Before the advent of the welding process, all work pieces are riveted. It is a very old work piece joining process. Although it has a history of 4-5 years, it is still the main connection. One of the processes is indispensable. Especially in the manufacturing of aerospace vehicles, the riveting workload is very large. It is claimed that the amount of rivets for the C919 large aircraft is measured in millions, and the amount of rivets for the regional passenger aircraft ARJ21 is also as large as 560,000.
The main structural material of aircraft is aluminum alloy. The net mass of aluminum structure and components of commercial aircraft accounts for 60% to 80% of the total net aircraft mass. Rivets connecting aluminum structures and parts must be made of aluminum alloys with a small electrode potential difference. Of course, it is better to use the same type of alloy rivets. If the same type of alloy rivets cannot be used, alloy potentials as close to the alloy as possible should be used to prevent dissimilar metals. Contact corrosion between and/or alloys.
Rivets are made of wire rods. In order to manufacture aircraft and other aluminum equipment, the aluminum industry and other departments have developed and manufactured a series of aluminum alloys for rivet lines. There are two types of aluminum alloy materials used in aluminum structures: heat-resistant non-reinforced aluminum alloys and heat-treatable aluminum alloys. Most of these special aluminum rivets have been incorporated into the national standard GB/T3197.
Aluminium and aluminum alloy rivet wire size China aluminum rivet wire production began in November 1956 Northeast Light Alloy Co., Ltd. (named Harbin aluminum processing plant, code number one zero plant) completed and put into production, rivet wire production capacity 1000t/ a; In September 1968, China Aluminum's Northwest Aluminum Processing Branch was established (at that time, the name of the Northwest Aluminum Processing Plant, codenamed 113 plant), and the production capacity was 300t/a, but the aviation and spacecraft rivets and wires were still mainly due to the above The two factories produce some rivets and wire rods that are imported or supplied by foreign-owned companies in China, such as aluminum-lithium alloy rivets. Aluminum and aluminum alloy rivet wire size and size deviations are shown in Table 1 (GB/T3197).
Shear Strength The load on the rivets during work is mainly shear stress. Therefore, the rivet wire must have a certain shear strength. Table 2 shows the shear strength of industrial pure aluminum and aluminum alloy rivet wire (GB/T3196) that can not be strengthened by heat treatment, and Table 3 shows the shear strength of aluminum alloy rivet wire that has undergone solution treatment and effectiveness.
Heat treatment can not be strengthened aluminum alloy rivet wire 1035 industrial pure aluminum 1035 industrial pure aluminum rivets for riveting industrial pure aluminum manufacturing components, used in the aircraft to connect the ventilation system components, wire protection conduit parts, gaskets and so on. There are more applications in aluminum chemical equipment. 1035 industrial pure aluminum is a widely used pure aluminum, its composition (mass%): Cu0.05, Mn0.05, Mg0.05, Zn0.10, Ti0.06, V0.05, (Si+Fe) 0.65, a single impurity of 0.03, Al99.35, high-voltage transmission lines are drawn with this aluminum.
3A21 alloy 3A21 alloy is a kind of Al-Mn series non-heat-treatable deformation aluminum alloy, widely used, a wide range of semi-finished products, plates, belts, foils, tubes, rods, models, lines, satin parts, GB/T3196 and GJB2055 The rivet wire properties, composition, etc. are specified, its alloying element content is 1.0% Mn ~ 1.6% Mn, wire diameter 1.6mm ~ 10.0mm, in the HX8 state bundle supply, shear strength Rc ≥ 69N/mm2. The strength of the alloy is low, but it is higher than that of industrial pure aluminum. Cold deformation can increase its strength, and it has high corrosion resistance, which is comparable to that of industrial pure aluminum. Under the unbalanced condition, the solidified structures are α-Al, Al12Mn, Al6Mn, and Al4Mn. During annealing, Al4Mn is transformed into Al6Mn. Al12Mn is metastable and completely disappears when the temperature is ≥550°C. In addition, when the supersaturated solid solution containing Mn decomposes, the initially formed Al12Mn is converted into stable Al6Mn. Impurities in the alloy Fe can form insoluble Al6 (FeMn) phase, Si may produce Al10Mn3Si (T) phase. In aircraft, it is used in the manufacture of fuel tanks, petrol-oil pipelines, cold stampings, and low-stress parts. It has numerous applications in civilian products, general equipment, and construction.
