Description
Factory-direct Q235B seamless hollow sections — Hot-rolled tubes from 20×20 mm to 500×500 mm with wall thickness up to 20 mm, shipped with full mill test certificates and CE/EN compliance for 50+ countries.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Seamless Square and Rectangular Hollow Section |
| Product Type | Seamless Square and Rectangular Steel Tube / Hollow Section |
| Steel Grade | Q195, Q215, Q235, Q235B, Q345, Q355, #20, #45, S195, S235, S235JR, S355JR, A53 Grade A, A53 Grade B, A500 Grade A, A500 Grade B, A500 Grade C, STK400, SS400, ST42.2, A36 |
| Standard | EN 10219, EN 10210, GB/T 6728, JIS G3466, ASTM A500, ASTM A53, ASTM A36 |
| Section Shape | Square / Rectangular |
| Size Range (Square) | 20×20 mm – 500×500 mm |
| Size Range (Rectangular) | 20×40 mm – 300×500 mm |
| Wall Thickness | 1.2 mm – 20 mm |
| Length | 3 m – 12 m (random / cut to length) |
| Technique | Hot Rolled / Seamless |
| Surface Treatment | Black (oiled / non-oiled), Pre-galvanized (40–80 g/m²), Hot-dip galvanized (200–600 g/m²) |
| Tolerance | ±1% |
| Ends | Plain / Beveled (customizable) |
| Processing Service | Bending, Welding, Decoiling, Punching, Cutting |
| Application | Steel structures, Construction, Solar structures, Fence posts, Greenhouse frames, Machinery, Shipbuilding, Bridges, Pressure vessels |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Construction | Steel structure frames, high-rise building columns, bridge support components, infrastructure pylons |
| Solar & Greenhouse Builders | Solar panel mounting structures, greenhouse frame systems requiring corrosion-resistant galvanized finishes |
| Machinery & Industrial Manufacturing | Heavy-load welded structural parts, lifting machinery frames, pressure vessel shells, oil storage tank supports |
| Shipbuilding & Power Engineering | Deck structures, cable support frames, power transmission tower bases |
| Highway & Airport Infrastructure | Highway railing posts, airport terminal roof trusses, signage support columns |
What Missing Mill Test Certificates Cost on a Q235B Hollow Section Order
A customs hold at destination port costs far more than the price difference between a verified mill and a trading company.
I have seen Q235B seamless square and rectangular hollow section containers stuck at Lagos and Jeddah because the mill test certificates listed chemical compositions that did not match the heat numbers stamped on the tube ends. The importer paid demurrage for weeks while the supplier “investigated.” The root cause was never a material failure — it was a documentation failure. When you source a Q235B seamless square and rectangular hollow section for structural use under EN 10219 or ASTM A500, the certificate must trace every tube back to its original heat number with verified chemical composition and mechanical test results. [NEED_CITE: EN 10204 3.1 inspection document requirements for steel products]
Fragmented sourcing makes this worse. Buy pipes from one supplier, plates from another, and fabrication from a third — and you end up with three different certificate formats, three different traceability chains, and three different points of failure when the inspector arrives on site.
How Seamless Hot-Rolled Q235B Tubes Match Structural Frame Requirements
A Q235B seamless square and rectangular hollow section produced through the hot-rolled process delivers consistent wall thickness across the entire cross-section — critical when structural engineers calculate load-bearing capacity for column and beam applications. The seamless manufacturing method eliminates the weld seam found in ERW tubes, making these hollow sections suitable for pressure vessels and environments where weld integrity is a concern. Wall thickness from 1.2 mm to 20 mm covers both light-gauge greenhouse framing and heavy-duty machinery bases. The ±1% tolerance range keeps theoretical weight calculations reliable for cost estimation, while cut-to-length service at 3 m to 12 m reduces on-site waste.
