Variation of the friction conditions in cold ring compression tests of medium carbon steel

Lubrication and friction conditions vary with deformation during metal forming processes.Significant macro-variations can be observed when a threshold of deformation is reached.This study shows that during the cold compression processing of#45(AISI 1045)steel rings,the magnitude of friction and surface roughness(Ra)changes significantly upon reaching a 45%reduction in ring height.For example,the Ra of compressed ring specimens increased by approximately 55%immediately before and after reaching this threshold,compared to an 18% or 25%variation over a 35%-45%or a 45%-55%reduction in height,respectively.The ring compression test conducted by this study indicates that the Coulomb friction coefficient and Tresca friction factor mare 0.105 and 0.22,respectively,when the reduction in height is less than 45%;and 0.11 and 0.24,respectively,when the reduction in height is greater than 45%.