Description
Factory-Direct Seamless Square Tubes — Q195–Q345 grades rolled from solid billets with no weld seams, shipped with original mill test certificates for every heat number.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195-Q345 Seamless Square Steel Tube |
| Product Type | Seamless Square Steel Tube / Hollow Section |
| Steel Grade | Q195, Q235, Q345, 10#, 20#, 45#, S235JR, S275JR, S355JR, SS400, Gr.B, Gr.50 |
| Standard | ASTM, EN, GB, JIS |
| Section Shape | Square |
| Wall Thickness | 0.9 mm |
| Length | 6 m / 6.4 m / 12 m |
| Technique | Seamless (pierced solid billet, hot rolled / cold rolled / cold drawn) |
| Surface Treatment | Hot Rolled, Non-oiled |
| Tolerance | ±1% |
| Ends | Plain (default) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Application | Construction Structure, Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Load-bearing column frames, portal structures for warehouses, bridge support piers |
| Industrial Scaffolding | Vertical standards, ledger connections, heavy-duty shoring towers |
| Petrochemical & Energy | Hydraulic piping manifolds, gas distribution headers, chemical fertilizer feed lines |
| Machinery & Equipment | Machine base frames, conveyor support structures, crane boom sections |
What Negative Tolerance Really Costs on a 0.9 mm Wall Order
A ±1% tolerance on a 0.9 mm wall means the difference between passing structural inspection and getting the entire container rejected at port.
I’ve seen project buyers lose weeks because the actual wall thickness drifted beyond acceptable limits — and the mill certificates looked perfect on paper. When you’re ordering Low Carbon Seamless Square Steel Tube for Construction Structure Supplier applications with thin-wall sections, every micron matters. Inconsistent material properties mean your fabricator can’t predict weld behavior, and missing traceability means customs holds your cargo before it ever reaches the job site. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
How Seamless Manufacturing Matches Structural Frame Demands
The pierced billet process eliminates the longitudinal weld seam that becomes the weakest point under cyclic loading. For construction frames carrying dynamic loads from cranes or vibrating equipment, this uniform wall structure distributes stress evenly across all four faces. Our Q195–Q345 grades offer the weldability your site crews need while maintaining the dimensional stability that ±1% tolerance guarantees — critical when you’re bolting connections that must align within millimeters across 12-meter spans.
Meeting EN 10219 and ASTM A500 for International Projects
European specifiers calling for S235JR or S355JR under EN 10219 need more than a mill certificate — they need chemical composition reports matching the heat number stamped on every tube. [NEED_CITE: steel grade equivalence between GB Q-series and EN S-series standards] Our in-house lab tests each batch for mechanical properties before release, and we arrange SGS or BV third-party inspection when your project demands independent verification. The hot-rolled surface finish arrives non-oiled and ready for welding, punching, or bending without additional preparation — saving your fabricator time and avoiding coating compatibility issues.
Why Q195 Through Q345 Cover Most Structural Applications
The Q-series grades represent yield strength thresholds in the Chinese GB system, where Q195 suits light framing and Q345 handles primary structural members. When your drawings call for S235JR or S355JR, the carbon-manganese chemistry delivers comparable performance with proven weldability using standard E70XX electrodes. The 10#–45# carbon steels fill the gap for machined components requiring higher hardness, while SS400 and Gr.B/Gr.50 serve Japanese and American specifications respectively. This grade coverage means your procurement team sources all structural tubes from one mill — no splitting orders across five suppliers and managing conflicting delivery schedules.
The Hidden Price of Buying Cheap Hollow Sections
Material substitution without notification turns a routine delivery into a compliance nightmare. Tubes stamped S355JR but testing as Q235 won’t pass structural engineer review, and you’ll pay twice — once for return freight, again for replacement air freight to avoid project delays. Missing mill test certificates mean customs officials hold your container for inspection, charging demurrage by the day. [NEED_CITE: consequences of non-compliant steel materials in structural applications]
Why Project Buyers Source From Our Mill
We run three production lines simultaneously, giving you 20,000+ tons monthly capacity without subcontracting to unknown workshops. Every Low Carbon Seamless Square Steel Tube for Construction Structure Supplier order ships with original mill test certificates showing chemical composition and mechanical properties — not photocopies from trading companies. Our 2,800+ specification inventory means standard sizes ship within days, while custom lengths and non-standard dimensions roll in typical production lead times. The CE certification under EN 10210/EN 10219 and ISO 9001:2015 quality system satisfy European and international project requirements, and our export team handles container loading optimization to maximize payload per shipment — critical when you’re buying by theoretical weight but paying freight by actual volume.
Documentation & Compliance
- Mill test certificate documenting Q195–Q345 chemical composition and mechanical properties per GB/T standards, with heat number traceability
- CE certificate confirming compliance with EN 10210/EN 10219 for structural hollow sections exported to European markets
- ISO 9001:2015 quality management certificate covering the full production process from billet piercing to final inspection
- SGS or BV third-party inspection report available upon request for independent verification of dimensions and material properties
- Material traceability documentation linking each tube bundle to its original heat number and production batch
- Complete customs documentation including packing list, bill of lading, and certificate of origin for smooth port clearance
Packaging, Loading & Delivery
- Seamless square tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit, with 0.9 mm wall thickness requiring careful handling
- Hot-rolled non-oiled surface shipped with anti-rust paper wrapping for 6 m and 12 m lengths, preserving mill finish for welding applications
- Container loading plans optimized for 6 m / 6.4 m / 12 m lengths to maximize payload in 20ft and 40ft containers, reducing per-ton freight costs
- Heat number and steel grade stenciled on each tube end for site identification, matching mill test certificate documentation
- FOB, CIF, and DDP shipping terms available with professional export team handling customs clearance and door-to-door logistics coordination
Getting Your Quote With Full Technical Documentation
Send your specifications — steel grade, wall thickness, length, quantity, and destination port — and receive a detailed quotation within 12 hours including mill test certificate samples and third-party inspection options. Our engineering team reviews your drawings to confirm grade equivalence and tolerance requirements before production begins, ensuring your Low Carbon Seamless Square Steel Tube for Construction Structure Supplier order meets project specifications on first delivery.
Frequently Asked Questions
Q: How do Q195/Q235/Q345 grades compare to S235JR/S355JR under EN 10219?
A: The Q-series follows Chinese GB standards while S-series follows European EN standards, but they represent comparable yield strength levels — Q235 aligns with S235JR, and Q345 aligns with S355JR in structural performance. We provide grade equivalence documentation with every order for international project approval.
Q: Can you arrange third-party inspection before shipment?
A: Yes, SGS and BV inspection services are available upon request. We coordinate the inspection schedule with your chosen agency and provide the inspection report alongside the mill test certificate for complete quality verification.
Q: What is the minimum order quantity for non-standard dimensions?
A: Our flexible MOQ starts from 25 tons for standard specifications. For non-standard sizes requiring custom rolling, we discuss minimum quantities based on production line scheduling and billet availability.
Q: How does theoretical weight invoicing work with ±1% tolerance?
A: We invoice by theoretical weight calculated from nominal dimensions, while actual production maintains ±1% tolerance. This gives you predictable material costs while ensuring dimensional accuracy for structural calculations.
Q: Do you provide cutting and welding preparation services?
A: Yes, our processing services include cutting to exact lengths, beveling for welding preparation, punching for bolt holes, and bending for custom angles — reducing your site fabrication time and material waste.
Request Your Project-Specific Quotation
Submit your steel grade, dimensions, quantity, and destination port to receive competitive factory-direct pricing with complete mill test certificates and CE/ISO compliance documentation.
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
