Description
Factory-Direct Q345B ERW Welded Square Steel Tube — Produced on our own cold-forming lines in Jinan with in-house dimensional and chemical testing, eliminating trading markups on every metric ton shipped.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q345B ERW Welded Square Steel Tube |
| Product Type | Welded Square Steel Tube |
| Steel Grade | Q345B, S235JR, S355, SS400, Q235B, A36 |
| Standard | ASTM A500, EN10219, EN10210, JIS G3466, GB/T 6728, BS, AISI, DIN |
| Section Shape | Square |
| Side Length | 110×110mm (2×2 inch) |
| Wall Thickness | 2mm (customizable) |
| Length | Custom length (standard 6m/12m or per requirement) |
| Technique | ERW (Electric Resistance Welding) |
| Surface Treatment | Cold Rolled |
| Tolerance | ±1% |
| Oiled or Non-oiled | Non-oiled |
| Processing Service | Welding, Punching, Cutting, Bending, Decoiling |
| Invoicing | By Theoretical Weight |
| Application | Steel structures / Construction frames / Machinery manufacturing / Furniture frames / Infrastructure construction / Vehicle manufacturing |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Steel Structures & Construction | Building column frames, roof trusses, portal frames for warehouses and commercial centers |
| Machinery Manufacturing | Machine tool bases, conveyor support frameworks, automation equipment skeletons |
| Infrastructure & Vehicle | Bridge auxiliary bracing, trailer chassis members, recreational vehicle structural frames |
| Furniture & Interior | Heavy-duty display racks, industrial shelving uprights, modular furniture frames |
What Negative Wall Tolerance Actually Costs on a 110×110 Structural Frame
A 0.5mm wall shortfall on a 2mm specified Q345B ERW square tube can reduce section modulus enough to fail structural acceptance under EN 10219 dimensional checks.
Procurement teams ordering Q345B ERW welded square steel tube for load-bearing frames often discover the problem only when the third-party inspector arrives at the yard. The mill cert says 2mm, the caliper reads 1.6mm, and the entire batch is flagged. Reworking the frame design, air-freighting replacements, or renegotiating with the end client costs far more than the original price difference between a reliable supplier and the cheapest offer. Dimensional uncertainty on cold-formed sections also creates fit-up gaps at welded connections, slowing on-site assembly and introducing eccentric loading that the structural engineer never calculated for. [NEED_CITE: EN 10219 cold-formed structural hollow sections dimensional tolerance requirements]
Matching 110×110 Cold-Rolled ERW Sections to Structural Frame Geometry
The 110×110mm square profile with 2mm wall thickness delivers a balanced strength-to-weight ratio for medium-load portal frames and machinery bases where torsional rigidity matters more than raw section area. Cold rolled surface finish on this Q345B ERW welded square steel tube provides tighter dimensional control at the corners compared to hot-rolled alternatives, which directly improves fit-up when tubes are welded into grid frameworks or bolted through pre-punched holes. For machinery manufacturers building conveyor supports or automation equipment skeletons, the ±1% tolerance means repeatable positioning across hundreds of identical frames without shimming. Custom length cutting at our lines reduces on-site welding passes and scrap offcuts at the assembly stage.
