Description
Factory-Direct ERW Hollow Sections — Vertically integrated mill and fabrication facility covering Q195–Q345 and S235–S355 grades across 2,800+ size specifications, eliminating third-party material sourcing gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q195-Q345 Black ERW Rectangular Hollow Section Steel Tube |
| Product Type | Rectangular Hollow Section (RHS) / Square Hollow Section (SHS) |
| Steel Grade | Q195, Q215, Q235, Q345, 10#, 20#, Gr.A, Gr.B, Gr.C, S235, S275, S355, A36, SS400 |
| Standard | ASTM A500, EN 10219, EN 10210, JIS G3466, GB/T 6728 |
| Section Shape | Square / Rectangular |
| Size Range (SHS) | 20×20 mm – 400×400 mm |
| Size Range (RHS) | 20×40 mm – 300×500 mm |
| Wall Thickness | 0.8 – 20 mm |
| Length | 3 – 12 m (customizable) |
| Technique | ERW (High-Frequency Welded) |
| Surface Treatment | Black Iron / Oiled / Painted (Varnish Lacquer) / Hot Dipped Galvanized (220–260 g/m²) / Pre-Galvanized (30–150 g/m²) / Bare |
| Tolerance | ±1% |
| Ends | Plain End / Bevel End / Groove End / Flange Joint / Threaded |
| Application | Steel structures / Construction / Scaffolding / Fence posts / Fire protection structures / Greenhouse frames / Low-pressure fluid transport |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Building frames, column-beam assemblies, mezzanine platforms for warehouses and logistics centers |
| Industrial Facilities | Factory roof trusses, equipment support structures, conveyor frame systems |
| Infrastructure | Bridge handrails, sound barrier posts, highway sign gantries |
| Agriculture | Greenhouse skeleton frames, irrigation support structures, livestock shelter frameworks |
| Scaffolding & Access | Scaffolding uprights, cross braces, stairway stringers for construction sites |
What Negative Tolerance on Wall Thickness Costs You at Customs and on Site
A black rectangular hollow section steel tube that passes mill inspection may still fail third-party verification if wall thickness clusters at the extreme negative edge of tolerance.
When overseas buyers receive ERW hollow sections sourced through trading intermediaries, the material traceability chain often breaks between the original mill and the final shipment. Third-party inspectors at destination ports — particularly in the Middle East and EU — routinely measure wall thickness at multiple points per piece. If readings fall below the minimum specified in EN 10219 or ASTM A500, entire containers get held. The cost of air-freighting replacement sections, combined with project schedule delays, typically dwarfs the original price difference between a verified supplier and a broker. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed welded hollow sections]
Matching Section Dimensions to Structural Load Paths
Selecting the right RHS or SHS profile from the 20×40 mm to 300×500 mm range depends on the load path and connection geometry of the target structure. For warehouse portal frames, larger sections such as 200×300 mm or 250×400 mm with wall thickness above 8 mm carry primary rafter and column loads, while smaller 40×60 mm or 50×100 mm sections serve as purlins and bracing members. The ±1% dimensional tolerance on this black rectangular hollow section steel tube ensures that welded connections and bolted end-plates fit without on-site grinding or reaming — a detail that matters when EPC contractors enforce tight erection tolerances. Our integrated production line covers the full range from light gauge greenhouse frames to heavy structural columns in a single quality system.
Engineering Compliance Across International Standards
Structural hollow sections used in load-bearing frames must comply with the design code governing the project location. EN 10219 covers cold-formed welded structural hollow sections for European projects, while ASTM A500 governs the North American market. The Q195–Q345 and S235–S355 grade range on this black rectangular hollow section steel tube allows procurement teams to source a single material family that maps across GB, EN, and ASTM systems — reducing the complexity of multi-standard projects. [NEED_CITE: steel grade equivalence mapping between GB Q-series and EN S-series] Surface treatment selection follows the corrosion environment: black or oiled finish suits indoor structural frames with planned fireproofing, pre-galvanized coatings at 30–150 g/m² serve sheltered outdoor applications, and hot dipped galvanizing at 220–260 g/m² is specified for aggressive coastal or industrial atmospheres. CE certification to EN 10210 and EN 10219 is required for structural steel entering the EU market, and third-party inspection by SGS or BV before shipment provides the documentation package that customs authorities and project engineers expect.
