Description
Factory-Direct ERW Welded Square Steel Tube — Every Q235 and S355JR section rolls off our own ERW lines in Jinan, shipped with original mill certificates and no trading markup.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 / S355JR ERW Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube (ERW) |
| Steel Grade | Q195, Q235, Q345, S235JR, S275JR, S355JR |
| Standard | ASTM |
| Section Shape | Square |
| Wall Thickness | 0.9 mm (full range available on request) |
| Length | 6 m / 6.4 m / 12 m |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Non-oiled |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Fluid Pipe, Boiler Pipe, Drill Pipe, Hydraulic Pipe, Gas Pipe, Oil Pipe, Chemical Fertilizer Pipe, Structure Pipe |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frames, column supports, scaffolding structures, warehouse purlins |
| Machinery Manufacturing | Equipment bases, conveyor frames, crane boom sections, machine guards |
| Industrial Piping | Fluid transfer lines, hydraulic circuits, gas distribution networks, chemical fertilizer pipelines |
| Energy & Petrochemical | Boiler support structures, drill pipe casings, oil and gas platform handrails |
What Weld Seam Integrity Costs When a Container Gets Rejected at Destination
A single cold lap in the ERW seam can void an entire shipment — regardless of how clean the outer surface looks.
Global buyers sourcing welded square tubes from fragmented suppliers routinely face quality uncertainty: inconsistent material properties, unclear steel grade traceability, and no independent lab verification before loading. Certification gaps compound the problem — missing or incomplete CE, ISO, or mill test certificates trigger customs delays and project compliance failures at the port of discharge. When an ERW welded square steel tube supplier cannot prove weld seam integrity through ultrasonic testing and caliper-checked wall thickness on every piece, the buyer absorbs the full cost of rejection, re-shipment, and project delay. [NEED_CITE: ERW weld seam inspection standards for cold-formed hollow sections]
Matching Q235 and S355JR Sections to Structural Frame Requirements
Square ERW tubes in Q235 and S355JR grades serve load-bearing frames where dimensional consistency directly affects connection fit-up and welding alignment. The ±1% tolerance on this ERW welded square steel tube ensures that column-to-beam joints meet fabrication drawings without on-site grinding or shimming. Hot rolled, non-oiled surface condition accepts galvanizing or painting directly, eliminating the stripping step that galvanized or oiled finishes would require before coating.
Engineering Compliance Across ASTM, EN, and Project Specifications
Structural applications demand compliance with recognized engineering frameworks — ASTM for North American projects, EN 10219 for European cold-formed hollow sections, and local certification such as SONCAP or SASO for African and Middle Eastern imports. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerances] Steel grade selection between Q235, Q345, S235JR, and S355JR must align with the structural engineer’s load calculations and the importing country’s customs requirements. Fixed lengths of 6 m, 6.4 m, and 12 m reduce on-site cutting waste, while plain ends allow field welding or mechanical coupling without end-preparation delays.
Understanding ERW Welding, Steel Grade Systems, and Surface Condition
ERW (Electric Resistance Welded) square tubes form by passing hot-rolled coil through forming rolls and welding the seam through electrical resistance — no filler metal, no flux. This process suits structural and low-to-medium pressure applications where cost efficiency and dimensional accuracy matter more than the extreme pressure ratings of seamless pipe. The Q-series (Q195, Q235, Q345) follows Chinese GB standards with yield strength designations; the S-series (S235JR, S275JR, S355JR) follows European EN standards with guaranteed minimum yield values and impact energy at specified temperatures. [NEED_CITE: steel grade equivalence between Chinese GB, European EN, and ASTM standards] Hot rolled, non-oiled finish preserves the mill scale that protects during storage while remaining receptive to downstream galvanizing, painting, or powder coating. Wall thickness at 0.9 mm with ±1% tolerance means the actual section modulus stays within predictable bounds for structural calculation — a critical factor when theoretical weight drives freight cost and load-bearing design.
The Hidden Price of Unverified Wall Thickness and Missing Certificates
Accepting an ERW welded square steel tube without mill test certificate traceability or third-party inspection exposes the project to cascading costs: structural elements that fail load testing during acceptance, customs authorities holding containers for missing CE or ASTM documentation, and weld seams with subsurface defects that propagate under cyclic loading. [NEED_CITE: consequences of non-compliant structural steel in international construction projects] Negative tolerance abuse — where actual wall thickness falls below the specified minimum — reduces load capacity while inflating the apparent tonnage delivered. The cost of re-procurement, project delay, and potential structural remediation far exceeds the initial price difference between verified and unverified supply.
