What is Heat Treatment? Process & Benefits

What is Heat Treatment- Process & Benefits

Brief Overview of the Topic and Its Benefits

We use metals every day. We use them in our phones and in our computers as well as in our vehicles and our buildings. But before these metals can be used for such purposes, they must first undergo the heat treatment process.

Heat treatment is widely used to prepare metals for everyday use. The process involved heating and cooling the metal in order to improve its properties. Different methods are used to achieve different desired properties depending on what we intend to use the metal for.

Some of these beneficial properties include increased strength and durability as well as increased corrosion resistance. So what is heat treatment, and how does it work? Let’s take a look.

What is Heat Treatment?

Heat treatment of metals is a process that uses heating and cooling to alter the physical and sometimes chemical properties of the metal. This is done in order to improve the metal’s physical properties, most commonly to increase its strength.

Other advantages of heat treatment include corrosion resistance by creating a barrier to protect the metal and improved wear resistance by hardening the metal.

The main key benefits of heat treatment that we will discuss in this blog include improving workability and machinability, improving wear resistance and durability, improving strength and toughness, and improving magnetic properties.

The 3 Stages of Heat Treatment Process

  • Heating
  • Holding
  • Cooling

There are three stages in the heat treatment process. They are as follows, heating, holding, and finally, cooling.

Stage One: Heating

Stage One- Heating

The first stage of the heat treatment process is heating. During this stage, the metal will be heated to a specific temperature. The exact temperature you heat the metal will depend on the metal you are working with and your desired outcome.

For example, to harden a metal, you will heat it to a temperature above its critical point, and to make a metal less brittle, you would heat it to a temperature below its critical point.

Stage Two: Holding

Once the metal has been heated, it is time for stage two holding, sometimes referred to as soaking. During this stage, the metal is held at the temperature for a certain amount of time, depending on the metal you are working with and the desired outcome.

This is important in objects where you need the metal to have uniform properties.

Holding the metal in the heat allows time for the metal properties to change internally, not just on the surface. This is beneficial as it makes the metal material tougher and more resistant to wear.

Stage Three: Cooling

Stage Three- Cooling

Once the metal has been held at the required temperature for the required time, it is time for it to be cooled. Cooling, like holding, can be done in different ways, causing different outcomes. If the metal is cooled rapidly, it will become harder and more brittle.

Alternatively, if the metal is cooled slowly, known as annealing, it will make it more ductile and less brittle.

The Key Benefits of Heat Treating Your Metals

The Key Benefits of Heat Treating Your Metals

  • Improving Workability and Machinability
  • Improving Wear Resistance and Durability
  • Improving Strength and Toughness
  • Improving Magnetic Properties

There are numerous benefits to heat treating your metals. The four main benefits are improving workability and machinability, improving wear resistance and durability, improving strength and toughness, and improving magnetic properties.

Key Benefit One: Improving Workability and Machinability

Key Benefit One- Improving Workability and Machinability

Heat treatment can improve the workability and machinability of a metal, saving time and money by making it more malleable. The more malleable material will be easier to work with and less likely to break during manufacturing.

Heat-treated metals will also be of a better quality as opposed to the same metal that has not been heat treated.

Key Benefit Two: Improving Wear Resistance and Durability

The wear resistance and durability of metal can be improved through heat treatment by hardening the metal. A metal such as steel can be hardened just on the surface, known as case hardening, or it may be hardened all the way through, known as through hardening, depending on the heating, holding, and cooling process that the metal goes through.

Through hardening makes the materials stronger, more durable, tougher, and more resistant to wear. This is important for metals that are expected to undergo a lot of friction, such as gears and bearings.

Key Benefit Three: Improving Strength and Toughness

Key Benefit Three- Improving Strength and Toughness

By altering the rate of cooling, we can alter the strength and toughness of a metal. When metal is cooled rapidly, it will form hard but brittle properties. Alternatively, when metal is cooled slowly, a softer tougher material is formed.

The process of hardening will create strength but cause brittleness; therefore, the metal may require a secondary process of tempering to reduce the brittleness and create toughness.

We will discuss these methods and more below. Improving the strength and toughness of metal is important to enabling them to be able to withstand heavy loads and impact, especially important in metal that is to be used for structural applications.

