Prodn. of passivated near-eutectic aluminium-silicon alloy - comprises adding pre-alloy contg. strontium to melt just before tapping to reduce contact-time and hydrogen pick-up

摘要

A quasi Al-Si alloy is rendered passive by adding a prealloy contg. Sr to the alloy directly before the melt is tapped into the mould at a turbulent part of the melt flow. The prealloy is added in the casting channel with the time between alloy addition and tapping being 0.1-5 min. The ratio of Sr (in wt.%) to the (in ml/100g) in the prealloy is min. 5. The H2 content in the prealloy is max. 1.5 ml/100 g. The prealloy is in the form of a wire and is added to the melt continuously or discontinuously. The Sr content in the prealloy is 3-20 wt.% and the prealloy contains fine grained elements. The quasi-eutectic alloy contains 5-14 wt.% Si and the final alloy contains 0.01-0.08 wt.% Sr. ADVANTAGE - By considerably reducing the contact time between alloy melt and Sr-contg. prealloy prior to casting the H2 pick-up is reduced thereby reducing the amt. of final porosity. The resulting pores produced are also finely dispersed.