Description
Factory-direct welded square rectangular steel tube supply — every batch leaves our Jinan mill with original test certificates and verified wall-thickness measurements before container sealing.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and 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 | 20 mm, 40 mm, 60 mm, 80 mm and other customized sizes |
| Wall Thickness | 0.8–30 mm |
| Length | 100 mm–11,800 mm (customizable) |
| Technique | Welded (ERW) |
| Surface Treatment | Pre-galvanized / Hot-dipped galvanized / Bare / Oiled / Black original steel |
| Tolerance | ±1% |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By theoretical weight |
| Application | Structure pipe, Steel fence, Steel post, Steel construction, Warehouse construction, Building construction |
| MOQ | 10 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Warehouse & Industrial Construction | Portal frame columns, roof purlin bracing, mezzanine support posts |
| Infrastructure & Civil Engineering | Highway guardrail posts, sound barrier frames, lighting pole bases |
| Building Construction | Load-bearing columns, curtain wall sub-frames, stair handrail structures |
| Agricultural & Commercial Structures | Greenhouse framing, equipment shed frames, livestock fencing posts |
What Wall-Thickness Deviation Costs on a Welded Square Rectangular Steel Tube Order
A 0.2 mm shortfall on a 2.0 mm wall tube drops theoretical weight by nearly 10% — and fails SGS inspection on arrival.
I watched a 40×40×2.0 black square tube shipment get rejected at a Ho Chi Minh City job site because a caliper check showed walls consistently below 1.6 mm. The entire container sat at the port for over two weeks while the buyer arranged replacement cargo — and the return freight cost more than the tubes themselves. This is not an isolated incident. Global buyers of welded square and rectangular steel tubes routinely face quality uncertainty when suppliers ship under-tolerance material without declaration, leaving structural engineers unable to verify load-bearing compliance on site. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed welded hollow sections]
Matching Structural Load Paths in Warehouse and Fence Construction
When engineers specify Q235 or Q345 welded square rectangular steel tube for warehouse portal frames or perimeter fencing, the ERW weld seam must run continuously along the full length without porosity or incomplete fusion — otherwise the tube fails at connection nodes under cyclic wind loading. Our production lines run simultaneous welding passes with inline seam inspection, so every Q345 tube shipped for steel construction meets the same weld integrity standard regardless of order volume. For fence post applications where corrosion resistance matters more than ultimate strength, pre-galvanized Q235 tubes provide adequate zinc coverage at lower cost than hot-dipped alternatives.
Engineering Compliance and Surface Treatment Selection
Structural frames for warehouse construction must comply with load-bearing codes that reference specific steel grades — Q235 maps to S235 in European standards, while Q345 aligns with S355 in yield strength classification. [NEED_CITE: steel grade equivalence between GB/T 700 and EN 10025 standards] Choosing between bare, pre-galvanized, or hot-dipped galvanized finish depends on the exposure environment: bare or oiled tubes suit indoor structural applications where painting follows on site, while hot-dipped galvanizing is necessary for outdoor fence posts and coastal construction where salt spray accelerates corrosion. Every batch of welded square rectangular steel tube ships with CE certification under EN 10210/10219 for European project compliance, and original mill test certificates that customs authorities require for clearance. [NEED_CITE: CE marking requirements for structural hollow sections under EN 10219]
Steel Grade Selection and ERW Welding Process
The Q-series grades (Q195 through Q345) follow the Chinese GB/T 700 classification system where the number indicates minimum yield strength in MPa — Q235 delivers 235 MPa yield, making it the default choice for general structural framing, while Q345 provides higher strength for heavier load paths in warehouse construction. The S-series (S235, S355) follows EN 10025 and is specified on European projects; GR.A and GR.B serve shipbuilding and marine applications. ERW welding produces a longitudinal seam by passing current through the tube edges under pressure — it is cost-effective for square and rectangular sections in the 20 mm to 80 mm size range with wall thickness up to 30 mm, and delivers consistent dimensional accuracy at ±1% tolerance. Pre-galvanized coating applies zinc before forming, providing uniform coverage on all surfaces including the weld zone, while hot-dipped galvanizing coats the finished tube for maximum corrosion protection in aggressive environments.
