Description
Factory-direct pricing with zero middlemen markup — every Q235 square and rectangular steel tube ships from our Jinan production lines at bulk volume rates, backed by original mill test certificates for every heat number.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Square Steel Tube |
| Product Type | Square and Rectangular Steel Tube (Welded) |
| Steel Grade | Q195, Q235, Q345 |
| Standard | ASTM, JIS, DIN |
| Section Shape | Square / Rectangular |
| Size Range | 100×100 mm – 500×500 mm |
| Wall Thickness | 0.5 – 30 mm |
| Length | 6 – 12 m |
| Technique | Hot Rolled / Cold Rolled, Welded |
| Surface Treatment | Hot Rolled, Oiled or Non-oiled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures, Construction frames, Machinery, Scaffolding, Furniture, Bridges, Shipbuilding, Roofing |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, scaffolding systems, roofing purlins, column supports |
| Industrial & Machinery | Equipment base frames, conveyor structures, machine guards |
| Energy & Transport | Bridge component assemblies, shipbuilding structural members |
| Commercial Structures | Furniture frameworks, display rack supports, warehouse mezzanines |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a 10 mm wall means the difference between passing structural inspection and scrapping an entire container at the port.
I watched a 300×300 ASTM A500 shipment get held at Dubai customs because the third-party inspector pulled calipers and found 8.5 mm walls where the paperwork said 10 mm. The buyer had already paid freight. The steel sat in a bonded warehouse for six weeks before anyone figured out how to resolve it. When you source an ASTM Q235 square and rectangular steel tube supplier who treats tolerance as a suggestion rather than a specification, that is the kind of bill that shows up — not on the invoice, but at the job site. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Q235 Tubes to Structural Frame Loads
Q235 sits in the sweet spot for general construction framing — it delivers adequate yield strength for building columns, scaffolding uprights, and warehouse mezzanine beams without the premium that higher grades command. The 100×100 to 500×500 mm range covers most standard frame node sizes, while the 0.5–30 mm wall thickness band lets engineers dial in weight versus load capacity. Our production lines run hot rolled and cold rolled welded processes side by side, so a procurement team can spec hot rolled for heavy structural members and cold rolled for lighter furniture-grade frames — all under one ASTM Q235 square and rectangular steel tube supplier contract, consolidated into shared containers.
Engineering Compliance and Certification Requirements
Structural steel tubes destined for EU markets must conform to EN 10210 (hot finished) or EN 10219 (cold formed) dimensional and chemical requirements; North American projects typically call for ASTM A500 Grade B or C. Q235 maps closely to S235JR in the EN system, and we supply mill test certificates documenting chemical composition and mechanical test results per the relevant standard for each order. For projects requiring CE marking, our tubes carry Lloyd’s CE certification under EN 10210/10219, which clears customs across EU member states without additional testing delays. [NEED_CITE: steel grade equivalence between Chinese GB and European EN standards] Plain ends come ready for on-site welding or mechanical connection, and we offer custom cutting to project-specific lengths to reduce field waste.
Understanding Q235 Steel Grade and Welded Tube Manufacturing
Q235 is a carbon structural steel defined under Chinese GB/T 700, with a minimum yield strength that positions it between basic mild steel and higher-strength low-alloy grades like Q345. In the ASTM framework, Q235 performs comparably to A36 for general structural use, while Q345 aligns more closely with A572 Grade 50 — giving procurement teams a clear upgrade path within the same product family. Our welded tube process forms coiled or plate steel through progressive roll forming into square or rectangular profiles, then applies continuous or intermittent welding along the seam. Hot rolled tubes undergo forming at elevated temperatures, which produces a scaled surface suited to structural applications where appearance is secondary; cold rolled tubes are formed at ambient temperature from pickled coil, yielding tighter dimensional accuracy and a cleaner surface for visible architectural elements. The oiled surface treatment option provides short-term corrosion protection during ocean transit, while non-oiled finishes serve indoor or immediately painted applications.
Hidden Costs of Sourcing Without Verified Mill Certificates
When a supplier ships Q235 tubes without original mill test certificates, the buyer inherits every risk that certificate was meant to prevent: chemical composition that does not match the specified grade, wall thickness that falls below minimum tolerance, and no heat number traceability if a structural member fails inspection. Customs authorities in the EU, Middle East, and Southeast Asia increasingly require CE documentation or third-party inspection reports before releasing steel shipments — arriving without them means bonded warehouse fees, demurrage charges, and in some cases forced re-export. [NEED_CITE: customs documentation requirements for structural steel imports in EU and GCC countries] The cost of requesting an SGS or BV inspection before shipment is a fraction of what a rejected container costs in port storage and reshipping.
