SOME ASPECTS OF COLD EXTRUSION OF FREE CUTTING STEEL WITH PREFORM GEOMETRY.

In forming, it is difficult to achieve very close tolerances and undercuts in the product. Under such cases, machining becomes indispensible. Free cutting steels are known for easy machinability due to the presence of sulfur and phosphorous resulting in discontinuous chips. Most of the cold extruded steels other than free cutting steel generate continuous chips and attendent problems. If the free cutting steels are cold extruded to an intermittent shape, the advantages of forming and discontinuous chips can be retained while machining the part of final accuracy. The inclusions responsible for easy machining pose difficulties during cold working because, they are vulnerable agents for crack formations. The present work enumerates the shaping of billet geometry to avoid cracks during cold forward solid extrusion. The forces of extrusion are analysed at various reductions accounting for adiabatic heating. Micrographic inspections reveal the crack free extrudes. The influence of elongations of inclusions reflecting on subsequent machining forces have been studied.