The granular refining agent has a good slag removal (oxide, boride, and carbide) and impurity removal (alkali metal elements Na, Ca, and Li) in the aluminum melt. The principle of slag removal is: when the solid particle refining agent is sprayed into the aluminum melt by inert gas, the solid particles can quickly melt into droplets. Because the density of these droplets is less than that of the aluminum melt, the surface tension of the slag inclusions is smaller. It has a strong ability to wet and adsorb slag inclusions; when the slag inclusions are adsorbed by the flux droplets, they float up and are expelled from the melt. At the same time, after the flux droplets float up, a liquid layer is formed to cover the surface of the aluminum melt, thereby reducing the oxidative burning loss of the aluminum melt. The impurity removal principle of Granular Refining Agent is: after the magnesium ion-containing compound in the refining agent enters the aluminum melt, it will react with the alkali metal elements Na, Ca, and Li to release magnesium atoms into the aluminum alloy melt, and at the same time absorb the reaction The alkali metal elements Na, Ca, and Li are brought to the surface of the aluminum melt, thereby playing the role of removing alkali metals.
In the process of aluminum alloy smelting, inclusions and gas are often generated, which greatly affects the quality of ingots and aluminum products. Common inclusions include oxides, carbides, nitrides, borides, etc. Among them, oxides (such as Al2O3, MgO) pollute the aluminum alloy melt the most. These inclusions not only provide a carrier for the gas, but also make the increase of the gas content in the melt, also causes defects, such as slag inclusion and looseness in the ingot. In addition, the impure raw and auxiliary materials used in smelting aluminum alloys will also bring some harmful impurities to the melt, such as alkali metals such as Na, Ca, Li, etc., which reduce the physical and chemical properties of aluminum alloys. The Na element has a high Mg content. The aluminum alloy easily causes “sodium embrittlement” and also reduces the fluidity of the melt. Therefore, in the production of aluminum alloy materials, there are strict regulations on the slag content, gas content, and impurity element content in the aluminum alloy melt.
In order to remove the gas and inclusions in the aluminum alloy melt, the aluminum melting and casting industry usually uses a mixed refining agent of inert gas (N2, Ar, etc.) and powder flux (NaCl, KCl, Na2 SiF6, etc.), which is sprayed in the melting furnace. Method for refining purification treatment. In order to remove harmful impurity elements (Na, Li, Ca), chlorine-containing gas refining is used. However, this traditional refining process has many shortcomings, such as: a large amount of harmful gases and smoke containing chlorine and fluorine are generated, which pollutes the environment; the powder mixed refining agent exists in the melt in solid form, which is harmful to slag inclusions. The effect of adsorption and dissolution is not obvious, and the effect of degassing and slag removal is limited. If the operation is improper, it is easy to form flux inclusions and pollute the aluminum alloy melt; the local high temperature chemical reaction during the refining process will cause serious aluminum oxidation burnout and so on.