When we talk about metal spinning, many people are not unfamiliar with it. Metal spinning is widely used in the civilian field, we can see the presense of spun products in both home and hotels settings, such as lamp shadow, stainless steel tableware, bottle, vase. Many people are confused what fields and components metal spinning can process in the aerospace. Thin-wall rotary shell components manufactured by spinning forming technology can solve the technical problems of low stiffness, large vibration, low machining precision or impossible to process during CNC turning, metal spinning have many advantages in aerospace field.

Space X and Musk

Talking about Aerospace, most of people immediately think of SpaceX and Musk, Space X（Space exploration technologies corporation）is an American private space company founded in 2002 by Elon Musk and headquartered in Hawthorne, California. Space X was founded to reduce the cost of space transportation, advance the reuse of rocket technology, and eventually achieve the goal of human colonization of Mars.

Maybe someone will ask the Musk team make the space X, what the CNC metal spinning machine they used or where the CNC metal spinning machine. At first, the editor was also very curious, and in an attitude of learning, the editor specifically checked the picture on the official Twitter account of space X, we find the CNC metal spinning was designed and assembled by themselves, compare to rocket manufacturing, a CNC metal spinning machine tool is so simple for Space X team. At the same time, we have to sincerely admire the technical ability of Musk's team and its contribution to the development of science and technology.

There are plenty of Space X launch videos and factory footage on the Internet. It makes aerospace manufacturing and technology less mysterious. Of course, aerospace and aviation technology is still very advanced technology. Metal spinning also plays an indispensable role in these areas. Let us now take a closer look at metal spinning applications and materials in the field of aerospace and aviation.

Aerospace and aviation

1. Rocket nozzle

Nozzle is an important component of rocket engine. It is a device that accelerates airflow by changing the geometry of the inner wall of the tube. All the pipes used to make the air pressure reduction growth rate are called nozzles, and there are two types of nozzles commonly used in thermal power generation: one is a shrinking nozzle, and the other is a scaling nozzle, or a Laval nozzle. The materials of nozzle is nickel-base superalloy, it is also called Inconel. Inconel metal spinning performance is worse than stainless steel 304, it need to spin by heating. The turning performance is poor because of high hardness and sticking turning tool.

2.Combustion chamber

It is a device in which the fuel or propellant is burned to produce high temperature gas, and is a combustion equipment made of high temperature resistant alloy materials. The fuel is burned in this chamber. It is an important component of gas turbine engines, ramjets and rocket engines. It is used by superalloy to hot spin, hot forging, superalloy is hard to form by cold working, it is hard to control the tolerance as the springback is bigger than stainless steel.

3. Airplane nozzle

The main function of the tail nozzle is to make the gas after the turbine continue to expand, fully transform the remaining enthalpy in the gas into kinetic energy, so that the gas is expelled from the nozzle at a high speed. The nozzle is used Inconel to make commonly, inconel needs hot spinning to form.

4. Fairing

It is used to protect the satellite and airplane from harmful environmental effects such as air power, aerodynamic heating and acoustic vibration. It is an important part of the launch vehicle.  Airplane, rocket, missile have the fairing components, airplane use the aluminum 2024, missile is used the 5A06 material.

5. Missile housing

Missile housing are made by flow forming, it need to make a forging blank, then put it in a three roller machine, flow forming can improve the accuracy and tensile strength of the structure, compare to traditional CNC turning, flow forming can process it without remove the materials, the accuracy and tensile strength is better.

6. Airplane fuel tank

Airplane fuel tankis commonly used the aluminum 5A06, at first, the aluminum density is light. Second ,the tensile strength is high. Third, it has Excellent corrosion resistance.

7. Oxygen tank

After the aircraft starts the main engine, it automatically shuts down the APU, and the high-pressure compressor section of the engine enjects air into the cabin to provide oxygen for passengers. In addition, the existing engine technology is very reliable, and rarely stops in the air, but for the sake of safety, there are three sets of backup oxygen systems for civil aircraft! In both cases, the backup oxygen system will be activated, the first is the aircraft body ruptures, the cabin loses pressure, oxygen supply is not guaranteed, and the second is the engine stops, can not continue to provide oxygen to the air conditioning, in both cases, the backup oxygen will provide enough flight life time until the aircraft descend to a safe enough altitude.

8. Hydraulic tank

Why use liquid hydrogen as the primary fuel for spacecraft? Hydrogen is easily burned in the air, in addition to nuclear fuel, hydrogen is the highest heating value of all fuels (including fossil fuels, chemical fuels and biofuels, etc.). The heat produced by burning each kilogram of hydrogen is about the same as that produced by burning 4.5 kilograms of coke, 3 kilograms of gasoline or 3.9 kilograms of alcohol. 

