Studies on Heat-Checking of Iron and Steel (3rd Report). Influence of Heating Time and Heating Temperature on Heat-Checking

Abstract

The sides of disk-like specimens made of 5%Cr-Mo-Si steel were repeatedly heated and cooled by using a high-frequency induction surface-hardening apparatus, and the influence of heating time and heating temperature on the formation of heat-checks on the sides was studied. The results were as follows: (1) The longer the heating time (t) and the higher the heating temperature (surface temperature θ), the more conspicuous the checks. This tendency is more apparent in the case of N(the number of thermal cycles)=1000 than N=100. (2) In the case of N=1000, the mean depth and the maximum depth of checks increase with increasing heating times and heating temperature, but the total number of checks reaches a maximum at t=2.5 sec (θ=850°) and decreases at t=3.0 sec (θ=910°). (3) The depth of checks at any heating time is distributed according to the exponential function, but in the case of t=3.0 sec the distribution is changed showing a lesser number of shallow checks. (4) With increasing heating time and heating temperature, the width of the checks on the cross-section of the specimen also increases.