蒸気用タービンブレード材の高速ミーリング特性に関する研究

（ステンレス鋼13Cr およびチタン合金の切削特性）

抄録

This paper presents an experimental study on the high-speed milling of stainless steel (SUS13Cr) and titanium alloy (Ti-6Al-4V) for high-efficiency machining of steam turbine blades. As experimental conditions, the cutting speed was used as a parameter, and the width of flank wear of the outer edge of the end mill, the surface hardness of the machined surface, and the observation results of the end mill surface using energy dispersive X-ray analysis (hereinafter abbreviated as EDX) were used as evaluation criteria. The results show that the width of flank wear becomes larger at higher cutting speeds for both materials and that the surface hardness of the machined surface became harder at higher cutting speeds for stainless steel. It can be presumed that this is because the coating on the end mill is peeled off and the coefficient of friction at the cutting point is increased, which increases the strain on the surface of the crop, resulting in work hardening. As a result of using two types of coated endmills with different heat resistance temperatures on titanium alloy, a sudden increase in the width of the flank wear of the outer edge of the end mill occurred at an inflection point under a certain cutting speed. By using EDX, it was confirmed that the coating peels off and disappear. As a result of estimating the processing point temperature using AdvantEdge FEM, the processing-point temperature was higher than the heatresistance temperature of the coating, and this is considered to be the main cause. Based on these results, when highspeed milling is performed with the aim of high-efficiency machining, the surface hardness of stainless steel is improved (work hardening). In the case of titanium alloys, it is important that the processing-point temperature is not higher than the heat-resistant temperature of the coating and that the hardness of the processed surface is not reduced.