Stainless steel square tubes offer excellent corrosion resistance and structural strength, widely used in construction, machinery, and decoration. This article outlines grades, specifications, surface finishes, and key selection tips.
A stainless steel square tube is a hollow section with square cross-section, produced by welding steel strips or by forming seamless round pipes into square shapes. Advantages:
Corrosion resistance in varied environments.
High structural strength with stable geometry.
Clean appearance with polished surfaces.
Flexible processing for cutting, drilling, welding.
Grade Comparison Table
| Grade |
Main Elements |
Corrosion Resistance |
Typical Use |
| 304/304L |
18Cr-8Ni |
General purpose |
Architecture, furniture, structures |
| 316/316L |
18Cr-12Ni-2Mo |
Better against chlorides |
Coastal buildings, chemical plants |
| 321 |
18Cr-9Ni-Ti |
High-temp stability |
Exhaust, heating equipment |
| Duplex 2205 |
22Cr-5Ni-3Mo |
High strength + pitting resistance |
Marine, petrochemical |
| 310S |
High Cr-Ni alloy |
Oxidation resistance at high temp |
Furnaces, heat equipment |
Welded tubes: rolled and welded strips, then reshaped.
Seamless tubes: pierced round pipes, drawn/extruded into square.
Surface finishes: 2B/BA (industrial), brushed/polished (decorative), electropolished (hygienic).
Standard Sizes
| Outer Size (mm) |
Wall Thickness (mm) |
Length (m) |
Standards |
| 20×20 – 50×50 |
0.8 – 2.0 |
6 |
ASTM A554 |
| 60×60 – 120×120 |
2.0 – 6.0 |
6/12 |
ASTM A554 / EN 10296-2 |
| >150×150 |
6.0 – 12.0 |
Customized |
EN 10210 |
Applications
Construction & structures: curtain walls, rails, posts, frames.
Machinery: conveyor frames, machine parts.
Decoration & furniture: tables, racks, handrails.
Industrial: supports for chemical/food equipment.
Selection & Usage Notes
Choose 316L or duplex for marine/outdoor use.
Ensure welds are passivated after fabrication.
Consider stress concentration at corners in design.
Protect surfaces from chloride exposure in outdoor service.
