The performance and integrity of final Al castings are intrinsically governed by the quality of the molten metal, with hydrogen content and inclusions being the two most critical yet challenging parameters to control. To evaluate these parameters, the industry employs a range of of techniques broadly categorized into ex-situ and in-situ methods. This paper provides a systematic review of these approaches. For the ex-situ analysis of Al melt cleanliness, established methods including reduced pressure test (RPT), K-mold test, metallographic analysis, porous disc filtration analysis (PoDFA), liquid metal analyser for inclusions and solids (LAIS), and the Prefil pressure filtration method are thoroughly described. A comparative evaluation of their underlying principles, measurement accuracy, and suitability for laboratory-based quantification is also presented. For real-time monitoring, in-situ techniques such as solidification curve analysis, ultrasonic attenuation sensors for hydrogen, and the liquid metal cleanliness analyzer (LiMCA) for inclusions are examined, focusing on their application in process control. This review conducts a critical comparative analysis of these two paradigms, highlighting the inherent trade-off between the high precision of ex-situ methods and the real-time feedback provided by in-situ monitoring systems. By mapping the capabilities, limitations, and complementary roles of each technique, this work serves as a practical guide for method selection in both quality assurance and process optimization contexts.
Jia et al. (Tue,) studied this question.