Before the welding process was introduced, all the workpiece joints were riveted. It is a very old workpiece joining process. Although it has a history of four or five thousand years, it is still one of the main joining processes. lack. Especially in the manufacture of aerospace vehicles, the riveting workload is very large. It is said that the rivet of the C919 large aircraft is in the order of one million, and the rivet of the regional passenger aircraft ARJ21 is also up to five or six hundred thousand.
The main structural material of the aircraft is aluminum alloy, and the net quality of aluminum structures and parts of commercial aircraft accounts for 60% to 80% of the total net mass of the aircraft. The rivet connecting the aluminum structure and the part must be made of aluminum alloy with the smallest electrode potential difference. Of course, it is better to use the same alloy rivet. If the same alloy rivet cannot be used, the electrode potential should be applied as close as possible to the alloy to prevent dissimilar metals and / or contact corrosion between alloys.
Rivets are made of wire. In order to manufacture aircraft and other aluminum equipment, the aluminum industry and other departments have developed and processed a series of special aluminum alloys for rivet lines. There are two types of aluminum alloy materials for aluminum structures: heat-treated non-reinforced aluminum alloys and heat-treated reinforced aluminum alloys. Most of these special rivet aluminum alloys have been included in the national standard GB/T3197.
Aluminum and aluminum alloy rivet wire size
China's aluminum alloy rivet wire production began in November 1956. Northeast Light Alloy Co., Ltd. (then known as Harbin Aluminum Processing Factory, code 701 factory) was completed and put into production, rivet wire production capacity of 1000t / a; September 1968 in September China National Aluminum Corporation's Northwest Aluminum Processing Branch (then the name of the Northwest Aluminum Processing Plant, coded 133 Factory) was built, with a production capacity of 300t/a, but the aerospace rivet wire is still mainly produced by the above two factories, some rivets and Wires are imported or supplied by foreign-owned enterprises in China, such as aluminum-lithium alloy rivets. The dimensions and dimensional deviation of aluminum and aluminum alloy rivet wire are shown in Table 1 (GB/T3197).Shear strength
The load that the rivet receives during work is mainly shear stress, therefore, the rivet wire must have a certain shear strength. The shear strength of the industrial pure aluminum and aluminum alloy rivet wire which can not be strengthened by heat treatment (GB/T3196) is shown in Table 2, and the shear strength of the aluminum alloy rivet wire which is solution treated and timely is shown in Table 3.Heat treatment can not strengthen aluminum alloy rivet wire
1035 industrial pure aluminum
1035 industrial pure aluminum rivets are used for riveting components made of industrial pure aluminum, used in aircraft to connect ventilation system components, wire protection conduits, gaskets, etc. There are many applications in aluminum chemical equipment. 1035 industrial pure aluminum is a widely used pure aluminum, its composition (% by mass): Cu0.05, Mn0.05, Mg0.05, Zn0.10, Ti0.06, V0.05, (Si+Fe) 0.65, other impurities, single 0.03, Al99.35, high-voltage transmission lines are drawn with this kind of aluminum.
3A21 alloy
3A21 alloy is a kind of Al-Mn non-heat-treated reinforced deformation aluminum alloy. It is widely used and has a complete range of semi-finished products. Plate, belt, foil, tube, rod, type, wire and satin are available. GB/T3196 and GJB2055 are rivets. The properties and composition of the wire are specified. The alloying element content is 1.0% Mn~1.6% Mn, the wire diameter is 1.6mm~10.0mm, and the bundle is supplied in the HX8 state, and the shear strength Rc≥69N/mm2. The strength of the alloy is low, but higher than that of industrial pure aluminum. Cold deformation can increase its strength and has high corrosion resistance, which is equivalent to that of industrial pure aluminum. The solidification structure under unbalanced conditions is α-Al, Al12Mn, Al6Mn, Al4Mn, and Al4Mn is converted to Al6Mn during annealing. Al12Mn is metastable and completely disappears at temperatures ≥550 °C. Further, when the supersaturated solid solution containing Mn is decomposed, the initially formed Al12Mn is converted into stable Al6Mn. The impurity Fe in the alloy forms an insoluble Al6 (FeMn) phase, and Si may produce an Al10Mn3Si(T) phase. Used in the manufacture of fuel tanks, gasoline oil pipelines, cold stampings, and low-force parts in aircraft, there are a large number of applications in civilian products, general equipment and construction.
