Q235 steel is a carbon structural steel widely used in China and internationally. It belongs to the GB/T 700 standard and is divided into four quality grades: Q235A, Q235B, Q235C, and Q235D.
This steel has moderate strength, good plasticity, excellent weldability, and is widely used in construction, engineering, and mechanical applications.
Key Physical Properties:
Density: 7.85 g/cm³ (0.284 lb/in³)
Tensile Strength: 370–500 MPa (54–73 ksi)
Yield Strength: 235 MPa (34 ksi) for steel bar diameter or plate thickness ≤16 mm
No heat treatment required for standard applications
Meaning and Designation
"Q": First letter of the Chinese pinyin "Qu" (屈), meaning Yield Point
"235": Minimum yield strength of 235 MPa
Quality Grades: A, B, C, D – each grade represents increasing control over chemical composition and performance, with Q235B being the most widely used
Features and Applications
Q235 steel is notable for:
Good plasticity, toughness, and weldability
Moderate strength with excellent cold bending properties
Common Forms:
Wire rods, round bars, square bars, flat bars
Angle steel, I-beams, channel beams
Steel plates and steel pipes/tubes
Typical Applications:
Construction: welded structures, factory buildings, bridges, transmission towers
Vehicles and machinery: boilers, containers, lightly stressed rods, brackets, nuts, screws
Mechanical components with moderate stress requirements
Chemical Composition (Heat Analysis, Mass %)
| Steel Grade | Quality | C (%) | Si (%) | Mn (%) | P (%) | S (%) | Deoxidation Method |
|---|---|---|---|---|---|---|---|
| Q235 | A | 0.22 | 0.35 | 1.40 | 0.045 | 0.050 | Rimmed / Killed |
| Q235 | B | 0.20 | 0.35 | 1.40 | 0.045 | 0.045 | Rimmed / Killed |
| Q235 | C | 0.17 | 0.35 | 1.40 | 0.040 | 0.040 | Killed |
| Q235 | D | 0.17 | 0.35 | 1.40 | 0.035 | 0.035 | Exceptionally Killed |
Note: Q235B carbon content can be ≤0.22 % by agreement.
Mechanical Properties
Yield Strength (MPa, ≥) – Thickness / Diameter (mm)
| Steel Grade | Quality | d ≤16 | 16<d ≤40 | 40<d ≤100 | 100<d ≤150 | 150<d ≤200 | Tensile Strength (MPa) |
|---|---|---|---|---|---|---|---|
| Q235 | A/B/C/D | 235 | 225 | 215 | 195 | 185 | 370–500 |
Elongation (%, ≥) – Thickness / Diameter (mm)
| Steel Grade | d ≤40 | 40<d ≤60 | 60<d ≤100 | 100<d ≤150 | 150<d ≤200 |
|---|---|---|---|---|---|
| Q235 | 26 | 25 | 24 | 22 | 21 |
Charpy Impact (V-notch, Longitudinal, ≥J)
| Steel Grade | Quality | Temperature (°C) | Impact Energy (J) |
|---|---|---|---|
| Q235 | B | +20 | 27 |
| Q235 | C | 0 | - |
| Q235 | D | -20 | - |
Cold Bending Test (180°) – Steel Sample Guidance
d ≤60 mm: vertical 2a, horizontal 1.5a–2.5a
B = width of sample steel, a = sample diameter/thickness
Physical Properties of Q235 Steel
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting Point | 1450–1530 °C |
| Specific Heat Capacity | 470 J/(kg·K) |
| Electrical Resistivity | ~0.15 μΩ·m (20 °C) |
| Elastic Modulus | 200 GPa |
| Thermal Conductivity | 49–53 W/m·K |
| Coefficient of Thermal Expansion | 11.3–11.6 ×10⁻⁶ /K |
| Poisson's Ratio | 0.24–0.28 |
Q235 Steel Equivalents (Global Standards)
| Chinese GB/T 700 | US ASTM | EU EN | UK BS | Australia AS/NZS | Japan JIS | India IS |
|---|---|---|---|---|---|---|
| Q235A | - | - | BS 970 Part 1: 080A15 | - | JIS G3101/G3106: SS400, SM400A | IS 2062: E250A |
| Q235B | ASTM A36 / A283: A36 Grade D | EN 10025-2: S235JR (1.0038) | BS EN 10025-2: S235JR | AS/NZS 3678: 250 | JIS G3101/G3106: SS400, SM400A | IS 2062: E250B |
| Q235C | ASTM A36 / A283 / A573: A36 Grade D | EN 10025-2: S235J0 (1.0114) | BS EN 10025-2: S235J0 | AS/NZS 3678: 250L0 | JIS G3106: SM400A, SM400B | IS 2062: E250C |
| Q235D | ASTM A36 / A283M: A36 Grade D | EN 10025-2: S235J0 / S235J2 | BS EN 10025-2: S235J0 / S235J2 | AS/NZS 3678: 250L20 | JIS G3106: SM400A | IS 2062: E250C |
Note: S235JR replaced older S235JRG2 in EN 10025-2 (2004).