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 material widely recognized as a difficult-to-machine material from the viewpoint of chip control. A temperature distribution in different functional cutting zones is prescribed so that the material properties in each sub-zone can be altered to meet the machinability requirements. Liquid nitrogen is selectively 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 degreesC. Consequently, it expands the chip-breaking range of feed and cutting speed, with a reduced chip-tool interface temperature and increased tool life. This approach also minimizes the undesirable cooling effect to the shear zone to avoid the increase of material strength and cutting resistance. (C) 2001 Elsevier Science B.V. All rights reserved.