Achieving high surface brightness and high processability necessitates the development of a lubricant with suitable extreme-pressure (EP) agents to prevent seizures and heat scratches on strip surfaces. Despite its significance, a comprehensive investigation of the mechanisms by which EP agents function within lubricant oils during cold rolling remains insufficient. In this study, we aim to elucidate the effect of EP agents with varying molecular structures on oil film formation, utilizing micro-Fourier transform infrared spectroscopy (micro-FTIR) in conjunction with ball-on-disk testing. The findings reveal that the molecular structure of EP agents significantly impacts oil film formation, attributable to their condensation behaviors at the entry side of the Hertzian contact area and their distinct viscosity characteristics.

The effects of die temperature, die gap, plunger speed and molten metal temperature on the flow length of A1070 pure aluminum in a thin die gap were investigated. The die gaps were 0.5, 0.8 and 1.0 mm. The plunger speeds were 0.2, 0.4, 0.6 and 0.8 m/s. The die temperatures were 30, 70, 110 and 150 °C.The molten metal temperatures were 680, 730 and 780 °C. When the die gap was 0.5 mm, the flow length was largest when the die temperature was 30 °C and the plunger speed was 0.2 m/s, which is contrary to conventional expectations. However, when the die gap was 1.0 mm, the flow length increased as the die temperature and plunger speed increased, which aligns with previously reported results. It became clear that when the die gap was 0.5 mm, the effects of die temperature and plunger speed on flow length were opposite to those for a die gap wider than 0.5 mm. The cause of this phenomenon is discussed in terms of the adhesion and peeling of the solidification layer.