Description
Factory-Direct Q355/S355 SHS Supply — Each Q355/S355 square steel tube is rolled, tested, and certified in-house before leaving Jinan, eliminating middlemen markups and traceability gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q355/S355 SHS Square Steel Tube |
| Product Type | Square Steel Tube (Seamless & Welded) |
| Steel Grade | Q355, S355, Gr.B, S235, S275, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square |
| Size Range | 19mm×19mm – 800mm×800mm |
| Wall Thickness | 1 – 30mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | Welded (ERW) / Seamless |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±10% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Curtain walls / Support tubes / Building structures |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Industrial plant steel frames, pipe rack supports, equipment platform columns |
| Construction Companies | High-rise building columns, curtain wall mullions, mezzanine floor beams |
| Machinery Manufacturers | Conveyor system frames, crane boom sections, automated storage rack uprights |
| Infrastructure Developers | Bridge handrail posts, sound barrier supports, solar mounting structures |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A 1mm negative tolerance deviation on a 10mm wall SHS can shift load-bearing capacity by double-digit percentages.
When a container of Q355/S355 square steel tube arrives at a Middle East job site and the ultrasonic thickness gauge reads 8.7mm instead of the specified 10mm, the entire batch fails structural acceptance. The contractor faces three choices: scrap the steel, negotiate a steep discount, or wait weeks for replacement — all while cranes sit idle. Inconsistent wall thickness is rarely visible at the mill, but it becomes catastrophic once welded into a load-bearing frame. [NEED_CITE: EN 10219 cold-formed hollow section requirements]
How Q355/S355 SHS Matches Structural Frame Demands
Square hollow sections in Q355 and S355 grades deliver equal resistance on all four faces, making them ideal for columns and compression members where buckling direction is unpredictable. The 19×19mm to 800×800mm size range covers everything from light-gauge curtain wall supports to heavy industrial columns. ERW welded variants serve general structural work at lower cost, while seamless options handle higher pressure or dynamic loading. Each Q355/S355 square steel tube leaves the mill with documented chemistry and mechanical test results tied to its heat number.
Engineering Compliance and Certification Pathways
Structural engineers specifying Q355/S355 SHS typically require compliance with EN 10219 for cold-formed welded sections or ASTM A500 for North American projects. The ±10% wall thickness tolerance aligns with EN 10219 dimensional requirements, but actual mill practice must hold tighter to pass third-party inspection. CE certification under EN 10210/EN 10219 is mandatory for EU customs clearance, while SGS or BV inspection reports satisfy Middle East and Southeast Asian project owners. Fixed lengths of 6m and 12m reduce on-site cutting waste, while random lengths serve non-standard frame heights. [NEED_CITE: steel grade equivalence between EN and ASTM standards]
Steel Grade Selection and Manufacturing Process
Q355 (Chinese GB standard) and S355 (European EN standard) occupy the same yield strength tier — both deliver higher load capacity than S235 or S275 without the cost premium of high-strength low-alloy grades. For projects spanning multiple regions, Gr.B (ASTM A500) serves as the North American equivalent. ERW welded tubes suit static structural applications where cost efficiency matters; seamless tubes handle dynamic or pressure-loaded conditions. Surface treatment selection depends on environment: galvanized coatings protect outdoor infrastructure for decades, black painting serves indoor structural frames, and bare tubes work when field-applied fireproofing or additional coating is planned. Wall thickness from 1mm to 30mm covers light decorative frames to heavy industrial columns, with tighter tolerance control on thicker walls where negative deviation carries greater structural risk.
The Hidden Price of Unverified Steel Procurement
Purchasing Q355/S355 SHS without mill test certificates or third-party inspection creates downstream liabilities that dwarf the initial savings. Material traceability gaps mean failed structural audits; missing CE documentation triggers customs holds at Rotterdam or Jebel Ali; negative tolerance violations force costly re-engineering or complete frame replacement. Engineering standards like EN 10219 and ASTM A500 exist precisely because unverified steel has caused structural failures worldwide. [NEED_CITE: consequences of non-compliant structural steel in construction projects]
Why Project Procurement Teams Choose Xin Jiyuan
Every Q355/S355 square steel tube undergoes chemical composition analysis and mechanical testing in our in-house laboratory before shipment — no batch leaves without a corresponding mill test certificate. Our 2,800+ specification range means you source SHS, RHS, round pipe, and plate from a single mill, cutting coordination overhead and consolidating freight. The 41 patented technologies include sharp-corner rectangular tube production that fills global specification gaps. CE EN10210/EN10219, ISO 9001:2015, and Singapore FPC certifications clear customs across EU, North America, and Southeast Asian markets. Custom non-standard sizes and fixed-length cutting serve projects where standard catalog dimensions create waste. Professional loading plans optimize container weight for 6m and 12m lengths, reducing per-ton freight costs.
Documentation & Compliance
- Mill test certificate documenting Q355/S355 chemical composition and yield strength per ASTM A500 or GB/T 3091
- CE certificate confirming EN 10210/EN 10219 compliance for EU market customs clearance
- ISO 9001:2015 quality management certificate covering production and testing processes
- SGS or BV third-party inspection report available upon request for project owner verification
- Material traceability by heat number linking each tube to its original melt and test results
- Complete customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q355/S355 SHS bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized tubes receive additional plastic wrapping to preserve zinc coating integrity
- Container loading plans optimized for 6m and 12m fixed lengths to maximize weight utilization per 20ft or 40ft container
- Random length tubes cut to project-specified dimensions to minimize on-site waste
- Heat number and steel grade stenciled on each bundle for site identification and traceability
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to 50+ countries
Start Your Q355/S355 SHS Procurement
Submit your specification sheet — including size, wall thickness, steel grade, quantity, and destination port — and receive a detailed quotation with mill test certificate samples within 12 hours. Our engineering team reviews your requirements to confirm dimensional compliance and certification pathways before production begins.
Request Your Q355/S355 SHS Quotation Today
Send your specifications via email to admin@sdxjysteel.com or contact us at +86 188 5315 7756 (WhatsApp/WeChat available) to receive pricing, mill test certificate samples, and delivery timelines for your next structural steel procurement.
Frequently Asked Questions
Q: What is the difference between Q355 and S355 steel grades for square hollow sections?
A: Q355 (Chinese GB standard) and S355 (European EN standard) deliver equivalent yield strength and mechanical properties. Both grades suit structural applications requiring higher load capacity than S235 or S275. Your project specification or local building code determines which standard applies.
Q: Can you provide third-party inspection for Q355/S355 square steel tubes?
A: Yes. SGS and BV third-party inspections are available upon request. The inspection covers dimensional verification, wall thickness measurement, visual surface check, and review of mill test certificates before shipment.
Q: What certifications do you provide for EU market customs clearance?
A: We supply CE certification under EN 10210/EN 10219 for structural hollow sections, along with ISO 9001:2015 quality certificates and mill test certificates. These documents satisfy EU customs requirements and project owner specifications.
Q: What is the minimum order quantity for Q355/S355 SHS?
A: The MOQ is 5 tons per size specification. For mixed-size orders, we consolidate multiple specifications into a single shipment to meet project procurement needs while maintaining production efficiency.
Q: Do you offer custom non-standard sizes for square steel tubes?
A: Yes. Beyond our standard 19×19mm to 800×800mm range with 1-30mm wall thickness, we produce custom non-standard sizes based on your engineering drawings. Lead times for custom specifications are confirmed during quotation.
