Description
Direct Mill Supply, No Trading Markup — ASTM A572 Gr 50 seamless square hollow sections produced and fabricated under one roof, with heat-level traceability from billet to finished section.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | ASTM A572 Gr 50 Seamless Square Hollow Section |
| Product Type | Seamless Square and Rectangular Steel Tube / Hollow Section |
| Steel Grade | A572 Gr 50, Q355, Q195, Q235, Q345, S235JR, S275JR, S355JR, A500 |
| Standard | ASTM A572, ASTM A500, ASTM A213, DIN EN 10217-1, GB/T 6728 |
| Section Shape | Square / Rectangular |
| Size Range | 15×15 mm – 500×500 mm (Square) / 20×30 mm – 800×1200 mm (Rectangular) |
| Wall Thickness | 0.5 mm – 12 mm |
| Length | 5.8 m – 12 m (or customized) |
| Technique | Seamless / Cold Drawn |
| Surface Treatment | Black, Galvanized (40–500 g/m² or customized), Painted, Oiled |
| Tolerance | ±1% – ±5% |
| Ends | Plain |
| Application | Steel structures, Construction frames, Machinery, Scaffolding, Fluid transport, Hydraulic systems, Industrial platforms |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| EPC & Industrial Construction | Structural frames for warehouses, factory buildings, and process platforms |
| Machinery & Equipment | Hydraulic cylinder barrels, crane boom sections, conveyor support structures |
| Commercial Construction | Scaffolding uprights, mezzanine beams, column casings |
| Infrastructure | Bridge handrail posts, signage gantry frames, utility support structures |
What Dimensional Tolerance Actually Costs on a Seamless Hollow Section Order
Tight tolerance on seamless square hollow sections is not a luxury — it determines whether your steel arrives on-site ready to weld or ready to rework.
When overseas buyers source an ASTM A572 Gr 50 seamless square hollow section from fragmented suppliers, the wall thickness variance between pieces in the same bundle can exceed acceptable limits. I have seen third-party inspectors reject entire shipments at the port because the OD-to-wall ratio drifted beyond the tolerance band allowed by ASTM A500. The cost of re-rolling and re-shipping falls on the buyer when the mill test certificate does not match the physical product. With our vertically integrated production line, every ASTM A572 Gr 50 seamless square hollow section is drawn from billets we control, so the tolerance stays within ±1% – ±5% across the full order — not just on the samples sent to the lab. [NEED_CITE: ASTM A500 dimensional tolerance requirements for cold-formed and seamless hollow structural sections]
How Seamless Cold-Drawn Sections Match Structural Frame Demands
Seamless and cold-drawn hollow sections carry load more predictably than welded alternatives because there is no weld seam to act as a stress concentration point. For EPC contractors building industrial frames under ASTM A572 Gr 50 specifications, this means the column and beam connections perform as the structural engineer calculated — without derating factors for weld quality. Our cold-drawn process produces superior surface finish and tighter dimensional accuracy, which matters when sections must slot into pre-fabricated connection plates on-site. The ASTM A572 Gr 50 seamless square hollow section we supply fits directly into structural designs calling for high-strength, low-alloy steel with improved atmospheric corrosion resistance.
Engineering Compliance and Certification Pathways
Structural frames designed to AISC or EN 1993 standards require material that conforms to recognized specifications — ASTM A572 Gr 50 for North American projects, S355JR or Q355 for European and Chinese-spec work. The seamless cold-drawn manufacturing route meets the dimensional and surface quality requirements of DIN EN 10217-1, while the steel chemistry and mechanical properties satisfy ASTM A572. For projects in corrosive environments, we offer hot-dip galvanizing at 40–500 g/m² coating weight, or painted and oiled finishes for indoor or temporary exposure conditions. Third-party inspection through SGS, BV, or TÜV is available at every production stage, and all material is traceable by heat number back to the original billet cast. [NEED_CITE: ASTM A572 grade equivalence with EN and GB structural steel standards]
Steel Grade Selection and Cold-Drawn Process Fundamentals
ASTM A572 Gr 50 is a high-strength, low-alloy columbium-vanadium steel that delivers higher yield strength than standard carbon grades like A36 or Q235, allowing engineers to reduce section weight while maintaining structural capacity. In the ASTM system, Gr 50 indicates a minimum yield strength of 50 ksi; in the EN system, S355JR serves a similar structural role at 355 MPa yield. Our Q355 grade follows the Chinese GB/T 1591 standard and is widely accepted on Belt & Road infrastructure projects. The seamless cold-drawn process starts from a solid billet pierced and drawn through a die — eliminating the longitudinal weld seam found in ERW tube and producing uniform wall thickness around the entire perimeter. This matters for hydraulic applications and high-pressure fluid transport where weld integrity is a failure risk. Surface treatment choice depends on the service environment: black (mill scale) for indoor structural use, hot-dip galvanized for outdoor or coastal exposure, and oiled for temporary corrosion protection during transit and storage.