Engineering Compliance: Load, Corrosion, and Certification Alignment
Structural frames designed under EN 1993 or AISC specifications require hollow sections that meet dimensional and mechanical standards — EN 10219 for cold-formed or EN 10210 for hot-finished structural hollow sections in European projects, ASTM A500 Grade B or C for North American construction. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerances] Q235B maps directly to S235JR under EN standards and A53 Grade B under ASTM, simplifying specification compliance across regions. For outdoor or marine environments, hot-dip galvanized coating at 200–600 g/m² provides long-term corrosion protection, while black oiled finish suits indoor structural applications where painting follows installation. Beveled ends prepare tubes for on-site butt welding, and plain ends work with mechanical connectors. CE certification under EN 10210/EN 10219 is mandatory for structural steel entering the EU market — without it, the shipment faces rejection at customs regardless of material quality. [NEED_CITE: CE marking requirements for structural steel under EN 10210]
Steel Grade Equivalence and Hot-Rolled Seamless Process Explained
Q235B is a Chinese standard carbon structural steel with minimum yield strength positioning it between mild steel and higher-strength low-alloy grades. In the European system, S235JR serves as the direct equivalent, both meeting similar chemical composition limits for carbon, manganese, and sulfur. Under ASTM, A53 Grade B and A500 Grade A occupy comparable positions. This equivalence matters when a project specification calls for S235JR but the procurement team sources from Chinese mills producing Q235B — the material is interchangeable if the mill test certificate confirms compliance.
The hot-rolled seamless process starts with solid round billets heated and pierced through the center, then elongated and shaped into square or rectangular profiles through a series of dies. Unlike ERW tubes formed from rolled coil and welded along a seam, seamless tubes have uniform grain structure around the entire cross-section. This makes them preferable for applications involving internal pressure, bending without seam splitting, or exposure to cyclic loading.
Surface treatment selection follows the service environment. Black oiled tubes ship with a thin oil film preventing transit rust — suitable for indoor structures that receive paint or fireproofing after installation. Pre-galvanized coating at 40–80 g/m² offers moderate corrosion resistance for covered outdoor applications like greenhouse frames. Hot-dip galvanizing at 200–600 g/m² immerses the finished tube in molten zinc, creating a metallurgical bond that protects solar mounting structures and highway railings for decades.
Wall thickness tolerance at ±1% means a specified 10 mm wall measures between 9.9 mm and 10.1 mm. This tight range matters for weight-based invoicing and structural calculations — wider tolerances found in some welded tube production can shift actual weight by significant margins across a full container load.
The Hidden Cost of Wrong Grade or Missing Certification on Site
Specify Q235B for a structural column and receive tubes with actual chemistry outside the standard range — the engineer’s load calculations become invalid, and the building inspector rejects the entire batch. The cost is not the tube price. It is the crane time already scheduled, the welders standing by, and the project delay penalty. Similarly, a container of Q235B seamless square and rectangular hollow section arriving without CE documentation for an EU construction site cannot be legally installed, regardless of whether the steel itself is perfectly compliant. [NEED_CITE: consequences of non-compliant steel documentation in EU construction projects] Negative tolerance abuse — where a supplier ships tubes at the lower edge of acceptable thickness and invoices at nominal weight — transfers cost from the mill to the buyer through reduced structural capacity and inflated piece counts.
Why Engineering Procurement Teams Source Q235B Hollow Sections Here
Every container of Q235B seamless square and rectangular hollow section leaving our Jinan facility passes through an in-house physical and chemical laboratory that tests incoming billets, monitors production parameters, and verifies finished tube properties before release. The mill test certificate travels with the shipment — heat number, chemical composition, tensile strength, and dimensional inspection results tied to every bundle. Our facility holds 41 invention patents including proprietary sharp-corner rectangular tube technology that produces tight-radius corners impossible through standard cold-forming, filling specification gaps for architectural and structural projects requiring precise internal dimensions.
