Ultrafine ferrite in low carbon steel

Ultrafine (1μm) equiaxed ferrite grains in steel strip were produced using a simple new thermomechanical process. Strips were reheated to produce a coarse austenite grain size, then rolled in a single pass at or just above the A r3 . The ultrafine grains formed in the surface regions of the strip. Coarser ferrite grains (5-10μm) and carbides were produced in the core of the strip. Refinement of the grains was attributed to strain induced transformation from austenite to ferrite.