Description
Factory-Direct Rectangular Hollow Sections — 20×40mm to 300×500mm carbon steel tubes produced on three dedicated lines with in-house lab testing before every shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Black Rectangular Hollow Section |
| Product Type | Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q215, Q235, Q345, #20, #45 |
| Standard | EN10219, EN10210, GB/T 6728, JIS G3466, ASTM A500, ASTM A36 |
| Section Shape | Rectangular |
| Size Range | 20×40mm – 300×500mm |
| Wall Thickness | 1.2mm – 20mm |
| Length | 3m – 12m (random) |
| Technique | Hot Rolled / ERW |
| 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 / Solar structure components / Fence posts / Greenhouse frames / Machinery manufacturing / Shipbuilding |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors & Construction | Structural building frames, solar panel support structures, bridge railings |
| Machinery Manufacturers | Equipment frames, conveyor system supports, industrial fabrication bases |
| Infrastructure & Agriculture | Highway fence posts, greenhouse skeleton frames, warehouse column supports |
| Shipbuilding | Deck structure supports, cabin framing, non-pressure piping conduits |
What Wall-Thickness Tolerance Costs on a Black Rectangular Steel Tube 25×25 Hollow Section Supplier Order
A ±1% tolerance means the difference between passing structural inspection and scrapping an entire container.
When procurement teams order rectangular hollow sections without verifying tolerance claims against actual mill measurements, the consequences compound quickly. A 1.5mm wall that arrives at 1.2mm reduces load-bearing capacity below design thresholds — and the entire batch becomes unusable for structural applications. Missing mill certificates trigger customs holds at destination ports, while inconsistent steel grades across bundles force on-site re-sorting that delays crane schedules. [NEED_CITE: EN 10219 cold-formed structural hollow section tolerance requirements]
Matching Q235 and Q345 Rectangular Tubes to Structural Load Requirements
The Black Rectangular Steel Tube 25×25 Hollow Section Supplier range from 20×40mm to 300×500mm covers load paths from light greenhouse framing to heavy industrial equipment bases. Q235 grades serve general construction frames where moderate yield strength suffices, while Q345 steps up for solar structure components and machinery bases requiring higher load resistance. The ±1% wall thickness tolerance ensures that calculated section modulus values hold true during engineering sign-off, and the proprietary sharp-corner forming technology delivers flat surfaces that bolt flush against connection plates without gap-filling shims.
Engineering Compliance Across EN, ASTM, and JIS Frameworks
Rectangular hollow sections destined for EU projects must conform to EN 10219 (cold-formed) or EN 10210 (hot-formed) standards, with CE marking mandatory for structural use. North American buyers typically specify ASTM A500 Grade A, B, or C, while JIS G3466 governs Japanese-specification projects across Southeast Asia. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards] The Black Rectangular Steel Tube 25×25 Hollow Section Supplier portfolio maps Q235 to S235JR and A500 Grade A equivalents, with mill test certificates documenting chemical composition and mechanical properties per the requested standard. Third-party inspection through SGS or BV validates compliance before container sealing, eliminating rejection risk at destination customs.
Decoding Carbon Steel Grades and ERW Welding for Rectangular Hollow Sections
Q195 through Q345 represent the Chinese GB/T 700 carbon steel series, where the number indicates minimum yield strength in MPa — Q235 delivers 235 MPa yield, suitable for general structural frames, while Q345 provides 345 MPa for heavier load paths. The #20 and #45 grades fall into优质碳素结构钢 territory, with #45 offering higher carbon content for machined components requiring surface hardness. ERW (Electric Resistance Welding) forms the rectangular profile from coil strip, creating a longitudinal weld seam that undergoes ultrasonic inspection — this process suits wall thicknesses from 1.2mm to 20mm and delivers tighter dimensional accuracy than seamless alternatives at lower cost. [NEED_CITE: ERW versus seamless rectangular tube manufacturing process comparison] Black oiled surface treatment provides short-term corrosion protection during transit and fabrication, while pre-galvanized (40–80g/m²) and hot-dip galvanized (200–600g/m²) options extend service life in outdoor or humid environments.
Hidden Costs When Mill Certificates and Tolerance Claims Fall Short
Ordering rectangular hollow sections without verified documentation creates downstream expenses that dwarf initial price savings. Material arriving without proper mill test certificates faces customs rejection or requires costly retroactive testing at destination. Wall thickness below specified tolerance forces structural engineers to recalculate load capacity — often resulting in rejection for safety-critical applications. [NEED_CITE: consequences of non-compliant steel imports on construction project timelines] Steel grade substitution without approval voids project insurance coverage and creates liability exposure if structural failure occurs. The Black Rectangular Steel Tube 25×25 Hollow Section Supplier program eliminates these risks through in-house laboratory testing, original MTC issuance per heat number, and optional third-party inspection before dispatch.
