The Influence of Die Temperature and Hardness on the Wear of No. 5. Die Steel Under Hot Forging Conditions

Abstract

A study has been made of the influence of die hardness and temperature on the wear of No. 5. Die Steel, under hot forging conditions. Tests were performed under controlled conditions in an automated experimental press, the material, in the form of flat die inserts, being worn by the regular upsetting of cylinders of hot stock between the insert faces, and the die temperature being simulated by means of heaters within the main die blocks. The wear so produced was in the form of an annulus and the volume of metal removed was computed from data obtained by tracing across four diameters of the worn insert using a surface measuring instrument. All inserts were also sectioned, applying a modification of conventional taper sectioning techniques, and investigated metallographically, in order that the wear might be related to the structural condition of the near surface regions of the material. It was found that abrasion was largely responsible for the total amount of wear. Wear increased with increased temperature mainly as a result of the consequent decrease in strength and hardness of the material, but became disproportionately severe once the surface temperature exceeded Ac1. Wear decreased with increased hardness in a discontinuous manner, the discontinuities being related to the structural state of the steel. An acicular structure containing well dispersed carbide particles was found to be particularly wear resistant.