Description
Factory-direct ERW rectangular tubes — vertically integrated from raw steel mill to finished fabrication, covering Q195 through Q345 grades under ASTM and EN standards.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 Rectangular Steel Tube |
| Product Type | Rectangular Steel Tube (Welded / ERW) |
| Steel Grade | Q195, Q215, Q235, Q345 |
| Standard | ASTM, ASTM A213, DIN EN 10217-1 |
| Section Shape | Rectangular |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Slightly Oiled |
| Tolerance | ±1% |
| Length | Customers’ Request |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Application | Fluid Pipe, Boiler Pipe, Drill Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Steel frame structures, column systems, beam assemblies for warehouses and logistics centers |
| Industrial Infrastructure | Structural support frames for processing plants, conveyor systems, and equipment platforms |
| Energy & Petrochemical | Gas conveyance lines, chemical fertilizer pipe networks, and fluid transfer systems |
| Civil Engineering | Bridge support members, infrastructure framework, and foundation pile casings |
What Negative Tolerance Really Costs on a Q345 Rectangular Tube Order
A ±1% tolerance window separates compliant structural delivery from a rejected container at the destination port.
When overseas buyers source Q235 Q345 ERW Rectangular Steel Tube from Chinese fabricators, the gap between theoretical weight and actual measured weight becomes the first checkpoint for third-party inspectors. Wall thickness pushed beyond permissible negative tolerance triggers dimensional rejection — not because the tube cannot carry load, but because the mill test certificate no longer matches the physical product. On Middle East and Southeast Asian projects, I have seen entire shipments held at the discharge port because the inspector’s ultrasonic gauge readings fell outside the ±1% band declared on the packing list. The cost is not just the re-inspection fee; it is the crane standing idle, the schedule slip, and the conversation with the main contractor. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed hollow sections]
How Q235 and Q345 Grades Align with Structural Frame Demands
For commercial building frames and industrial platform structures, Q235 Q345 ERW Rectangular Steel Tube delivers the yield strength progression that structural engineers specify — Q235 for secondary members and bracing where load demands remain moderate, Q345 for primary columns and long-span beams where higher yield capacity reduces section size and self-weight. The ERW process produces a continuous longitudinal weld seam that, when controlled under certified welding procedures, maintains weld integrity comparable to the parent metal. Hot rolled surface with slight oiling provides baseline corrosion protection during ocean transit, while the ±1% dimensional tolerance ensures that connection plates and bolt holes align on-site without field reaming.
Engineering Compliance and Certification Pathways
Structural rectangular tubes destined for EU markets must conform to EN 10219 for cold-formed welded structural hollow sections, while North American projects typically reference ASTM A500 or ASTM A213. The Q-series grades (Q195 through Q345) map broadly to S235/S355 under EN standards and A500 Grade B/C under ASTM, but equivalence is not automatic — chemical composition and mechanical property test reports must demonstrate compliance with the specific standard cited in the purchase order. For projects in the Middle East and Africa, ASTM compliance combined with third-party inspection (SGS/BV) satisfies most EPC procurement specifications. Custom length cutting and CNC punching before shipment reduce on-site secondary processing, which matters when labor costs at the destination exceed the fabrication premium paid in China. [NEED_CITE: steel grade equivalence mapping between GB Q-series and EN/ASTM standards]
Understanding ERW Process and Surface Treatment Selection
The ERW (Electric Resistance Welded) process forms the rectangular section by cold-forming a flat strip and welding the longitudinal seam through electrical resistance heating — no filler metal is added, which keeps the weld zone narrow and the dimensional profile consistent. For Q235 and Q345 grades, this process suits structural applications where internal pressure is not the primary design driver, unlike seamless tubes used in high-pressure boiler or hydraulic systems. The hot rolled finish with slight oiling is the standard delivery condition for structural and fluid conveyance use; it protects the surface during storage and transit without adding the cost of galvanizing or multi-layer coating systems. When the project environment demands enhanced corrosion resistance — coastal industrial plants, chemical processing facilities — the tubes can be shot blasted and painted to project specification before dispatch, leveraging the integrated fabrication capability rather than outsourcing coating separately.