Hydraulic tank is made by necking spinning with heating, the materials is aluminum 6061, when finished spinning tank, its exterior will be wrapped in carbon fiber, it improve the tensile strength greatly. Except the rocket use the hydrogen tank, the automobile ,bus use the hydrogen tank, Hydrogen energy is burned to produce water, it is benifit for environment .

What materials is used in aerospace and aviation 

1. Aluminum alloy: 7075

The aerospace components requirement is strict, it need to meet excellent mechanical properties ,at first, it is very light, the metal materials are light with ultra high strength aluminum aluminum 7075 has the best tensile strength in all the aluminum types. It has a high strength below 150ºC and a particularly good low temperature strength. Aircraft parts, gears and shafts.

2. Aluminum alloy: 2024

Aluminum 2024 has high strength, certain heat resistance, and can be used as working parts below 150ºC. At temperatures above 125ºC, the strength of the 2024 alloy is higher than that of the 7075 alloy. The formability in hot state, annealing state and new quenching state is better, and the heat treatment strengthening effect is remarkable, but the heat treatment process is strict. Aluminum 2024 is used in the aircraft covering.

3. Aluminum alloy : 5A06

5A06 aluminum sheet has high strength and excellent corrosion resistance, especially suitable for engineering applications requiring high strength and good corrosion resistance‌. the missile shell and aircraft fuel tank use this material, it just can be shearing and cold spinning, it has excellent welding performance, tensile strength after welding can reach 95% of the base material.

4. Inconel 718 and Inconel 625

Inconel 718 is a precipitation-hardened nickel-chromium ferroalloy containing niobium and molybdenum, which has high strength, good toughness and corrosion resistance at high and low temperatures at 700℃. The supply state may be in solution treatment or precipitation hardening state.

Inconel625 alloy is a solid solution strengthened nickel-based deformed superalloy with molybdenum and niobium as the main strengthening elements. It has excellent corrosion resistance and oxidation resistance. It has good tensile and fatigue properties from low temperature to 980℃, and is resistant to stress corrosion under salt spray atmosphere. Therefore, it can be widely used in the manufacture of aerospace engine components, aerospace structural components and chemical equipment. The alloy is used in the manufacture of engine casing, guide blade, mounting edge and barrel, fuel manifold and other parts, and has passed the practical application test, the highest operating temperature is 950℃.

5. Superalloy

Aerospace engine, known as the "flower of industry", is one of the most technical and difficult components in the aviation industry. As an aircraft engine, it is particularly important for metal structural materials to have light weight, high strength, high toughness, high temperature resistance, oxidation resistance, corrosion resistance and other properties, which is almost the highest performance requirements in structural materials.

Superalloy is a metal material that can work for a long time above 600℃ and under certain stress conditions. Superalloy is developed to meet the harsh requirements of modern aero-engine materials, and has become an irreplaceable key material for aero-engine hot end components. In advanced aero engines, the proportion of superalloy has reached more than 50%. In modern advanced aircraft engines, the amount of superalloy materials accounts for 40% to 60% of the total engine. In aero engine, superalloy is mainly used for combustion chamber, guide blade, turbine blade and turbine disk four hot parts. In addition, it is also used for parts such as case, ring, afterburner and tail nozzle.

As we know, Superalloy (High temperature alloys refer to those based on iron, nickel, and cobalt) has super high temperature, high pressure and corrosion resistance, the highest use temperature can reach 1200℃ or more, often used in the aerospace field. It is hard to form by cold spinning. We commonly need to heating by propane, propane heating is more uniform and has high temperature.

6. Titanium alloy precision spinning technology

The φ3900mm large missile shell produced by flow spinning in the United States has a radial dimensional accuracy of 0.05mm, a surface roughness of 1.6~3.2μm, and a wall thickness difference of less than 0.03mm. The American Titanium Manufacturing Company uses a 1.5m vertical spinning machine to spin φ1524mm Ti-6Al-4V titanium alloy missile pressure vessel head, and the spinning time of each head is 5min. Minuteman intercontinental missile second stage solid motor shell using Ti-6Al-4V titanium alloy, titanium alloy shell weight reduced by 30% after shearing forming. Around the space model for light, high strength, large space needs, the German MT Aerospace company using spinning process to prepare φ1905 mm high-strength Ti-15V-3Cr alloy propulsion system storage tank, and applied to the European Alpha communication satellite giant platform, to achieve a significant reduction in the weight of the satellite platform and increase the payload.

China's spinning process and equipment research originated in the early 1960s, titanium alloy spinning research began in the 1970s, after more than 40 years of development, the basic formation of a mature system from the development of equipment to process development. Titanium alloy and spinning products used in domestic aerospace, such as rocket engine shell, blade cover, gyroscope guide cover, inner skin, etc. Ti8Al1Mo1V high titanium alloy is used for engine blade heat treatment to strengthen titanium alloy spinning forming; TB2 titanium alloy is used for small nozzle spinning.