Change in Surface Profiles by Heat Treatment

The change in dimensions after heat treatment, in most cases, has been expressed by elongation or shrinkage obtained by measuring the distance between two sides of the specimen. In this paper, change in dimensions and change in profiles on sections and cubic surfaces after heat treatment by oil cooling, air cooling, marquenching, etc. were studied by using micrometer and surface roughness gauge. Three kinds of tool steels (SKS 2, SKD 11, and SKS 31+Mo in JIS) were selected and worked into rectangular parallelopipeds of 150×45×22mm for test pieces. The results obtained were as follows. (1) The surface profile of each face changed in three dimensions. For example, after SKS 2 was oil cooled, two corrugated ranges of mountains appeared in one direction and only one range in the perpendicular direction on 150×22mm face. However, on 150×45 face, there appeared V shaped corrugations in one direction and one range of mountains in the perpendicular direction. (2) Change in dimensions was the largest in SKS 2, and next in order were SKS+Mo and SKD 11. (3) SKS 2 showed the best results among the test pieces on which profiles were symmetrically distorted. The surface profiles were more accurately measured with roughness gauge than micrometer.