Evaluation for lubricity of lubricant by simulation testing machine developed newly in hot rolling

Recently, rolls made of high speed steel (HSS) which are superior to wear and abrasion resistance are used in many hot rolling mills. However, some troubles are occurred due to by the use of the HSS roll. To solve these problems, new lubricants are developed and the lubricities of them are estimated by using the two-disk testing machine or the pin-on-disk testing machine. But the evaluation obtained by these testing machines are different from one of the actual rolling processing. In order to evaluate the lubricity of lubricant in hot rolling, the simulation testing machine in the laboratory is modified from one for cold rolling. The evaluation performance of the simulation testing machine is investigated into using thc SPHC workpiece strip having dimensions of a width of 20 mm and a thickness of 2 mm at a hot rolling temperature of 1030 °C. From the experimental results, the lubricity of lubricant in hot rolling can be evaluated by the coefficient of friction measured. The effect of the additive on the coefficient of friction can be also confirmed. The obtained results are as follows: (1) When the mineral oil and one with oiliness additives are used as lubricants, the coefficient of friction increases rapidly with increasing rolling distance. (2) When the oils with the extreme-pressure additives are used, the coefficient of friction is steady over a rolling distance of 1000 mm.