Steel is often categorized according to its carbon content. All steel contains at least some amount of carbon. After all, steel is defined as an alloy of iron and carbon. Without the presence of carbon, it would simply be iron. By adding carbon to it, the metal becomes stronger and harder. This is why many manufacturing and construction companies prefer steel over conventional iron.
Low-carbon steel is characterized by a low ratio of carbon to iron. By definition, low-carbon consists of less than 0.30% of carbon. Also known as mild steel, it costs less to produce than both medium-carbon and high-carbon steel. In addition to its low cost, low-carbon steel is more pliable, which may improve its effectiveness for certain applications while lowering its effectiveness for other applications.
Low-carbon steels do not have sufficient hardenability to form martensite except in the thinnest sections and are therefore produced primarily with ferritic microstructures, which have excellent ductility for cold-working and forming operations.
Low-carbon steels, e.g. case-hardenable as well as QT steels are soft-annealed to improve their cold workability. Many hobbed or cold-extruded shapes are only possible with very soft steels. This state is too soft for cutting because it produces a continuous chip. The treatment process is included in the designation of the material, e.g. 34Cr4A (annealed) or 34Cr4AC (spheroidised annealed).
| Low Carbon Steel Properties | |||
| Physical Properties | Metric | English | Comments |
|---|---|---|---|
| Density | 2.85 – 8.08 g/cc | 0.103 – 0.292 lb/in³ | Average value: 7.60 g/cc Grade Count:1327 |
| Mechanical Properties | Metric | English | Comments |
| Hardness, Brinell | 86 – 550 | 86 – 550 | Average value: 247 Grade Count:809 |
| Hardness, Knoop | 103 – 682 | 103 – 682 | Average value: 278 Grade Count:728 |
| Hardness, Rockwell B | 30 – 105 | 30 – 105 | Average value: 89.4 Grade Count:764 |
| Hardness, Rockwell C | 10 – 64 | 10 – 64 | Average value: 31.7 Grade Count:518 |
| Hardness, Vickers | 22 – 661 | 22 – 661 | Average value: 266 Grade Count:730 |
| Tensile Strength, Ultimate | 241 – 2450 MPa | 35000 – 355000 psi | Average value: 716 MPa Grade Count:1303 |
| Tensile Strength, Yield | 140 – 2400 MPa | 20300 – 347000 psi | Average value: 519 MPa Grade Count:1295 |
| Elongation at Break | 3.0 – 48 % | 3.0 – 48 % | Average value: 20.2 % Grade Count:1290 |
| Reduction of Area | 15.4 – 75 % | 15.4 – 75 % | Average value: 53.4 % Grade Count:507 |
| Modulus of Elasticity | 183 – 213 GPa | 26500 – 30900 ksi | Average value: 202 GPa Grade Count:1096 |
| Compressive Yield Strength | 152 – 1800 MPa | 22000 – 260000 psi | Average value: 1480 MPa Grade Count:14 |
| Bulk Modulus | 148 – 163 GPa | 21500 – 23600 ksi | Average value: 160 GPa Grade Count:1028 |
| Poissons Ratio | 0.25 – 0.30 | 0.25 – 0.30 | Average value: 0.290 Grade Count:978 |
| Fatigue Strength | 758 – 772 MPa | 110000 – 112000 psi | Average value: 765 MPa Grade Count:4 |
| Fracture Toughness | 33.0 – 115 MPa-m½ | 30.0 – 105 ksi-in½ | Average value: 68.2 MPa-m½ Grade Count:16 |
