Description
Factory-Direct ERW Steel Tubes — Q235 and SS400 square and rectangular hollow sections rolled and welded on our own production lines, shipped without trading markups to your project site.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 / SS400 ERW Welded Square and Rectangular Steel Pipe |
| Product Type | ERW Welded Square and Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, ASTM A500, S235, SS400 |
| Standard | ASTM, API, CE, JIS |
| Section Shape | Square / Rectangular |
| Size Range | 20×20 mm – 200×200 mm |
| Wall Thickness | 1.5 – 30 mm |
| Length | 1 – 12 m (customizable) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Black / Slightly Oiled |
| Tolerance | ±5% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Machinery / Fluid transport / Scaffolding / Industrial fabrication |
| MOQ | 25 Tons (1×20ft container) |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frameworks for industrial plants and warehouse construction |
| Construction Companies | High-rise building columns, beam systems, and scaffolding supports |
| Machinery Manufacturers | Precision frames for conveyors, automation equipment, and hydraulic structures |
| Infrastructure Developers | Bridge railings, sound barrier posts, and utility pole foundations |
| System Integrators | Conveyor support structures and industrial racking systems |
What Wall-Thickness Tolerance Actually Costs on a 200×200 Frame Order
A ±5% tolerance on a 10mm wall means the difference between passing SGS inspection at destination and having the entire container held at port.
When procurement teams order Q235 ERW welded square and rectangular steel tube for structural frames, the wall thickness specification on paper rarely matches what arrives on the dock. Negative tolerance drifting beyond acceptable limits triggers third-party inspection failures, customs holds, and project delays that cost far more than the per-ton savings from thinner material. Fragmented sourcing from multiple suppliers compounds the problem — each mill applies its own tolerance interpretation, and without centralized quality control, your structural engineer cannot verify load-bearing consistency across the full order. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Q235 and SS400 Grades to Structural Load Requirements
Q235 and SS400 ERW welded square and rectangular steel tube serve as the workhorse grades for non-critical structural frames, scaffolding, and machinery bases where moderate yield strength suffices. The 20×20 mm to 200×200 mm size range with wall thickness from 1.5 mm to 30 mm covers everything from light-duty conveyor supports to heavy equipment frames. Our in-house physical and chemical laboratory tests every heat before the tubes leave the mill, so when your engineer specifies Q235 for a warehouse column or SS400 for a machinery base, the mill test certificate matches the actual material in the container — not a blended batch from a trading company’s warehouse.
Engineering Compliance Across EU, North American, and Asian Markets
Structural hollow sections must satisfy different certification frameworks depending on destination: CE EN 10210 and EN 10219 for European import, ASTM A500 for North American projects, and JIS G3466 for Japanese-spec work. Q235 cross-references to S235 under EN standards and roughly aligns with ASTM A500 Grade B, but the equivalence is not automatic — customs authorities and project inspectors require documented proof of chemical composition and mechanical properties per the destination standard. Our production lines hold CE certification for EN 10210/10219, ISO 9001:2015 quality management, and Singapore FPC, with SGS and BV third-party verification available before loading. [NEED_CITE: steel grade equivalence mapping between GB Q series and EN S series]
ERW Welding Process and Hot Rolled Surface Treatment
Electric resistance welding fuses the steel strip edges under pressure and current without filler metal, producing a clean longitudinal seam suitable for square and rectangular profiles up to 200×200 mm. The hot rolled black surface with slight oiling provides basic rust prevention during transit and storage while remaining weldable and paintable without additional surface preparation. For projects requiring enhanced corrosion resistance, the same ERW base tubes can be galvanized or coated per specification. Wall thickness tolerance of ±5% applies across the full 1.5 mm to 30 mm range, though procurement teams should specify whether theoretical weight or actual weight pricing applies — negative tolerance beyond -10% risks inspection rejection on projects with strict dimensional requirements.
The Hidden Price of Unverified Steel Grades and Missing Certificates
Ordering Q235 ERW welded square and rectangular steel tube from suppliers without in-house testing creates a chain of unknowns: the chemical composition may not match the stated grade, the weld seam may lack proper fusion, and the mill test certificate may be fabricated or borrowed from another batch. When these tubes reach the project site, the consequences are not abstract — structural connections fail load tests, customs officials reject shipments lacking proper CE documentation, and contractors face rework costs that dwarf the initial per-ton savings. [NEED_CITE: consequences of non-compliant steel materials in structural construction projects]
Why Project Procurement Teams Source Direct from Our Mill
Our three dedicated production lines cover over 2,800 specifications of square, rectangular, and round steel tubes with wall thickness up to 40 mm, eliminating the need to coordinate multiple suppliers for pipes, plates, and sections. We hold 41 invention patents including proprietary sharp-corner rectangular tube technology that delivers tighter corner radii than standard ERW processes — critical for aesthetic architectural applications and precision machinery frames. Every shipment includes original mill test certificates documenting chemical composition and mechanical properties per heat number, with SGS or BV third-party inspection available at our facility before container loading. Professional loading plans optimize container utilization for the 20×20 mm to 200×200 mm size range, and we coordinate FOB, CIF, or DDP logistics to 50+ countries with real-time tracking.
Documentation & Compliance
- Mill test certificate documenting Q235 or SS400 chemical composition (C, Mn, Si, P, S) and yield strength per heat number
- CE certificate confirming compliance with EN 10210/EN 10219 for European Union customs clearance
- ISO 9001:2015 quality management system certificate covering the full ERW production process
- SGS or BV third-party inspection report verifying dimensional tolerance and surface quality before loading
- Material traceability documentation linking each tube bundle to its original heat number and production date
- Complete customs document package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Hot rolled black ERW square and rectangular tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Slight oiling applied to all Q235 and SS400 tubes before bundling to inhibit rust formation during container shipping
- Container loading plans optimized for 1–12 m lengths across the 20×20 mm to 200×200 mm size range to maximize 20ft and 40ft container utilization
- Heat number and steel grade stenciled on each bundle for site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to 50+ countries
- Custom cutting to project-specific lengths available before shipment to reduce on-site waste
Start Your Procurement with Verified Specifications
Submit your required steel grade (Q235, SS400, ASTM A500, or other), section dimensions, wall thickness, quantity, and destination port to receive a detailed quotation including unit price, delivery timeline, and applicable certification documentation within 12 hours. Our technical team will confirm material availability, provide mill test certificate samples, and coordinate third-party inspection scheduling based on your project compliance requirements.
Request Quotation and Mill Test Certificate
Send your specifications to admin@sdxjysteel.com or contact us via WhatsApp at +86 188 5315 7756 to begin your procurement process with verified documentation and factory-direct pricing.
