Description
Factory-Direct ERW Tubes — 2,800+ specifications in stock from our own steel mill
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B ERW Welded Square/Rectangular Steel Tube |
| Product Type | ERW Welded Square / Rectangular Steel Tube |
| Steel Grade | Q195, Q215, Q235, Q345, S235, SS400 |
| Standard | ASTM, API, CE, JIS, ISO 9001, SGS |
| Section Shape | Square / Rectangular / Round |
| Size Range | 20×20 mm – 200×200 mm |
| Wall Thickness | 1.5 – 30 mm |
| Length | 1 – 12 m (standard 6 m / 6.4 m / 12 m; custom available) |
| Technique | ERW (Electric Resistance Welded) |
| Surface Treatment | Hot Rolled / Galvanized Coated / Slightly Oiled |
| Tolerance | ±5% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Machinery / Scaffolding / Furniture / Fluid transport / Gas & oil pipeline / Boiler / Hydraulic systems |
| MOQ | 25 Tons |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Infrastructure | Building frame columns, beam-to-column connections, platform supports, stairway handrails |
| EPC & Industrial Projects | Warehouse portal frames, factory roof trusses, pipe rack structures, equipment support bases |
| Machinery & Scaffolding | Conveyor frame members, scaffolding vertical standards, equipment guard structures |
| Fluid & Energy Systems | Low-pressure fluid transport lines, boiler support frames, hydraulic system manifolds |
What Wall-Thickness Tolerance Costs on a Q235B ERW Square Rectangular Steel Tube Order
A ±5% tolerance window is where procurement risk meets structural reality.
When buyers source a Q235B ERW welded square rectangular steel tube supplier from overseas, the distance between the mill and the job site magnifies every specification gap. Wall thickness drifting beyond tolerance means theoretical weight calculations no longer match actual delivered tonnage — and third-party inspectors at the destination port will flag the discrepancy before the cargo ever reaches the project. I have seen entire shipments held at customs because the mill certificate listed one thickness range while the ultrasonic gauge readings told a different story. The cost is not just the re-inspection fee; it is the crane idle time, the rescheduled erection crew, and the RFI chain that follows [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerance requirements].
Matching Q235B and Q345 Grades to Structural Frame Demands
The Q235B and Q345 grades in this Q235B ERW welded square rectangular steel tube product line serve fundamentally different load-bearing roles. Q235B, with its moderate yield point, handles secondary framing, scaffolding uprights, and non-critical bracing where weight optimization matters less than cost efficiency. Q345 steps into primary columns and beam-to-column moment connections where higher yield strength reduces section size without sacrificing load capacity. Our own steel production facility rolls both grades in-house, so the mill test certificate traces every heat number back to our melt shop — no third-party sourcing gaps that leave buyers unable to verify chemistry when the inspector asks.
Engineering Compliance Across ASTM, CE, and JIS Frameworks
Structural hollow sections for international projects must satisfy the compliance framework of the destination market. ASTM A500 governs North American structural applications, while EN 10219 covers cold-formed welded structural hollow sections for European projects — and the two standards define different tolerance bands, testing frequencies, and marking requirements [NEED_CITE: steel grade equivalence mapping between ASTM A500 and EN 10219]. CE certification under EN 10210 or EN 10219 is mandatory for structural components entering the EU market, and customs authorities increasingly request the Declaration of Performance alongside the mill certificate. Our ISO 9001 quality system covers the full documentation chain: WPS, PQR, weld maps, dimensional inspection reports, and coating thickness records — prepared before the container is sealed.
ERW Process, Surface Treatment, and Grade Selection Explained
Electric Resistance Welding forms the seam by passing current through the steel strip edges under pressure, creating a forge weld without filler metal. This makes the weld zone narrow and the heat-affected zone minimal — critical for maintaining uniform mechanical properties around the tube perimeter. For Q195 through Q345 grades in the 1.5–30 mm wall thickness range, ERW delivers consistent seam integrity suitable for structural framing and low-to-medium pressure fluid transport. Surface treatment selection depends on the service environment: hot rolled finish works for indoor structural frames where painting follows on site; galvanized coating provides sacrificial zinc protection for outdoor scaffolding and coastal infrastructure; slight oiling prevents transit corrosion during ocean shipping before final surface treatment at destination. The Q-series Chinese grades (Q195, Q215, Q235, Q345) map broadly to S235 and S355 in the European system and ASTM A500 Grade B/C in the American system — but the equivalence is chemical and mechanical, not automatic, and project engineers must confirm acceptance with the specifying authority [NEED_CITE: Q235B to S235JR and ASTM A500 Grade B chemical composition comparison].
Hidden Costs When Material Certification Does Not Match the Purchase Order
Ordering a Q235B ERW welded square rectangular steel tube supplier shipment without verified mill test certificates creates a cascade of downstream failures. If the delivered chemistry does not match the specified grade, the structural engineer cannot sign off on load calculations — and the entire batch becomes scrap or requires costly downgrade negotiation. Wall thickness below the stated tolerance triggers rejection at the third-party inspection stage, and the buyer absorbs demurrage, return freight, or emergency air shipment of replacement material. Certification gaps also block customs clearance in markets requiring CE marking or SGS pre-shipment verification, leaving containers stranded at the port while the project timeline slips [NEED_CITE: consequences of missing CE Declaration of Performance for structural steel imports into EU].
