| 摘要 |
PURPOSE: To provide a cutting tool made of a silicon nitride matter sintered body which is excellent in strength, toughness and chipping resistance and capable of high speed feeding. CONSTITUTION: A cutting tool is mainly composed of β-Si3 N4 minute particle being less than 3μm in diameter, cylindrical β-Si3 N4 large particle being more than 3μm in diameter, and the grain boundary phase of oxide and/or nitride- oxide. In the section of an sintered body, the area of β-Si3 N4 large particle is from 2 area % to 40 area % of the sectional area of silicon nitride substance sintered body, and the average aspect ratio (=major axis/minor axis) of β-Si3 N4 large particle in a section cut in parallel to a tool face 1 is larger more than 5% than the average aspect ratio of β-Si3 N4 large particle in a section cut perpendicularly to the tool face 1. |