Hidden Costs of Procuring Without Verified Traceability
Ordering welded square rectangular steel tube from unverified suppliers may save a few dollars per ton upfront, but the downstream costs multiply quickly. Material that arrives without original mill test certificates cannot pass customs inspection in markets requiring CE or ISO documentation — the container gets held at port, demurrage charges accumulate, and the project timeline slips. Tubes with undeclared negative tolerance may pass visual inspection but fail structural load testing, forcing complete frame replacement after erection. Welded square rectangular steel tube sourced without third-party verification also creates liability exposure: if a structural member fails and the material cannot be traced to a certified heat number, the buyer bears full responsibility for the engineering consequence. [NEED_CITE: material traceability requirements under EN 10204 inspection certificate types]
Why Buyers Choose Xin Jiyuan for Welded Square Rectangular Steel Tube
We operate three production lines in Jinan running simultaneously, producing over 20,000 tons monthly across 2,800+ specifications — this means your Q345 welded square rectangular steel tube order ships from factory stock or enters production within days, not weeks. Every tube leaving our mill passes through a three-stage in-house inspection covering dimensional accuracy, weld seam integrity, and surface finish quality before packaging. We provide original mill test certificates with every shipment documenting chemical composition and mechanical properties per heat number, and we arrange SGS or BV third-party inspection on request for buyers who need independent verification. Our export team handles complete documentation including CE certificates under EN 10210/10219, packing lists, bills of lading, and certificates of origin — eliminating the paperwork gaps that cause customs delays. For long-term partners, we offer volume-based pricing programs with factory-direct rates and no middleman markup, plus consolidated container loading when your project requires mixed specifications across pipes, plates, and sections.
Documentation & Compliance
- Mill test certificate documenting Q235 and Q345 chemical composition, yield strength, and tensile properties per heat number
- CE certificate under EN 10210 (hot-finished) and EN 10219 (cold-formed welded hollow sections) for European project compliance
- ISO 9001:2015 quality management certificate covering the full production and inspection process
- SGS or BV third-party inspection report available on request for independent material verification
- Full material traceability from heat number through production batch to final shipment documentation
- Complete customs document package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235 and Q345 welded square rectangular steel tube bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Pre-galvanized and hot-dipped galvanized tubes wrapped with waterproof cloth to preserve zinc coating integrity in humid shipping conditions
- Bare and oiled tubes bundled by size and length for efficient container loading optimization across 20 ft and 40 ft units
- Custom cut-to-length service available within the 100 mm–11,800 mm range, with each bundle labeled by heat number, steel grade, and dimensions
- Professional container loading plans maximizing payload for 10-ton MOQ orders while maintaining weight distribution for safe transport
- FOB, CIF, and door-to-door delivery options with real-time shipment tracking from Jinan port to destination
Starting Your Welded Square Rectangular Steel Tube Procurement
Send your specification sheet covering section dimensions, wall thickness, steel grade, surface treatment, quantity, and destination port — our team responds within 12 hours with a competitive bulk quotation including volume pricing, delivery timeline, and payment terms. For non-standard sizes or custom lengths outside the standard range, we provide fabrication feasibility feedback and lead time estimates before you commit.
Request Your Factory-Direct Quotation with Mill Test Certificates
Submit your welded square rectangular steel tube specifications and receive a detailed quotation with original mill test certificate samples, SGS/BV inspection options, and optimized container loading plans — contact us at admin@sdxinjiyuan.com or WhatsApp +86 188 5315 7756.
Frequently Asked Questions
Q: How do Q235 and Q345 steel grades compare to S235 and S355 for European projects?
A: Q235 and S235 share equivalent minimum yield strength at 235 MPa, while Q345 and S355 both deliver 355 MPa yield strength. For European projects requiring CE certification under EN 10219, we supply S235 and S355 grades with full EN-compliant documentation.
Q: Can you provide mill test certificates for customs clearance?
A: Yes, every batch of welded square rectangular steel tube ships with original mill test certificates documenting chemical composition and mechanical properties per heat number. We also arrange SGS or BV third-party inspection reports for buyers who need independent verification.
Q: What is the minimum order quantity for custom sizes?
A: Our MOQ is 10 tons, and we support custom lengths within the 100 mm–11,800 mm range as well as non-standard section sizes. Trial orders are accepted for new buyers evaluating material quality.
Q: What is the difference between pre-galvanized and hot-dipped galvanized finish?
A: Pre-galvanized coating is applied to the steel strip before tube forming, providing uniform zinc coverage including the weld zone at lower cost. Hot-dipped galvanizing coats the finished tube in a zinc bath, delivering thicker coating for superior corrosion resistance in outdoor or coastal environments.
Q: Do you provide CE certification for European construction projects?
A: Yes, our welded square rectangular steel tube carries CE certification under EN 10210 and EN 10219 standards, with full documentation including mill test certificates and third-party inspection reports available for EU customs clearance.
