Description
Full-Range ERW Square Tube Supply — 2,800+ specifications in stock from 19×19mm to 800×800mm with wall thickness up to 30mm, shipped directly from our Jinan production facility.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q235B, Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square |
| Size Range | 19mm×19mm – 800mm×800mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | ERW / Welded |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Curtain wall framing / Support tubes / Building structures |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Column frames, beam-to-column connections, mezzanine support structures, warehouse roof trusses |
| Facade & Curtain Wall | Vertical mullions, horizontal transoms, architectural exposed framing for glass curtain wall systems |
| Industrial & Machinery | Equipment base frames, conveyor support structures, platform handrails, machine guarding frames |
| Infrastructure | Bridge parapet posts, sound barrier support columns, signage gantry frames |
Where Wall-Thickness Tolerance Decides Structural Acceptance
A ±1% tolerance on a 30mm wall Q235B welded square steel tube means the difference between passing inspector sign-off and full container rejection.
Procurement teams sourcing welded square tubes for structural frames routinely encounter mills pushing negative tolerance to the edge. When wall thickness drops below the specified minimum, the theoretical weight calculation no longer matches actual delivery weight — and structural engineers cannot verify load-bearing capacity without re-testing every piece. On facade projects, inconsistent corner geometry creates visible misalignment in curtain wall framing, forcing field modifications that delay handover. The cost of re-inspection, replacement shipping, and schedule slippage far exceeds the initial price difference between a compliant Q235B welded square steel tube supplier and the cheapest alternative. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
Matching Structural Load Requirements for Building Frames
Q235B welded square steel tubes in the 100×100mm to 400×400mm range with wall thickness 6–20mm serve as primary load-bearing members in multi-story steel frames. The ERW welding process produces a continuous longitudinal seam that maintains uniform strength around the full perimeter — critical when columns experience multi-directional loading. For curtain wall applications, smaller sections from 50×50mm to 150×150mm with 3–8mm walls provide rigid framing for glass panel support while keeping dead load minimal. Our production lines cover the complete range from 19×19mm architectural framing tubes to 800×800mm heavy structural columns, eliminating the need to split orders across multiple suppliers.
Engineering Compliance and Certification Pathways
Structural projects in the EU require CE marking per EN 10219 for cold-formed welded hollow sections, while North American projects specify ASTM A500 Gr.B or Gr.C. Q235B welded square steel tubes produced to GB/T 3091 meet Chinese structural codes, but international projects demand cross-standard equivalence documentation. Our in-house laboratory tests chemical composition and mechanical properties per batch, issuing mill test certificates that satisfy third-party inspectors from SGS or BV. For corrosion-prone environments, galvanized surface treatment provides zinc coating protection extending service life without field painting — essential for coastal infrastructure or industrial facilities with chemical exposure. [NEED_CITE: ASTM A500 versus EN 10219 steel grade equivalence]
Steel Grade Selection and ERW Process Fundamentals
Q235B remains the baseline carbon structural steel in Chinese specifications, offering adequate strength for general building frames at competitive pricing. When projects require higher yield strength, S275 or S355 grades from the EN system provide increased load capacity without increasing section size — reducing overall structure weight. STK400 from JIS G3466 serves Japanese-specification projects requiring proven structural tube performance. The ERW (Electric Resistance Welding) process forms square tubes from slit coil, welding the longitudinal seam under pressure without filler metal — producing consistent wall thickness and smooth interior surfaces suitable for concrete filling in composite columns. Black painted surface treatment provides temporary rust prevention during transit and storage, while galvanized coating offers long-term corrosion resistance for exposed applications. Wall thickness tolerance of ±1% ensures that ordered 10mm wall tubes deliver between 9.9mm and 10.1mm — preventing the negative-tolerance abuse that causes weight discrepancies and structural calculation errors.
