發(fā)布時間：2019-01-19 08:50

【摘要】：弧齒錐齒輪齒面幾何形狀與嚙合理論非常復雜。在生產(chǎn)中,一方面對其齒面質(zhì)量要求很高,另一方面需要在擁有優(yōu)良耐磨性的同時具備較高抗接觸疲勞和抗彎曲疲勞性能。現(xiàn)今汽車工業(yè)通常采用滲碳淬火表面強化技術提高零件機械性能,工件淬火后可以獲得外硬內(nèi)韌的組織分布。但是淬火過程冷卻介質(zhì)流動不均、組織轉(zhuǎn)變、熱應力作用將使零件不可避免地產(chǎn)生扭曲和變形,降低幾何精度。過去弧齒錐齒輪相關熱處理研究集中于熱應變及組織應變對工件幾何精度的影響,忽略淬火過程冷卻介質(zhì)流動對熱邊界條件變化的影響。這種簡化方式適于淬火槽內(nèi)流場分布均勻、工件幾何形狀簡單的情況,但對于預測結構復雜零件的冷卻歷史有一定局限性。相關研究結果顯示,淬火冷卻階段換熱系數(shù)的取值對仿真計算結果影響很大。為減小弧齒錐齒輪熱處理畸變,了解熱處理過程組織演變、應力應變分布規(guī)律,對考慮冷卻介質(zhì)流動影響的弧齒錐齒輪滲碳淬火熱處理進行了如下研究:(1)使用三維軟件UG建立弧齒錐齒輪及現(xiàn)有淬火槽模型,使用流體動力學軟件CFX對現(xiàn)有淬火槽內(nèi)冷卻介質(zhì)流場分布進行了研究,得到槽內(nèi)流場分布及相關因素影響規(guī)律。(2)在上述研究基礎上提出均化流場分布的方案,得到單向、均勻、可控的淬火槽流場分布;將考慮介質(zhì)流動的換熱系數(shù)作為淬火槽內(nèi)冷卻背景下多場耦合計算動態(tài)熱邊界條件,使考慮介質(zhì)流動的多場耦合滲碳淬火仿真計算成為可能,并提高了仿真預測準確度。(3)使用材料預報軟件Jmatpro預測了20CrMoH低碳合金鋼的材料性能,使用熱處理仿真軟件Deform-HT對考慮冷卻介質(zhì)流動的滲碳淬火熱處理進行了仿真研究,分析了弧齒錐齒輪在滲碳淬火熱處理中溫度變化、組織演變規(guī)律,得到了碳元素分布、微觀組織分布、硬度分布、殘余應力及熱畸變等信息,為熱處理工藝參數(shù)的調(diào)整提供參考。仿真計算結果顯示,淬火后齒頂產(chǎn)生鼓形凸起,可能使齒輪副出現(xiàn)頂緣接觸。(4)為了在保證齒面硬度的同時縮短鼓形長度,使用正交試驗對考慮介質(zhì)流動影響的滲碳淬火熱處理工藝進行了優(yōu)化,以介質(zhì)溫度、入口速度、保溫溫度及擴散碳勢為試驗因素,鼓形長度及齒面硬度為試驗指標,對熱處理工藝參數(shù)進行優(yōu)化,得到了最優(yōu)工藝參數(shù)組合,從流場分布和熱處理工藝優(yōu)化兩個方面提高現(xiàn)有熱處理水平。本文從流場分布和熱處理工藝參數(shù)兩個方面對淬火槽冷卻背景下的滲碳淬火熱處理進行了優(yōu)化設計,效果良好,能夠為實際生產(chǎn)提供參考。
[Abstract]:The tooth surface geometry and meshing theory of arc bevel gear are very complicated. In production, on the one hand, the quality of tooth surface is very high, on the other hand, it is necessary to have high contact fatigue and bending fatigue properties while having excellent wear resistance. Nowadays, Carburizing and quenching surface strengthening technology is usually used to improve mechanical properties of parts in automobile industry. After quenching, the hard and tough microstructure distribution of workpiece can be obtained. However, the uneven flow of cooling medium, the transformation of microstructure and thermal stress during quenching will inevitably cause distortion and deformation of the parts and reduce the geometric accuracy. In the past, the related heat treatment of arc bevel gears focused on the effect of thermal strain and microstructure strain on the geometric accuracy of workpiece, and the influence of cooling medium flow on the change of thermal boundary conditions during quenching was ignored. This simplified method is suitable for the cases where the flow field in the quenching tank is uniform and the geometric shape of the workpiece is simple, but it is limited to predict the cooling history of the complicated parts. The results show that the heat transfer coefficient of quenching cooling stage has a great influence on the simulation results. In order to reduce the distortion of arc bevel gear during heat treatment, to understand the microstructure evolution and the distribution of stress and strain during heat treatment, The Carburizing quenching heat treatment of spiral bevel gear considering the influence of cooling medium was studied as follows: (1) the model of arc bevel gear and existing quenching slot was established by using 3D software UG. The flow field distribution of cooling medium in the existing quenching tank was studied by using the fluid dynamics software CFX. The distribution of the flow field in the tank and the influence of related factors were obtained. (2) based on the above research, the scheme of homogenizing the flow field distribution was put forward, and the unidirectional flow field distribution was obtained. Uniform and controllable flow field distribution in quenching tank; Taking the heat transfer coefficient of medium flow into account as the dynamic thermal boundary condition of multi-field coupling calculation under the background of cooling in the quenching tank, it is possible to simulate the multi-field coupled Carburizing quenching with the consideration of the medium flow. (3) material prediction software Jmatpro is used to predict the material properties of 20CrMoH low carbon alloy steel, and the heat treatment simulation software Deform-HT is used to simulate the Carburizing quenching heat treatment considering the flow of cooling medium. The temperature change and microstructure evolution of arc bevel gear during Carburizing quenching heat treatment are analyzed. The information of carbon element distribution, microstructure distribution, hardness distribution, residual stress and thermal distortion are obtained. It provides reference for the adjustment of heat treatment process parameters. The simulation results show that after quenching the top of the tooth produces a bulge which may make the gear pair contact with the top edge. (4) in order to ensure the hardness of the tooth surface at the same time to shorten the length of the drum shape. The orthogonal test was used to optimize the Carburizing and quenching heat treatment process considering the influence of medium flow. The factors such as medium temperature, inlet velocity, holding temperature and diffusion carbon potential were taken as the test factors, and the drum length and tooth surface hardness were taken as the test indexes. The optimal combination of process parameters was obtained by optimizing the process parameters of heat treatment, and the existing heat treatment level was improved from two aspects: flow field distribution and heat treatment process optimization. In this paper, the optimum design of Carburizing and quenching heat treatment under the cooling background of quenching tank is carried out from two aspects of flow field distribution and heat treatment process parameters. The results are good and can provide reference for practical production.
【學位授予單位】：江西理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG162.73

【參考文獻】

相關期刊論文 前10條

1 王延忠;陳云龍;張祖智;陳燕燕;劉e，

本文編號：2411200