Description
Factory-direct ERW square tubes — Produced on 3 in-house lines covering 2,800+ specifications with wall thickness up to 30mm, shipped directly from Jinan mill to your project site.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| 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 / Building structures / Curtain wall framing / Support tubes / Machinery structures |
| MOQ | 5 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & EPC | Column and beam frames for commercial buildings, warehouse portal structures, bridge support piers |
| Facade & Curtain Wall | Vertical mullion supports, horizontal transom framing, architectural exposed square columns |
| Machinery Manufacturing | Conveyor frame structures, crane boom sections, equipment base platforms |
| Infrastructure | Sound barrier posts, solar panel mounting racks, highway sign gantry columns |
What Dimensional Tolerance Actually Costs on a Welded Square Tube Order
A ±1% tolerance on an 800×800mm SHS means up to 8mm deviation per side — enough to misalign curtain wall anchor plates and force on-site reaming.
I once watched a facade contractor in Dubai reject an entire container of 200×200 welded square tubes because the out-of-square exceeded 3mm over a 6m length. The mill had shipped material meeting their own internal standard, but the project specification called for EN 10219 Class C dimensional accuracy. The tubes were structurally sound — yet they sat in Jebel Ali for six weeks before re-inspection and partial rework cleared them. [NEED_CITE: EN 10219 cold-formed welded hollow sections dimensional tolerance classes]
When you source an ASTM A500 welded square steel tube supplier, the real question is not whether the steel passes a tensile test. It is whether the supplier controls corner radius consistency, weld seam flushness, and length straightness to a tolerance your engineer has actually signed off on. Missing that distinction turns a routine procurement into a customs-hold or site-rejection event.
How ERW Welded Square Tubes Match Structural Frame Requirements
An ASTM A500 welded square steel tube in S355 or Gr.B grade serves load-bearing frames where flat interior surfaces and 90-degree corners allow direct plate-to-tube welding without gusset fillers. The ERW process produces a continuous longitudinal weld that, when properly normalized, achieves weld-zone mechanical properties comparable to the parent metal — critical for moment-resisting connections in seismic zones. For curtain wall applications, the tight ±1% tolerance on side length ensures that fabricated frame modules arrive on site within the alignment range of standard anchor bolts, eliminating field drilling.
Engineering Compliance and Surface Protection Selection
Structural frames designed to EN 1993 or AISC 360 require verified yield strength and documented chemical composition — both confirmed through mill test certificates traceable to heat number. [NEED_CITE: steel grade equivalence between ASTM A500 and EN 10219 standards] For outdoor or high-humidity environments, galvanized surface treatment provides corrosion resistance exceeding 50 microns coating thickness, while black painting suits interior dry applications where visual appearance is secondary. ASTM A500 Gr.B remains the default specification for North American projects, while S355 covers European and Middle Eastern structural codes — confirming grade equivalence before ordering prevents customs rejection at destination port.
Steel Grade Selection and ERW Weld Integrity
The five grades offered — Gr.B, S235, S275, S355, STK400 — represent a yield strength progression from approximately 235 MPa to 355 MPa nominal minimum, directly influencing section modulus requirements and member sizing. S235 suffices for non-critical bracing and purlin systems, while S355 is specified for primary columns and transfer girders where higher strength reduces member weight. The ERW welding process forms the tube by cold-rolling flat strip into square profile and passing it through high-frequency induction coils that forge the longitudinal seam under pressure — producing a weld line that, when properly controlled, shows no visible bead on the exterior surface. Wall thickness from 1mm to 30mm covers everything from light-gauge purlin tubes to heavy structural columns, with the ±1% tolerance applying uniformly across this range.
Hidden Costs of Incorrect Grade or Tolerance Procurement
Ordering Gr.B when the structural drawing specifies S355 means the delivered tubes carry insufficient yield strength — the error surfaces only during third-party inspection or, worse, after erection when deflection exceeds serviceability limits. Certification gaps create a separate failure mode: tubes shipped without EN 10219 compliance documentation cannot clear EU customs, regardless of actual material quality. [NEED_CITE: structural steel certification requirements for EU customs clearance] Negative tolerance abuse — where wall thickness consistently falls at the lower boundary — reduces theoretical weight and load capacity simultaneously, a discrepancy invisible until structural calculation review or ultrasonic thickness measurement on site.