5A02 alloy 5A02 alloy is a kind of Al-Mg alloy that cannot be strengthened by heat treatment. It is equivalent to the international 5052 alloy. It has low strength and high plasticity. Cold deformation can increase its strength, but it has lower plasticity, higher corrosion resistance, and weldability. Good, suitable for working in the marine environment, cold work hardening has no effect on the corrosion resistance and weldability of the alloy, the material annealing temperature is 350°C~410°C, and GB/T3196 and GJB2055 make provisions on related matters of 5A02 alloy rivet wire. The wire diameter is 1.6mm~10.0mm, and the HX8 is supplied in bales. The annealed 5A02 alloy consists of α-Al and β phases (Al3Mg2). Impurities iron and silicon form Al3Fe and Mg2Si, and AlMg2Mn and AlFeSi may also exist. Wire shear strength Rc ≥ 1180N/mm2.
5A05 alloy 5A05 alloy: a deformed aluminum alloy containing a high Mg content (4.80% to 5.50%) and containing Mn (0.30% to 0.60%), which cannot be heat-treated and strengthened by cold deformation, improves the strength, reduces the plasticity, and annealed the material. The plasticity is high, the semi-cold-hardened material is medium in plasticity, and the corrosion resistance is high. The GJB2055 rivet wire is delivered in bundles in the HX8 state. The diameter is 1.6mm~10.0mm, and the shear strength Rc is ≥166N/mm2. This alloy is generally used to manufacture welded pipes, liquid containers, etc. that require high process plasticity and corrosion resistance to withstand moderate loads, and rivets are used to fasten parts. The corrosion resistance of 5A05 alloy is closely related to the distribution pattern of the second phase β (Al3Mg2). When the β phase is continuously distributed in the grain boundary, the alloy has considerable grain boundary corrosion and stress corrosion cracking susceptibility, but is properly annealed. By uniformly distributing the β phase in the grain boundary and crystal grains in the dispersed state, the corrosion resistance of the alloy can be significantly improved, and even the sensitivity to these two kinds of corrosion can be eliminated; the cold hardening, welding, and long-term heating in use can be reduced. The corrosion resistance of the alloy can even cause exfoliation corrosion. The microstructure of 5A05 alloy at room temperature is α-Al+β phase. Mn, Fe and Si can form AlMg2Mn, AlFeSi and Mg2Si. Annealing at 310°C to 335°C can avoid the continuous distribution of β-phase along the grain boundary. 5A05 alloy is equivalent to the United States of the 5056 alloy, alloy melting temperature range of 638 °C ~ 568 °C.
5B05 Alloy 5B05 Alloy: A type of Al-Mg series professional rivet alloy with high Mg content (4.70% to 5.70%) is not heat-treatable. Its rivets are used to rivet aluminum structures and magnesium structures. Rivets are riveted in an annealed condition because This state rivet has better plasticity. Its average magnesium content is 5.2%, slightly higher than 5.15% of 5A05 alloy. In fact, the alloying elements (Mg, Mn) content of these two alloys are equal, but in the impurity There are some differences in content, 5B05 alloy Si, Fe content should be ≤ 0.40%, while the 5A05 alloy is 0.5%, and in the 5B05 alloy, the sum of (Si + Fe) should be ≤ 0.6%, but the 5A05 The (Si+Fe) content is not specified. 5B05 alloy rivet wire diameter 1.6mm ~ 10.0mm, in the HX8 state bundle delivery, according to GB/T3196 and GJB2055 requirements, the alloy's shear strength should be ≥ 157N/mm2. Rivets need to be annealed and sealed with potassium dichromate and then riveted. If annealing in a salt bath, the rivets must be installed in thin-walled steel tubes with a closed hole (pipe diameter <50mm, wall thickness <1.5mm). The holding time is equivalent to the annealing in the air furnace, ie 40 min. 5B05 alloy wire annealing system: (350 °C ~ 410 °C), determined by the material diameter, should not be too long. The alloy rivet is used for riveting an aluminum alloy and a magnesium alloy structural member that is annealed at -196°C to 200°C. The microstructure of 5B05 alloy is comparable to that of 5A05 alloy. Its corrosion resistance is closely related to the distribution of the second phase (β-Al3Mg2). If it is continuously distributed at grain boundaries, there is grain boundary corrosion and stress corrosion cracking sensitivity. The appropriate annealing can make the β-phase fine particles evenly distributed in the grain boundary and in the crystal, significantly improving the corrosion resistance. Cold work hardening and prolonged heating during use will reduce the corrosion resistance of the alloy and even cause exfoliation corrosion.
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