한국주조공학회

In order to determine the feeding distance of aluminiun alloys (Alsi7Mg and AlCu4Ti) bar castings in the sand mold, the distance of the sound castings has been observed by radiograph for various risers, melt treatment, and casting design. Variation of porosity and hardness with the distance from the riser were also measured in order to determine the casting soundness. The results obained were as follows; 1) The modulus of riser should be 1.4 times of the casting`s 2) The maximum distance which can be made sound is greatly dependent on chemical composition and ingate location, and follows the rules given by the formula; a) When the melt flows into the casting first, and the riser afterward, D = 37.7 {sqrt{T}} for AlSi7Mg D = 31.2 {sqrt{T}} for pure aluminium D {ge} 54.8 {sqrt{T}} for AlCu4Ti Where T = casting thickness in mm Of this maximum distance, aa{sqrt{T}} for AlSi7Mg and 7.5 {sqrt{T}} for pure aluminium is made sound by the chilling effect of the casting edge. b) When the melt flows into the casting passing through the riser, 30x30x600mm bars can be made sound in all cases 3) Percentage of porosity is higer in AlCu4Ti than AlSi7Mg. And it is increased gradually by moving closer to the riser in case of 30x30x600mm bars, but for the 30x30x600mm bars it is increased gradually by moving closer to the center of bars. 4) Hardness variation is similar to the tendency of porosity. And it decreased gradually with approaching to the center in case of 30x30x600mm bars.