COMPARING HYDROGEN TESTING METHODS FOR WROUGHT ALUMINUM

In this study on selected wrought aluminum alloys, several commonly us ed methods for determining hydrogen were compared and verified with re gard to accuracy, reproducibility, and process-related limits. The two direct methods studied-the AlScan and CHAPEL (continuous hydrogn anal ysis by pressure evaluation in liquids) techniques-are able to quantit atively determine hydrogen content directly in the melt. In testing, b oth showed outstanding agreement with regard to accuracy and reproduci bility. Two analytical methods were also studied-vacuum solid extracti on and carrier fusion extraction. Both the direct and analytical metho ds yielded satisfactory agreement among the results. Also studied was an indication method, reduced-pressure testing, which is a quick and s imple method suitable for the qualitatively evaluating hydrogen conten t. Here, however, the relationship between the density index and the h ydrogen content of the melt is influenced by numerous factors.