Description
Factory Direct Square Steel Tubes — Q235 Q345 S355 square steel tube supplier producing from our own mill with full material traceability from billet to finished section.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Q345 S355 Square Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube |
| Steel Grade | Q235, Q235B, Q345, Q345B, S235JR, S275JR, S355J2, SS400, ASTM A53, ASTM A106 |
| Standard | ASTM A53, ASTM A106, API 5L, EN Standard (S235JR / S275JR / S355J2), GB Standard (Q195 / Q235 / Q345), JIS |
| Section Shape | Square, Rectangular |
| Size Range | 15mm×15mm – 800mm×800mm |
| Wall Thickness | 1mm – 50mm |
| Length | 6000mm, 12000mm or Customized |
| Technique | ERW, Hot Rolled, Cold Rolled |
| Surface Treatment | Black Painted, Varnished, Galvanized (Hot-Dip / Electro), 3LPE/3LPP Coated, Oiled |
| Tolerance | ±1% |
| Tensile Strength | 350 – 850 MPa |
| Yield Strength | 205 – 700 MPa |
| Elongation | 10% – 35% |
| Hardness | ≤ 200 HB |
| Application | Construction, Oil & Gas, Automotive, Machinery, Shipbuilding |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Structural frameworks for commercial buildings, scaffolding systems, warehouse columns and beams |
| Oil & Gas / Energy | Pipeline transmission supports, offshore platform structural members, drilling rig frames |
| Machinery & Industrial | Hydraulic cylinder bodies, pneumatic system housings, equipment frames for factory floors |
| Shipbuilding | Marine piping supports, offshore platform bracing, deck structural members |
| Automotive | Exhaust system frames, chassis structural components, roll cage assemblies |
What Negative Tolerance Really Costs on a Square Steel Tube Order
A 15% negative tolerance deviation turns a compliant shipment into rejected cargo at the destination port.
When overseas buyers receive square steel tubes sourced from traders who consolidate from multiple mills, the material certification chain breaks at the first inspection. I watched an entire container of Q345B rectangular tubes get rejected in Jakarta because the wall thickness measured 1.7mm against a declared 2.0mm — the freight cost to return and re-roll exceeded the original cargo value. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements] The problem is not the steel itself but the absence of a single accountable source controlling production from raw material to finished section.
How Wall Thickness Range Meets Structural Load Requirements
The 1mm to 50mm wall thickness range across 15×15mm to 800×800mm sections covers everything from light-gauge scaffolding to heavy-duty industrial columns. Q235 Q345 S355 square steel tube selections depend on whether the project demands lightweight framing or primary load-bearing members. Our vertically integrated production means the same facility that rolls the steel plate also forms and welds the tube, eliminating the material sourcing gap that causes tolerance inconsistencies.
Engineering Compliance Across International Standards
Structural projects specifying EN 10219 for European markets or ASTM A500 for North American construction require documented compliance at every stage. The Q235 Q345 S355 square steel tube range covers GB, EN, and ASTM grade equivalences with certified welding procedures per AWS D1.1 and EN 1090 execution classes. [NEED_CITE: steel grade equivalence mapping between GB Q series and EN S series standards] Third-party inspection from SGS, BV, or TÜV is available before shipment to verify dimensional accuracy and coating thickness against project specifications.
Steel Grade Selection and Manufacturing Process Explained
Q235 and Q345 represent the Chinese GB standard system where the number indicates minimum yield strength in MPa, while S235JR, S275JR, and S355J2 follow the European EN standard designation with JR indicating room-temperature impact testing and J2 specifying -20°C impact requirements. ERW (Electric Resistance Welded) production suits standard structural applications where cost efficiency matters, while hot rolled processes deliver heavier wall sections for primary structural members. Surface treatment selection depends on the service environment: hot-dip galvanizing provides long-term corrosion protection for outdoor exposure, black painted or oiled finishes suit indoor or temporary applications, and 3LPE/3LPP coating addresses aggressive chemical or marine environments.
