Description
Factory-direct pricing with no middlemen — Every Q235 Q345 ERW welded square rectangular steel tube factory direct supplier order ships from our own production lines in Jinan, eliminating trading margins and ensuring mill-level quality control from raw coil to final bundle.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (ERW) |
| Steel Grade | Q195, Q215, Q235, Q345 |
| Standard | ASTM A213, DIN EN 10217-1 |
| Section Shape | Square / Rectangular |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Slightly Oiled |
| Tolerance | ±1% |
| Length | 6m / 6.4m / 12m (customizable per request) |
| Ends | Plain (default) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Application | Fluid Pipe, Boiler Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Construction | Structural frames, building columns, scaffolding systems for industrial warehouses and commercial buildings |
| Machinery Manufacturers | Equipment base frames, conveyor support structures, automation system housings |
| Infrastructure & Civil Engineering | Bridge handrails, sound barrier posts, highway sign gantry supports |
| Fluid & Gas Transport | Low-pressure water supply lines, gas distribution networks, chemical fertilizer pipeline systems |
What Negative Tolerance Costs on a Structural Frame Order
A 0.8mm wall deviation on a 6mm tube can void an entire project inspection.
I have seen containers of square tubes rejected at destination ports because the actual wall thickness fell below the minimum allowed by EN 10219. The mill ran heavy negative tolerance, the third-party inspector measured it at the quay, and the client faced weeks of delay plus re-shipment costs. When you source a Q235 Q345 ERW welded square rectangular steel tube factory direct supplier, dimensional consistency matters more than unit price savings. Inconsistent wall thickness creates weak weld joints, unpredictable load-bearing capacity, and failed structural calculations — especially on sharp-corner rectangular tubes where forming stress concentrates at the corners [NEED_CITE: EN 10219 cold-formed structural hollow sections dimensional tolerance requirements].
How ERW Welded Square and Rectangular Tubes Match Structural Engineering Demands
Electric resistance welding produces a continuous longitudinal seam with minimal heat-affected zone, making Q235 and Q345 ERW tubes suitable for load-bearing frames where weld integrity directly affects structural safety. The ±1% tolerance on our production lines ensures that 150×150×6mm tubes arrive at your site within spec — critical when bolted connections depend on precise outer dimensions. For EPC contractors building warehouse structures across Southeast Asia, we supply 12m fixed lengths that reduce on-site cutting waste and accelerate erection schedules.
Engineering Compliance and Certification Requirements Across Markets
Structural hollow sections used in load-bearing applications must comply with regional codes — EN 10210/EN 10219 for European projects, ASTM A500 for North American specifications, and JIS G3466 for Japanese-standard construction [NEED_CITE: steel grade equivalence between Chinese GB standards and international EN/ASTM standards]. Our Q235 Q345 ERW welded square rectangular steel tube factory direct supplier output carries CE certification under EN 10210/EN 10219, enabling direct customs clearance into EU member states without additional testing. For corrosive environments, we offer hot-rolled finish with slight oiling as standard, with galvanized or painted options available upon request.
Steel Grade Selection and ERW Process Fundamentals
Q235 and Q345 represent the two most widely specified carbon structural grades in Chinese steel production — Q235 offers good formability and weldability for general structural use, while Q345 provides higher yield strength for applications requiring greater load capacity. The ERW process uses high-frequency current to heat and forge the tube seam without filler metal, producing a weld zone with mechanical properties closely matching the parent material. Wall thickness up to 40mm is achievable on our dedicated production lines, covering both thin-walled sections for non-structural cladding supports and heavy-walled tubes for primary structural members. Our proprietary sharp-corner rectangular tube technology — one of 41 patented processes — achieves tight internal corner radii that improve connection fit-up and aesthetic finish for architectural applications.
Hidden Costs of Sourcing Without Verified Mill Documentation
Purchasing steel tubes without traceable mill test certificates creates compounding risks: customs authorities in the EU and Middle East increasingly demand EN 10219 or ASTM A500 compliance documentation, and shipments without proper certification face detention or rejection [NEED_CITE: customs documentation requirements for structural steel imports into EU markets]. Material substitution — receiving Q195 when Q345 was specified — may pass visual inspection but fails under structural load testing, forcing costly rework after erection has begun. Negative tolerance abuse reduces actual weight per meter below theoretical calculations, creating safety margins that engineers never approved.
