【作者】 黄宇；

【导师】 黄光胜；

【作者基本信息】 重庆大学 ， 工程（材料工程）（专业学位）， 2021， 硕士

【摘要】 工业机器人作为智能制造“云-网-端”架构的重要实现端,近年来获得了迅猛发展。轴承作为工业机器人关节用减速器的重要承载运动部件,其耐磨性的高低极大影响了减速器的使用寿命。目前,国内机器人用RV减速器曲柄轴的滚动疲劳寿命普遍较短,严重制约了国内机器人行业的发展。本论文以常见的热轧态商用曲柄轴用钢20CrNi2Mo为研究对象,旨在对比国内外的曲柄轴用钢的组织与性能,研究渗碳淬火工艺及深冷处理对20CrNi2Mo钢组织力学性能的影响规律。结论如下:(1)国内外的曲柄轴用钢均为低碳钢,但其在Ni、Cr含量配比方面上有一定差异。此外,国外轴承用钢组织中夹杂物较为细小,且分布均匀,夹杂物控制上整体优于国内。国内外曲柄轴心部组织相似,均为低碳板条状马氏体,但表层组织差异较大。其中,国内的为高碳针状马氏体及少量残余奥氏体,而国外的则以细小的隐晶马氏体组织为主,其间均匀分布有细小的碳化物,国外曲柄轴渗碳层的硬度值比国内高约100HV。(2)对比研究了传统渗碳淬火和循环渗碳淬火以及气淬+油淬工艺下20CrNi2Mo钢组织与力学性能之间的关系。其中,传统渗碳淬火和循环渗碳淬火后,20CrNi2Mo钢表层组织均以高碳针状马氏体为主,并残留有部分奥氏体及少量碳化物,而经气淬+油淬处理后其组织细化显著,以隐晶马氏体为主。此外,气淬+油淬后的表面渗碳层硬度梯度、心部硬度及拉伸性能及耐磨性整体均优于另外两者。(3)经过深冷处理后,三种渗碳淬火工艺的试样表层主要组织类型未出现显著变化,但奥氏体含量相较于处理前降低显著,分别降低了2.3%、5.1%、3.9%。经过深冷处理后三种试样的整体表层硬度相较于未深冷处理前均提高了约50HV,组织中较低的奥氏体含量导致摩擦过程中形变诱发的奥氏体相变比例降低,从而使得试样在整个摩擦过程的摩擦系数相较于深冷处理前更加稳定。此外,在100N载荷下,深冷处理后的三个试样磨损表面均没有出现明显的犁沟。在200N载荷下,试样表面较为平整,并覆盖有大量的氧化膜,氧化膜的存在或促进了试样耐磨性的提高。更多还原

【Abstract】 As an important realization end of the intelligent manufacturing "cloud-networkend" architecture,industrial robots have been developing rapidly in recent years.Bearings are important moving parts of the reducer for industrial robot joints,and their wear resistance greatly affects the service life of the reducer.At present,the rolling fatigue life of the crank shaft of the domestic robot RV reducer is generally short,which severely restricts the development of the domestic robot industry.This paper takes the common hot-rolled commercial crankshaft steel 20 Cr Ni2Mo as the research object,aiming to compare the structure and properties of crankshaft steels at home and abroad,and discuss the effect of carburizing and quenching process and cryogenic treatment on the mechanical properties of 20 Cr Ni2Mo steel.Conclusions are as below:(1)The crankshaft steels at home and abroad are all low-carbon steels,but there are certain differences in the ratio of Ni and Cr content.In addition,the inclusions in the steel structure of foreign bearings are relatively small and evenly distributed,and the control of inclusions is generally better than that of domestic ones.The structure of the crank shaft at home and abroad is similar,all of which are low-carbon lath martensite,but the surface structure is quite different.Among them,the domestic one is high-carbon acicular martensite and a small amount of retained austenite,while the foreign one is mainly composed of fine cryptocrystalline martensite with evenly distributed fine carbides.The hardness value of the carburized layer of crankshaft abroad is about 100 HV higher than that of domestic.(2)The relationship between the structure and mechanical properties of 20 Cr Ni2Mo steel under the traditional carburizing quenching and cyclic carburizing quenching and gas quenching + oil quenching process was comparatively studied.Among them,after traditional carburizing and quenching and cyclic carburizing and quenching,the surface structure of 20 Cr Ni2Mo steel is mainly high-carbon acicular martensite,with some austenite and a small amount of carbide remaining,and after gas quenching + oil quenching treatment Its structure is remarkably refined,mainly cryptocrystalline martensite.In addition,the overall hardness gradient,core hardness,tensile properties and wear resistance of the surface carburized layer after gas quenching and oil quenching are better than the other two.(3)After cryogenic treatment,the main microstructure types of the sample surface of the three carburizing and quenching processes did not change significantly,but the austenite content was significantly reduced compared with that before the treatment,which was reduced by 2.3%,5.1%,and 3.9%,respectively.After cryogenic treatment,the overall surface hardness of the three samples is increased by about 50 HV compared with that before cryogenic treatment.After cryogenic treatment,the lower austenite content in the structure leads to a decrease in the proportion of austenite transformation induced by deformation during the friction process,so that the friction coefficient of the sample during the entire friction process is more stable than before treatment.In addition,under a load of 100 N,no obvious furrows appeared on the worn surfaces of the three specimens after cryogenic treatment.Under a load of 200 N,the surface of the sample is relatively flat and covered with a large amount of oxide film.The presence of oxide film may promote the improvement of the wear resistance of the sample.更多还原