The chemical composition and condition
Pure aluminum is relatively weak structural material with a tensile strength of about 90 MPa. However, in addition to aluminum of small amounts of such alloying elements as manganese, silicon, copper, magnesium or zinc, and the appropriate heat treatment and / or after cold plastic deformation, limit strength aluminum - aluminum alloy or longer - may reach 700 MPa.
Many aluminum alloys have wide ranges of mechanical and physical properties, depending on the type of condition. These states are obtained by processing aluminum product, as the heat, and deformation. These wide ranges of properties of aluminum alloys allow selection of just such an aluminum alloy, that would provide the maximum desired properties at the lowest cost.
Three grade aluminum
Aluminum is classified into three main grades:
- "Pure" aluminum; it is aluminum with varying degrees of purity, aluminum brand;
- aluminum alloys shaped castings, that is, casting castings; this is - casting aluminum alloys.
- Aluminum alloys for the manufacture of metal treatment methods pressure, i.e, pressing (extrusion), rolling, forging, stamping; this is - wrought aluminum alloys.
Industrial undoped Aluminum - commercially pure aluminum - aluminum comprises from 99,80 to 99,00 %. Unalloyed aluminum has a relatively low strength and therefore is of limited use as a structural material. The exceptions are those cases, when important are good electrical conductivity, ease of handling and high corrosion resistance. Pure aluminum has no ability to thermally harden. However, the strength properties of pure aluminum may be increased by autofrettage, i.e. cold plastic deformation.
Pure aluminum has poor casting properties, so it is used mainly in the form of products, are prepared by methods of metal forming.
Wrought Aluminum Alloys
Most of the aluminum alloys, which are used for the manufacture of metal forming methods, contain no more than 7 % alloying elements. By controlling the amount of and type of alloying elements improve the properties of aluminum and increase its processability. for instance, special aluminum alloys have been developed for specific production processes such as extrusion and forging.
Wrought aluminum alloys (as well as cast alloys) are subdivided into thermally hardenable and thermally non-hardenable alloys.. Improving the mechanical properties of thermally neuprochnyaemyh aluminum alloys are produced by peening, i.e. cold plastic deformation with or without subsequent partial annealing him. Improving the mechanical properties of the thermally hardenable alloys is achieved by tempering them at a suitable temperature and subsequent aging. For some thermally hardenable alloys use a combination of heat treatment and work hardening.
The main types of semi-finished products, which is prepared from wrought aluminum alloys, are:
- sheets (plates),
- extruded profiles, tubes, rods, rods,
- cold drawn pipes;
- wire and
Casting aluminum alloys
Aluminum alloys, which are designed for casting castings contain one or more alloying elements in an amount of not more than 12 % each. Some foundries "designed" so alloys, so they can be used in the as-cast condition without any heat treatment. Other alloys have the chemical composition, that they can be subjected to heat treatment to improve their mechanical properties and dimensional stability. High strength with good ductility can be obtained by choosing suitable chemical composition and heat treatment.
Classification of aluminum alloys
The global aluminum industry, a system of classification of aluminum alloys, which is based on the system of the American Aluminum Association (AA). The same classification used international standards ISO and European standards EN, but in addition to digital signage is also used in alloys alphanumeric characters.
All aluminum alloys are divided into wrought and cast alloys, that, in turn, subdivided into various series (groups) according to the main alloying elements. Each of these groups or belongs to the thermally hardenable alloys, or alloys thermally neuprochnyaemym.
Based on the classification of the American Aluminum Association American Standard ANSI H35.1 notation gives aluminum and aluminum alloy, which include:
- method of their application (deformable, foundries and for remelting ingots), and
- condition of the alloy (excluding ingots for remelting, which are stateless).
Designations wrought alloys
To designate deformable aluminum and deformable aluminum alloys, the international digital system of four numbers is used:
The first digit
The first digit “1” indicates a series of technical grades of aluminum.
a sign, on which aluminum alloy refers to one of a series of 2xxx to 8xxx, is the alloying element with the maximum average (nominal) content. The exception is the 6xxx series alloys, in which the main feature is the ratio of the predominant magnesium and silicon content, are available for the formation of magnesium silicide, Mg2Si.
If the same maximum average content in the alloy have several alloying elements, then the selection of the series is made in the order of the series: copper, manganese, silicon, magnesium,, silicide tycoon, zinc.
The second digit
The aluminum stamp series 1xxx designation, which have a second digit from 1 to 9 indicate special control of one or more individual impurities.
In the alloys of the 2xxx series to 8xxx second digit of the alloy refers to alloy modification. If the second digit is zero, this indicates an initial, base alloy. figures from 1 to 9 show, respectively, modification of the base alloy.
The third and fourth digits
1xxx series includes unalloyed aluminum with natural levels of impurities. The last two digits (10xx) are used to indicate the minimum allowable aluminum content in various versions of unalloyed aluminum.. Usually they are called names aluminum.
These last two digits match the last digits of the minimum aluminum content, which is indicated to the nearest 0,01 %. for instance, aluminum content at least 99,80 % Aluminum has grade designation 1080.
The last two digits in the notation of the series 2xxx alloys from 8xxx to have no physical or chemical sense, and simply identify various alloys within group.
Sometimes at the end of the four-digit notation is added to the letter A, which indicates the modification of the alloy. for instance, Alloy 6063A alloy modification is 6063.
Full designation of wrought aluminum alloy for finished goods other than designations alloy must include his condition, for example, 6063-T6.
Designations cast alloys
The international system of signs cast aluminum grades and aluminum alloys is also based on four numbers, however, the latter figure is separated from the rest of a decimal point. This system identifies a grade of aluminum and aluminum alloys, as well differentiates their options for the finished castings and ingots for remelting.
The first digit
The first number in the designation of cast aluminum alloys indicates a series of alloys:
For casting alloys from 2hh.h to 8hh.h corresponding series is determined by the alloying elements, which is present in the alloy to a maximum average concentration. If the alloy is the same maximum average content of alloying elements have several, then for such an alloy, the main alloying element is determined in the order of the series: from copper (2xx.x) to tin (8xx.x).
The second and third digits
Foundry aluminum series 1hh.h second and third digits, as for aluminum wrought, indicate the purity of the metal. For the alloys from series to 2hh.h 9hh.h second and third digits identify a particular casting aluminum alloy.
The number after the point
The chemical composition of the same cast alloy, which is identified by the first three digits, It has options depending on its purpose, which is indicated by the fourth digit - the digit immediately after the decimal point:
- 0 denotes a casting (finished product);
- 1 denotes a standard ingot;
- 2 denotes an ingot having a narrower chemical composition within the standard of chemical composition of the ingot.
Additional embodiments of the chemical composition, for example, difference in content of impurities, designated by capital letters in front of a digital alloy designation. for instance, one of the most popular alloys for gravity casting, alloy 356, It has options A356, V356 and S356. Each of these alloys is identical to the content of the main alloying elements, but different levels of impurities, especially iron.
Full designation aluminum alloy casting – a molded article – It should include the state, which it received in manufacturing, for example, A356-T5. Designation of casting aluminum alloy ingot, which is intended for the preparation of melt alyuminevogo, naturally, It does not include the state information.