烧结组合式粉末冶金中空凸轮轴生坯装配工艺的研究

发布时间：2018-03-02 00:23

  本文关键词： 粉末冶金中空凸轮轴 粘结处理 生坯装配 滚花参数　出处：《北京有色金属研究总院》2017年硕士论文　论文类型：学位论文

【摘要】：烧结组合式粉末冶金中空凸轮轴是一种轻量化、高性能的新型凸轮轴。在大力提倡节能环保的趋势下,烧结组合式粉末冶金中空凸轮轴具有质量轻、耐磨性好、设计灵活等优点,发展前景十分广阔。粉末冶金材料生坯强度低,脆性大,因此凸轮片容易在运输、装配过程发生破损甚至破裂。目前烧结组合式粉末冶金中空凸轮轴在装配时需要对凸轮进行预烧处理,增加了工序和设备投入,同时使得能耗增加、尺寸精度变差,导致生产成本提高,因此实现凸轮的生坯装配是一个亟待解决的难题。本文通过粘结处理工艺向粉末中添加具有高本征力学性能的粘结剂,以提高凸轮轴粉末的工艺性能和生坯力学性能,实现凸轮轴生坯的自动装配工艺。本文对多种粘结剂树脂进行了对比和改性研究,确定了粘结剂种类和用量并对比了粘结剂处理后粉末性能。通过对粉末压制工艺和压坯性能的研究,优化了生坯固化工艺,获得了更高强度和韧性的凸轮生坯。在对装配过程中的滚花参数进行适当优化后实现了粉末冶金中空凸轮轴的生坯自动装配,并进行烧结实验。得到以下结论:1)研究了粘结剂种类对生坯力学性能的影响,并通过共混反应将25 wt.%的热塑性树脂TP与75 wt.%的热固性树脂W6混合,获得了综合力学性能优异的WT25粘结剂,加入1.0wt.%此改性粘结剂的粉末生坯强度达到了 36.1MPa,拉伸强度达到了 8.7MPa,拉断变形率为2.6‰,与W6相比,提高了近10倍。2)研究了粘结剂含量(0～3.0 wt.%)对粉末性能的影响。当粘结剂的含量为1.0 wt.%时,具有最佳的综合工艺性能,流动性为30s/50g,松装密度为2.7g/cm3,细粉粘结率由25%提高到了 96%,表征成分偏析性的石墨变异系数由8.6%降低至1.2%。3)研究了固化工艺对生坯力学性能的影响。随着固化温度提高和固化时间的延长,生坯综合力学性能提高,超过210℃后将导致粘结剂失效。最佳固化工艺为150℃保温150min,此时生坯强度达到39.3MPa,拉伸强度达到9.6MPa,拉断变形率为2.8‰。4)利用正交试验研究了凸轮装配过程中的滚花齿高,齿长和齿间距对凸轮表面应变的影响。当齿高为0.04mm,齿长为8mm,齿间距为0.6mm时,凸轮装配时应变最小,为120μm/mm。在此条件下装配,凸轮不易开裂,产品更加稳定。5)用凸轮轴自动装配机在最佳装配参数下对凸轮进行了生坯装配。装配后的凸轮轴的凸轮角度和轴向位置合格率为100%,而凸轮表面开裂概率仅为1.3%,实现了凸轮生坯的自动装配。6)生坯装配的凸轮轴经烧结后凸轮密度达到7.6g/cm3,凸轮硬度达到55HRC以上,凸轮与轴管间的焊接扭矩约为1000N·m。
[Abstract]:Sintered composite powder metallurgy hollow camshaft is a new type camshaft with lightweight and high performance. Under the trend of promoting energy saving and environmental protection, sintered composite powder metallurgy hollow camshaft has light weight and good wear resistance. Due to the advantages of flexible design and wide prospect of development, the powder metallurgy material has low strength and high brittleness, so the cam sheet is easy to be transported. The assembly process is damaged or even broken. At present, it is necessary to pre-fire the cam in the assembly of the sintered composite powder metallurgy hollow camshaft, which increases the process and equipment input, increases the energy consumption, and makes the dimension precision worse. Therefore, it is an urgent problem to realize the assembly of cam billet. In this paper, binder with high mechanical properties is added to the powder by bonding process. In order to improve the technological properties and mechanical properties of camshaft powder and realize the automatic assembly process of camshaft billet, this paper compares and modifies many kinds of binder resins. The type and amount of binder were determined and the properties of powder treated with binder were compared. The solidification process of raw billet was optimized through the study of powder pressing technology and compaction properties. Cam billet with higher strength and toughness is obtained. The blank of powder metallurgy hollow camshaft is automatically assembled after proper optimization of knurling parameters in assembly process. The effect of binder on the mechanical properties of green billet was studied, and the 25 wt.% TP and 75 wt.% thermosetting resin W6 were mixed by blending reaction. The WT25 binder with excellent mechanical properties was obtained. The strength of the powder billet was 36.1 MPA, the tensile strength was 8.7 MPA, and the tensile deformation rate was 2.6 鈥，

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