Key Benefit Four: Improving Magnetic Properties

Heat treatment can also alter the magnetic properties of metal. This is achieved by controlling the rate at which the metal is both heated and cooled during the heat treatment process.

This idea is essential in items such as electronics, speakers, motors, and other components where magnets are used. Heat-treated metals can also be used in magnetic memory applications, such as in computer hard drives and other data storage devices.  

Types of Heat Treatment and Their Purposes in Machining

  • Hardening
  • Tempering
  • Annealing
  • Normalizing

There are four main types of heat treatment, each serving a different purpose and resulting in a different desired outcome. The four types of heat treatment are as follows hardening, tempering, annealing, and normalizing.



The process of hardening involves heating the metal to a temperature that is above its critical point. The critical point of a metal is the temperature at which the metal will begin to experience physical changes.

Upon being heated in the hardening process, the metal is then cooled rapidly. This type of heat treatment is used to harden or provide strength to the metal; however, a drawback of such a method is that it can cause the metal to become brittle.

That takes us to our next type of heat treatment, tempering.


Tempering is often used after hardening to reduce the brittleness of the metal important in preventing the metal from fracturing or cracking. During tempering, the metal is heated to a point below its critical point and held there to allow uniformity before being cooled slowly.

The lower temperature reduces the brittleness whilst retaining the hardness of the metal. Therefore, it is no surprise that the tempering process often follows the hardening process. 


The annealing process is the opposite of the hardening process. It actually decreases the hardness of the metal whilst increasing the ductility. Ultimately making it easier to work with the metal.

This is achieved by heating the metal above its critical point and then cooling it slowly in oil or water.

This slow cooling process results in a softer, more malleable material compared to the same metal cooled rapidly. This is especially important in more complex objects, such as parts for automobiles.



Normalizing is a process similar to annealing; however, cooling is achieved differently. Like annealing, the metal is heated to a temperature above its critical point; however, rather than being cooled in oil or water like the annealing process, the metal is cooled slowly in still air.

Cooling this way produces a more uniform structure and hardness throughout the metal. This is important in applications where high stability of the metal is required, such as machining applications.

What Metals Are Suitable for Heat Treating?

What Metals Are Suitable for Heat Treating

Although there are clear benefits of heat treatment for metals, not all metals are suitable for the process. The metals suitable to undergo heat treatment include the obvious choice of steel along with aluminum, magnesium, titanium, and copper.

Heat treatment can increase the strength of copper, making it harder and more wear-resistant. Strength and durability are some of the main benefits of heat treatment and can also be improved in aluminum and magnesium.

Heat treatment in titanium can be used to improve corrosion resistance, another main benefit of the heat treatment process.

CNC Machining at Kemal | Low Volume Manufacturing & Rapid Prototyping

CNC Machining at Kemal - Low Volume Manufacturing & Rapid Prototyping

CNC machining is the most common manufacturing technique used today. CNC ( computer numerical control) machining is a manufacturing process in which pre-programmed computer software dictates the movement of factory machinery and tools.

CNC machining has been around for a long time; however, it has only recently become popular for low-volume manufacturing and rapid prototyping. CNC offers a huge advantage over traditional methods.

This is its ability to create challenging and complex shapes with ease. Such is especially useful for rapid prototyping as designers can quickly create a prototype that closely matches the final product.

At Kemal, we use this technology for low-volume manufacturing and rapid prototyping, making it possible to turn product ideas into a reality quickly and affordably.

FAQs – Heat Treatment of Metals

One of the main benefits of heat treatment of metals is improved strength, so yes, in many cases, heat treatment does make metals stronger.

However, this is not always the case. In some instances, heat treatment actually makes the metals weaker.

During the heat treatment of metals, the metals undergo heating and then cooling in order to alter the properties of the metal to a desired outcome.

This is achieved by physically changing the internal structure of the metal. Different methods are used depending on the outcome you desire.

For example, there is the hardening metal, where the metal is heated to a high temperature and then rapidly cooled, giving the metal strength, and then there is the tempering method, where metal is heated to a low temperature and cooled slowly making the metal less brittle.

This depends on the type of steel you are working with. Every type has its own upper and lower limit in regard to its toughness.

The temperature at which a steel’s toughness drops refers to the ‘Ductile to Brittle Transition Temperature.’ This is usually around 75°C but will differ depending on the type of steel you are working with.

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