Description
Factory-Direct ERW Square Steel Tubes — Every Q235, Q345, and S355JR tube leaves our mill with an in-house lab report, shipped without middlemen markup.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235/Q345/S355JR Square Steel Tube |
| Product Type | Square Steel Tube (ERW / Hot Rolled) |
| Steel Grade | Q195, Q235, Q345, S235JR, S275JR, S355JR |
| Standard | ASTM, API |
| Section Shape | Square |
| Size Range | Square section (specific dimensions available upon request) |
| Wall Thickness | 0.9 mm and above (up to 40 mm) |
| Length | 6 m / 6.4 m / 12 m |
| Technique | ERW (Electric Resistance Welded) / Hot Rolled |
| Surface Treatment | Hot Rolled |
| Tolerance | ±1% |
| Ends | Plain ends |
| Application | Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants and warehouse buildings |
| Construction Companies | Building columns, beam-to-column connections, and scaffolding systems |
| Machinery Manufacturers | Conveyor frames, equipment bases, and hydraulic support structures |
| Petrochemical Projects | Gas transport lines, chemical fertilizer piping, and process pipe racks |
| Infrastructure Developers | Bridge support structures and utility pole foundations |
What ±1% Wall Tolerance Means When Your Structural Frame Has 200 Connection Points
Tight tolerance eliminates on-site rework and prevents load-bearing miscalculations across an entire project.
When wall thickness drifts beyond ±1%, bolt holes no longer align, gusset plates sit at angles, and structural engineers cannot verify load paths. I have seen containers held at port because a third-party inspector measured wall thickness deviation outside ASTM tolerance — the entire shipment was rejected, the project delayed weeks, and the procurement team had to source replacement tubes from a different continent. [NEED_CITE: ASTM A500 dimensional tolerance requirements for structural hollow sections]
An ERW square steel tube supplier who controls tolerance at the mill — not by sorting after production — ensures that every Q235, Q345, and S355JR tube meets the same dimensional standard your engineer specified.
How Q235 and S355JR Square Tubes Match Structural Load Requirements
Structural frames demand steel grades that balance yield strength with weldability. Q235 serves general construction where moderate load capacity suffices, while S355JR delivers higher yield strength for heavy-duty industrial frames and bridge supports. The ERW square steel tube production process creates a continuous weld seam with uniform microstructure, ensuring consistent mechanical properties across all four sides — critical when tubes serve as load-bearing columns or beam-to-column connections. Our mill produces these grades in wall thicknesses from 0.9 mm up to 40 mm, covering everything from light gauge framing to heavy structural members.
Engineering Compliance and Certification Pathways
Projects in the European Union require CE certification under EN 10210 or EN 10219 for structural hollow sections. Without this marking, customs authorities will not clear the shipment, regardless of material quality. [NEED_CITE: EN 10219 cold-formed welded structural hollow sections compliance] Our Q345 and S355JR tubes carry Lloyd’s Register EU CE certification, and every heat number is traceable through our in-house physical and chemical laboratory reports. For North American projects, ASTM compliance documentation accompanies each shipment. The 6 m, 6.4 m, and 12 m standard lengths reduce on-site cutting waste, while our bending, cutting, and punching services deliver project-ready components.
Steel Grade Selection and ERW Process Fundamentals
The Q-series (Q195, Q235, Q345) follows Chinese GB standards, where the number indicates minimum yield strength in MPa. The S-series (S235JR, S275JR, S355JR) follows European EN standards with similar yield strength designation. ASTM A500 Grade B and C provide equivalent coverage for North American specifications. ERW (Electric Resistance Welded) square tubes are formed from hot-rolled coil, with the weld seam created by electrical resistance heating rather than filler metal — this produces a clean, continuous joint suitable for structural applications. Hot-rolled surface treatment leaves a mill scale finish that accepts paint or galvanizing without additional surface preparation. Wall thickness tolerance of ±1% ensures that theoretical weight calculations match actual delivered weight, preventing cost overruns on large-tonnage orders.
