Forging

Application of precision forgings in aerospace

Precision forging technology has a wide range of applications in the aviation industry, and is mainly used to manufacture key components in aircraft that are subjected to alternating loads and concentrated loads. For example, it is used to manufacture the main load-bearing parts such as aircraft fuselage structure, engine rotating parts and landing gear. The quality of parts made of forgings accounts for about 20% to 35% of the total mass of the aircraft body structure and 30% to 45% of the total mass of the engine structure. It is an important factor that determines the performance, reliability, life and economy of aircraft and engines. one.

Application of precision forgings in aircraft fuselage structure

Precision forgings are widely used in aircraft fuselage, such as engine frame, door frame, fuselage frame beam, wing frame beam, joints and other parts, the specific distribution is shown in Figure 1. Among them, the fuselage bearing frame beams, wing frame beams, joints and other parts are mainly die forgings produced by die forging, and the materials are mainly titanium alloys, aluminum alloys, and structural steels. At present, the characteristics of aircraft fuselage structural forgings are outstanding: complex structure, large projected area, and difficult forming; and in recent years, the number of new materials used has increased, and the requirements for its structure, fracture toughness and fatigue strength are improving. .

Application of Forgings on Landing Gear

Whether it is a military aircraft or a civilian aircraft, the landing gear is a vital part. In the process of frequent take-off and landing of the aircraft, the landing gear of the aircraft has to bear a large impact load. Therefore, the requirements for the structure and performance of forgings are higher, and the metallurgical process and precision forging process of structural materials need to be strictly controlled.

Aircraft landing gear is mainly produced by die forging, and its die forgings have the characteristics of large size, complex structure and large projected area. The material is mainly high-strength structural steel and high-strength and high-toughness titanium alloy, which has great deformation resistance during processing. There are high requirements for the uniformity, impact resistance and fatigue resistance of forgings.

300M steel forgings for aircraft landing gear

The application of precision forgings in the key parts of the engine

The compressor disc, turbine disc, spacer, sealing ring, integral blisk, dual performance disc, turbine shaft, fan shaft and other key parts on the aircraft engine are prepared by forging technology.

Distribution map of forgings in aero-engine

The materials selected for the forgings used in the manufacture of aero-engines are mainly superalloys (including powder superalloys), titanium alloys and steels, and their comprehensive properties (high temperature, normal temperature mechanical properties) and microstructure uniformity are required to be high. The main features of the machining process of these precision forgings are the large deformation resistance of the material and the difficulty in process control.

Aero engine forgings

Application of titanium alloy precision forging in aerospace field

In the application of various titanium alloy products, precision forgings are mostly used in applications requiring high strength, high toughness and high reliability, such as gas turbine compressor discs and medical artificial bone. Therefore, not only high dimensional accuracy is required for precision forgings, but also materials with excellent properties and high stability are required. To this end, the characteristics of titanium alloys should be fully utilized in the manufacturing process of titanium forgings to obtain high-quality forgings. Titanium alloys are difficult to forge and are prone to cracks. Therefore, the most important thing in the production of titanium alloy forgings is to properly control the forging temperature and plastic deformation.

1. Application fields of titanium alloy precision forgings

1) Aerospace

50% of the titanium in the world is used in the aerospace field. 30% of the body of military aircraft uses titanium alloys, and the amount of titanium in civil aircraft is also gradually increasing. According to reports, the amount of titanium used in Boeing 787 aircraft has reached more than 15%. The representative of the titanium alloy used in the body is the Ti-6AI-4V alloy, which has the highest reliability. The near-type high-strength and high-toughness titanium alloy Ti-10V-2Fe-3AI has been used in the landing gear parts of Boeing 777 aircraft, and A380 has been discussing the use of large forgings of Ti-10V-2Fe-3Al alloy as the transmission device of the main landing gear.

