Eco-friendly lubricants for improving performance and environmental impact in cold rolling

Abstract

Cold rolling of strips is a well-known metal forming process, carried out below the material recrystallization temperature to improve the surface finish and the geometrical tolerance of the rolled strip. Friction plays a fundamental role in the rolling process and, even in case of a favorable roll bite condition, a non-optimal lubrication causes the rapid wear of the work rolls and high energy consumptions. Most of the currently used lubricants are based on synthetic or semi-synthetic formulations. However, the increase in the cost of petroleum-based products and the tightening of the environmental regulations is pushing the scientific and industrial community to search for more sustainable alternatives. Recently, the demand for green lubricants capable of matching non-toxicity, high biodegradability while keeping good lubricating performance is becoming of outmost importance. In the present work, the environmental impact and the lubricating performance of two innovative natural-based lubricants have been assessed using laboratory tests. An animal-based (AB) and a vegetable-based (VB) formulation were investigated and the results compared with a commercial mineral-based (MB) one. As concerns the environmental impact, emulsions at 2% oil concentration were chemically treated using a powder composed of bentonite and activated carbons and the Chemical Oxygen Demand (COD) and total Surfactants in the aqueous phase were evaluated. The lubricating performance of the emulsions at 2% oil concentration was assessed by conducting tribological tests using the Falex tribometer in accordance with the Standard. The experimental comparison revealed that it is not only feasible but also convenient in terms of both environmental impact and performance to replace the mineral-based lubricant.