Description
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B / Q355B Hot Rolled Square and Rectangular Carbon Steel Tube |
| Product Type | Square and Rectangular Steel Tube (Seamless / Welded Hollow Sections) |
| Steel Grade | Q195, Q215, Q235, Q355, #20, #45 |
| Standard | EN 10219, EN 10210, GB/T 6728, JIS G3466, ASTM A500, ASTM A36, ASTM A53 |
| Section Shape | Square / Rectangular / Round |
| Size Range | Square pipe 20×20 mm – 500×500 mm; Rectangular pipe 20×40 mm – 300×500 mm |
| Wall Thickness | 1.2 mm – 20 mm (up to 30 mm available) |
| Length | 3 m – 12 m (random / customized) |
| Technique | Hot Rolled / Welded |
| Surface Treatment | Black (oiled / non-oiled), Pre-galvanized (40–80 g/m²), Hot-dip galvanized (200–600 g/m²) |
| Tolerance | ±1% |
| Ends | Plain / Beveled |
| Processing Service | Bending, Welding, Decoiling, Punching, Cutting |
| Application | Construction, Steel structure, Solar structure, Fence, Greenhouse, Glass curtain wall, Machinery, Shipbuilding |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Building frames, column supports, beam structures, roof trusses |
| Steel Structure Engineering | Welded fabrication for industrial warehouses, workshop frames, platform structures |
| Architectural Facade | Glass curtain wall framing, decorative structural elements, sharp-corner rectangular tubes for exterior cladding |
| Solar & Renewable Energy | Solar panel mounting structures, ground screw supports, racking systems |
| Infrastructure & Civil | Highway railings, bridge handrails, airport terminal structures, fence posts |
| Machinery & Equipment | Conveyor frames, machine base structures, hydraulic support columns, automobile chassis components |
Where Steel Grade Equivalence Decides Customs Clearance and Site Acceptance
Ordering Q235B when the drawing specifies S235JR — or specifying ASTM A500 Grade B when the mill produces Q355B — creates documentation gaps that block EU customs and fail third-party inspection at destination.
Procurement teams across Southeast Asia and the Middle East frequently receive project drawings referencing EN 10219 or ASTM A500, then place orders using Chinese domestic grade names. The material arrives physically acceptable, but the Mill Test Certificate lists Q235B while the contract demands S235JR. SGS inspectors flag the grade mismatch. Customs in Rotterdam or Dubai hold the container. The buyer pays demurrage, requests replacement documents, or — worst case — returns the shipment. [NEED_CITE: steel grade equivalence between EN 10219 and GB/T 6728 standards]
Beyond documentation, the mechanical properties behind these grades differ. Q235B and S235JR share similar yield strength ranges, but their chemical composition limits — particularly carbon, manganese, and sulfur content — follow different testing protocols. A Hot Rolled Square Rectangular Carbon Steel Tube Supplier who maps these equivalences at the inquiry stage prevents the mismatch before production begins.
How Q235B and Q355B Hollow Sections Match Structural Load Requirements
Hot rolled square and rectangular carbon steel tubes in Q235B serve general construction framing where yield strength requirements remain moderate — typical warehouse columns, greenhouse frames, and fence posts. When the structural engineer specifies higher load-bearing capacity for bridge supports, machinery bases, or multi-story building frames, Q355B delivers increased yield strength without changing the section geometry. The Hot Rolled Square Rectangular Carbon Steel Tube Supplier provides both grades from the same production line, allowing project buyers to consolidate orders rather than splitting purchases across multiple mills. Wall thickness from 1.2 mm to 20 mm covers light-gauge framing through heavy structural columns, with ±1% tolerance meeting EN 10219 dimensional requirements for welded hollow sections.
