Our Q235B black square tube is a welded carbon steel hollow section with a square cross-section, supplied with a plain black surface and no zinc coating. Q235B is a widely used carbon structural steel grade, and the closed square shape gives good strength and stiffness in every direction. It is used for steel structures, support frames, brackets, and fabrication work, and it is a cost-effective base material that can be painted, galvanized, or powder coated after it is fabricated.
Or email admin@wananelectric.com, or call or WhatsApp +86 18823394830.
Key Features
- Q235B carbon steel: a common structural grade with a minimum yield strength of 235 MPa, and an impact test at room temperature for the B grade
- Square hollow section: equal strength on both axes, good for columns, frames, and supports
- Easy to fabricate: cuts, drills, and welds well, so it is simple to work into frames and brackets
- Black surface: a plain surface ready for painting, hot-dip galvanizing, or powder coating after fabrication
- Cost effective: a lower-cost structural material than galvanized or stainless steel tube
- Flat sides: square faces make fixing, bolting, and welding of plates and brackets easy
- Custom lengths: cut to length and processed on request
Specifications
| Size, Width x Width (mm) | Wall Thickness (mm) | Length (m) |
|---|---|---|
| 20 x 20 | [confirm] | [confirm] |
| 25 x 25 | [confirm] | [confirm] |
| 30 x 30 | [confirm] | [confirm] |
| 40 x 40 | [confirm] | [confirm] |
| 50 x 50 | [confirm] | [confirm] |
| 60 x 60 | [confirm] | [confirm] |
| 80 x 80 | [confirm] | [confirm] |
| 100 x 100 | [confirm] | [confirm] |
Material: Q235B carbon steel. Surface: black, uncoated, [confirm: with or without light oil]. Process: [confirm: welded (ERW) cold-formed or hot-rolled]. Standard: [confirm the product standard, e.g. GB/T 6728 or GB/T 3094, and the dimensional tolerance]. Standard length: [confirm, e.g. 6 m]. Other sizes, wall thicknesses, and lengths are available on request.
Where to Use It
- Steel structure frames and supports
- Equipment bases, platforms, and walkways
- Support frames and brackets for cable tray, pipes, and equipment
- Mounting structure frames and fabricated supports
- General fabrication, fencing, and machinery frames
Black, Pre-Galvanized, or Hot-Dip Galvanized Tube?
| Black tube | Pre-galvanized tube | Hot-dip galvanized tube | |
|---|---|---|---|
| Surface | Plain black steel | Zinc coated before forming | Zinc coated after forming |
| Rust protection | None until painted or coated | Basic, cut edges and welds not coated | Thick zinc on every surface |
| Best for | Indoor or fabricated parts that will be finished later | Dry indoor use | Outdoor and harsh use |
| Cost | Lowest | Medium | Higher |
Good to Know
- Black tube rusts: without a coating, it will rust in damp air. Paint it, galvanize it, or powder coat it after fabrication, and protect it in storage
- Finish after welding: weld the frame first, then galvanize or coat the finished part, so welds and cut edges are covered
- Check the standard: dimensions, wall thickness tolerance, and mechanical properties depend on the product standard, so confirm it against your project specification
- Design by an engineer: member sizes and loads for structures must come from a structural design, not from the tube size alone
- Ask for documents: material certificates showing the grade and test results are available on request
Why Choose Wanan
Wanan has been manufacturing metal products for cable management and electrical installations since 2004, with a 20,000 m² factory. We supply EPC contractors, MEP contractors, and distributors, with drawings, OEM/ODM service, and documents such as material certificates and inspection reports on request. Send us your sizes, wall thickness, finish, and quantity, and our team will quote.
Or email admin@wananelectric.com, or call or WhatsApp +86 18823394830.
