Micro-temperature manipulation in cryogenic machining of low carbon steel

This paper presents an environmentally safe approach of micro-manipulation of cutting temperatures in machining AISI/SAE 1008 low carbon steel, a mate rial widely recognized as a difficult-to-machine material from the viewpoin t of chip control. A temperature distribution in different functional cutti ng zones is prescribed so that the material properties in each sub-zone can be altered to meet the machinability requirements. Liquid nitrogen is sele ctively applied to the chip and the tool rake face in well-controlled jet. Finite element analysis shows that this cooling approach can bring the chip temperature down to the embrittlement temperature for the material, -55 de greesC. Consequently, it expands the chip-breaking range of feed and cuttin g speed, with a reduced chip-tool interface temperature and increased tool life. This approach also minimizes the undesirable cooling effect to the sh ear zone to avoid the increase of material strength and cutting resistance. (C) 2001 Elsevier Science B.V. All rights reserved.