AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE 3RD INTERNATIONAL SEMINAR ON METALLURGY AND MATERIALS (ISMM2019): Exploring New Innovation in Metallurgy and Materials - Tangerang Selatan, Indonesia (23–24 October 2019)] PROCEEDINGS OF THE 3RD INTERNATIONAL SEMINAR ON METALLURGY AND MATERIALS (ISMM2019): Exploring New Innovation in Metallurgy and Materials - Comparative study of degassing method by using NaF-NaNO3-based tablet degasser, technical argon gas, and pure argon gas in aluminum casting