Large aluminum alloy forging process

Large aluminum alloy forging process

Large forgings are generally used for key parts of large machinery. Due to the poor working environment and complex force, the quality requirements of large forgings in the production process are very high. Large forgings are forged directly from ingot. In the production of large forgings, even if advanced metallurgical technology is used, there are inevitably micro-cracks, loose, shrinkage, segregation and other defects inside the ingot, which seriously affect the quality of the forgings. In order to eliminate these defects and improve the quality of forgings, it is necessary to improve the forging process and select reasonable forging process parameters.
Large forging is not only to meet the shape and size of the required parts, but also to break the casting organization, fine particles, uniform organization, forging shrinkage holes,loosening and other defects, and improve the internal quality of the forging. The larger the size of the ingot, the more serious the defects in the ingot, and the more difficult it is to improve the defects in forging, thus increasing the difficulty of forging. In the forging process, rolling and stretching is a basic process, but also an indispensable process, for forgings with special shapes, tire die forging is also more commonly used.

Upsetting process
In the free forging production of large forgings, the roll head is a very important deformation process. Reasonable selection of roll parameters plays a decisive role in the quality of large forgings. The rolling head can not only improve the forging ratio of the billet, but also break the carbide in the alloy steel to achieve the purpose of uniform distribution. It can also improve the horizontal mechanical properties of forgings and reduce the anisotropy of mechanical properties.
Large cake forgings and wide plate forgings are mainly head deformation, the head deformation is very large, but the current ultrasonic detection rate is very high, mainly due to the internal horizontal crack layer defects, but the current process theory can not explain. For this reason, since the 1990s, after long-term careful research, Chinese scholars have conducted in-depth research on the head theory starting from the theory of main deformation zone and passive deformation zone. The tensile stress theory of the rigid plastic mechanical model and the shear stress theory of the hydrostatic stress mechanical model were put forward, and a large number of qualitative physical simulation experiments were carried out. The generalized slip line method and mechanical block method were used to analyze the internal stress state of the workpiece. A large number of data proved the rationality and correctness of the theory, and revealed the distribution law of the internal stress of the ordinary flat cylinder. A new process of cone-plate rolling is proposed, and a rigid plastic mechanical model is established.

The drawn-out process
Drawing length is an indispensable process in the forging process of large-shaft forgings, and it is also the main process that affects the quality of forgings. The cross-sectional area of the billet can be reduced and the length increased by the drawing process. At the same time, the coarse crystal can be broken, the internal porosity and holes can be forged, and the casting structure can be refined, so as to obtain uniform and dense forgings. At the same time of studying the drawing process of flat anvil, people gradually realize the importance of the internal stress and strain state of large forgings on the internal defects of forgings, from ordinary drawing of flat anvil to drawing of flat anvil and drawing of V-anvil. Later, by changing the shape and process conditions of the drawing anvil, WHF forging, KD forging, FM forging, JTS forging, FML forging, TER forging, SUF forging and new FM forging were proposed.
1.WHF forging method is a forging method of strong pressing wide flat anvil. The forging principle is to use the upper and lower wide flat anvil, the pressure rate is large. The large deformation of the heart in the forging process is conducive to eliminating the internal defects of the ingot, and is widely used in the forging of large hydraulic press.
2.KD forging method is developed on the basis of WHF forging method. The principle is that the ingot has enough plasticity under long-term high temperature conditions, and can be forged with wide anvil and high pressure rate on limited equipment. The upper and lower V-shaped wide anvil forging is beneficial to improve the metal plasticity of the forging surface, increase the three-way compressive stress state of the heart, and effectively forge the internal defects of the ingot.
3.FM forging method is to use the upper flat anvil, the lower platform forging asymmetrical deformation, the lower platform forging friction resistance, so that the forging gradually deforms from top to bottom, so that the tensile stress is transferred to the contact surface between the blank and the platform, increase the center hydrostatic stress, and improve the stress state of the deformed body.
4.JTS forging method is to heat the ingot to high temperature before forging, and then quickly cool the surface, the ingot surface forms a hard shell, the heart is still in a high temperature state, the hard shell fixed billet deformation, so that the deformation is mainly concentrated in the forging center, improve the heart compaction effect, improve the pass rate of forging.
5.FML forging method is a forging method that reduces the press load on the basis of FM method. The width of the cutting board is narrower than the blank, and the length direction is consistent with the axial direction of the blank. The following assistive tools are still a big platform. In the process of reforging, the pressure and forging ratio are relatively small, under the premise of ensuring the effective forging of the internal holes of the blank, under the premise of loose defects.
6.TER forging method uses a wide flat anvil to elongate in one direction, and adopts the wrong anvil process to force and elongate for several times, so that the blank produces large deformation in one direction and effectively forging internal hole defects. With this method, the forging pressure is small, the forging cycle is short, the labor productivity is increased, the production cost is reduced, and the economic benefit is increased.

7.  SUF forging method is a forging method that fully reduces the height of the ingot by controlling the width ratio of the anvil, and then forging the section into a rectangle. It is a forging method by flattening with a wide flat anvil. The wide flat anvil flattening increases the width of the metal plastic flow range near the ingot shaft, which is more conducive to the heart defect of the forging billet.
8. The new FM forging method is based on the FM forging method, according to the relationship between the transverse stress of the forging heart and the material width ratio, increase the control of the material width ratio, so as to reduce the transverse tensile stress of the heart. When the new FM forging method is used to produce large forgings, remarkable economic benefits have been obtained.

Die forging process
Tire mold forging is a forging method in which the blank is pre-forged into the shape and size required for tire forging directly with blank or free forging, and then the tire mold is used for final forging on the free forging equipment. The tire mold forging is not fixed on the forging equipment, and is placed on the anvil under the equipment when used, which is convenient to use and does not require installation, greatly saving the mold test time, and the process operation is flexible and diverse; Because the metal deformation is always completed in the mold room, the shape and size of the forging is mainly guaranteed by the tire mold, and the complex shape and accurate size requirements can be obtained, and the heating fire and deformation process are also reduced, which not only improves the utilization rate of metal materials, but also reduces the processing time, and greatly improves the labor productivity. In terms of forging quality, due to the role of the mold, metal deformation is limited, the forging organization is dense, the forging quality is good, the surface quality is good, the processing allowance is small, the material utilization rate is greatly improved, the production efficiency is high, the forging shape is complex; Large forgings can also be produced on small equipment, with partial forming. Based on the above advantages, tire mold forging has been concerned and favored by many manufacturers.