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백승철(S. C. Baek),강충길(C. G. Kang),강석봉(S. B. Kang) 한국소성가공학회 2010 한국소성가공학회 학술대회 논문집 Vol.2010 No.5
Magnesium, which is the lightest amongst metals, has excellent material properties, such as specific strength and stiffness, ability to be cast, ability to be machined, vibration and shock-absorption ability, and fatigue resistance. As the supply of portable electronic devices, such as laptop computers and mobile phones, has been increasing, the demand for new material that possesses the attributes of recyclability and durability as well as the ability to effectively shield electromagnetic waves, which are harmful to human beings, has increased. Thus, this study aims to predict the heating time by which the temperature of the material reaches the desired temperature given a range of 150-350℃ for the die temperature. Moreover, thus far, studies about the deep drawing of magnesium sheets have focused mostly on the forming limit, microstructural change, and anisotropy that arise from rectangular, circular deep-drawing and piercing process However, research has not been reported on the effect of the clearance between the die and punch on the change in the thickness of the material, when complex shapes, such as those of electronic and automobile components, are formed by three deep-drawing. Thus, this study predicts the change in the material thickness and the forming depth at the firs forming process that produces the rectangular cup by the deep drawing of the rectangular blank. To experiment of three step deep drawing, The used magnesium sheet is fabricated with twin roll strip casting and its rolling process. The other magnesium sheet to deep drawing is fabricated by extrusion process. After three step deep drawing with rectangular shape circular shape and piercing process, respectively, the formability and thickness variation has been investigated for variation of punch speed and forming temperature.
AZ31 마그네슘 판재의 더블 싱크형 딥드로잉 공정의 성형성에 관한 실험적 연구
권기태(K. T. Kwon),강석봉(S. B. Kang),강충길(C. G. Kang) 한국소성·가공학회 2008 소성가공 : 한국소성가공학회지 Vol.17 No.8
In warm press forming of magnesium alloy sheet, it is important to control the sheet temperature by heating the sheet in closed die. When forming a commercial AZ31 magnesium alloy sheets which are 0.5mm and 1.0mm thick, respectively, time arriving at target temperature and temperature variation in magnesium alloy sheet have been investigated. The deep drawing process with rectangular shape alone at the first stage and with both circular and rectangular shapes at the second stage was employed. At the first stage, through deep drawing process with rectangular shape alone according to various forming temperature(150~350℃) and velocity(0.1~1.0mm/s), optimum forming condition was obtained. At the second stage, deep drawing process with the circular and rectangular shapes were performed following deep drawn square cups with Limited Drawing Height(LDH) obtained at the first stage. Here, clearance which is defined a gap between the die and the punch including sheet was set to ratio of 20, 40 and 100% to thickness in sheet. Accordingly, temperature, velocities, and clearances suitable for forming were suggested through investigating the thickness variation of the product.