Scanning tunnelling microscopy (STM) has been employed to investigate the fine surface structure of alloyed materials in the air surrounding, with the surface covered by a liquid layer to eliminate surface absorption and oxidation. The delicate substructure of lower bainitic ferrite plates of a silicon steel has been investigated. STM images demonstrate that the lower bainitic ferrite consists of four layers of substructure: a lower bainitic ferrite plate contains subplates, subplates contain subunits, and subunits contain ultra-subunits. An individual ultra-fubunit is of regular shape when a group of ultra-subunits are arranged in proper order and of a certain periodicity. Scanning tunnelling microscopy (STM) has been employed to investigate the fine surface structure by lower layer bainitic ferrite plates of a silicon steel has been investigated. STM images demonstrate that the lower bainitic ferrite consists of four layers of substructure: a lower bainitic ferrite plate contains subplates, subplates contain subunits, and subunits contain ultra-subunits. An individual ultra-fubunit is of regular shape when a group of ultra-subunits are arranged in proper order and of a certain periodicity.