Description
Factory-direct seamless hollow sections — 2,800+ specifications with wall thickness up to 20mm in stock.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q345B Carbon Steel Seamless Square & Rectangular Hollow Section |
| Product Type | Seamless Square and Rectangular Hollow Section |
| Steel Grade | Q195, Q215, Q235B, Q345B, #20, #45 |
| Standard | EN10210, EN10219, GB/T 6728, JIS G3466, ASTM A500, ASTM A36, ASTM A53, ASTM A106 |
| Section Shape | Square / Rectangular |
| Size Range | Square 20×20mm–500×500mm; Rectangular 20×40mm–300×500mm |
| Wall Thickness | 1.2mm–20mm |
| Length | 3m–12m (random / cut-to-length) |
| Technique | Seamless / Hot Rolled |
| Surface Treatment | Black (oiled / non-oiled), Pre-galvanized (40–80g/m²), Hot-dip galvanized (200–600g/m²) |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures, construction frames, machinery manufacturing, solar support structures, glass curtain walls, greenhouse frames, fence posts, pressure vessels, bridges, power plant equipment |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, bridge trusses, high-rise structural columns, solar mounting systems |
| Architectural Facades | Glass curtain wall framing, sharp-corner rectangular profiles for exposed steel facades |
| Machinery Manufacturing | Hydraulic cylinder housings, conveyor rollers, crane boom sections, equipment bases |
| Industrial & Energy | Pressure vessel shells, power plant pipe racks, boiler support frames, pipeline casings |
| Agriculture & Fencing | Greenhouse structural frames, heavy-duty fence posts, irrigation support structures |
What Wall-Thickness Tolerance Costs on a Seamless Hollow Section Order
Tolerance drift beyond ±1% turns a compliant structural frame into a rejected shipment at destination inspection.
When procurement teams order ASTM A106 Q345B seamless square rectangular hollow section supplier products for load-bearing frames, even minor wall thickness deviations compound across hundreds of members. A batch of seamless square tubes arriving at a Middle East site with negative tolerance beyond the allowable range triggered a full SGS rejection — the structural engineer could not verify load capacity against the original design calculations. [NEED_CITE: EN 10219 dimensional tolerance requirements for structural hollow sections] The cost was not just the replacement material; it was three weeks of idle labor and rescheduled crane time.
This is why in-house dimensional verification before shipment matters. Every ASTM A106 Q345B seamless square rectangular hollow section supplier shipment undergoes ultrasonic wall thickness mapping at multiple points per piece, not just at the ends where thinning is least likely during the hot-rolling pierce process.
Matching Seamless Hollow Sections to Structural Load Paths
Seamless square and rectangular hollow sections in Q345B and ASTM A106 grades carry load uniformly across all four faces, making them the default choice for compression members and moment-resisting connections in steel frames. The hot-rolled seamless process eliminates the weld seam found in ERW alternatives — critical when the tube will be drilled, slotted, or welded at close spacing for gusset plate connections. For glass curtain wall applications, the patented sharp-corner rectangular profile provides clean 90-degree external corners that sit flush against architectural glazing channels, removing the need for filler plates or grinding that rounded-corner ERW tubes require.
Engineering Compliance and Certification Requirements
Structural hollow sections destined for EU markets must carry CE marking under EN10210 (hot-finished seamless) or EN10219 (cold-formed welded), with factory production control audited by a notified body. [NEED_CITE: CE marking requirements for structural steel hollow sections under CPR Regulation 305/2011] North American projects typically specify ASTM A500 Grade B/C or ASTM A106 for high-temperature service, requiring mill test certificates with heat-level chemical and mechanical traceability. The Q345B grade maps closely to S355JR/S355J2 in the EN system and offers higher yield capacity than Q235B for heavily loaded columns and transfer beams. Cut-to-length service at the mill reduces on-site welding and secondary cutting, which preserves the integrity of the heat-affected zone in structural connections.
Steel Grade Selection and Seamless Process Fundamentals
The Q-series carbon structural steels (Q235B, Q345B) follow the Chinese GB/T 1591 system where the number indicates minimum yield strength in MPa. Q345B delivers roughly 50% higher yield capacity than Q235B, allowing smaller cross-sections for the same design load — a direct weight and cost saving on large-tonnage orders. The #20 and #45 grades serve mechanical and pressure applications where carbon content governs machinability and heat treatment response rather than structural yield. The seamless hot-rolling process starts from a solid round billet pierced through the center, then elongated and shaped through a series of dies into square or rectangular profiles — this produces a grain structure that flows continuously around the corners, giving seamless hollow sections superior corner toughness compared to welded alternatives where the corner is formed by bending a flat plate. [NEED_CITE: metallurgical grain flow advantages of seamless versus welded hollow sections] Surface options range from black oiled for indoor structural use to hot-dip galvanized (200–600g/m²) for outdoor or corrosive environments such as coastal facades and industrial plant frames.
The Hidden Cost of Unverified Seamless Tube Procurement
Ordering ASTM A106 Q345B seamless square rectangular hollow section supplier material without verified mill test certificates creates a cascade of downstream risk. Material that fails to meet the specified grade chemistry will not pass third-party inspection at destination, triggering customs holds or outright rejection. Negative tolerance beyond the standard ±1% range reduces actual load capacity below design assumptions, creating structural safety exposure that only surfaces during loading tests or, worse, under service loads. Missing CE documentation blocks EU customs clearance entirely, regardless of physical product quality. [NEED_CITE: consequences of non-compliant structural steel documentation in international trade] The true cost of a rejected container is not the material price — it is the project delay, the re-procurement lead time, and the loss of credibility with the end client.
