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0.3wt.%C 탄소강의 미세조직과 3-body 연삭마멸 거동 사이의 상관관계
정영중(Y. -J. Jeong),김종철(J. C. Kim),권혁우(H. Gwon),김용석(Y. -S. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
The present investigation was performed to find out the relationship between 3-body abrasive wear characteristics and microstructure in a 0.3 wt.% C steel. The steel was heat treated under different conditions to have PF/P (Polygonal ferrite & Pearlite), B (Bainite), M (Martensite) and TM (Tempered martensite) microstructures. Three-body abrasive wear tests were carried out using a ball-cratering tester. The tester used AISI 52100 steel ball as a counterpart. The ball-surface was roughened prior to the test, which was necessary for smooth feeding of abrasive slurry into the contact between the ball and the specimen. The slurry was composed of Al₂O₃ particles (4㎛) suspended in water with a concentration of 0.75g/ml. The slurry was fed on top of the ball throughout the test at an approximate rate of 1.445g/min. All tests were performed at a normal load of 0.2 N, sliding (ball rotation) speed of 0.1m/s and sliding distance of 50m. Microstructure of the heat treated specimens was observed by an optical microscope, and the worn surfaces were observed by a stereoscopic optical microscope and SEM (scanning electron microscope). The M (martensite) specimen showed the highest 3-body abrasive wear resistance due to its much higher hardness than the others. Among the specimens with similar hardness, the PF/P (polygonal ferrite/pearlite) specimen displayed high wear resistance, where the wear proceeded by a ploughing mechanism.
0.3C, 0.35C 탄소강의 시멘타이트 형상 변화에 따른 3-body 연삭마멸 거동 비교
정영중(Y. -J. Jeong),김명곤(M. G. Kim),김용석(Y. -S. Kim) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
Microstructural influence on 3-body abrasive-wear in carbon steel has been investigated. It has been found that the wear behavior changes significantly depending on cementite morphology in steel with similar hardness. Carbon steels with different carbon content (0.3C and 0.35C) were heat treated under different conditions to change the cementite morphology: PF/SP (Polygonal ferrite + Spheroidized pearlite) and TM (Tempered martensite) microstructures. Three-body abrasive wear tests were conducted using a ball-cratering tester. AISI 52100 steel ball was used as a counterpart material. All tests were performed at a normal load of 0.2 N, sliding (ball rotation) speed of 0.1 m/s and sliding distance of 50 m. Microstructure of the heat treated specimens was observed by an optical microscope, and the worn surfaces were observed by a stereoscopic optical microscope and an SEM (scanning electron microscope). Test results showed that as the shape of cementite becomes more spherical, the more wear loss was observed. Plate-like carbides resulted in high wear resistance.
0.3 wt.% C 탄소강 미세조직 시멘타이트 형상에 따른 3-body 연삭마멸 기구 변화
정영중(Y. -J. Jeong),권혁우(H. Gwon),김고남(G. Kim),김재윤(J. -Y. Kim),김명곤(M. G. Kim),김용석(Y. -S. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
The present investigation was performed to figure out the effect of cementite morphology on 3-body abrasive wear characteristics in a 0.3 wt. %C steel. The steel was heat treated under different conditions to have PF/P (Polygonal ferrite & Pearlite), PF/SP (Polygonal ferrite & Spheroidized pearlite), and TM (Tempered martensite) microstructures. Three body abrasive wear tests were carried out using a ball-cratering tester. AISI52100 steel ball was used as a counterpart. The ball-surface was roughened prior to the test, which was necessary for steady feeding of abrasive slurry into the contact between the ball and the specimen. The slurry was composed of Al₂O₃) particles (4 ㎛) suspended in water with a concentration of 0.75 g/㎖. The slurry was fed on top of the rotating ball throughout the test at the rate of 1.445 g/min. All tests were performed at a normal load of 0.2 N, sliding (ball rotation) speed of 0.1 ㎧ and sliding distance of 50 m. Microstructure of the heat treated specimens was observed by an optical microscope, and the worn surfaces were observed by a stereoscopic optical microscope and an SEM (scanning electron microscope). The PF/P (polygonal ferrite/pearlite) specimen displayed high wear resistance, where the wear proceeded by a ploughing mechanism.
0.25 wt.% C 탄소강의 미세조직 변화와 3 - body 연삭마멸 특성
정영중(Y.-J. Jeong),김종철(J. C. Kim),윤나래(N. R. Yoon),권혁우(H. W. Kwon),김용석(Y.-S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
This investigation was performed to reveal the effect of microstructure on 3-body abrasive wear behavior of the 0.25wt.% C steel. The steel was heat treated under different conditions to obtain PF/P (Polygonal ferrite & Pearlite), AF(Acicular ferrite) and PF/TM (Polygonal ferrite & Tempered martensite) microstructures. Three-body abrasive wear tests were carried out using a ball-cratering tester. The ball was an AISI 52100 steel ball. The ball-surface was roughened by rotating on a specimen to feed slurries easily into the contact between the ball and the specimen. The roughening distance was 7.85 m. The slurry of Al2O3 particles(4μm) suspended in water with concentration of 0.75 g/ml was fed on top of the ball throughout the test at a rate approximately 1.445 g/min. All tests were performed with a normal load of 0.2N, sliding(ball rotation) speed of 0.05 m/s and sliding distance of 50 m. Microstructure of the heat treated specimens was observed by an optical micorscope, and worn surface were observed by a stereoscopic microscope and SEM (scanning electron microscop). Hardness of the stell was measured by a micro Vickers hardness tester. The PF/P microstructure showed the best 3-body-abrasive-wear resistance among the microstructures examined in the present study.
