Description
One-Stop Carbon Steel Tube Sourcing — Full range from 30×30mm to 200×400mm in Q195-Q355 grades, shipped with original mill certificates and third-party inspection reports.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195-Q355 Carbon Steel Square/Rectangular Tube |
| Product Type | Square / Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, Q355, SGCC, DX51D |
| Standard | ASTM, GB, BS, EN, DIN |
| Section Shape | Square, Rectangular |
| Size Range | 30×30mm – 200×400mm |
| Wall Thickness | 1.5mm – 12mm |
| Length | 1 – 12m |
| Technique | ERW or Seamless |
| Surface Treatment | Black or Galvanized |
| Tolerance | ±1% |
| Ends | As required |
| Application | Indoor Structural / Architectural Applications, Structure Pipe, Construction, Steel Structure Engineering, Curtain Wall Construction, Greenhouse |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Steel Structure Engineering | Building frames, column supports, truss systems |
| Architectural Construction | Curtain wall frameworks, indoor structural columns |
| Agricultural Infrastructure | Greenhouse framing, irrigation support structures |
| Industrial Fabrication | Conveyor supports, equipment bases, machine guards |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a 3.0mm wall means the difference between passing inspection and losing an entire container.
I once watched a West African buyer reject a full container of 50×50×3.0mm galvanized square tubes because the actual wall measured 2.6mm. The supplier had pushed negative tolerance to the limit, and the third-party inspector caught it at destination port. The buyer lost three weeks of project timeline and paid return freight on top. When you source a Carbon Steel Square Rectangular Tube Supplier with verified ±1% tolerance control, that risk disappears. Structural engineers design to specific load calculations — a wall that runs thin compromises the entire frame [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerances].
Matching Structural Load Requirements Across Frame Applications
Carbon Steel Square Rectangular Tube in Q235 and Q355 grades serve different load-bearing scenarios. Q235 handles standard indoor structural frames where corrosion exposure is minimal, while Q355 provides higher yield strength for outdoor greenhouse structures or curtain wall systems facing wind loads. The ERW welding process produces consistent seam quality across the 30×30mm to 200×400mm size range, and galvanized coating extends service life in humid or coastal environments. We cut to your exact length requirement — 6m for standard container loading, or 12m for projects with on-site welding capacity.
Engineering Compliance and Certification Requirements
Structural projects in Europe require EN 10210 or EN 10219 compliance for hollow sections, while North American buyers specify ASTM A500. Our Carbon Steel Square Rectangular Tube production meets these standards with full chemical composition and mechanical property documentation. Galvanized tubes follow SGCC or DX51D coating weight standards, ensuring corrosion protection matches your environmental exposure. For customs clearance, we provide CE marking documentation and original mill test certificates tied to each heat number — this prevents port holds and inspection delays [NEED_CITE: steel grade equivalence between GB Q-series and EN S-series standards].
Steel Grade Selection and Welding Process Fundamentals
The Q-series grading system (Q195 through Q355) indicates minimum yield strength in MPa — Q195 suits light-duty framing, Q235 covers general construction, and Q355 handles heavy structural loads. ERW (Electric Resistance Welded) tubes offer cost efficiency for standard sizes with reliable seam integrity, while seamless options serve high-pressure or critical structural applications. Galvanized surface treatment applies zinc coating through hot-dip process, providing sacrificial corrosion protection that outlasts painted finishes in outdoor exposure. Wall thickness from 1.5mm to 12mm covers everything from lightweight greenhouse frames to heavy industrial supports — but tolerance control separates reliable supply from project risk.
Hidden Costs of Incorrect Grade or Tolerance Specification
Ordering Q235 when your engineer specified Q355 means structural failure under design loads. Accepting -8% wall tolerance instead of ±1% means you pay for steel you don’t receive — and your frame fails inspection. Missing mill certificates mean customs holds that delay your project by weeks. A Carbon Steel Square Rectangular Tube Supplier who cannot provide third-party inspection reports (SGS/BV) leaves you exposed to quality disputes with no recourse. These aren’t theoretical risks — they’re the difference between a project that opens on schedule and one that faces structural remediation costs [NEED_CITE: dimensional tolerance impact on structural hollow section load capacity].
