In metallurgy, gas flushing removes dissolved gases from the molten metal prior to the material being processed. For example, before casting aluminium alloys, argon bubbles are injected into liquid aluminium using a rotary degasser. The argon bubbles rise to the surface, bringing with them some of the dissolved hydrogen. The degassing step reduces the occurrence of hydrogen gas porosity. In the steel making process, this method is used very commonly for duplex steel and some high reactivity metals.