CV黒鉛鋳鉄と各種切削工具との反応性

抄録

  High efficiency machining methods are required for compacted vermicular graphite cast iron (FCV) to reduce production costs. For this reason, we have been conducting basic research on cutting tools for realizing high efficiency machining of FCV.
  In this study, tests were carried out on reactions between cast iron and various tools at high temperature (1403K) at which the state of the tool cutting edge in high speed machining can be reproduced. Three types of cast iron were used as samples; FCV, gray cast iron (FC), and ductile cast iron (FCD). The tools used were Ti(C, N)-Al₂O₃3 coated CVDcemented carbide tool (CVD), Al₂O₃-Ti(C, N) ceramics tool (CER), and TiC binder cBN tool (cBN). TiC and Al₂O₃ sintered compact was also tested. Analysis was carried out by line analysis of the interface by EDS, changes in the microstructure near the interface, diffusion layer thickness, and reaction products.
  As a result, it was found that the TiN ＋ Ti(C, N) layer of CVD, Ti(C, N) of CER, cBN particle and TIC binder of cBN reacted with Fe in cast iron. CVD was the thinnest Fe diffusion layer, and cBN was the thickest layer in each cast iron. The Al₂O₃ layer of CVD, Al₂O₃ of CER, and Al₂O₃ sintered compact did not react with Fe. Mg in FCV and FCD condensed on the interface of the {TiN ＋ Ti (C, N)} / Al₂O₃ layers in CVD as well as on CER and Al₂O₃ sintered compact. It did not condense on Ti (C, N) sintered compact, and is thought to condense selectively on Al₂O₃.
  The results of this study suggest that, to realize high efficiency machining of FCV, there is a need to review the tool material from the following viewpoints based on the design of available Al₂O₃ coated CVD cemented carbides; (1) Higher hardness and thicker Al₂O₃ layer on the substrate, (2) Better reaction resistance of the Al₂O₃ layer or to coat the other layers to protect the Al₂O₃ layer against Mg reaction, (3) Higher thermal conductivity of the substrate to reduce rise in cutting edge temperature.