How does heat-treatment the steel affects properties?
Heat can affect the electrical, magnetic, and structural properties of steels. Since steel has a wide range of uses, various conditions emphasize different attributes. Toughness is required in industrial applications, whereas low electrical density is significant in electronic applications.
There are many methods of heating steel that are widely used to change these properties. To obtain the desired result, the temperature at which the steel is heated and the rate at which it cools is closely regulated.
The following are the most critical ways that steels are converted by heat:
Magnetism
Electrical Resistance
Thermal Expansion
Magnetism
Iron, nickel, and cobalt are the three steels that have magnetic properties. It is referred to as ferromagnetic steel. Heating these steels 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 steel is an indicator of how deeply it obstructs the flow of electrical current. Electrons scatter when they collide with the steellic structure as they flow through the steel. Electrons consume more energy and travel faster while the steel is heated. This causes further scattering, which raises the sum of the resistance. Thermometers typically calculate temperature by measuring the difference of electrical resistance in a piece of wire.
Thermal Expansion
When heated, steel 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 steel. Thermal expansion happens as a result of heat increasing the motions of the steel’s atoms. When building steellic 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 steels
Heat treatment is a method of altering the characteristics of steel in order to make it more suitable for its desired applications. The following are the most common methods of heat treatment:
Annealing
Normalising
Hardening
Tempering
Annealing
Materials such as iron, steel, copper, brass, and silver are commonly softened by annealing. The procedure entails heating the material to a certain degree and then allow to cool slowly and steadily. Annealing changes the steel’s physical and chemical characteristics to make it more ductile and less rigid. This makes for easier carving, stamping, and formation methods, as well as easier cutting of the steel. Electrical conductivity is also improved by annealing.
Normalizing
Normalizing also known as normalization is a process used to achieve uniformity of grain size and composition in alloys. The steel is heated to a certain degree before being cool by air. The resulting steel 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.
Hardening
Steel and other alloys are hardened to enhance their mechanical property. During hardening, the steel is heated to a high temperature and kept there until a proportion of the carbon has been melted. The steel is then put out, which means it is 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
Tempering is used to increase the ductility of steel. Untempered steel is very strong, but it is too porous for the majority of practical applications. Tempering is a low-temperature heat treatment technique used to achieve a desired hardness/toughness ratio after hardening (neutral hardening, double hardening, ambient carburizing, carbonitriding, or induction hardening). To reduce some of the excess hardness, steel is heated to a lower temperature. After that, the steel is able to cool in still air, resulting in a harder and less brittle material.
