Year

2021

Degree Name

Doctor of Philosophy

Department

School of School of Mechanical, Materials, Mechatronic and Biomedical Engineering

Abstract

Lubricants are essential to energy efficiency of cold plate rolling processes, as well as to surface quality and downstream processing of the rolled products. High performing rolling lubrication requires a balanced degree of ‘stability’ for a good dispersion and consistent oil supply to the contact area and ‘instability’ for plate out of oil components from lubricants on the surface to create an oil-rich film upstream of the rolls’ bite zone. Vegetable oil-in-water (VO/W) emulsions are the preferred lubricants for boundary regime cold rolling lubrication in which the dispersed surface-active and polar vegetable oil components e.g. triglycerides or free fatty acids) plate out on the surface upstream of the rolls’ bite zone to provide required wet minimum quantity lubrication (MQL) support.

However, VO/W emulsions show several drawbacks due to high polarity of vegetable oil components including their low coalescence and creaming stability which leads to phase separation, and their tendency to oxidise and leave varnish-like residue on the surface which reduces the downstream processing capability of rolled products e.g. painting and annealing capacity, indicating poor clean-ability of polar tribo-films from metal surfaces. Besides, cold rolling lubrication by using additive-free emulsions results in adhesion and material transfer, lowering the surface quality of the rolled work-pieces. This is particularly an issue in rolling of ‘sticky’ metals such as aluminium, stainless steel, Ti, and Zr alloys, commonly performed in industrial applications.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.