Why Project Procurement Teams Source from Shandong Xin Jiyuan
Our Jinan mill operates three dedicated ERW lines producing welded square tubes from 19×19mm to 800×800mm, eliminating the specification gaps that force buyers to split orders across multiple suppliers. Every heat undergoes chemical and mechanical testing in our in-house laboratory before release, with mill test certificates generated directly from verified data — not back-filled from generic templates. We hold Lloyd’s CE certification under EN 10219 and EN 10210, Singapore FPC approval, and ISO 9001:2015 registration, covering the full certification chain required for regulated markets. Our patented sharp-corner rectangular tube technology — holding 41 invention patents — delivers true 90-degree external corners that standard ERW mills cannot achieve, meeting the aesthetic and connection-precision demands of architectural facade projects. Custom non-standard sizes, cut-to-length service, and professional container loading with anti-damage measures complete the procurement cycle from inquiry to site delivery across 50+ countries.
Documentation & Compliance
- Mill test certificate documenting Gr.B / S235 / S355 chemical composition and yield strength per ASTM A500 or EN 10219, traceable to heat number
- CE certificate covering EN 10219 cold-formed welded structural hollow sections and EN 10210 hot-formed sections, issued by Lloyd’s Register
- ISO 9001:2015 quality management system certificate covering full production and inspection process
- SGS or BV third-party inspection report confirming dimensional accuracy, surface treatment thickness, and mechanical test results prior to shipment
- Material traceability report linking each bundle to heat number, production date, and test certificate reference
- Complete customs documentation set including packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- ERW welded square tubes bundled with high-tensile steel strips at minimum four points per bundle, with end caps protecting plain ends during transit
- Galvanized tubes packed with edge protectors and interleaved separators to preserve zinc coating integrity and prevent white rust formation during ocean shipment
- Container loading optimized for 5.8m and 6m lengths in 20ft units, with 11.8m and 12m lengths loaded in 40ft open-top or flat-rack containers using timber cradles to prevent bending
- Cut-to-length service available for random length orders, with kerf loss calculated and charged per actual piece count
- Each bundle labeled with heat number, steel grade (Gr.B / S355 / STK400), size designation, and purchase order reference for site identification
- Shipping terms FOB Qingdao, CIF destination port, or DDP project site available, with full tracking from mill dispatch through customs clearance to final delivery
Requesting Quotation and Technical Documentation
Submit your specification sheet listing side length, wall thickness, steel grade, surface treatment preference, total tonnage, and destination port — we return a detailed quotation within 12 hours including unit pricing, production lead time, and shipping terms. For non-standard sizes outside the 19×19mm to 800×800mm range or wall thickness beyond 30mm, our engineering team provides custom feasibility assessment and tooling timeline. Mill test certificates, CE documentation, and third-party inspection arrangements are confirmed at contract stage, ensuring full compliance before production begins.
Frequently Asked Questions
Q: How do I select between Gr.B, S235, S275, S355, and STK400 for my project?
A: Grade selection depends on your structural design code and load requirements. ASTM A500 Gr.B is standard for North American projects, S235/S275/S355 follow EN 10219 for European specifications, and STK400 aligns with JIS G3466 for Japanese-standard projects. We provide grade equivalence confirmation before production to ensure material matches your engineer’s specification.
Q: Can you provide mill test certificates and arrange third-party inspection?
A: Yes. Every shipment includes mill test certificates documenting chemical composition and mechanical properties per the applicable standard (ASTM A500, ASTM A53, or GB/T 3091). SGS or BV third-party inspection is available upon request, conducted at our facility before shipment to verify dimensional accuracy, surface treatment, and test certificate consistency.
Q: What is the minimum order quantity for custom non-standard sizes?
A: Standard sizes from our 2,800+ specification range carry a 5-ton MOQ. Custom non-standard sizes outside stock range require minimum 20 tons per size to justify mill setup and tooling adjustment. We provide detailed feasibility assessment including tooling cost and production timeline for non-standard inquiries.
Q: How do you ensure dimensional tolerance meets ±1% consistently?
A: Our in-house laboratory performs dimensional inspection on every production heat using calibrated measuring equipment. Side length, wall thickness, straightness, and out-of-square are verified against ASTM A500 or EN 10219 tolerance classes before bundle release. Full inspection reports with photographs are provided prior to shipment for client review.
Q: What surface treatment options are available and how do they affect lead time?
A: We offer black painting, hot-dip galvanized, varnish coating, and bare (oiled) surface treatment. Black painted and bare tubes ship from stock within typical production lead times. Galvanized tubes require additional processing time for zinc coating application and cooling, extending lead time accordingly. Surface treatment selection is confirmed at quotation stage based on your project environment and specification requirements.
Get Your ASTM A500 Welded Square Steel Tube Quotation Today
Send your specification requirements to receive detailed pricing, mill test certificate samples, and production timeline within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
Website: www.sdxjypipe.com
