Method for Determination of the Friction Coefficient during Cold Rolling of Extra Thin Sheets

The method is aimed at comparing the lubricating capacity of different emulsions. The purpose of the work is to evaluate the possibility of using a universal friction machine, type MMW-1A, to determine the value of the friction coefficient in the cold rolling of very thin strips of carbon steel. The article analyzes the research related to the methods of measuring the friction coefficient in lengthwise rolling. The methodology of experiment determination of friction coefficient value between the material of RCM-1250 reversing mill rolls (steel of working rolls-analog of 60S2HFA steel) and the sample of annealed strip, 0.224-mm thick, made of TS-435 steel grade (analog of 08ps steel, GOST 1050) has been developed. The selected friction conditions are semi-fluid friction. The experiment applied the emulsion, based on the lubricating-cooling liquid, such as Quaker 2185, and used an RCM-125 reversing mill. Two types of ring-shaped samples made of roll material were used in the experiment with wall thicknesses of S = 4 mm and S = 2 mm. The results of the experiments showed that the use of the ring-shaped sample with S = 4 mm is more reasonable from the point of view of stability of the created friction conditions. The recommended average value of friction coefficient between the above materials of rolls and strip was determined: f(cf) = 0.038. In the course of the experiment the values of the friction coefficient fluctuated within the boundaries, from the minimum of f(min) = 0.012, to the maximum of f(max) = 0.048. In general, these experimental results are correlated with reference data on the value of the friction coefficient for this type of rolling and the results of other experiments described in the literature, conducted under similar friction conditions. Proceeding from this, it is possible to draw a conclusion that estimation of the lubricating capacity of various lubricating-cooling liquids, application of universal friction machines of the design described in the article is expedient.