한국주조공학회

Effects of CaCN₂ addition on the grain refinement in the AM60 magnesium ingots were investigated. The effects of the CaCN₂ are estimated with different inoculation temperatures, inoculation contents, and holding time to find out the optimum condition. AM60 alloy was melted in the low carbon steel crucible by cylindrical electric furnace under an argon atmosphere. The melting and casting apparatus is specially designed for magnesium alloys. The grain size of AM60 magnesium alloy decreased significantly with an increase in CaCN₂content and, at 0.8 wt% CaCN₂ or more, grain size becomes constant at about 85μм. The optimum condition was obtained in the 0.8 wt%CaCN₂ for holding molten metal of 30 min. at the temperature of 710℃. The tensile properties of AM60 magnesium alloys were improved due to grain refinement by addition of CaCN₂. In the optimum condition, the yield strength, tensile strength and elongation were σо‚₂=107 MPa , σt.s=234 MPa and e=14.2%. The variation of stress with strain obeyed the relationship of the σ=Kε’. The strain-hardening exponent, n and strength coefficient, K obtained in the 0.8 wt% CaCN₂ added AM 60 magnesium alloy were n=0.21 and K=390 MPa.