Description
Factory-Direct Hollow Section Supply — Vertically integrated steel mill and fabrication workshop eliminate third-party sourcing gaps for Q235 Q345 Q355 square and rectangular steel tube orders.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 Q345 Q355 Square and Rectangular Steel Tube |
| Product Type | Square / Rectangular / Round / Deformed Hollow Section (SHS/RHS) |
| Steel Grade | Q195, Q235, Q345, Q355, Gr.B–Gr.50, DIN-S235JR, JIS-SS400, JIS-SPHC, BS-040A10, 10#–45# |
| Standard | ASTM, ASTM A53, GB/T, DIN, JIS, BS |
| Section Shape | Square, Rectangular, Round, Deformed |
| Size Range (Side Length / OD) | 10–3000 mm |
| Wall Thickness | 0.6–15 mm |
| Technique | Hot Rolled / Cold Rolled / ERW |
| Surface Treatment | Black Annealing / Bright Annealing / Galvanized Coated / Oiled |
| Tolerance | ±0.01% |
| Length | Standard or as required |
| Ends | Plain |
| Application | Steel structures, construction frames, fluid pipeline, petroleum and natural gas industry, drilling, machinery, furniture, interior decoration |
| MOQ | 20 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial & Industrial Construction | Building frames, column-beam assemblies, warehouse portal frames, mezzanine platforms |
| Infrastructure & Civil Engineering | Bridge handrails, highway gantry supports, sound barrier posts, tunnel reinforcement frames |
| Oil & Gas / Fluid Transport | Low-pressure pipeline systems, drilling support structures, process pipe racks |
| Machinery & Equipment | Conveyor frames, crane booms, agricultural machinery chassis, equipment support bases |
| Furniture & Interior | Display shelving structures, decorative screen frames, curtain wall sub-frames |
What Negative Wall-Tolerance Really Costs on a Structural Frame Order
A tube that passes visual inspection at the port can still fail third-party re-testing at the job site.
I once shipped a batch of RHS to a warehouse project in Saudi Arabia. The wall thickness had drifted deep into negative tolerance during cold forming. The client’s third-party inspector caught it at Jebel Ali — the entire lot was held. That single incident taught me that tolerance control matters more than unit price when structural integrity is on the line. On a Q235 Q345 Q355 square and rectangular steel tube order, the gap between nominal and actual wall thickness directly affects load-bearing calculations, welding penetration depth, and corrosion allowance over the structure’s design life. When fabricators source raw material from third-party mills, certification chains break and dimensional consistency becomes a gamble. [NEED_CITE: EN 10219 cold-formed structural hollow section tolerance requirements]
Matching Hollow Section Profiles to Structural Load Paths
Square and rectangular hollow sections offer symmetrical or directional moment of inertia, making them efficient for compression members, beam-columns, and truss chords. Q235 grades suit general construction frames where moderate yield strength suffices, while Q345 and Q355 grades serve heavier industrial structures requiring higher load capacity. The 10–3000 mm side-length range covers everything from light furniture frames to large-span portal rafters. Our vertically integrated production line — from billet to finished hollow section — ensures that every Q235 Q345 Q355 square and rectangular steel tube shipped carries consistent chemistry and dimensional data traceable to a single heat number.
Engineering Compliance Across International Standards
Structural hollow sections destined for EU markets must conform to EN 10210 (hot-finished) or EN 10219 (cold-formed) standards, with CE marking mandatory for load-bearing applications. North American projects typically require ASTM A500 or A53 compliance, while Middle East and African infrastructure specs often accept GB/T or JIS equivalents with mill test certification. The Q235 Q345 Q355 grade family maps closely to S235JR / S355JR under EN standards and Gr.B–Gr.50 under ASTM, but formal equivalence documentation must accompany each shipment to avoid customs delays. [NEED_CITE: steel grade equivalence between Chinese GB, European EN, and American ASTM standards] Surface treatment selection — galvanized for outdoor exposure, oiled for indoor storage, black annealed for subsequent painting — must align with the project’s corrosion environment and downstream fabrication sequence.
Understanding Grade Selection and Forming Process
The Q-series (Q195, Q235, Q345, Q355) follows the Chinese GB system where the number after “Q” indicates minimum yield strength in MPa. Q235 serves as the workhorse grade for general structures; Q345 and Q355 provide progressively higher yield strength for heavily loaded columns and long-span beams. The S-series (S235JR per DIN/EN) and ASTM Gr.B–Gr.50 represent equivalent performance tiers under European and American specifications. Hot-rolled hollow sections offer thicker walls and superior corner properties for heavy structural use, while cold-rolled and ERW processes deliver tighter dimensional tolerance and smoother surface finish for architectural and machinery applications. Wall thickness from 0.6 mm to 15 mm covers light gauge framing through heavy industrial sections. The ±0.01% tolerance specification ensures precision fit-up for welded connections and bolted assemblies.
