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°C. 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.