| Machinability | 50 – 160 % | 50 – 160 % | Average value: 61.3 % Grade Count:575 |
| Shear Modulus | 70.0 – 80.0 GPa | 10200 – 11600 ksi | Average value: 79.7 GPa Grade Count:1100 |
| Izod Impact | 35.0 – 138 J | 25.8 – 102 ft-lb | Average value: 96.5 J Grade Count:81 |
| Charpy Impact | 14.0 – 339 J | 10.3 – 250 ft-lb | Average value: 54.9 J Grade Count:13 |
| Bend Radius, Minimum | 0.00 – 10 t | 0.00 – 10 t | Average value: 2.46 t Grade Count:87 |
| Electrical Properties | Metric | English | Comments |
| Electrical Resistivity | 0.0000142 – 0.000142 ohm-cm | 0.0000142 – 0.000142 ohm-cm | Average value: 0.0000220 ohm-cm Grade Count:948 |
| Thermal Properties | Metric | English | Comments |
| CTE, linear | 10.1 – 16.6 µm/m-°C | 5.61 – 9.22 µin/in-°F | Average value: 12.5 µm/m-°C Grade Count:575 |
| Specific Heat Capacity | 0.450 – 0.486 J/g-°C | 0.108 – 0.116 BTU/lb-°F | Average value: 0.473 J/g-°C Grade Count:857 |
| Thermal Conductivity | 25.3 – 93.0 W/m-K | 176 – 645 BTU-in/hr-ft²-°F | Average value: 49.6 W/m-K Grade Count:1002 |
| Melting Point | 1430 °C | 2600 °F | Average value: 1430 °C Grade Count:3 |
| Maximum Service Temperature, Air | 400 – 677 °C | 752 – 1250 °F | Average value: 637 °C Grade Count:7 |
| Component Elements Properties | Metric | English | Comments |
| Aluminum, Al | 0.010 – 1.5 % | 0.010 – 1.5 % | Average value: 0.468 % Grade Count:69 |
| Boron, B | 0.00050 – 0.0060 % | 0.00050 – 0.0060 % | Average value: 0.00268 % Grade Count:127 |
| Carbon, C | 0.0030 – 0.80 % | 0.0030 – 0.80 % | Average value: 0.185 % Grade Count:1289 |
| Chromium, Cr | 0.20 – 10 % | 0.20 – 10 % | Average value: 0.883 % Grade Count:505 |
| Cobalt, Co | 7.5 – 12 % | 7.5 – 12 % | Average value: 8.75 % Grade Count:32 |
| Copper, Cu | 0.020 – 1.5 % | 0.020 – 1.5 % | Average value: 0.371 % Grade Count:161 |
| Iron, Fe | 63 – 100 % | 63 – 100 % | Average value: 96.6 % Grade Count:1306 |
| Lead, Pb | 0.15 – 0.36 % | 0.15 – 0.36 % | Average value: 0.251 % Grade Count:7 |
| Manganese, Mn | 0.10 – 2.2 % | 0.10 – 2.2 % | Average value: 0.827 % Grade Count:1277 |
| Molybdenum, Mo | 0.050 – 4.8 % | 0.050 – 4.8 % | Average value: 0.460 % Grade Count:743 |
| Nickel, Ni | 0.030 – 18.5 % | 0.030 – 18.5 % | Average value: 2.62 % Grade Count:584 |
| Niobium, Nb (Columbium, Cb) | 0.0050 – 0.15 % | 0.0050 – 0.15 % | Average value: 0.0485 % Grade Count:73 |
| Nitrogen, N | 0.0010 – 0.070 % | 0.0010 – 0.070 % | Average value: 0.0134 % Grade Count:38 |
| Phosphorus, P | 0.0010 – 0.40 % | 0.0010 – 0.40 % | Average value: 0.0369 % Grade Count:1239 |
| Silicon, Si | 0.010 – 1.0 % | 0.010 – 1.0 % | Average value: 0.293 % Grade Count:977 |
| Sulfur, S | 0.0010 – 0.50 % | 0.0010 – 0.50 % | Average value: 0.0435 % Grade Count:1264 |
| Titanium, Ti | 0.010 – 1.4 % | 0.010 – 1.4 % | Average value: 0.355 % Grade Count:57 |
| Vanadium, V | 0.0050 – 0.95 % | 0.0050 – 0.95 % | Average value: 0.0912 % Grade Count:89 |
| Zirconium, Zr | 0.010 – 0.15 % | 0.010 – 0.15 % | Average value: 0.0271 % Grade Count:35 |
