Steel is considered among some of the strongest materials on earth, but some processes can make it even stronger. Quenching and tempering is one way to increase the strength and durability of steel for many different types of industrial applications. This quick guide will provide information on steel treatment methods and how they enhance steel for many purposes.
How Does The Quench Temper Process Work?
The iron-based alloys are heated, rapidly cooled, and then reheated during this process. The grain or molecular structures are altered if you apply heat above a certain point to steel. Following this, the steel is quenched using varying speeds. This is done to create the desired molecular structure of the grain. You can think of this sort of like steaming green beans and then following that with cold water. This stops the beans from further cooking from residual heat.
After the steel is quenched in water, it will be as hard as it possibly can be. However, at this point in the process, the material is also brittle. It is subject to cracking. The solution to this is to then temper the metal with further heat. Heat is applied until the metal becomes ductile.
More on Quenching
Let’s get into a little more detail concerning the quenching process. Once the metal has been heated, it will need to cool quickly. During the quenching portion of the process, grains within the material will start to transform. Some of the grains that will change include martensite, ferrite, pearlite, and cementite. The development of the structures of the grains can be manipulated by how quickly the material is cooled.
There are different options for cooling. Salt water solutions are considered to be the fastest but also the most severe. Other options include fresh water, oil, forced air, and polymer. It should be noted that the fastest isn’t always the best, however. Fast quenching can often result in cracking. Freshwater quenching is often recommended. Let’s take a closer look at the different types of quenching available and their benefits.
Freshwater Quenching – This provides uniform cooling if the water maintains a consistent temp and is evenly applied.
Polymer Quenching – This is a water-based process. This is considered less severe than water or salt water quenching. This process can minimize distortion.
Oil Quenching – This process provides a slower cooling rate. This is often used for alloyed steel. Alloyed steels are more susceptible to cracking when severe methods are used. This is a good method to use when you want to reduce the amount of distortion.
Brining – This is also often called a saltwater quench. This is considered a severe form of quenching that could result in cracking.
Tempering
Once the steel is quenched, the metal is hard but brittle. Another step must be taken, and that is tempering. Tempering reduces some of the hardness but increases the ductility. During tempering, the steel is heated for a certain period of time between 400 degrees F and 1,105 degrees F. If a greater degree of ductility is needed, higher temps can be used.