Description
Factory-Direct ERW Tube Supply — Q235 welded square and rectangular steel tubes produced on 3 dedicated lines with in-house lab testing before every shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235 ERW Welded Square/Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, ASTM, S235, SS400 |
| Standard | ASTM, API, JIS, CE (EN 10219/10210 referenced) |
| Section Shape | Square / Rectangular / Round |
| Size Range | 20×20 – 200×200 mm |
| Wall Thickness | 1.5 – 30 mm |
| Length | 1 – 12 m (6 m / 6.4 m / 12 m standard, customizable) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Black / Galvanized Coated / Slightly Oiled |
| Tolerance | ±5% |
| Ends | Plain |
| Application | Structure Pipe, Construction, Bridge, Fluid Pipe, Gas Pipe, Hydraulic Pipe, Machinery, Electrical Installation |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Building | Structural frames, column supports, roof trusses, scaffolding uprights |
| Steel Structure Fabrication | Welded beam-to-column connections, portal frame bracing, purlin systems |
| Infrastructure & Bridge | Pedestrian bridge railings, drainage culvert frames, signage gantry posts |
| Machinery Manufacturing | Conveyor support frames, equipment bases, hydraulic cylinder housings |
| Electrical & Mining | Cable tray supports, mining ventilation duct frames, substation equipment racks |
Why Dimensional Tolerance on ERW Square Tubes Determines On-Site Weld Fit-Up
A ±5% tolerance on wall thickness sounds acceptable on paper, but stacked square tubes with inconsistent walls create cumulative misalignment that forces rework before any welding begins.
Procurement teams ordering ASTM Q235 ERW welded square rectangular steel tube batches for structural frames routinely discover that tubes from different heats arrive with wall variations beyond the stated tolerance range. The result is that beam-to-column connections do not sit flush, gusset plates require shimming, and welders spend hours correcting gaps that should have been zero. On a recent facade project, a batch of 200×200 mm tubes with uneven walls caused the entire curtain wall sub-frame to twist by 3 mm over a 6-meter span — enough to reject glass panel mounting brackets. The root cause was never the design; it was the mill’s tolerance control. [NEED_CITE: EN 10219 dimensional tolerance requirements for cold-formed structural hollow sections]
Matching Q235 ERW Tubes to Structural Load Paths and Connection Details
The Q235 grade sits at the entry point of structural carbon steel, offering adequate yield strength for non-primary frames, bracing members, and secondary support systems. When engineers specify ASTM Q235 ERW welded square rectangular steel tube for conveyor supports or electrical installation racks, the ERW seam runs along one flat face — meaning connection plates welded to that face must account for the weld bead profile. For galvanized-coated tubes used in outdoor mining ventilation frames, the zinc layer protects the ERW seam from corrosion, but field cutting exposes bare steel that requires cold-galvanizing compound before bolting. Our 3 production lines cover the full 20×20 to 200×200 mm range in a single order, so a contractor framing a pedestrian bridge can source both 50×50 mm handrail posts and 200×100 mm main beams from the same heat lot, ensuring consistent chemistry and mechanical behavior across the structure.
Engineering Compliance: Load Codes, Corrosion Protection, and Certification Pathways
Structural frames designed under EN 1993 or AISC 360 require traceable mill test certificates showing chemical composition and mechanical properties per heat number. Q235 tubes exported to the EU must carry CE marking under EN 10219 for cold-formed welded structural hollow sections, while North American projects typically reference ASTM A500 Gr.B equivalence. [NEED_CITE: steel grade equivalence mapping between GB Q235 and ASTM A500 / EN S235JR] Corrosion environment dictates surface treatment: hot-rolled black finish suits indoor machinery bases where paint will be applied on-site; galvanized coating is mandatory for outdoor bridge railings and mining structures exposed to moisture; slightly oiled black tubes serve as interim protection during ocean transit before final coating at destination. Wall thickness selection directly affects load-bearing capacity — a 200×200×8 mm tube carries significantly more axial load than the same outer dimension at 5 mm, but the weight and cost difference must be justified by structural calculation, not guesswork.