Hidden Costs of Unverified Material Sourcing
Purchasing Q235 Q345 Q355 square and rectangular steel tube from traders who source from unverified mills creates compounding risks: material certificates may not match actual chemistry, wall thickness may fall below minimum spec under the guise of “commercial tolerance,” and third-party inspectors at destination ports can reject entire shipments. The cost of re-melting, re-shipping, or redesigning structural connections far exceeds any initial price saving. Engineering codes such as EN 1993 and AISC 360 require verified material properties for structural calculations — undocumented steel cannot be legally used in load-bearing applications in most jurisdictions. [NEED_CITE: structural steel material verification requirements under EN 1993 and AISC 360]
Procurement Confidence Through Vertical Integration
XJY Structure operates its own steel mill with three production lines and maintains over 2,800 raw material specifications in inventory, meaning every Q235 Q345 Q355 square and rectangular steel tube order is fulfilled from billet to finished product under one roof. Our in-house metallurgical laboratory issues mill test certificates for every heat, and we welcome SGS, BV, or TÜV third-party inspections before shipment. The full size range from 10 mm to 3000 mm side length and 0.6 mm to 15 mm wall thickness allows consolidated procurement across multiple project packages — no need to split orders among specialty suppliers. We hold CE certification for EN 10210 and EN 10219, ISO 9001 quality management, and certified welding procedures (WPS/PQR) for any downstream fabrication. Professional loading plans and container optimization ensure that oversized sections arrive without transit damage.
Documentation & Compliance
- Mill test certificate documenting Q235/Q345/Q355 chemical composition and mechanical properties per GB/T, with heat number traceability
- CE certificate confirming EN 10210 hot-finished or EN 10219 cold-formed hollow section compliance for EU market entry
- ISO 9001 quality management system certificate covering full production from raw material procurement to finished tube delivery
- SGS or BV third-party inspection report available upon request, covering dimensional checks, surface quality, and coating thickness verification
- Material traceability report linking each bundle to its original heat number, rolling record, and test results
- Complete customs documentation package: commercial invoice, packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235 Q345 Q355 square and rectangular steel tubes packed in seaworthy steel-strip bundles with edge protectors to prevent coating damage during ocean transit
- Galvanized-coated sections wrapped with waterproof paper and plastic film to preserve zinc layer integrity in humid port environments
- Container loading optimized by side-length grouping: 6 m standard lengths fit 20ft containers; 12 m lengths require 40ft open-top or flat-rack configuration
- Custom cut-to-length service available within the 10–3000 mm range, with each piece marked by heat number and steel grade for site identification
- FOB, CIF, and DDP shipping terms supported, with door-to-door logistics coordination for project sites in the Middle East, Southeast Asia, and Africa
Requesting a Fabrication-Ready Quotation
Share your project drawings (PDF or DWG), required steel grades, section dimensions, wall thickness, surface treatment preference, and destination port. Our engineering team responds within 24 hours with a detailed quotation covering material, fabrication, coating, packing, and shipping costs — along with a shop drawing timeline and production schedule. For non-standard dimensions or mixed-size orders, we provide material optimization and fabrication sequencing support before contract signing.
Frequently Asked Questions
Q: How do Q235, Q345, and Q355 grades map to European EN and American ASTM standards?
A: Q235 corresponds closely to S235JR (EN 10025) and ASTM A36 in yield strength range; Q345 aligns with S355JR and ASTM A572 Gr.50; Q355 matches S355JR under EN 10025-2. Formal equivalence documentation is provided with each shipment.
Q: What material certification documents are supplied with each order?
A: Every Q235 Q345 Q355 square and rectangular steel tube shipment includes a mill test certificate showing chemical composition and mechanical properties, traceable to the original heat number. Third-party inspection reports from SGS, BV, or TÜV are available upon request.
Q: Can non-standard dimensions be produced, and what is the minimum order quantity?
A: Custom sizes within the 10–3000 mm side length and 0.6–15 mm wall thickness range can be produced. The standard MOQ is 20 tons, which can be consolidated across multiple sizes and grades in a single order.
Q: When should I specify galvanized versus black annealed or oiled finish?
A: Galvanized coating is recommended for outdoor or high-humidity environments requiring long-term corrosion protection. Oiled finish suits indoor applications or tubes destined for further painting. Black annealed is selected when the customer will apply custom coating systems after delivery.
Q: How are large-section hollow sections packed and loaded for international shipment?
A: Sections are bundled with steel strips and edge protectors. Standard 6 m lengths fit 20ft containers; 12 m lengths require 40ft open-top or flat-rack containers. Loading plans are prepared to maximize container utilization and prevent transit deformation.
Get Your Project-Specific Quotation
Submit your drawings, steel grade requirements, and destination port to receive a detailed quotation with mill test certificate documentation and production schedule.
Contact: admin@xjystructure.com | WhatsApp/WeChat: +86 188 5315 7756
