Description
Direct Mill Supply — Vertically integrated production from raw steel to finished welded square and rectangular steel tubes, eliminating third-party sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square / Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, GR.A, GR.B, S235, S355 |
| Standard | ASTM A213, DIN EN 10217-1 |
| Section Shape | Square / Rectangular |
| Size Range | 20mm–80mm+ (customizable) |
| Wall Thickness | 0.8–30 mm |
| Length | 100mm–11800mm (customizable) |
| Technique | Welded (ERW) |
| Surface Treatment | Pre-galvanized / Hot-dip galvanized / Bare / Oiled / Black original steel |
| Tolerance | ±1% |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Packing | Standard Seaworthy Packing |
| Application | Structure pipe, Steel fence, Steel post, Steel construction, Warehouse construction, Building construction |
| MOQ | 10 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Warehouse & Industrial Construction | Primary frame columns, purlin bracing, mezzanine support structures |
| Steel Fencing & Infrastructure | Perimeter fence posts, highway barrier supports, lighting pole bases |
| EPC Project Structural Packages | Modular building frames, equipment support platforms, pipe rack structures |
| Commercial Building Construction | Curtain wall sub-frames, canopy supports, interior structural partitions |
Where Negative Tolerance Eats Into Structural Load Capacity
Wall thickness deviation beyond ±1% directly reduces moment of inertia and compromises load-bearing calculations.
When procurement teams source welded square and rectangular steel tubes from fragmented suppliers, material traceability gaps emerge — the mill test certificate references a heat number that cannot be traced back to the original slab. On African EPC sites, I have seen entire container loads rejected because actual wall thickness fell 12% below nominal, turning theoretical weight calculations into fiction. The structural engineer signs off on S355 grade assumptions, but the delivered tubes carry Q235 chemistry with no documentation to prove otherwise. Customs authorities in the EU increasingly demand EN 10204 3.2 certificates for structural hollow sections, and without proper material traceability, containers sit at port accumulating demurrage charges. [NEED_CITE: EN 10219 cold-formed structural hollow section tolerance requirements]
Matching Wall Thickness to Structural Frame Requirements
The 0.8–30 mm wall thickness range covers both light-gauge fencing applications and heavy-duty structural columns. For warehouse construction in coastal environments, pre-galvanized welded square and rectangular steel tubes with 60–80 μm zinc coating provide corrosion resistance without field painting. When structural calculations demand higher load capacity, Q345 grade offers increased yield strength over Q235, while S355 meets European EN 10219 requirements for projects targeting EU markets. Our in-house CNC cutting and punching services eliminate secondary processing delays at the fabrication shop.
Structural Code Compliance and Surface Treatment Selection
Engineering specifications for steel construction typically reference EN 1993 (Eurocode 3) or AISC 360 for load-bearing calculations, requiring certified material properties and dimensional accuracy. The choice between pre-galvanized and hot-dip galvanized surface treatment depends on corrosion environment severity — pre-galvanized suits indoor warehouse framing, while hot-dip galvanized withstands outdoor exposure in Middle East and Southeast Asian climates. For projects requiring CE marking under EN 10210 or EN 10219, the welded square rectangular steel tube must carry Factory Production Control certification and undergo third-party inspection before shipment. [NEED_CITE: steel grade equivalence between GB Q-series and EN S-series standards]
Understanding ERW Welding Process and Grade Selection
Electric Resistance Welding (ERW) produces a longitudinal seam by heating tube edges through electrical current and applying pressure — this method suits square and rectangular sections from 20mm to 80mm+ side lengths with consistent weld quality. The Q-series steel grades (Q195, Q215, Q235, Q345) follow Chinese GB standards, where the number indicates minimum yield strength in MPa; Q345 provides approximately 50% higher yield capacity than Q235 for the same cross-section. European S-series grades (S235, S355) and ASTM GR.A/GR.B serve equivalent structural functions but require different certification documentation for customs clearance. Wall thickness tolerance of ±1% ensures that theoretical weight calculations match actual delivered weight — critical for projects where freight costs are calculated per metric ton.
