Tempering with water or Polymer quenching

Standard – UNI 10990
Typical Materials – Quenching and tempering steels such as C40, C45, etc.
Achievable Metallurgical Characteristics – Surface hardness of XXXHB, with a sorbitic-bainitic microstructure.

The tempering process is typically applied to raw parts after forging to standardize the hardness and microstructure of the components.

The process involves heating the material to austenitizing temperatures, usually between 850-950°C, with holding times sufficient to ensure thorough heating of the sections. Austenitization is always followed by quenching through rapid cooling in water or polymer, bringing the material to microstructural stability temperatures. After quenching, tempering is performed at temperatures between 500-680°C, depending on the desired hardness levels.

Compared to oil quenching, water and polymer quenching provide a more severe quenching effect, making them especially suitable for less hardenable steels. This process can also be applied to higher alloy steels, such as 42CrMo4, 39NiCrMo3, etc., where excellent microstructural transformations can be achieved. However, for these steels, the higher quenching severity can cause cracking, so non-destructive testing is strongly recommended.