Description
Integrated Mill-to-Tube Supply — Q235 and Q345 ERW welded square rectangular steel tube manufactured from our own steel production lines with full material traceability from coil to finished section.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345 Welded Square and Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (ERW) |
| Steel Grade | Q195, Q215, Q235, Q345 |
| Standard | ASTM A213, DIN EN 10217-1 |
| Section Shape | Square / Rectangular |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Slightly Oiled |
| Tolerance | ±1% |
| Length | 6m / 6.4m / 12m (Customizable) |
| 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 |
|---|---|
| Construction & Infrastructure | Building frames, warehouse structures, scaffolding systems, conveyor supports |
| Industrial Facilities | Machinery frames, equipment bases, platform structures, pipe rack supports |
| Oil & Gas | Gas transport pipelines, oil field structural supports, drilling platform frameworks |
| Chemical Processing | Chemical fertilizer plant structures, fluid transport systems, process pipe supports |
| Energy & Power | Boiler support structures, solar panel mounting frames, power transmission tower components |
What Wall-Thickness Tolerance Costs on a Q235 Q345 ERW Welded Square Rectangular Steel Tube Order
Tolerance deviations compound across every beam connection in a structural frame.
When ERW welded square rectangular steel tube arrives at site with wall thickness below specification, the structural engineer’s load calculations become invalid. A ±1% tolerance maintained throughout production ensures each Q235 or Q345 section performs as designed. We have seen projects where negative tolerance accumulation forced complete frame replacement because connection plates no longer aligned with reduced wall sections. Material certification gaps between coil heat numbers and finished tube documentation create customs clearance delays in EU markets requiring EN compliance verification [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements].
How Q235 and Q345 Grades Match Structural Frame Requirements
The Q235 Q345 ERW welded square rectangular steel tube serves distinct load-bearing roles in structural applications. Q235 provides adequate strength for secondary structures, scaffolding, and non-critical frames where cost optimization matters. Q345 delivers higher yield strength for primary load-bearing columns, crane beams, and seismic-resistant frames in warehouse and industrial building projects. Our ERW welding process ensures seam integrity matching base metal strength, while the ±1% dimensional tolerance guarantees that connection details fabricated to drawing specifications fit without on-site modification. The vertically integrated production from raw steel coil through tube forming eliminates material sourcing gaps that create traceability problems during third-party inspection.
Compliance Requirements for International Structural Projects
Structural steel projects in EU markets require EN 10219 compliance with CE marking for load-bearing hollow sections, while North American projects specify ASTM standards with mill test certificates showing chemical composition and mechanical properties per heat number [NEED_CITE: steel grade equivalence between Chinese GB standards and international EN/ASTM systems]. The Q235 grade corresponds roughly to S235 in EN standards, while Q345 aligns with S355 specifications, though exact equivalence requires project engineer verification. Surface treatment selection between hot rolled finish and oiled protection depends on transport duration and site storage conditions before final coating application. Custom length options at 6m, 6.4m, or 12m reduce on-site cutting waste and labor costs while maintaining dimensional accuracy for prefabricated assembly sequences.
Understanding ERW Welding Process and Steel Grade Selection
Electric Resistance Welding creates the longitudinal seam in Q235 Q345 ERW welded square rectangular steel tube by passing high-frequency current through steel strip edges, generating heat that fuses the material under pressure without filler metal. This process produces a weld seam with mechanical properties matching the base metal when properly controlled, making ERW tubes suitable for structural applications where seam strength matters. The Q-series steel grades (Q195, Q215, Q235, Q345) follow Chinese GB standards where the number indicates minimum yield strength in MPa, providing a straightforward selection method for engineers familiar with this specification system. Hot rolled surface treatment leaves a mill scale layer that requires removal before painting, while slight oiling provides temporary corrosion protection during ocean transit to Southeast Asian and Middle Eastern job sites. Wall thickness tolerance directly affects theoretical weight calculations used in project costing, making ±1% control essential for accurate material procurement and structural analysis.
Hidden Costs of Incorrect Grade Selection and Tolerance Failure
Specifying Q235 when structural calculations require Q345 creates safety margins that disappear under actual load conditions, while ordering Q345 for non-critical applications wastes project budget on unnecessary strength. Material certificates showing chemical composition outside standard ranges trigger rejection during third-party inspection, forcing replacement orders that delay project schedules by weeks. Negative wall thickness tolerance beyond ±1% reduces load-bearing capacity below engineering specifications, requiring structural reassessment or complete section replacement after installation. Missing heat number traceability between mill test certificates and delivered tubes creates customs clearance failures in markets requiring EN 1090 execution class documentation [NEED_CITE: EN 1090 structural steel fabrication execution class requirements].
