Pure Iron
Pure Iron is produced in small quantities and is used principally for research purpose. It is also used largely as the basic material for (re-)melting of low-carbon, stainless and acid-resistant steels, materials with a high nickel content, magnetic alloys as well as stainless and heat resistant steel castings in induction and vacuum furnaces.
There are many types of pure Iron such as Zone-refined iron, Armco ingot iron and electrolytic iron. The chemical compositions of some relatively pure irons are (%):
- C (0.012-0.005), Mn(0.028-0.17),P(0.004-0.005),S(0.025-0.003),Si(0.005-0.0012)
- The yield strength of pure iron is very low and small quantities of elements such as C, Mn, P and S can increase the yield strength therefore the purity of iron must be slight less than pure iron (99.9%).
Table 1 shows the properties of pure Iron
| Atomic number | 26 |
| Atomic radius( nm ) | 0.128 |
| Atomic weight | |
| Crystal structure | Body centred cubic |
| Hardness - Mohs | 4.0-5.0 |
| Tensile modulus ( GPa ) | 211.4 |
| Tensile strength ( MPa ) | 180-210 |
| Yield strength ( MPa ) | 120-150 |
| Boiling point(°C) | 2750 |
| Density( g cm-3 ) | 7.87 |
| Melting point (°C) | 1535 |
| Latent heat of evaporation ( J g-1 ) | 6095 |
| Latent heat of fusion ( J g-1 | 272 |
| Specific heat in 25°C ( J K-1 kg-1 ) | 444 |
| Thermal conductivity in100 °C ( W m-1 K-1 | 80.4 |
Fig 1 shows the cooling curve for pure iron
Pure iron exist in the following allotropic and phases forms:
- α-Fe( α-ferrite) is Bcc solid solution, Max solubility of C is 0.022 wt %,RT solubility of C is 0.008 wt %
- γ-Fe (γ-austenite) is Fcc solid solution,Max solubility of C is 2.14 wt%
- ∂-Fe(∂-ferrite) is Bcc solid solution, Stable only at high T, Max solubility of C is 0.10 wt %
- Fe3C (iron carbide/ cementite), Orthorhombic structure, Intermetallic, Brittle
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