Carbon structural steel grades are widely used in various industrial applications due to their mechanical properties and cost-effectiveness. These steels are classified based on their chemical composition, mechanical characteristics, and intended use. Below is a detailed overview of different carbon structural steel grades, including their chemical compositions, mechanical properties, and typical applications.
**Chemical Composition of Carbon Structural Steel Grades**
| Brand | Grade | Chemical Composition (mass fraction) (%) | Deoxygenation Method |
|-------|--------|------------------------------------------|----------------------|
| | | C | Mn | Si | S | P | |
| Q195 | | 0.06–0.12 | 0.25–0.50 | 0.30 | 0.050 | 0.045 | F, b, Z |
| Q215 | A | 0.09–0.15 | 0.25–0.55 | 0.30 | 0.050 | 0.045 | F, b, Z |
| | B | 0.045 | | | | | |
| Q235 | A | 0.14–0.22 | 0.30–0.65 | 0.30 | 0.050 | 0.045 | F, b, Z |
| | B | 0.12–0.20 | 0.30–0.70 | | 0.045 | | |
| | C | ≤0.18 | 0.35–0.80 | | 0.040 | 0.040 | Z |
| | D | ≤0.17 | | | 0.035 | 0.035 | TZ |
| Q255 | A | 0.18–0.28 | 0.40–0.70 | 0.30 | 0.050 | 0.045 | Z |
| | B | 0.045 | | | | | |
| Q275 | | 0.28–0.38 | 0.50–0.80 | 0.35 | 0.050 | 0.045 | Z |
*Note: F stands for boiling steel, b for semi-killed steel, z for killed steel, and TZ for special killed steel.*
**Yield Point of Carbon Structural Steel**
| Brand | Grade | Yield Point (σs/MPa) | Steel Thickness or Diameter (mm) |
|-------|--------|----------------------|----------------------------------|
| | | | ≤16 | >16–40 | >40–60 | >60–100 | >100–150 | >150 |
| Q195 | | ≥ | 195 | 185 | | | | |
| Q215 | A, B | ≥ | 215 | 205 | 195 | 185 | 175 | 165 |
| Q235 | A, B | ≥ | 235 | 225 | 215 | 205 | 195 | 185 |
| | C, D | ≥ | 235 | 225 | 215 | 205 | 195 | 185 |
| Q255 | A, B | ≥ | 255 | 245 | 235 | 225 | 215 | 205 |
| Q275 | | ≥ | 275 | 265 | 255 | 245 | 235 | 225 |
*Note: The yield point of Q195 is for reference only and not a delivery condition.*
**Tensile Strength, Elongation, and Impact Properties**
| Brand | Tensile Strength (σb/MPa) | Elongation (δ5/%) | Impact Test (V-notch, Ak/J) | Temperature (°C) |
|-------|----------------------------|-------------------|----------------------------|------------------|
| Q195 | 315–430 | 33 | – | – |
| Q215 | 335–450 | 31 | 26 | 20 |
| Q235 | 375–500 | 26 | 20 | 20 |
| Q255 | 410–550 | 24 | 19 | 20 |
| Q275 | 490–630 | 20 | – | – |
*Note: Impact tests are conducted at different temperatures, with values indicating the minimum energy absorption required.*
**Cold Bending Properties**
| Brand | Sample Orientation | 180° Cold Bending Test (B=2a/mm) |
|-------|--------------------|----------------------------------|
| | | 60 | >60–100 | >100–200 |
| Q195 | Vertical | 0 | – | – |
| | Horizontal | 0.5a | – | – |
| Q215 | Vertical | 0.5a | 1.5a | 2a |
| | Horizontal | a | 2a | 2.5a |
| Q235 | Vertical | a | 2a | 2.5a |
| | Horizontal | 1.5a | 2.5a | 3a |
| Q255 | | 2a | 3a | 3.5a |
| Q275 | | 3a | 4a | 4.5a |
*Note: "a" refers to the thickness or diameter of the steel, while "B" represents the width of the sample.*
**Characteristics and Applications of Carbon Structural Steel**
| Brand | Main Characteristics | Application Examples |
|-------|----------------------|----------------------|
| Q195 | High plasticity, toughness, and weldability; low strength | Anchor bolts, ploughshares, chimneys, rivets, thin plates, welded pipes, and structures |
| Q215 | Good ductility, weldability, and cold stamping performance | General parts, brackets, frames, and building structures |
| Q235 | Balanced properties: good plasticity, toughness, weldability, and strength | Widely used in general engineering structures, bridges, and mechanical components |
| Q255 | Good strength, ductility, and weldability | Bolts, keys, shafts, and structural steel components |
| Q275 | High strength, good plasticity, and machinability | Gears, sprockets, agricultural machinery parts, and conveyor chains |
Carbon structural steel grades offer a versatile range of options for engineers and manufacturers, depending on the required strength, formability, and application environment. Each grade has its own unique set of properties that make it suitable for specific uses, from lightweight construction materials to heavy-duty mechanical parts. Understanding these differences helps in selecting the right material for the job.
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