Why Procurement Teams Choose Our Production Lines
We run three welded tube production lines simultaneously in Jinan, giving us the capacity to fill a 20-ton order for 200×200 Q235 tubes while simultaneously running a separate heat of 400×400 Q345 rectangular tubes for another client — all from the same facility, with shared logistics coordination. Every bundle leaving our yard carries an original mill test certificate tied to a specific heat number, and our in-house lab performs three-stage inspection covering dimensional checks, weld seam integrity, and surface quality before any tube reaches the loading bay. Our inventory covers over 2,800 standard specifications across square, rectangular, and round profiles, which means trial orders as small as 1 ton can ship from ready stock while full-container bulk orders move into production within typical lead times. We handle export documentation, customs clearance paperwork, and container loading optimization as a standard part of the order — not as an add-on service.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition (C, Mn, Si, S, P) and tensile test results per GB/T 700, with heat number traceability for every bundle
- CE certificate issued by Lloyd’s Register confirming compliance with EN 10210 and EN 10219 for hot finished and cold formed hollow sections
- ISO 9001:2015 quality management system certificate covering the full production and inspection process
- SGS or BV third-party inspection report available on request, covering dimensional verification, visual weld inspection, and material testing
- Material traceability by heat number stamped on each tube and cross-referenced to the mill test certificate
- Full customs documentation package including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Q235 welded tubes bundled with steel strip bands and edge protectors to prevent surface damage during handling and ocean transit
- Oiled surface treatment applied before bundling to provide rust inhibition for the typical sea freight duration
- Container loading plans optimized for 6 m and 12 m lengths to maximize payload per 20ft or 40ft container, reducing per-ton freight cost
- Custom cutting to project-specified lengths available before shipment, with cut ends deburred and marked with heat number and steel grade
- Each bundle tagged with identification labels showing steel grade (Q195/Q235/Q345), section size, wall thickness, length, and heat number
- FOB, CIF, and DDP shipping terms available with professional export coordination from Jinan to destination port
Getting Your Quotation and Mill Documentation
Submit your required section dimensions, wall thickness, steel grade, total tonnage, and destination port — we respond within 12 hours with bulk pricing, available stock status or production lead time, and the certification package included with your order. For non-standard sizes outside the 100×100 to 500×500 mm range, share your drawing or specification sheet and we will confirm feasibility and tooling requirements.
Start Your Q235 Tube Procurement
Send your specifications to admin@sdxinjiyuan.com or message us on WhatsApp at +86 188 5315 7756 to receive a quotation and sample mill test certificate within one business day.
Frequently Asked Questions
Q: How does Q235 compare to ASTM A500 or S235JR for structural applications?
A: Q235 falls within the same general-purpose carbon structural steel category as ASTM A36 and EN S235JR. For most building frame, scaffolding, and general machinery applications, these grades are functionally interchangeable. We supply mill test certificates that document the specific chemical and mechanical results for your heat, so your engineer can verify compliance with the calling standard.
Q: Can you provide third-party inspection before shipment?
A: Yes. SGS and BV inspection reports are available on request for any order. The inspection covers dimensional verification, visual weld quality, surface condition, and material testing. The report is issued independently by the inspection agency and accompanies your shipment documentation.
Q: What is the minimum order quantity for Q235 square and rectangular tubes?
A: Our standard MOQ is 5 tons for production orders. For trial orders or urgent requirements, we can supply from ready stock starting at 1 ton, depending on the specific size and availability at the time of inquiry.
Q: Do you supply non-standard sizes outside the 100×100 to 500×500 mm range?
A: Our inventory covers over 2,800 specifications. If your project requires a size outside the standard range listed, share your specification and we will confirm whether it can be produced on our existing tooling or if a custom roll setup is needed.
Q: What certifications do you provide for EU customs clearance?
A: Every shipment can be accompanied by a CE certificate issued under EN 10210 (hot finished) or EN 10219 (cold formed), along with original mill test certificates and ISO 9001:2015 quality system documentation. This package satisfies customs requirements across EU member states.
