Metalworking fluids play a significant role in machining operations and have a substantial impact on tool life, shop productivity, and the quality of the workpiece. The results presented in this article show the influence of the properties of the metalworking fluids and the supply system on the workpiece quality in cutting and grinding processes. Chemical, physical, and tribological aspects have an impact on the properties of the generated surface. For the assessment of cooling effectiveness, a special test rig for the investigation of the coolant supply system in a grinding process is presented. Another approach to investigate the effectiveness and efficiency of the cooling and lubrication system during grinding is to monitor the temperatures and forces by a wheel-based measurement using telemetric data transmission. A further important aspect of water-soluble metalworking fluids is the influence of microbial effects on working results in machining. Microbial degradation leads to drastic changes in the physical and chemical properties of the metalworking fluid during service life. Besides the demands on the efficiency and economy of cutting processes, their environmental friendliness becomes a crucial issue itself. Therefore, an example for a holistic view on the environmental impacts of machining processes and the application of metalworking fluids is given.

No abstract

The hardness and fatigue strength achieved by strain hardening are normally noticeable lower than those attained by thermal or thermochemical heat treatments. Strain or deformation induced martensitic transformation of residual austenite can increase the strength achieved by mechanical surface hardening processes considerably. In this paper, an approach is presented where workpieces with a high content of metastable austenite are used for hardening the surface layer. The microstructure has to be sufficiently stable, in order to ensure that the material can be machined without being changed by strain induced transformation of the residual austenite. After machining, high Hertzian contact stresses are introduced by deep rolling, so that a strain induced martensitic transformation of the residual austenite takes place. At the same time deep rolling produces the surface finish of the part. By this method, a surface hardening without a heat treatment process within the production line can be realized. A conceivable use of this method could be the production of bearings or guideways.

Residual stress induced in cutting processes substantially impacts adversely on functional part performance and distortion, especially when thin-walled workpieces are machined. For this reason, basic research focuses on the correlation between a specific high-speed turning configuration and the occurrence of residual stress and the amount of resulting distortion. The presented experiments in high-speed turning of thin-walled AISI 52100 (100Cr6) steel workpieces show, that residual stress distribution in the surface layer moves toward compressive stress as cutting speed increases while feed and lower wall-thickness decrease. Indications were also, that increasing cutting speed leads to higher distortion. To evaluate residual stress potential in shape deviation, the so-called source forceF’sourcewas calculated by numerically integrating the residual stress depth profile.

KurzfassungSeit dem Jahr 2001 wird an der Stiftung Institut für Werkstofftechnik Bremen (IWT) ein neues endwärmebehandlungsfreies Verfahren zur Herstellung von randschichtgehärteten Stahlbauteilen erforscht. Bei diesem Verfahren wird die Randschichthärtung durch eine mechanisch induzierte martensitische Phasenumwandlung in die Fertigungslinie integriert. Neben einer deutlichen Verkürzung der Produktionsdauer wird die lokale Härtung von Funktionsflächen eines Bauteils ermöglicht. Zudem kommt es durch die Einsparung einer abschlieβenden Wärmebehandlung zu einer signifikanten Reduzierung des Energieverbrauchs und der damit verbundenen CO2-Emission.Um eine spannungs- bzw. dehnungsinduzierte martensitische Phasenumwandlung aufgrund von rein mechanischen Effekten zu ermöglichen, wird zunächst ein bei Raumtemperatur metastabiles austenitisches Gefüge hergestellt. Dieser Werkstoffzustand soll so stabil sein, dass eine spanende Bearbeitung keine ausgedehnte martensitische Phasenumwand-lung auslöst und das Werkstück somit noch “weich” bearbeitet werden kann. In einem anschlieβenden mechanischen Verfahren, wie z. B. einem Festwalzprozess, soll die auf die Werkstückoberfläche ausgeübte Pressung so weit gesteigert werden, dass die zur martensitischen Umwandlung des Austenits benötigte Spannung in der Bauteilrandzone erreicht wird.