Description
Factory-Direct Carbon Steel Square Rectangular Steel Tube Supplier — 2,800+ specifications in Q195–Q345 grades shipped to 50+ countries with CE EN 10210/10219 and ISO 9001 certification.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Square / Rectangular Steel Tube |
| Product Type | Square and Rectangular Steel Tube (SHS / RHS) |
| Steel Grade | Q195, Q215, Q235, Q345, 10#, 20# |
| Standard | GB/T 6728, EN 10210, EN 10219, JIS G3466, BS |
| Section Shape | Square / Rectangular |
| Size Range | 20 mm – 610 mm |
| Wall Thickness | 0.6 mm – 20 mm |
| Length | Standard or as per customer’s request |
| Technique | ERW / Hot Rolled |
| Surface Treatment | Bare surface, Varnish painting, Galvanizing, or as per customer’s request |
| Tolerance | ±1%, ±5% |
| Ends | Plain |
| Application | Civil engineering, Architecture, Steel towers, Shipyard, Scaffolding, Struts, Piles for landslide suppression, Structural frames |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants and warehouse projects |
| Construction Companies | High-rise building columns, bridge support struts, scaffolding systems |
| Machinery Manufacturers | Equipment base frames, conveyor support structures, hydraulic ram housings |
| Infrastructure Developers | Piles for landslide suppression, steel tower cross-arms, culvert reinforcement |
What Negative Tolerance Really Costs on a Structural Frame Order
A ±5% wall-thickness deviation on a Q345 RHS can shift theoretical weight by enough to fail acceptance inspection.
When procurement teams order carbon steel square rectangular steel tube by theoretical weight but receive material at the lower edge of tolerance, the load-bearing capacity drops below design assumptions. I once watched an entire container of 40×40 SHS get rejected at a West African job site because the actual wall thickness fell short of what the mill certificate implied. The return freight alone exceeded the cargo value. [NEED_CITE: EN 10219 cold-formed hollow section tolerance requirements] Fragmented sourcing from multiple traders makes this worse — each batch carries different tolerance behavior, and no single mill test certificate covers the full order.
Matching Wall Thickness and Grade to Structural Load Paths
For scaffolding and temporary works, Q195 or Q215 grades in thinner walls (0.6–2.0 mm) provide adequate performance at lower cost. When the carbon steel square rectangular steel tube serves as primary structural framing — building columns, bridge struts, or equipment skids — Q345 delivers higher yield strength without increasing section dimensions. Our production lines cover the full 0.6–20 mm range across 2,800+ specifications, so EPC contractors can consolidate SHS, RHS, and round pipe into a single purchase order rather than coordinating five different traders.
Compliance Pathways for EU, North America, and Asian Markets
Structural hollow sections exported to the European Union must carry CE marking under EN 10210 (hot-finished) or EN 10219 (cold-formed), with factory production control audited by a notified body. [NEED_CITE: CE marking requirements for structural steel hollow sections EN 10210 EN 10219] North American projects typically specify ASTM A500 Grade B or C, while Southeast Asian and Middle Eastern tenders often accept GB/T 6728 or JIS G3466 with mill test certificates. Our in-house physical and chemical laboratory tests every heat before release, and we arrange SGS or BV third-party inspection for clients who require independent verification. [NEED_CITE: steel grade equivalence between EN ASTM and GB standards]
Understanding Q-Series Grades and ERW Weld Integrity
The Q-designation system (Q195 through Q345) follows the Chinese GB standard framework where the number indicates minimum yield strength in MPa. Q195 and Q215 suit light structural and fencing applications; Q235 is the workhorse grade for general construction; Q345 provides roughly 50% higher yield strength for heavily loaded frames. Our ERW welding process produces a continuous longitudinal seam that undergoes online ultrasonic inspection, and the weld zone is normalized to match base metal mechanical properties. Hot rolled variants are available for thicker walls above 6 mm where seamless-like performance is needed without the cost premium of true seamless pipe. Surface treatment choices — bare, varnish, or hot-dip galvanized — depend on the service environment: galvanized coating extends service life in coastal or high-humidity conditions, while bare tubes with site-applied painting suit enclosed structural frames.
Hidden Costs of Unverified Material and Missing Certificates
Ordering carbon steel square rectangular steel tube without verified mill test certificates creates three failure modes: customs holds at destination port (CE documentation gaps in EU markets), structural rejection during third-party inspection (grade substitution or tolerance exceedance), and weld defects when actual chemistry deviates from what the fabricator assumed. [NEED_CITE: consequences of missing mill test certificates in steel procurement] A single container delayed at Rotterdam for documentation review can cost more in demurrage than the entire shipment value. Our system ties every bundle to its heat number, so traceability runs from raw coil to finished tube.
Why Project Procurement Teams Consolidate Here
Our factory operates three dedicated production lines with in-house physical and chemical laboratories — every heat is tested for chemical composition and mechanical properties before shipment. We hold 41 invention patents including proprietary sharp-corner rectangular tube technology that achieves tight corner radii impossible with standard roll-forming. The product range covers 2,800+ specifications with wall thickness up to 20 mm (and up to 40 mm on specialized lines), so a single purchase order can cover SHS, RHS, round pipe, and structural sections. CE certification under EN 10210/10219, ISO 9001:2015, Singapore FPC, and SGS/BV verification satisfy compliance requirements across EU, Southeast Asian, and Middle Eastern markets. We export to 50+ countries with professional container loading optimization — a 20-foot container loaded with mixed-size RHS can carry 20+ tons when nesting is planned correctly.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q345B chemical composition and yield strength per GB/T 6728 or EN 10219 as specified
- CE certificate covering EN 10210 hot-finished or EN 10219 cold-formed hollow sections for EU market customs clearance
- ISO 9001:2015 quality management system certificate covering design, production, and inspection of welded steel tubes
- SGS or BV third-party inspection report available for clients requiring independent verification before shipment
- Material traceability sheet linking each bundle to heat number, coil origin, and test results
- Customs document package including packing list, bill of lading, and certificate of origin formatted for destination port requirements
Packaging, Loading & Delivery
- Bare Q235B and Q345B tubes bundled with steel strips and waterproof cloth wrapping to prevent surface rust during ocean transit
- Galvanized square and rectangular tubes packed with edge protectors and separation mats to preserve zinc coating integrity
- Mixed-size container loading plans optimized for 20-foot and 40-foot containers — smaller SHS nested inside larger RHS to maximize weight per container
- Custom cut-to-length service available for 6-meter and 12-meter standard lengths, with saw-cut ends deburred and marked by heat number
- Each bundle labeled with steel grade, size, wall thickness, heat number, and net weight for site identification
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to 50+ countries
Getting Your Quotation and Mill Test Certificate Ready
Send your specification list — section shape, outer dimensions, wall thickness, steel grade, quantity, and destination port — and receive a detailed quotation within 12 hours including unit price, delivery schedule, and applicable certification. For non-standard sizes outside the 20–610 mm range, we provide custom roll-forming proposals with confirmed lead times.
Start Your Carbon Steel Square Rectangular Steel Tube Inquiry
Submit your specifications via email or WhatsApp to receive pricing, mill test certificate samples, and container loading plans.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjysteel.com
Email: admin@sdxjysteel.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
