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- Aluminum and its alloys have a unique position in modern industrial materials due to their low density, high thermal conductivity and electrical conductivity (listed only after Ag, Cu, and Au). In the manufacture of satellites, rockets, missiles, microwave components, aircraft or ground-based radar antennas, automotive water tanks or air-conditioning radiators, in order to reduce weight, reduce energy consumption, improve efficiency and enhance maneuverability, try to use aluminum as much as possible. Even the steel. The key to the replacement is the welding of Ding·Aluminum and its alloys, while the precision of welding is the first to braze.
- Where aluminum and its alloys are difficult to braze compared to other alloys, there is an extremely dense oxide film on the surface. This oxide film is very stable and resistant to atmospheric attack, and it can generate new films at any time when the old film is destroyed. The chemical nature of aluminum is very active, and it is the protection of the oxide film that is formed at any time that aluminum and its alloys are likely to become important materials today. There are also ways to completely destroy this film, such as dropping a drop of HgCl2 solution on aluminum or putting some metal mercury, rubbing with an abrasive cloth to form aluminum amalgam, and the liquid Al-Mg alloy on the aluminum surface will keep the oxide film intact and dense. At this time, it can be clearly seen that it can react with water to release hydrogen. The agglomerated aluminum and its alloys turn into a fluffy A1 (0H) in the wet state at night. Aluminum and its alloys need to be destroyed during brazing. Otherwise, the molten solder cannot be wetted with the base material; it is necessary to maintain the integrity of the protective film after welding, otherwise the joint will cause severe corrosion.
2.2 pot and key alloy number
Designations of Aluminum and its Alloys
- Pure aluminum has excellent ductility and low strength. It has special properties after adding alloys such as Mn, Mg, Cu, Si, Cr and other metals. Some can be obtained with high strength after heat treatment, and even comparable to some special steels. The alloys are classified as follows: (JIS) basically uses the American representation.
- Most of the aluminum alloys in the developed countries of the world have their own grades and components, about half of which can be compared with each other, and the composition is not exactly the same. There are quite a few children’s aluminum alloys that are developed independently, and there are no corresponding alloys in other countries. 8%。 The old number (GB) (1) in LX for industrial pure aluminum, X is the number 1~6, the smaller the number, the higher the purity, from U to L6, the purity from 99.7% to 99.8%. 5%。 The LGX represents 髙 pure aluminum, X is 0~4, the greater the X, the higher the purity, from LG1 to LG5, the purity is from 98.55% to 99.99%. Anti-rust aluminum (LF series) is Al-Mn and Al-Mg alloy, hard aluminum (LY series) is Al-Cu-Mg alloy, and forged aluminum (LD series) is A1-M-Si and Al-Mg- The Si-Cu alloy and the superhard culture (LC series) are Al-Zn-Mg-Cu series alloys. Table 2-1 lists the controls for alloy grades in different countries (7). The approximate composition of the alloy can be seen from it. Among the countries in the world, countries such as Laos, Italy, Switzerland, Belgium, Sweden, and the Netherlands adopt similar representations from the International Standardization Association, while other countries adopt the number from C. Japan Table 2-1 Comparison of alloy grades in different countries
Table 2-1 Some comparison examples of aluminum alloys designation for different countries
|category||China GB New (old)||United States AA||Russia rocT||International Standardization Organization ISO|
|Pure aluminum||1A90 (LG2) 1A85 (LG1) —(L1) 1A50 (LB2) —(L5-1)||1090
|Anti-rust aluminum||5A02 (LK2) 5A03 (LF3) 5A05 (LF5) 3A21 (LF21)||5052
|Hard aluminum||2A01 (LY1)
2 All (LY11) 2A12 (LY12)
|AlCu2. 5 Mg AlCu4MgSi AlCu4Mgl|
|Wrought aluminum||6061 (LD30) 6063 (LD31) 2A70 (LD7) 2A14 (LD10)||6061
|Super hard aluminum||7A09 (LC9)||7075||一||AlZn5.5MgCu|
|Special aluminum||4A01 (LT1)||4043||AK||AlSi5|
- In December 1972, 18 countries signed a contract to develop an international plaque naming system for deformed aluminum and aluminum alloys. This system is basically based on the American Aluminum Association (AA) nomenclature, a four-digit font system. The first digit represents the main added alloying element: 1 xxx is specially added, ie pure aluminum; 2xxx is Cu; 3xxx is Mn; 4 xxx is Si; 5 xxx is Mg; 6 xx X is Mg + Si; 7 xxx It is Zn; 8 xxx is other elements. The second represents the state of the alloy modification: 0 is the prototype and 1 is the modification. The second and fourth digits are alloy identification numbers and have no special meaning. International alloys similar to AA are identified by four digits followed by English uppercase (except I, 0, Q). The naming of China’s aluminum alloy grades has been relied on by this system, some of which are directly cited, and some are added with English letters and suffixes after four digits. For alloys that are far from AA, except for the first digit to maintain the common rule, the second digit is changed to English capital letters instead of numbers. For example, LY1 is changed to 2A01, LY12 is changed to 2A12, LF2 is changed to 5A02, and LF10 is changed. For 5B05 and so on (1).