What Types of Steel Can You Water Quench?
In this episode of Metallurgy Minute, Metallurgical Engineer Rob Simons talks water quenching and the magic carbon limit.Watch Now
Water quenching is an umbrella term used to describe a heat treatment process in which a heated metal component is rapidly cooled by immersing it in a water-based quenchant. There are four different types of water-based quenching media: caustic, brine, water, and polymer.
Caustic quenchants, also known as alkaline quenchants, are water-based solutions that contain a high concentration of sodium hydroxide or other alkalis. These quenchants are often used for materials that are difficult to quench in water alone, such as stainless steel or high carbon steels, because they have a faster cooling rate than water alone.
Brine quenchants are water-based solutions that contain a high concentration of salt. They are used for materials that require a slower cooling rate than water, such as low-carbon steels, but a faster cooling rate than oil quenching.
Water quenchants are pure water, which are often used for materials that can be cooled rapidly without risk of cracking or distortion, such as low-carbon steels.
Polymer quenchants are water-based solutions that contain a high concentration of polymers, such as polyethylene glycol or glycol. They are used for materials that require a slower cooling rate than water, such as aluminum alloys, but a faster cooling rate than oil quenching.
It is important to select the appropriate quenchant for a particular material and application to achieve the desired properties and prevent cracking or distortion of the material. At Paulo, we specialize in quenching steel using our Batch Integral Quench Furnace and Continuous Belt Furnace.
Water quenching is the most severe form of quenching available and not all steels are suited for this process due to cracking risk. Steel with more than .3% carbon can’t be water quenched because it can potentially crack during this process. Materials under .3% are best for water quenching. Metallurgical Engineer Rob Simons refers to this as the “magic carbon level.”
Because of the severity of water quenching, part geometry is an important consideration when determining if your parts are suited for this process. Certain part geometries are more prone to cracking and distortion. Fasteners, for example, can never be caustic quenched because the threads will not endure. The thread would be completely stripped away by the caustic solution.