Understanding ERW Welding and Grade Selection for Hollow Sections
The ERW high-frequency welding process used to produce this black rectangular hollow section steel tube forms the longitudinal seam by heating the steel strip edges to forging temperature and pressing them together under pressure — without filler metal. This method produces a clean, narrow weld zone suitable for structural applications where the weld integrity is verified through in-process NDT and certified welding procedures (WPS/PQR). Compared to seamless manufacturing, ERW offers tighter dimensional tolerance on wall thickness and more consistent surface finish across the 0.8–20 mm thickness range, at a lower production cost per ton.
Steel grade selection directly affects the load-bearing capacity of the finished structure. Within the Q-series (GB standard), Q235 provides general-purpose strength for non-critical frames, while Q345 delivers higher yield strength for primary structural members. The S-series (EN standard) follows a similar progression: S235 for light structures, S275 for intermediate loads, and S355 for heavily loaded columns and long-span beams. The ASTM A500 Grades A, B, and C serve the same tiered function in North American projects. Choosing the correct grade avoids both over-engineering (unnecessary material cost) and under-engineering (structural failure risk).
Wall thickness tolerance deserves particular attention. The ±1% tolerance on this black rectangular hollow section steel tube means that a nominal 5 mm wall can measure between 4.95 mm and 5.05 mm. When invoicing is calculated by theoretical weight, buyers should confirm whether the supplier applies actual measured weight or theoretical weight based on nominal dimensions — a distinction that affects cost transparency. [NEED_CITE: theoretical weight calculation methods for welded hollow sections per EN 10219]
Hidden Costs of Procuring Hollow Sections Without Verified Documentation
Ordering ERW rectangular hollow sections from unverified suppliers introduces risks that surface only after the material reaches the project site. Material certificates that cannot be traced to specific heat numbers leave engineers unable to confirm chemical composition or mechanical properties. Sections that fail to meet the dimensional requirements of EN 10219 or ASTM A500 trigger rejection during third-party inspection — forcing the buyer to either accept non-conforming material (creating structural safety liability) or source replacements at premium cost and extended lead times. Missing CE documentation blocks customs clearance for EU-bound shipments, generating demurrage charges and project delays. [NEED_CITE: consequences of non-compliant structural steel in international construction projects]
Why Project Teams Source This Black Rectangular Hollow Section Steel Tube Through Our Facility
Our production starts from raw steel manufactured in our own mill, which operates three production lines and maintains over 2,800 size specifications in stock. This vertical integration means the chemical composition and mechanical properties of every black rectangular hollow section steel tube we deliver are traceable from the original steelmaking heat through the ERW forming, welding, and finishing stages — no third-party material sourcing, no gaps in the certification chain. Our internal laboratory performs chemical composition analysis and mechanical property testing on every production batch, and the resulting Mill Test Certificates document the actual values rather than specification minimums.
The fabrication division handles downstream processing — CNC cutting, drilling, welding, and surface treatment — allowing us to deliver both raw hollow sections and pre-fabricated assemblies from a single contract. Certified welding procedures (WPS/PQR) and qualified welders (AWS/EN certified) ensure that any welded connections or custom fabrications meet international code requirements. We provide complete quality documentation packages including WPS, PQR, weld maps, dimensional inspection reports, and coating thickness measurements — the paperwork that EPC firms and project owners require for engineering approval and customs clearance.
