低温切削における超硬工具の損傷

Abstract

本研究は超硬工具を用いて,STY80鋼(タイヤ鋼)に対する低温切削をおこなった結果について報告するものである.低温をうるためにCO_2ガスを,工具を通して切刃部まで噴射し,約-50℃まで冷却した.結果として次のことが明らかとなった.(1)焼鈍材切削試験においては実験の範囲では乾式切削の場合とCO_2による冷却の場合とでは寿命に明らかな相違はみとめられない.(2)焼入材切削においてはCO_2冷却の効果があり工具寿命が改善された.(3)CO_2冷却の場合超硬工具S_2はセラミック工具がしばしばみせるような突発欠損を生じ,低温脆性を示す.

This report deals in the sub-zero machining of the STY 80 steel with cemented carbide tools. In the tests CO_2 gas was applied for cooling the cutting edge and the gas was fed through the cutting tool. Then temperatures up to minus 50 deg. were obtained in this test. The results are as follows : (1) In machining the annealed steel, there has been no difference between the tool lives in dry cut and CO_2 cooling. (2) The effect of CO_2 gas cooling is displayed in the machining of the hardened steel, namely the tool life of the carbide tool was improved. (3) The cemented carbide tool might present the brittleness in low temperatures because the carbide tool broke down very frequently in the sub-zero machining.