Heated metal bars.

How Heating Metals Affects It’s Properties

When heat is applied to metal their electrical and structural properties can change.  As the application of metals are varied, different environments prioritize different qualities.  There are a number of ways of heating metal which are commonly used to transform these properties.  The temperature of which the metal is heated and the rate of cooling are carefully controlled to achieve the desired outcome.   

The Effect Of Heat On Metal 

The most important ways that metals are transformed through heat:


  • Electrical Resistance 
  • Thermal Expansion
  • Structure 
  • Magnetism


Electrical Resistance 

Electrical resistance is the measure of how strongly metal impedes the passing of electrical currents.  As the electrons pass through the metal they collide with the metallic structure.  The heat acts as a boost for the electrons providing them with more speed as they move. This creates a scattering frenzy with the electrons which creates resistance.  

Thermal Expansion

Metal expands as it is exposed to heat.  Length, surface area and volume will increase at temperature.  The scientific term for this process is thermal expansion.  Now, the metal will determine the degree of expansion.  Thermal expansion occurs because the heat increases the vibration of the atoms in the metal.  Accounting for thermal expansion is essential when designing metallic structures.  One great example is household pipes as they have to be able to withstand both the expansion and contraction as the seasons change.  


Metals are composed of symmetrical structures of atoms known as allotrope.  When heat is applied it displaces the atoms from their position causing them to form a new structure.  This is known as allotropic phase transformation.  Allotropic phase transformation alters the hardness, strength, and ductility of the metal.  The most important allotropic phase transformation is conducted on iron.  

When iron is heated past 1,674 degrees Fahrenheit it is able to absorb more carbon, which is an ingredient that will increase the hardness of any steel product.  This effect is commonly used in several types of high carbon steel.  

Heat Treatment

Heat treatment is a process designed to alter the properties of the metal to better suit its intended use.  The main type of heat treatments are: 

  • Annealing 
  • Normalising
  • Hardening 
  • Tampering 


Contact Markham Metals

Markham Metals has the facility and machinery to conduct all metal fabrication needs to fulfill your project.  We offer professional services that range from welding to bending along with a wide variety of steel products.  Contact us today for more information on our products and services.