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How does heating the metal affects its properties?

Heat can affect the electrical, magnetic, and structural properties of metals. Since metal has various uses, various conditions emphasize different attributes. Toughness is required in industrial applications, whereas low electrical density is significant in electronic applications.



Many methods of heating metal are widely used to change these properties. The temperature at which the metal is heated and the rate at which it cools is closely regulated to obtain the desired result.

Heat’s Impact on Metal

The following are the most critical ways that metals are converted by heat:

  • Magnetism
  • Electrical Resistance
  • Thermal Expansion


Iron, nickel, and cobalt are the three metals that have magnetic properties. It is referred to as ferromagnetic metal. Heating these metals reduces their magnetism to the point that magnetism is no longer there. The Curie temperature is the temperature at which this happens. This temperature is 626 ° Fahrenheit for nickel, 2,012 degrees Fahrenheit for cobalt, and 1,418 ° Fahrenheit for iron.

Electrical Resistance

The electrical resistance of a metal is an indicator of how deeply it obstructs the flow of electrical current. Electrons scatter when colliding with the metallic structure as they flow through the metal. Electrons consume more energy and travel faster while the metal is heated. This causes further scattering, which raises the sum of the resistance. Thermometers typically calculate temperature by measuring the difference in electrical resistance in a piece of wire.

Thermal Expansion

When heated, metal expands. Temperature causes an increase in length, surface area, and thickness. Thermal expansion is the technical name for this. The degree of thermal expansion varies depending on the metal. Thermal expansion happens due to heat increasing the motions of the metal’s atoms. When building metallic structures, it is critical to account for thermal expansion. A simple example is the construction of household pipes, which must allow for expansion and contraction as the seasons shift.

Heat Treatment on metals
Heat treatment is a method of altering the characteristics of metal to make it more suitable for its desired applications. The following are the most common methods of heat treatment:

  • Annealing
  • Normalising
  • Hardening
  • Tempering


Annealing commonly softens materials such as iron, steel, copper, brass, and silver. The procedure entails heating the material to a certain degree and then allow to cool slowly and steadily. Annealing changes the metal’s physical and chemical characteristics to make it more ductile and less rigid. This makes for easier carving, stamping, and formation methods and easier cutting of the metal. Electrical conductivity is also improved by annealing.


Normalizing, also known as normalization, is a process used to achieve uniformity of grain size and composition in alloys. The metal is heated to a certain degree before being cool by air. The resulting metal is free of impurities and has increased strength and hardness. Normalizing is often used to manufacture harder and tougher steel, but it is less ductile than annealing. Since the procedure improves this attribute, the normalizing process is typically done on products that may be exposed to machining.


Steel and other alloys are hardened to enhance their mechanical property. During hardening, the metal is heated to a high temperature and kept until a proportion of the carbon has melted. The metal is then put out and quickly cooled in oil or water. Hardening results in an alloy with high strength and wear-resistant. Hardening, on the other hand, makes it more brittle and is thus unsuitable for industrial application. Surface hardening is used where the surface of a part has to be hard enough to prevent wear and degradation while preserving ductility and resilience to withstand impact and shock loading.


Tempering is used to increase the ductility of steel. Untempered steel is solid, but it is too porous for the majority of practical applications. Tempering is a low-temperature heat treatment technique to achieve a desired hardness/toughness ratio after hardening (neutral hardening, double hardening, ambient carburizing, carbonitriding, or induction hardening). Steel is heated to a lower temperature to reduce some of the excess hardness. After that, the metal can cool in still air, resulting in a more rigid and less brittle material.



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