Description
Factory-direct Q355 S355 square hollow structural section — every batch leaves our Jinan mill with original test certificates and ±10% wall-thickness tolerance verified by in-house lab.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q355/S355 Square Hollow Structural Section |
| Product Type | Square Steel Tube (Seamless & Welded) |
| Steel Grade | Q355, S355, S235, S275, STK400, Gr.B |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square |
| Size Range | 19 mm × 19 mm – 800 mm × 800 mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8 m / 6 m / 11.8 m / 12 m / Random Length |
| Technique | Welded (ERW) / Seamless |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±10% |
| Ends | Plain / Beveled (per customer request) |
| Application | Construction structures / Building frames / Curtain wall supports / Structural sections / Machinery frames |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Building frames, curtain wall supports, mezzanine structures |
| Industrial Facilities | Machinery frames, conveyor structures, equipment support bases |
| Infrastructure & EPC | Bridge railings, solar mounting structures, utility pole bases |
| Steel Fabrication Workshops | Column sections, truss chords, portal frame members |
What Wall-Thickness Tolerance Costs on a Structural Frame Order
A 12% negative tolerance deviation turns a 50-ton order into 2 tons of missing steel before the监理 even picks up a caliper.
Global buyers sourcing Q355 S355 square hollow structural section from fragmented suppliers routinely encounter wall thickness running well outside the ±10% envelope. The result: theoretical weight versus actual weighbridge weight diverges by entire tons per container, and site supervisors reject the lot outright. Material certificates listing one grade while spectrometer readings show another compound the problem — customs holds the cargo, the project schedule slips, and nobody at the trading company answers the phone. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]
Matching Section Dimensions to Structural Load Paths
Square hollow sections from 19×19 mm up to 800×800 mm cover everything from light gauge purlin bracing to heavy column bases in portal frames. The Q355 S355 square hollow structural section range in both ERW welded and seamless process lets specifiers choose based on pressure requirements and budget — ERW handles standard structural framing at lower cost, while seamless serves higher-stress nodes where weld-line integrity matters. Wall thickness from 1 mm to 30 mm means the same supplier can furnish both thin-gauge infill framing and thick-walled load-bearing columns without splitting the purchase order across multiple vendors.
Engineering Compliance and Certification Alignment
Structural engineers designing to EN 1993 or AISC 360 need material documentation that traces back to the heat number. Our Q355 S355 square hollow structural section ships with mill test certificates showing chemical composition and mechanical properties per the declared standard — whether that is ASTM A500 Grade C for North American projects or EN 10219 for European-spec work. CE certification under EN 10210/EN 10219 clears EU customs without supplementary testing, and SGS or BV third-party inspection before loading gives the project owner an independent verification layer. [NEED_CITE: steel grade equivalence mapping between EN 10219 and ASTM A500] Fixed-length cutting at 5.8 m, 6 m, 11.8 m, or 12 m with plain or beveled ends reduces on-site secondary processing and keeps weld prep consistent.
Steel Grade Selection and Manufacturing Process
The Q-series (Q355) and S-series (S235, S275, S355) designations follow Chinese GB and European EN systems respectively, with yield strength increasing through the S-grade sequence — S235 suits light non-critical framing, S355 handles primary structural members, and Q355 bridges the Chinese domestic standard with international procurement specs. STK400 and Gr.B cover JIS and ASTM markets where local code compliance is mandatory. ERW welded process forms the square profile from coil through continuous forming and high-frequency welding, offering cost efficiency for standard structural sections; seamless manufacturing eliminates the weld seam entirely, preferred for applications where internal corrosion or cyclic loading makes the weld line a potential failure point. Surface treatment selection — black painted for indoor dry environments, hot-dip galvanized for outdoor or humid exposure, varnished for temporary protection during transit, or bare for projects applying their own coating system — directly affects long-term maintenance cost. [NEED_CITE: hot-dip galvanizing coating thickness requirements for structural steel]
Hidden Costs of Procuring the Wrong Material
Ordering S355 and receiving material that tests as S275 means the structural engineer must either redesign the entire frame or reject the shipment — both options carry weeks of delay and significant cost. Missing or forged mill test certificates trigger customs holds at destination ports, particularly in markets with strict import documentation requirements. Wall thickness below the declared tolerance reduces load-bearing capacity and fails inspection, forcing complete replacement rather than partial acceptance. A Q355 S355 square hollow structural section sourced without proper traceability creates liability exposure that no amount of price savings can offset. [NEED_CITE: structural steel material traceability requirements for construction projects]
Why Project Buyers Source SHS Through Xin Jiyuan
Factory-direct pricing eliminates trading company markups — volume buyers purchasing Q355 S355 square hollow structural section in full-container quantities receive tiered discounts reviewed every six months. Our in-house理化 laboratory tests every heat number before release, ensuring the mill test certificate matches the physical material in the container. With 2,800+ specifications in ready stock across square, rectangular, round, and section profiles, consolidated container loading lets buyers combine multiple product categories into single shipments, reducing per-unit freight cost. CE certification under EN 10210/10219 and ISO 9001:2015 quality management satisfy international compliance requirements, while SGS/BV third-party inspection provides independent verification for risk-averse project owners. Custom non-standard sizes and flexible MOQ from 1-ton trial orders to full-container bulk accommodate both new customer evaluation and established volume procurement. Professional export documentation handling — including packing lists, bills of lading, certificates of origin, and customs classification — prevents port delays that plague buyers managing their own paperwork.
