Description
Factory-direct pricing, no middlemen markup — every Q195-Q345 seamless square steel tube rolls off our own JIS G3466-certified lines with full mill test traceability before it leaves Jinan.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195/Q235/Q345 Seamless Square Steel Tube |
| Product Type | Seamless Square Steel Tube (SHS) |
| Steel Grade | Q195, Q215, Q235, Q345, S235JR, S275JR, S355JR |
| Standard | JIS G3466, CE, ISO 9001, API |
| Section Shape | Square |
| Outer Diameter or Side Length | Customization available |
| Wall Thickness | Customization available |
| Length | 1–12 m (standard 6 m / 12 m) |
| Technique | Seamless / Cold Rolled / Hot Rolled |
| Surface Treatment | Black Painted / Cold Rolled / Hot Rolled |
| Tolerance | ±1% |
| Ends | Plain ends (default) |
| Application | Construction / Mechanical engineering / Steel structure projects / Shipbuilding / Solar power brackets / Power engineering / Agricultural and chemical machinery / Glass curtain walls / Car chassis / Airports |
| MOQ | 10 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Steel structure frames for industrial plants and infrastructure projects |
| Construction Companies | High-rise building columns, bridge support structures, and foundation piling |
| Machinery Manufacturers | Precision tubes for hydraulic cylinders, conveyor frames, and equipment bases |
| Shipbuilding | Deck structures and internal framing for marine vessels |
| Solar Power | Ground-mounted solar bracket systems and support purlins |
| Power Engineering | Transmission tower bracing and substation structural members |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A ±1% tolerance on a seamless square steel tube is the difference between passing third-party inspection and watching an entire batch sit at the port for weeks.
I watched a Lagos job site reject a full container of SHS because the wall thickness ran negative beyond acceptable limits. The third-party inspector flagged it, customs held the cargo, and the contractor paid demurrage for fourteen days before replacement tubes arrived. That kind of specification gap doesn’t just delay a schedule — it erodes the margin on the whole project. When you source a Q235 seamless square steel tube supplier who controls the rolling process in-house and runs every heat through a physical and chemical lab before it leaves the mill, the paperwork matches the steel and the steel matches the drawing. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching JIS G3466 Seamless Tubes to Structural Load Paths
Seamless square steel tubes produced under JIS G3466 carry uniform grain structure around the entire cross-section, which matters when the tube serves as a compression member in a braced frame or a load-bearing column. The absence of a weld seam eliminates the weakest point that ERW tubes present under cyclic loading. For EPC contractors framing industrial buildings or machinery manufacturers building conveyor supports, this Q195-Q345 seamless square steel tube supplier delivers tubes that hold dimensional accuracy through cutting, drilling, and welding without unexpected distortion.
Engineering Compliance and Surface Protection Choices
Structural engineers specifying these tubes for outdoor or marine-adjacent projects need to weigh the bare or black-painted finish against the corrosion environment the tube will face. Hot-rolled surface condition accepts field-applied coatings well, while cold-rolled finish provides a smoother base for powder coating or galvanizing after fabrication. For projects targeting EU markets, CE certification under EN 10210/10219 confirms the tubes meet European hollow section standards for structural use. [NEED_CITE: steel grade equivalence between JIS, EN, and ASTM systems] Custom cut-to-length service means site crews receive tubes ready to weld, reducing secondary cutting waste and keeping the project on schedule.
Steel Grade Selection and Manufacturing Process
The Q-series grades — Q195 through Q345 — follow the Chinese yield-strength designation system, where the number indicates minimum yield strength in MPa. Q235 remains the workhorse grade for general structural frames, while Q345 steps up for heavier load paths where higher strength reduces section size and overall weight. The S-series equivalents (S235JR, S275JR, S355JR) align with European EN standards, making cross-referencing straightforward for international projects. [NEED_CITE: structural steel grade comparison across international standards] Seamless manufacturing eliminates the longitudinal weld seam found in ERW tubes, giving uniform mechanical properties in all directions — critical when the tube faces multi-axial loading in a space frame or truss system. Wall thickness customization with ±1% precision ensures the theoretical weight calculation matches the actual delivered weight, so structural engineers can trust their load tables.