Hidden Costs of Sourcing the Wrong Grade or Unverified Material
Ordering ASTM A572 Gr 50 but receiving material that only meets A36 chemistry means the structure will not perform as designed — and the deficiency may not surface until the building inspector requests mill test certificates at final handover. Material without proper heat-number traceability cannot be verified against the original test reports, creating liability exposure for the general contractor. Negative tolerance abuse — where wall thickness consistently falls below the nominal value — reduces load capacity and may violate the minimum thickness requirements in AISC 360 or EN 10210. [NEED_CITE: consequences of material substitution in structural steel construction projects]
Why Project Teams Source ASTM A572 Gr 50 Seamless Square Hollow Section From Us
We operate our own steel production facility with three rolling lines and stock over 2,800 specifications of raw material, so when you order an ASTM A572 Gr 50 seamless square hollow section, the billet-to-finished-section chain never leaves our control. Our in-house metallurgical lab issues mill test certificates documenting chemical composition and mechanical properties for every heat, and we welcome SGS, BV, or TÜV inspection at any stage. The integration of raw material production and fabrication means we can supply both the hollow sections and the cut, drilled, welded, and painted structural components from a single purchase order — one quality system, one point of accountability. We hold ISO 9001 certification, our welding procedures are qualified to AWS and EN standards, and we have delivered structural steel packages to projects across the EU, Middle East, Southeast Asia, and Africa. Custom non-standard sizes and cut-to-length service are available against engineering drawings.
Documentation & Compliance
- Mill test certificate (EN 10204 3.1/3.2) documenting A572 Gr 50 chemical composition and mechanical properties per ASTM A572, traceable by heat number
- CE marking documentation for EN 10219 cold-formed hollow sections where applicable to project specification
- ISO 9001 quality management system certificate covering the full production and inspection process
- SGS, BV, or TÜV third-party inspection report available at pre-shipment or during production stage
- Material traceability report linking each bundle to its original heat number, billet cast date, and test results
- Full export documentation package: commercial invoice, packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Seamless square hollow sections bundled with high-tensile steel strips and edge protectors to prevent surface damage during ocean transit
- Galvanized ASTM A572 Gr 50 sections wrapped with waterproof paper and plastic film to preserve the zinc coating from moisture condensation in container shipping
- Container loading optimized for 5.8 m and 12 m lengths with nested stacking for square sections up to 200×200 mm, maximizing payload per 20ft and 40ft containers
- Custom cut-to-length service available for sections ordered in 5.8 m – 12 m range, with deburred and beveled ends per drawing requirements
- Each bundle marked with heat number, steel grade (A572 Gr 50), size, and length for on-site identification and traceability
- FOB, CIF, and DDP shipping terms available with professional oversized cargo loading plans for sections exceeding standard container dimensions
Ready to Move Forward on Your Hollow Section Procurement
Send your project drawings (PDF or DWG), required steel grade, size schedule, quantity, and destination port — we respond within 24 hours with a detailed quotation including material cost, fabrication scope, coating, packing, and shipping. Our engineering team will review your shop drawings, confirm ASTM A572 Gr 50 availability in your required sizes, and provide a production schedule with milestone inspection points.
Get Your ASTM A572 Gr 50 Seamless Square Hollow Section Quote
Submit your specifications and receive a detailed quotation with mill test certificate samples within 24 hours.
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
Frequently Asked Questions
Q: What is the difference between ASTM A572 Gr 50, S355JR, and Q355?
A: These three grades serve similar structural roles in different standard systems. ASTM A572 Gr 50 follows the US ASTM specification with a minimum yield of 50 ksi. S355JR conforms to the European EN 10025 standard at 355 MPa yield. Q355 follows the Chinese GB/T 1591 standard. All three are high-strength, low-alloy structural grades. We supply all three and can provide grade equivalence documentation for your project’s engineering team.
Q: How can I verify the material authenticity of the seamless hollow sections I receive?
A: Every bundle we ship includes a mill test certificate (EN 10204 3.1 or 3.2) documenting the chemical composition and mechanical properties for that specific heat number. The heat number is marked on each bundle and can be traced back to the original billet cast record. We also welcome third-party inspection by SGS, BV, or TÜV at our facility before shipment, so you can confirm the product matches the documentation independently.
Q: What is the difference between hot-dip galvanized and cold galvanized (electroplated) coating?
A: Hot-dip galvanizing immerses the steel section in molten zinc, producing a metallurgically bonded coating typically at 40–500 g/m² that provides long-term corrosion protection suitable for outdoor and coastal environments. Cold galvanizing (electroplating) applies a thinner zinc layer through electrochemical deposition, which is more economical but offers shorter service life. For structural steel exposed to weather, hot-dip galvanizing is the standard choice.
Q: Can you produce non-standard sizes or cut-to-length sections for my project?
A: Yes. We stock over 2,800 specifications and can produce custom sizes within our range of 15×15 mm to 500×500 mm (square) and 20×30 mm to 800×1200 mm (rectangular), with wall thickness from 0.5 mm to 12 mm. Cut-to-length, drilling, welding, and surface treatment services are available against your engineering drawings. The minimum order quantity is 1 Ton.
Q: What is the typical production lead time and how do you handle export packing for large sections?
A: Standard sizes in stock can ship within typical production lead times after contract and deposit. Custom or non-standard sizes require additional production scheduling based on order volume. For export, we use seaworthy bundling with steel strips and edge protectors. Sections exceeding container dimensions receive professional oversized cargo loading plans with detailed lashing and bracing to prevent transit damage.