We maintain 2,800+ specifications in stock across square, rectangular, and round profiles — meaning a project requiring Q235B seamless tubes at 200×200×10 mm alongside Q355B welded sections at 300×150×12 mm sources both from a single purchase order with unified documentation. CE certification under Lloyd’s Register for EN 10210/EN 10219, ISO 9001:2015 quality management, Singapore FPC, and SGS/BV third-party verification remove certification gaps that cause customs delays. Professional loading plans optimize container utilization for 11.8 m long tubes in 40ft containers, with dunnage and blocking calculated to prevent transit damage — a lesson learned from watching a container of deformed tubes get rejected at an African port because the stacking pattern shifted the center of gravity.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Mn, Si, S, P limits) and mechanical properties per GB/T 700, with heat number traceability for every bundled tube
- CE certificate under EN 10210 / EN 10219 for structural hollow sections entering European Union construction markets
- ISO 9001:2015 quality management system certificate covering design, production, and inspection of seamless square and rectangular hollow sections
- SGS or BV third-party inspection report available upon request, verifying dimensional tolerance, surface quality, and coating thickness before shipment
- Material traceability report linking each bundle to its original heat number, production date, and test results from our in-house laboratory
- Customs documentation package including packing list, bill of lading, and certificate of origin formatted for destination-country clearance requirements
Packaging, Loading & Delivery
- Seamless Q235B square and rectangular hollow sections bundled with steel strips and edge protectors, preventing surface damage to black oiled or galvanized finishes during ocean transit
- Hot-dip galvanized tubes separated by rubber spacers within bundles to preserve zinc coating integrity — critical for solar structure and greenhouse frame applications requiring full corrosion protection
- Container loading plans optimized for 6 m and 11.8 m tube lengths in 20ft and 40ft containers, with wooden dunnage positioned to distribute weight and prevent shifting during port handling
- Cut-to-length service available within the 3 m to 12 m range, reducing on-site cutting waste for construction projects with fixed bay spacing requirements
- Heat number and steel grade stenciled on each tube end, with bundle tags matching the mill test certificate for immediate site identification and inspection
- FOB, CIF, and DDP shipping terms available, with door-to-door logistics coordination for project sites in EU, North America, Southeast Asia, Middle East, and Africa
How to Request a Quotation with Full Technical Documentation
Submit your specification sheet listing section dimensions, wall thickness, length, steel grade (Q235B or equivalent), surface treatment preference, and destination port — our team responds within hours with unit pricing, production lead time, and available mill test certificate formats. For non-standard dimensions outside the 2,800+ specification range, share your drawing and required quantity to receive a custom production assessment including tooling timeline and minimum order requirements.
Start Your Q235B Hollow Section Procurement
Send your specifications, quantity, and destination to receive a detailed quotation with mill test certificate confirmation and delivery schedule.
- Website: www.sdxjysteel.com
- Email: admin@sdxjysteel.com
- WhatsApp: +86 188 5315 7756
Frequently Asked Questions
Q: Can you provide EN 10204 3.1 mill test certificates for Q235B seamless hollow sections exported to Europe?
A: Yes. Every shipment includes EN 10204 3.1 type inspection certificates documenting chemical composition and mechanical properties per the applicable standard, with heat number traceability for each bundle. Our in-house laboratory conducts all testing, and third-party verification through SGS or BV is available upon request before shipment.
Q: How does Q235B compare to S235JR and ASTM A53 Grade B for international projects?
A: Q235B is the Chinese national standard equivalent to S235JR under EN 10219/EN 10210 and closely matches ASTM A53 Grade B in chemical composition and mechanical properties. Our mill test certificates confirm compliance with the specified standard, allowing seamless substitution when project specifications permit equivalent grades across EN, ASTM, and GB systems.
Q: What is the minimum order quantity for custom non-standard dimensions outside your standard range?
A: We stock over 2,800 specifications covering 20×20 mm to 500×500 mm square sections and 20×40 mm to 300×500 mm rectangular sections with wall thickness from 1.2 mm to 20 mm. For dimensions outside this range, custom production is available — share your required specifications and quantity to receive a tailored assessment including minimum order requirements and production timeline.
Q: How do you optimize container loading for 11.8 m long seamless hollow sections?
A: Our loading team calculates weight distribution and stacking patterns for each order, positioning wooden dunnage and securing bundles to prevent transit shift. For 40ft containers, 11.8 m tubes load efficiently with nested smaller sections filling void spaces. Loading plans are photographed and shared before container sealing, giving you visibility into how your Q235B seamless square and rectangular hollow section order is secured for ocean freight.
Q: Do you offer cutting, bending, and other value-added processing before shipment?
A: Yes. Our facility provides cutting to specified lengths within the 3 m to 12 m range, bending, punching, and welding preparation including beveled ends. These services reduce on-site fabrication time and waste for construction and machinery manufacturing projects, with processing details documented in the shipment paperwork alongside material certifications.
