Q235 steel is a low-carbon structural steel widely used in construction and engineering applications. The different grades A, B, C, D, and E represent the steel's impact performance at various temperatures, as well as slight differences in chemical composition.
Impact Performance by Grade
| Grade | Impact Test Temperature | Notes |
|---|---|---|
| Q235A | ≥ +40°C | High-temperature impact performance |
| Q235B | ≥ +20°C | Standard room temperature impact; most commonly used |
| Q235C | ≥ 0°C | Moderate cold-temperature impact |
| Q235D | ≥ -20°C | Low-temperature impact |
| Q235E | ≥ -40°C | Very low-temperature impact; suitable for extreme cold environments |
Explanation: The grade indicates the steel's toughness under impact at different temperatures. For example, Q235B is tested at room temperature (20°C), Q235C at 0°C, and Q235D at -20°C. Lower temperatures generally reduce impact values, so higher-grade steels are selected for harsher environmental conditions.
Chemical Composition by Grade
| Grade | C (%) | Mn (%) | Si (%) | S (%) | P (%) |
|---|---|---|---|---|---|
| Q235A | ≤0.22 | ≤1.4 | ≤0.35 | ≤0.050 | ≤0.045 |
| Q235B | ≤0.20 | ≤1.4 | ≤0.35 | ≤0.045 | ≤0.045 |
| Q235C | ≤0.17 | ≤1.4 | ≤0.35 | ≤0.040 | ≤0.040 |
| Q235D | ≤0.17 | ≤1.4 | ≤0.35 | ≤0.035 | ≤0.035 |
Notes on Elemental Content:
Sulfur content decreases progressively from A → D, improving steel toughness.
Phosphorus content: A and B share similar levels; C is slightly lower; D is the lowest to enhance low-temperature impact resistance.
Temperature suitability: A (highest) → E (lowest), corresponding to the steel's impact resistance under different environmental conditions.
Chemical composition: Slightly reduced C, S, and P content from A to D to improve toughness at lower temperatures.
Q235B is the most commonly used grade for standard construction at normal temperatures, offering a good balance of weldability, strength, and cost-effectiveness.
