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 (R_a) changes significantly upon reaching a 45% reduction in ring height. For example, the R_a 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 μ and Tresca friction factor m are 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%.