AISI 52100 베어링강의 미세조직에 따른 3-body 연삭마멸거동
정영중(Y. -J. Jeong),김종철(J. C. Kim),권혁우(H. W. Gwon),윤나래(N. R. Yoon),김용석(Y. -S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.5
This investigation was performed to reveal the microstructural effect on 3-body abrasive wear behavior of the AISI 52100 bearing steel. The steel was heat treated under different conditions to obtain bainite and pearlite microstructures. The bainite and pearlite microstructures were obtained by holding the solution treated specimens at 300℃ and 330℃ for 2 hours and at 650℃ and 700℃ for various period followed by water quenching, respectively. Three-body abrasive wear tests were carried out using a ball-cratering tester. Abrasive slurries of SiC particles (4 fim) suspended in water were used at constant concentration (0.75 g/ml). All tests were performed with a sliding speed of 0.05 m/s, normal load of 0.2 N and sliding distances of 50 m. The slurries were fed on to the top of the ball throughout the test at a rate approximately 1.15 g/min. The worn surfaces were observed by a stereoscopic microscope, SEM, and FESEM (field emission scanning electron microscope). The hardness of specimens was measured by a micro Vickers hardness tester. It was found that the wear resistance of the pearlite was better than that of the bainite.
미끄럼 거리에 따른 STS 304 스테인리스강의 마멸기구 변화
김재윤(J. -Y. Kim),권혁우(H. Gwon),정영중(Y. -J. Jeong),김고남(G. Kim),김명곤(M. G. Kim),김용석(Y. -S. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10
In this paper, sliding wear tests of the 304 stainless steels were performed at room temperature varying sliding distance and applied load using a pin-on-disk wear tester. Worn surfaces and wear debris were analyzed using an XRD and observed by an SEM. Micro Vickers hardness was also measured as a function of depth from the worn surface to evaluate work hardening during the wear. Test results showed that the wear mode changed from mild wear to severe plasticity dominated wear (metallic particle oxidation, adhesive wear) as the sliding distance and the applied load increased. The change in the wear mechanism was associated with subsurface plastic deformation and work-hardening. Strain-induced martensitic transformation was observed on the sliding surface of the austenitic stainless steel. Relationship between the transformation and the work-hardening was explored and discussed.
AZ31B 마그네슘 합금 판재의 Galling특성에 미치는 금형소재와 온도의 영향
권혁우(H. Gwon),김종철(J. C. Kim),정영중(Y.-J. Jeong),김재윤(J. Y. Kim),김용석(Y.-S. Kim) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
Galling is the most frequently observed gross damage include scratching, grooving and plastic deformation of surfaces of metal sheet (or tools), which is associated with adhesion or stiction during hot forming of magnesium alloys. This study was undertaken to examine tribological phenomena during sliding of tool steel against AZ3l B Mg alloy and to find out formation mechanism of the galling. Reciprocating sliding of tool steel against the Mg-alloy plate was carried out at various temperature and normal loads under an un lubricated condition. The galling behavior was evaluated by measuring friction coefficient and surface roughness together with SEM observation. Higher and severely fluctuating friction coefficient was measured during sliding at 250℃ than at room temperature. The high and largely varying friction coefficient at 250 ℃ was explained by enhanced adhesion between the two surfaces and easier plastic deformation of the Mg alloy at high temperature.
AZ31B 마그네슘 합금 galling 기구에 미치는 온도와 하중의 영향
권혁우(H. Gwon),정영중(Y.-J. Jeong),김누리(N.R. Kim),김용석(Y.-S. Kim) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
Galling is the most frequently observed tribological phenomena during sheet metal forming, which is associated with adhesion (stiction) and transferring of a metallic particle from softer sheet metal to harder tool surface. In this study, tribological characteristics during sliding of STD-61 tool steel against AZ31B magnesium alloy were examined to find out galling mechanism of AZ31B magnesium alloy-tool steel tribopair at different loads and temperatures. Flat surface-on-disk reciprocating tests were carried out at various applied loads under both dry and lubricated condition at room temperature and 250 ℃. Galling of the AZ31B magnesium alloy was evaluated by measuring friction force (friction coefficient), surface roughness and observing slid surfaces of both Mg alloy and tool steel by OM and SEM. The results showed that number of asperity junctions formed between the two surfaces increased rapidly as temperature and applied load increase. Severe plastic deformation was observed at the slid surface of the AZ31B magnesium alloy sheet.
연마제의 크기와 미세조직에 따른 0.18 wt. % C 탄소강의 3 - body 연삭마멸 특성
윤나래(N. R. Yoon),정영중(Y.-J. Jeong),김종철(J. C. Kim),권혁우(H. W. Gwon),김용석(Y.-S. Kim) 한국소성가공학회 2011 한국소성가공학회 학술대회 논문집 Vol.2011 No.10
Three-body abrasive wear behavior of 0.18 wt % C steel was investigated using a ball-cratering tester. Silicon carbide of various sizes was used as an abrasive. Wear test conditions were optimized to ensure three-body abrasive wear preventing two-body abrasive wear during the test. The abrasive was supplied as a slurry form, of which the concentration was 0.75 g/ml. Sliding distance, speed (ball-rotation speed) and normal load were fixed as 50 m, 0.05 m/s, and 0.2 N, respectively. Before the abrasive wear test, 0.18 wt % C steel was heat treated under various conditions to vary its microstructure. Effect of the microstructure as well as the abrasive-particle size on the wear was investigated. It was found that the abrasive wear behavior did not depend on a specific parameter such as hardness; besides, the effect of microstructure and abrasive-particle size was significant in determining the wear of the steel.