【作者】 冀东生；

【导师】 夏巨谌；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2011， 博士

【摘要】 齿轮品种多,数量巨大,在汽车、飞机、轮船、机床等产品中应用广泛,尤以各种车辆传动装置中应用最多,其中,一辆汽车上的齿轮近40件,约有一半可采用精密模锻工艺生产。其中,圆锥齿轮、起动齿轮和同步器齿环等已实现精密模锻工艺生产,在节材、节能、提高产品性能和环保方面创造了显著的经济与社会效益。但,结合齿轮、倒档齿轮和大模数直齿圆柱齿轮等结构复杂、成形极为困难的齿轮的精锻技术研究很少见到报导。国外,德国的蒂森克虏伯公司和日本的你期待(Nichidai)公司已研发出结合齿轮和倒档齿轮的温冷复合精锻成形工艺并用于生产,由于技术保密,未见发表论文；对于大模数直齿圆柱齿轮未见公开报导。而国内的研究刚刚起步,有的甚至为空白。本文以实现这些复杂齿轮的精密模锻为目标,采用经典塑性成形理论、有限元模拟与试验相结合的方法对中空分流锻造成形机理及应用技术进行研究,其主要研究内容及成果如下：研究了中空分流锻造成形机理,得到：当采用实心圆饼毛坯通过常规闭式锻造成形为圆饼直齿轮时,毛坯金属以轴向压缩流动为主,径向流动极小,其等效应变值小,但等效应力值大,导致成形力迅速增大,而齿顶未能充满；当采用环形毛坯闭式锻造即中空分流锻造时,毛坯金属产生轴向与径向复合流动,等效应变值增大,等效应力值减小,不仅成形力大为减小,而且齿顶充填饱满。分析了影响锻造成形力的各主要因素及其相互关系,提出了以成形力最小为目标函数的优化模型的思路,导出了中空分流锻造成形力的计算公式和满足中空分流锻造成形要求的环形毛坯孔径的计算公式,实现了环形毛坯的优化设计。采用刚粘塑性与热力耦合有限元模拟方法,分析了采用常规闭式锻造成形结合齿轮精密锻件时,因金属沿径向流动距离过长、切向拉应力过大,从而导致模具破裂和锻件缺陷；针对这一技术难题,提出了中空分流锻造成形工艺方案和预锻件的优化设计方法,完成了三工序结合齿轮中空分流锻造模具结构设计,同样,采用刚粘塑性有限元模拟和工艺及模具试验,验证了其可行性与先进性。针对采用厚壁无缝管坯通过带芯轴挤压成形为大模数直齿圆柱齿轮存在材料利用率低、成形力过大的问题,提出采用圆柱体毛坯通过温(热)态闭式挤压和冷挤压精整的中空分流锻造成形工艺方案,完成了热态闭式挤压和冷挤压精整模具结构设计并提出了相应的选用原则,采用刚粘塑性热力耦合有限元及弹塑性有限元模拟分析与工艺试验验证了其可行性。利用所取得的理论研究成果,在合作企业建立了由下料、加热、16000KN三工位热模锻压力机、热处理炉和6300KN精锻液压机组成的中空分流锻造成形生产线,实现了“大众”二档结合齿轮精密锻件的批量生产,为企业创造了良好的经济社会效益；大模数直齿圆柱齿轮中空分流锻造成形工艺与模具,为相关企业实现汽车驱动桥行星齿轮精锻生产的应用提供了科学依据。更多还原

【Abstract】 There are many kinds of gears, which are extensively used in automobile, aircrafts, ships, machine tools and so on, especially in the transmission system of various kinds of vehicles. There are nearly 40 gears in a car, and half of which can be produced by precision die forging process. At present, the large industrialization production of bevel gears has been achieved by precision die forging process, as well as automobile starter gears and synchronizer blocking rings. Hence, a remarkable benefit in social, economic aspects were made on saving energy. And environmental protection, the quantity and performance of the products were improved. But reports are few, about the studies on joint gears, reverse gears and spur gears with big modulus which have complicated structure and great difficulty of being formed. German ThyssenKrupp Automotive Company and Japan Nichidai Company developed precision forging forming processes on joint gears and reverse gears. And those processes have been applied to production. Duo to technical security, there is no pubulic papers. The process of forming spur gears with big modulus has not been reported yet. Domestic research and application on joint gears and spur gears with big modulus have just started internally. In this paper, it is targeted as realizing the precision die forging of those gears. Classical plastic forming theory, finite element simulation and corresponding experiments were used to study the forming mechanism and application of hollow divided flow forging technology. The main research contents and results of this paper are as follows:Hollow divided flow forging technology was studied and some research results were achieved. When the flat spur gear is obtained from the solid cylinder blank through conventional closed die forging technology, most of the metal of the blank flows along the axial and the radial flow is very little. The equivalent strain is low; however the equivalent stress is high during the forming process. As a result, the forming force increases rapidly and the teeth of the gear are not formed competely. Nevertheless, by adopting hollow divided flow forging technology in the forming process of the flat spur gear, the matal flows along the axial combined with the radial. The equivalent strain increases and the equivalent stress decreases. Meanwhile, the teeth of the gear are formed well.The main factors that influence the forming force and the interrelation of these factors were analyzed. An optimal model of target function was developed for obtaining the minimal forming force. The calculation formula for the forming force of the hollow divided flow forging technology was derived, as well as the calculation formula for the radius of the ring blank used in hollow divided flow forging technology. The optimization design was implemented.Conventional closed die forging technology of joint gear was analysed by means of traditional plasticity theory and thermodynamic couple numerical simulation in rigid-viscoplastic finite element method, through which the forming rules were obtained. Because the metal of the blank flows too long and the tangential stress of die is too high, the fracture of die and forging defects appear. According to the key technical problems, the hollow divided flow forging technology of joint gear was developed, the same as the optimum design of the shape of pre-forging. The structure of the three-stage die was designed. As well, corresponding experiments were carried out. The results show that the forging is qualified, and the hollow divided flow forging technology of joint gear is feasible.Problems such as low material utilization and large forming force exist in the forming process of the spur gear with big modulus, when using the thick wall seamless tube through extrusion with core shaft. To solve the above-mentioned problems, hot closed extrusion shceme and cold extrusion finishing hollow divided flow forging technology were proposed. The die structure design was completed. Based on coupled thermo-mechanical simulation in rigid-viscoplastic finite element method and elastoplastic finite element method, the forming processes were simulated by the software Deform-3D. Then, corresponding experiments were conducted and the results perfectly matched the simulation results.Based on the theoretical research results, a hollow divided flow forging technology production line was put into production in cooperative enterprise. The production line includes blanking, heating,16000KN three-stage hot die forging press, heat treatment furnace and 6300KN precision forging hydraulic press. Batch process of two crosspiece joint gear precision forging was done and larger economic benefit was achieved. The hollow divided flow forging technology and the die of spur gears with big modulus provide a scientific basis for forming the precision forging of the driving axle planetary gear in relevant enterprises.更多还原