Description
Factory-direct ERW RHS/SHS mill — Q235B welded rectangular steel tubes rolled on dedicated lines with in-house dimensional and chemical testing before every shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Welded Rectangular Steel Tube |
| Product Type | Welded Square and Rectangular Steel Tube (RHS/SHS) |
| Steel Grade | Q235B, Gr.B, S235, S275, S355, STK400 |
| Standard | ASTM A500, ASTM A53, GB/T 3091 |
| Section Shape | Square and Rectangular |
| Size Range | 15mm×20mm – 700mm×800mm |
| Wall Thickness | 1 – 30 mm |
| Length | 5.8m / 6m / 11.8m / 12m / Random Length |
| Technique | ERW (Welded) |
| Surface Treatment | Black Painting / Galvanized / Varnish / Bare |
| Tolerance | ±1% |
| Ends | Plain |
| Application | Steel structures / Construction frames / Curtain wall / Support tubes / Building frames |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Commercial Construction | Building frames, column sections, mezzanine supports |
| Architectural Facades | Glass curtain wall mullions, sharp-corner exposed steel framing |
| Industrial Structures | Equipment support stands, conveyor gantries, platform handrails |
| Infrastructure | Bridge parapet posts, signage gantry columns, utility support frames |
What Rounded Corners Cost a Curtain Wall Contractor
Standard ERW rectangular tubes leave R≥2t radius corners that force facade fabricators to grind, fill, or sleeve joints before glass panels can seat flush.
When a project specifies exposed steel framing for a glass curtain wall, even a 3mm corner radius compounds across dozens of mullion intersections — creating visible gaps, misaligned sight-lines, and extra shop-floor labor that the original budget never covered. Sourcing a Q235B welded rectangular steel tube supplier who can deliver true sharp-corner sections in the same size range eliminates that rework entirely. [NEED_CITE: cold-formed hollow section dimensional tolerance requirements for architectural applications]
Matching Wall Thickness to Curtain Wall Span Loads
Facade engineers specifying Q235B welded rectangular steel tube sections for curtain wall mullions typically need wall thickness between 3mm and 8mm to resist wind pressure deflection over 3–6m spans. The ±1% ERW tolerance keeps corner geometry consistent along the full 6m or 12m length, so glass retention clips seat uniformly without shimming. For ground-floor entrance canopies carrying higher point loads, stepping up to S355 grade in the same outer dimensions raises yield capacity without changing the architectural profile.
Structural Code Compliance and Certification Pathways
Load-bearing frames for commercial buildings must satisfy EN 1993 or AISC design rules, which reference material certificates traceable to heat numbers. A Q235B welded rectangular steel tube supplied with EN 10204 3.1 mill test certificates lets the structural engineer sign off without requesting additional third-party testing. For EU-bound shipments, Lloyd’s CE marking under EN 10219 confirms the hollow sections meet harmonized product standards — without it, customs at Rotterdam or Hamburg will hold the container pending documentation review. [NEED_CITE: EN 10219 cold-formed structural hollow sections CE marking requirements]
How ERW Welding and Grade Selection Shape the Final Frame
Q235B remains the workhorse grade for non-critical structural frames across Southeast Asia and the Middle East because it welds easily, bends predictably, and costs less per ton than S-series equivalents. Where projects demand higher strength-to-weight ratios — long-span warehouse portals, crane runway beams — S355 delivers noticeably higher yield strength in the same wall thickness, reducing total tonnage on the shipping manifest. The ERW process forms the tube from coil through continuous roll-forming and high-frequency welding, producing a clean internal weld bead suitable for black painting, hot-dip galvanizing, or bare delivery depending on the corrosion environment. Sharp-corner rectangular tubes use a separate patented forming sequence that achieves near-90° internal radii, giving architectural facades the crisp sight-lines that rounded-corner ERW tubes cannot replicate.
