The Research On Facility And Technique Of Forming Connecting-rod Billet In Cross Wedge Rolling Processing

As is well known, axial-symmetry bar-piece has a important position in the field of machine work and tools. And as a typical axial-symmetry forging, connecting-rod is the important component part of transference dynamic in engine, the quality of connecting-rod has a direct effect on the safety use and run of the engine or even the all automobile. It transfers the guiding of piston to the rotation movement of crankshaft, and at the same time transfers the force of piston to crankshaft. During this time, there are manifold complicated and cyclic variation forces which contain tension, compression, to-and-fro inertia force and gas pressure etc on connecting-rod.At present, the process of automotive connecting-rod is almost forging, its technological process includes baiting, heating, body billet, dummying, finish forging, flash trimming and shaping etc. Cross wedge rolling machine, forging hammer and forge rolling machine are widely used in body blank. Friction press, die hammer and hot drop press are usually used in dummying and finish forging procedures.There are a bit of defect on acailable plasticity forming technique when they come to processing the initial billet of axial-symmetry bar-piece: die forming on hammer has the default of low service life of die, great impulsive noise, heavy intensity of labor; forge rolling has the virtue of low equipment investment, long service life of die and high capacity usage ratio. But because there are no die constraints on the longitudinal warping of workpiece in forge rolling, it will produce forward slip and rearward shift and this had a strong impact on the quality of body blank. Moreover, all of the above have the default of big fash and low utilization rate of materials.Cross wedge rolling is one of the advanced forging press which develop in 1960s, it is a processing technology of few or no cutting. Compare with the traditional technology of forging and cutting, it has the advantage of high utilization rate of materials, adequate quality of forming and long service life of die etc. But as one of the advanced manufacturing engineering, cross wedge rolling forming technique also has the inevitable default and shortage. At the aspect of equipment, the roller cross wedge rolling machine has the virtue of good toughness, but it has complex process of die and poor precision of component part. Further more, it has some difficult on rolled the stepped shaft which has big diameter and long length. Although the process of die is simple in flat cross wedge rolling, it has poor toughness. At the aspect of technology, in the deformation process of cross wedge rolling, because there are no axial extension in the center of cylinder billet and the maximum axial extension is in the external surface, and this takes the interfacing which deformation is inhomogenous, so here comes default, such as the restriction crack of interfacing, the concave bit of end head and so on, which will weaken the strength of materials of workpiece, and lead to part failure. In addition, the technology of traditional cross wedge rolling is that rolled the thick rod to thin, but when come to the part whose sectional plane changed greatly, such as connecting-rod, it needs very thick bar stock to form the pin. Because of the large percentage reduction in area, it must be rolled multistep. And this is difficult to ensure the continuance and stability of forming, moreover, it also has the defect of low forming efficiency, big space of die, hardness on design and machining, high facility request.To solve the above problems in the traditional forging process of automotive connecting-rod, my tutor professor Song has put forward a plan to solve the equipment problems as first step. He has devised plate precise cross wedge rolling machine and precise plastic rolling machine innovation. These creative ideas can effectively conquer slipping forward and backward in roll forging process, poor stiffness of plate cross wedge rolling machine and low accuracy in cross wedge rolling process by using cross wedge rolling mill. Based on these solutions on equipments, he has creatively put them into automotive connecting-rod precise plastic forming and devised a new process named as automotive connecting-rod precise plastic rolling process. This process can efficiently solve a series of problems in the traditional connecting-rod forging process.This thesis is an important part of my tutor-professor Song's research field on automotive connecting-rod precise plastic rolling process. It based on advanced design works on the core equipments of the process, strictly according to the patent automotive connecting-rod precise plastic rolling process and equipment. On the precondition of improving the forming quality and utilization rate of materials, designed the die which is used in prepare the connecting-rod billet in cross wedge rolling. And also based on experiment requirement, we designed flat cross wedge rolling machine. Because this process is technology innovation, its design method and scheme can't copy the traditional connecting-rod forging process. The work in this thesis is only elementary R&D on the design scheme and method. It needs a lot of profound and successive work to be done in order to put this process into practice.Based on profound comprehension about the traditional forging process of automotive connecting-rod, strictly according to the patent idea of automotive connecting-rod precise plastic rolling process, the thesis takes an existing connecting-rod forging as study object. By studying the die and experimental equipment of cross wedge rolling in connecting-rod body billet, it concludes the proper design scheme and method suit to this forming process. Main work in this thesis is listed as following. At first, improved develop the flat cross wedge rolling experiment machine and gain the aim that moved more stable and uniform speed, moreover, it comes to simple automatic. This provides practical experimental equipment for simulation experiment of auto connecting-rod body billet. Using the volume measuring instrument of arbitrary shape workpiece in my tutor-professor Song's patent to gain the volume of connecting rod. In according to the patent idea, we adopt a newly connecting-rod figure in article, that is using whirl flat polyhedron instead of round bar, and this bring up higher require for CWR die design. Another innovation of automotive connecting-rod precise plastic rolling process is that make the best of gather materials function of CWR and choice thinner billet to forming more reasonable connecting-rod initial billet. The innovation of above technical is that it not only using major diameter billet to form steel bar, but also squeezing the excess stock of detail to butt end by the gather materials function of CWR, and this is the difficulty of technological design. In the process of die design, according as the connecting-rod dimension which are calculated above, work out the connecting-rod initial billet die of CWR. At last, use numerical simulation to simulate the operation of rolling of this new technology. By the research of simulation experiment gained perfect result.Base on designing die and experimental equipment, gained the process improvement method in traditional process. And achieved the aim of improved workpiece quality and improved production efficiency. In the process of putting automotive connecting-rod precise plastic rolling process into practice, the scheme and method in this thesis are valuable reference.