Description
Direct Mill Supply for ERW Square Tubes — XJY Plate supplies ASTM A500 Gr.B welded square steel tubes in sizes from 19×19mm to 800×800mm with wall thickness up to 30mm, shipped with original mill test certificates and full heat number traceability.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Carbon Steel Welded Square Tube |
| Product Type | Welded Square Steel Tube / Square Hollow Structural Section (SHS) |
| Steel Grade | Gr.B, S235, S275, S355, STK400, Q235 |
| 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 / DRL / SRL / Random Length |
| Technique | ERW (Welded) |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Processing Service | Bending, Cutting |
| Application | Construction structures, building frames, curtain wall systems, support tubes, structural pipe, scaffolding, machinery fabrication |
| MOQ | 5 Tons |
| Origin | China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Steel Fabricators | Structural frames for warehouses, equipment support bases, machinery mounting platforms |
| Construction Companies | High-rise building columns, curtain wall mullions, bridge support members |
| Shipyards & Infrastructure | Offshore platform support legs, scaffolding systems, walkway handrails |
Wall-Thickness Tolerance Decides Whether Your Frame Passes Inspection
A ±1% tolerance on a 30mm wall sounds tight — until a caliper reading at 27mm turns a 50-ton order into a rejected shipment.
I once watched a 50×50 welded square tube shipment get turned away at a Lagos project site because the wall thickness measured 2.5mm against a specified 3.0mm. The监理 rejected the entire container. Negative tolerance practices — where mills push wall thickness to the lower legal limit — create a gap between theoretical weight invoicing and actual structural capacity. When ASTM A500 Gr.B tubes arrive at a job site with walls thinner than declared, engineers cannot verify load-bearing compliance, and the entire procurement cycle restarts. [NEED_CITE: ASTM A500 dimensional tolerance requirements for structural hollow sections]
How ERW Square Tubes Match Structural Engineering Demands
An ASTM A500 welded square steel tube in S355 or Gr.B grade delivers the flat bearing surfaces that bolted and welded connections require in portal frame construction. The ERW process produces a consistent longitudinal weld seam that runs through the full length of each tube, maintaining uniform strength across the cross-section. For curtain wall mullions and scaffold uprights, the square profile eliminates rotational instability that round tubes introduce under eccentric loading. XJY Plate cuts and bends these tubes to project-specific dimensions, reducing on-site welding and waste — a practice we refined supplying structural frames to fabricators across West Africa and East Africa.
Engineering Compliance and Surface Protection Selection
Structural hollow sections used in load-bearing frames must conform to dimensional and mechanical requirements defined by ASTM A500 or EN 10219, depending on the project specification jurisdiction. [NEED_CITE: EN 10219 cold-formed welded structural hollow sections standard scope] For outdoor or marine-adjacent applications, hot-dip galvanizing provides corrosion resistance that black painting cannot match beyond five years of exposure. Bare or varnished finishes suit indoor structural use where appearance and corrosion are not primary concerns. Steel grade selection — S235 for light frames, S355 for heavily loaded columns — directly determines the member size an engineer can specify under AISC or Eurocode 3 design rules. Third-party inspection by SGS or BV verifies both dimensional accuracy and weld seam integrity before shipment.
Understanding Grade Equivalence and ERW Weld Quality
The carbon steel grades listed for this product — Gr.B, S235, S275, S355, STK400, Q235 — span three major international standard systems: ASTM (American), EN (European), and GB/JIS (Chinese and Japanese). ASTM A500 Gr.B roughly corresponds to EN S235JR in yield strength class, while S355 offers significantly higher load capacity for column and beam applications. [NEED_CITE: steel grade equivalence between ASTM A500 and EN 10219 standards] The ERW welding process forms the tube by rolling a flat steel strip into a square profile and welding the seam through high-frequency electric resistance — this produces a clean, narrow weld zone with minimal heat-affected zone distortion. Wall thickness tolerance of ±1% ensures that the actual cross-sectional area stays within the range engineers use for load calculations, preventing the dangerous gap between design assumptions and as-built conditions. Surface treatment selection depends on the service environment: galvanized coatings protect against atmospheric corrosion for 15–25 years, while black paint or varnish serves as a temporary barrier during storage and transport.