Engineering Compliance: EN 10219, ASTM A500, and Project Certification
Structural hollow sections exported to European markets must comply with EN 10219 for cold-formed welded tubes or EN 10210 for seamless and welded sections. These standards define chemical composition limits, mechanical property testing methods, and dimensional tolerances that differ from Chinese GB/T 6728 in specific areas — particularly impact testing temperatures and elongation requirements. [NEED_CITE: EN 10219 cold-formed hollow section technical delivery conditions] North American projects referencing ASTM A500 Grade B or C require different certification documentation, including Charpy impact test results at specified temperatures. The Hot Rolled Square Rectangular Carbon Steel Tube Supplier maintains Lloyd’s CE certification under EN 10210 and EN 10219, Singapore FPC approval, and ISO 9001:2015 registration — ensuring that mill test certificates carry the marks customs authorities and project inspectors require. For projects demanding third-party verification, SGS or BV inspection arranges before shipment, with heat number traceability documented from raw material through finished tube.
Understanding Steel Grade Systems: Q-Series, S-Series, and ASTM Equivalence
Chinese steel grades Q235B and Q355B follow GB/T 700 and GB/T 1591 standards, where the “Q” prefix indicates yield strength in MPa — Q235B yields at 235 MPa minimum, Q355B at 355 MPa minimum. European EN standards use the “S” prefix for structural steel: S235JR, S275JR, S355JR, with additional letters indicating impact test quality (J0 for 0°C, J2 for -20°C). ASTM A500 Grade A, B, and C represent increasing yield and tensile strength levels for cold-formed welded structural tubing. While Q235B approximately corresponds to S235JR and ASTM A53 Grade B, and Q355B aligns with S355JR and ASTM A500 Grade B, exact equivalence requires chemical composition comparison — not just yield strength matching. [NEED_CITE: steel grade equivalence mapping between GB EN and ASTM standards] The Hot Rolled Square Rectangular Carbon Steel Tube Supplier provides cross-reference documentation at inquiry stage, confirming which Chinese grade meets the specified EN or ASTM requirement for the project’s certification needs.
Surface treatment selection follows application environment. Black oiled tubes suit indoor structural framing where corrosion protection comes from paint systems applied after fabrication. Pre-galvanized tubes with 40–80 g/m² zinc coating provide basic corrosion resistance for sheltered outdoor applications like greenhouse frames. Hot-dip galvanized tubes with 200–600 g/m² coating handle aggressive environments — coastal solar structures, chemical plant platforms, marine facility handrails — where long-term corrosion resistance justifies the higher material cost.
The Hidden Cost of Negative Tolerance and Missing Certification
A 0.5 mm negative tolerance deviation on a 4 mm wall thickness tube reduces actual weight by over 12%, directly compromising structural load capacity. When the project specification calls for 4 mm minimum wall per EN 10219, and the delivered tubes measure 3.5 mm average, the structural engineer rejects the batch — regardless of whether the tubes “look acceptable.” Replacement costs include new material, return shipping, project delay penalties, and re-fabrication if the original tubes were already cut. [NEED_CITE: dimensional tolerance requirements for structural hollow sections] Missing CE marking on tubes destined for EU construction sites blocks customs clearance; missing mill test certificates fail third-party inspection at destination. The Hot Rolled Square Rectangular Carbon Steel Tube Supplier maintains in-house physical and chemical laboratories, testing every heat for dimensional accuracy, mechanical properties, and chemical composition before release — ensuring that tolerance claims match actual production.
Why Project Buyers Source from Shandong Xin Jiyuan
Shandong Xin Jiyuan holds 41 invention patents, including China’s first sharp-corner rectangular tube technology — filling the gap for architectural facade contractors who need true right-angle corners rather than the rounded corners (R≥2t) standard rectangular tubes produce. The factory operates 3 production lines covering 2,800+ specifications with wall thickness up to 40 mm, allowing buyers to consolidate square tubes, rectangular tubes, round pipes, and section steel (H-beam, I-beam, channel, angle bar) in a single order. Full international certifications — ISO 9001:2015, Lloyd’s CE under EN 10210 and EN 10219, Singapore FPC, and SGS/BV verification — ensure documentation supports customs clearance in regulated markets. The in-house laboratory performs dimensional, mechanical, and chemical testing per project requirements, with mill test certificates issued per EN 10204 3.1 or 3.2 standards. Custom non-standard sizes, cutting, marking, and professional container loading with anti-damage measures serve export orders to 50+ countries across Europe, North America, Middle East, and Southeast Asia.
