Study of Tool Failure in Turning of High Hardness Alloy Steels
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....
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| Format: | Others |
| Language: | zh-TW |
| Published: |
1993
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| Online Access: | http://ndltd.ncl.edu.tw/handle/56323491159880540111 |
| Summary: | 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.
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