A heat treatment does far more than just change the physical appearance of metals. It also can modify the properties of them to reach the intended goal. This type of treatment involves heating and cooling the metals at the right temperatures to alter their microstructure. How long the treatment requires depends upon the size of the project as well as the type of metal. We will discuss how heat treatments modify the metal properties as well as the different types of these treatments in the following.
The Main Goals of Heat Treatment for Metals
• Increases the hardness and or strength of the metal to make it more durable. It will be additionally resistant to cracks, chips and breaks as a result.
• Softens the chosen metals to increase their workability. This helps to form them into the right shape more effectively. Regardless of how you are moulding the metals into shape, the heating and cooling processes of these treatments can help produce the ideal outcome.
• Heat treatments stabilise the physical and mechanical characteristics of the metal to ensure that they will stand up to a number of environmental and work conditions.
• Lowers the amount of magnetism that a metal has, especially in the case of iron, cobalt and nickel.
• Reduces that amount of residual stress that a fabrication process can inflict on metals. Less damage and waste happen when this stress is lowered.
• Heat treatments ensure the dimensional stability of metal as well in certain circumstances.
• Helps the metals to become resistant to electrical current so that they can be used in a variety of situations involving electricity.
Metals Differ in Their Response to Heat Treatments
Since each metal has a unique chemical composition, metals respond differently to heat treatments regardless of the method that is utilised. Alterations of their structural and physical properties happen when they reach their ideal temperature. Also, their composition will determine the method of heat treatment as well as the time it takes and the rate of cooling that is necessary.
Examples of the Types of Heat Treatment
• Age Hardening uses a low-temperature to perform the heat treatment to strengthen metals.
• Solution Heat Treatment heats metal to the right temperature and then holds it there until the alloy elements turn to a solid state. The metal is then quenched to cool it.
• Precipitation Hardening is a combination of the solution heat treatment, age hardening and quenching and is for increasing the hardness or strength of an alloy.
• Annealing softens the metals by heating them to the correct temperature and then, cooling them slowly to accomplish the desired result.
Ensure that the metals you wish to modify receive the right heat treatment to accomplish your goal. Also, turn to the professionals if you do not have any experience with these treatments to ensure ideal results.
Various properties of metals experience change when they go through a heat treatment. Some changes make the metals more resilient or resistant while others allow them to be reshaped. Even though modern technology has created new methods for this type of treatment, blacksmiths many years ago used to accomplish similar goals by heating and cooling metals for horseshoes, wagon parts and more. To learn additional facts about how heat treatments affect the characteristics of metals, read the following details.
The Effects of Heating Metals
1. Thermal Expansion
As metals are heated, their volume, surface and length will expand. The term for these actions is thermal expansion. Each metal will have a different rate of expansion when exposed to the heat.
2. Structural Alterations
Another effect that heat treatments have on metals is that the structure of them will go through a transformation. This is due to the fact that heat displaces the allotrope atoms in metals and causes them to reform in a different configuration. For this reason, this action is called the allotropic phase transformation. It not only can change the structural shape of the metal, but it also can alter its strength, ductility and hardness of it.
3. Makes the Metals Resistant to Electrical Current
A heat treatment can effectively make a metal have a certain level of electrical resistance. The reason that this happens is that when metals are heated, their electrons can absorb addition energy and makes them move faster than normal.
4. Reduces a Metal’s Magnetism
Magnetic metals such as nickel, cobalt and iron can lose some of their magnetism by undergoing a heat treatment. In some cases, they are no longer magnetic at all.
Types of Heat Treatments
All heat treatments involve heating and cooling metals to change them in some fashion. The most popular reasons for performing these treatments is to increase a metal’s toughness, hardness, strength, corrosion or electrical resistance, and ductility. The following are the most common methods for performing these treatments:
• Annealing softens the metal through heating to make it workable and to increase its ductility. The metal is heated to the appropriate temperature to alter its microstructure and then, it is slow-cooled. It also increases the metal’s electrical conductivity.
• Hardening improves the mechanical properties of steel and other alloys. During this process the metal is heated to a high enough temperature to dissolve a portion of the carbon in it, prior to the appropriate quenching medium being applied. Hardening can increase wear resistance and strength but can also increase brittleness at times, so it is not recommended for some engineering applications.
• Normalising is used on alloys to provide them with a uniform composition and grain.
• Tempering is used on steel to improve its ductility. Steel that does not undergo this process is extremely hard but too brittle to use in many applications.
While there are many other details to learn about how heat treatments affect the properties of metals, the above information gives you a start on your education about this topic. Ensure that your metals receive the appropriate heat method to achieve your purposes.