Heat treatment optimization of through-hardening bearing steels

Abstract

Non-contact infrared thermometers, such as pyrometers, are excellent for monitoring surface temperatures of objects that are moving, difficult to reach or extremely hot without damaging the object. Pyrometers are also easy to handle and often less expensive than contact temperature sensors. If pyrometers are to be used in a greater extent at SKF when evaluating or creating new heat treatment recipes for large bearings, more data is needed. The purpose of the study was to evaluate the current heat treatment recipes with the help of a hand held pyrometer. Twelve inner rings and ten outer rings of a large spherical roller bearing made from the through hardening bearing steel 100CrMnMoSi8-4-6 were measured and the results were verified using thermocouples. The pyrometer measurements showed consistent heat-up and soaking times for inner and outer rings, respectively, and relatively small time differences compared to the thermocouple measurements. Soaking time between the inner and outer rings as well as between the different furnaces did, however, differ quite a lot. The author concludes that pyrometers can be used effectively to monitor the heat treatment and that the inner ring’s recipe should be changed to assure a more consistent heat treatment.