It's necessary to add various alloy elements to enhance performance of aluminum to make different grades of alloy. Some aluminum processing plants have used metal additives to replace the master alloy. In terms of the using effect, aluminum metal additives not only have all the advantages of master alloy but also overcome some disadvantages, which makes additives more and more widely used.
Aluminum and aluminum alloy additives are far superior to master alloys due to their excellent adding mechanism, convenient use method, stable element actual yield and economical production method. The melting temperature of the master alloy is so high as to reduce the melting furnace life and increase the burning loss of aluminum and alloy elements as well as decrease the smelting productivity and worsen the working conditions. What's more serious is that the composition of the master alloy is not uniform, which brings a series of difficulties to control the content of alloying elements in the future. In terms of most aluminum alloys for civil use, the metal additive for aluminium is an ideal material to replace the master alloy.
Aluminum metal additive may be added directly to the melting furnace or the holding furnace, but it must be added before refining. Other conditions need to be met in order to achieve the due casting yield of alloying elements which are specified as follows:
Due to the pure metal addition mechanism, the absorption rate of alloying elements always increases as temperature raises. On-site experience shows that aluminum and aluminum additives are sensitive to temperature, especially manganese. Additives should be added when aluminum liquid temperature controlled at 740±10℃, otherwise the time of metal absorption will be prolonged.