Views:67 Author:Ronsco Publish Time: 2021-05-08 Origin:Nickel Alloy Knwoledge
According to the forging characteristics of special alloys and the use characteristics of forging equipment, the adaptability of common forging equipment to the forging of special alloys can be summarized as follows:
Upper die forging with die forging hammer is the earliest developed die forging method. Although a variety of new die forging equipment and die forging process methods continue to appear, the upper die forging of the forging hammer is flexible, adaptable, metal is easy to fill the die cavity, single die cavity and multi die cavity die forging, and the equipment is low in price. Advantages, therefore, it still occupies an important position in the production of die forgings. However, the upper die forging of the forging hammer also has its disadvantages that are difficult to overcome, such as large noise and vibration, environmental pollution, and poor working conditions. Because of the high speed, it is not suitable for forging special alloys with low plasticity.
The speed at which the die forging hammer (including the counter hammer) starts to strike the forging is 4m/s～8m/s, which is an impact load. The hammer head has a high striking speed and large changes. It is not suitable for forging special alloys with low plasticity and slow recrystallization speed. , Special alloys whose plasticity is not too bad, can also be forged on die forging hammers and counter hammers, but the heating temperature is different from that of press die forging. In addition, the forging should be lightly hit at the beginning, and then gradually increase the hammering force, and strictly control the deformation of each hammer. The deformation of the last hammer of the final forging process is especially important to avoid uneven grain structure.
Forging hydraulic presses are divided into three types: free forging hydraulic presses, die forging hydraulic presses and extrusion hydraulic presses. Free forging hydraulic presses are divided into ordinary free forging hydraulic presses and rapid forging hydraulic presses. Free forging hydraulic presses (3MN～160MN) are mainly used for the production of ingots of various materials and large and super large free forgings. The rapid forging hydraulic press (working stroke speed can reach 0.3m/s) generally has a small tonnage and is mainly used for billeting and billet making of special alloy ingots.
The nominal load of die forging hydraulic press is mostly in the range of 8MN～750MN. Compared with other die forging equipment, die forging hydraulic press has a low working speed (working stroke speed is about 0.1m/s or lower), controllable, and stable action. The equipment continuously supplies energy throughout the working stroke to keep the loading speed basically No change, especially suitable for die forging of special alloys that are sensitive to deformation speed; long working stroke, suitable for forging processes with a large amount of deformation in one stroke, such as extrusion and upsetting. However, the long working stroke of the die forging hydraulic press leads to a long loading time, large wear of the die and easy chilling of the forging, which are also disadvantages.
Small and medium-sized die forging hydraulic presses are mainly used for die forging aluminum alloy, magnesium alloy and copper alloy forgings. Large-scale die forging hydraulic presses above 10,000 tons are mainly used for die forging large-scale special alloy structural parts, for example, large-scale aluminum alloy structural parts of aircraft, titanium alloy frame, joints and beams of aircraft, and engine compressors of high-temperature alloy and titanium alloy. Disks and turbine disks, etc.
The idle stroke speed of the mechanical press is relatively high, while the working (loading) speed is relatively low (below 0.3m/s), and the action is stable. The equipment completes one process at one stroke, so it is suitable for die forging of high-temperature alloys and titanium that are sensitive to deformation speed. alloy. Because the equipment has large rigidity and high degree of rigidity, and is equipped with precision die holders and upper and lower ejector devices, it can die forgings with small forging inclination and high precision. Mechanical presses are mostly used for mass production of high-temperature alloy and titanium alloy blade die forgings, precision forgings and other small and medium-sized structural parts. Modern mechanical presses such as wedge transmission and yoke type have high rigidity and are equipped with load display devices, which are especially suitable for mass production of precision forgings.
The screw press combines the working characteristics of the forging hammer and the press. Its speed-stroke curve is similar to that of a forging hammer. It is loaded at the highest speed point of the entire stroke, but because its highest speed is generally not higher than 1.2m/s, and it can perform repeated blows with different degrees of deformation, it has a wide range of uses and also Suitable for die forging or precision forging of special alloy blades and structural parts, as well as forgings such as engine compressor discs and turbine discs. The actual striking load of the screw press can reach 1.6 to 2.0 times of its nominal load, which is especially suitable for the precision forging of thin-walled forgings.
