Description
Factory-Direct ERW Square Tube Supply — S235JR through S355 grades manufactured on our own lines with original mill test certificates for every heat number.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | S235JR / A36 / S355 / SS400 ERW Welded Square Steel Pipe |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | S235JR, A36, S355, SS400, Q235B |
| Standard | ASTM A500, EN 10219, EN 10210, JIS G3466, GB/T 6728 |
| Section Shape | Square |
| Technique | ERW (Electric Resistance Welded) |
| Length | Customized |
| Tolerance | ±1% |
| Surface Treatment | Cold Rolled / Galvanized (optional) |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Oiled or Non-oiled | Non-oiled |
| Invoicing | By Theoretical Weight |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Building & Construction | Factory trusses, stadium roof beams, commercial center columns, greenhouse frames |
| Infrastructure | Bridge structural members, stage trusses, transmission tower frames |
| Machinery Manufacturing | Machine tool frames, conveyor support structures, automation equipment bases |
| Vehicle Manufacturing | Trailer chassis, RV space frames, logistics rack structures |
| Home & Furniture | Stair handrails, security window frames, industrial furniture skeletons |
What Steel Grade Equivalence Costs You on a Multi-Standard Project
Mixing S235JR, A36, and SS400 on one drawing without verified equivalence invites rejection at inspection.
Global project buyers routinely specify EN, ASTM, and JIS grades on the same procurement list. When the mill test certificate shows S235JR chemistry but the engineer asked for A36, customs officers or site inspectors flag the shipment — regardless of whether the mechanical properties actually overlap. [NEED_CITE: steel grade equivalence between EN 10219 and ASTM A500 standards] We have seen full containers held at port because the paperwork could not cross-reference grade tables. A S235JR S355 ERW welded square steel tube supplier who stocks multiple standard designations and prints equivalence notes on the MTC eliminates that bottleneck before the container is sealed.
Matching ERW Square Tubes to Structural Frame Demands
Square ERW tubes in S235JR to S355 grades carry axial and lateral loads in portal frames, mezzanine structures, and equipment skids where bending moments concentrate at the corners. The flat-to-flat geometry gives predictable section modulus in both axes, which matters when a column must resist wind load from any direction. Our production lines run S235JR for general building frames where cost efficiency leads the spec, and step up to S355 when the structural engineer calls for higher yield in long-span trusses or crane-support beams. The S235JR S355 ERW welded square steel tube supplier you choose must hold both grades in rolling schedule — switching mills mid-order changes chemistry batches and breaks traceability.
Compliance Paths for EN, ASTM, and JIS Markets
European projects demand CE marking under EN 10219 for cold-formed welded structural hollow sections, and the factory production control audit must cover the specific steel grade shipped. [NEED_CITE: EN 10219 cold-formed structural hollow sections compliance requirements] North American specifiers write ASTM A500 Grade B or C, and the mill test must report chemistry and tensile results against that standard — not an EN equivalent. Japanese infrastructure tenders reference JIS G3466. Our in-house lab tests every heat against the standard written on the purchase order, and the MTC states the standard explicitly rather than listing “equivalent.” Third-party inspection by SGS or BV is available before loading, which satisfies the most common documentary credit conditions.
Understanding ERW Welding, Grade Selection, and Surface Finish
ERW (Electric Resistance Welded) square tubes are formed from cold-rolled coil, passed through forming rolls into a square profile, and welded along the seam by electrical resistance heat without filler metal. The result is a tight dimensional tolerance — we hold ±1% across the section — and a smooth surface that accepts galvanizing or paint directly. S235JR and Q235B sit at the lower yield range, suited to non-critical structural frames and furniture. S355 delivers roughly 50% more yield strength than S235JR, which lets engineers reduce wall thickness and save weight on long-span members. A36 and SS400 occupy the middle band and remain the default for North American and Japanese projects respectively. [NEED_CITE: steel grade equivalence standards across EN ASTM JIS systems]
For outdoor or corrosive environments, hot-dip galvanizing after welding adds a zinc layer that protects the seam and corners — the areas most vulnerable to moisture trapping. Cold-rolled finish suits indoor applications where appearance and paint adhesion matter. Non-oiled surface is standard for galvanized or painted end-use; oiled surface applies when tubes ship bare and need short-term rust prevention during ocean transit.
Hidden Costs When Grade Documentation Does Not Match the Drawing
Ordering S355 and receiving S235JR with a certificate that says “equivalent” creates three failure modes: the structural engineer rejects the material because the design calculation assumed higher yield; the inspector refuses to sign off because the MTC does not cite EN 10219 for the delivered grade; and the project owner delays payment until a replacement shipment arrives. [NEED_CITE: structural steel compliance and mill test certificate requirements in international procurement] Negative tolerance abuse compounds the problem — a tube that passes the drawing dimension but falls below the minimum wall thickness at the weld seam fails ultrasonic inspection. A S235JR S355 ERW welded square steel tube supplier who invoices by theoretical weight must still guarantee that actual wall thickness meets the standard minimum, not just the order nominal.
