Why is this method better than merely cutting the RPT samples and visually evaluating the porosity?
While the “cut and look” method may seem to be easier and faster, it has been demonstrated to actually be slower than an automated measurement of the specific gravity of samples. With the QCD-1 System, the results are available in less than 25 seconds and are a quantified, reproducible measurement that may be stored in a computer. Thus the measurements are a near ideal, low-cost method to measure hydrogen levels in molten aluminum melts. It may be seen from an examination of pictures shown on another page of this site that the bubble density is not uniform across multiple sections of the same RPT sample, and that visual estimates of the “Rating” are actually very subjective, even when evaluated by experienced operators. Differences in Ratings of more than two or three levels are not uncommon, and can have a large bearing on gas level control in aluminum melts.
