Ring compression test for high strength steel at high reduction in height under dry condition

Abstract

Cold forging of automotive parts in high strength steel causes high pressure on the die. The high pressure or heavy load reduces a die life and accuracy of the forged parts, so prediction of a more accurate load helps us to design optimum die dimensions in the process. In this report, the more precise frictional coefficient was measured by a ring compression test to predict the more accurate load in cold upsetting of high strength steel. The experimental results indicated a frictional coefficient μ of about 0.19 within height reduction less than 20% under a dry condition. However, when the reduction in height exceeds 20%, the results deviate from the calibration curve assumed to be constant μ = 0.19. This means that the friction changing during compression. Slight adhesion was observed on the die surface, which must directly increase the frictional coefficient. The calibration curve was modified considering the change in friction during compression. Using the modified calibration curves, the experimental results are exactly plotted on the calibration curve which is drawn by changing μ from 0.19 to 0.25 at the reduction in height of 20%. This increasing frictional coefficient was helpful to estimate the accurate load when the rod of high strength steel is upset at high reduction under a dry condition.