I. Comprehensive knowledge of aluminum alloy profiles
Aluminum profile is aluminum bar through hot melting, extrusion, so as to get different cross-section shape of aluminum material. The production process of aluminum profiles mainly includes casting, extrusion and coloring (coloring mainly includes: oxidation, electrophoretic painting, fluorocarbon spraying, powder spraying, etc.) three processes.
Aluminum profiles are divided into:
1. Industrial aluminum profile: mainly used in airplanes, trains, industrial radiators, automobiles, electrical appliances, etc.
2. Aluminum alloy building profiles: mainly used for building doors and Windows, curtain walls, indoor and outdoor decoration and building structure with aluminum profiles.
Aluminum profile according to the surface treatment is divided into:
1. Anodized aluminum material: the surface of the profile is anodized, electrolytically colored or organic colored.
2. Electrophoretic coating aluminum: the surface of the profile is treated by anodic oxidation and electrophoretic coating.
3. Powder spraying aluminum material: the surface of the profile is coated with thermosetting organic polymer powder.
4. Fluorocarbon paint spraying aluminum: profile surface with polyvinylidene fluoride paint coating. At present, the heat insulation profiles commonly used are a kind of aluminum alloy profiles that are threaded or castable.
Key indicators:
1. Appearance quality: the surface of the anodized profile is not allowed to have electrical burns, oxide film falling off and other defects affecting the use; Electrophoresis, powder, fluorocarbon profiles paint after the paint film should be uniform, neat, smooth, do not allow wrinkles, cracks, bubbles, flow marks, inclusions and paint film off the impact of the use of defects, but in the profile end 80mm range to allow local film. The appearance quality of aluminum alloy building profiles affects the decorative effect of buildings, so the surface of the factory profiles must be covered with film to avoid scratches, scratches and corrosion in the process of transportation and stacking. Some aluminum alloy building profiles in the market have similar water striation and mildew spots in the inner cavity, which reflects the defects in the production process.
2. Wall thickness: the wall thickness of the profile is one of the main factors affecting the strength of the workpiece, and the main profile is the force part in the project. For example, the minimum nominal wall thickness of the main profile of the window shall not be less than 1.4mm.
3. Film thickness: the extruded aluminum alloy profile, its surface corrosion resistance is not strong, must be surface treatment to increase the corrosion resistance, wear resistance and appearance of aluminum. Anodized aluminum film thickness is divided into AA10, AA15, AA20, AA25, electrophoretic coating aluminum film thickness is divided into A.B.S, powder spraying aluminum decorative surface coating minimum local thickness Greater than or equal to 40um, fluorocarbon paint coating aluminum decorative surface coating thickness due to different coating types, requirements are different. Average film thickness of two coatings Greater than or equal to 30um, average film thickness of three coatings Greater than or equal to 40um, average film thickness of four coatings Greater than or equal to 65um.
4. Chemical composition, mechanical properties: aluminum alloy profiles of different grades, the supply state of the chemical composition, mechanical properties of technical parameters are different, customers should check the standard (contract) one by one.
5. Color and color difference: there are differences in color and color difference in different grades and supply states of alloy. It is suggested that the influence of color and color difference inconsistency on building structure should be fully considered when selecting alloy grade and supply status.
6 salt spray corrosion resistance, abrasion, weathering, mortar, etc. : this is an important technical parameter of aluminum alloy profiles, reflect the performance of aluminum alloy profiles, affect the use.
Two, high-end aluminum alloy special chlorine and nitrogen mixture refining device
The liquid aluminum from the electrolytic cell contains various impurities, so it needs to be purified before casting. Purification methods such as clarification, flux and gas are mainly used in industry, and directional solidification and filtration methods are also used in some cases.
1. Flux purification
Flux purification is to use the flux added to liquid aluminum to form a large number of fine droplets, so that the oxides in liquid aluminum are wet adsorption and dissolved by these droplets, forming a new droplet to the surface, after cooling to form scum removal.
The flux used for purification is composed of salt with low melting point, small density, small surface tension, large activity and strong adsorption capacity for oxidation slag. When using, first put small pieces of flux into the iron cage, and then insert them into the bottom of the mixing furnace and stir back and forth until the flux is melted, take out the iron cage and rest for 5 10min. Scoop out the surface scum can be cast. The flux can also be removed to cover the surface as required.
2. Gas purification
Gas purification is a main primary aluminum purification method, the gas is chlorine, nitrogen or chlorine nitrogen mixture.
(1) Chlorine gas purification. Previously, active chlorine gas was used as a purifying agent (chlorination method). In the chlorination process, when chlorine gas is passed into liquid aluminum, a lot of very small bubbles of AlCl3 are formed, which are fully mixed in the liquid aluminum. Hydrogen dissolved in the liquid aluminum and some mechanical inclusions are adsorbed on the AlCl3 bubbles and discharged as the AlCl3 bubbles rise to the surface of the liquid aluminum. Chlorine gas can also make some more electronegative element chlorination than aluminum, such as calcium, sodium, magnesium and so on, due to chlorine gas and generate corresponding chloride, can be separated. So chlorination is a very effective method of primary aluminum purification. Chlorine gas consumption is 500-700g per ton of aluminum. But because oxygen is toxic and more expensive, in order to avoid air pollution and reduce the cost of aluminum ingot production, so in the modern aluminum industry has gradually abandoned the chloride method into inert gas - nitrogen purification method.
(2) Nitrogen purification method. Also known as smokeless continuous purification method, with alumina ball (418mm) as the filter medium. N2 is directly injected into liquid aluminum. Liquid aluminum is continuously sent into the purification furnace, through the alumina ball filter layer, and is washed by nitrogen, so the non-metallic inclusions in liquid aluminum and dissolved hydrogen can be removed, and then discharged continuously, so that the fine nitrogen bubble evenly distributed in the treated liquid aluminum plays a role in purification. Nitrogen is pollution-free to the atmosphere and has a large purification capacity, which can treat 200 600kg liquid aluminum per minute. The aluminum loss caused in the purification process is relatively reduced, so it is widely used now. But it is not like chlorine to remove calcium, sodium, magnesium in liquid aluminum.
(3) mixed gas purification method. The mixture of chlorine and nitrogen gas is used to purify liquid aluminum. Its role is to remove hydrogen and separate oxides on the one hand, and remove some metal impurities (such as magnesium) in aluminum on the other hand. The commonly used composition is 90 percent nitrogen plus 10 percent chlorine gas. Some use 10 percent chlorine plus 10 percent carbon dioxide plus 80 percent nitrogen. This works even better. Carbon dioxide diffuses chlorine gas and nitrogen gas, shortening operation time.
Three, pure aluminum, refined aluminum, high purity aluminum difference
Pure aluminium: metallic aluminium that contains at least 99.0 percent aluminium and does not exceed the following limits:
Fe plus Si content is not more than 1.0 percent ;
Other elements include Cr, Cu, Mg, Mn, Ni and Zn. If the chromium and manganese content does not exceed 0.05%, the copper content is allowed > {{0}}.10 percent to Less than or equal to 0.20 percent .) Each content is not more than 0.10 percent .
Refined aluminum: pure aluminum with a content of 99.0 percent or more is made by special smelting method with a purity of no less than 99.95 percent . For example, China's national standard GB/T8611-2000 is listed in 4 kinds of refined aluminum ingot.
High purity aluminum: aluminum with a purity of no less than 99.999 percent produced by a special smelting method (e.g., directional solidification purification method) using high quality refined aluminum as raw material. For example, China's non-ferrous metal industry standard YS/T275-1994 lists two kinds of high purity aluminum.
