There are several methods and techniques of quenching. Each significantly affects the final properties of your finished material. Let us cover common media for quenching metal and their trade-offs.
Water
Water is an aggressive quenching method since it offers the fastest cooling rate. Water’s rapid cooling mechanism is suitable when hardness and strength are non-negotiable. However, if proper procedures are not followed, it makes your metal susceptible to cracking and distortion.
Oil
Oil quenching is slower and more controlled than water quenching. Therefore, it is considered a safe method to prevent metal cracking and distortion
Oil quenching is ideal for striking a balance between hardness and strength. Due to the unique cooling process, it also gives your metal an excellent surface finish.
Air
Air is the most cost-effective medium of quenching. It involves heating your steel, then leaving it to cool slowly in the air. Since it is the slowest quenching medium, air minimizes the risk of cracks or thermal stress. This makes air ideal for steels that require exceptional toughness and moderate hardness.
Another form of air quenching uses compressed air. This method gives you more control of the temperature and cooling rate.
Brine
10% salt is added to water to form brine. This form of quenching is less common than water, air, or oil. But it offers a superior rate of cooling even faster than water.
It’s worth mentioning that brine is corrosive. Therefore, you must remove it from your steel by rinsing thoroughly once the job is complete.
Polymer-based quenchant
Polymers are not a medium of quenching but rather a quenching additive. Its cooling rate is slightly faster than oil but slower and less corrosive than water.
Polymers are inversely soluble in water. This means they separate from water at the start of a quench. Due to this effect, a polymer solution is created around your metal, enabling heat to exchange in a more controlled manner.
