슬라이드 1

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1 마이크로분말소재의형상가공및성형 6. 형상가공 : binder aided forming process 7. 분말성형 : powder forming process 1

2 마이크로분말소재의성형 분말재료를설계된부품의형태로만들기위한공정 입자상호간결합을유도하여기계적강도부여. Rearrangement and deformation of the particles 소결시성형체의수축율을고려하여성형밀도제어필요 마이크로분말소재의성형의종류 비 ( 무 ) 가압성형법 : 자연소결법, Slip 주조법 냉간압축성형법 : Die 성형법, 진동성형법, 연속성형법, 분말압연법, 등압성형법폭발성형법, 사출성형법 열간압축성형법 : 고온압축법, 열간압출법, 열간등압성형법, 열간사출법 2

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5 목표분말부품에적합한가공기술을확인하기위한의사결정도 5

6 6. Binder aided forming process binder 의역할 : 소결이진행될때까지분말을원하는형상으로충진하고유지시킴 binder 는최종조성에는포함되지않으나공정에중요한역할. 완벽한 binder 는없으며, 첨가제가포함된다성분계혼합물로공정에따라선별 tape cast, slurry cast, extrusion, injection molding, die forming( 다이성형 ) 등의공정 공정별분말및첨가제와기공분율에대한비교 6

7 형상가공공정 : powder binder 혼합물을가압하여금형을통해유동을일으키는것 형상의변형속도는혼합물의점도 (η : Pa sec) 에의해결정 점도는 powder 의양이많을수록증가 점도에대한간접측정법 : 액상유동지수 (melt flow index), 혼합시발생하는회전토크측정법, 모세관압출측정법 순수바인더의점도 (η B ) 에대한혼합체의점도 (η M ) 의상대비율 임계분말함량 (φ C ) 에대한실제분말함량 (φ) 의함수로나타낸그림 ( 임계분말함량 (φ C ): 유동이어려운혼합물의점도를갖는분말함량 ) 점도는유동저항에대한척도이며, 혼합체의점도는분말함량에의존한다. 7

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9 형상가공기술 (binder aided forming process) 의분류 바인더를첨가한압출 (extrusion) : 긴구조물, 작은분말, 일정한단면적, 간단형상 사출성형 (injection molding) : 복잡형상, 작은부품, 고성능부품 슬러리캐스팅 (slurry casting) : 복잡형상, 두껍고큰부품 슬립캐스팅 (slip casting) : 매우큰구조, 일정한두께, 낮은정밀도 테이프캐스팅 (tape casting): 평평한팜, 간단한형상, 작은분말 9

10 Powder Injection Molding( 사출성형, PIM) 10

11 Powder Injection Molding( 사출성형, PIM) Originally developed for plastic forming. Applied to PM to produce complex shaped products Mass production Mixture(metal/ceramic powder+polymer) 는높은압력의정수압상태의공정 밀도의균일화 Net shape forming Binder: 열가소성 wax, polymer, oil+ 계면활성제 PIM 사용분말 : Carbonyl, Oxide reduced and gas atomized powder with near spherical shape. 0.5~1.5mm 내외 Typical binder: 70% paraffin wax, 30% polypropylene + lubricant, wetting agents 150 o C 내외에서용해 Mixing ratio: 분말충진특성에따라부피분율의 40% 까지.. 공정요구사항 : Attain high packing density of particles in the binder system while maintaining a low mixture viscosity High pressure and low viscosity 11

12 몰드주입시간은냉각과정보다공정상비중이작다 12

13 PIM 에의한복합소재 (W-Cu) 의제조비교 Conventional process P I M W Skeleton Micron powder Nano powder (W-Cu) Mixing Powder-binder mixture Cu-infiltration Machining Injection molding Machining of Kovar Brazing Debinding & Sintering ( 탈지 ) 13

14 ( 탕도 ) ( 탕구 ) A sketch of the flow path in injection molding, showing the location of the nozzle, sprue, runner, and gate for a two- cavity tool set. 15MPa, less than 20sec. mold filling in a sec PIM 초기단계에서금형내부공간은 screw 위치전진에따라채워지면서유압증가유발. 금형이채워지면 screw 는고정위치에서금형내의 feed stock 을가압하에서유지되도록한다. 14

15 Alumina PIM 부품의금형주입과정 1 단계탈지 (debinding) 후분말접촉부분 : 잔류바인더는소결전분말위치고정, then burn out during sintering 15

16 Molding technology PIM 에서는최종형상보다크게제작 몰드재료는경도, 내구성, 절삭성능및연삭성능이우수해야함예 ) SUS 420, SUS 440C, H13 steel, M2 steel 등 몰드의수명 : 300,000 개이상의사출 몰드설계시제품의수축인자의정밀적용 생산성을높이기위하여는적절한 die cavity 의양고려 (~ 40pieces) 냉각공정의비중이큼. PIMed trigger guard: (Fe-Ni / polymer wax binder) After sintering and drilling As PIMed Look at the size difference, except some drilling/finishing 16

