China Aluminum Online: At 20:43 pm on November 3, 2016, China’s larger-thrust new generation launch vehicle, the Long March No. 5, was launched from the Wenchang Air Launching Site on Hainan Island in China and skylit, reaching its scheduled orbit after about 30 minutes. The first launch mission of the launch vehicle was a success. This loud noise that broke through the sky shocked the entire globe, marking China’s crossing the threshold of the aerospace powerhouse and entering the World Aerospace Power Club.
The Long March 5 rocket is a real big man. It is a veritable "fat five" with a mass of about 870 tons for takeoff and 12 "big hearts" - engines. The take-off thrust is about 10.56 MN (1078t force). The low orbit (almost orbit) carries Capacity 25t, high (geosynchronous transfer) orbital carrying capacity of 14t level, over the international large-scale carrier rocket near-Earth orbit carrying capacity of 20t, high orbit of the 10t "gap", with the United States God of the universe 5, Delta 4, The Arian, Europe’s major players in the world’s major rockets have completed their transformation.
The "Large" of the Long March 5 is also reflected in its appearance. Its diameter is 50% larger than that of the active rocket, its core-level diameter is 5m, and the outer four boosters are 3.35m in diameter, which is more than that of China's current service rocket. The big 49.3% and 49.0%.
The length of the five rockets is about 57m, which is a bit higher than the 20-storey building. However, it is shorter than that of the Long March 2 launch vehicle. Therefore, the Long Five Rocket can accommodate much more propellant. The core-level rocket propellant is -253°C liquid hydrogen and -183°C liquid oxygen. The booster propellant is liquid oxygen and kerosene. This is the first time in the development of Chinese carrier rockets due to liquid hydrogen and liquid oxygen. The temperature is very low, so some people call the Long Five Rocket the “ice arrow†and there are more than 100,000 parts and components.
Fuel tank aluminum alloy
The Long March V rocket has 870 tons of takeoff mass, of which liquid hydrogen (-253 °C) and liquid oxygen (-183 °C) account for 90% of the mass, ie, the mass of the two fuels is 783 tons. According to reports, the development of the Long March V rocket lasted 10 years, breaking through 247 key technologies represented by 12 key technologies, many of which are related to aluminum alloy materials. Among the key technologies, the proportion of new technologies accounts for almost 100%, all core technologies have independent intellectual property rights, and the upgrading of the Long March Rockets has been achieved, which has enabled China to leap into aerospace power, and has also made China a solid leader in aluminum processing. Stride.
Whether the major components of the Long March V rocket were made from what materials were not reported by the media, but it is certain that the aluminum alloy in the structural materials is definitely the mainstream because of the huge liquid-hydrogen oxygen tank of the core-class rockets, and 4 assists. The liquid oxygen and kerosene storage tanks of pushers should all be made of aluminum alloys. Only aluminum alloys can work under such extreme conditions: First, they are small and lightweight, about 30% of steel density; Excellent performance, no low-temperature brittleness, the strength and ductility of aluminum alloys increase simultaneously with the decrease of temperature, becoming a class of excellent low-temperature structural materials, becoming a difficult to replace aerospace materials; processability and formability Well, good weldability, especially friction stir welding (FSW) performance, the United States large rocket low temperature fuel aluminum alloy tank is friction stir welding.
2219 aluminum alloy is excellent
Low temperature fuel tank material
What type of aluminum alloy welding is used for the liquid hydrogen (-253°C) and liquid oxygen (-183°C) tanks of the Long March 5 large rockets? What kind of aluminum alloy ring forging is used to connect and fix the forging rings? No media reports, but The liquid hydrogen and liquid oxygen tanks used by large-scale rockets launched abroad are either welded in the United States or in Japan and Europe. They are all welded with 2219 aluminum alloy plates (>6mm~10mm). The plates should be China Aluminum Corporation. Produced by their respective factories, they have 60 years of experience in producing aerospace aluminum and have passed certification from the aerospace department.
Look at the true face of 2219 alloy
Alloy 2019 is a high-strength, high-toughness, high-temperature, heat-resistant alloy developed by Alcoa for the aerospace industry. It was registered with Alcoa Corporation in 1954. In 2008, China incorporated 2219 and 2519 alloys into national standards. GB/T3190, since then, 2219 and 2519 alloys are not only American alloys, but also China's standard alloys. Their calibration chemical compositions are shown in Table 1. Besides Ti and V, they also contain 0.10% to 0.25% Zr.
The 2219-type Al-Cu-Mn alloy contains a small amount of Ti, V, and Zr, and the composition is quite complex. Therefore, the alloy has good high- and low-temperature properties, and Ti, V, and Zr can form Al3Ti, Al3Zr, and Al5V compounds. It has the effect of refining grains, increasing recrystallization temperature and heat resistance. Alloys of this type were introduced in the early 1950s and can be processed into a wide variety of semi-finished products for the production of components operating at temperatures between 200°C and 300°C and at extremely low temperatures.
In Al-Cu-Mn alloys, Cu and Mn are the main alloying elements, Cu and Al form the compound Al2Cu, which is the main strengthening phase, and 2519 alloy contains 0.05% to 0.40% Mg, because the amount is too small, it will not Compounds formed, all solid solution, a slight solid solution strengthening effect, Ti, Zr, V compounds are dispersed particles distributed in the matrix, there are some dispersion strengthening effect.