Hidden Costs When Material Traceability Breaks Down
Procuring Q235 Q345 ERW Rectangular Steel Tube without verified mill test certificates creates a cascade of downstream risk. If the heat number on the tube cannot be traced back to the original steelmaking batch, the entire delivery becomes uncertified — meaning the structural engineer cannot sign off, the building inspector cannot issue occupancy, and the project owner faces liability exposure. Tubes sourced from traders who blend material from multiple mills without proper documentation may meet dimensional specs on the outside but fail chemical composition tests under spectrographic analysis. The hidden cost is not the price difference between certified and uncertified material; it is the project delay, the re-order cycle, and the reputational damage with the end client. [NEED_CITE: material traceability requirements under EN 1090 structural steel fabrication standard]
Why Sourcing from an Integrated Mill-Fabricator Changes the Equation
XJY Structure operates as the dedicated structural steel fabrication division of Shandong Xin Jiyuan Special Steel Tube Co., backed by an own steel production facility with three production lines and over 2,800 raw material specifications in stock. This vertical integration means the Q235 Q345 ERW Rectangular Steel Tube you order comes from a single material source — the same mill that produces the raw strip also controls the ERW forming, welding, and finishing processes, eliminating the traceability gap that occurs when fabricators source steel from third-party suppliers. Certified welding procedures (AWS/EN) and qualified welders handle all fabrication services including CNC cutting, drilling, bending, and MIG/MAG/SAW welding. Every shipment includes a complete quality documentation package: WPS, PQR, weld maps, dimensional inspection reports, and coating reports — not as an afterthought, but as a standard deliverable built into the production workflow. Professional loading plans for oversized fabricated components ensure that heavy rectangular tubes and assembled frames reach the destination without transit damage.
Documentation & Compliance
- Mill Test Certificate documenting Q235/Q345 chemical composition and mechanical properties per ASTM A213 and DIN EN 10217-1, traceable by heat number
- CE certification for EN 10219 cold-formed structural hollow sections, required for EU market customs clearance and project acceptance
- ISO 9001 quality management system certificate covering the integrated steel production and fabrication workflow
- SGS or BV third-party inspection report available upon request, covering dimensional checks, weld seam NDT, and coating thickness verification
- Full material traceability from steelmaking heat number through ERW forming to finished tube, with test reports matched to each bundle
- Export documentation package including commercial invoice, packing list, bill of lading, and certificate of origin for destination customs clearance
Packaging, Loading & Delivery
- Q235/Q345 rectangular tubes bundled with high-tensile steel strips at regular intervals, with edge protectors to prevent coating damage during handling and ocean transit
- Hot rolled surfaces with slight oiling preserved through waterproof wrapping for containerized shipments, preventing surface oxidation during extended sea freight
- Custom length cutting available per project specification, with cut ends deburred and marked for on-site identification, reducing secondary processing at destination
- Container loading plans optimized for rectangular tube geometry, maximizing weight utilization within 20ft and 40ft containers while maintaining weight distribution for crane offloading
- Heat number and steel grade stenciled on each bundle with weather-resistant paint, ensuring traceability verification at the project site without unpacking
- FOB, CIF, and DDP shipping terms available with professional oversized cargo loading and lashing for fabricated structural assemblies
How to Initiate Your Procurement Inquiry
Submit your project drawings (PDF/DWG), steel grade requirements (Q235/Q345), dimensional specifications, target standards (ASTM/EN), and quantity to receive a detailed quotation within 24 hours — including material cost, fabrication services, surface treatment, packing, and shipping. Our engineering team will review shop drawings, confirm material availability from our 2,800+ specification inventory, and provide a production schedule aligned with your project timeline. Confirm third-party inspection requirements and certification documentation needs at the inquiry stage to ensure all compliance deliverables are integrated into the production plan from the outset.
Frequently Asked Questions
Q: How do Q235 and Q345 grades compare to S235JR/S355JR or ASTM A500?
A: Q235 broadly corresponds to S235JR under EN standards and ASTM A500 Grade B, while Q345 aligns with S355JR and ASTM A500 Grade C in terms of yield strength classification. However, equivalence must be verified through chemical composition and mechanical property test reports specific to the production batch — direct substitution without documented compliance is not recommended for certified structural applications.
Q: Can you provide Mill Test Certificates and arrange third-party inspection?
A: Yes. Every shipment of Q235 Q345 ERW Rectangular Steel Tube includes a Mill Test Certificate documenting chemical composition and mechanical properties, traceable by heat number. SGS or BV third-party inspection can be arranged upon request to cover dimensional verification, weld seam testing, and coating inspection before shipment.
Q: What is the minimum order quantity and can you produce non-standard dimensions?
A: The minimum order quantity is 5 tons. Custom dimensions beyond standard size ranges can be produced based on project drawings and specifications, with shop drawing approval required before fabrication begins. Our integrated mill facility supports over 2,800 raw material specifications to accommodate non-standard requirements.
Q: What surface treatment options are available for different project environments?
A: Standard delivery is hot rolled with slight oiling for corrosion protection during transit. For enhanced corrosion resistance, tubes can be shot blasted and painted to project specification, or galvanized for long-term exposure in aggressive environments. Surface treatment selection depends on the project’s environmental conditions and design service life.
Q: Do your products meet EN 10219 standards for EU projects?
A: Yes. Q235 Q345 ERW Rectangular Steel Tube can be produced and certified to meet EN 10219 requirements for cold-formed welded structural hollow sections, with CE marking and full documentation for EU market customs clearance and project acceptance.
Request Your Q235 Q345 ERW Rectangular Steel Tube Quotation
Send your project specifications, drawings, and quantity requirements to receive a detailed quotation with Mill Test Certificate documentation within 24 hours.
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