Hidden Costs of Non-Compliant Square Tube Procurement
Ordering Q235B welded square steel tubes without verified mill test certificates creates downstream risk: customs authorities in regulated markets may reject shipments lacking proper CE documentation or EN standard references. Wall thickness below specified minimums forces structural engineers to recalculate load capacity — potentially requiring additional bracing or member upsizing that exceeds the original budget. Material substitution without proper documentation voids project warranties and creates liability exposure if structural failure occurs. Third-party inspection before shipment costs a fraction of the expense associated with rejected containers, demurrage charges, and emergency air freight for replacement materials. [NEED_CITE: consequences of missing CE certification for steel imports to EU]
Why Procurement Teams Choose Our Production Facility
Our Jinan factory operates three dedicated ERW lines producing 2,800+ specifications of square and rectangular tubes — covering every size from 19×19mm to 800×800mm with wall thickness up to 30mm. We hold 41 invention patents including China’s original sharp-corner rectangular tube technology, delivering true 90-degree corners for architectural applications where rounded corners create aesthetic and connection problems. Every Q235B welded square steel tube shipment includes mill test certificates from our ISO 9001:2015 certified laboratory, with chemical composition and mechanical properties documented per heat number. Lloyd’s CE certification per EN 10219/10210 and Singapore FPC approval enable customs clearance across EU and Asian regulated markets. Custom non-standard sizes, cut-to-length service, and container loading optimization reduce waste and freight cost — we ship to 50+ countries with professional bundling that prevents transit damage.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Mn, Si, P, S) and yield strength per GB/T 3091, issued per heat number
- CE certificate per EN 10219 for cold-formed welded structural hollow sections, required for EU market customs clearance
- ISO 9001:2015 quality management system certificate covering production process and testing procedures
- SGS or BV third-party inspection report verifying dimensional tolerance, surface quality, and wall thickness before shipment
- Material traceability documentation linking each bundle to heat number, production date, and test results
- Export customs documents including packing list, bill of lading, and certificate of origin for destination country clearance
Packaging, Loading & Delivery
- Q235B welded square steel tubes bundled with steel strips at both ends and middle, sized to prevent shifting during ocean transit
- Galvanized surface treatment tubes packed with edge protectors and waterproof wrapping to preserve zinc coating integrity
- 6m and 12m standard lengths loaded in 20ft and 40ft containers with optimized nesting to maximize payload per shipment
- Random length or cut-to-order tubes marked with heat number, steel grade Q235B, and dimensional identification on each piece
- Professional container loading with wooden chocks and steel wire lashing to prevent bundle movement and surface damage
- FOB, CIF, or DDP shipping terms available with complete export documentation for destination port or project site delivery
Starting Your Q235B Welded Square Steel Tube Inquiry
Submit your required section size, wall thickness, steel grade, surface treatment preference, and total quantity to receive a detailed quotation within 12 hours. We provide mill test certificates, third-party inspection coordination, and container loading plans before production begins — ensuring your Q235B welded square steel tube order arrives compliant and damage-free.
Request Quotation with Mill Test Certificate
Send your specification list including size, wall thickness, length, quantity, and destination port to receive pricing and delivery timeline.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjypipe.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
Frequently Asked Questions
Q: What steel grades are available for welded square steel tubes besides Q235B?
A: We produce welded square tubes in Q235B, Gr.B, S235, S275, S355, and STK400, covering GB, ASTM, EN, and JIS standards. Each grade is tested in our in-house laboratory with mill test certificates provided per batch.
Q: Can you produce non-standard sizes outside the 19×19mm to 800×800mm range?
A: Yes, we offer custom non-standard sizes with low MOQ requirements. Our 2,800+ specification range covers most project needs, and our engineering team can evaluate special dimension requests for feasibility and lead time.
Q: What surface treatment options are available for welded square tubes?
A: We offer black painting for temporary protection, hot-dip galvanizing for long-term corrosion resistance, varnish coating, and bare (uncoated) delivery. Surface treatment selection depends on your application environment and project specifications.
Q: Do you provide third-party inspection before shipment?
A: Yes, we coordinate SGS or BV third-party inspection for dimensional verification, surface quality check, and wall thickness measurement. Inspection reports are provided before container loading to confirm compliance with your order specifications.
Q: What certifications do your welded square tubes carry for international projects?
A: Our welded square tubes carry CE certification per EN 10219/10210 for EU markets, ISO 9001:2015 quality certification, and Singapore FPC approval. Mill test certificates document chemical composition and mechanical properties per the applicable standard.