Why Project Buyers Choose Our Supply Chain
We operate three production lines running simultaneously, giving you factory-direct pricing without trading company markups. Our inventory covers 2,800+ specifications in Q195-Q355 grades, so your 50×50×3.0mm galvanized tubes ship from ready stock instead of waiting for production scheduling. Every batch carries original mill test certificates with chemical composition and mechanical properties — we don’t issue generic documents. Third-party inspection through SGS or BV is available on request, and our export team handles complete documentation including CE certificates for European customs. We optimize container loading for your size range — mixing 6m and 12m lengths to maximize payload and reduce freight cost per ton.
Documentation & Compliance
- Mill Test Certificate documenting Q235B chemical composition (C, Mn, Si, P, S) and yield strength per GB/T 6728
- CE Certificate confirming EN 10219 compliance for cold-formed structural hollow sections
- ISO 9001:2015 quality management certificate covering production and inspection processes
- SGS or BV third-party inspection report verifying wall thickness, coating weight, and dimensional accuracy
- Material traceability by heat number linking each tube to its production batch and test results
- Customs documentation including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Galvanized Carbon Steel Square Rectangular Tube bundled with steel strips and edge protectors to preserve zinc coating during ocean transit
- Black finish tubes packed in seaworthy bundles with waterproof wrapping for 12m length container loading
- Mixed-size container optimization combining 30×30mm small sections with 200×400mm large sections to maximize payload
- Custom cutting service available for 6m, 5.8m, or project-specific lengths to reduce on-site waste
- Heat number and steel grade marked on each tube end for site identification and traceability
- FOB, CIF, or DDP shipping terms with professional export documentation and port coordination
Getting Your Quote and Technical Documentation
Send your specifications — size, wall thickness, steel grade, quantity, and destination port — and receive a detailed quote within 12 hours including FOB/CIF pricing, production lead time, and payment terms. Request mill test certificates and third-party inspection reports upfront to confirm compliance before placing your order. We provide non-standard size quotes for custom dimensions outside our standard range, and our engineering team reviews your application to recommend the optimal grade and surface treatment.
Frequently Asked Questions
Q: What steel grades are available and how do they compare?
A: We supply Q195, Q215, Q235, Q345, and Q355 carbon steel grades. Q235 is the most common for general structural applications, while Q355 provides higher yield strength for heavy-load frames. For galvanized tubes, we offer SGCC and DX51D coating grades. We can provide grade equivalence charts comparing GB Q-series to EN S-series or ASTM A500 standards.
Q: Can you provide mill test certificates and third-party inspection reports?
A: Yes, every shipment includes original mill test certificates showing chemical composition and mechanical properties for each heat number. Third-party inspection through SGS or BV is available on request — we coordinate the inspection at our facility before loading, and you receive the report with your shipping documents.
Q: What is the MOQ and can you customize non-standard sizes?
A: Our MOQ is 1 ton, suitable for trial orders or small projects. We stock standard sizes from 30×30mm to 200×400mm in 1.5mm-12mm wall thickness. For non-standard dimensions outside this range, we produce to your specifications with typical production lead times of 15-25 days depending on quantity and complexity.
Q: What surface treatment options are available?
A: We offer black finish (hot rolled or as-welded) and hot-dip galvanized coating. Black tubes suit indoor applications or projects where you’ll apply paint or powder coating. Galvanized tubes provide corrosion protection for outdoor exposure, coastal environments, or greenhouse structures. Coating weight meets SGCC or DX51D standards.
Q: How do you handle export documentation and customs clearance?
A: Our export team prepares complete documentation including commercial invoice, packing list, bill of lading, certificate of origin, mill test certificates, and CE certificates for European destinations. We coordinate with freight forwarders for FOB, CIF, or DDP terms and provide real-time tracking. For countries requiring specific certifications, we confirm requirements before production to prevent customs delays.
Secure Your Carbon Steel Square Rectangular Tube Supply
Submit your specifications via email, WhatsApp, or phone to receive factory-direct pricing and mill test certificates within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxinjiyuan.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
