铸态高铝锌基合金（ZA27）电梯曳引机蜗轮材料安全可靠性研究

【作者】 张杰；

【导师】 黎晓华；

【作者基本信息】 深圳大学 ， 材料工程， 2016， 硕士

【摘要】 近年来,随着材料工艺技术发展,国内电梯行业开始采用具有生产工艺简单、性能优良、低成本等优点的铸态高铝锌基合金ZA27制作曳引机蜗轮。然而目前,国内外专家学者对铸态高铝锌基合金ZA27的研究集中在改善材料综合机械性能,对其作为电梯曳引机蜗轮材料方面的系统研究依然空白,尚未对其作为电梯曳引机蜗轮材料进行安全可靠性评估,也未制定出相关技术指标。随着电梯增多,由铸态高铝锌基合金ZA27曳引机蜗轮失效引起的安全事故也随之增多,人们对铸态高铝锌基合金ZA27能否用于电梯曳引机蜗轮提出质疑。因此,对铸态高铝锌基合金ZA27电梯曳引机蜗轮材料安全可靠性研究具有重要意义。对出现断齿现象的电梯曳引机蜗轮进行失效分析。结果表明,蜗轮材料的主成分含量符合GB/T1175-1997《铸造锌合金》中的牌号成分含量。轮齿断裂是疲劳断裂,断裂源在齿根部位。首损齿齿根处存在疏松、气孔、夹杂等铸造缺陷,局部疏松相连形成缺陷聚集区。这些缺陷的存在引起局部应力集中,降低材料抗拉强度,裂纹在缺陷处萌生并向四周扩展。在交变载荷作用下,裂纹不断扩展,最后轮齿发生折断;断齿表面有剥落点蚀坑存在,经验证,轮齿齿面点蚀出现几率与其组织中铸造缺陷分布与大小有关。对不同铸造工艺制造的高铝锌基合金ZA27电梯曳引机蜗轮毛坯组织性能进行表征,并与铸造锡青铜的性能对比,全面分析影响铸态高铝锌基合金ZA27电梯曳引机蜗轮正常使用因素。结果表明,最佳铸造工艺为挤压铸造,该工艺下的蜗轮显微组织致密,晶粒形貌为细小等轴晶;关键部位无缩孔、疏松和夹杂物等铸造缺陷存在;抗拉强度为412MPa,断后伸长率为6.5%,冲击功为53.5J,显微硬度为127.9HV,摩擦系数为0.101~0.118。并且其力学性能优于铸造锡青铜。利用有限元分析,建立铸态高铝锌基合金ZA27电梯曳引机蜗轮力学数学模型,计算在极限工况下蜗轮所受应力,分析有限元计算结果。结果表明,最大应力发生在齿根区域;当轿厢负载125%额定载荷且静止或轿厢负载110%额定载荷以加速度9.8m/s2在底层启动或轿厢负载125%额定载荷以加速度9.8m/s2在底层紧急制动等三种极限工况下,曳引机均不会发生失效。因此控制好蜗轮关键部位铸造缺陷程度及蜗轮工作温度情况下,铸态高铝锌基合金ZA27则能够安全用于电梯曳引机蜗轮的制造。更多还原

【Abstract】 In recent years,with the development of materials technology,the domestic elevator industry began to use the cast state high aluminum zinc base ZA27 which has simple production process,excellent performance,low cost and other advantages to make worm gear in elevator traction machine. However at present,experts and scholars for the cast state high aluminum zinc based alloy ZA27 research focuse on improving the comprehensive mechanical properties of material,the system studied aspects on material of worm gear in elevator traction machine is still blank,As material worm gear in elevator traction machine which lacked safety and reliability assessment, also did not formulate relevant technical indicators. With the increase of the elevator,the cast state high aluminum zinc based alloy ZA27 worm gear in elevator traction machine failure caused by accidents have also increased,the cast state high aluminum zinc based alloy ZA27 can be used to challenge the worm gear in elevator traction machine. Therefore,it is of great significance to the research on the safety and reliability of the cast state high aluminum zinc based alloy ZA27 material of worm gear in elevator traction machine.The failure analysis of the elevator traction machine which appeared worm gear teeth broken. The results show that the content of the principal components of the worm gear was in accordance with the content of the grade composition in the GB/T1175-1997 《casting zinc alloy》. Tooth fracture is fatigue fracture,fracture source at the root part of the gear. There is pitting corrosion pit on the surface of broken tooth. There are some casting defects such as loose and porosity and inclusions on the first tooth loss,partial loose to form defect area.These defects cause local stress concentration,reduce tensile strength of the material,crack initiation and propagation in the defect. Under cyclic loading,he crack extending,finally broken tooth. It is proved that the probability of pitting on the surface of gear teeth is related to the distribution and size of the casting defects in the microstructure.To characterize microstructure and properties of high aluminum zinc based alloy ZA27 worm gear blank in elevator traction machine from different manufacturing processes,andwith the comparison of the properties of cast tin bronze,then to comprehensive analysis the influence factors of normal use of casting state high aluminum zinc based alloy ZA27 worm gear in elevator traction machine. The results show that the best production process is squeeze casting,the microstructure of the worm gear is dense,grain morphology is fine equiaxed grain;there is not loose and porosity and inclusions in key parts;its tensile strength is 412 MPa and elongation is 6.5%, impact energy is 53.5J,micro hardness for is 27.9HV.The friction coefficient is 0.101~0.118. And its mechanical properties are better than cast tin bronze.Using finite element analysis to establish the cast state high aluminum zinc based alloy ZA27 worm gear in elevator traction machine dynamics mathematical model and calculate worm gear stress in different conditions and analysis the calculation results of finite element.The results show that the maximum stress occurs in the root area;When the car load 125% of rated load and static or car load 110% of rated load to 9.8m/s2 acceleration at the bottom to start or car load 125% of rated load to 9.8m/s2 acceleration in underlying emergency braking of three extreme conditions,the traction machine failure which does not occur. Therefore,to control casting defect degree in the key parts of the worm gear,and the working temperature,the cast state high aluminum zinc based alloy ZA27 can used safety for manufacturing worm gear in elevator traction machine.更多还原