Engineering Compliance and Certification Pathways for ERW Square Tubes
Structural frames designed under EN 1993-1-1 require hollow sections conforming to EN 10219 (cold-formed) or EN 10210 (hot-formed), with CE marking mandatory for EU market entry. The Q345B grade specified here meets the chemical and mechanical requirements of S355JR under EN 10219 when produced to the equivalent standard, though project engineers should confirm grade equivalence on the mill test certificate before releasing purchase orders. [NEED_CITE: steel grade equivalence mapping between GB Q345B and EN S355JR] For North American projects calling for ASTM A500 Grade B or C, the same 110×110 ERW profile can be rolled to meet those specifications on separate production runs. Non-oiled cold rolled surface condition suits indoor structural applications and painted finishes; for outdoor or corrosive environments, galvanizing or epoxy coating should be specified as a secondary processing step. Third-party inspection by SGS or BV before shipment provides independent verification of wall thickness, corner dimensions, and weld seam integrity — a requirement increasingly written into EPC contracts for infrastructure and commercial construction. [NEED_CITE: ASTM A500 structural tubing quality requirements]
Understanding Q345B, ERW Welding, and Cold Rolled Finish on Square Hollow Sections
Q345B is a Chinese standard low-alloy high-strength structural steel with higher yield strength than carbon grades like Q235B, making it the default choice for load-bearing frames where weight reduction and section efficiency matter. In international projects, Q345B is typically specified as equivalent to S355JR (EN), ASTM A500 Grade C, or SS400 (JIS), though exact chemical composition and impact testing requirements should be verified against the project specification. ERW (Electric Resistance Welding) forms the square profile from cold-rolled coil through progressive forming rolls and welds the seam by resistance heating without filler metal — a process that delivers consistent wall thickness and smooth internal surfaces at lower cost than seamless alternatives for non-pressure structural applications. The cold rolled surface treatment referenced here means the base coil was cold-reduced before forming, producing a smoother finish and tighter dimensional tolerance than hot-rolled strip, which benefits applications where appearance matters (exposed architectural frames, furniture structures) or where secondary coating adhesion is critical. Wall thickness tolerance of ±1% on this Q345B ERW welded square steel tube ensures that theoretical weight invoicing aligns closely with actual delivered weight, reducing the commercial disputes that arise when negative tolerance pushes beyond acceptable limits.
Hidden Costs of Sourcing ERW Square Tubes Without Verified Mill Documentation
Ordering Q345B ERW welded square steel tube based on price alone, without requiring EN 10204 3.1 mill test certificates or third-party pre-shipment inspection, exposes the project to material substitution risk — receiving Q235B or lower-grade material stamped as Q345B. The consequences are not theoretical: structural frames that pass visual inspection but fail load testing during commissioning, customs holds at EU ports due to missing CE EN 10219 documentation, or welding procedure qualifications invalidated because the actual carbon equivalent differs from the assumed grade. [NEED_CITE: consequences of material misidentification in structural steel procurement] Re-cutting, re-welding, and re-certifying a batch of 110×110 frames after a failed audit costs multiples of the original tube price and delays project handover by weeks.
Why Project Procurement Teams Specify Our ERW Square Tube Lines
Our Jinan production facility operates dedicated cold-forming lines for square and rectangular hollow sections, producing directly from coil without intermediary stockholders — which means the Q345B ERW welded square steel tube you order comes with traceable heat numbers from our in-house physical and chemical laboratory. We hold CE certification under EN 10210 and EN 10219, ISO 9001:2015 registration, and SGS/BV verification, allowing our mill test certificates to clear EU and regulated-market customs without supplementary documentation. The 110×110×2mm profile is one of over 2,800 specifications we produce, and custom lengths beyond standard 6m or 12m are cut to drawing on our processing lines, reducing your on-site labor and material waste. For projects requiring sharp-corner rectangular tubes in architectural facades or glass curtain wall frames, our patented right-angle forming technology (41 invention patents) delivers true 90-degree corners that standard ERW dies cannot achieve. Professional container loading with anti-damage measures prevents the bending and surface scratching that frequently causes rejection at destination ports.