Hidden Costs When Material Traceability Fails
Procuring tubes without verified mill test certificates means the contractor cannot prove steel grade compliance during project handover. A batch that tests below specified yield strength during第三方 re-inspection triggers full rejection — not partial. The replacement order adds weeks to the critical path, and the original material becomes scrap value at best. Certification gaps also create customs clearance failures in markets requiring CE marking or SGS verification, turning a routine shipment into a bonded-warehouse holding. [NEED_CITE: consequences of missing mill test certificates in international steel procurement]
Why Procurement Teams Choose Our Mill
Our three dedicated production lines cover over 2,800 specifications in square and rectangular hollow sections, with wall thicknesses reaching 40mm — meaning non-standard sizes that other mills quote as “special order” ship from our regular schedule. The in-house physical and chemical laboratory tests every heat before it moves to the finishing line, so the mill test certificate reflects actual production data rather than a generic template. We hold 41 invention patents, including proprietary sharp-corner rectangular tube technology, and our products carry CE, ISO 9001:2015, Singapore FPC, and SGS/BV verification. Factory-direct pricing eliminates trading-company margins, and our export team handles documentation, container optimization, and door-to-door logistics to 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Q235 and Q345 chemical composition and mechanical properties per JIS G3466 for each heat number
- CE certificate confirming compliance with EN 10210/10219 for structural hollow sections exported to European markets
- ISO 9001:2015 quality management certificate covering the full production process from raw material incoming inspection to final dimensional check
- SGS or BV third-party inspection report available upon request for projects requiring independent verification before shipment
- Full material traceability by heat number linking each tube bundle to its original mill test certificate and chemical analysis
- Export customs documents including packing list, bill of lading, and certificate of origin formatted for destination-country clearance
Packaging, Loading & Delivery
- Seamless square steel tubes bundled with steel strips and edge protectors to prevent surface damage to the black-painted or hot-rolled finish during ocean transit
- Custom cut-to-length tubes (1–12 m) loaded with optimized container stowage plans that maximize payload for 6 m and 12 m standard lengths
- Heat number and steel grade stenciled on each bundle for site identification and traceability verification upon arrival
- Seaworthy packaging with waterproof wrapping available for Q195-Q345 tubes destined for high-humidity or tropical port environments
- FOB, CIF, and DDP shipping terms with professional loading supervision to ensure weight distribution meets container safety standards
- Door-to-door logistics coordination for EPC projects requiring direct delivery to inland construction sites or fabrication yards
Getting Your Quote and Mill Test Certificate Started
Send your specification sheet — including steel grade, side length, wall thickness, length, quantity, and destination port — and our team returns a detailed quotation within 12 hours with pricing, production lead time, and applicable certification options. For non-standard sizes or custom cut lengths outside the 1–12 m range, we provide a feasibility review and tooling timeline before you commit. Confirm your required mill test certificate format and any third-party inspection preferences, and we build those into the production plan from day one.
Frequently Asked Questions
Q: What is the difference between Q235 and S235JR for the same structural application?
A: Q235 and S235JR share similar minimum yield strength levels, but they follow different standard systems — Q235 follows Chinese GB standards while S235JR follows European EN 10025. For projects in Europe or requiring CE marking, S235JR documentation aligns directly with local engineering codes. We supply both grades and can provide equivalence documentation for cross-standard projects.
Q: Can you provide third-party inspection before shipment?
A: Yes. SGS and BV third-party inspections are available upon request. The inspector verifies dimensions, wall thickness, surface condition, and reviews the mill test certificate against the purchase order before the container is sealed.
Q: What is the minimum order quantity for custom non-standard sizes?
A: The standard MOQ is 10 tons. For custom non-standard side lengths or wall thicknesses outside our regular 2,800+ specification range, we review the tooling requirements and confirm feasibility before quoting.
Q: How do you ensure wall thickness stays within ±1% tolerance?
A: Every tube passes through our in-house physical and chemical laboratory during production. Ultrasonic thickness testing confirms dimensional accuracy before the tube moves to cutting and bundling. The mill test certificate records actual measured values for each heat.
Q: What surface treatment options are available for outdoor structural use?
A: Standard options include black painted, cold rolled, and hot rolled finishes. For enhanced corrosion protection, we can coordinate hot-dip galvanizing or 3PE coating as a secondary process after the seamless tube is produced.
Secure Your Q195-Q345 Seamless Square Steel Tube Quote Today
Submit your specifications — steel grade, dimensions, quantity, and destination — to receive a detailed quotation with mill test certificate options within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjysteel.com
Website: www.sdxjysteel.com
