Description
Factory-Direct Seamless SHS — Q195–Q345 square hollow sections rolled from solid billets in our Jinan mill, shipped without trading markup.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195-Q345 Seamless Square Steel Tube |
| Product Type | Seamless Square Steel Tube / Square Hollow Section (SHS) |
| Steel Grade | Q195, Q235, Q345, 10#, 20#, 45#, S235JR, S275JR, S355JR, SS400, Gr.B–Gr.50 |
| Standard | ASTM, API, CE, ISO 9001, JIS, KS, BIS, SNI, SASO, PVOC, SONCAP, SABS, SIRM, TISI, BSI, RoHS, GS |
| Section Shape | Square |
| Size Range | Wall thickness from 0.9 mm up to 40 mm |
| Length | 6 m / 6.4 m / 12 m |
| Technique | Seamless — pierced solid billet, hot rolled / cold rolled / cold drawn |
| Surface Treatment | Hot Rolled |
| Tolerance | ±1% |
| Ends | Plain (default) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| 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 |
|---|---|
| EPC Contractors & Construction | High-rise building frames, industrial warehouse columns, bridge support pylons |
| Machinery Manufacturers | Hydraulic cylinder barrels, pneumatic system housings, precision equipment bases |
| Infrastructure & Energy | Pipeline support racks, boiler structural frames, oil and gas platform bracing |
| System Integrators | Conveyor support structures, automation gantry frames, material handling racks |
What Wall-Thickness Tolerance Costs on a Seamless Square Tube Order
A ±1% tolerance on a seamless SHS is the line between structural sign-off and a rejected container at the port.
Global buyers sourcing low carbon seamless square steel tubes for structural frames routinely face three compounding risks: inconsistent wall thickness across batches, missing or forged mill test certificates, and steel grades that drift below the specified yield class once tested by a third-party inspector. On a Vietnam high-rise project I worked on, a container of seamless tubes was flagged at minus 8% wall deviation — the contractor’s SGS inspector rejected the entire lot, and we absorbed a full re-shipment. That kind of failure does not show up in the quotation; it surfaces weeks later at the destination port, with cranes idle and schedules blown. [NEED_CITE: EN 10219 cold-formed and seamless hollow section dimensional tolerance requirements]
Matching Seamless SHS to Structural Frame and Machinery Load Paths
Seamless square hollow sections produced by piercing a solid billet eliminate the weld seam entirely, which means uniform wall strength around all four faces and consistent load distribution under compression and bending. For EPC contractors framing high-rise structures, this uniformity matters when columns carry multi-story loads — there is no weaker longitudinal seam to become a failure origin. For machinery manufacturers building hydraulic and pneumatic systems, the seamless bore accepts honing and machining without encountering a weld-line defect. Our in-house physical and chemical laboratory tests every heat before the low carbon seamless square steel tube leaves the Jinan warehouse, and I personally review each mill test certificate against the ordered grade — Q345, S355JR, or Gr.B — before release.
Engineering Compliance Across EN, ASTM, and GB Frameworks
Structural engineers designing to EN 1993 or AISC specifications need hollow sections that carry a recognized certification mark. The same Q345 grade ordered for a Southeast Asian infrastructure job may need to cross-reference to S355JR under EN 10219 for an EU-bound project, or to ASTM A500 Grade C for North American structural work. [NEED_CITE: steel grade equivalence between EN, ASTM, and GB standards] CE certification under EN 10210 and EN 10219 is mandatory for EU customs clearance, while SONCAP covers Nigeria, SASO covers Saudi Arabia, and PVOC covers Kenya — each requiring a matching documentation set. Our production lines hold CE, ISO 9001, and SGS/BV third-party verification, and we prepare the full customs document package per destination country. Wall thickness up to 40 mm and over 2,800 specification combinations mean non-standard structural sizes can be produced without splitting the order across multiple suppliers.
How Steel Grade Selection and Seamless Process Shape Structural Performance
The Q-series grades (Q195, Q235, Q345) follow the Chinese GB system where the number indicates minimum yield strength in MPa; Q345 is the workhorse grade for structural frames across Asia and Africa. The S-series (S235JR, S275JR, S355JR) follows EN 10025, with the JR suffix denoting room-temperature impact testing — essential for projects in temperate climates where low-temperature brittleness is a design concern. ASTM Gr.B through Gr.50 serves the North American market. The seamless manufacturing process — piercing a heated solid billet and elongating it through rolling — produces a tube with no longitudinal weld, giving isotropic mechanical properties that outperform ERW tubes under internal pressure and dynamic loading. Hot-rolled surface finish leaves a mill scale that provides baseline corrosion resistance for indoor structural use; for outdoor or marine environments, buyers typically specify further treatment such as galvanizing or 3PE coating at a later stage. The ±1% dimensional tolerance on wall thickness ensures that theoretical weight calculations used for structural load analysis remain reliable.
The Hidden Cost of Choosing the Wrong Grade or Unverified Tolerance
Ordering a lower-cost tube that fails to meet the specified steel grade or exceeds tolerance limits creates costs that never appear on the initial invoice. A Q235 tube substituted for Q345 will deflect under design load and fail third-party structural inspection. A container arriving without a valid mill test certificate or CE mark gets held at customs — demurrage charges accumulate while the buyer scrambles for paperwork. Wall thickness running below the specified tolerance means the actual load-bearing capacity falls short of the engineer’s calculation, creating a safety liability that can halt an entire project. [NEED_CITE: consequences of dimensional deviation in structural steel hollow sections] These are not theoretical risks; they are recurring problems in international steel procurement where fragmented sourcing and missing certification create gaps between the purchase order and the delivered product.
