Comparison of machineability of new developed plastic mould steels

Polish ability, wear and corrosion resistance and a high tool life at high working temperatures are required by plastic mould users. On the other hand, toolmakers want steels with good attributes for machining, eroding, polishing or etching. New developed mould steels have to meet both demands. The target of Böhler Edelstahl in developing the tool steel M315 EXTRA was to reduce the machining costs at constant or better mechanical properties. The machining investigations at the end of the stepwise improvement are showing a reduction by half of the milling and drilling expenses. Corrosion resistance and best polish ability were the goals for M333 ISOPLAST, best wear resistance for M340 ISOPLAST. In the case of the powder metallurgic plastic mould steel M390 MICROCLEAN, a very high wear resistance and tool life time were intended. Additionally, a good machine ability is important. For this purpose, suitable cutting tools and parameter for the high speed cutting strategy were determined for these steels. The different behaviour in machining of the new plastic mould steels is described