Mn is the main element for ensuring the heat resistance of the alloy, and Ti, Zr, and V also have a certain role. The diffusion coefficient of Mn in aluminum is small, which can reduce the diffusion of Cu in Al, not only decreases the decomposition tendency of α(Al) solid solution, but also reduces the tendency of Al2Cu to aggregate at high temperatures. The content of Mn should not be more than 0.4%. Otherwise, T phase (Al12CuMn2) can be formed, which is unfavorable for the heat resistance of the alloy. Adding a small amount of Mn on the one hand, due to the formation of Al6Mn on the heat resistance of the alloy, on the other hand can reduce the tendency of weld formation cracks.
Mg reduces the weldability of alloys 2219, 2319, and 2419, and its content should not exceed 0.02%. However, alloy 2519 contains 0.05% to 0.40% Mg, which is intended to improve its room temperature strength and to improve it at 150°C to 250°C. The heat resistance.
Impurity Zn accelerates the diffusion of Cu in aluminum and is detrimental to the properties of the alloy. Fe forms a ternary compound Al7Cu2Fe with copper, which reduces the copper content in α(Al) and decreases the strength of the alloy, and should be strictly controlled. Si reduces the high-temperature (300°C) permanent strength of the alloy and is a harmful impurity.
Heat treatment characteristics
The remarkable characteristics of 2219 alloy are: high thermal strength, low temperature performance, long-term use at -270 °C ~ 300 °C, the use of a large span of temperature, ranking first in aluminum alloy; extrusion material has no squeeze effect. These alloys have little natural ageing effect but have significant artificial aging power. In the artificial aging state T6, there are both high strength, heat resistance, and solderability.
The solution treatment temperature of this alloy is 520°C~535°C, and the artificial aging specification is 160°C~170°C/(10~16)h. In the solution treatment, two opposite processes are performed in the alloy: one is the alpha (Al)+Al2Cu binary eutectic and the ternary eutectic alpha (Al)+Al2Cu+T (Al12CuMn2) solid solution in alpha (Al) The second is to precipitate the Mn-containing phase T (Al12CuMn2) from α(Al), which is dispersed in a spot-like manner in the α(Al) base. The α(Al) obtained after quenching is supersaturated, and Al2Cu and T phases precipitate during artificial aging to strengthen the alloy.
At high temperature, not only the T-phase itself has higher microhardness than Al2Cu, but also its softening percentage is lower than that of Al2Cu under high-temperature long-term load. T-phase can also significantly increase the high-temperature permanent hardness of the alloy. The T phase is much more stable than Al2Cu at high temperatures and does not aggregate easily.
Good low temperature performance
In aluminum alloys, the 2219 alloy has a long-standing reputation for its low temperature performance, and liquid hydrogen and liquid oxygen tanks are the best. 2219-T62 alloy tensile strength at 25 °C Rm = 400N/mm2, and -195 °C when the 505N/mm2, increased 26.25%, 25 °C elongation A = 12%, -195 °C However, it rose to 16%, an increase of 33.33%. As the temperature decreased, the strength and temperature increased synchronously. It is very commendable, as shown in Table 2.
2219 Alloy Typical Performance
2219 alloy thin plate (thickness ≤ 6mm) is coated with a thin layer of 7072 alloy (Cu0.10, Mn0.10, (Si+Fe)0.70, Zn0.80~1.3, Mg0.10, other impurities each 0.05, a total of 0.15, the rest is Al) to improve its corrosion resistance.
Typical uses: Intercontinental rocket and spacecraft rocket welding oxidant tank and fuel tank, supersonic aircraft skeleton and structural parts. Application temperature -270 °C ~ 300 °C. High fracture toughness, T8 material limited high stress corrosion cracking resistance. Typical tensile properties of various state materials are shown in Table 3.
The fatigue strength of the RR molar test of 5 x 108 cycles was 103 N/mm2. Physical properties: Density 2840kg/m3 at 20°C, liquidus temperature 643°C, melting point of low melting point eutectic starting at 543°C, linear expansion coefficient: 20.8μm/(m·k), 20°C at -50°C~20°C 22.5 μm/(m·k) at ~100°C, 23.4 μm/(m·k) at 20°C to 200°C, 24.4 μm/(m·k) at 20°C to 300°C, and a volume expansion coefficient of 6.5×10- 5m3/(m3·k); specific heat capacity at 864J/(kg·k) at 20°C; thermal conductivity: 170w/(m·k) at O-state material, 116w/(m·k) at T31 and T37, T62 130w/(m·k) of the T81, T87, and T87 states.
Conductivity: equal volume rate at 20°C, 44% IACS for O state, 28% IACS for T31, T37, T351 state, 30% IACS for T62, T81, T87, T851 state. Resistivity: 39nΩ·m in the O state at 20°C, 62nΩ·m in the T31, T37, and T351 states, and 57nΩ·m in the T62, T81, T87, and T851 states. The temperature coefficient of resistance of various materials is 0.1nΩ·m/k at 20°C. The potential of 0.1N calomel electrode in 53 g NaCl and 3 g H2O2 aqueous solutions at 25° C. is −0.64 V for T31, T37, and T351 state materials, −80 V for T62, T81, T87, and T851 states. (Wang Zhutang)
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