Drilling in heat resistant cast stainless steel DIN 1.4848 for turbocharger housings
Pages 132-140
Modern turbochargers are important components to reduce the gasoline consumption on actual and future engines. The reduction of the cubic capacity (downsizing) of an engine with a simultaneous increasing power, reduced gasoline consumption and asignificant decrease of COoutput is only possible by using modern turbocharger tech-nology and fuel injection systems. The temperature in the housings will reach ca. 1050°C and it is necessary to use austenitic cast steel like 1.4848 for the housings. Drilling and threading are quite difficult technologies in this material.The experiment conducted by the authors showed, that for the machining of heat resistant cast stainless steel 1.4848 totally different drill designs are recommended from the precision tool manufactures. For a reduced or smaller axial force, cutting torque and a slower increase of the tool wear with an indication of longer tool life the following geometries does have positive aspects: a concave or straight cutting edge with a small cutting edge radius provides decrease in process parameters and a longer tool life. A reduction of the helix angle in combination with a straight nearly sharp cutting edge (small radius) provides also good results. Convex main cutting edges and high cutting edge radii or strong facets delivers higher forces and cutting torques in combination with a stronger corner edge wear. For a stabilization of the cutting corner edge, this part of the drill should be slightly rounded or produced with a small facet. A small land of the drill in combination with a step grinding gives advantages in comparison to wider lands with a continuous transition, due to reduced friction and a lower tendency of cold welding or build up edge.
DOI: 10.22227/1997-0935.2013.11.132-140
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