Procurement Confidence Through Verified Manufacturing Capability
Every ASTM A106 Q345B seamless square rectangular hollow section supplier order ships with full dimensional, chemical, and mechanical test reports generated from the in-house physical and chemical laboratory — not outsourced to a third party that samples after the fact. The production facility holds 41 invention patents including the original Chinese patent for sharp-corner rectangular hollow sections, covering 2,800+ specifications with wall thickness up to 20mm. Full international certification includes ISO 9001:2015, Lloyd’s CE marking under EN10210/EN10219, Singapore FPC, and pre-shipment verification by SGS or BV at buyer’s request. Custom non-standard sizes, cut-to-length service, and professional container loading with anti-damage measures are standard — not premium add-ons. The ASTM A106 Q345B seamless square rectangular hollow section supplier capability extends to 50+ countries across the EU, North America, Middle East, and Southeast Asia, with designated supplier status for major state-owned enterprises and listed companies.
Documentation & Compliance
- Mill test certificate documenting Q345B chemical composition (C, Mn, Si, S, P) and mechanical properties per GB/T 1591 and EN10210 equivalent requirements
- CE certificate confirming EN10210 compliance for hot-finished seamless structural hollow sections, issued by Lloyd’s Register
- ISO 9001:2015 quality management system certificate covering the full production and inspection process
- SGS or BV third-party inspection report verifying dimensional tolerance, surface quality, and marking before container sealing
- Heat number traceability linking each piece to its original billet chemistry and rolling record
- Export customs documentation including packing list, bill of lading, and certificate of origin for destination clearance
Packaging, Loading & Delivery
- Seamless square and rectangular hollow sections bundled with high-tensile steel strips, separated by timber dunnage to prevent surface scratching during ocean transit
- Black oiled tubes wrapped in waterproof cloth at bundle ends to prevent moisture ingress and edge corrosion during container shipping
- Hot-dip galvanized hollow sections fitted with rubber edge protectors at contact points to preserve the zinc coating under strap tension
- Cut-to-length orders (3m–12m) loaded with nested nesting optimization to maximize 20ft and 40ft container payload without exceeding weight limits
- Each piece marked with heat number, steel grade (Q345B / ASTM A106), size, and length for on-site identification and traceability
- FOB, CIF, and DDP shipping terms available with professional container loading supervision to prevent bending or impact damage to sharp-corner rectangular profiles
Initiating Your Seamless Hollow Section Inquiry
Submit your required section shape, outer dimensions, wall thickness, steel grade, surface treatment, total tonnage, and destination port to receive a detailed quotation with unit pricing, production lead time, and applicable certification documentation. For non-standard sizes outside the 20×20mm–500×500mm range or wall thickness beyond 20mm, the engineering team will confirm feasibility and tooling requirements. Third-party inspection (SGS/BV) and specific mill test certificate formats can be arranged at the inquiry stage to align with your project’s quality assurance protocol.
Frequently Asked Questions
Q: How do Q235B and Q345B grades correspond to EN and ASTM standards?
A: Q235B maps closely to S235JR in the EN system and ASTM A36 in the US system, while Q345B corresponds to S355JR/S355J2 under EN10210 and ASTM A572 Grade 50. Full chemical and mechanical equivalence should be confirmed against the specific project specification, and mill test certificates are provided to verify compliance with the nominated standard.
Q: What is the difference between seamless and welded square/rectangular hollow sections for structural use?
A: Seamless hollow sections are produced by hot-rolling a solid billet through a piercing process, resulting in continuous grain flow around the corners and no weld seam. This makes them preferred for high-pressure applications, heavy structural columns, and situations where the tube will be extensively drilled or welded at close spacing. Welded hollow sections are formed from plate and welded along a seam, offering cost advantages for lighter structural applications where the weld zone is not critically loaded.
Q: Can you produce non-standard sizes with low minimum order quantities?
A: The production facility covers 2,800+ specifications with wall thickness up to 20mm, and custom non-standard sizes outside the standard range are available with a minimum order quantity of 1 Ton. Specific tooling and lead time requirements for non-standard dimensions are confirmed during the quotation stage.
Q: What documentation is provided for EU customs clearance?
A: EU shipments include CE marking under EN10210 or EN10219 as applicable, mill test certificates with heat number traceability, and full export documentation (packing list, bill of lading, certificate of origin). Lloyd’s CE certification and Singapore FPC are held on file, and third-party inspection reports from SGS or BV can be arranged pre-shipment.
Q: How is corner quality guaranteed for sharp-corner rectangular tubes used in architectural facades?
A: The sharp-corner rectangular tube technology is covered by 41 invention patents and produces true 90-degree external corners without the rounded radii typical of formed welded sections. Dimensional verification of corner squareness is performed during in-house inspection, and the profile is designed to sit flush against architectural glazing channels without filler or grinding.
Request Your Seamless Hollow Section Quotation
Provide your section dimensions, steel grade, quantity, and destination port to receive pricing, certification details, and production scheduling within 12 hours.
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