EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Harder grades and better surface quality in longer rolling campaigns are the todays challenges in the hot rolling finishing mill. One of the key factors to achieve these objectives is the application of roll gap lubrication. It is essential to have a high performance, robust and highly efficient industrial lubrication installation. During the last years, also the economic aspect has gained importance. In view of the application of efficient low cost lubricants, new environmentalfriendly and waste oils from other processes have been characterised in hot rolling conditions at the CRM laboratories. In a first phase, the lubricant is characterised using different chemical lubricant analysis, wettability trials, friction analysis and plate out trials combined with oil droplet analysis. The plate out simulator at CRM is able to spray an emulsion on a moving substrate (work roll simulation) with different spraying parameters. The effective oil quantity on the surface is measured by a fluorence technique to quantify the small oil film. In a second phase, the lubricants and application methods are tested on the continuous hot rolling pilot line. A stable flat rolling process is simulated on a 3 mm thick strip with a maximum width of 200 mm at a speed up to 0.5 m/s. By this almost similar roll/strip contact times are obtained as in stands one and two of an industrial finishing mill. A specific task in the evaluation has been the development of a dedicated multiple oil injection installation to apply up subsequently to four oils directly on the work roll cylinders. This allows a very quick change of oil composition without changing any other rolling or spraying parameter during the hot continuous rolling trial. In order to have the same industrial emulsion conditions, a lubrication header configuration of an industrial hot strip finishing mill is used. This allows to do a first evaluation of the lubricant and lubricant application practice in terms of their efficiency. Afterwards, the best practice technique is transferred to the industrial hot strip mill. Different green oils and waste oils have been compared to commercial hot rolling lubricants applied at different facilities. The results were very supprising: although a much lower cost (up to 5 times), green oils were with the most efficient oils in hot rolling operations. Savings up to 150 keuro/year could be made in industrial plants by applying these oils.