Microstructural Evolution of Emulsion-Lubricated Cold-Rolled Steel Interface

The complex interaction between emulsion lubrication, heavy-load rolling, interfacial friction, and interfacial microstructural evolution is an urgent scientific problem that needs to be explored for emulsion-lubricated rolling. In this study, the evolution of the surface and interface microstructures of AISI-1045 steel subjected to two types of emulsion lubrication rolling is investigated. The influence of the differences between the properties of the emulsions (wettability, homogeneity, and tribological properties) on the surface and interface of the rolled material is analyzed. The results show that the differences between the emulsion properties produce different rolling forces and surface qualities. The rolling force and surface roughness of E-H (Emulsion H) having poor emulsion properties increase by 9.3% and 83.3%, respectively, compared with those of E-L (Emulsion L) having superior properties. The excessive rolling force exerted when applying E-H-emulsion-lubricated rolling results in a gradient distribution structure of the material surface: a layer of fine grains, layer of finely deformed grains, and layer of large grains with a small amount of deformation. Many defects (stacking dislocations, dislocation unit structures, and twinning boundaries) are distributed in the fine-grained and finely deformed-grain layers. The dense distribution of dislocations in the crystals leads to further rotation of the texture toward the Brass{011}⟨211⟩ and S3{123}⟨634⟩ texture components. Consequently, the variability in the emulsion properties significantly affects the surface and interfacial structural composition of the rolled material. Thus, material properties are affected. This study provides methods for optimizing the cold-rolling lubrication process.