Q235B square tube is a hollow structural steel profile with a square or rectangular cross section. It is commonly referred to as a cold-formed steel hollow section.
Using Q235B hot-rolled or cold-rolled strip as the raw material, the tube is shaped through cold bending and subsequently welded using high-frequency welding technology.
For thick-walled or extra-thick square tubes produced by hot rolling, the corner radius and edge flatness can match or even exceed the performance of resistance-welded cold-formed hollow sections.
Seamless vs. Welded Q235B Square Tubes
Welded square tube:
Produced by forming and welding strips/coils. Suitable for general structural use and larger sizes.
Seamless square tube:
Produced from seamless round tubes by extrusion or forming. Offers higher pressure resistance and uniform mechanical properties.
Mechanical Properties Explanation
Plasticity
Plasticity refers to the ability of Q235B steel to undergo permanent deformation without fracture under external load.
Hardness
Hardness evaluates the resistance of steel to deformation or indentation.
Common tests include:
Brinell Hardness (HB)
Rockwell Hardness (HRA/HRB/HRC)
Vickers Hardness (HV)
Impact Toughness
Impact toughness describes the material's ability to withstand sudden impact loads without brittle failure.
Strength
Strength characterizes the ability of the steel to resist deformation or fracture under static loads.
Includes:
Tensile strength
Compressive strength
Bending strength
Shear strength
Tensile strength is typically used as the primary reference index.
Applicable Standards
GB/T6728-2002 – Cold-formed structural hollow sections
JIS G3466-88 – Japanese standard for general structural rectangular/square pipes
EN10025-2:2004 / EN10025-3:2004 – European structural steel standards
Weight Calculation Formulas
Square Tube Weight
Weight (kg) = Side × 4 × Wall Thickness × 0.00785 × Length
Rectangular Tube Weight
Weight (kg) = (Side A + Side B) × 2 × Wall Thickness × 0.00785 × Length
Side & wall thickness = mm
Length = m
Weight = kg
Mechanical Properties & Chemical Composition
Q195
| Element | C | Mn | Si | S | P |
|---|---|---|---|---|---|
| Content (%) | 0.06–0.12 | 0.25–0.50 | ≤0.30 | ≤0.050 | ≤0.045 |
Tensile Strength: 315–430 MPa
Yield Strength: 195 MPa
Elongation: 33%
Q235
| Element | C | Mn | Si | S | P |
|---|---|---|---|---|---|
| Content (%) | 0.12–2.0 | 0.30–0.70 | ≤0.30 | ≤0.045 | ≤0.045 |
Tensile Strength: 375–460 MPa
Yield Strength: 235 MPa
Elongation: 26%
Q345
| Element | C | Mn | Si | S | P | V |
|---|---|---|---|---|---|---|
| Content (%) | ≤0.20 | ≤1.70 | ≤0.55 | ≤0.040 | ≤0.040 | 0.02–0.15 |
Tensile Strength: 470–630 MPa
Yield Strength: 345 MPa
Elongation: 21%
Products Applications
Q235B square tubes are widely used across a broad range of industries thanks to their excellent weldability, strength, and versatility. They are commonly applied in mechanical equipment manufacturing, steel structure engineering, and shipbuilding, where stable load-bearing performance is essential.
In the construction sector, they are frequently used for glass curtain wall frameworks, marble curtain wall dry-hanging systems, and various types of building supports.
In addition, Q235B square tubes are ideal materials for furniture manufacturing, agricultural machinery, chemical equipment, medical devices, and automotive components.
Their stable mechanical properties and customizable sizes make them suitable for both structural and decorative purposes in modern engineering.
Q235B Square Tubes Specifications
| Size (mm) | Wall Thickness (mm) |
|---|---|
| 15×15 | 0.8–1.2 |
| 20×20 | 0.8–3.0 |
| 25×25 | 0.8–3.0 |
| 30×30 | 0.8–4.0 |
| 40×40 | 1.0–5.0 |
| 50×50 | 1.0–6.0 |
| 60×60 | 1.2–6.0 |
| 70×70 | 2.0–6.0 |
| 80×80 | 2.0–8.0 |
| 90×90 | 3.0–10 |
| 100×100 | 2.0–12 |
| 120×120 | 2.0–12 |
| 140×140 | 3.0–12 |
| 150×150 | 3.0–12 |
| 160×160 | 3.0–12 |
| 180×180 | 5.0–12 |
| 200×200 | 4.0–16 |
| 250×250 | 4.0–16 |
| 300×300 | 6.0–16 |
| 350×350 | 6.0–16 |
| 400×400 | 8.0–16 |
| 450×450 | 8.0–16 |
| 500×500 | 8.0–16 |
Q235B Rectangular Tubes Specifications
| Size (mm) | Wall Thickness (mm) |
|---|---|
| 15×30 | 0.8–1.5 |
| 20×40 | 0.8–3.0 |
| 25×50 | 0.8–3.0 |
| 30×50 | 0.8–3.0 |
| 30×60 | 1.5–3.0 |
| 40×80 | 2.0–5.0 |
| 50×70 | 2.0–6.0 |
| 50×100 | 2.0–6.0 |
| 60×80 | 2.0–6.0 |
| 60×100 | 2.0–6.0 |
| 60×120 | 2.0–6.0 |
| 60×160 | 3.0–6.0 |
| 80×100 | 3.0–8.0 |
| 80×120 | 3.0–8.0 |
| 80×160 | 3.0–8.0 |
| 80×200 | 5.0–10 |
| 100×200 | 4.0–12 |
| 100×300 | 5.0–12 |
| 150×300 | 8.0–12 |
| 200×300 | 5.0–16 |
| 200×400 | 8.0–16 |
| 300×400 | 8.0–16 |
