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남기우(K. W. Nam),황석환(S. H. Hwang),김대용(D. Y. Kim),이문용(M. Y. Lee),이상문(S. M. Lee) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.10
핫 스탬핑은 오스테나이트 변태 온도 이상에서 프레스 성형 후 급속히 냉각되는 고강도 부품을 제조하는 성형 방법이다. 매우 적은 양의 보론 성분을 가지고 있는 보론강은 핫 스탬핑에 사용되는 재료 중의 하나이다. 본 연구의 목적은 열처리 조건에 따르는 기계적 성질과 에릭슨 커핑 시험에 의하여 성형성을 조사하는 것이다. 다양한 온도에서 다이퀜칭은 대기 시간을 달리하여 실시하였다. 1173 K-0s에서 퀜칭 후 TWB는 1203 MPa의 인장 강도를 얻었다. 이것은 모재 인장강도(1,522 MPA)의 79 %이다. 금형 온도(298, 523, 673 K)에 따른 보론강 TWB의 성형성은 차이가 크지 않았다. 그러나 성형 속도가 증가함에 따라 성형성이 감소하는 것을 확인할 수 있었다. The hot-stamping technique is a forming method used for manufacturing high-strength parts, in which a part is cooled rapidly after press forming above the austenite transformation temperature. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to investigate the mechanical properties of boron steel according to the heat-treatment conditions and the formability by using an Erichsen cupping test. Die quenching from various temperatures was conducted for different elapsed heat-treatment times. Laser-welded boron steel after quenching at 1173 K-0 s has a tensile strength of 1203 MPa. This is 79% of the tensile strength of the base metal (1522 MPa). The formability of boron steel was not significantly different from that at the mold temperature. However, it decreased with increasing forming speed. These properties provide practical information for the use of boron steels for hot stamping.
미끄럼 방지 바닥 도료용 폴리프로필렌 수지의 화학적 분쇄에 관한 연구
김대인 ( D L Kim ),정화영 ( H Y Chung ),황석환 ( S H Hwang ),조익성 ( I S Cho ),윤경준 ( K J Youn ),조백수 ( B S Cho ),김광국 ( K K Kim ),윤강재 ( K J Yun ) 한국안전학회(구 한국산업안전학회) 2012 한국안전학회지 Vol.27 No.6
In this study, some experimental results of the peroxide-degradation process of polypropylene(PP) in a co-rotating twin-screw extruder to produce controlled rheology polypropylene(CRPP) are presented. The peroxide was dicumyl peroxide(DCP) and the concentration of DCP was in the range 0-0.3wt%. It was found that the rheological properties of PP change significantly during reactive extrusion. Melt fiow index(MFI) increased with DCP concentration. Intrinsic viscosity decreases with increasing DCP concentration. From dynamic rheological data, number ave-rage molecular weight(Mn), weight average molecular weight(Mn) and molecular weight distribution(MWD) were cal-culated. Results indicated that Mw decreases and MWD becomes narrower with increasing peroxide concentration. Especially, particle size distribution of CRPP decreases with increasing DCP concentration by chemical powdering process, and anti-slip floor paint, CRPP(DCP 0.2 wt%) powder by 10phr was friction coefficient 2.15μ, abrasion resis-tance 511.18%.