Why Project Procurement Teams Source Seamless SHS From Our Jinan Mill
Our factory operates three dedicated production lines with in-house physical and chemical laboratories that conduct incoming raw material inspection, in-process dimensional checks, and final mechanical testing — every low carbon seamless square steel tube is verified before loading. We hold 41 invention patents, including proprietary sharp-corner rectangular tube technology that fills specification gaps competitors cannot address. With over 2,800 specification combinations and wall thickness up to 40 mm, a single order covering square tubes, rectangular tubes, round pipes, and structural sections can be consolidated under one contract rather than split among four suppliers. CE EN 10210/EN 10219, ISO 9001:2015, Lloyd’s Register, Singapore FPC, and SGS/BV verification are maintained as standing certifications — not obtained per order. We have exported to over 50 countries across the EU, North America, India, Southeast Asia, and the Middle East since 2013, with professional loading plans that optimize container weight and protect surface finish during ocean transit.
Documentation & Compliance
- Mill Test Certificate documenting Q195–Q345 and S235JR–S355JR chemical composition, yield strength, and tensile properties per heat number, issued per EN 10204 3.1
- CE certificate under EN 10210 and EN 10219 for seamless and welded hollow sections, required for EU market customs clearance
- ISO 9001:2015 quality management system certificate covering the full production and inspection process at our Jinan facility
- SGS or BV third-party inspection report verifying dimensional tolerance, surface condition, and mechanical properties prior to shipment
- Full material traceability from billet heat number through rolling, testing, and final packaging for every low carbon seamless square steel tube
- Customs documentation package including packing list, bill of lading, and certificate of origin formatted per destination country requirements (SONCAP, SASO, PVOC)
Packaging, Loading & Delivery
- Hot-rolled seamless square tubes bundled with high-tensile steel strips and edge protectors, sized to match 6 m, 6.4 m, and 12 m standard lengths for container loading
- Plain-end tubes secured in seaworthy bundles with waterproof wrapping to prevent surface oxidation during ocean freight for Q195–Q345 grades
- Container loading plans optimized by our logistics team to maximize weight utilization within 20ft and 40ft containers, accounting for the density of thick-wall seamless SHS up to 40 mm
- Custom cutting to project-specific lengths available before shipment, reducing on-site waste and secondary cutting cost for EPC contractors
- Each bundle marked with heat number, steel grade (Q345, S355JR, etc.), size, and length for immediate identification at the job site
- Shipping terms available as FOB, CIF, or DDP with door-to-door delivery to project sites across Southeast Asia, the Middle East, Africa, and the EU
Requesting a Quotation for Your Seamless SHS Project
Submit your specification sheet — including steel grade, outer dimension, wall thickness, total tonnage, and destination port — and our engineering team returns a detailed quotation within 12 hours, including unit price, applicable certification, production lead time, and payment terms. For non-standard dimensions outside the 2,800+ specification range, we provide a custom feasibility assessment with proposed tooling and lead time. All quotations include the option to attach original mill test certificates and arrange SGS/BV third-party inspection before shipment.
Frequently Asked Questions
Q: How do Q345, S355JR, and ASTM A500 Gr.C compare for structural applications?
A: These grades belong to different standard systems — Q345 follows Chinese GB, S355JR follows European EN 10025, and ASTM A500 Gr.C follows American standards — but they occupy a similar yield strength class used for structural frames and load-bearing hollow sections. We provide cross-reference documentation with each order so your engineer can verify equivalence for the project’s governing code.
Q: Can I verify material authenticity before shipment?
A: Every low carbon seamless square steel tube is accompanied by an original Mill Test Certificate with heat number traceability. Buyers may also appoint SGS or BV for third-party inspection at our facility before loading, and we provide full chemical composition and mechanical property reports from our in-house laboratory.
Q: What is the MOQ and can you produce non-standard sizes?
A: The standard MOQ is 25 tons. Our production lines cover over 2,800 specifications with wall thickness up to 40 mm, and we accept custom non-standard dimensions based on project drawings.
Q: What certifications do you provide for EU and African markets?
A: We hold CE certification under EN 10210 and EN 10219 for EU compliance, and we prepare SONCAP documentation for Nigeria, SASO for Saudi Arabia, and PVOC for Kenya. The full customs document package is included with every shipment.
Q: What surface treatment options are available beyond hot-rolled?
A: Hot-rolled is the standard finish for seamless square tubes. Depending on the application environment, we can arrange galvanized coating, 3PE anti-corrosion coating, or oiled surface treatment to match the project’s corrosion protection requirements.
Get Your Seamless SHS Quotation with Mill Test Certificate
Send your specification — steel grade, size, wall thickness, quantity, and destination — to receive a detailed quotation and sample mill test certificate within 12 hours.
Email: admin@sdxjysteel.com | WhatsApp / Mobile: +86 188 5315 7756 | Tel: +86 531 8573 6315
