Investigation of Quenchants Based on Sodium Aqueous Ionic Solutions

The mechanical properties of steel components are influenced by the microstructure, which is determined by the heat treatment cycle. In the quenching of the steel: water, oil, aqueous polymer solutions and aqueous salt solutions (brine) can be used as quenchants, which exhibit different characteristic cooling mechanisms. For example, when water is used as the cooling media, a stable vapor film is formed around the hot component resulting in nonuniformity of surface heat transfer during the cooling process, which is often responsible for distortion, and cracking. Using salt based on sodium (Na) as an additive forming a solution with distilled water was able to reduce or eliminate the vapor film, enhance the cooling rate and keep the heat flux in high values during the most part of the drop of the temperature that is better for a more homogeneous cooling. This work investigated the cooling performance of different aqueous salt solutions and quenching bath parameters (temperature and agitation). These analyses were made using cooling curves and heat flux to quantify the behavior and hardening power capacity of these aqueous salt solutions.

Keywords: heat treatment; quenching; salt solution;