Why Procurement Teams Source This Q235B ERW Welded Square Rectangular Steel Tube from XJY Structure
Our vertically integrated operation eliminates the most common failure point in overseas steel procurement: the gap between material supplier and fabricator. We produce the raw steel on our own mill with three production lines, then fabricate directly in our adjacent workshop — meaning the mill test certificate, the dimensional inspection report, and the welding procedure specification all come from one accountable source. With over 2,800 specifications held in stock, we fill orders for Q235B ERW welded square rectangular steel tube requirements across the full 20×20 to 200×200 mm range without waiting for third-party mill rolling schedules. Our certified welding procedures (AWS and EN qualified) and third-party inspection arrangements through SGS and BV give buyers the documentation package that satisfies both the structural engineer and the customs authority. Professional packing, oversized cargo loading plans, and FOB/CIF/DDP shipping coordination handle the logistics complexity that typically adds weeks to project delivery timelines.
Documentation & Compliance
- Mill Test Certificate documenting Q235B and Q345 chemical composition and mechanical properties per ASTM and GB/T standards, traceable by heat number
- CE Certificate covering EN 10210 hot-finished and EN 10219 cold-formed structural hollow sections for European market compliance
- ISO 9001 quality management certificate covering the full production and inspection workflow from melt to dispatch
- SGS or BV third-party inspection report verifying dimensional accuracy, wall thickness, coating thickness, and visual weld quality before shipment
- Material traceability sheet linking each bundle to its heat number, chemical analysis, and tensile test results
- Complete customs documentation package including packing list, bill of lading, certificate of origin, and commercial invoice
Packaging, Loading & Delivery
- Q235B and Q345 ERW square and rectangular tubes bundled with galvanized steel strips at intervals matched to the 6 m / 6.4 m / 12 m standard lengths, preventing bundle shift during ocean transit
- Galvanized coated tubes wrapped with edge protectors and moisture barrier film to preserve the zinc layer against condensation damage inside the container
- Hot rolled and oiled finish tubes stacked with timber dunnage separators to prevent surface scratching and allow drainage of any residual moisture
- Container loading optimized by mixing 20×20 to 200×200 mm sections to maximize payload within the 25-ton MOQ while respecting weight distribution limits
- Each bundle labeled with heat number, steel grade (Q235B/Q345/S235), size, wall thickness, and length for immediate site identification
- FOB Jinan/Qingdao port with CIF and DDP options available, including professional lashing plans for oversized fabricated components exceeding standard container dimensions
How to Initiate a Procurement Inquiry for Structural Steel Tubes
Submit your project drawings, required steel grades (Q195 through Q345, S235, SS400), section dimensions, wall thickness, surface treatment preference, and destination port — we respond within 24 hours with a detailed quotation covering material, fabrication, coating, packing, and shipping costs. For non-standard dimensions or custom cut lengths outside the 1–12 m range, share your fabrication sequence requirements so we can confirm production scheduling and MOQ alignment. We provide the complete documentation package — mill test certificates, CE declarations, and third-party inspection coordination — before the contract deposit is processed.
Frequently Asked Questions
Q: How do Q235B, S235JR, and ASTM A500 Grade B compare for structural applications?
A: Q235B is the Chinese standard grade with yield strength and chemical composition broadly aligned to S235JR (EN 10025) and ASTM A500 Grade B. The equivalence covers carbon content, manganese range, and minimum yield point, but project engineers must confirm acceptance with the specifying authority, as testing frequency and tolerance bands differ between standards.
Q: Can you provide Mill Test Certificates and arrange third-party inspection?
A: Yes. Every shipment includes a Mill Test Certificate with chemical composition and mechanical properties traceable by heat number. Third-party inspection through SGS or BV can be arranged for dimensional checks, coating thickness measurement, and visual weld inspection before dispatch.
Q: What is the minimum order quantity for custom lengths or non-standard dimensions?
A: The standard MOQ is 25 tons. For custom lengths outside the 6 m / 6.4 m / 12 m standard range or non-standard section sizes, the MOQ depends on the rolling schedule and can be confirmed during the quotation stage.
Q: When should I choose hot rolled, galvanized, or oiled finish?
A: Hot rolled finish suits indoor structural frames where site painting follows installation. Galvanized coating is specified for outdoor exposure, coastal environments, or scaffolding requiring long-term corrosion protection. Slight oiling is a transit-protection measure for ocean shipping when the final surface treatment will be applied at destination.
Q: What is the typical production lead time and do you handle international shipping?
A: Production lead times depend on order volume and specification complexity. We handle FOB, CIF, and DDP shipping with professional packing plans for both standard bundles and oversized fabricated components, coordinating with forwarders for door-to-port or door-to-site delivery.
Start Your Q235B ERW Square Rectangular Steel Tube Inquiry Today
Send your project specifications, steel grade requirements, and destination port to receive a detailed quotation with mill test certificate documentation within 24 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Website: www.xjystructure.com
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@xjystructure.com
Address: No.11889, Jingshi West Road, Lulian Group, Jinan City, Shandong Province, China
