Description
Factory-Direct SHS Production — XJY Structure operates its own steel mill with 3 production lines and over 2,800 raw material specifications, delivering Q355/S355 square hollow sections directly from raw slab to finished tube without third-party intermediaries.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q355/S355 SHS Square Steel Tube |
| Product Type | Square Hollow Section (SHS) |
| Steel Grade | Q355, S355, S235, S275, Gr.B, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square |
| Size Range | 19mm×19mm – 800mm×800mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | Welded (ERW) / Seamless |
| Surface Treatment | Black Painted / Galvanized / Varnish / Bare |
| Tolerance | ±10% |
| Ends | Plain / Beveled |
| Application | Construction structures / Building frames / Curtain wall / Support tubes / Structural pipe |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Steel frame structures, column and beam assemblies for office buildings and retail complexes |
| Industrial Facilities | Warehouse portal frames, mezzanine platforms, conveyor support structures |
| Infrastructure | Bridge railings, sound barrier supports, utility pole bases |
| Architectural Facades | Curtain wall mullions, canopy frames, decorative structural elements |
What Negative Tolerance Really Costs on a Structural Frame Order
A 0.8mm wall deviation on a 6mm SHS can trigger full-batch rejection at third-party inspection.
When buyers source Q355 S355 SHS square steel tube from trading companies rather than integrated mills, the material certification chain breaks somewhere between the steel slab and the finished tube. I have seen warehouse projects in the Middle East where theoretical weight invoicing masked severe negative tolerance — the actual wall thickness fell well below the specified 6mm, and SGS inspectors flagged the entire shipment. The result was three weeks of re-inspection delays, air-freighted replacement sections, and a strained relationship with the main contractor. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Section Dimensions to Structural Load Paths
Selecting the correct Q355 S355 SHS square steel tube size starts with understanding how the section geometry interacts with your structural load path. For portal frame columns in warehouse construction, the 200×200mm to 400×400mm range with wall thickness above 8mm provides the moment of inertia needed to resist lateral wind loads, while lighter sections in the 50×50mm to 150×150mm range serve adequately as purlin bracing or curtain wall supports. The flat faces of square hollow sections simplify connection design — bolted end plates and welded gussets sit flush against the surface without the rotational alignment issues that round tubes introduce. Our integrated production line covers the full 19×19mm to 800×800mm range, so project teams sourcing multiple section sizes from a single heat number maintain consistent material properties across the entire structural frame.
Engineering Compliance and Certification Requirements
Structural steel hollow sections used in load-bearing frames must comply with recognized engineering codes, and the certification package must travel with the material through customs and site inspection. [NEED_CITE: EN 10219 cold-formed welded structural hollow sections compliance framework] For European projects, EN 10219 certification with CE marking is mandatory, while North American specifications typically reference ASTM A500 Grade B or C. The Q355 grade under GB/T 3091 corresponds closely to S355 under EN standards, and our mill test certificates document the chemical composition and mechanical properties against the applicable standard for each order. Surface treatment selection also carries compliance weight — hot-dip galvanized coatings must meet minimum thickness requirements for corrosive environments, while black painted or bare finishes require clear documentation of the shop primer specification for site welding acceptance.
Steel Grade Selection and Manufacturing Process
The Q355 and S355 grades represent medium-tensile structural steels with higher yield strength than S235 or S275, making them the default choice for primary structural members where weight optimization matters. Within the Q-series and S-series designation systems, the number indicates the nominal yield strength in MPa, so S355 delivers higher load-bearing capacity per unit cross-section than S235 — allowing engineers to specify smaller sections and reduce overall structure weight. [NEED_CITE: steel grade equivalence between Chinese GB, European EN, and American ASTM standards] The ERW welded process produces square hollow sections by forming flat strip into a square profile and welding the longitudinal seam, offering cost efficiency for standard structural applications, while seamless tubes eliminate the weld seam entirely for higher-pressure or critical fatigue applications. Surface treatment follows fabrication — galvanized coatings provide sacrificial zinc protection for outdoor exposure, black paint suits interior or temporarily protected conditions, and bare sections ship with mill oil for workshop priming at destination.
Hidden Costs of Sourcing Without Material Traceability
Procuring Q355 S355 SHS square steel tube without verified mill test certificates creates compounding risks downstream. Material that cannot be traced to a specific heat number fails third-party inspection at the port of discharge, triggering customs holds and demurrage charges. Wall thickness that exceeds permissible negative tolerance under EN 10219 or ASTM A500 reduces the section modulus below design assumptions, forcing structural engineers to either accept reduced safety margins or order replacement material at premium air-freight rates. [NEED_CITE: consequences of non-compliant structural steel in international construction projects] Welding procedure qualifications become void if the base metal chemistry deviates from the certified grade, and coating adhesion tests fail on surfaces with undocumented mill scale or contamination.
Why Project Teams Source from an Integrated Mill-Fabricator
XJY Structure controls the entire production chain from raw steel slab to finished fabricated component, eliminating the certification gaps that occur when material passes through multiple intermediaries. Our own steel mill operates 3 production lines covering over 2,800 raw material specifications, so every Q355 S355 SHS square steel tube ships with a mill test certificate traceable to the original heat number. The fabrication workshop holds certified welding procedures under AWS and EN standards, with qualified welders performing shop drawing review, CNC cutting, and assembly for projects requiring fabricated components beyond raw tube supply. Third-party inspection through SGS or BV is available at every production stage, and our quality documentation package includes WPS, PQR, weld maps, dimensional inspection reports, and coating thickness measurements — the complete file that project managers need for handover to the client.
Documentation & Compliance
- Mill test certificate documenting Q355/S355 chemical composition and yield strength per GB/T 3091 or EN 10219
- CE certificate confirming compliance with EN 10210 for hot-finished or EN 10219 for cold-formed structural hollow sections
- ISO 9001 quality management system certificate covering the full production scope from steelmaking to finished tube
- SGS or BV third-party inspection report verifying dimensional accuracy, wall thickness, and surface treatment compliance
- Material traceability documentation linking each bundle to its heat number, production date, and test results
- Export customs documents including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Q355/S355 SHS tubes bundled with steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized sections wrapped with waterproof paper and plastic film to preserve the zinc coating against moisture exposure
- Random length and fixed-length tubes loaded with optimized container stowage plans to maximize payload per 20ft or 40ft container
- Beveled-end sections separated by wooden spacers to protect the weld preparation geometry during transport
- Each bundle marked with heat number, steel grade, size specification, and production batch for site identification
- Delivery terms available as FOB, CIF, or DDP with professional oversized cargo loading and door-to-door logistics coordination
Starting Your Procurement Process
Submit your project drawings, required steel grades, section dimensions, quantity, and destination port to receive a detailed quotation including material cost, fabrication charges, surface treatment, and shipping. Our engineering team reviews your specifications within 24 hours and provides shop drawing confirmations before production begins. For non-standard sizes or custom fabrication requirements, we prepare technical proposals covering material optimization and production sequencing.
Request Your Q355 S355 SHS Quotation
Share your project specifications, steel grades, and quantity to receive pricing with mill test certificates within 24 hours.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
