The coefficient of thermal expansion (CTE) represents the rate at which a material expands or contracts with changes in temperature. The coefficient of thermal expansion for mild steel is typically around 12 x 10^-6 per degree Celsius (12 μm/m°C) or 6.7 x 10^-6 per degree Fahrenheit (6.7 μin/in°F).
It's important to note that the CTE of mild steel can vary slightly depending on factors such as the specific composition of the steel and its heat treatment. The value mentioned above is an average approximation commonly used for general reference. For precise engineering applications, it is recommended to consult material-specific data or refer to relevant standards and specifications.