Description
Direct Mill Supply for Q235 SS400 ERW Structural Tubes — Every Q235 and SS400 ERW square and rectangular steel tube ships with original mill test certificates and full heat-number traceability, sourced directly from our rolling facility in Shandong.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 / SS400 ERW Square & Rectangular Steel Tube |
| Product Type | ERW Welded Square and Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, SS400, ASTM A36, S235 |
| Standard | ASTM, API, CE, JIS, ISO 9001 |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 200×200 mm |
| Wall Thickness | 1.5 – 30 mm |
| Length | 1 – 12 m (standard 6 m / 6.4 m / 12 m; custom length available) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Galvanized Coated / Slightly Oiled |
| Tolerance | ±5% |
| Ends | Plain |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Application | Structure Pipe, Fluid Pipe, Boiler Pipe, Gas Pipe, Oil Pipe, Hydraulic Pipe, Construction, Bridge, Machinery, Mining, Electrical Installation |
| MOQ | 25 Tons (1×20ft container) |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building structural frames, bridge support columns, scaffolding uprights, highway guardrail posts |
| Industrial Machinery | Equipment base frames, conveyor support structures, crane boom sections, mining machinery skeletons |
| Energy & Utilities | Gas distribution pipelines, boiler support structures, hydraulic system frames, oil transport manifolds |
| Electrical Installation | Cable tray supports, substation structural frames, transmission tower bracing members |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±5% tolerance on a 200×200×10 mm ERW square tube means the difference between a passing inspection and a rejected shipment.
Structural engineers calculate load-bearing capacity based on nominal wall thickness. When actual thickness drifts beyond tolerance — especially with negative deviation practices common in unverified supply chains — the entire frame’s moment of inertia changes. On a warehouse project in the Middle East, I watched a contractor discover that 100×100 mm tubes with wall thickness below specification caused connection plates to sit at angles, forcing on-site re-cutting of every joint. The ERW square and rectangular steel tube supplier who shipped those tubes had no mill test certificates to verify heat numbers, and the replacement cost exceeded the original order value. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
How Q235 and SS400 ERW Tubes Match Structural Engineering Requirements
Q235 and SS400 represent the workhorse grades for general structural applications across Asia and the Middle East. Their yield strength positioning makes them suitable for building frames, bridge bracing, and machinery supports where extreme load conditions are not the primary design driver. The ERW welding process produces a continuous longitudinal seam that, when properly controlled, delivers consistent mechanical properties across the full 20×20 mm to 200×200 mm size range. For projects requiring corrosion resistance in coastal or industrial environments, galvanized-coated ERW square and rectangular steel tubes provide zinc layer protection without additional field treatment. Our Shandong facility maintains rolling schedules for both Q235 and SS400 in wall thicknesses from 1.5 mm to 30 mm, allowing single-source procurement for mixed-specification orders.
Engineering Compliance and Certification Pathways
Structural steel procurement for international projects must satisfy both the engineer’s specification and the importing country’s customs requirements. Q235 tubes conforming to GB/T 3091 or GB/T 6728 serve domestic Chinese projects and markets that accept Chinese national standards. For European projects, the same physical tubes must carry CE marking under EN 10219 for cold-formed welded structural hollow sections, with declared mechanical properties and factory production control documentation. [NEED_CITE: steel grade equivalence between GB Q235 and EN S235JR standards] ASTM A36 and SS400 serve North American and Japanese-specification projects respectively, though chemical composition and tensile requirements differ subtly between these grades. Third-party inspection by SGS or BV before shipment resolves most customs and client-side verification concerns, particularly for pressure-containing applications where API certification may be required.