Hidden Costs of Procuring Without Verified Tolerances
Ordering welded square tubes based on price alone, without requiring original mill test certificates and independent dimensional inspection, exposes projects to three categories of hidden cost. First, material that fails to meet the specified grade — whether through substitution or forged certificates — cannot pass structural验收, forcing complete replacement at the contractor’s expense. Second, tubes with excessive negative tolerance arrive at port with lower actual weight than invoiced, creating disputes and potential customs discrepancies. Third, inconsistent wall thickness causes fit-up problems during fabrication, delaying welding schedules and increasing labor costs. [NEED_CITE: structural steel procurement quality verification requirements]
Why Project Buyers Source ASTM A500 Welded Square Tubes from XJY Plate
XJY Plate operates as a dedicated flat-product division within Shandong Xin Jiyuan Special Steel Tube Co., Ltd, meaning every welded square tube we supply comes directly from our rolling lines — no trading markup, no middleman inventory shuffling. Our in-house testing lab produces original mill test certificates for every heat, documenting chemical composition and mechanical properties with full traceability back to the steelmaking batch. We maintain ready stock across the full 19×19mm to 800×800mm range in S235 through S355 grades, so project buyers do not wait for mill rolling schedules on standard specifications. Custom cutting to exact project lengths and bending services reduce on-site fabrication time — a capability we developed supplying steel fabricators who need precise member lengths for modular construction. Every shipment includes professional heavy cargo loading with flatbed or open-top container options, and we handle complete export documentation including certificate of origin and customs clearance support for destinations across Southeast Asia, the Middle East, Africa, and South America.
Documentation & Compliance
- Mill test certificate documenting Gr.B / S235 / S275 / S355 chemical composition and mechanical properties per ASTM A500 or EN 10219, with heat number traceability
- ISO 9001:2015 quality management certificate covering the full welded square tube production process
- CE certificate confirming compliance with European structural steel product requirements
- SGS or BV third-party inspection report available upon request, covering dimensional verification and visual weld inspection
- Material traceability report linking each tube to its heat number, chemical analysis, and mechanical test results
- Complete customs documentation including packing list, bill of lading, and certificate of origin for destination-country clearance
Packaging, Loading & Delivery
- Welded square tubes bundled with steel strips and edge protectors, sized to match the 5.8m / 6m / 11.8m / 12m length specifications for optimal container utilization
- Galvanized square tubes packed with separated layers and anti-scratch padding to preserve the zinc coating during ocean transit
- Black painted and varnished tubes wrapped in waterproof paper or shrink film to prevent surface damage from moisture and handling
- Custom cut-to-length tubes grouped by project specification with heat number and steel grade markings stenciled on each piece
- Loading plans optimized for 20ft and 40ft open-top containers, with weight distribution calculated to avoid overweight penalties at destination ports
- FOB, CIF, and DDP shipping terms available, with professional flatbed and break-bulk logistics for project cargo exceeding container capacity
Start Your Procurement with Verified Specifications
Submit your required steel grade, section size, wall thickness, length, and quantity along with your destination port to receive a detailed quotation including material cost, processing fees, and shipping terms. We respond to all inquiries within 12 hours with a complete offer backed by original mill test certificate availability and third-party inspection options.
Request Your ASTM A500 Welded Square Tube Quotation
Send your specifications to receive pricing, mill test certificate samples, and shipping options within 12 hours.
Company: Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjyplate.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjyplate.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
Frequently Asked Questions
Q: How do ASTM A500 Gr.B, EN S235/S275/S355, and GB Q235 compare in terms of grade equivalence?
A: These grades span different international standard systems but share comparable carbon steel compositions. ASTM A500 Gr.B aligns closely with EN S235JR in yield strength classification, while S275 and S355 offer progressively higher yield strength for heavier structural applications. GB Q235 serves as the Chinese national standard equivalent for general structural use. We provide grade conversion guidance and supply the specific grade your project specification requires, with mill test certificates documenting compliance.
Q: Can you provide original mill test certificates with heat number traceability, and is third-party inspection available?
A: Yes. Every shipment includes an original mill test certificate documenting chemical composition and mechanical properties, with heat number traceability back to the steelmaking batch. Third-party inspection by SGS or BV is available upon request to verify dimensional accuracy, surface quality, and weld seam integrity before shipment.
Q: What is the minimum order quantity for cut-to-size square tubes, and can you produce non-standard dimensions?
A: The minimum order quantity is 5 tons. We offer custom cutting to your specified lengths from the standard range of 5.8m, 6m, 11.8m, and 12m, as well as random length options. Bending and blanking services are also available. For non-standard side lengths or wall thicknesses outside the 19×19mm to 800×800mm and 1–30mm ranges, please submit your specifications for feasibility review.
Q: When should I choose hot-dip galvanized versus black painted or bare finish for structural applications?
A: Hot-dip galvanizing is recommended for outdoor, marine-adjacent, or high-humidity environments where long-term corrosion resistance is critical — it provides 15–25 years of protection without maintenance. Black painting suits indoor structural use or applications where the tubes will receive additional coating on-site. Bare or varnished finishes work for temporary exposure during construction or for indoor machinery frames where corrosion is not a primary concern.
Q: How do you handle invoicing — by theoretical weight or actual weighed tonnage?
A: We offer both options depending on your preference and destination country customs requirements. Theoretical weight calculation is based on the specified dimensions and standard steel density, while actual weight is determined by scale measurement before loading. Our ±1% wall thickness tolerance ensures that the difference between theoretical and actual weight remains minimal, reducing invoicing disputes.