The main basis for selecting forging equipment is the technical requirements of the forgings (such as projected area, thickness (height), shape, complexity, precision, etc.), material characteristics, and the company's existing equipment conditions.
Commonly used various forging equipment can meet the requirements of ordinary structural steel forgings, and can be selected most economically according to the company's existing equipment status and the batch of forgings. But for special alloy forgings, the plasticity of the material and the requirements for the structure and performance of the forging have become an important basis for equipment selection. E.g:
1) Aluminum alloy, magnesium alloy and copper alloy forgings
The preferred forging equipment for aluminum alloy, magnesium alloy and copper alloy forgings is hydraulic press (especially for large die forgings). For medium and small aluminum alloy die forgings, in addition to hydraulic presses, mechanical presses or screw presses are often used. In the absence of the above equipment, a forging hammer can also be used, but at this time, it should be operated in strict accordance with the regulations of the process to avoid cracking and uneven organization of the forging.
2) Titanium alloy
It is recommended to use hydraulic press to die forging large titanium alloy die forgings. Small and medium-sized titanium alloy die forgings are forged with mechanical presses and screw presses. In the absence of the above-mentioned equipment, a forging hammer can also be used, but at this time, it should be operated in strict accordance with the regulations of the process to avoid unqualified organization and performance.
The forging of stainless steel forgings is generally not limited by the type of forging equipment.
4) High temperature alloy forgings
For large high-temperature alloy die forgings, such as turbine disks, hydraulic press die forging is recommended. For small and medium-sized high-temperature alloy die forgings, mechanical press die forging is recommended; screw press die forging can also be used, and die forging hammer die forging is generally not recommended.
1) Large die forgings
For high-temperature alloy, titanium alloy and aluminum alloy large die forgings, hydraulic press die forging is recommended. For large-scale structural steel and stainless steel die forgings, due to economic reasons, hammer and die forging are generally selected; for extra-large structural steel and stainless steel die forgings, hydraulic press die forging is recommended.
2) Small and medium-sized die forgings
For high-temperature alloy, titanium alloy and aluminum alloy medium and small die forgings, mechanical press and screw press are recommended for die forging. Titanium alloy medium and small die forgings can also be forged with forging hammers. Small and medium-sized die forgings of structural steel and stainless steel are usually forged with forging hammers. Depending on the batch size and existing equipment, mechanical presses or screw presses can also be used for die forging.
1) Forgings with large thickness and large blank height
The hydraulic press is suitable for forging processes with long working strokes of various materials, for example, the forgings of special alloy turbine discs with a large amount of reduction in the upsetting and die forging processes, and the extrusion or punching where the load is almost constant throughout the long working stroke. Process.
2) Thin forgings
Die forging hammers and screw presses are suitable for die forging thin forgings, but die forging hammers are limited to die forging stainless steel and titanium alloy forgings. Mechanical presses and screw presses are suitable for die forging high-temperature alloy, titanium alloy, stainless steel, aluminum alloy, magnesium alloy and copper alloy forgings.
1) High-precision forgings
Mechanical presses and screw presses are suitable for precision die forging titanium alloy and stainless steel blades, as well as small and medium-sized forgings such as aluminum alloy, magnesium alloy and copper alloy.
2) Forgings with general precision
Hydraulic presses and forging hammers are suitable for forging common die forgings with general precision.
1) Large batch
Mechanical presses are most suitable for the production of high-volume die forgings such as automobiles, agricultural machinery, medical equipment, hardware tools and other parts and aero engine blades.
2) Medium batch
Forging hammers and screw presses are suitable for die forging of medium batch forgings.
3) Small batch
The hydraulic press is suitable for the production of small batches of large die forgings.
The above suggestions for selecting forging equipment are only based on the characteristics of the forging equipment and the characteristics of the forgings. However, the selection of forging equipment is very complicated. In addition to the above selection principles, the status of the company's existing equipment, the history of the equipment used by technicians and workers, and the familiarity of the equipment should also be considered. The specific selection equipment for a certain special alloy forgings generally only meets a few main principles.