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김명곤(M. G. Kim),권혁우(H. Gwon),허하리(H. L. Hur),김용석(Y. -S. Kim) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.5
The present investigation was performed to investigate wear-rate variation (wear-rate data scatter) in carbon steel depending on its microstructure. Steel specimens with different microstructure were used for the investigation, which are pure iron, 0.2 wt. % C steel (0.2C), 0.45 wt. % C steel (0.45C), and bearing steel (AISI52100). The pure iron, two carbon steel and the bearing steel showed microstructure of full ferrite, ferrite + pearlite and full pearlite, respectively. Depending on carbon content, the carbon steel exhibited difference pearlite-volume fraction. Dry sliding wear tests have been carried out using a ball-on-disk wear tester at a sliding speed of 0.1 m/s. Applied load and sliding distance were varied from 50 N to 150 N and from 300 m to 710 m, respectively. An AISI 52100 bearing steel ball was used as a counterpart for disk steel specimen disks. Wear rate was calculated by dividing wear volume by the sliding distance. At least three tests were conducted under the same condition, and the mean deviation of the wear rate in each specimen was compared. Specimens with the ferrite + pearlite microstructure (0.2C steel) exhibited the highest deviation from the mean wear rate at 100 N. The deviation varied with the applied load, and it decreased with the increase of pearlite volume fraction. The pure iron and the bearing steel showed much less deviation. The high deviation observed from the 0.2C steel was attributed to mixed microstructure of the two phases (ferrite and pearlite).
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.
탄소강의 초석페라이트와 시멘타이트의 형상이 미끄럼마멸 거동에 미치는 영향 분석
허하리(H. L. Hur),권혁우(H. Gwon),김명곤(M. G. Kim),김용석(Y. S. Kim) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.5
This study was conducted to elucidate the correlation between wear resistance and cementite morphology (degree of spheroidization) in carbon steel. For that purpose, we analyzed effect of the existence of pro-eutectoid ferrite and cementite morphology on the sliding wear of medium and high carbon steel. AISI 52100 bearing steel and S45C medium carbon steel were heat treated to obtain full pearlite and ferrite + pearlite microstructure. After the heat treatment, a spheroidizing heat treatment was performed on both steel to spheroidize the pearlite. Sliding wear tests were carried out using a pin-on-disk wear tester with the steel specimens as a disk. An alumina (Al₂O₃) ball was used as a pin counterpart. The sliding wear tests were carried out at room temperature in the air with humidity of 40±2 %. Adapted sliding distance and applied load was 300 m and 100 N, respectively. Sliding speed was 0.1 m/s and the wear-track radius was 9 mm. Worn surfaces and cross-sections of the wear track were examined using an SEM. Micro Vickers hardness of the wear-track subsurface was measured as a function of depth from the worn surface. It was found that sliding-wear resistance of both AISI 52100 bearing steel and S45C steel decreased as the cementite morphology become more spheroidized.
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.
복합조직을 지닌 0.2wt% C강의 미끄럼 마멸속도 편차 분석
김명곤(M.-G. Kim),권혁우(H. Gwon),허하리(H.-L. Hur),김용석(Y.-S. Kim) 한국소성가공학회 2014 한국소성가공학회 학술대회 논문집 Vol.2014 No.10
The present investigation was performed to investigate wear-rate variation (wear-rate data scatter) in 0.2wt% C steel depending on its microstructure. The steel was heat treated to get polygonal ferrite + pearlite, acicular ferrite + pearlite, polygonal ferrite + martensite and martensite microstructure. Dry sliding wear tests were carried out using a ball-on-disk wear tester at a sliding speed of 0.1m/s. Sliding distance were varied from 300m to 710m and applied load was 100N. An AISI 52100 bearing steel ball was used as a counterpart for disk steel specimen disks. Wear rate was calculated by dividing wear volume by the sliding distance. At least five tests were conducted under the same condition, and the wear-rate data scatter in each specimen was compared. At sliding distance 300m, specimens with the polygonal ferrite + pearlite microstructure exhibited the highest deviation from the mean wear-rate. On the contrary specimens with the polygonal ferrite + martensite microstructure showed the lowest deviation from the mean wear-rate. Wear-rate deviation was related to the number of crack nucleation sites in the subsurface.