Why Project Buyers Source This ERW Welded Square Steel Tube From Shandong Xin Jiyuan
Our Jinan facility runs three dedicated ERW production lines with monthly capacity exceeding 20,000 tons, covering over 2,800 specifications across square, rectangular, round, and section steel categories. Every weld seam undergoes ultrasonic inspection; every tube is caliper-checked before loading — a practice established after an early export batch failed SGS audit for subsurface cold laps and wall thickness deviation. Factory-direct pricing eliminates trading margins, with volume discount programs reviewed every six months for long-term partners. ISO 9001:2015, Lloyd’s CE (EN 10210/EN 10219), and FPC certifications support EU and international customs clearance. Our professional export team handles documentation, container loading optimization, and real-time shipment tracking, consolidating multi-product orders into single-container shipments to reduce freight cost per ton.
Documentation & Compliance
- Mill test certificate documenting Q235 and S355JR chemical composition and mechanical properties per ASTM, with heat number traceability to the original coil
- CE certificate covering EN 10210 and EN 10219 for European structural hollow section compliance and customs clearance
- ISO 9001:2015 quality management certificate covering the full ERW welding square steel tube production process
- SGS or BV third-party inspection report available on request, covering dimensional check, weld seam ultrasonic testing, and mechanical property verification before container sealing
- Material traceability by heat number stamped on each bundle, linking every tube back to coil chemistry and rolling records
- Complete customs documentation package including packing list, bill of lading, and certificate of origin for destination port clearance
Packaging, Loading & Delivery
- Hot rolled ERW welded square steel tubes bundled with steel strips and edge protectors to preserve the non-oiled mill scale surface during ocean transit
- 6 m, 6.4 m, and 12 m lengths loaded with optimized container stowage plans to maximize payload per 20ft and 40ft containers, reducing freight cost per ton
- Heat number and steel grade (Q235 / S355JR) marked on each bundle tag for site identification and traceability verification upon arrival
- Custom cutting to project-specific lengths available before shipment, minimizing on-site waste and cutting labor at destination
- FOB, CIF, and DDP terms supported with professional export documentation and real-time shipment tracking from Jinan inland depot to discharge port
Starting Your ERW Welded Square Steel Tube Procurement
Submit your specification sheet — including section size, wall thickness, steel grade, total tonnage, and destination port — to receive a competitive bulk quotation with volume discount structure, production lead time, and mill test certificate commitment. Non-standard dimensions, custom lengths, and consolidated multi-product container loading are available for project buyers requiring full-category steel supply from a single source.
Request Your Bulk Quotation and Mill Test Certificate
Send your specification requirements via email to admin@sdxinjiyuan.com or contact our export team directly at +86 188 5315 7756 (WhatsApp / WeChat) to confirm pricing, certification, and delivery schedule for your next ERW welded square steel tube order.
Frequently Asked Questions
Q: How do Q235 and Q345 map to S235JR and S355JR for international project specifications?
A: Q235 corresponds roughly to S235JR in yield strength class, while Q345 aligns with S355JR. Both series meet structural requirements for building frames and machinery, with the S-series providing guaranteed impact energy values at specified sub-zero temperatures for cold-climate projects. Mill test certificates from our facility document compliance with the specific standard you require — ASTM, EN, or GB.
Q: What documentation accompanies each shipment of ERW welded square steel tubes?
A: Every batch ships with original mill test certificates showing chemical composition and mechanical properties, traceable by heat number to the source coil. CE (EN 10210/10219), ISO 9001, and FPC certificates support EU and international customs clearance. SGS or BV third-party inspection is available on request before container sealing.
Q: Can I order non-standard dimensions with a 1-ton trial quantity?
A: Yes. Our flexible MOQ starts at 1 ton for trial orders, with full-container bulk pricing available for recurring procurement. Custom wall thickness, length, and section sizes are produced on our three ERW lines with typical lead times of 15–25 days for non-standard specifications.
Q: What surface treatment options are available beyond hot rolled non-oiled?
A: Hot rolled non-oiled finish is standard for this product, suitable for downstream galvanizing, painting, or powder coating. Galvanized and 3PE coating options are available for corrosion-prone environments — contact our team with your project environment details to confirm the appropriate surface treatment for your application.
Q: How do you ensure customs clearance for EU, African, and Middle Eastern imports?
A: Our CE certification under EN 10210 and EN 10219 covers European structural hollow section requirements. For African and Middle Eastern destinations, we provide SONCAP, SASO, and certificate of origin documentation as required. Our export team handles complete customs documentation and coordinates with freight forwarders for smooth port clearance.
