가공역학 Performance evaluation of cemented carbide tools in turning AISI 1010 steel 발표자 : 유승현
1.introduction Cemented carbide still (초경합금 공구) WC기 :W, Ti, Ta 등의 탄화물을 Co로 결합시킨 합금 (프린트 기판용 마이크로 드릴, 정밀바이트) TIC기 :TiC를 주성분으로 하는 초경합금, WC기에 비해 경도, 녹는 점, 내 산화성, 내 용착성 우수 Coating CVD(chemical vapor deposition) : 도금 실내에서 고온의 피 도금물 주위에 도금하려는 화합물의 증 기를 운송가스와 함께 보내 표면에서 열분해 시켜 도금하는 방법 PVD(Physical Vapor Deposition) : 진공 중에 금속을 기화시켜 금속원자가 산화하지 않은 채 방해물 없이 피 도금물에 도금된다.
1.introduction Side cutting edge angle(SCEA)
2. 실험방법 Cutting conditions(절삭조건) 선반기계 : 9.2KW급 해리슨 M500 Cutting Speed(V) 140 m/min 200 m/min 280 m/min Feed rate(f) -0.230mm/rev -0.280mm/rev Workpiece materials(공작물 재료) Automotive AISI 1010 steel bars (length 300mm, diameter 100mm) C MN S P hardness 0.08-0.13% 0.3-0.6% Maximum of 0.04% Maximum of 0.05% 131 HV
2. 실험방법 Cutting inserts(공구) Insert 1: Kennametal black KC 935 (CVD with TiCN/TiC/Al₂O₃ coating layer sequence) Insert 2: Kennametal golden KC 792 (CVD with TiCN/TiC and PVD with TiN coating layer sequence) Insert 3: Mitubishi silver gray G5560 A5 (uncoated) Insert design : ISO ,CNMG120408 (80°-diamond insert shape with 0.8mm nose radius) Tool holder design : ISO, PCBNR 2525 M12 (SCEA of +15°, back rake angle of -15°, side rake angle of -5°
2. 실험방법 Experimental techniques(실험기법) Cutting force –tangential force –feed force –radial force Surface roughness Chip –secondary shear zone thickness(z) -chip thickness (t₂) -angle of maximum crystal elongation(ψ)
3. Result and discussion Cutting force(절삭력)
3. Result and discussion Surface roughness(표면조도)
3. Result and discussion Surface roughness(표면조도)
3. Result and discussion Microstructure studies(미세조직 연구) Chip thickness Chip ratio Secondary shear zone strain Angle of crystal elongation
3. Result and discussion Microstructure studies
3. Result and discussion Microstructure studies Micrographs(x1000) of chip roots (V=280m/min, f=0.28mm/rev) Insert 1. Insert 2. Insert 3. Example
4. conclusions 1. A remarkable achievement in this study is the reduction in bulk chip strain (high chip ratio) and low strain in SSZ (thickness of only 2 μm) 2. Having compared the performance of three cemented carbide cutting tools，insert 2 performs best performance 3. The tangential force was much higher than the other forces at any particular experimental trial. 4. The relationship curves between the forces and the cutting speed were generally found to be similar when the feed rate was increased. The same can also be said for the surface roughness and the SSZ thickness measurements. 5. The surface roughness measurements obtained increases when the cutting speed was increased contrary to established theory where Chisholm had shown that the surface finish decreases as the cutting speed increases， until the surface finish equals the ideal finish.