impurities removal for recycled aluminum alloy
The production process of recycled aluminum alloy can be divided into three stages: pretreatment, smelting (including refining), and ingot casting. The smelting process is to add scrap aluminum into the melting furnace and heat the temperature up to melt aluminum scrap into a liquid state,after scrapping, temperature measurement and composition processes etc, then transferred to the refining furnace, add silicon, copper and other elements, and through the steps of degassing and slag refining. The harmful metal elements in the recycled aluminum melt mainly include Fe, Mg, Zn, Pb, etc., and different removal methods are required for different harmful metal elements.
1.To remove iron
Iron is an common impurity in the production of recycled aluminum, which has a very adverse effect on the quality and performance of aluminum and aluminum alloys. Therefore, in addition to pre-treatment of waste aluminum to remove iron, the inclusion of iron should be removed as much as possible during the smelting process to prevent it from being slightly soluble in aluminum and aluminum alloy melts. The following methods are generally used to remove iron inclusions:
(1)Adding manganese to remove iron. Manganese can effectively form a high-melting iron-rich phase compound in the aluminum alloy solution and deposit it on the bottom of the furnace to achieve the purpose of iron removal.
(2)Adding beryllium to remove iron. Beryllium reacts with the Al9Fe2Si2 phase in the aluminum alloy melt, thereby reducing the harmful effects of iron.
(3)There are also other ways to remove iron, such as sedimentation iron removal method: The comprehensive effect of the multi-component intermediate alloy prepared by the four substances of Mn, Cr, Ni and Zr interacts with the coarse iron-rich compound in the aluminum alloy melt to form a new multi-component iron-rich compound. Filter iron removal:It uses the principle that the iron-rich phase impurities in the aluminum alloy melt segregate at a lower temperature and a longer holding time, and uses mechanical filtration to remove the accumulated iron-rich phase substances. Smelting direct iron removal method: it is one direct smelting iron removal method, and has been widely used in the recycled aluminum industry due to its low cost and simple operation.
2.Remove Magnesium: the following methods are usually used to remove magnesium from the waste aluminum melt.
(1)Magnesium oxide removal method: it is based on the principle that the affinity of magnesium and oxygen is greater than that of other metals, during the smelting process, magnesium first reacts strongly with oxygen, and its oxides do not dissolve in aluminum and aluminum alloy melts and float up.
(2)Magnesium chloride removal: chlorine gas is commonly used for magnesium removal from regenerated aluminum melts as an oxidizing agent to react with active metals such as magnesium in the melt to form chlorides.
(3)Cryolite removal of magnesium: cryolite reacts with magnesium to form a compound that is insoluble in the melt of aluminum and aluminum alloys and removes magnesium.
(4)Remove zinc and Pb: Subsidence method is used to remove heavy metal impurities such as zinc and Pb in aluminum and aluminum alloy melts. The sedimentation method is to prolong the standing time of the aluminum and aluminum alloy melts, using the principle of higher density of zinc and Pb, so that zinc and Pb can sink into the bottom of zinc and Pb, so that zinc and Pb can sink into the bottom of furnace during smelting, stabilize the liquid flow during discharge, which can make zinc, lead and other heavy metals First, it flows out and adheres to the first few ingots poured, and these ingots can be selected for additional treatment.
In order to produce high quality aluminum alloys, it is important to control the content of impurities elements, also sometimes need to add certain elements such as silicon and magnesium to meet the alloy requirement, Anyang Huatuo in the silicon metal and magnesium metal for more than 10 years, welcome for your consult.