Documentation & Compliance
- Mill test certificate documenting Q235B or Q355B chemical composition and mechanical properties per GB/T 700 or GB/T 1591, with cross-reference to EN 10219 or ASTM A500 equivalence
- CE certificate under EN 10210 and EN 10219 for structural hollow sections exported to European Union markets
- ISO 9001:2015 quality management system certificate covering hot rolled and welded square rectangular tube production
- SGS or BV third-party inspection report available upon request, covering dimensional verification, visual inspection, and witness testing
- Material traceability by heat number from raw material coil through finished tube, documented in mill test certificate
- Customs documentation including packing list, bill of lading, and certificate of origin for import clearance
Packaging, Loading & Delivery
- Hot rolled black square and rectangular tubes bundled with steel strips, edges protected to prevent coating damage during ocean transit
- Pre-galvanized and hot-dip galvanized tubes packed with plastic sheeting separation and wooden pallets to preserve zinc coating integrity
- Container loading optimized for 6 m and 12 m lengths, with inner tubes nested to maximize 20ft and 40ft container capacity
- Custom cutting service available for non-standard lengths from 3 m to 12 m, with cut ends deburred and marked per drawing requirements
- Heat number, steel grade, and size marked on each tube bundle with stenciled identification for site traceability
- FOB, CIF, and DDP shipping terms available, with professional loading supervision to prevent bending and surface damage
Ready to Confirm Specifications and Receive Mill Test Certificates
Submit your project drawing or specification sheet — including section dimensions, wall thickness, steel grade requirement (Q235B/Q355B or EN/ASTM equivalent), surface treatment, quantity, and destination port — to receive a detailed quotation with unit pricing, production lead time, and mill test certificate sample. For non-standard sizes or sharp-corner rectangular tubes requiring custom tooling, the engineering team provides feasibility confirmation and tooling timeline within 12 hours.
Request Quotation with Material Certification
Send specifications to admin@sdxjypipe.com or contact via WhatsApp at +86 188 5315 7756 for pricing, certification confirmation, and delivery schedule.
Frequently Asked Questions
Q: How do Q235B and Q355B compare to S235JR, S355JR, and ASTM A500 grades?
A: Q235B approximately corresponds to S235JR and ASTM A53 Grade B in yield strength range, while Q355B aligns with S355JR and ASTM A500 Grade B. However, exact equivalence requires chemical composition comparison — particularly carbon, manganese, sulfur, and phosphorus limits — which differ between GB, EN, and ASTM standards. We provide cross-reference documentation at inquiry stage to confirm grade equivalence for your project specification.
Q: Can you provide mill test certificates and arrange third-party inspection?
A: Yes. Mill test certificates issue per EN 10204 3.1 standard, documenting chemical composition and mechanical properties for each heat number. Third-party inspection by SGS or BV arranges before shipment upon request, covering dimensional verification, visual inspection, and witness testing per project requirements.
Q: What is the minimum order quantity for custom non-standard sizes and sharp-corner rectangular tubes?
A: Standard specifications ship from stock with 1 ton minimum order. Custom non-standard sizes and sharp-corner rectangular tubes require production scheduling, with minimum order quantities depending on section dimensions and wall thickness. Contact us with your specific requirements for MOQ confirmation and production timeline.
Q: Which surface treatment suits my application — pre-galvanized, hot-dip galvanized, or black oiled?
A: Black oiled tubes suit indoor applications where paint systems provide corrosion protection after fabrication. Pre-galvanized tubes with 40–80 g/m² zinc coating handle sheltered outdoor applications like greenhouse frames. Hot-dip galvanized tubes with 200–600 g/m² coating serve aggressive environments — coastal structures, chemical plants, marine facilities — requiring long-term corrosion resistance.
Q: Do your products carry CE marking for European Union import under EN 10210 and EN 10219?
A: Yes. Our structural hollow sections carry Lloyd’s CE certification under EN 10210 and EN 10219 standards, with mill test certificates documenting compliance. Singapore FPC certification also available for projects requiring additional approval. CE marking ensures customs clearance and project acceptance in EU regulated markets.
Get Your Project Quote with Full Certification Package
Email your specifications to admin@sdxjypipe.com or WhatsApp +86 188 5315 7756 to receive pricing, mill test certificate samples, and delivery confirmation within 12 hours.
