Detection of errors in case hardening processes brought on by cooling lubricant residues

Life cycle of case hardened steel work pieces depends on the quality of hardening. A large influencing factor on the quality of hardening is the cleanliness of the work pieces. In manufacturing a large amount of auxiliary materials such as cooling lubricants and drawing compounds are used to ensure correct execution of cutting and forming processes. Especially the residues of cooling lubricants are carried into following processes on the surfaces of the machined parts. Stable and controlled conditions cannot be guaranteed for these subsequent processes as the residues' influence on the process performance is known insufficiently, leading to a high uncertainty and consequently high expense factor. Therefore, information is needed about the type and amount of contamination. In practice the influence of these cooling lubricants on case hardening steels is a well-known phenomenon but correlation of the residue volume and resulting hardness are not known. A short overview of the techniques to detect cooling lubricant residues will be given in this paper and a method to detect the influence of the residues on the hardening process of case hardening steels will be shown. An example will be given for case hardening steel 16MnCr5 (1.7131). The medium of contamination is ARAL SAROL 470 EP.