The New Equipment And Technology On Cross Wedge Rolling Precision Performing Of Railway Axles

The successive partial plastic forming is an important aspect of the field of materials processing. It is the overall shape into a local deformation of a continuous cycle of accumulation, reducing the instantaneous deformation area and the total forming force. This technology has the advantage of the static pressure forming(Shock, vibration, and hazardous to the environment is very small), the high utilization rate of energy, stable production quality, easy to implement mechanization and automation, high production efficiency, fully exploited the potential capacity of plastic metal, etc. The cross wedge rolling (CWR) technology belongs to successive partial plastic forming technology.The CWR forming process is a metal successive partial plastic forming technology developed in recent decades at home and abroad. In the field of metallurgical processing, it is an evolution from the equal cross-section rolling to the non-equal crosssection rolling. In the field of mechanical processing, the overall successive partial plastic forming is an improvement to the subsection integral plastic forming.CWR, with the advantages of high material utilization, high energy efficiency, high production efficiency, automation and no impact noise. It occupies an important position, and has a good development prospect in modern net-shape forming and green machining technology.Railway axle is the key components of the train. It is one of three key components of the railway industry. It endured the vehicle weight and load. When the train is running and parking, it also withstand impact and braking force. In high-speed and overloading of the state, Its situation of force is more complex. Railway axles is the very large axisymmetric and ladder shaft parts. Its maximum diameter about 200mm, Its length about 2200mm.At present, the forming process of railway axle are mainly two kinds of free forging and precision forging process. Railway axles were formed by the free forging process using the drop-down quick forging hydraulic press, and were forged with slower velocity relatively. The forming time of a axle need 8-10 minutes. However, the internal of axis is prone to crack. This technology has the shortcomings of low yielding products, multi-consumable materials, next process time wasted, noisy. Railway axles were formed by the precision forging process using the radial forging machine. This technology has the advantages of high process automation, material-saving and energy-saving, high production efficiency, forging a shaft just 3-4 minutes. But it has the shortcomings of forging defects in the center of forgings, better quality of billets, an obvious pit in the end, at the same time its core equipment radial forging machines currently still to import, relatively high cost of equipment, supporting facilities with large investment, required a higher technical level and professionals with higher technical. The researchers of Beijing University of Science and Technology studied the way of multi-wedge on the roll cross wedge rolling to roll the railway axles. But the technology has the shortcomings of complex mold machining process, large equipment, convergence slope prone to the phenomenon of stacked leather, certain uncertainty of internal quality and surface quality.Therefore, the study about the new equipment and technology of railway axle will become necessary because of the existing problems on the railway axle forming technology. With the development of China's railroad industry, because of the railway axle as the key parts of train bogie, railway axle's manufacturing research will also be a hot spot. We have studied how to use the new equipment, new technology, new materials to form railway axles. We make production costs lower, and improve the quality. In order to better serve the development of China's railroad industry to provide technical support.Any kind of manufacturing technology iscomposed of equipment and technology. New requirements for new equipment are being put forward because of the development of new technology, which promotes the development of new equipment. And in turn, new equipment provides important means for implementation of new technology. The development of equipment and technology by supplementing each other forms the historical trunk of the whole manufacture industry. The development of cross wedge rolling is no exception either. Cross wedge rolling equipment are mainly three kinds of arc-shaped cross wedge rolling, the roll cross wedge rolling and plate cross wedge rolling. The roller CWR machine and plate CWR machine are commonly used at present. The roller CWR machine has high rigidity, but the sector dies are difficult to process, and the billet is fed by the conducting plate. Hence, the work-piece produced on the roller CWR machine has poor quality, precision and stability. The dies of plate CWR machine is easy to process, and can be quenched integrally. Hence, the CWR machine has high precision and stability, but poor rigidity.For new equipment, based on the patent " plate rolling plastic precision forming machine", We developed the precision forming machine with rolling plate cross wedge rolling. It absorbs the advantages of roll cross wedge