Description
Factory-Direct ERW Square & Rectangular Steel Tube — Vertically integrated from raw coil to finished SHS/RHS, eliminating third-party sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B/Q345B ERW Square & Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (SHS/RHS) |
| Steel Grade | Q195, Q235B, Q345B, S235JR, S275JR, S355J2, SS400, ASTM A53 (A/B), ASTM A106 (B/C), API 5L (Gr.A, Gr.B, X42, X52, X60, X70) |
| Standard | GB/T 6728, EN 10219, EN 10210, ASTM A500, ASTM A53, ASTM A106, API 5L, JIS G3466 |
| Section Shape | Square / Rectangular |
| Size Range | 15mm × 15mm – 800mm × 800mm |
| Wall Thickness | 1mm – 50mm |
| Length | 6m / 12m (customized available) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Black Painted / Varnished / Hot-Dip Galvanized / Electro-Galvanized / 3LPE / 3LPP Coated / Oiled |
| Tolerance | ±1% |
| Ends | Plain / Beveled |
| Application | Steel structures / Construction frameworks / Scaffolding / Oil & gas pipeline transmission / Machinery / Shipbuilding & offshore platforms / Automotive chassis |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building columns, beam-to-column connections, warehouse frames, scaffolding systems |
| Oil & Gas | Pipeline transmission supports, drilling platform structures, hydraulic and pneumatic systems |
| Shipbuilding & Offshore | Marine piping, offshore platform support structures, corrosion-resistant galvanized tubes |
| Industrial & Machinery | Conveyor structures, machine frames, automotive chassis and exhaust systems |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
Dimensional accuracy directly affects load-bearing calculations and connection fit-up on site.
When sourcing ERW square and rectangular steel tube from overseas, ±1% tolerance may sound acceptable on paper — but on a multi-story steel frame, cumulative deviation across dozens of beam-to-column joints creates alignment failures that require costly rework. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]. Worse, negative tolerance beyond specification reduces actual wall thickness, compromising structural integrity while inflating theoretical weight calculations. Buyers who skip third-party inspection often discover these discrepancies only after containers arrive at destination ports.
How ERW Square & Rectangular Steel Tube Matches Structural Engineering Demands
The ERW welding process produces consistent seam quality with in-line dimensional monitoring, ensuring that Q235B and Q345B grades maintain uniform mechanical properties across the entire length. For construction frameworks requiring EN 10219 compliance, our fabrication workshop prepares shop drawings with precise cut-to-length specifications, eliminating on-site welding delays. Hot-dip galvanized finish provides corrosion resistance for coastal or outdoor applications, while black painted or oiled surfaces suit indoor structural use where appearance matters less than cost efficiency.
Structural Code Compliance and Surface Protection Selection
Engineering projects governed by EN 1993 (Eurocode 3) or AISC 360 require certified material properties and traceable mill test certificates for every heat number. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards]. For buried or marine environments, 3LPE/3LPP coating or hot-dip galvanizing (zinc layer ≥45μm) prevents corrosion that would otherwise compromise load-bearing capacity within years. S355J2 grade offers higher yield strength than Q235B for heavy-duty applications, but requires proper welding procedures (WPS/PQR) to avoid hydrogen-induced cracking in thick-wall sections. Custom lengths (6m/12m or cut-to-order) reduce on-site cutting waste and accelerate erection schedules.
Steel Grade Selection and ERW Process Fundamentals
Q-series (Q235B, Q345B) dominates Chinese domestic construction, while S-series (S235JR, S275JR, S355J2) aligns with European EN standards, and ASTM A53/A500 serves North American projects. The ERW (Electric Resistance Welded) process uses high-frequency current to fuse the steel strip edges, producing a weld seam as strong as the parent metal — ideal for square and rectangular profiles where uniform corner strength matters. Unlike seamless tubes, ERW offers cost efficiency for structural applications below 20MPa internal pressure. Wall thickness from 1mm to 50mm covers both light-gauge purlins and heavy-duty columns, with ±1% tolerance ensuring predictable weight calculations. [NEED_CITE: ERW vs seamless steel tube application comparison]. Hot-dip galvanizing adds 45-85μm zinc coating for 20-50 year corrosion protection in moderate environments, while 3LPE coating suits buried pipelines requiring mechanical damage resistance.
Hidden Costs of Unverified Material Certification
Purchasing ERW square and rectangular steel tube without EN 10204 3.1/3.2 mill test certificates risks customs rejection in EU markets, where CE marking per EN 10219 is mandatory. [NEED_CITE: CE marking requirements for structural steel hollow sections]. Material substitution — receiving Q235B when S355J2 was specified — creates structural safety hazards and potential liability if discovered during third-party inspection. Negative tolerance abuse (actual wall thickness below nominal) reduces load capacity while buyers pay for theoretical weight, inflating project costs by 5-15% without visible warning until failure.