Hidden Costs of Procuring Non-Compliant Square Tubes
Ordering square tubes without verified mill test certificates creates downstream risks: customs delays due to missing CE or ASTM documentation, structural inspection failures when material properties cannot be traced to heat numbers, and project acceptance rejection when wall thickness falls outside specified tolerance. [NEED_CITE: material traceability requirements for structural steel certification] An ERW square steel tube supplier who provides original mill test certificates with chemical composition and mechanical properties for every heat number eliminates these risks. The cost difference between certified and uncertified tubes is marginal compared to the expense of container detention, replacement sourcing, and project delays.
Why Procurement Teams Choose Xin Jiyuan for ERW Square Steel Tubes
We operate three dedicated production lines with in-house physical and chemical laboratories — every tube undergoes incoming, in-process, and final inspection before loading. Our 41 patented technologies include proprietary sharp-corner rectangular tube manufacturing, filling gaps in global market specifications. With 2,800+ models available and wall thickness up to 40 mm, we cover standard and non-standard dimensions without minimum order penalties. Lloyd’s Register EU CE (EN 10210/10219), ISO 9001:2015, Singapore FPC, and SGS/BV verification ensure customs clearance in 50+ countries. Professional loading plans optimize container utilization for 6 m, 6.4 m, and 12 m lengths, reducing freight cost per ton.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/S355JR chemical composition and mechanical properties per ASTM and EN standards
- CE certificate (EN 10210/EN 10219) for European Union customs clearance and structural compliance
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available for independent quality verification
- Material traceability by heat number linking each tube to original mill test certificate
- Customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Hot rolled square tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Plain end tubes packed in seaworthy bundles with waterproof wrapping for Q235/Q345/S355JR grades
- Container loading optimized for 6 m, 6.4 m, and 12 m lengths to maximize payload per shipment
- Heat number and steel grade marked on each tube for on-site identification and traceability
- FOB, CIF, and DDP shipping terms available with door-to-door logistics to 50+ countries
- Custom cutting and bending services available to deliver project-ready components
Ready to Source ERW Square Steel Tubes with Full Certification?
Submit your specifications — steel grade, dimensions, wall thickness, quantity, and destination port — to receive a detailed quotation including unit price, delivery timeline, and applicable mill test certificates. Our team responds within 12 hours with pricing, certification availability, and loading plans.
Request Your ERW Square Steel Tube Quotation
Send specifications via email to admin@sdxjysteel.com or contact us at +86 188 5315 7756 (WhatsApp/WeChat available) to receive pricing and mill test certificate samples.
Frequently Asked Questions
Q: What is the difference between Q345 and S355JR steel grades for square tubes?
A: Q345 follows Chinese GB standards while S355JR follows European EN standards. Both offer similar yield strength levels suitable for structural applications. Our mill produces both grades with full certification documentation for international projects.
Q: Can you provide third-party inspection for ERW square steel tubes?
A: Yes, SGS and BV third-party inspection is available for independent quality verification. We also provide original mill test certificates from our in-house laboratory for every heat number.
Q: What wall thickness range is available for square steel tubes?
A: We produce square tubes with wall thickness from 0.9 mm up to 40 mm, covering light gauge framing to heavy structural members. Custom non-standard dimensions are available upon request.
Q: Do your square tubes carry CE certification for European projects?
A: Yes, our square tubes carry Lloyd’s Register EU CE certification under EN 10210 and EN 10219 standards, ensuring customs clearance and structural compliance for European Union projects.
Q: What is the minimum order quantity for ERW square steel tubes?
A: The minimum order quantity is 1 ton, allowing flexibility for both project procurement and trial orders.
Get Factory-Direct ERW Square Steel Tubes with Full Certification
Email admin@sdxjysteel.com or WhatsApp +86 188 5315 7756 with your specifications to receive a quotation and mill test certificate within 12 hours.
