Description
Let me work through this step by step.
Gate Check:
- identifier: “Carbon Steel Black Rectangular Steel Tube” — not null/empty → Pass
Step 1: Bold Positioning Statement
- identifier: “Carbon Steel Black Rectangular Steel Tube”
- Sum of digits in identifier: No digits in “Carbon Steel Black Rectangular Steel Tube” → sum = 0
- 0 mod 3 = 0 → Factory direct, no middleman direction
Step 2: Technical Specifications Table
From specs:
- Product Type: Rectangular Steel Tube (Hollow Section)
- Steel Grade: Q195, Q215, Q235, Q345, #20, #45
- Standard: ASTM / EN10219 / EN10210 / GB/T 6728 / JIS G3466 / ASTM A500 / A36
- Section Shape: Rectangular
- Size Range: Rectangular pipe 20×40mm–300×500mm; Square pipe 20×20mm–500×500mm
- Wall Thickness: 0.5–30mm
- Length: 3–12m
- Technique: Hot Rolled
- Surface Treatment: Black / Oiled / Pre-galvanized / Hot dipped galvanized
- Tolerance: ±1%
- Ends: Plain
- Application: from applications list
- MOQ: 1 Ton
- Origin: China (from client profile)
Step 3: Application Suitability
Intersect applications with client profile target industries.
Step 4: H2 with main keyword
Main keyword: “black rectangular steel tube supplier”
Need 3-6 occurrences.
Step 5-16: Follow skeleton
Let me now draft the full content.
Keyword count plan:
- “black rectangular steel tube supplier” — need 3-6 times, distributed evenly.
Let me draft:
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Factory-Direct Mill Supply, Zero Broker Markup — SD XJY Pipe operates three dedicated production lines covering over 2,800 specifications for hot-rolled black rectangular and square hollow sections, shipped directly from Jinan to your project site.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Black Rectangular Steel Tube |
| Product Type | Rectangular Steel Tube (Hollow Section) |
| Steel Grade | Q195, Q215, Q235, Q345, #20, #45 |
| Standard | ASTM A500, ASTM A36, ASTM A53, EN10219, EN10210, GB/T 6728, JIS G3466 |
| Section Shape | Rectangular |
| Size Range | Rectangular 20×40mm–300×500mm; Square 20×20mm–500×500mm |
| Wall Thickness | 0.5–30mm |
| Length | 3–12m (random or customized) |
| Technique | Hot Rolled |
| Surface Treatment | Black / Oiled / Pre-galvanized (40–80g/m²) / Hot dipped galvanized (200–600g/m²) |
| Tolerance | ±1% |
| Ends | Plain |
| Processing Service | Bending, Welding, Decoiling, Punching, Cutting |
| Application | Construction, Steel Structures, Solar Structures, Machinery Manufacturing, Glass Curtain Walls, Bridges |
| MOQ | 1 Ton |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Building frames, column supports, beam-to-column connections, scaffolding uprights |
| Steel Structure Fabrication | Portal frames, truss members, bracing elements, purlin systems |
| Solar Energy | Solar panel mounting structures, ground-mount racking frames, tracker support posts |
| Glass Curtain Walls | Architectural facade framing, mullion supports, sharp-corner decorative sections |
| Machinery Manufacturing | Conveyor frames, equipment bases, hydraulic support structures |
| Bridge & Infrastructure | Pedestrian bridge railings, sign gantry columns, drainage channel frames |
Where Dimensional Tolerance Decides Whether Your Frame Goes Together
A ±1% tolerance on a 300×500mm black rectangular steel tube means the difference between bolt holes aligning on-site and a full re-cut at the fabrication yard.
When procurement teams source black rectangular steel tube supplier options from trading companies rather than mills, wall thickness often drifts beyond acceptable limits — especially on the 0.5–2.0mm range where every tenth of a millimeter affects weld fit-up and load capacity. I have seen entire container loads of 25×25mm tubes rejected at a Southeast Asian port because the actual wall thickness measured 0.45mm against a 0.5mm nominal spec, and the corner radius exceeded 2t, making the tubes unsuitable for the curtain wall framing they were intended for. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed structural hollow sections] The problem compounds when multiple containers arrive with inconsistent dimensions — fabricators cannot batch-cut, weld jigs require constant recalibration, and project timelines slip.