Documentation & Compliance
- Mill Test Certificate (EN 10204 3.1) documenting Q345B chemical composition (C, Mn, Si, P, S) and mechanical properties per GB/T 6728 or equivalent EN 10219 grade mapping
- CE Certificate of Conformity under EN 10219 (cold-formed) and EN 10210 (hot-formed) for EU market structural hollow section compliance
- ISO 9001:2015 Quality Management System certificate covering design, production, and testing of welded square and rectangular steel tubes
- SGS or BV Third-Party Inspection Report verifying wall thickness, corner dimensions, surface quality, and dimensional tolerance before container loading
- Heat Number Traceability linking each bundle of 110×110mm Q345B ERW square tubes to the original coil test report and production batch record
- Export Customs Documentation including packing list, bill of lading, certificate of origin, and commercial invoice aligned with destination country import requirements
Packaging, Loading & Delivery
- Q345B cold rolled ERW square tubes bundled with high-tensile steel strips at intervals preventing bundle separation during ocean transit, with edge protectors preserving the cold rolled surface finish
- Custom length tubes (cut to 5.8m, 6m, 12m, or project-specific dimensions) stacked in uniform layers with timber spacers to prevent contact damage between pieces
- Non-oiled surface condition suitable for indoor storage; for extended outdoor staging at destination, protective wrapping or temporary corrosion inhibitors can be applied per request
- 110×110mm square profile optimized for 20ft and 40ft container loading, with professional loading plans maximizing payload while preventing shifting during transit
- Each bundle tagged with heat number, steel grade (Q345B), size (110×110×2mm), length, and production date for immediate identification at site
- FOB, CIF, and DDP shipping terms available from Qingdao port, with door-to-door logistics coordination to project sites across 50+ export markets
Initiating Your Q345B ERW Square Tube Procurement
Submit your required dimensions (110×110mm or other sizes), wall thickness, steel grade (Q345B/S355JR/A36), total quantity, and destination port to receive a detailed quotation including unit price, production lead time, and applicable certifications. We provide mill test certificates and third-party inspection reports for review before contract signing, and custom length cutting or processing services can be confirmed during the quotation stage.
Request Quotation and Mill Test Certificate for Q345B ERW Welded Square Steel Tube
Send your specifications and quantity to receive pricing, available certifications, and production schedule within 12 hours.
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: How does Q345B compare to S355JR and ASTM A500 Grade C for structural applications?
A: Q345B is a Chinese standard low-alloy high-strength steel with yield strength and chemical composition broadly equivalent to S355JR under EN 10219 and ASTM A500 Grade C. For projects requiring international standard compliance, we produce the same 110×110mm ERW square tube to EN 10219 (S355JR) or ASTM A500 specifications on request, with mill test certificates documenting the applicable standard’s chemical and mechanical requirements.
Q: Can you provide third-party inspection before shipment for EU customs clearance?
A: Yes. We arrange SGS or BV third-party inspection covering dimensional checks (wall thickness, corner dimensions, straightness), visual surface inspection, and review of mill test certificates before container loading. The inspection report is provided to the buyer and supports CE EN 10219/10219 documentation required for EU market structural hollow section imports.
Q: What is the MOQ for custom length cutting on 110×110mm Q345B square tubes?
A: Standard stock lengths (6m, 12m) have no minimum order quantity for container-load purchases. Custom length cutting to project-specific dimensions (e.g., 5.8m, 3.2m, or mixed lengths) is available with typical MOQ of one 20ft container equivalent, depending on the number of different cut lengths required.
Q: Is the cold rolled surface suitable for painting or powder coating?
A: The cold rolled surface finish on Q345B ERW welded square tubes provides excellent adhesion for paint, powder coating, and epoxy systems. The smooth, scale-free surface requires minimal preparation (typically solvent cleaning and light abrasive blasting if needed) compared to hot-rolled mill scale, reducing surface treatment cost and improving coating longevity.
Q: How do you ensure wall thickness tolerance of ±1% on 2mm wall tubes?
A: Our in-house physical laboratory performs dimensional inspection on every production batch using calibrated ultrasonic thickness gauges and mechanical calipers. Wall thickness is verified at four points per tube (each face center and both weld seam areas), with results recorded on the mill test certificate. Tubes falling outside ±1% tolerance are rejected before bundling.
