Temperature measurement when high speed machining hardened mould/die steel

When turning and face milling hardened (>30 HRC) mould/die steels, it is ne cessary to use conventional ceramic or polycrystalline cubic boron nitride (PCBN) tool materials. The use of high speed steel and cemented tungsten ca rbide (WC) tooling for this application is precluded due to their relativel y low hot hardness values. In recent years, however, the mould and die indu stry has begun to utilise solid WC ball nose end mills for the high speed m achining (HSM) of hardened steel cavities. Economic tool lives have been re ported at high rotational speeds/feed rates. The paper details the use of 6 mm diameter solid, TiCN coated WC ball nose end mills for the HSM of a hot work tool steel, AISI H13, hardened to 52 HR C. Tests were performed on a Matsuura 20 000 rpm high speed machining centr e and temperatures were measured using thermocouple and infrared techniques . Recorded tool/workpiece interface and chip temperatures were relatively l ow (200-400 degrees C) and increased with higher cutting speed, when using worn rather than new tools and with the workpiece inclined at 60 degrees to simulate finishing operations on the side of die cavities. (C) 1999 Elsevi er Science S.A. All rights reserved.