Documentation & Compliance
- Mill Test Certificate documenting Q235/Q345 or S235/S355 chemical composition and mechanical properties per EN 10219 or ASTM A500, traceable to heat number
- CE certificate confirming compliance with EN 10210 and EN 10219 for structural hollow sections entering European Union markets
- ISO 9001:2008 quality management system certificate covering the integrated steelmaking and ERW tube production process
- SGS or BV third-party inspection report verifying dimensional accuracy, wall thickness, surface treatment coating weight, and visual quality before shipment
- Material traceability documentation linking each black rectangular hollow section steel tube bundle to its original heat number, chemical analysis, and mechanical test results
- Export customs documents including packing list, bill of lading, and certificate of origin formatted for the destination country’s import requirements
Packaging, Loading & Delivery
- ERW rectangular and square hollow sections bundled with galvanized steel strips at intervals sized to prevent bundle deformation during lifting, with each bundle tagged by heat number, steel grade, and section dimensions
- Black iron or oiled surface finish protected by waterproof wrapping for ocean transit; pre-galvanized and hot dipped galvanized sections receive edge protectors to preserve coating integrity during handling and shipping
- Container loading plans optimized for 6 m and 12 m standard lengths of RHS and SHS profiles, with nested smaller sections inside larger profiles to maximize container utilization and reduce freight cost per ton
- Custom cutting to project-specific lengths within the 3–12 m range, with cut ends deburred and protected against corrosion during transport and on-site storage
- Each bundle marked with stenciled identification showing steel grade (Q345, S355, etc.), section size, wall thickness, heat number, and purchase order reference for site-level material traceability
- Shipping terms available as FOB, CIF, or DDP with professional export packing and complete documentation for customs clearance at destination ports
Starting Your Procurement for ERW Hollow Sections
Submit your project drawings, section sizes, steel grades, required surface treatment, and destination port to receive a detailed quotation including material cost, fabrication charges, coating, packing, and freight — along with the Mill Test Certificate format and third-party inspection arrangement. Our engineering team reviews shop drawings and confirms fabrication sequencing before production begins, ensuring that every black rectangular hollow section steel tube we ship matches your structural design and compliance requirements.
Request a Quotation with Full Mill Test Documentation
Send your specifications, steel grades, quantities, and destination port to receive pricing, production lead times, and certification details.
Contact: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Website: www.xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
Frequently Asked Questions
Q: How do Q235 and Q345 (GB standard) map to S235/S355 (EN standard) and Gr.B/Gr.C (ASTM A500)?
A: The Q-series, S-series, and ASTM grades follow a tiered strength progression. Q235 corresponds roughly to S235 and ASTM Gr.B in yield strength category, while Q345 aligns with S355 and ASTM Gr.C. We supply this black rectangular hollow section steel tube across all three standard systems from a single production facility, and our Mill Test Certificates document the actual test values so your engineer can verify equivalence for your specific design code.
Q: Can you arrange third-party inspection before shipment?
A: Yes. We coordinate pre-shipment inspection with SGS, BV, or CCIC at our facility. The inspector verifies dimensional accuracy, wall thickness, surface treatment coating weight, visual quality, and reviews the Mill Test Certificates against the purchase order. The inspection report is included in the export documentation package.
Q: When should I specify black, oiled, pre-galvanized, or hot dipped galvanized surface treatment?
A: Black or oiled finish is suitable for indoor structural frames where fireproofing or painting will be applied on site. Pre-galvanized coating at 30–150 g/m² provides corrosion protection for sheltered outdoor applications such as greenhouse frames or fence posts. Hot dipped galvanizing at 220–260 g/m² is specified for aggressive environments including coastal areas, industrial atmospheres, or buried applications. We produce this black rectangular hollow section steel tube in all surface options from the same section profiles.
Q: How is invoicing calculated — by theoretical weight or actual weight?
A: We invoice by theoretical weight based on the nominal section dimensions and wall thickness specified in the order. The ±1% dimensional tolerance means actual weight may vary slightly from theoretical weight. If your project requires actual weight invoicing, we can arrange this with pre-shipment weighing and documentation.
Q: How are large RHS sections packed and loaded for export?
A: Rectangular hollow sections in the 200×300 mm to 300×500 mm range are bundled with galvanized steel strips and loaded in containers using crane equipment. Smaller sections are nested inside larger profiles to maximize container space. For lengths exceeding container capacity, we arrange breakbulk or flat rack shipping with professional lashing and securing for ocean transit.
