The recycling of waste aluminum is generally carried out through the following four basic processes.
(1) Preparation of waste aluminum materials
First of all, the primary classification of waste aluminum, hierarchical stacking, such as pure aluminum, deformed aluminum alloy, cast aluminum alloy, mixed materials. For scrap aluminum products, it shall be dismantled to remove steel and other non-ferrous metal parts connected with aluminum materials, and then made into waste aluminum materials through washing, crushing, magnetic separation and drying. For thin and loose sheet-like scrap aluminum parts, such as locking arms on the car, speed gear bushings and aluminum chips, they should be pressed into a bag with a hydraulic metal baler. For steel-cored aluminum stranded wires, the steel core should be separated and the aluminum wire wound into a coil.
(2) Ingredients
According to the preparation and quality of waste aluminum materials, according to the technical requirements of recycled products, select and calculate the amount of various materials. The oxidative burning loss of the metal should be considered in the batching. The oxidative burning loss of silicon and magnesium is larger than that of other alloying elements, and the burning rate of various alloying elements should be determined experimentally in advance. The physical specifications and surface cleanliness of the waste aluminum material will directly affect the quality of the recycled product and the metal yield. The waste aluminum with unclean oil will have up to 20% of the active ingredient entering the slag.
(3) Regenerated deformation aluminum alloy
The deformed aluminum alloys that can be produced from waste aluminum alloys are 3003, 3105, 3004, 3005, 5050, etc., mainly producing 3105 alloy. In order to ensure that the chemical composition of the alloy material meets the technical requirements and the process requirements of the pressure processing, a part of the original aluminum ingot should be added if necessary.
(4) Recycled cast aluminum alloy
Only a small part of the waste aluminum material is regenerated into a deformed aluminum alloy, and about 1/4 of the deoxidizer for steelmaking is produced, and most of it is used for reclaiming aluminum alloy for casting. Die-cast aluminum alloys a380, aDCl0, etc., which are widely used in the United States and Japan, are basically regenerated from waste aluminum.
Waste aluminum pretreatment wind selection method
The purpose of waste aluminum pretreatment technology is to realize the mechanization and automation of waste aluminum separation, to maximize the removal of metal impurities and non-metallic impurities, and to effectively sort waste aluminum. The most ideal sorting method for waste aluminum is to divide the waste aluminum into several categories according to the main alloy composition, such as alloy aluminum, aluminum-magnesium alloy, aluminum-copper alloy, aluminum-zinc alloy, aluminum-silicon alloy and the like. This can alleviate the difficulty of removing the impurity technology and adjusting the composition in the smelting process, and can comprehensively utilize the alloy composition in the waste aluminum, especially the waste aluminum containing zinc, copper and magnesium, which are separately stored and can be used as the smelting aluminum alloy. Adjust the ingredients of the ingredients.
The wind selection method can separate waste paper, waste plastics and dust. Various waste aluminums contain more or less waste paper, waste plastic film and dust. The preferred process is air separation. The process of the wind selection method is very simple, and it can efficiently separate most of the light waste materials, but it must be equipped with a better dust collection system to avoid dust pollution to the environment. The sorted waste paper and waste plastic film are generally not suitable for further sorting and can be used as fuel.
Iron impurities are very harmful to the smelting of scrap aluminum. When iron is too much, brittle metal crystals are formed in the aluminum, thereby reducing its mechanical properties and reducing its corrosion resistance. The iron content should generally be controlled below 1.2%. For waste lead containing more than 1.5% iron, it can be used as a deoxidizer for the steel industry. Commercial aluminum alloys rarely use aluminum scrap with high iron content. At present, there is no very successful method in the aluminum industry to satisfactorily remove excess iron in scrap aluminum, especially in the form of stainless steel.
Waste aluminum often contains organic non-metallic impurities such as paint, oil, plastic and rubber. It must be removed before it can be smelted. For wire-like waste aluminum, mechanical coating or shear stripping, heat stripping, chemical stripping, etc. are generally used to remove the foreskin. At present, domestic enterprises often use high-temperature ablation to remove insulators. During the ablation process, a large amount of harmful gases will be generated, which will seriously pollute the air. If a combination of low-temperature baking and mechanical peeling is adopted, the insulator can be softened by heat, the mechanical strength is lowered, and then peeled off by mechanical boring, thereby achieving the purpose of purification and at the same time recovering the insulator material. Coatings, oil stains and other contaminants on the surface of waste aluminum vessels may be cleaned with an organic solvent such as acetone. If they cannot be removed, they should be stripped in a paint stripping furnace. The maximum temperature of the paint stripping furnace should not exceed 566 ° C. As long as the waste material stays in the furnace for a sufficient period of time, the general oil and coating can be removed.
For aluminum foil paper, it is difficult to effectively separate the aluminum foil layer and the paper fiber layer by ordinary waste paper pulping equipment. The effective separation method is to first heat and press the aluminum foil paper in an aqueous solution, and then quickly discharge it to a low pressure environment. And mechanical agitation. This separation method can recover both fiber pulp and aluminum foil.
The liquefaction separation of waste aluminum is the development direction of recycling aluminum metal in the future. It combines the pretreatment of reclaimed aluminum scrap with remelting, which not only shortens the process, but also avoids air pollution to the utmost extent, and makes the recovery of net metal. The rate has been greatly improved.
In the device, there is a filter that allows gas particles to pass through. In the liquefied layer, aluminum is deposited at the bottom, and organic substances such as paint adhered to the waste aluminum are decomposed into gas, tar and solid carbon at 450 ° C or higher, and then passed through an oxidizing device inside the separator. Completely burning. The waste is stirred by a rotating drum, mixed with the dissolved liquid in the silo, and impurities such as sand and gravel are separated into the gravel separation zone, and the dissolved ferrite is taken out by the recovery propeller and returned to the liquefaction chamber.
Taps and dies are tools used to create purpose screw threads, which is called threading. Many are cutting tools; others are forming tools. A tap is used to cut or form the female portion of the mating pair (e.g. a nut). A die is used to cut or form the male portion of the mating pair (e.g. a bolt). The process of cutting or forming threads using a tap is called tapping, whereas the process using a die is called threading.
Using an ordinary tap or die to clean threads generally removes some material, which results in looser, weaker threads. Because of this, machinists generally clean threads with special taps and dies-called chasers-made for that purpose.
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