Large forgings are generally used in the key parts of large machinery. Due to the poor working environment and the complexity of the force, large forgings have high quality requirements in the production process. Large forgings are forged directly from ingots. In the production of large forgings, even with the use of advanced metallurgical technology, the ingot internal micro-cracks, loose, shrinkage, segregation and other defects inevitably exist, seriously affecting the quality of forgings. In order to eliminate these defects, improve the quality of forgings, we must improve the forging process, choose a reasonable forging process parameters.

　　Large forgings forging not only to meet the shape and size of the required parts, but also to break the casting organization, refine the particles, uniform organization, forging shrinkage holes, holes, loose and other defects, improve the internal quality of forgings. The larger the size of the ingot, the more serious the defects in the ingot, 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 and an indispensable process, for forgings with special shapes, tire die forging is also more commonly used.

　　I. Upsetting process

　　In the free forging production of large forgings, rolling head is a very important deformation process. Reasonable selection of the header process parameters for the quality of large forgings plays a decisive role. Repeatedly roll head can not only improve the forging ratio of the billet, but also can break the carbide in the alloy steel to achieve the purpose of uniform distribution; can also improve the level of mechanical properties of forgings, reduce the anisotropy of mechanical properties.

　　Large cake forgings and wide plate forgings are mainly head deformation, head deformation is very large, but the current ultrasonic flaw detection rate is very high, mainly due to internal horizontal internal crack layer defects, but the current process theory can not be explained. For this reason, since the 1990s, after a long period of serious research, Chinese scholars from the main deformation zone and passive deformation zone theory, the theory of the head has carried out in-depth research. Proposed rigid plastic mechanical model of tensile stress theory and hydrostatic stress mechanical model of shear stress theory, at the same time, a large number of qualitative physical simulation experiments, the use of generalized slip line method and mechanical chunking method to analyze the internal stress state of the workpiece, a large number of data to prove the reasonableness of the theory and the correctness of the distribution of stress inside the ordinary flat plate cylinders, proposed a new process of rolling cone plate, and the establishment of a rigid Plastic machinery model.

　　Second, the drawing process

　　Drawing long is an essential process in the forging of large shaft forgings, but also a major process that affects the quality of forgings. Through the drawing process, it can reduce the cross-sectional area of the blank and increase the length. At the same time, it can also break coarse crystals, forging internal porosity and holes, refining the casting organization, so as to obtain homogeneous and dense forgings. In the study of flat anvil elongation process at the same time, people gradually recognize the importance of the internal stress and strain state of large forgings on the importance of internal defects in forgings, from the ordinary upper and lower flat anvil elongation to the upper and lower flat anvil under the V anvil elongation and upper and lower V anvil elongation. Later, by changing the shape of the drawing anvil and process conditions, WHF forging, KD forging, FM forging, JTS forging, FML forging, TER forging, SUF forging and the new FM forging were proposed.

　　1.WHF forging is a forging method of pressing down the wide flat anvil strongly. Its forging principle is to utilize the upper and lower wide flat anvil with large pressure rate. The large deformation of the heart in the forging process is conducive to the elimination of internal defects in the ingot, and it is widely used in the forging of large hydraulic presses.

　　2.KD forging method is developed on the basis of WHF forging method. Its principle is to use the ingot in the long-term high temperature conditions have enough plasticity, can be in a limited number of equipment with a wide anvil large underpressure rate forging. Upper and lower V-type wide anvil forging is conducive to improve the plasticity of the metal on the surface of the forging, increase the heart of the three-way compressive stress state, effective forging ingot internal defects.

　　3.FM forging method is to use the upper flat anvil, the lower platform forging asymmetric deformation, the lower platform forging friction resistance, so that the forging from top to bottom gradually deformation, so that the tensile stress is transferred to the blank and the platform contact surface, to increase the center hydrostatic compressive stress, and to improve the deformation of the stress state.

　　4.JTS forging method is to heat the ingot to a high temperature before forging, and then quickly cool the surface, the ingot surface to form a hard shell, the heart is still in a high temperature state, the hard shell fixes the deformation of the billet, so that the deformation is mainly concentrated in the center of the forging, to improve the effect of the heart compaction, and to improve the forging qualification rate.

　　5.FML forging method is a forging method to reduce the load of the press on the basis of FM method. The width of the anvil is narrower than the billet, and the length direction is the same as the axial direction of the billet. The following auxiliary tool remains a large platform. In the process of reforging, the pressure and forging ratio is relatively small, under the premise of ensuring the effective forging of holes inside the billet, under the premise of loosening defects.

　　6.TER forging method uses a wide flat anvil to elongate in one direction, and the wrong anvil process is used to carry out multiple strong pressure elongation, so that the billet produces a large deformation in one direction, and the internal hole defects are forged effectively. Using this method of forging, the pressure is small, forging and forming cycle is short, improve labor productivity, reduce production costs and improve economic efficiency.

　　7.SUF forging method is a forging method that fully reduces the height of the ingot by controlling the anvil-width ratio, and then forges the cross-section into a rectangle. It is a forging method of flattening with a wide flat anvil. Flattening with a wide flat anvil increases the width of the plastic flow range of the metal near the ingot shaft, which is more favorable for forging billets with heart defects.

　　8. The new FM forging method is based on the FM forging method, according to the relationship between the transverse stress in the heart of the forging and the material width ratio, increase the control of the material width ratio, so as to reduce the transverse tensile stress in the heart. Significant economic benefits have been achieved in the production of large forgings using the principles of the new FM forging method.

　　Third, tire mold forging process

　　Tire die forging is a direct use of billet or free forging will billet pre-forged into tire forging required shape and size, and then in the free forging equipment using a tire die for the final forging forging method. Tire die forging is not fixed in the forging equipment, when used on the anvil under the equipment, easy to use, without installation, greatly saving the time of the mold test, the process operation is flexible and varied; because the metal deformation is always completed in the mold room, the shape and size of the forging piece is mainly guaranteed by the tire die, can obtain complex shapes and accurate dimensional requirements, heating fires and deformation process is also reduced, not only to improve the The utilization rate of metal materials, but also reduces the processing time, greatly improving labor productivity. In terms of forging quality, due to the role of the mold, metal deformation is limited, forging organization is dense, forging quality is better, good surface quality, small machining allowances, material utilization is greatly improved, high production efficiency, forging complex shapes; can also be used in small equipment for the production of large forgings, localized molding. Based on the above advantages, tire mold forging has been the attention and favor of many manufacturers.