Bainite Incubation Period
The incubation time of the bainite stage is the time elapsed between reaching the transformation temperature and the onset of bainitic nucleation in the TTT diagram. It determines the thermal window for isothermal bainitizing processes.
Physico-Chemical Mechanism of Action
The incubation time refers to the time during which the metal crystals change their structure and new phases such as bainite form. This process is temperature-dependent and depends on the chemical additives in the steel.
Metallurgical Relevance & Welding Risks
Too short an incubation time can cause incomplete bainite formation. This can lead to insufficient toughness and increased susceptibility to cracking. Conversely, too long an incubation time can lead to overformation of the microstructure and possibly a steel that is too soft.
Workshop Practice & Instructions
To ensure optimal bainite formation, it is important to maintain the transformation temperature precisely and control the incubation time according to the metallurgical properties of the steel. This can be achieved by using isothermal processes where temperature is kept constant.