Hidden Costs When Mill Certificates Do Not Match the Heat
Ordering Q235B welded rectangular steel tube based on price alone often surfaces problems at the destination port: wall thickness measured below the stated 3mm minimum triggers rejection under ASTM A500 tolerance rules; a missing CE mark delays EU customs clearance by weeks; or the chemical composition on the certificate does not match the heat number stamped on the tube, forcing the contractor to pay for independent re-testing. Each scenario adds crane time, storage fees, and schedule delays that dwarf the original per-ton savings. [NEED_CITE: consequences of non-conforming mill test certificates in structural steel procurement]
Why Project Buyers Source From Our Jinan Mill
We roll Q235B welded rectangular steel tube on three dedicated ERW lines covering 2,800+ size combinations — from 15×20mm thin-wall decorative sections up to 700×800mm heavy structural boxes with wall thickness reaching 30mm. Our in-house physical and chemical laboratory tests every heat for composition, yield, tensile, and elongation before the mill test certificate is issued, so the document arriving with your container matches the steel on the truck. The sharp-corner rectangular tube technology we patented — 41 invention patents in total — fills the gap that standard rounded-corner mills cannot serve for curtain wall and facade contractors. Full international certification coverage includes ISO 9001:2015, Lloyd’s CE under EN 10210 and EN 10219, and Singapore FPC, with SGS or BV third-party inspection arranged on request. Custom non-standard sizes and cut-to-length service keep MOQ practical for mid-volume project orders, and our loading team uses purpose-built cradles and edge protectors to prevent surface damage during ocean transit to EU, Middle East, and Southeast Asian ports.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition and mechanical properties per GB/T 3091, traceable to heat number
- CE certificate under EN 10219 for cold-formed structural hollow sections shipped to EU member states
- ISO 9001:2015 quality management certificate covering the full ERW welding and forming process
- SGS or BV third-party inspection report verifying dimensional tolerance and surface finish before loading
- Material traceability sheet linking each bundle to its heat number, chemical analysis, and mechanical test results
- Export customs package including packing list, bill of lading, and certificate of origin for destination clearance
Packaging, Loading & Delivery
- Q235B black-painted rectangular tubes bundled with steel strips and separated by rubber pads to prevent coating abrasion during ocean transit
- Hot-dip galvanized RHS/SHS sections wrapped with waterproof cloth and edge protectors to preserve zinc coating integrity through container loading
- 6m and 12m fixed lengths loaded in dedicated 20ft or 40ft containers with timber chocks; random-length bundles sized to maximize payload per TEU
- Cut-to-length service available for 5.8m and 11.8m requirements matching standard container internal dimensions, reducing on-site cutting waste
- Heat number and steel grade stenciled on each bundle tag; shipping marks customized to buyer’s import license requirements
- FOB Jinan or Qingdao port as standard, with CIF and DDP routing available to major ports across EU, Middle East, and Southeast Asia
Requesting a Project-Specific Quotation
Submit your section dimensions, wall thickness, steel grade preference, surface treatment, and total tonnage to receive a detailed quotation including unit price, production lead time, and mill test certificate format confirmation. For curtain wall or facade projects requiring sharp-corner rectangular tubes, share the corner radius tolerance so our engineering team can confirm the patented forming process matches your specification. We will also advise on the most efficient container loading plan once quantities and lengths are confirmed.
Frequently Asked Questions
Q: Can Q235B be substituted with S235JR or ASTM A500 Gr.B on the same project?
A: Yes — Q235B, S235JR, and ASTM A500 Gr.B occupy equivalent positions in their respective national standards for mild structural carbon steel. We supply all three grades on the same ERW line and issue the appropriate mill test certificate referencing the standard your engineer specified.
Q: What is the difference between standard ERW rectangular tubes and your sharp-corner rectangular tubes?
A: Standard ERW rectangular tubes produce corner radii of R≥2t due to the roll-forming process. Our patented sharp-corner technology achieves near-90° internal angles, which is essential for glass curtain wall mullions and exposed architectural facades where rounded corners create visible joint gaps.
Q: Do you provide third-party inspection before shipment?
A: Yes. SGS and BV inspection teams can attend dimensional checks, visual surface inspection, and witness mechanical testing at our in-house laboratory before the container is sealed. The inspection report is issued alongside the mill test certificate.
Q: What surface treatment options are available for Q235B welded rectangular steel tube?
A: We offer black painting, hot-dip galvanizing, varnish coating, and bare (oiled) delivery. Galvanizing is recommended for outdoor or high-humidity environments; black painting suits indoor structural frames where appearance is secondary; bare delivery works for projects that will apply their own coating system on site.
Q: What is the minimum order quantity for custom non-standard sizes?
A: Standard sizes ship from stock with flexible MOQ. Custom non-standard dimensions enter production with a practical minimum that we confirm after reviewing the drawing — typically lower than overseas mills require, making small-batch facade orders viable.
Get Your Q235B Welded Rectangular Steel Tube Quote Today
Send your size list, steel grade, surface finish, and destination port to receive pricing, production lead time, and a sample mill test certificate format within 12 hours.
Shandong Xin Jiyuan Special Steel Tube Co., Ltd
Tel: +86 531 8573 6315
Mobile/WhatsApp/WeChat: +86 188 5315 7756
Email: admin@sdxjypipe.com