Why Project Buyers Source ERW Square Tubes Through Xin Jiyuan
We run three ERW production lines in Jinan, producing over 20,000 tons monthly across square, rectangular, and round sections. Every heat is tested in our own理化 lab before the mill test certificate is issued — chemistry, tensile, and flattening tests are recorded by heat number, and the number is stenciled on every bundle. Our inventory covers 2,800+ specifications in S235JR, A36, S355, SS400, and Q235B, so standard sizes ship from stock while custom lengths and non-standard sections roll in typical production lead times. CE certification under EN 10210 and EN 10219, ISO 9001:2015, and FPC factory audits are current and available for download. For buyers who need cutting, punching, or bending before shipment, our processing line handles it — reducing on-site labor at the destination. We also optimize container loading for mixed-size orders: a 40-foot container can carry square tubes from 20×20 mm to 300×300 mm in nested bundles, and our loading plan maximizes weight without exceeding port limits.
Documentation & Compliance
- Mill test certificate documenting S235JR / S355 / A36 chemical composition and mechanical properties per EN 10219 or ASTM A500 as specified
- CE certificate covering EN 10210 and EN 10219 cold-formed and welded structural hollow sections for EU customs and site acceptance
- ISO 9001:2015 quality management certificate for the full production and inspection process
- SGS or BV third-party inspection report available on request before container sealing
- Full material traceability by heat number stenciled on each bundle, matching the mill test certificate
- Export documentation set including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- ERW welded square tubes bundled with steel strips and padded at contact points to protect the cold-rolled or galvanized surface during ocean transit
- Galvanized square tubes shipped with edge protectors and waterproof wrapping to preserve the zinc coating through humidity and salt-air exposure
- Custom-length cutting available per order, with standard lengths up to 12 meters loaded in 20-foot or 40-foot containers using optimized nesting plans
- Heat number and steel grade stenciled on every bundle for site identification and inspection traceability
- FOB, CIF, and DDP terms available; professional loading supervision at Qingdao port with real-time container tracking
Getting a Firm Quote for Your ERW Square Tube Requirement
Send your specification list — section size, wall thickness, steel grade, total tonnage, and destination port — and we return a bulk price with volume discount tiers, production lead time, and the applicable mill test certificate format within 12 hours. For non-standard sizes or mixed-grade container orders, we provide a consolidated loading plan and weight breakdown before you confirm.
Request Your ERW Square Tube Quotation and Mill Test Certificate
Submit your size list, steel grade, and destination port to receive factory-direct pricing and sample mill test certificates.
WhatsApp / WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
Frequently Asked Questions
Q: What is the difference between S235JR, A36, and SS400, and can they be used interchangeably?
A: S235JR follows EN 10025, A36 follows ASTM A36, and SS400 follows JIS G3101. They share similar carbon ranges but differ in manganese content, impact testing requirements, and minimum yield values. Most engineers treat them as non-interchangeable on paper — the mill test certificate must cite the standard named in the drawing. We supply all three grades and can provide grade equivalence notes for your engineer’s review.
Q: Do you provide mill test certificates, and can third-party inspection be arranged?
A: Yes. Every batch ships with an original mill test certificate showing chemical composition and mechanical properties by heat number. SGS and BV third-party inspections are available on request before loading, and the inspection report is included in the export document set.
Q: What is the minimum order quantity for custom-length ERW square tubes?
A: We accept trial orders from 1 ton for standard stock sizes. Custom lengths and non-standard sections typically require a minimum that fills one production run, and we confirm the exact MOQ after reviewing your size list.
Q: Can you cut, punch, or bend the square tubes before shipping?
A: Yes. Our processing services include cutting to exact length, punching connection holes, and bending for curved frame members. This reduces on-site fabrication work and speeds up installation at the project location.
Q: How do you handle negative tolerance and weight invoicing?
A: We invoice by theoretical weight based on the nominal dimensions and standard density. Our production tolerance is ±1%, and we guarantee that actual wall thickness meets the minimum required by the applicable standard — not just the order nominal. The mill test certificate confirms the measured dimensions for each heat.
Get Factory-Direct Pricing on S235JR–S355 ERW Square Tubes
Share your specification sheet and destination port, and our team will return a detailed quotation with mill test certificate samples and container loading plans.
WhatsApp / WeChat: +86 188 5315 7756
Email: admin@sdxinjiyuan.com
