Bainitic Step Structure
A microstructure consisting of needle-like ferrite and fine carbides formed via combined diffusion and shear mechanisms at intermediate temperatures. It offers an optimal balance of strength and ductility.
Bainite forms when you cool steel after welding or heating in a medium temperature range – sort of between pearlite and martensite formation. The structure is tough and stronger than ferrite/pearlite, but not as hard and brittle as martensite. In welding, this means: if you cool too fast, you'll get martensite and risk cracking. If you want bainite, you need to slow down the cooling rate, e.g., by preheating or letting it cool slowly. Exact temperatures depend on the material, but you can usually identify bainite by its fine, needle-like structure in a micrograph.