The active gas used in the refining of aluminum and aluminum alloy refers to the chemical reaction with the gas in the melt, and the reaction product is a gas insoluble in the melt.
At present, the commonly used active gas is chlorine. In addition to using the principle of partial pressure difference to remove the gas, the chlorine refining and degassing method also chemically reacts with hydrogen to produce hydrogen chloride and aluminum trichloride vapor. Under the action of the three gases, the purification effect is improved.
Active gas degassing and refining are characterized by significant degassing effect of chlorine gas and sodium removal effect; chlorine gas is toxic and harmful to humans, corroding equipment and polluting the environment, requiring perfect ventilation and exhaust measures and equipment. Since chlorine reacts with the titanium in the melt and destroys the primary crystal nucleation of titanium, when the chlorine is passed for too long, it is easy to refine the coarse mixed gas of the ingot structure.
Mixed gas refining (N2 and Cl2) can give full play to the advantages of inert gas and active gas refining, and avoid its shortcomings, so it is widely used in production. Practice has proved that when the chlorine concentration is 16%, the degassing effect is the best.