If practical, this would be the largest titanium forging at 7m. In aircraft engines, titanium alloys are also indispensable materials, mainly used for fan and compressor parts with temperatures below 853K. Typical use parts are fan blades, casings, discs, compressor blades, discs, stub shafts, casings, etc. The titanium alloys used are Ti-6AI-4V, Ti-6AI-2Sn-4Zr-6Mo, Ti-5Al-2Sn-2Zr-4Cr-4MbTi-17), Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5 Mo-0.35S and so on. In the aerospace field, titanium alloy forgings are used in fuel tanks for rocket and satellite propulsion engines, attitude control engine housings, vanes for liquid fuel turbo pumps and inlet sections for suction pumps. Most of these parts use low-interstitial elemental Ti-5Al-2.5SnELI alloys with excellent low-temperature toughness.

2) Turbine blades for power generation

Increasing the blade length of the steam turbine of thermal power generation is an effective measure to improve the power generation efficiency, but the lengthening of the blade will increase the load of the rotor. The use of titanium alloy forgings as blades can reduce the load, and the use of 1m long Ti-6Al-4V alloy blades at the end of the high-speed rotating steam turbine has been practical in 1991.

2. Forging technology of titanium alloy

In the hot working of titanium alloys, the heating temperature is very important. The lower the temperature, the greater the deformation resistance, and it is easy to produce cracks and other defects. At the same time, it also has a great dependence on the deformation speed, which should be paid special attention to in forging. In the process of precision hot die processing of titanium alloys, heating the temperature of the forging die to a temperature equal to or higher than that of the forging can suppress the decrease in the temperature of the forging during forging. Due to the high deformability of this method, thinner-walled precision forgings can be forged with fewer heating times. However, this method needs to use expensive Ni-based or Mo-based superalloys, and the production efficiency is low, so it faces a big problem in economy.

1) Forging technology of engine disk parts

Discs for aircraft engines require high fatigue strength and fracture toughness. Ti-6Al-2Sn-4Zr-6Mo alloy forgings are used in the medium temperature region around 700K. The traditional processing method is forging in the a-zone, and its microstructure is phase and equiaxed a grains and fine acicular a two-phase structure, and the fracture toughness value is low. To improve this, a forging method with zone heating was developed. The forging method is to heat and forge above the phase transition temperature, which will cause recrystallization. Therefore, the forging temperature and processing deformation have a great influence on the material properties, and it is not allowed during forging.

Deformation is stopped by reheating. Therefore, the forging temperature and the amount of deformation must be strictly controlled in B forging. For Ti-6Al-2Sn-4Zr-6Mo alloy, the processing temperature is in the range of 10731323K, and there must be enough processing deformation. The forging structure is all needle-like, and the fracture toughness value is increased from the original 30MPa*m1/2 to 50MPa*m1/2.

2) Turbine blade forging technology

Turbine blades are very thin, and the temperature drops quickly during the forging process. Generally, they are forged with a screw press with a fast reduction speed and a large single processing energy. During hammer forging, the blowing lateral force is generated due to the twisting of the shape of the blade, so the die should be precisely designed. Currently, a process is being developed to effectively utilize the energy of the upper and lower blows to form the blade surface. First, flat forging is performed, then bending is performed, and finally precision forging is performed.

3) Ring manufacturing technology

Large Ti-6A1-4V alloy rolling rings are used for the engine fan casing and the compressor casing. For titanium alloy products with relatively high material costs, reducing the amount of material input is very effective in reducing costs, especially the near-net-shape technology is more effective. Taking the V2500 engine fan casing as an example, the material consumption of the near-net-shape parts is reduced by more than 55% compared with the machining of the ring parts.

When processing thick rings, in order to avoid cracks, compressive stress should be given as much as possible, and attention should be paid to the control of the structure and the temperature drop of the rings during processing.

In short, the production of titanium alloy forgings requires proper processing temperature and proper deformation to obtain high-quality forgings.