The coefficient of thermal expansion of steel is alpha L. definition: The relative elongation of the object increases with the temperature rising by 1 C.
The coefficient of thermal expansion is not constant, but varies slightly with the change of temperature.


The size of the original length L1 and L2 is warming. L is the amount of deformation (L2-L1), T1 is the original temperature, T2 is the temperature, and T is the temperature difference (T2-T1).


The change of body temperature caused by expansion is called "thermal expansion". Usually refers to the external pressure under the same conditions, most materials at high temperature, its volume increases, temperature decreases, volume decreases. Under the same conditions, gas expansion is the largest, followed by liquid expansion and solid expansion is the smallest. In a certain temperature range, the temperature of a few substances increases, but their volume decreases. Because of body temperature, the average kinetic energy of molecule movement increases, and the distance between molecules increases, so the volume of the object expands. When the temperature decreases, the average kinetic energy of the object becomes small molecule when it is cooled, and the distance between molecules shortens, so the volume of the object will shrink. In addition, due to the average kinetic energy of the motion of solids, liquids and gases with different sizes, there are also significant differences in the thermal expansion of macroscopic phenomena.