Development of new tribo-meter for forging

A lubricant plays very important part in forging to improve both forgiability and die life. Ring compression test has been well used for the evaluation of forging lubricants as a standard tribo-meter. Ring compression test is the only method to obtain a friction factor, however the surface expansion ratio of Ring compression test is only between 2 and 4. While the surface expansion ratios of general forging parts such as flange bolt and constant velocity joint components are more than 15. So the development of new tribo-meter which can evaluate in sever forging condition has been desired. We have developed the new three tribo-meters named Spike test, Taper cup test and Flange header test. Spike test is based on combination of forward extrusion and upsetting. It can evaluate the forging and eject behaviour, and covers the surface expansion ratio between 7 and 13, which is medium forging condition. Taper cup test is based on a backward forging using taper punch. It can evaluate the forging behaviour and covers the surface expansion ration from 15 to 50. It can evaluate the lubrication limit and obtain friction factor at the same time using FE analysis. Flange header test is a kind of header forging method. It can evaluate the forging and eject behaviour and covers the surface expansion behaviour up to 19. In this test, the side surface of the specimen is evaluated. So it is suitable for the evaluation of wire coating lubricant. In this paper, the theory and feature of tribo-meters have been introduced. In addition, evaluation results of representative lubricants were also reported.