Temper Embrittlement
Temper brittleness is the loss of toughness in alloyed steels at certain tempering temperatures, caused by segregation of accompanying elements at grain boundaries.
Physical-Chemical Mechanism of Action
Temper brittleness arises from the segregation (variation in additive distribution) of accompanying elements such as silicon or carbon at grain boundaries of the steel during the melting and cooling process. These variations lead to local stresses, which at certain tempering temperatures cause brittleness and loss of toughness.
Metallurgical Relevance & Risks in Welding
Temper brittleness can cause hot cracking and deformation of the weld. These cracks may not always be visually detectable, leading to serious safety issues in service. Additionally, brittleness can reduce the service life of the component.
Workshop Practice & Instructions
To avoid temper brittleness, it is important to precisely control the melting and cooling process. This includes maintaining correct tempering temperatures and using stable alloyed steels with low segregation tendency. For specific applications, a special cooling curve may be prescribed to minimize brittleness.