Procurement Confidence Through Vertical Integration and Certification Depth
Shandong Xin Jiyuan operates three dedicated production lines covering 2,800+ specifications, with wall thicknesses reaching 40mm — capabilities backed by 41 invention patents including proprietary sharp-corner rectangular tube technology that addresses global market gaps. Every batch undergoes chemical composition analysis and mechanical property testing in the on-site physical and chemical laboratory before shipment, with results documented in original mill test certificates. The factory holds ISO 9001:2015 certification alongside Lloyd’s Register EU CE marking under EN 10210 and EN 10219, plus Singapore FPC certification and SGS/BV verification — documentation that clears customs across 50+ export destinations without delay. Custom non-standard sizes and定尺 cutting services eliminate the need for on-site modification, while professional loading plans optimize container utilization for 3m to 12m lengths, reducing per-ton freight costs.
Documentation & Compliance
- Mill Test Certificate documenting Q235/Q345 chemical composition and yield strength per EN10219 or ASTM A500 as specified
- CE Certificate under EN 10210 and EN 10219 for EU market structural compliance and customs clearance
- ISO 9001:2015 Quality Management System certificate covering production and testing processes
- SGS or BV Third-Party Inspection Report verifying dimensions, surface quality, and coating thickness before shipment
- Material Traceability Records linking each bundle to heat number, production date, and test results
- Customs Documentation Package including packing list, bill of lading, and certificate of origin for destination clearance
Packaging, Loading & Delivery
- Black oiled rectangular tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Pre-galvanized and hot-dip galvanized sections wrapped with waterproof cloth to preserve zinc coating integrity
- Container loading optimized for 3m–12m random lengths with nested rectangular profiles maximizing 20ft and 40ft GP capacity
- Custom cutting to project-specified lengths available, with bundled labeling showing heat number, steel grade, and dimensions
- FOB, CIF, and DDP logistics options with door-to-door delivery to 50+ countries including EU, North America, and Southeast Asia
- Bundle identification tags displaying steel grade (Q235/Q345), size specification, wall thickness, and production heat number for on-site traceability
Requesting Quotes and Mill Test Certificates for Your Rectangular Hollow Section Project
Submit your specification sheet including section dimensions, wall thickness, steel grade preference, total tonnage, and destination port to receive a detailed quotation within 12 hours. The response includes unit pricing, production lead time, applicable certifications, and sample mill test certificate format for your engineering team’s review. Non-standard sizes and custom length requirements receive separate evaluation with feasibility confirmation and tooling timeline.
Frequently Asked Questions
Q: How do Q235, Q345, and international steel grades correspond to each other?
A: Q235 maps to S235JR under EN standards and ASTM A500 Grade A, while Q345 corresponds to S355JR and ASTM A500 Grade B. The mill test certificate documents actual chemical composition and mechanical properties, allowing your engineering team to verify equivalence for your specific design code.
Q: Can you provide third-party inspection before shipment?
A: Yes, SGS and BV inspection services are available upon request. The inspector verifies dimensions, wall thickness, surface quality, coating thickness for galvanized products, and witnesses mechanical testing. The inspection report accompanies the mill test certificate in the shipping documentation package.
Q: What is the minimum order quantity for custom non-standard rectangular sizes?
A: The standard MOQ is 1 Ton for catalog sizes within the 20×40mm to 300×500mm range. Non-standard dimensions outside this scope require evaluation based on production line setup and tooling requirements — contact the sales team with your specification for feasibility confirmation and quantity requirements.
Q: How do you ensure wall thickness meets the ±1% tolerance claim?
A: Every production batch undergoes ultrasonic thickness measurement at multiple points along the length and around the perimeter. Results are documented in the mill test certificate. The in-house physical and chemical laboratory performs incoming material inspection, in-process monitoring, and final pre-shipment verification.
Q: What surface treatment options work best for outdoor structural applications?
A: For outdoor exposure, hot-dip galvanized coating (200–600g/m²) provides the longest corrosion protection life. Pre-galvanized (40–80g/m²) suits moderate environments or applications requiring subsequent painting. Black oiled finish works for indoor structural frames or components receiving field-applied coating systems.
Secure Your Black Rectangular Steel Tube 25×25 Hollow Section Supplier Quote Today
Send your project specifications including dimensions, steel grade, quantity, and destination port to receive pricing and mill test certificate samples within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjysteel.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjysteel.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