Why Project Procurement Teams Choose Our Integrated Production
Our own steel production facility with three production lines manufactures the raw material for Q235 Q345 ERW welded square rectangular steel tube, eliminating the gap between material supplier and fabricator that creates quality control uncertainty. Over 2,800 specifications in our inventory system cover the dimensional range needed for medium-to-large structural projects, while our fabrication workshop provides cutting, drilling, bending, and welding services that reduce secondary processing requirements at your site. Certified welding procedures per AWS and EN standards with qualified welders ensure that any fabrication work maintains the same quality level as the base tube production. Complete quality documentation packages including WPS, PQR, weld maps, dimensional inspection reports, and coating reports satisfy the documentation requirements for international projects across EU, Middle East, Southeast Asia, and African markets. Professional loading planning for oversized and heavy fabricated components prevents transport damage and ensures site delivery in condition ready for installation.
Documentation & Compliance
- Mill test certificate documenting Q235 and Q345 chemical composition and mechanical properties per heat number according to DIN EN 10217-1
- CE certificate confirming EN 10219 compliance for structural hollow sections required in EU construction projects
- ISO 9001 quality management system certificate covering the integrated steel production and tube fabrication process
- SGS or BV third-party inspection report verifying dimensional tolerance, weld seam quality, and surface treatment condition
- Material traceability documentation linking each Q235 Q345 ERW welded square rectangular steel tube bundle to specific coil heat numbers
- Complete customs documentation package including packing list, bill of lading, and certificate of origin for international shipment clearance
Packaging, Loading & Delivery
- Q235 Q345 ERW welded square rectangular steel tube bundled with steel strips in seaworthy packaging suitable for 6m, 6.4m, and 12m lengths
- Slightly oiled surface treatment provides corrosion protection during ocean transit to Southeast Asian and Middle Eastern project sites
- Container loading optimization for 12m length tubes maximizes payload per shipment while protecting tube ends from impact damage
- Custom cutting to project-specified lengths reduces on-site waste and labor costs for prefabricated structural assembly
- Heat number and steel grade identification marked on each bundle ensures traceability verification during site inspection
- FOB, CIF, and DDP shipping terms available with professional loading planning for oversized structural components
Getting Your Q235 Q345 ERW Welded Square Rectangular Steel Tube Quote Started
Submit your project drawings in PDF or DWG format along with steel grade requirements, dimensional specifications, quantity, and destination port to receive a detailed quotation within 24 hours including material cost, fabrication services, coating, packing, and shipping. Our engineering team reviews shop drawings and provides material optimization recommendations before production begins, ensuring the Q235 Q345 ERW welded square rectangular steel tube specifications match your structural design requirements. Confirm third-party inspection requirements and certification documentation needs for your specific market to ensure smooth customs clearance and project approval.
Request Technical Quotation with Mill Test Certificate
Share your project specifications and steel grade requirements to receive detailed pricing and complete quality documentation for your Q235 Q345 ERW welded square rectangular steel tube order.
Contact Information:
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
Frequently Asked Questions
Q: What is the difference between Q235 and Q345 steel grades for square and rectangular tubes?
A: Q235 provides minimum yield strength of 235 MPa suitable for secondary structures and non-critical applications, while Q345 delivers 345 MPa yield strength for primary load-bearing structural members. The selection depends on your structural engineer’s load calculations and the specific application requirements for your project.
Q: Can you provide third-party inspection and material certification for EU and US projects?
A: Yes, we arrange SGS or BV third-party inspection covering dimensional verification, weld seam quality, and surface treatment condition. Complete mill test certificates with chemical composition and mechanical properties per heat number are provided, along with CE certification for EN 10219 compliance required in European construction projects.
Q: What is the MOQ for custom-length welded square and rectangular tubes?
A: The minimum order quantity is 5 tons for Q235 Q345 ERW welded square rectangular steel tube. Custom lengths of 6m, 6.4m, or 12m are available within this quantity, and our engineering team can provide material optimization recommendations to minimize waste for your specific project requirements.
Q: How do you ensure weld seam quality in ERW tubes?
A: Our ERW welding process uses high-frequency electric resistance welding with certified welding procedures per AWS and EN standards. In-process dimensional checks and non-destructive testing verify weld seam integrity matches base metal strength, with complete quality documentation including WPS, PQR, and weld maps provided for each production batch.
Q: What surface treatment options are available for welded square and rectangular tubes?
A: Standard surface treatment includes hot rolled finish with mill scale or slight oiling for temporary corrosion protection during transit. Additional processing services include shot blasting and painting preparation for projects requiring final coating application at the installation site.
Get Your Project-Specific Quotation Today
Send your structural steel requirements including drawings, steel grades, quantities, and destination to receive comprehensive pricing with complete mill test certificates and quality documentation within 24 hours.
Contact Information:
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
