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1、华中科技大学硕士学位论文高性能铝硅轴承合金材料及闭模轧制生产技术的研究姓名：雷健申请学位级别：硕士专业：材料加工工程指导教师：魏伯康;袁序弟20041001I摘 要 轴瓦是汽车发动机重要的减磨零件它与曲轴轴径构成发动机四大摩擦副之一其主要功能是减少轴瓦与曲轴间的滑动摩擦磨损提高发动机曲轴及连杆的使用寿命轴瓦在使用过程中由于受到来自曲轴旋转产生的交变载荷冲击润滑油中外来硬质点引起轴瓦的擦伤以及轴瓦与曲轴轴颈加工的不同轴而产生局部磨损因此作为轴承合金必须具备良好的疲劳性能和表面性能 早期的滑动轴承材料以巴氏合金为主轴瓦采用铸造工艺生产近年来随着发动机转速的提高和输出功率的增加汽车工业广泛采用铝基铜
2、基轴承合金材料和复合轧制粉末冶金烧结工艺来生产发动机轴瓦在铝基轴承合金中最具代表性的为A l 2 0 S n C u 这种合金中含有 2 0 % 的锡锡相在铝基体中呈孤岛状分布形成硬基体软质点的耐磨组织随着球铁曲轴的广泛应用和汽车发动机柴油化的发展趋势A l 2 0 S n C u合金耐磨性能差和疲劳强度低的不足日益暴露出来铜基轴承合金中最具代表性的为铜铅合金这种合金的轴瓦具有较高的疲劳性能比较适合大功率柴油发动机其不足在于材料成本高制造工艺复杂和不利于环保基于以上情况项目组开展高性能低成本的铝硅轴承合金材料及制造工艺的研究进一步拓展了传统铝基轴承材料的使用空间达到取代或部分取代 A l 2
3、0 S n C u 和铜铅轴承合金的目的 本项目分析了轴瓦的工作状况及材料和制造工艺的发展进程探讨了影响轴瓦寿命的主要因素通过材料熔铸热处理和复合轧制过程中工艺的优化基本上解决了研制合金所暴露出轧制性能和材料的表面性能差的问题 成功开发出两个品种的高性能铝硅轴承合金材料及轴瓦性能达到国外同类产品指标要求 在低硅轴瓦材料试验中一方面在传统的 A l 2 0 S n C u材料基础上进行合金优化设计通过添加 2 . 5 % 硅和减少低熔点锡的含量来提高合金的强度和硬度从而达到提高轴瓦的疲劳强度和耐磨性能的目的另一方面由于硬质点硅的加入也伴随着合金轧制性能降低因此项目组进行了轴瓦带材制造工艺及退火工
4、艺的优化试验使得轧制成材率由原先不足 1 0 % 提高到 9 0 % 以上另外项目组开展了中高硅铝基轴瓦II材料的研究将合金中的硅含量提高到 4 8 % 锡含量进一步降低到 3 6 % 水平并加入一定量锌和其他强化元素使得研制合金的疲劳性能达到或接近铜铅合金的水平这样材料的轧制性能差的问题表现的更加突出因此解决这一问题也成了项目研究的重点与难点通过采取闭模轧制工艺代替传统的开放式平辊轧制工艺基本上解决合金轧制性能差的问题满足汽车发动机对轴瓦使用性能的要求并实现了轴瓦批量工业化生产 通过本项目的研究项目组基本掌握了高性能铝硅轴承合金的全套生产技术为轴瓦产品的升级换代奠定了良好的基础使得轴瓦生产技
5、术达到国际先进水平取得了良好的社会经济效益 关键词发动机 滑动轴承 铝硅合金 复合 闭模轧制 疲劳性能 表面性能 耐磨性能 IIIABSTRACT Bearing, which forms one of the four friction pairs with shaft journal, is a significant engine component. Its primary functions are to reduce wear and tear between bearing and shaft, and raise longevity of shaft and connectio
6、n rod. During the use of bearing, due to the effect of three factors: cyclic impact from rotating shaft, hard exterior particles in the lubricating oil, which could lead to score of bearing or journal, as well as minor uncoaxiality with the bearing or shape irregularities of crankshaft journal, whic
7、h can result in wear partly, the material must possess excellent fatigue strength and good compliance. Bearings of Babbitt Alloy, of which manufacturing technology is usually chosen centrifugal casting, have been widely used in the initial engine. Recently, with faster rotating speed of engine and g
8、reater output of power, bearing materials of engine have trended to choose Al-based or Cu-based alloy, and relevant manufacturing processing of bearing adopts roll-bonding and powder metallurgy sintering respectively. Among Al-based bearing materials, a representative alloy contains 20% Sn that dist
9、ributes in matrix as “isolated island” , which is a typical wear-resisting structure with soft particle embedding hard matrix. This alloy has largely used in bearings of light engine. However, under the condition of widely applying of nodular iron shaft and the general trend of diesel engine in the
10、automobile industry, its disadvantages of poor wear-resisting property and low fatigue strength are exposed clearly. On the other hand, Cu-Pb bearing alloys with higher fatigue property, which adapt to manufacture the bearing of great power diesel engine, but reveals high cost, complicated manufactu
11、ring processing, as well as unfriendly environmental behavior, so its application has been limited gradually. Based the situation above, we expect to develop two new type of bearing Al-Si alloys with high properties to extend the using space of conventional Al-based material. In this article, the gr
12、oup of project has analyzed the operating state of bearing and its evolving process, and discussed the principal factors that influence bearings lifespan. By optimizing of melting, casting, heat treating and roll-bonding, the problems of poor rolling-forming property and bad surface performance, whi
13、ch have exposed in using and IV producing of bearing, have been tackled basically. Two or three kinds of Al-based bearing alloys with high properties, which adapt to high volume productions of automobile industry, have been developed successfully. These alloy and bearings properties have caught up w
14、ith the counterpart abroad. During optimizing experiment of composition of low silicon bearing material in terms of traditional alloy Al20SnCu, through addition of 2.5% Si that acts as role of solid solution strengthening and decrease of low melting point Sn, the bearing alloy with high wear resista
15、nce and good fatigue strength has been obtained. Meanwhile, the companying problem of poor rolling-forming property is also brought out. In order to deal with it, the project group adjusts the processing of rolling and annealing of bearing strip, the production rate raises more than 90% from less th
16、an 10%. On the other hand, the group starts the research about Al-Si bearing alloy. By increasing the content of Si to 48%, decreasing Sn to 36%, as well as adding Zn and other alloying element, the fatigue strength of the developing alloy reaches or approaches the level of Cu-Pb alloy. With improvement of strength, the decline of rolling property is certain consequence, so tackling this problem becomes the importance and difficulty of project exploring. Through replacing the tr
