Abstract
Gas porosity is still one of the most frequent casting defects in aluminium castings. In practice, the first step in avoiding gas-induced casting defects is to try to minimize the hydrogen content of the melt, using various degassing techniques. A new measuring method for determining hydrogen content in aluminium melts (CHAPEL method) continuously monitors the lance and impeller degassing process. This study examined the influence of various process parameters (flushing gas flow rate, rotor speed) and melt conditions on the efficiency of degassing treatments for unmodified AlSi9Mg melts. Impeller degassing with optimized process parameters achieves much lower hydrogen contents than lance degassing. Hydrogen values attained under these conditions guarantee the production of high-quality castings. To ensure high degassing efficiency and prevent regassing, the melt temperature should not exceed 780°C during either lance or impeller degassing.