Description
Factory-direct S355 welded square steel tube supply — Every S355 welded square steel tube is produced on dedicated ERW lines and verified by our in-house physical and chemical laboratory before dispatch, eliminating trading company markups and material traceability gaps.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S355 / Gr.B Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (SHS) |
| Steel Grade | Gr.B, S235, S275, S355, 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 | ERW (Welded) |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Curtain wall / Support tubes / Building structures |
| MOQ | 5 Tons |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC Contractors | Industrial plant frameworks, pipe rack supports, equipment platform columns |
| Construction Companies | High-rise building frames, curtain wall mullions, bridge handrail posts |
| Machinery Manufacturers | Conveyor system uprights, crane boom sections, agricultural equipment chassis |
| Infrastructure Developers | Solar mounting structures, sound barrier posts, traffic signal gantries |
What Wall-Thickness Tolerance Actually Costs on a Structural Frame Order
A ±1% tolerance on a 30mm-wall S355 welded square steel tube means the difference between passing structural inspection and triggering a full batch rejection.
Procurement teams ordering S355 welded square steel tube for load-bearing frames often discover that wall-thickness deviation beyond acceptable limits reduces the actual section modulus below design values. When suppliers ship material at the extreme negative edge of tolerance without declaring it, engineers face recalculated load capacities that no longer match the original structural drawings. The result is not just a paperwork dispute — it means on-site rework, delayed handover, and in worst cases, structural reinforcement that was never budgeted. Material traceability gaps compound the problem: without heat-number linkage on every piece, sorting compliant tubes from non-compliant ones becomes a destructive testing exercise. [NEED_CITE: EN 10219 cold-formed welded structural hollow sections dimensional tolerances]
Matching S355 SHS to Structural Frame and Curtain Wall Demands
S355 welded square steel tube in the 100×100mm to 400×400mm range with wall thickness between 6mm and 16mm serves as the primary load-transfer element in portal frame structures and curtain wall support grids. The flat internal surfaces of square hollow sections allow direct bolted or welded connections without gusset plates, reducing joint complexity on site. For curtain wall applications, the ±1% tolerance on S355 welded square steel tube ensures that mullion alignment stays within architectural finish requirements, while the ERW weld seam — positioned along the centerline of each face — provides predictable stress distribution under wind loading.
Structural Compliance and Certification Requirements Across Markets
Engineering specifications for steel structures typically reference EN 1993-1-1 (Eurocode 3) in European markets and AISC 360 in North American projects. S355 welded square steel tube conforming to EN 10219 satisfies the material toughness and weldability requirements of Eurocode 3 for structures in seismic and cold-climate zones. For projects entering the EU, CE marking under EN 10210/EN 10219 is not optional — customs authorities require the Declaration of Performance alongside the mill test certificate, and shipments without these documents face port holds averaging several weeks. [NEED_CITE: CE marking requirements for structural steel hollow sections under EU Construction Products Regulation] ASTM A500 Gr.B equivalence applies for North American tenders, where the same S355 welded square steel tube can be supplied under dual certification if the chemical composition and mechanical properties satisfy both standards. On-site cutting and welding of these tubes follow standard procedures for carbon manganese steels, though pre-heat treatment may be required for wall thickness exceeding 25mm in cold ambient conditions.
Steel Grade Selection and ERW Welding Process Fundamentals
The S-series steel grades — S235, S275, S355 — represent increasing minimum yield strength levels under the EN standard system, where S355 delivers approximately 50% higher yield capacity than S235, making it the default choice for primary structural members in multi-story buildings and industrial frames. The ASTM equivalent Gr.B under A500 occupies a similar mid-range position, while STK400 from the JIS system serves comparable roles in Asian market specifications. ERW (Electric Resistance Welding) forms the square profile from steel coil through progressive roll forming, then fuses the longitudinal seam using high-frequency current — this process produces a consistent weld zone with mechanical properties matching the parent metal when properly controlled. Surface treatment selection depends on the service environment: black painted or varnished finishes suit indoor structural applications where appearance matters but corrosion exposure is limited; galvanized coatings extend service life in outdoor or humid environments; bare tubes are specified when the buyer applies their own coating system on site. Wall thickness tolerance directly affects theoretical weight calculations — a 200×200×8mm S355 welded square steel tube at nominal dimensions weighs differently than one produced at the negative tolerance edge, and procurement documents must specify whether ordering is by theoretical or actual weight.
