Surface roughness, hardness and microstructure characterization of cold rolled sheet

Abstract

Cold rolling process is the oldest deformation processes in metal-forming industry. Due to the ever increasing demand for high quality aluminum strips and foils, rolling lubrication and rolling oil are playing an important role in attaining the best possible rolled surface during the aluminum and steel cold rolling process. Surface roughness control is one of the most important subjects during producing steel and aluminium strips. This research work is mainly pointed towards investigation of improvement in the surface features of cold rolling strips by using suitable lubricants. Thus, the effects of oil film on the rolled surface, including surface roughness, variation in rolling force and thickness reduction and rolled surface morphology, mechanical properties, etc, were investigated during cold rolling of aluminum and steel strips. Various lubricants with different viscosities were used for the study. The performance of water-based and mineral based lubricant is compared with rolling done without lubrication. It has been found from our work that more the viscosity of lubricant better is the quality of surface obtained after cold rolling. Moreover, use of nanolubricants is rarely found in the literature for cold rolling process. Keeping in mind, the enhanced tribological and thermal characteristics of the selected nanoparticles, an attempt is also made to explore the impact of nanoparticles addition in the lubricant in the outcome of rolling process. Also, a theoretical analysis on strip surface roughness is carried out where experimental data are validated with an existing roughness model. A great number of statistical results show that experimental data is in excellent agreement with the adopted model and the relative deviation on roughness between calculated and measured is very less. From the study it is also revealed that lubrication has significant impact on rolling outcome and surface features of rolled strips, including strip reduction and spreading of strip, amount surface transfer layer and surface roughness transfer and hardness of the rolled strips.