Understanding ERW Welding Process and Grade Selection
ERW (Electric Resistance Welded) steel tubes are formed from hot-rolled coil that passes through continuous forming rolls, with the longitudinal seam welded by electrical resistance heating without filler metal. This process suits high-volume production of square and rectangular sections in the 20–200 mm size range, offering cost advantages over seamless tubes for non-pressure structural applications. The Q-series grades (Q195, Q215, Q235, Q345) follow Chinese national standards where the number indicates minimum yield strength in MPa. SS400 follows JIS G 3101, where 400 represents minimum tensile strength in N/mm². S235 follows EN 10025, with 235 indicating yield strength. These grades overlap significantly in chemical composition and mechanical properties, but equivalence is not automatic — a project specifying SS400 cannot simply accept Q235 without engineer approval, as tensile strength and elongation requirements differ. [NEED_CITE: JIS G 3101 SS400 mechanical property requirements] Surface treatment selection depends on the service environment: hot-rolled (black) tubes suit indoor structural frames or applications where field painting is planned; galvanized coatings provide 50–150 μm zinc protection for outdoor or corrosive environments; slight oiling prevents transit rust for tubes destined for immediate fabrication.
The Hidden Cost of Unverified ERW Square and Rectangular Steel Tube Supply
Purchasing structural tubes without verified mill test certificates creates risks that surface only during installation or inspection. Chemical composition outside the specified grade range affects weldability — high carbon equivalents cause cracking in field welds, while insufficient manganese reduces strength. Wall thickness below nominal tolerance reduces load capacity, but the financial impact extends beyond structural failure: customs authorities in the EU and Middle East increasingly reject steel imports lacking proper CE documentation or MTC traceability. [NEED_CITE: EU Construction Products Regulation steel certification requirements] A 20-ton container of non-conforming tubes represents not just material cost, but freight, customs duties, project delays, and replacement sourcing at premium prices.
Why Source Your ERW Square and Rectangular Steel Tube from XJY Plate
Our Shandong rolling facility produces ERW square and rectangular steel tubes in Q235, SS400, Q345, and ASTM A36 grades with wall thickness from 1.5 mm to 30 mm, covering the full range from light structural bracing to heavy-duty equipment frames. Every shipment includes original mill test certificates documenting heat number, chemical composition, and mechanical properties — not reissued copies from trading companies. We maintain ready stock in common specifications (20×20 mm to 200×200 mm) while offering custom cutting to project-specified lengths between 1 m and 12 m, reducing on-site waste. Our facility holds ISO 9001:2015 certification and CE marking under EN 10219, with SGS and BV third-party inspection available before shipment. Professional heavy cargo loading experience ensures that 20ft and 40ft containers maximize payload without damaging tube surfaces or exceeding port weight limits.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition (C, Si, Mn, P, S content) and mechanical properties (yield strength, tensile strength, elongation) per GB/T 700
- CE certificate confirming EN 10219 compliance for SS400 and S235 structural hollow sections with declared performance values
- ISO 9001:2015 quality management certificate covering ERW welding process control and dimensional inspection
- SGS or BV third-party inspection report verifying wall thickness, surface quality, and dimensional tolerance before container sealing
- Material traceability by heat number linking each bundle to its original coil and rolling schedule
- Customs documentation including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Q235 and SS400 ERW tubes bundled with galvanized steel strips at intervals preventing bundle separation during ocean transit, with edge protectors preserving surface finish
- Galvanized-coated tubes wrapped in waterproof paper with plastic caps on tube ends to prevent zinc coating damage and moisture ingress during container shipping
- Mixed-size container loading optimized for 20ft and 40ft units, with heavier wall thickness tubes (10–30 mm) positioned at container bottom and lighter sections (1.5–5 mm) on top to prevent deformation
- Custom-length tubes (1–12 m) cut to project specifications and marked with heat number, steel grade, and dimensional information on each piece
- FOB, CIF, and DDP shipping terms available from Chinese ports to global destinations, with professional flatbed and container loading for tubes up to 12 m length
Securing Your ERW Square and Rectangular Steel Tube Quotation
Submit your specification requirements — steel grade (Q235, SS400, Q345, or ASTM A36), section dimensions, wall thickness, length, quantity, and destination port — to receive a detailed quotation including material cost, processing fees, and shipping terms within 12 hours. We provide original mill test certificates before shipment for your quality verification, and third-party inspection can be arranged at our facility if your project requires independent confirmation.
Request Your ERW Square and Rectangular Steel Tube Quotation
Send your specification sheet to receive pricing, mill test certificate samples, and delivery schedule for your next structural steel procurement.
Contact: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjyplate.com