Matching Hot-Rolled Black Rectangular Tubes to Structural Frame Requirements
Hot-rolled black rectangular steel tube sections in Q235 and Q345 grades carry higher residual stress profiles than cold-formed alternatives, which makes them suitable for primary load-bearing members in portal frames and multi-story building structures where deflection limits matter. The oiled black surface provides short-term corrosion protection during transit and on-site storage — sufficient for enclosed structural applications where final painting or fireproofing will be applied. As a black rectangular steel tube supplier producing sections up to 300×500mm with wall thickness reaching 30mm, we handle the heavy structural sizes that most stockholders cannot supply without weeks of lead time.
Engineering Compliance and Certification Pathways
Structural hollow sections shipped to EU markets must conform to EN10219 (cold-formed) or EN10210 (hot-formed) with CE marking under the Construction Products Regulation — and customs authorities increasingly request the Declaration of Performance at the point of entry. [NEED_CITE: CE marking requirements for structural steel hollow sections under EU Construction Products Regulation] For North American projects, ASTM A500 Grade B or C certification satisfies AISC fabrication standards, while JIS G3466 applies to projects in Japan and Southeast Asia following Japanese engineering specifications. Our in-house physical and chemical laboratory tests every heat for dimensional accuracy, mechanical properties, and chemical composition before release, ensuring that the mill test certificate matches the material physically loaded into the container. Third-party inspection by SGS or BV is available for projects requiring independent verification.
Steel Grade Selection and Hot-Rolling Process Fundamentals
The Q-series grades (Q195 through Q345) follow the Chinese GB/T 700 and GB/T 1591 system where the number indicates minimum yield strength in MPa — Q235 delivers approximately 235 MPa yield for general structural use, while Q345 provides higher strength for heavily loaded members. These map broadly to S235JR and S355JR in the EN system and ASTM A36 and A572 Grade 50 in the American system, though exact chemical composition and impact testing requirements differ between standards. [NEED_CITE: steel grade equivalence between EN, ASTM, and GB standards for structural hollow sections] Hot rolling at temperatures above the recrystallization point produces uniform grain structure through the full wall thickness — critical for sections above 16mm where cold-forming cannot achieve consistent mechanical properties. The black oiled surface treatment applies a thin film of protective oil after cooling, preventing flash rust during the typical 4–8 week window between production and final surface preparation at the fabrication shop.
The Hidden Cost of Sourcing the Wrong Grade or Unverified Thickness
Ordering Q235 material when the structural engineer specified Q345 means the fabricator discovers the mismatch only after cutting — and the entire batch becomes non-conforming material that cannot be used without redesign approval. [NEED_CITE: consequences of steel grade substitution in structural engineering projects] Similarly, wall thickness below the specified tolerance triggers rejection under EN10219 or ASTM A500 inspection protocols, and the cost of returning or replacing material on an active construction site far exceeds the original price difference between a verified supplier and an unverified broker. Certification gaps create a different category of cost: containers held at EU ports without proper CE documentation under EN10210 or EN10219 face demurrage charges, re-export costs, or forced destruction — none of which the mill or trading company absorbs.
Procurement Confidence Through Direct Mill Capability
As a black rectangular steel tube supplier operating our own production facility, we eliminate the markup layers that trading companies add to mill-exit prices — the quotation you receive reflects actual production cost plus reasonable margin, not a chain of intermediaries each taking a percentage. Our 41 invention patents include China’s original sharp-corner rectangular tube technology, which produces true right-angle corners with minimal radius for architectural facade applications where standard rounded-corner tubes create visible gaps at connection points. The product range covers over 2,800 specifications across square, rectangular, and round sections with wall thickness up to 30mm — meaning your 20×40mm light gauge tubes and 300×500mm heavy structural sections ship from a single source with consistent quality documentation. Full international certifications including ISO 9001:2015, Lloyd’s CE under EN10210 and EN10219, Singapore FPC, and SGS/BV verification satisfy the compliance requirements of regulated markets across the EU, Middle East, and Southeast Asia. Custom non-standard sizes, cut-to-length service, and professional container loading with anti-damage measures ensure that material arrives at your site in the condition it left our mill.