Why Source from an Integrated Manufacturer
Our vertically integrated facility combines raw steel production with fabrication workshop capabilities, offering 2,800+ size specifications in stock and eliminating the traceability gaps that occur when buyers coordinate separate material suppliers and processors. Every shipment includes complete quality documentation: WPS/PQR for certified welding procedures, dimensional inspection reports, coating thickness measurements, and EN 10204 3.1 mill test certificates with full chemical composition and mechanical test results. Third-party inspection (SGS/BV/TÜV) is available at any production stage — raw material, in-process, or pre-shipment — providing independent verification for international projects. CE marking per EN 10210/EN 10219 ensures EU customs clearance, while ISO 9001 certification documents our quality management system from coil procurement to final packaging. Professional loading teams specialize in oversized cargo and container optimization, reducing shipping costs for 6m/12m length tubes through strategic bundling and weight distribution.
Documentation & Compliance
- Mill test certificate documenting Q235B/Q345B chemical composition and yield strength per GB/T 6728 or EN 10219
- CE certificate (EN 10210/EN 10219) with Declaration of Performance for EU market compliance
- ISO 9001 quality management certificate covering entire production process from raw material to finished product
- SGS or BV third-party inspection report verifying dimensional accuracy, coating thickness, and weld seam quality
- Material traceability by heat number linking each tube to specific steel coil and production batch
- Customs documents including packing list, bill of lading, and certificate of origin for import clearance
Packaging, Loading & Delivery
- ERW square and rectangular steel tube bundled with steel strips and edge protectors to preserve galvanized coating during ocean transit
- Hot-dip galvanized surfaces wrapped with waterproof paper to prevent white rust formation during storage and shipping
- 6m/12m length tubes loaded in 20ft/40ft containers with optimized weight distribution to maximize payload while meeting port weight restrictions
- Custom cut-to-length service available for project-specific dimensions, reducing on-site cutting waste and accelerating installation
- Each bundle marked with heat number, steel grade (Q235B/Q345B/S355J2), size specification, and production date for site identification
- FOB/CIF/DDP shipping terms with door-to-door logistics coordination for oversized cargo requiring special equipment
How to Request a Quotation for Your Project
Submit your project drawings (PDF/DWG), steel grade requirements (Q235B/Q345B/S355J2), size specifications, surface treatment preference, and destination port to receive a detailed quotation within 24 hours, including material cost, fabrication charges, coating fees, packing expenses, and shipping rates. Our engineering team will review shop drawings, confirm material availability from 2,800+ specifications in stock, and provide a production schedule with typical lead times. Specify any third-party inspection requirements (SGS/BV/TÜV) or certification needs (CE marking, EN 10204 3.2 certificates) to ensure compliance with your project standards.
Frequently Asked Questions
Q: How do Q235B, S235JR, and ASTM A36 steel grades compare for structural applications?
A: Q235B (Chinese GB standard), S235JR (European EN standard), and ASTM A36 (American standard) offer similar yield strength around 235 MPa and are interchangeable for general construction frameworks. For higher load requirements, Q345B corresponds to S355JR or ASTM A572 Grade 50 with yield strength around 345-355 MPa. We provide cross-reference documentation and can supply mill test certificates confirming compliance with your specified standard.
Q: Can you arrange third-party inspection before shipment?
A: Yes, we coordinate SGS, BV, or TÜV inspection at any production stage — raw material verification, in-process dimensional checks, coating thickness measurement, or pre-shipment final inspection. Inspection reports are included in the documentation package at no additional coordination cost, though third-party inspection fees are borne by the buyer.
Q: What is the minimum order quantity for custom wall thickness or non-standard sizes?
A: Standard sizes from our 2,800+ specification range have no minimum order quantity. Custom wall thickness or non-standard side lengths typically require minimum 5-10 tons depending on specification, as these require dedicated production runs. Contact us with your exact requirements for a tailored quotation.
Q: When should I choose hot-dip galvanized versus 3LPE coated versus black painted finish?
A: Hot-dip galvanizing (45-85μm zinc coating) suits outdoor or coastal environments requiring 20-50 year corrosion protection. 3LPE/3LPP coating provides mechanical damage resistance for buried pipelines or abrasive environments. Black painted or oiled finish is cost-effective for indoor structural applications where corrosion resistance is not critical. We can advise based on your specific project environment and design life requirements.
Q: How is invoicing calculated — theoretical weight or actual weight?
A: We invoice by actual weight as measured at our facility before shipment, ensuring you pay only for the material received. Theoretical weight calculations (based on nominal dimensions and standard density) are provided for reference during quotation, but final invoicing reflects actual measured weight. This approach eliminates disputes over negative tolerance variations.
Request Your ERW Square & Rectangular Steel Tube Quotation Today
Send your project specifications, steel grade requirements, and destination port to receive a detailed quotation with mill test certificate documentation within 24 hours.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