Procurement Confidence Through Direct Factory Control
As a Q235 Q345 ERW welded square rectangular steel tube factory direct supplier, we operate three dedicated production lines with in-house physical and chemical laboratories conducting incoming, in-process, and final inspections on every heat. Every bundle carries traceable heat numbers linked to original mill test certificates. Our 2,800+ specification range covers square tubes from 10×10mm to 500×500mm and rectangular tubes up to 600×400mm, with wall thickness from 0.5mm to 40mm — reducing fragmented sourcing across multiple vendors. Custom non-standard sizes, pre-cut lengths, and punched or bent processing are available with typical production lead times, not the extended waits common at trading companies. Professional loading plans optimize container utilization for 6m and 12m lengths, and we coordinate door-to-door logistics to 50+ countries with real-time shipment tracking.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345 chemical composition and mechanical properties per ASTM A213 and DIN EN 10217-1, traceable to original heat number
- CE certificate confirming compliance with EN 10210/EN 10219 for structural hollow sections, required for EU market customs clearance
- ISO 9001:2015 quality management system certificate covering full production process from raw material inspection to final dimensional verification
- SGS or BV third-party inspection reports available upon request for projects requiring independent quality verification at loading port
- Material traceability documentation linking each bundle to specific heat numbers, production dates, and test results
- Complete customs document package including packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- Q235/Q345 ERW welded square rectangular steel tubes bundled with high-tensile steel strips at minimum three points per bundle, preventing shift during ocean transit
- Hot-rolled and slightly oiled surface treatment preserved through waterproof wrapping and edge protectors on sharp-corner rectangular tubes
- Container loading plans optimized for 6m and 12m lengths, maximizing 20ft and 40ft GP utilization for structural tube shipments
- Custom cut-to-length service available for 6.4m and non-standard sizes, reducing on-site waste for EPC project sites
- Heat number and steel grade stenciled on each tube end for site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional coordination to ports across EU, North America, Southeast Asia, Middle East, and 50+ countries
Start Your Procurement With Verified Specifications
Submit your detailed requirements — including section dimensions, wall thickness, steel grade, total quantity, and destination port — and receive a comprehensive quotation within 12 hours, complete with mill test certificate samples and certification documentation. For non-standard dimensions or sharp-corner rectangular tubes, our technical team provides custom feasibility assessment and production scheduling confirmation before contract signing.
Request Your Q235 Q345 ERW Welded Square Rectangular Steel Tube Factory Direct Supplier Quotation
Send your specifications to admin@sdxjysteel.com or contact us via WhatsApp at +86 188 5315 7756 for immediate technical consultation and pricing.
Frequently Asked Questions
Q: How do Q235 and Q345 steel grades compare to international standards like ASTM A500 or EN 10210?
A: Q235 and Q345 are Chinese structural carbon steel grades with chemical composition and mechanical properties that correspond to international equivalents. Q235 generally aligns with ASTM A252 Grade 2 or S235JR in EN standards, while Q345 corresponds to ASTM A500 Grade B or S355JR/S355J2 in EN standards. We provide detailed grade equivalence documentation with every shipment to support engineering approval and customs clearance.
Q: Can you provide mill test certificates and arrange third-party inspection for our project?
A: Yes, every shipment includes original mill test certificates documenting chemical composition and mechanical properties, traceable to specific heat numbers. We also accommodate SGS, BV, or other internationally recognized third-party inspection agencies at our facility before shipment, with inspection reports included in the documentation package.
Q: What is the minimum order quantity for custom non-standard sizes and sharp-corner rectangular tubes?
A: The standard MOQ is 5 tons for regular stock specifications. For custom non-standard dimensions or proprietary sharp-corner rectangular tubes, MOQ depends on the specific size and production setup requirements — our technical team provides exact quantities during the quotation stage based on your detailed specifications.
Q: What surface treatment options are available for different environmental conditions?
A: Standard delivery is hot-rolled with slight oiling for general indoor or protected applications. For outdoor or corrosive environments, we offer hot-dip galvanizing, painted coatings, or specialized anti-corrosion treatments. Surface treatment selection depends on your project’s environmental exposure and design specifications.
Q: Do your CE certificates comply with EN 10210/EN 10219 for European market import?
A: Yes, our CE certification under Lloyd’s Register covers EN 10210 (hot-finished structural hollow sections) and EN 10219 (cold-formed welded structural hollow sections), meeting all requirements for structural steel imports into European Union member states. We also hold Singapore FPC certification for Southeast Asian projects.
