Study of Tool Failure in Turning of High Hardness Alloy Steels

• Main Authors: Tsai,Yaw-Yang, 蔡曜陽
• Other Authors: Liao, Y. S.
• Format: Others
• Language: zh-TW
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/56323491159880540111

碩士 === 國立臺灣大學 === 機械工程研究所 === 81 === High hardness alloy steels have usually been machinied by grind- ing owing to its difficult-to-cut properties. However, there are many limitations in grinding ,such as production process ,cost, work geometry and so on. Hence,machining of hard work materials with ceramic and ultrahard tools is another manufacture concept that can eliminate grinding and save both time and cost. The ob- jectives of this study are to investigate the influences of hard- ness and cutting speed on tool failure during machining of hard- ened alloy steels. The results of experiments show that alumina oxide and CBN tools have a longer tool life while carbide and cer -met tools are easy to fracture. There are two types of tool fra- cture mechanism: high stress breakage at high feed and high temp- erature plastic deformation at high speed. The saw-tooth chip occurred when the hardness of the alloy steel machined with cera- mic and CBN tools exceeds a certain value. The cutting forces are high and cutting temperature is decreased associated with saw- tooth chip. The effects of saw-tooth chip on the wear mechanism of CBN and ceramic tool are studied. The saw-tooth chip reduces the flow rate of the work material as it passes the shear zone. An layer is then formed which reduces diffusion between the tool and work material. The reasons why the continous chip with car- bide tools are also discussed.