AA ASD-1(M)-2013 Aluminum standards and data 2013 Metric SI.pdf
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1、Aluminumstandards and data2013 Metric SI Copyright 2013, The Aluminum Association, Inc.Unauthorized reproduction by photocopy or any other method is illegal.general information/characteristics1-1November, 20131. General Informationare corrosive to aluminum. Although the metal can safely be used in t
2、he presence of certain mild alkalis with the aid of inhibitors, in general, direct contact with alkaline substances should be avoided.Some alloys are less resistant to corrosion than others, particularly certain high-strength alloys. Such alloys in some forms can be effectively protected from the ma
3、jority of corrosive infl uences, however, by cladding the exposed surface or surfaces with a thin layer of either pure aluminum or one of the more highly corrosion-resistant alloys.A word of caution should be mentioned in connection with the corrosion-resistant characteristics of aluminum. Direct co
4、ntacts with certain other metals should be avoided in the presence of an electrolyte; otherwise galvanic corrosion of the aluminum may take place in the vicinity of the contact area. Where other metals must be fastened to aluminum, the use of a bituminous paint coating or insulating tape is recommen
5、ded.The fact that aluminum is nontoxic was discovered in the early days of the industry. It is this characteristic that permits the metal to be used in cooking utensils without any harmful effect on the body, and today we fi nd also a great deal of aluminum equipment in use by food processing indust
6、ries. The same characteristic permits aluminum foil wrapping to be used safely in direct contact with food products.Aluminum is one of the two common metals having an electrical conductivity high enough for use as an electric conductor. The conductivity of electric conductor grade (1350) is about 62
7、 percent that of the International Annealed Copper Standard. Because aluminum has less than one-third the specifi c gravity of copper, however, a kilogram of aluminum will go about twice as far as a kilogram of copper when used for this purpose. Alloying lowers the conductivity somewhat, so that whe
8、rever possible alloy 1350 is used in electric conductor applications. The high thermal conductivity of aluminum came prominently into play in the very fi rst large-scale commercial application of the metal in cooking utensils. This characteristic is important wherever the transfer of thermal energy
9、from one medium to another is involved, either heating or cooling. Thus aluminum heat exchangers are commonly used in the food, chemical, petroleum, aircraft and other industries. Aluminum is also an excellent refl ector of radiant energy through the entire range of wavelengths, from ultraviolet, th
10、rough the visible spectrum to infrared and heat waves, as well as electromagnetic waves of radio and radar.Aluminum has a light refl ectivity of over 80 percent, which has led to its wide use in lighting fi xtures. Aluminum roofi ng refl ects a high percentage of the suns heat, so that buildings roo
11、fed with this material are cooler in summer.A unique combination of properties makes aluminum one of our most versatile engineering and construction materials. A mere recital of its characteristics is impressive. It is light in mass, yet some of its alloys have strengths greater than that of structu
12、ral steel. It has high resistance to corrosion under the majority of service conditions, and no colored salts are formed to stain adjacent surfaces or discolor products with which it comes into contact, such as fabrics in the textile industry and solutions in chemical equipment. It has no toxic reac
13、tion. It has good electrical and thermal conductivities and high refl ectivity to both heat and light. The metal can easily be worked into any form and readily accepts a wide variety of surface fi nishes.Lightness is one of aluminums most useful characteristics. The specifi c gravity is about 2.7. T
14、he mass (“weight”) of aluminum is roughly 35 percent that of iron and 30 percent that of copper.Commercially pure aluminum has a tensile strength of about 90 megapascals. Thus its usefulness as a structural material in this form is somewhat limited. By working the metal, as by cold rolling, its stre
15、ngth can be approximately doubled. Much larger increases in strength can be obtained by alloying aluminum with small percentages of one or more other elements such as manganese, silicon, copper, magnesium or zinc. Like pure aluminum, the alloys are also made stronger by cold working. Some of the all
16、oys are further strengthened and hardened by heat treatments so that today aluminum alloys having tensile strengths approaching 700 megapascals are available. A wide variety of mechanical characteristics, or tempers, is available in aluminum alloys through various combinations of cold work and heat
17、treatment. In specifying the temper for any given product, the fabricating process and the amount of cold work to which it will subject the metal should be kept in mind. In other words, the temper specifi ed should be such that the amount of cold work the metal will receive during fabrication will d
18、evelop the desired characteristics in the fi nished products.Aluminum and its alloys lose part of their strength at elevated temperatures, although some alloys retain good strength at temperatures from 200C to 260C. At subzero temperatures, however, their strength increases without loss of ductility
19、, so that aluminum is a particularly useful metal for low-temperature applications. When aluminum surfaces are exposed to the atmosphere, a thin invisible oxide skin forms immediately, which protects the metal from further oxidation. This self-protecting characteristic gives aluminum its high resist
20、ance to corrosion. Unless exposed to some substance or condition that destroys this protective oxide coating, the metal remains fully protected against corrosion. Aluminum is highly resistant to weathering, even in industrial atmospheres that often corrode other metals. It is also corrosion resistan
21、t to many acids. Alkalis are among the few substances that attack the oxide skin and therefore characteristics/general information1-2 November, 2013The ease with which aluminum may be fabricated into any form is one of its most important assets. Often it can compete successfully with cheaper materia
22、ls having a lower degree of workability. The metal can be cast by any method known to foundrymen; it can be rolled to any desired thickness down to foil thinner than paper; aluminum sheet can be stamped, drawn, spun or roll-formed. The metal also may be hammered or forged. Aluminum wire, drawn from
23、rolled rod, may be stranded into cable of any desired size and type. There is almost no limit to the different profi les in which the metal may be extruded.The ease and speed with which aluminum may be machined is one of the important factors contributing to the low cost of fi nished aluminum parts.
24、 The metal may be turned, milled, bored, or machined in other manners at the maximum speeds of which the majority of machines are capable. Another advantage of its fl exible machining characteristics is that aluminum rod and bar may readily be employed in the highspeed manufacture of parts by automa
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