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자동차 차체용 고강도 IF 강에서 미세조직과 기계적 성질에 미치는 Mn 의 영향
조경목,정우창 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.6
The purpose of this study was to develope IF(interstitial free) steels for the application to automotive body panels. IF steels containing less than 20 wt ppm of C and N, and 1.2 to 2.8 wt% of Mn were prepared to investigate the effect of Mn on the microstructure and mechanical properties. Microstructure observation of IF steels annealed at austenitic region revealed network type polygonal ferrite due to Mn gradient for the steels containing 1.23% Mn(A) and 1.94% Mn(B), and granular bainitic ferrite with high dislocation density for the steel containing 2.76%Mn(C). Tensile strength of A. B and C after annealing (800-920℃) was measured as about 400, 450 and 500 ㎫, respectively Tensile strength decreased slightly for A and B, butincreased for C with increasing annealing temperature. Granular bainitic ferrite of C might induce the strengthening effect at a high annealing temperature. (Fe. Ti) P precipitates formed when IF steels were annealed at ferritic region, which lead to the shortage of effective Ti content to remove solute carbon. The major texture of IF steels was found to be (554)[225 ̄] that is favorable to improve the formability. However, intensity of (554)[225 ̄] was decreased with increasing Mn content.
조경목,이희태,김수영,조영기 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.4
In the present study, wear properties, of cast Al-SiC_p composites were characterized. Wear tests were performed as a function of teat conditions including applied load, sliding speed and sliding distance under dry wear condition employing a block-on-roller type wear test machine. Wear mechanism of Al-SiC_p composites was also investigated by the analysis of worn surfaces and wear debris. Results show that wear resistance of Al alloy is improved with reinforcement of SiC_p especially with severer wear conditions such as high applied load and long sliding distance. Weight loss of Al-SiC_p composites almost linearly increases with applied load and sliding distance. There exists a transition point of wear behavior at which a minimum wear rate encountered in terms of the sliding speed. Wear mechanism is abrasive at the low speed and at .the transition speed, and adhesive/abrasive wear at the high speed range. It was found that uniform distribution of SiC_p reinforcement is desirable to improve the wear resistance of Al-SiC_p composites.
조경목,오광중,박대원,홍성수,양진섭,류봉기 한국공업화학회 1997 응용화학 Vol.1 No.2
Catalytic removal of soot particulate in the presence of excess oxygen was investigated over perovskite-type oxides by using temperature programmed reaction(TPR) in which carbon particulate/catalyst mixture was heated in the reaction gas containing nitric oxide and oxygen. LaCoO₃ catalyst was modified to enhance the activity by substitution of metal ion into A and B sites. The reaction conditions was also examined.