螺杆压缩机阴转子轧制成形研究

发布时间：2019-05-12 08:58

【摘要】：螺杆转子是螺杆压缩机的核心零件,其截面齿形由多段曲线组成,齿形复杂非对称,其螺旋齿形具有螺距大,螺旋升角大和齿形高度大的特点。螺杆转子的传统加工方式为切削加工,但切削时60%以上材料被去除,材料利用率低,同时加工耗时长,生产效率低。为进一步改善螺杆转子的工艺水平,提出定轴横轧螺杆转子的塑性成形新工艺,将螺杆转子的非对称大螺旋齿形和阶梯台阶在一个轧制过程中直接成形,提高其生产效率和材料利用率。选用易切削钢SAE1141做为轧制材料,其切削性能好,利于后续机加工的进行。课题采用理论分析、有限元模拟和轧制实验相结合的方法,对螺杆阴转子的定轴横轧成形工艺展开研究。通过高温压缩实验,对易切削钢SAE1141在不同变形条件下的热流变行为进行了实验测定。考虑应变量的影响,建立了易切削钢SAE1141的应变修正的Arrhenius本构方程,实现了对其流变应力行为的良好预测。基于空间啮合原理和矩阵理论,建立了与模具和轧件实时变化的共轭运动关系相关联的模具辊型曲线的通用求解方程,实现了模具辊型曲线的变参数化设计。构建得到的符合轧制工艺要求的轧件型线不同于产品原始型线,与原始产品形状大体保持一致,相应精整阶段的模具辊型曲线根据轧制啮合关系进行求取。对大螺旋齿形的轧制成形过程进行研究,提出了等型角增长和变型角增长的两种螺旋齿形成形方案,相应提出浮动结点法和固定结点法两种模具辊型曲线设计方案。基于不同模具辊型曲线设计方案和坯料参数确定方法,通过有限元仿真模拟分析表明,坯料长度按照螺旋齿形部分长度选取,采用固定结点法方案进行模具辊型曲线设计,轧制过程中金属变形均匀,齿形长起能力强,适合与楔横轧工艺配合使用。根据大螺旋齿形的成形特点,提出变齿形、变齿高的螺旋辊型模具设计方法,轧制时保证了模具和轧件的良好啮合。螺旋辊型模具由多组变导程、变螺旋升角的螺旋凸棱组成,单个螺旋凸棱的高度渐进升高；沿轴向方向,模具螺旋凸棱的高度一致。通过有限元软件DEFORM对大螺旋齿形轧制成形过程进行了仿真模拟分析,揭示了轧制变形区金属的流动特点；轧制螺杆阴转子时,应采用与其工作啮合时相反的旋向进行轧制,利于金属向径向齿高方向流动。在上述研究基础上,利用UG软件编程完成了螺旋辊型模具的加工制造。通过轧制实验首次实现了螺旋升角为45°20′、齿高比例达45.5%的非对称大螺旋齿形和阶梯台阶的直接轧制成形,得到的螺杆阴转子尺寸符合要求、内部质量合格,表明相关研究工作的结论是正确的,定轴横轧螺杆阴转子的工艺是可行的。相比于传统切削工艺,定轴横轧新工艺的节材率可达39%,净轧制耗时仅5-8s,具有较好的经济效益和实用价值。
[Abstract]:Screw rotor is the core part of screw compressor. Its section tooth profile is composed of multi-segment curve, the tooth profile is complex and asymmetrical, and its spiral tooth profile has the characteristics of large pitch, large spiral lift angle and large tooth profile height. The traditional machining method of screw rotor is cutting, but more than 60% of the materials are removed, the utilization rate of materials is low, and the processing time is long and the production efficiency is low. In order to further improve the process level of screw rotor, a new plastic forming process of screw rotor with fixed axis cross rolling is put forward, and the asymmetric large spiral tooth profile and step of screw rotor are formed directly in one rolling process. Improve its production efficiency and material utilization rate. Easy cutting steel SAE1141 is selected as rolling material, and its cutting performance is good, which is beneficial to subsequent machining. In this paper, the forming process of screw negative rotor with fixed axis cross rolling is studied by means of theoretical analysis, finite element simulation and rolling experiment. The thermal Rheological behavior of easy cutting steel SAE1141 under different deformation conditions was measured by high temperature compression experiment. Considering the influence of strain variables, the strain modified Arrhenius constitutive equation of easy cutting steel SAE1141 is established, and the flow stress behavior of easy cutting steel is predicted well. Based on the principle of spatial meshing and matrix theory, the general solving equation of die roll profile curve related to the conjugated motion relation of die and rolling piece in real time is established, and the variable parameter design of die roll profile curve is realized. The rolling profile constructed in accordance with the requirements of rolling process is different from the original profile of the product and is generally consistent with the shape of the original product. The roll profile curve of the die in the corresponding finishing stage is obtained according to the rolling meshing relationship. In this paper, the rolling forming process of large spiral tooth profile is studied, and two kinds of spiral tooth forming schemes with equal angle increase and variable angle growth are put forward, and two kinds of die roll curve design schemes, floating node method and fixed node method, are put forward accordingly. Based on the design scheme of different die roll profile curve and the determination method of billet parameters, the finite element simulation analysis shows that the blank length is selected according to the partial length of spiral tooth profile, and the fixed node method is used to design the die roll profile curve. In the rolling process, the metal deformation is uniform and the tooth shape is long, so it is suitable for use in combination with cross wedges rolling process. According to the forming characteristics of large spiral tooth profile, the design method of spiral roll die with variable tooth shape and variable tooth height is put forward, which ensures the good meshing between die and rolling piece during rolling. The screw roll die is composed of many groups of helix convex edges with varying lead and angle, and the height of a single spiral convex edge is gradually increased, and along the axial direction, the height of the screw convex edge of the die is consistent. The forming process of large spiral tooth profile rolling is simulated and analyzed by finite element software DEFORM, and the flow characteristics of metal in rolling deformation zone are revealed. When rolling screw negative rotor, the opposite rotation direction should be used to roll the screw negative rotor, which is beneficial to the flow of metal in the direction of radial tooth height. On the basis of the above research, the machining and manufacturing of spiral roll die is completed by using UG software. The direct rolling forming of asymmetric large spiral tooth profile and step with spiral lift angle of 45 掳20 and tooth height ratio of 45.5% is realized for the first time through rolling experiment. the size of the screw negative rotor meets the requirements and the internal quality is qualified. The results show that the conclusion of the related research work is correct and the process of fixed axis cross rolling screw negative rotor is feasible. Compared with the traditional cutting process, the material saving rate of the new fixed axis cross rolling process can reach 39%, and the net rolling time is only 5 脳 8 s, which has better economic benefit and practical value.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG335.19

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