Q195-Q345 ERW Square Rectangular Hollow Section Steel Tube Supplier

Description

Factory-Direct Black ERW Tubes — 2,800+ specifications in stock with 41 patented technologies including sharp-corner rectangular tube production.

Technical Specifications

Application Suitability

What Negative Tolerance Really Costs on a 20mm Wall Thickness Order

A 0.4mm shortfall on a 3.0mm wall tube can turn a full container into rejected cargo at the destination port.

I watched a Southeast Asian warehouse manager pull out a caliper and measure tube after tube from a container of 40×80 rectangular hollow sections. The purchase order specified 3.0mm wall thickness. The caliper read 2.6mm. The entire shipment was rejected. The re-cutting and replacement cost exceeded the original cargo value. That kind of loss does not come from the steel price — it comes from trusting a supplier who invoices by theoretical weight while delivering well below the tolerance band. When you source a Black ERW Square and Rectangular Hollow Section Steel Tube Supplier who controls production in-house, the ±1% tolerance is verified at three stages: incoming material, in-process welding, and final dimensional check. [NEED_CITE: EN 10219 cold-formed hollow section dimensional tolerance requirements]

Matching Wall Thickness and Steel Grade to Structural Load Paths

A Q235 black ERW square tube at 3mm wall thickness serves adequately as a greenhouse purlin or fence post where wind load governs design. Move that same section into an industrial mezzanine beam carrying point loads, and the engineer will call for Q345 or S355 at 6mm or 8mm wall. The Black ERW Square and Rectangular Hollow Section Steel Tube Supplier must hold both grades in rolling schedule and offer the full 0.8–20mm thickness range without forcing you to split orders across multiple mills. Our three dedicated ERW lines cover square sections from 20×20mm to 400×400mm and rectangular sections from 20×40mm to 300×500mm, meaning a single purchase order for an EPC project can combine light-gauge bracing tubes and heavy-gauge column sections in one shipment.

Engineering Compliance Across EN, ASTM, and JIS Frameworks

Structural hollow sections destined for European projects must carry CE marking under EN 10210 for hot-formed or EN 10219 for cold-formed routes, with factory production control audited by a notified body. North American specifiers typically call for ASTM A500 Grade B or C, while Japanese infrastructure works reference JIS G3466. The Black ERW Square and Rectangular Hollow Section Steel Tube Supplier you select must produce to the correct standard — not merely claim equivalence — because customs authorities in the EU and Singapore require verifiable CE or FPC certificates tied to the heat number on the mill test report. [NEED_CITE: CE marking requirements for structural steel hollow sections under EN 10219] Our mill holds CE certification under both EN 10210 and EN 10219, Singapore FPC approval, and ISO 9001:2015 registration, so documentation travels with the cargo rather than arriving later by email.

How ERW Weld Quality and Steel Grade Selection Intersect

High-frequency electric resistance welding fuses the longitudinal seam without filler metal, producing a weld zone whose metallurgical properties depend on the base steel’s carbon equivalent. Q195 and Q215, with their low carbon content, weld cleanly at high line speeds and suit light structural and fencing applications. Q345 and S355 carry higher manganese and micro-alloying additions that raise yield strength for load-bearing frames but demand tighter control of welding heat input to avoid brittle zones in the heat-affected area. Surface treatment choice follows the service environment: black iron with oil coating works for indoor structural frames where painting will occur on site; pre-galvanized at 30–150g/m² suits covered outdoor structures like greenhouse frames; hot dipped galvanized at 220–260g/m² is specified for exposed fencing posts and coastal infrastructure where corrosion resistance must last decades without maintenance.

The Hidden Price of Unverified Material Certificates

Ordering structural hollow sections without requiring an EN 10204 3.1 mill test certificate means you cannot prove to the project inspector that the Q345 tubes in your steel frame actually meet Q345 chemistry and mechanical properties. The tube may look correct, pass visual inspection, and even bolt together — until the testing laboratory extracts a coupon and finds carbon content outside the standard range or yield strength below the minimum. At that point, the entire batch faces rejection, the steel structure must be dismantled, and the project timeline extends by weeks. [NEED_CITE: EN 10204 inspection document types for steel products] Sourcing from a Black ERW Square and Rectangular Hollow Section Steel Tube Supplier who issues heat-number-traceable certificates and welcomes third-party inspection from SGS, BV, or CCIC eliminates that risk before the container is sealed.

Production Control and Certification Depth Behind Every Shipment

Our in-house physical and chemical laboratory tests every heat of incoming strip steel before it enters the ERW forming line, verifying chemistry against the ordered grade specification. During production, the welding parameters — frequency, pressure, and upset force — are monitored continuously, and finished tubes undergo dimensional checks on diameter, wall thickness, and straightness against the ±1% tolerance. The 41 patented technologies include our proprietary sharp-corner rectangular tube process, which produces tight internal radii that standard roll-forming cannot achieve, allowing fabricators to bolt connections flush without gap-filling shims. With over 2,800 specifications across square, rectangular, and round sections, and the ability to produce non-standard sizes to customer drawing, we consolidate what would otherwise require three or four separate suppliers into a single order managed from one mill.

Documentation & Compliance

• Mill Test Certificate documenting Q235B or S355JR chemical composition and yield strength per EN 10219, traceable to heat number
• CE certificate under EN 10210 and EN 10219 for structural hollow sections, valid for EU and Singapore project customs clearance
• ISO 9001:2015 quality management system certificate covering the full ERW tube production process
• SGS or BV third-party inspection report confirming dimensional tolerance, weld quality, and surface coating thickness
• Material traceability sheet linking each bundle to its heat number, strip coil certificate, and production date
• Customs document package including packing list, bill of lading, and certificate of origin formatted for the destination port

Packaging, Loading & Delivery

• Black ERW square and rectangular tubes bundled with steel strips and edge protectors, preventing surface scratches on the black iron or oiled finish during transit
• Pre-galvanized and hot dipped galvanized hollow sections wrapped with waterproof paper and fitted with rubber spacers to preserve the zinc coating from moisture and mechanical damage
• Container loading plans optimized for 20ft and 40ft containers, nesting smaller square tubes inside larger rectangular sections to maximize payload per shipment for sizes from 20×20mm to 400×400mm
• Cut-to-length service available for 3–12m standard lengths or custom sizes, with saw-cut ends deburred and marked with heat number, steel grade, and dimensional callout
• Shipping terms supported include FOB, CIF, and DDP, with door-to-door logistics coordination to 50+ countries across the EU, North America, Southeast Asia, Middle East, and South America

Start Your Procurement with Verified Specifications

Submit your required section dimensions, wall thickness, steel grade, surface treatment preference, and destination port — we respond within 12 hours with a detailed quotation including unit price, production lead time, applicable certifications, and a sample mill test certificate for your review. For non-standard sizes outside the 20×20mm–400×400mm square or 20×40mm–300×500mm rectangular range, our engineering team provides a custom feasibility assessment and drawing confirmation before production begins.

Request Your Quotation and Mill Test Certificate Today

Send your specification sheet by email or WhatsApp, and receive a complete commercial and technical offer with material documentation within one business day.

Tel: +86 531 8573 6315

Mobile/WhatsApp/WeChat: +86 188 5315 7756

Email: admin@sdxjysteel.com