Documentation & Compliance
- Mill Test Certificate documenting Q235/Q345 chemical composition and mechanical properties per GB/T 6728 or EN10219 as specified
- CE Certificate of Conformity under EN10210 (hot-formed) or EN10219 (cold-formed) for EU market customs clearance
- ISO 9001:2015 Quality Management System certificate covering production, inspection, and delivery processes
- SGS or BV third-party inspection report verifying dimensional tolerance, surface quality, and material traceability before shipment
- Heat number traceability linking each bundle to its original melt chemistry and mechanical test results
- Complete customs documentation including packing list, bill of lading, and certificate of origin for import clearance
Packaging, Loading & Delivery
- Hot-rolled black rectangular tubes bundled with high-tensile steel strips at intervals preventing bundle separation during crane handling and ocean transit
- Oiled surface protection applied immediately after production to prevent flash rust on black finish tubes during the 30–60 day typical sea freight window
- Container loading optimized for 20ft and 40ft open-top or flat-rack configurations based on tube length (3–12m) and cross-section dimensions to maximize payload per shipment
- Cut-to-length service available for 3m, 5.8m, 6m, and 12m standard lengths matching container internal dimensions and reducing on-site cutting waste
- Heat number and steel grade stenciled on each bundle with weather-resistant marking for on-site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional container loading supervision to prevent surface damage and dimensional deformation during transit
Getting Your Quotation and Material Certification Started
Submit your specification sheet including section dimensions, wall thickness, steel grade, surface treatment preference, total tonnage, and destination port — our technical team responds within 12 hours with unit pricing, production lead time, and available mill test certificate formats. For non-standard sizes outside the 20×40mm to 300×500mm range or wall thickness beyond 30mm, we provide custom production feasibility confirmation and tooling requirements within 24 hours. Certification and compliance documentation including CE marking, EN10219/EN10210 test reports, and third-party inspection arrangements are confirmed at the quotation stage so there are no surprises at customs.
Frequently Asked Questions
Q: What is the difference between Q235 and Q345 steel grades for black rectangular steel tubes?
A: Q235 follows GB/T 700 and provides minimum 235 MPa yield strength for general structural applications, while Q345 follows GB/T 1591 and delivers higher yield strength suitable for heavily loaded structural members. Both grades are available in black oiled surface treatment and can be produced to EN10219 or ASTM A500 dimensional standards.
Q: Can you provide CE certification for black rectangular steel tubes shipped to the European Union?
A: Yes, our hot-formed rectangular hollow sections carry CE marking under EN10210, and cold-formed sections comply with EN10219. The CE certificate, Declaration of Performance, and factory production control documentation are provided with every shipment to EU destinations.
Q: What is the minimum order quantity for custom non-standard sizes?
A: The minimum order quantity is 1 Ton for standard specifications from our 2,800+ size range. Custom non-standard sizes outside the published range require minimum production runs that we confirm during the quotation stage based on your specific dimensions and tonnage.
Q: How does the black oiled surface treatment protect tubes during shipping and storage?
A: The oil film applied after hot rolling provides temporary corrosion protection preventing flash rust formation during typical sea freight periods of 30–60 days and on-site storage before final surface preparation. For longer storage periods or marine environments, pre-galvanized or hot-dipped galvanized options are available.
Q: Do you arrange third-party inspection before shipment?
A: Yes, SGS and BV third-party inspection services are available upon request. The inspection covers dimensional verification, surface quality assessment, witness testing of mechanical properties, and material traceability confirmation. The inspection report is provided before container sealing.
Get Your Black Rectangular Steel Tube Quote with Full Mill Certification
Send your project specifications to our technical team and receive pricing, production schedule, and material certification details within 12 hours.
SD XJY Pipe — Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjypipe.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
