Tempering brittleness of heat treatment

There is a temper brittleness at 200 ~ 350 degrees, which is irreversible.

The second temper brittleness occurs at 400 ~ 650 degrees.

Heat treatment refers to the metal hot working process in which materials are heated, insulated and cooled in solid state to obtain the expected structure and properties.

Tempering brittleness refers to the phenomenon that the toughness of quenched steel decreases after tempering. During tempering, with the increase of tempering temperature, the hardness of quenched steel decreases and the toughness increases, but there are two valleys in the curve of the relationship between tempering temperature and impact toughness of many steels, one is between 200~400℃ and the other is between 450~650℃. With the increase of tempering temperature, impact toughness decreases. Tempering brittleness can be divided into the first category and the second category.