17 금형디자인 PIM 공정에서의결함 (blemishes) 의예 : a) 분말 - 바인더의분리, b) gate mark, c) 분리선 (parting line), d) ejection pin mark CAD technology 는몰딩시스템을구현하는데시간과결함을크게줄인다 17

18 금형 CAD simulation alumina plug parts 사출성형단계에서전단응력과혼합물주입상태전산모사 zirconia scissors 18

19 너무큰구조물에서는 PIM 의효율성 - 몰딩금형시스템비용과다 - 설비, 장비의규모가크고비싸다 - 몰딩, 탈지, 소결시열전달이느려사출성형주기가길다 19

20 PIM 제품응용례 스텐레스 putter 티타늄 putter 시계부품 pipe fitting orthodontic bracket 휴대폰용진동자 20

21 Bushing Side Key Carrying Strap 21

22 터보차져용임펠러시제품 광통신용 Laser Module Heat Sink 의사출성형체및 소결체 22

23 적용제품별분류 Automotive SENSOR for AIR BAG (17-4PH) TRIGGER for AIR BAG (17-4PH) VENT CAP (STS304L) Hair clipper SM-122 (SKD11) SM-128 (SKD11) Gun & Pistol TRIGGER BAR MAGAZINE CATCH FIRING PIN SEAR BLANK EXTRACTOR (7Ni-Fe, heat treated) 23

24 Computer MAG. PLATE (3%Si-Fe) ULTRA MAG. PLATE 1 (3%Si-Fe) ULTRA MAG. PLATE 2 (2%Ni-Fe) LATCH HOUSING (2%Ni-Fe) Textile YARN GUIDE BKT (STS316L) SPAN GUIDE (2%Ni-Fe, H) TAPE GUIDE HOOK (17-4PH) GUIDE PIECE (2%Ni-Fe) YARN CARRIER (2%Ni-Fe, H) Industrial machine ROLLER ARM (STS316L) SOLENOID ARM (STS316L) REGULATING PLATE (7%Ni-Fe, H) GEAR PLATE (7%Ni-Fe, H) PINION GEAR (2%Ni-Fe) SADDLE (2%Ni-Fe) CAM STACK (17-4PH) 24

압출 The extrusion process forces a slurry of powder and binder through a constriction to shape a continuous product such as a rod, tube, or honeycomb.

25 압출 The extrusion process forces a slurry of powder and binder through a constriction to shape a continuous product such as a rod, tube, or honeycomb. 응용 : Capacitor, 마이크로전자부품받침대 (substrates), 다공성튜브 ( 중심부에코어를넣어압출 ), 용접봉, 자동차용배기촉매담체 ( automobile catalytic converter substrates) 메틸셀루로우스 - 물혼합바인더를사용하여복잡구조의다이를통해압출성형한 honeycomb 구조 25

Slurry techniques : other binder assisted process (Slip casting, tape casting, extrusion) 1) Slip casting Powder + solvent + binder system (binder + dispersant( 분산제 ) + Lubricant +

26 Slurry techniques : other binder assisted process (Slip casting, tape casting, extrusion) 1) Slip casting Powder + solvent + binder system (binder + dispersant( 분산제 ) + Lubricant + defoamer( 소포제 ) ) pouring porous mold adsorbed solvent drying and debinding sintering 특징 Large component Pored structure Inexpensive Slow process Large shrinkage Low sintered density 26

27 2) Tape Casting (Dr. blade process) Tape casted powder sheet before sintering: Look at the flexibility!!! 27

28 기타 slurry processes 동결건조법 : - 몰딩후성형체를냉각동결, - 수분제거, - 적절한압력과온도조절을통한승화 후속공정에서의균열제거 전기영동전착법 (Electro Phoretic Display) : - 분말부피가 10% 범위인현탁액을이용하는성형방법 - 전해질내에분산된입자들은전하를띄게되는데전기장을가하여분말들을주어진형상으로충진 - 다이성형이어려운복잡형상, 작은크기, flexible, - 구배를갖는 (FGM) 부품제조에적합

143.fm

143.fm Journal of the Korean Ceramic Society Vol. 43, No. 1, pp. 859~864, 006. FE Analysis of Alumina Green Body Density for Pressure Compaction Process Jong-In Im and Young-Jin Yook Simulation Center for Fine