5A02 alloy
5A02 alloy is an Al-Mg alloy which cannot be strengthened by heat treatment. It is equivalent to the international 5052 alloy. It has low strength and high plasticity. Cold deformation can improve its strength, but it reduces plasticity, has high corrosion resistance and good weldability. Suitable for working in the marine environment, cold work hardening has no effect on the corrosion resistance and weldability of the alloy. The annealing temperature of the material is 350°C~410°C. GB/T3196 and GJB2055 stipulate the related matters of the 5A02 alloy rivet wire. 1.6mm~10.0mm, the HX8 state is supplied in bundles. The annealed state 5A02 alloy structure is composed of α-Al, β phase (Al3Mg2), and the impurity iron and silicon can form Al3Fe and Mg2Si, and possibly AlMg2Mn and AlFeSi. The wire has a shear strength Rc ≥ 1180 N/mm2.
5A05 alloy
5A05 alloy: a deformed aluminum alloy with high Mg content (4.80%~5.50%) and Mn-containing (0.30%~0.60%) non-heat treatable. Cold deformation can improve strength, reduce plasticity, plasticity of annealed material High, semi-cold hardened material has medium plasticity and high corrosion resistance. It is delivered in bundles according to GJB2055 rivet wire in HX8 state, diameter 1.6mm~10.0mm, shear strength Rc≥166N/mm2. This alloy is commonly used in the manufacture of welded pipes, liquid containers, etc., which require high process plasticity and corrosion resistance, and is used for fastening components. The corrosion resistance of 5A05 alloy is closely related to the distribution of the second phase β (Al3Mg2). When the β phase is continuously distributed at the grain boundary, the alloy has considerable grain boundary corrosion and stress corrosion cracking sensitivity, but is properly annealed. By uniformly dispersing the β phase in the grain boundary and the grain, the corrosion resistance of the alloy can be significantly improved, and even the sensitivity to the two kinds of corrosion can be eliminated; the cold work hardening, the welding, and the long-term heating in use are lowered. The corrosion resistance of the alloy may even cause spalling corrosion. The normal temperature structure of 5A05 alloy is α-Al+β phase, Mn, Fe and Si can form AlMg2Mn, AlFeSi and Mg2Si, and annealing at 310 °C~335 °C can avoid the continuous distribution of β phase along the grain boundary. The 5A05 alloy is equivalent to the US 5056 alloy, and the alloy has a melting temperature range of 638 ° C to 568 ° C.
5B05 alloy
5B05 alloy: a high-content (4.70%~5.70%) Al-Mg professional rivet alloy, which can not be heat-treated and reinforced, the rivet is used for riveting the aluminum structure and the magnesium structure, and the rivet is riveted in the annealed state because of this state. The rivet has the best plasticity, and its average magnesium content is 5.2%, which is slightly higher than 5.15% of the 5A05 alloy. In fact, the alloying elements (Mg, Mn) of the two alloys are equal, but in terms of impurity content. There are some differences. The Si and Fe contents of the 5B05 alloy should be ≤0.40%, and the 5A05 alloy is 0.5%. In the 5B05 alloy, the sum of (Si+Fe) should be ≤0.6%, but for the 5A05 (Si The content of +Fe) is not specified. 5B05 alloy rivet wire diameter 1.6mm~10.0mm, delivered in bundles in HX8 state, according to GB/T3196 and GJB2055, the shear strength of the alloy should be ≥ 157N/mm2. After the anodic oxidation and potassium dichromate are sealed, the rivet needs to be annealed and then riveted. If it is annealed in a salt bath, the rivet must be placed in a thin-walled steel pipe with a closed hole (tube diameter <50mm, wall thickness <1.5mm) The holding time is equivalent to the annealing in the air furnace, that is, 40 minutes. Annealing system of 5B05 alloy wire: (350 ° C ~ 410 ° C), according to the diameter of the material, should not be too long. The alloy rivet is used for riveting annealed aluminum alloy and magnesium alloy structural members operating at -196 ° C to 200 ° C. The microstructure of 5B05 alloy is equivalent to that of 5A05 alloy. Its corrosion resistance is closely related to the distribution of the second phase (β phase-Al3Mg2). If it is continuously distributed at the grain boundary, it has grain boundary corrosion and stress corrosion cracking sensitivity. By performing appropriate annealing, the β phase is uniformly distributed in the grain boundary and the crystal in a fine particle, and the corrosion resistance is remarkably improved. Cold work hardening and long-term heating during use reduce the corrosion resistance of the alloy and even cause spalling corrosion.
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