渗碳齿轮钢淬透性及其热处理变形和疲劳性能研究

发布时间：2018-03-18 14:22

本文选题：齿轮钢　切入点：淬透性　出处：《钢铁研究总院》2017年博士论文　论文类型：学位论文

【摘要】：淬透性在齿轮钢的生产和应用中具有重要的作用,窄淬透性带宽是高品质齿轮钢的重要特点之一。目前,国内齿轮钢淬透性带宽只能稳定控制在8 HRC以内,与4 HRC国外先进水平有明显差距。因此,开展齿轮钢淬透性及其对组织和性能影响的研究,具有重要的工程价值。本论文选择四种具有不同淬透性的渗碳齿轮钢作为研究对象,对比研究了四种齿轮钢的端淬曲线变化规律及影响因素,优化了硬度分布函数淬透性预测模型,并通过500 ℃临界冷速完善了组织预测模型,同时研究了淬透性对渗碳热处理变形的影响规律,探讨了渗碳齿轮钢的旋转弯曲疲劳和接触疲劳性能的影响因素。基于多炉次端淬试验结果,在评价20CrMoH和20CrNiMoH齿轮钢的淬透性预测模型适用性的基础上,对淬透性预测模型进行了修正,修正后的硬度分布函数模型在J5、J9和J15点硬度预测标准误差均小于2 HRC。研究发现,当晶粒度超过7级后,晶粒度对淬透性的影响明显,若将J9处淬透性带宽控制在≤4 HRC,晶粒度级别波动应≤1级。利用ABAQUS有限元软件建立了齿轮钢末端淬火试样温度场模型,结合Maynier组织预测模型对端淬试样J5、J9和J15处的组织和硬度进行预测,利用500 ℃的瞬时冷速预测组织和硬度值与试验值吻合较好。利用以上模型对20CrNiMoH钢J9处组织和硬度预测结果表明,若J9处淬透性带宽控制在≤4 HRC,马氏体含量的波动不应超过16.7%。C型缺口试样试验结果表明,渗碳热处理变形随着齿轮钢淬透性的提高而增加,热处理变形量大小主要与心部马氏体组织含量有关。当20CrNiMoH钢J9处硬度低于32 HRC时,心部组织以贝氏体为主,热处理变形量随淬透性的提高缓慢增加;当J9处硬度超过32 HRC时,心部组织以马氏体为主,马氏体含量和热处理变形量随淬透性的提高显著增加。不同齿轮钢的热处理变形率也与J9处硬度值呈正相关。齿轮钢旋转弯曲疲劳强度主要与渗碳层硬度、夹杂物的大小及分布、以及晶粒尺寸有关,渗碳齿轮钢裂纹起裂主要源于渗碳层内夹杂物。20CrNiMoH钢接触疲劳试样剥落坑深度在赫兹理论最大切应力附近,并且与夹杂物的分布有关。提高洁净度、细化渗碳层晶粒尺寸,能改善齿轮钢的疲劳性能。
[Abstract]:Hardenability plays an important role in the production and application of gear steel, narrow hardenability band is one of the important characteristics of high quality gear steel. At present, the bandwidth is only stable within 8 HRC through domestic gear steel quenching, there is difference between the 4 and HRC foreign advanced level. Therefore, the research development of gear steel hardenability and its effects on Microstructure and mechanical properties, which has important engineering value. This paper selects four different hardenability of carburized gear steel as the research object, a comparative study of the factor of the Jominy curve and the influence of the four kinds of gear steel, optimize the hardness distribution function of hardenability prediction model, and by 500 degrees the critical cooling rate improve the organization prediction model, also studied the influence of hardenability of carburizing heat treatment deformation, discusses the influence factors of carburized gear steel rotary bending fatigue and contact fatigue performance. Based on multi The furnace end quenching test results in the evaluation of 20CrMoH and 20CrNiMoH gear steel hardenability prediction based on the applicability of the model, the hardenability prediction model is modified, the modified hardness distribution function model in J5, J9 and J15 hardness standard error of prediction was less than 2 HRC. study found that when the grain size more than 7, the effects of grain size on the hardenability of the obvious, if the J9 hardenability bandwidth control in less than 4 HRC, the grain size level fluctuation should be less than or equal to 1. Established the model of temperature field of steel end quenching gears using ABAQUS finite element software, combined with the Maynier organization prediction model of Jominy J5 the organization, and the hardness of J9 and J15 at 500 DEG C predicted using instantaneous cooling rate prediction of microstructure and hardness values agree well with the experimental results. Using the above model and the hardness of 20CrNiMoH steel J9 Organization predicted results show that if J9 hardenability bandwidth control in H 4 RC, the content of martensite fluctuations should not exceed 16.7%.C notched specimens test results show that the heat treatment distortion increases with the hardenability of gear steel for improved heat treatment the amount of deformation is mainly related with the heart of martensite content. When the 20CrNiMoH steel J9 hardness is lower than 32 HRC, the heart tissue to bainite, heat treatment deformation with hardenability improved slowly increased; when the J9 hardness is more than 32 HRC, the heart tissue to martensite and martensite content and heat treatment to improve the deformation with hardenability increased significantly. Different heat treatment of gear steel deformation rate is positively correlated with J9 the hardness value. The rotary bending fatigue strength of gear steel with carburizing hardness, size and distribution of inclusions, and the grain size of carburized gear steel crack mainly due to inclusions in.20CrNiMoH Steel Carburized Layer contact fatigue spalling pits The depth is in the vicinity of the maximum shear stress in Hertz theory, and is related to the distribution of inclusions. Improving the cleanliness and refining grain size of carburized layer can improve the fatigue performance of gear steel.

【学位授予单位】：钢铁研究总院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG142.1;TG161

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