Hidden Costs of Procuring from Unverified Sources
Material certificates that cannot be traced to specific heat numbers create liability exposure when structural inspectors request verification. Non-compliant coating thickness leads to premature corrosion and warranty claims, while dimensional inaccuracies force on-site rework that delays project handover. [NEED_CITE: structural steel fabrication quality control requirements per EN 1090] The true cost of cheap procurement appears in customs delays, failed inspections, and the freight expense of returning non-conforming cargo.
Why Project Teams Source from Our Integrated Facility
Our own steel mill with three production lines and over 2,800 raw material specifications means we control quality from billet to finished tube rather than consolidating from external suppliers. Every Q235 Q345 S355 square steel tube ships with mill test certificates documenting chemical composition and mechanical properties per heat number. We hold CE EN10210/EN10219 certification for European market compliance and ISO 9001 quality management with complete dimensional inspection and coating reports. Custom lengths up to 12,000mm and non-standard dimensions are produced to engineering drawings with shop drawing review and material optimization support. Professional loading plans account for oversized cargo and container weight distribution to prevent transit damage.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/S355 chemical composition and yield strength per EN10219 or ASTM A500 as specified
- CE certificate confirming EN10210 hot-finished or EN10219 cold-formed hollow section compliance for European project delivery
- ISO 9001 quality management certificate covering the full production process from raw material inspection to final dimensional verification
- SGS or BV third-party inspection report verifying wall thickness tolerance, coating thickness, and surface quality before container sealing
- Material traceability documentation linking each tube to specific heat numbers with complete chemical and mechanical test results
- Customs clearance package including packing list, bill of lading, and certificate of origin formatted for destination port requirements
Packaging, Loading & Delivery
- Q235 Q345 S355 square steel tubes bundled with steel strips and edge protectors to prevent coating damage during ocean transit
- Hot-dip galvanized surfaces wrapped with waterproof paper and plastic film to preserve zinc coating integrity in humid container environments
- 6-meter and 12-meter lengths optimized for 20ft and 40ft container loading with weight distribution plans maximizing cubic capacity
- Custom cut lengths marked with heat number and steel grade stenciled on each bundle for site identification and traceability
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination for project sites requiring direct delivery
- Oversized sections above 400mm packaged on steel frames with lashing points secured for container or breakbulk shipment
How to Initiate Your Procurement Process
Submit project drawings in PDF or DWG format with specified steel grades, dimensions, surface treatment requirements, and destination port to receive a detailed quotation within 24 hours. Our engineering team reviews shop drawings for material optimization and fabrication sequencing before production begins. Confirm certification requirements and third-party inspection needs to ensure compliance documentation matches your project specifications.
Frequently Asked Questions
Q: What is the grade equivalence between Q235, Q345, and European S series standards?
A: Q235 corresponds approximately to S235JR in yield strength, while Q345 aligns with S355JR/S355J2. Full chemical composition and mechanical property comparison is provided in the mill test certificate for your engineer’s verification.
Q: How do you ensure material traceability from production to delivery?
A: Each Q235 Q345 S355 square steel tube is traced to its specific heat number with mill test certificates documenting chemical composition and mechanical properties. The certificate travels with the shipment and is available for inspection at any stage.
Q: Can you produce non-standard dimensions and custom lengths?
A: Yes, we produce custom lengths up to 12,000mm and non-standard section dimensions based on engineering drawings. Minimum order quantities apply for special sizes, and our engineering team provides shop drawing review before production.
Q: What surface treatment options are available for different environments?
A: We offer black painted, oiled, hot-dip galvanized, electro-galvanized, and 3LPE/3LPP coated finishes. Selection depends on service environment: galvanized for outdoor corrosion protection, painted or oiled for indoor use, and 3LPE/3LPP for aggressive chemical or marine conditions.
Q: How does theoretical weight differ from actual weight?
A: Theoretical weight is calculated from nominal dimensions, while actual weight reflects production tolerances within ±1%. We provide both theoretical and actual weight calculations in quotation documents so buyers understand the material received.
Request Your Quotation with Mill Test Certificate
Send your project specifications including steel grade, dimensions, quantity, and destination port to receive pricing and complete documentation package.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
