Our Factory
We operate 3 dedicated production lines with in-house physical and chemical laboratories that perform incoming raw material inspection, in-process weld seam testing, and final dimensional verification before shipment. Every Q195-Q345 welded square rectangular steel tube order includes an original mill test certificate documenting chemical composition and mechanical properties per heat number, enabling full material traceability from your project site back to our steel coil supplier. Our product range covers over 2,800 specifications in square and rectangular sections with wall thickness from 0.8 mm to 30 mm, including custom non-standard sizes and proprietary sharp-corner rectangular tube technology that fills gaps in the global market. CE certification under EN 10210/EN 10219, ISO 9001:2015 quality management, and third-party inspection through SGS and BV ensure compliance for projects in the EU, North America, and 50+ countries worldwide. Professional container loading optimization maximizes payload per shipment, while door-to-door logistics coordination handles customs documentation and port clearance so your material arrives on schedule.
Documentation & Compliance
- Mill test certificate documenting Q195/Q235/Q345 chemical composition and mechanical properties per heat number, with original copies for customs clearance
- CE certificate under EN 10210/EN 10219 for cold-formed welded structural hollow sections exported to European Union markets
- ISO 9001:2015 quality management system certificate covering production process and inspection procedures
- SGS or BV third-party inspection report available upon request for projects requiring independent verification
- Material traceability documentation linking each tube to its heat number, steel grade, and production date
- Complete customs document package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q195-Q345 welded square rectangular steel tube bundled with steel strips and edge protectors to prevent coating damage during ocean transit
- Hot-dipped galvanized tubes wrapped with waterproof paper and plastic film to preserve zinc coating surface finish
- Pre-galvanized and bare tubes coated with anti-rust oil before bundling to prevent corrosion during storage and shipping
- Container loading optimization for 5800 mm and 11800 mm lengths maximizes payload per 20ft and 40ft container
- Custom cut-to-length service at 500 mm to 4000 mm reduces on-site cutting waste and labor costs
- Heat number and steel grade stenciled on each bundle for site identification and material traceability
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to 50+ countries
How to Request a Quotation for Your Project
Submit your specification sheet including section dimensions, wall thickness, steel grade, surface treatment, quantity, and destination port. We respond within 12 hours with unit pricing, delivery timeline, payment terms, and applicable certification documents. For custom non-standard sizes or sharp-corner rectangular tubes, our engineering team provides OEM/ODM solutions with detailed drawings for your approval before production begins.
Start Your Procurement Process Today
Send your inquiry via email to admin@sdxjysteel.com or contact us on WhatsApp at +86 188 5315 7756 with your project specifications.
Frequently Asked Questions
Q: How do Q235 and Q345 steel grades compare to S235 and S355 in the EN system?
A: Q235 approximately corresponds to S235JR in the European standard system, while Q345 maps to S355JR/S355J2. Both grade systems specify minimum yield strength values, with Q345/S355 offering higher load capacity for heavy structural applications. We supply both Chinese GB grades and European EN grades from the same production lines with CE certification for EU market compliance.
Q: Can you provide third-party inspection and original mill test certificates for customs clearance?
A: Yes. Every shipment includes original mill test certificates documenting chemical composition and mechanical properties per heat number. We also arrange SGS or BV third-party inspection for projects requiring independent verification. These documents satisfy customs requirements in the EU, North America, and 50+ export destinations.
Q: What is the minimum order quantity for custom non-standard sizes and sharp-corner rectangular tubes?
A: The standard MOQ is 10 tons for regular specifications. For custom non-standard dimensions or proprietary sharp-corner rectangular tubes, MOQ depends on the specific size and production setup. Contact our engineering team with your drawing requirements for a detailed quotation.
Q: Which surface treatment is suitable for outdoor steel fence and post applications?
A: Hot-dipped galvanized coating provides the thickest zinc layer for long-term corrosion protection in outdoor environments, typically lasting 20-50 years without maintenance depending on atmospheric conditions. Pre-galvanized coating suits moderate exposure conditions, while bare or oiled tubes require field-applied paint systems for outdoor use.
Q: Do you offer professional container loading and door-to-door logistics?
A: Yes. Our logistics team optimizes container loading for 5800 mm and 11800 mm tube lengths to maximize payload per shipment. We coordinate FOB, CIF, and DDP shipping terms with complete customs documentation, handling port clearance and door-to-door delivery to your project site in 50+ countries.
Get Factory-Direct Pricing with Full Certification
Email your specification sheet to admin@sdxjysteel.com or WhatsApp +86 188 5315 7756 to receive a detailed quotation with mill test certificate samples within 12 hours.
