Behavior of Oxide-layer Adhered on Tool Surface when Machining Ca-Deoxidized Steel

Machining of Ca-Si deoxidized, Fe-Si deoxidized and conventionally deoxidized steels was investigated in order to reveal the effect and mechanism of the tool surface layer consistnig of oxides and sulfides in preventing tool wear. The tool surface layers were surveyed by the electron probe X-ray micro-analyzer, and the structural components of the layer were identified in this study. The following concludions were obtained : When machining Ca-Si deoxidized or Fe-Si deoxidized steels, the oxides and sulfides form layers on the tool surface, which avoid the direct contact of the work iron with the tool carbides, prevent the diffusion of the tool material. When cutting Ca-Si deoxidized steels, a semitransparent layer forms preferably on carbide tools which contain TiC, and it consists of 2 to 3 CaO-Al₂O₃-SiO₂. In the case of Fe-Si deoxidized steels, an ashy-grey coloured layer forms preferably on ceramic tools and it consists of CaO, Al₂O₃, SiO₂ and MnS

Turning of BN free-machining steel

金沢大学理工研究域機械工学系This paper deals with the machinability of BN (Boron Nitride) free-machining steel in turning. Tested work materials were plane carbon steel JIS S45C and BN free-machining steel. The JIS S45C used as the standard. The tool wear in turning BN free-machining steel was smaller than that in turning standard steel. BN free-machining steel showed slightly lower cutting temperature and smaller cutting force to compare with standard steel at the tested cutting speeds. At the tool wear region of P grade carbide tool after turning BN free-machining steel at high cutting speed, Al and N were detected as a layer. It is thought that one of the main reasons of outstanding machinability of BN free-machining steel is the deposited layer containing Al and N acts as diffusion barrier at the tool-chip interface. In turning larger Al content BN added steel with higher Ti content cutting tool, the influence of BN addition on the tool wear reduction was more remarkable.[議事録

Machinability of pearlitic cast iron with Cubic Boron Nitride (CBN) cutting tools

In order to increase the accurate finishing productivity of pearlitic cast iron, face milling by CBN (Cubic Boron Nitride) cutting tools was studied. The main focus of the study is the machinability investigation of pearlitic cast iron with CBN cutting tools by studying the relationships among machining conditions such as feed rate, cutting speed as well as CBN cutting tool type, tool wear, workpiece surface quality, cutting forces, and cutting temperature. In addition, an emphasis is put on the effect of Al additive in pearlitic cast iron on its machinability and tool wear characteristics. High-speed milling experiments with CBN cutting tools were conducted on a vertical machining center under different machining conditions. The results obtained provide a useful understanding of milling performance by CBN cutting tools