rolling and plate cross wedge rolling, and it has the advantages of high stiffness and simpleness of manufacturing the dies. But there are also difficult to adjust the template. For the shortcomings in precision forming machine with rolling plate cross wedge rolling,the adjustable plate wedge cross wedge rolling was designed, and retained its merits. And the elevating mechanism was installed in the bottom of the template in order to achieve the template distance adjustable. The machine was installed obliquely with easy to oxide skin removal. But it has an empty trip, low energy efficiency, and error of the reciprocating Meshing affect the machining accuracy, and it can not be processed pieces of large-scale axial symmetry. With the development of the heavy automobile and railway industry in China and large shaft parts with ever-increasing demand, development of large cross wedge rolling equipment is very important. Thus, we also proposed one-way successive plate CWR machine. We can know that the one-way CWR machine has the advantages of high rigidity, high forming precision, simple transmission system, high pro-duction efficiency, small floor space and is of convenience to remove roll scale, compared with available CWR ma-chines. Furthermore, it solves the technical difficulties of rolling large stepped shafts. Substituting for traditional forging machines, the machine is suitable for rolling such large stepped shafts as the shaft of rail vehicle and trans-mission shaft of heavy machinery.For new technology, the emergence of new equipment will inevitably promote the emergence of new technology. In traditional cross wedge rolling machine, the railway axles can not be formed with single wedge. Since the emergence of one-way successive plate cross wedge rolling machine, we propose the precision performing technology of railway axle that railway axle in the one-way successive plate cross wedge rolling machine to be formed with single Wedge. The mold has segmented structure in the new technology. The worn mold is easy to replace or repair. The mold life is also greatly increased. As the one-way successive plate cross wedge rolling machine with a long template and characteristics on one-way operation, we use the traditional single-wedge on the wedge-shaped. The technology of single-wedge rolling is relatively mature. The workpiece with high dimensional accuracy, internal quality, and high surface accuracy is formed with the technology.This paper selected typical RD₂ axles to simulate. According to the different contraction ratio of area of the various axle segments, we choose a different forming angle and stretching angle in each section, and design single-wedge segmented rolling die. Under RD₂ axle's rolling die, we proposed a set of physical simulation programs. And we construct physical models, and numerical simulation was conducted. The stress and strain fields were analyzed. We analyzed the technological parameter influence to performance parameter. We analyzed the finishing section's pressure-closed role to reduce and avoid the internal defects. Through analysis of simulation results, we can see that single wedge rolling die can form the railway axle's precision performing in one-way successive plate cross wedge rolling machine. As long as the selection of rational parameters, we can get railway axle's qualified precision performing with good surface quality and none of internal defects. Thus, in one-way successive plate cross wedge rolling machine forming railway axle is feasible.The finishing section of single-wedge segmented rolling die is longer. Rolling force is mainly compressive stress in the finishing section. It belong to hydrostatic deformation mode. Thus, the rolled-piece's internal stress-strain state is changed. It make to reduce the tensile stress, and to increase compressive stress. Thus it can avoid internal defects in cross wedge rolling production. Due to the hydrostatic deformation, it make the metal deformation organization uniform. Internal stress is small. CWR make workpiece continuous deformation, then make fibrous tissue uniform distribution along the axial direction. Thus, CWR improve the quality of the workpiece. Therefore, in the railway axle's forming tecnology on single-wedge rolling, longer finishing segment can improve organizational performance and prevent of internal defects. These are not available in the traditional cross-wedge rolling tecnology.The new railway axle forming technology for the production of the railway axles provides a better alternative. The technology has advantages of high efficiency, material saving, energy saving, good product quality and so on. It is better than the multi-wedge cross wedge rolling, free forging and precision forging. It is an effective technology means on mass production of large shaft in specialization and economization. The advantage of material saving and energy saving is the goal of today's manufacturing industry. With the successful development of one-way successive plate cross wedge rolling machine, it will drive the development of manufacturing processes of large pieces of axial symmetry, and can avoid too large equipment and increase in processing costs caused by increase mold. This will promote the application of cross wedge rolling technology to the wider field forward.