The Effect of Tellurium on the Machinability of AISI 12L14+Te Steel
1988 年 28 巻 12 号 p. 1051-1059
詳細
1988 年 28 巻 12 号 p. 1051-1059
The effect of tellurium on the machinability of AISI 12L14+Te leaded, lowcarbon, resulfurized free-machining steel was investigated as a joint project between Inland Steel Company in the U.S.A. and Nippon Steel Corporation in Japan using two types of plunge machinability tests. The Te addition globularizes MnS inclusions and improves machinability assessed in terms of cutting force and chip breaking characteristics. However, no clear trend on the effect on surface finish was observed. More than 20% of total Te content exists in MnS inclusions as solid solution, and the rest of Te exists as compounds such as PbTe. Unlike previous observation, a phase believed to be MnTe was detected at the interface between the matrix and MnS inclusions in addition to PbTe. Enhancement of the ability of MnS inclusions to improve machinability by globularization is believed to be one of the mechanisms by which Te improves machinability, although this may not be the major mechanism in AISI 1200 series free-machining steels. Liquid metal embrittlement of PbTe or MnTe-MnS eutectic has been ruled out from the possible mechanisms when high-speed-steel tools are used because the melting points of these compounds are higher than the cutting temperature.
