| 摘要 |
PROBLEM TO BE SOLVED: To enhance heat resistance, and to improve high speed cutting performance by using a cubic system boron nitride sintered body having the average particle size not more than a specific value, having the specific ratio of diffraction intensity to diffraction intensity in X-ray diffraction and substantially containing no inclusion in a grain boundary, as an edge. SOLUTION: This milling cutter is a cubic system boron nitride sintered body composed of cubic system boron nitride (cBN) having the average particle size not more than 1 μm. This cBN sintered body has isotropy being not less than 0.05 in the ratio of (220) diffraction intensity of cBN to (111) diffraction intensity of cBN in X-ray diffraction of a cBN sintered body. In a manufacturing method of a cubic system boron nitride sintered body (a cBN sintered body) used for an edge of a milling cutter, low pressure phase boron nitride (hBN) is synthesized by reducing/nitriding a compound containing boron and oxygen in an atmosphere of carbon and nitrogen. When obtained hBN is processed at high temperature under high pressure by both conditions of pressure not less than 6 GPa and a temperature range of 1550 to 2100 deg.C in nitrogen gas or in a vacuum, a nucleus of cBN is grown from hBN, and is directly converted into cBN having the average particle size not more than l μm by growth of a cBN crystal to simultaneously become the cBN sintered body. |
