Cutting techniques of high manganese non-magnetic steel

Among the machining techniques for high manganese non-magnetic steel, to which attention has been paid recently as the structural steel for atomic energy equipment, the methods of effectively turning and drilling this material, such as proper tools and optimum cutting conditions, are discussed. High manganese steel has been used as an abrasion resistant steel, but recently, its stable low permeability has been recognized anew, and it has begun to be used as a non-magnetic structural steel for the experimental apparatuses for nuclear fusion and the guideways for linear motor cars. It is expected to be used widely as the structural steel in special environment such as strong magnetic field or cryogenic condition, substituting for conventional austenitic stainless steel. However, from the viewpoint of machining, its large work hardening rate and low heat conductivity lower the machinability, which largely changes due to the C and Mn contents. In this paper, the selection of cutting conditions and tools when the high manganese steel with the composition adopted for the nuclear fusion experiment facility JT-60 was turned and drilled is reported. The methods of the machining tests and the results are described. The techniques of using cemented carbide drills must be developed. (Kako, I.)