Abstract
In this paper, nano-TiO2lubricating fluid was chosen as an advanced rolling lubricant to investigate its effect on the hot rolled surface and metallographic structure of SS41 steel strips. The tribological performances of nano-TiO2 lubricating fluid were measured by a four-ball tribotester. The hot rolling experiments under different lubrication conditions were carried out by a four-high rolling mill. The surface morphology, oxide scales and metallographic structure after hot rolling were observed using a confocal laser scanning microscope and scanning electron microscope (SEM), respectively. The composition of surface attachments was analyzed with X-ray photoelectron spectroscopy (XPS). The results indicate that the nano-TiO2 lubricating fluid has a better tribological performance. The surface defects on the hot rolled surface could be decreased. The phase composition of the surface still appears as a mixture of ferrite and pearlite. The surface of steel strips is not micro-alloyed with titanium as predicted. Additionally, the grain size of rolled steel strips which were lubricated with the nano-TiO2lubricating fluid decreased by nearly 50%, compared with traditional lubricating fluid. Furthermore, it was found that the thickness of the oxide layers on the surface reduced, whilst the Rockwell hardness of the oxide layers was enhanced as nano-TiO2 lubricating fluid was applied.
Highlights
Due to their special physical and chemical properties [1], such as excellent diffusivity, chemical activity, and the ability to self-repair and film-form [2], nanoparticles have extensive applications in lubrication
Previous studies reported that nano-TiO2 has good friction-reducing, anti-wear, and cooling properties, so it can reduce the coefficient of friction and rolling force during the hot rolling process [16,17]
To provide an intuitive description of the surface quality of the hot-rolled steel strips, the surface morphology after hot rolling was characterized by a confocal laser scanning microscope (Olympus LEXTOLS 4000, Olympus, Japan) for 2D and 3D topography observation
Summary
Due to their special physical and chemical properties [1], such as excellent diffusivity, chemical activity, and the ability to self-repair and film-form [2], nanoparticles have extensive applications in lubrication Nanoparticles, such as molybdenum disulfide (MoS2) [3,4], silicon dioxide (SiO2) [3,5], titanium dioxide (TiO2) [6,7,8] and aluminum oxide (Al2O3) [8], can create the appropriate conditions for machining process [9]. The TiO2 nanoparticles used in nano-TiO2 lubricating fluid might have a chance to react with the surface steel during the hot rolling process and cause an inhomogeneity of the strips in structure and texture. The structural and textural inhomogeneity of steel strips would impact the processing properties and service performance of products [22]
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