The Hidden Cost of Accepting Non-Compliant Hollow Sections
Ordering S355 welded square steel tube from suppliers without independent laboratory verification creates a chain of risks that surface only during project inspection. Material certificates fabricated without actual test data show correct grade designations on paper but fail when third-party inspectors conduct spectrochemical analysis or tensile testing at the destination port. The financial exposure extends well beyond the material cost: customs detention generates demurrage charges, project timelines shift as replacement material is sourced, and structural engineers must reassess whether partially installed non-compliant tubes can remain in place. [NEED_CITE: consequences of non-compliant structural steel in construction projects] Negative tolerance abuse — where wall thickness consistently falls below the declared nominal value — reduces load capacity without visible indication, creating latent structural safety concerns that compromise the entire building certification process.
Procurement Confidence Through Factory-Direct Verification
Every S355 welded square steel tube produced in our facility passes through an in-house physical and chemical laboratory that conducts incoming raw material inspection, in-process weld seam verification, and final dimensional and mechanical testing before any piece is approved for loading. This laboratory infrastructure supports the 41 patented technologies we hold, including proprietary sharp-corner rectangular tube manufacturing that extends our capability beyond standard ERW profiles. Our three dedicated production lines cover over 2,800 specifications across square, rectangular, and round sections, allowing single-source procurement that eliminates the coordination overhead of sourcing beams, plates, and tubes from separate suppliers. CE certification under EN 10210/EN 10219 and ISO 9001:2015 registration provide the documentary foundation for EU and international project compliance, while SGS and BV third-party inspection services are available for buyers who require independent verification before shipment. Custom non-standard dimensions, cut-to-length processing, and special packaging arrangements are handled within the same production facility, with professional loading plans optimizing container utilization for the specific size range of each order.
Documentation & Compliance
- Mill test certificate documenting S355 chemical composition (C, Mn, Si, P, S content) and mechanical properties (yield strength, tensile strength, elongation) per EN 10219 or ASTM A500
- CE certificate confirming compliance with EN 10210/EN 10219 for structural hollow sections, required for EU customs clearance and project handover
- ISO 9001:2015 quality management system certificate covering the full production process from coil reception to final inspection of S355 welded square steel tube
- SGS or BV third-party inspection report available upon request, covering dimensional verification, visual weld inspection, and mechanical testing for S355 / Gr.B grades
- Full material traceability by heat number linking each S355 welded square steel tube to its original coil test certificate and production batch record
- Export customs documentation including packing list with piece count and theoretical weight, bill of lading, and certificate of origin for preferential tariff treatment
Packaging, Loading & Delivery
- S355 welded square steel tubes bundled with high-tensile steel strips at regular intervals, with edge protectors preventing surface damage to galvanized or painted finishes during transit
- Galvanized S355 welded square steel tube shipments include waterproof wrapping at bundle ends to prevent white rust formation during ocean freight in humid climates
- Container loading plans optimized for 19×19mm through 400×400mm square tubes in 6m and 12m lengths, maximizing payload within 20ft and 40ft standard shipping containers
- Cut-to-length service available for S355 welded square steel tube ordered in random or specific lengths between 5.8m and 12m, with saw-cut ends deburred and marked
- Each bundle tagged with heat number, steel grade (S355 / Gr.B / S235), size designation, and production date for on-site identification and traceability
- FOB, CIF, and DDP shipping terms available with door-to-door logistics coordination to 50+ countries, including professional lashing and securing for heavy-wall S355 welded square steel tube exceeding 20mm thickness
Securing Your S355 Welded Square Steel Tube Quotation
Submit your project specifications — including section size, wall thickness, steel grade, total tonnage, and destination port — to receive a detailed quotation with production timeline and applicable certification documents. Our technical team reviews each inquiry to confirm standard availability or propose custom non-standard dimensions, and provides mill test certificate samples for your engineering approval before contract execution.
Request Your S355 Welded Square Steel Tube Quote Today
Send your specifications via email to admin@sdxjysteel.com or contact our international sales team at +86 188 5315 7756 (WhatsApp/WeChat available) for pricing, mill test certificate samples, and container loading confirmation.
