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습식 Cr도금 대체를 위한 CrN박막의 내마모성 및 내식성 향상에 관한 연구
김상식(Sang S.Kim),김갑석(Kab S.Kim),한전건(Jeon G.Han) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
CrN hard coating becomes one of the attractive protective films for enhancement of wear and corrosion resistance due to its superior properties. In addition, the noted property of CrN coating is the excellent corrosion resistance. Therefore CrN coating has a strong potential to replace the electro-deposited hard chrome coating which generates serious environmental pollution problem at present in the world. In this study, CrN film was deposited on S45C by cathodic arc ion plating process. The deposition of CrN laver was carried out at the various N₂ partial pressure of 5×10^-3 torr to 2×10^-2 torr under the bias voltage of -200V. All the coated specimens were analyzed by XRD and SEM for structural characterization and the wear and corrosion behaviors were compared with those of hard Cr coated specimens y ball-on-disc wear test and electrochemical polarization measurement.<br/> The CrN coating deposited at 1×10^-2 torr showed the highest CrN(220) intensity and a maximum hardness of Hk 2700 which is twice of that of the hard Cr coating. The wear resistance of CrN coated S45C against Al₂O₃ and AISI 52100 steel balls was highly improved compared to that of the hard Cr coating. The CrN coatings also enhanced the resistance of pitting and crevice corrosion. This improvement was associated with the formation of the CrN coatings with dense and fine granular structures without microcrack which exists in all the electroplated hard Cr coating.<br/>
권용철(Y. C. Kwon),김상열(S. H. Kim),김홍태(H. T. Kim),문호근(H. K. Moon),이세희(S. H. Lee),정상인(S. I. Jeong),양재규(K. G. Yang),김상식(S. S. Kim) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5
Main Shaft is one of the key components to connect between Rotor hub and Gear box in wind turbine. The mechanical components for wind turbine is most being manufactured with hot open die forging. The purpose of this study is to develop the manufacture process of Hollow Main Shaft by open die forging. In case of the open die forging for large forged part, pass schedule of manufacture process is most important because it can affect final dimensions of product. In this paper, hot compression tests were carried out to obtain the flow stress of cast microstructure at different temperature and strain rates. The measured flow stress dates were used to simulate the upsetting, piercing, pipe forging and final flange upsetting process of cast ingot using the practical material properties. Also the mechanical properties after forging of Hollow Main Shaft were investigated from the experiment. From the results, the prototypes of Hollow Main Shaft were manufactured based on analyzed results, productivity was stable, mechanical properties was increased and product dimension was optimized with suggested process. With FE-Analysis and prototype, the advantages of new method (hollow type) such as material utilization, mechanical properties and production cost were verified.
진상욱(S. U. Jin),이영선(Y. S. Lee),김상식(S. S. Kim) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
In this study, the importance of failure analysis on large ring forged products was assessed and the process and methodology were introduced. Failure analysis case study of the large ring forged steel product with approximately 10 mm long internal crack found by non-destructive test (NDT) was presented. The micrographic and fractographic observations and the verifying tests were conducted on the cracked specimen to identify the possible metallurgical reason for the defects, and the metallurgical aspects of internal crack formation were discussed.
박철,김상식,권용남,이영선,이정환,Park, C.,Kim, S.S.,Kwon, Y.N.,Lee, Y.S.,Lee, J.H. 한국재료학회 2003 한국재료학회지 Vol.13 No.6
The effect of forging parameters, including different forging stock, strain rate and strain, on the mechanical properties of hot-forged Al 6061-T6 was investigated. The forging was conducted using either hydraulic press, crank press or hammer press, respectively, at a forging temperature of $400^{\circ}C$. When using an extruded bar as a forging stock, the tensile strength was lower for the specimens prepared by hammer forging than those by crank press forging. It was found that the coarsening of recrystallized grain was responsible for the decrease in tensile strength with hammer forging. Systematic studies on the effects of strain and strain rate on the tensile properties of hot-forged Al 6061-T6 products using extruded bar as a forging stock further suggested that the coarsening of recrystallized grains and$ Mg_2$Si precipitates complexed the observed trends in the tensile behavior. In case of hot forging with continuous cast bar as a forging stock, on the other hand, the mechanical properties of the specimen were largely improved with hammer press compared to those with crank press, which appeared to be due to the homogenization of microstructure.