Relationship between the permeability of the porous disk filter and the filtrate weight - time curves generated with the PoDFA / Prefil® footprinter method

Abstract

Current methods to quantify metal quality suffer from disadvantages in complexity, expense or response time. One method suggested to provide a real-time quantitative assessment of metal quality is the use of filtrate weight-time curves produced by filtering the metal through a porous disk filter. The slope and overall shape of this curve should indicate the level of inclusions present in the metal. Hydro Aluminium increasingly employs such methods to assess the quality of both Aluminium und Magnesium alloys. Several different types of crucible and porous disk filter are used. Due to the increasing importance of this assessment method a better understanding of the importance of variations in the permeability of the filter was considered necessary. This paper describes a device to measure the permeability of the filter discs. It also gives details of trials conducted to quantify the effect of variations in filter permeability on the filtrate weight - time curves.