Research and Development of Long Life Mold Wash for Chill Casting of Aluminum Alloy

One defect which occurs in the aluminum chill casting is blacking scab defect. We investigated the mechanism and prevention of this defect using a liner-type test piece inserted in the corner of the die cavity. Results of investigations show that aluminum alloy sticks to the mold wash physically when the product is ejected from the die, creating Al-Si-Fe-O compound. To prevent the occurrence of blacking scab defects, the following are necessary : ①smoothing and closing of mold wash surface, ②packing and closing of interstices in the mold wash layer, ③selection of inactive chemical and stable binder for aluminum alloy melt. The developed mold wash consists of three layers (under coat ; conventional mold wash, middle coat ; sodium aluminate binder mold wash, primer coat ; titanium oxide mold wash). This structure was found to increase life by three to five times.