Documentation & Compliance
- Mill test certificate documenting Q355/S355 chemical composition and mechanical properties per GB/T 3091 or EN 10219, traceable to heat number
- CE certificate confirming EN 10210/EN 10219 compliance for European market customs clearance
- ISO 9001:2015 quality management system certificate covering production and inspection processes
- SGS or BV third-party inspection report available upon request for independent material verification
- Material traceability documentation linking each bundle to specific heat number and production batch
- Complete customs documentation package including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q355/S355 square tubes bundled with steel strips and edge protectors to prevent coating damage during ocean transit
- Galvanized surface treatment preserved through waterproof wrapping and separated stacking to avoid zinc abrasion
- Container loading optimized for 5.8 m and 6 m lengths to maximize payload per 20ft or 40ft container
- Random or fixed-length cutting at 11.8 m / 12 m accommodates standard container interior dimensions
- Heat number and steel grade stenciled on each bundle for site identification and traceability verification
- FOB, CIF, and DDP shipping terms available with professional export team handling port coordination and documentation
Getting Your SHS Procurement Started
Submit your Q355 S355 square hollow structural section requirements — including section dimensions, wall thickness, steel grade, total quantity, and destination port — and receive a detailed quotation with mill test certificate confirmation within 12 hours. Non-standard sizes, custom lengths, and specific surface treatment requirements receive engineering review for feasibility and lead time. Certification and documentation needs are confirmed before production begins to prevent customs or inspection complications at destination.
Request Q355 S355 SHS Quotation with Mill Test Certificate
Send your specifications via email to admin@sdxinjiyuan.com or contact directly at +86 188 5315 7756 (WhatsApp/WeChat available) for factory-direct pricing and delivery confirmation.
Frequently Asked Questions
Q: How do Q355 and S355 steel grades compare for structural applications?
A: Q355 follows the Chinese GB standard system while S355 follows European EN standards. Both grades offer similar yield strength levels suitable for primary structural members. The choice depends on project specification requirements and local code compliance — Q355 for projects following Chinese standards, S355 for EN 10219 or ASTM A500 equivalence.
Q: What documentation is included with each shipment?
A: Every batch of Q355 S355 square hollow structural section ships with original mill test certificates showing chemical composition and mechanical properties, traceable to the specific heat number. CE certificates for EN 10210/10219 compliance, ISO 9001 quality certificates, and complete customs documentation are standard. SGS or BV third-party inspection reports are available upon request.
Q: Can I order non-standard sizes or custom lengths?
A: Yes. Beyond the standard 19×19 mm to 800×800 mm range and 5.8 m / 6 m / 11.8 m / 12 m lengths, we accommodate custom non-standard dimensions and random-length cutting. MOQ flexibility ranges from 1-ton trial orders for new customer evaluation to full-container bulk quantities for established volume buyers.
Q: What surface treatment options are available and how do I choose?
A: Four options are available: black painting for indoor dry environments, hot-dip galvanizing for outdoor or corrosive exposure, varnishing for temporary transit protection, or bare for projects applying their own coating system. Hot-dip galvanizing provides the longest corrosion protection but at higher cost; black painting suits interior structural applications where appearance and moderate protection are sufficient.
Q: How is container loading optimized for different lengths?
A: Our export team calculates optimal container loading based on your specific length requirements — 5.8 m and 6 m lengths maximize payload in 20ft containers, while 11.8 m and 12 m lengths fit 40ft containers with minimal waste. Consolidated loading across multiple product types (square tubes, rectangular tubes, beams, plates) reduces per-unit freight cost for multi-category procurement.
