Determine the depth of penetration for 0.4% carbon steel heated from 30–900°C at 1000 Hz. The resistivity and permeability at various temperatures is given below.
Temperature °C | Resistivity \rho \times 10^{-6} ohm.cm | Permeability \mu \gamma |
30 | 16 | 40 |
200 | 29.6 | 36 |
400 | 49.3 | 30 |
600 | 76.6 | 15 |
760 | 104.2 | 1 |
900 | 114.6 | 1 |
Substituting
\begin{aligned}\delta_{30} & =5030 \sqrt{\frac{16 \times 10^{-6}}{40 \times 10^3}} \\& =0.101 \ \mathrm{~cm}\end{aligned}Similarly
\begin{aligned}& \delta_{200}=0.135\ \mathrm{~cm} \\& \delta_{400}=0.174 \ \mathrm{~cm} \\& \delta_{600}=0.219 \ \mathrm{~cm} \\& \delta_{760}=1.62 \ \mathrm{~cm} \\& \delta_{900}=1.70 \ \mathrm{~cm}\end{aligned}