Hidden Costs of Unverified Material Sources
Purchasing welded square and rectangular steel tubes without mill test certificates creates downstream risks: engineering验收 fails when inspector cannot verify chemistry against S355 requirements, customs clearance delays occur when EN 10204 3.2 documentation is missing, and structural safety concerns emerge when actual wall thickness falls below design assumptions. Replacing rejected materials after container arrival at site costs three to four times the original purchase price when factoring return freight, replacement production, and project schedule delays. [NEED_CITE: structural steel procurement quality verification requirements]
Why Project Procurement Teams Choose Our Mill
Our vertically integrated facility operates three production lines with access to 2,800+ raw material specifications, meaning the welded square and rectangular steel tube you order comes from our own steel mill — not a trading company reselling third-party output. Every heat number is traceable from slab to finished tube, and our in-house laboratory issues Mill Test Certificates documenting chemical composition and mechanical properties per EN 10219 or ASTM A500. We hold CE certification for EN 10210 and EN 10219 structural hollow sections, ISO 9001 quality management, and accept SGS/BV third-party inspection before shipment. Custom lengths up to 11,800mm and non-standard dimensions are produced to your shop drawings, with professional container loading plans maximizing payload for 20ft and 40ft shipments.
Documentation & Compliance
- Mill Test Certificate documenting Q235/Q345 chemical composition and yield strength per DIN EN 10217-1
- CE certificate confirming compliance with EN 10210 (hot-formed) and EN 10219 (cold-formed) structural hollow sections
- ISO 9001 quality management certificate covering entire production process from raw material to finished welded square and rectangular steel tube
- SGS or BV third-party inspection report verifying dimensional accuracy, coating thickness, and weld quality before shipment
- Material traceability documentation linking each tube bundle to specific heat number and production batch
- Complete customs clearance package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Pre-galvanized and hot-dip galvanized welded square and rectangular steel tubes bundled with steel strips and edge protectors to preserve zinc coating during ocean transit
- Bare black tubes bundled with waterproof wrapping for 20mm–80mm sections, with bundle weight optimized for 20ft container payload
- Custom cut lengths from 100mm to 11,800mm available, with container loading plans maximizing space utilization for mixed-size orders
- Each bundle tagged with heat number, steel grade (Q235/Q345/S355), wall thickness, and length for site identification
- FOB, CIF, and DDP shipping terms available, with door-to-door logistics coordination to project sites in Middle East, Southeast Asia, and Africa
- MOQ of 10 tons applies to standard sizes; custom dimensions and non-standard lengths subject to production schedule confirmation
Requesting Quotation and Technical Documentation
Submit your project specifications including steel grade (Q235, Q345, S355), section dimensions, wall thickness, length, surface treatment preference, and destination port to receive detailed quotation with Mill Test Certificate sample. Our engineering team reviews shop drawings for custom fabrication requirements and provides container loading optimization for your order volume. Confirm certification requirements (CE/EN 10219 for EU markets, ASTM for North America) to ensure proper documentation for customs clearance.
Frequently Asked Questions
Q: What is the difference between Q235 and S235 steel grades for welded square and rectangular steel tubes?
A: Q235 follows Chinese GB standards while S235 follows European EN standards; both indicate minimum yield strength of 235 MPa but require different certification documentation. For EU projects specifying EN 10219, S235JR or S355JR grades with CE marking are required; for projects without European certification requirements, Q235 offers equivalent structural performance at lower cost.
Q: Can you provide EN 10204 3.2 certificates for European customs clearance?
A: Yes, we issue Mill Test Certificates per EN 10204 3.1 as standard, and EN 10204 3.2 certificates witnessed by third-party inspection agencies (SGS, BV, TÜV) are available for EU customs clearance. Our CE certification under EN 10210 and EN 10219 covers hot-formed and cold-formed structural hollow sections respectively.
Q: What is the MOQ for customized sizes and non-standard dimensions?
A: Standard sizes (20mm–80mm square/rectangular sections with 0.8–30mm wall thickness) have MOQ of 10 tons. Custom dimensions outside standard range or special lengths up to 11,800mm require production schedule confirmation, typically with higher MOQ depending on specification complexity.
Q: Pre-galvanized vs hot-dip galvanized — which surface treatment suits my project?
A: Pre-galvanized (60–80 μm zinc coating) suits indoor applications like warehouse framing and interior structural supports where corrosion exposure is limited. Hot-dip galvanized (45–85 μm zinc coating after dipping) provides superior corrosion resistance for outdoor applications in coastal environments, Middle East climates, or infrastructure projects requiring 20+ year service life.
Q: How do you handle container loading for mixed-size welded square and rectangular steel tube orders?
A: Our logistics team creates container loading plans maximizing payload for 20ft and 40ft containers, nesting smaller sections inside larger ones and optimizing weight distribution. Mixed orders combining different wall thicknesses and lengths are bundled separately with clear identification tags, and loading photos are provided before container sealing for your verification.
Request Welded Square Rectangular Steel Tube Quotation with Mill Test Certificate
Send your project specifications (steel grade, dimensions, wall thickness, quantity, destination port) to receive detailed quotation and technical documentation package 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