Understanding Q235, ERW Process, and Surface Treatment Selection
Q235 belongs to the Chinese GB/T 700 carbon structural steel series, with yield strength positioning it between Q195 (light gauge, non-structural) and Q345 (higher strength, primary structural members). In international equivalence, Q235 maps closely to S235JR under EN 10025 and ASTM A283 Gr.C, though exact chemical limits vary by standard — procurement teams must confirm equivalence with the project engineer before substitution. The ERW (Electric Resistance Welded) process forms the tube by rolling a flat steel strip into a square or rectangular profile and fusing the seam through electrical resistance heating without filler metal. This produces a tight, consistent weld suitable for structural applications up to moderate wall thickness, at lower cost than seamless or SSAW alternatives. Surface treatment choice depends on the service environment: hot-rolled black provides a mill scale layer that accepts primer well; galvanized coating adds 40–80 μm zinc for corrosion resistance in exposed applications; slight oiling prevents white rust during storage and transit but offers no long-term protection. [NEED_CITE: ERW versus seamless steel tube manufacturing process comparison for structural applications]
The Hidden Cost of Ordering ERW Tubes Without Verified Mill Certificates
Purchasing ASTM Q235 ERW welded square rectangular steel tube based on price alone, without requiring EN 10204 3.1 mill test certificates per heat, exposes the project to three failure modes: chemical composition outside the Q235 range (meaning the steel may not weld predictably), wall thickness below the minimum tolerance (reducing load capacity below design assumptions), and missing CE documentation (blocking customs clearance in EU markets). The cost of replacing a rejected container at destination — including demurrage, re-melting, and re-shipping — typically exceeds the original purchase price by a factor of three. [NEED_CITE: consequences of non-compliant steel tube imports on construction project timelines]
Why Project Procurement Teams Source ERW Square Tubes from SD XJY Pipe
Every ASTM Q235 ERW welded square rectangular steel tube leaving our Jinan facility passes through an in-house physical and chemical laboratory that tests dimensional accuracy, tensile strength, and chemical composition before release — no shipment departs without a mill test certificate tied to the specific heat number. Our 3 dedicated ERW lines produce over 2,800 size combinations from 20×20 mm to 200×200 mm with wall thickness up to 30 mm, meaning a single purchase order covering columns, bracing, and purlins ships from one facility with unified documentation. We hold 41 invention patents including China’s original sharp-corner rectangular tube technology, and our full certification package — ISO 9001:2015, Lloyd’s CE under EN 10210/10219, Singapore FPC, and SGS/BV verification — clears customs in over 50 countries without delay. Custom non-standard sizes, cutting to exact project lengths, and professional container loading with anti-damage measures are standard, not premium options.
Documentation & Compliance
- Mill test certificate documenting Q235 chemical composition (C, Mn, Si, S, P limits) and yield/tensile strength per heat number, issued under EN 10204 3.1 format
- CE certificate covering EN 10219 cold-formed welded structural hollow sections, required for EU market customs clearance
- ISO 9001:2015 quality management system certificate covering the full ERW tube production process from raw material receipt to final inspection
- SGS or BV third-party inspection report available upon request, covering dimensional verification, visual weld seam examination, and witness testing
- Material traceability documentation linking each tube bundle to its heat number, production date, and test results
- Export customs documents including packing list, bill of lading, and certificate of origin formatted for destination country requirements
Packaging, Loading & Delivery
- Q235 ERW square and rectangular tubes bundled with galvanized steel strips at intervals matching the 6 m / 12 m standard lengths, preventing bundle separation during crane handling
- Hot-rolled black finish tubes wrapped with waterproof paper and plastic film to prevent mill scale rusting during ocean transit; galvanized tubes bundled with edge protectors to preserve the zinc coating
- Container loading optimized for 20×20 to 200×200 mm size ranges, with nested rectangular profiles maximizing 20ft and 40ft container payload while preventing surface scratching
- Custom cutting to project-specified lengths between 1 m and 12 m, with cut ends deburred and marked with heat number and steel grade for on-site traceability
- Each bundle labeled with steel grade (Q235), size dimensions, wall thickness, heat number, and gross/net weight for customs inspection and site receiving verification
- Shipping terms available as FOB Qingdao, CIF destination port, or DDP door-to-door, with full export documentation and container tracking until arrival
Requesting a Quotation for Your ERW Tube Requirement
Submit your project specifications — including section dimensions, wall thickness, steel grade, surface treatment preference, total tonnage, and destination port — and receive a detailed quotation within 12 hours, complete with mill test certificate samples and third-party inspection options. For non-standard sizes outside the 20×20 to 200×200 mm range, our engineering team provides custom production feasibility assessment and lead time confirmation.
Start Your Q235 ERW Tube Procurement
Send your specification sheet to receive pricing, certification documentation, and production lead time confirmation.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.sdxjypipe.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
Frequently Asked Questions
Q: What is the steel grade equivalence between Q235, S235JR, and ASTM A500?
A: Q235 under GB/T 700 maps closely to S235JR under EN 10025 in terms of yield strength and chemical composition limits. For ASTM equivalence, Q235 aligns with ASTM A283 Gr.C or ASTM A500 Gr.A depending on the specific application requirements. We provide mill test certificates showing actual chemical and mechanical results so your engineer can confirm equivalence before approval.
Q: Can you provide third-party inspection before shipment?
A: Yes, SGS and BV third-party inspections are available for every order. The inspection covers dimensional verification, visual weld seam examination, wall thickness measurement, and witness testing for mechanical properties. Inspection reports are issued before container sealing and included in the export documentation package.
Q: What is the MOQ for custom non-standard sizes?
A: Standard sizes from our 2,800+ specification range ship from stock with a 25-ton MOQ. Custom non-standard sizes outside the 20×20 to 200×200 mm range or wall thickness beyond 1.5–30 mm require production scheduling, with MOQ depending on the specific dimension and tonnage. Contact us with your exact requirements for a custom feasibility assessment.
Q: How do you ensure wall thickness tolerance on ERW tubes?
A: Every production heat undergoes dimensional testing in our in-house physical laboratory, including wall thickness measurement at multiple points around the tube cross-section. Results are documented on the EN 10204 3.1 mill test certificate. The ±5% tolerance stated in our specifications is verified before any shipment leaves the facility.
Q: What surface treatment options are available for Q235 ERW tubes?
A: We offer hot-rolled black finish (as-produced with mill scale), galvanized coating for corrosion protection in exposed environments, and slight oiling for transit protection. Surface treatment selection depends on your project’s service environment and whether final coating will be applied on-site or at destination.
