Measuring Hydrogen Content in Molten Aluminium Alloys using the CHAPEL Technique

A new method known as CHAPEL (Continuous Hydrogen Analysis by Pressure Evaluation in Liquids) for measuring hydrogen content in molten aluminium alloys has been developed and tested. The method relies on direct measurement of the hydrogen partial pressure in the melt. A number of interesting potential applications are indicated on the basis of laboratory and industrial experiences. The main advantage of the CHAPEL method, as compared to other techniques, is its ability to provide direct, continuous measurement of hydrogen in the melt, making it particularly suitable for process monitoring of aluminium melt quality. This paper systematically examines the influence of hydrogen content on porosity in aluminium-silicon cast alloys, taking solidification conditions and melt treatment into account. In this system, the greatest susceptibility to porosity is encountered with AlSi7Mg. An influence of the solidification rate on porosity, which varied with different hydrogen contents, was noted. The work describes a number of typical pore shapes and their distribution on the basis of metallographic studies.