纯铁薄壁球壳精密车削技术基础研究

发布时间：2018-04-07 17:00

  本文选题：纯铁　切入点：薄壁球壳　出处：《南京航空航天大学》2016年博士论文

【摘要】：具有高尺寸精度、高表面质量和极高壁厚均匀性要求的纯铁薄壁球壳是某试验中的关键零件,但纯铁切削时切屑变形大且极易形成积屑瘤、切削力大、刀具磨损严重,使得纯铁薄壁球壳的制造精度难以有效保证,迫切需要对影响并制约纯铁薄壁球壳加工精度的基础科学问题和关键技术进行深入研究和试验验证,从而推动纯铁薄壁球壳工艺技术的进步。本文主要研究工作包括:(1)采用直角切削试验对比研究了纯铁、10钢和45钢的切削加工性,分析了纯铁切屑形成机理及工艺参数对切屑变形的影响规律。结果表明,纯铁属于典型的高塑性、高韧性类难加工材料,具有切削力大、切屑变形严重、刀-屑接触长度大等特征,并呈现显著的剪切滑移变形,采用高切削速度、水冷方式和大前角刀具有利于改善纯铁材料的切削加工性。(2)采用分离式Hopkinson压杆和材料试验机进行了纯铁材料动态及准静态力学性能试验,获取了高温(20-800℃)、高应变率(104-5×104-1s)下的应力-应变曲线,建立了基于Power-Law模型的本构方程。根据实测的纯铁材料热物理属性和刀-屑平均摩擦系数,并对本构方程中应变强化参数进行修正,建立了纯铁材料切削仿真模型。切削力和切屑形态的仿真与试验结果对比表明,仿真模型能够用于纯铁粗加工阶段的工艺参数的优化。(3)研究了纯铁车削过程冷却润滑方式和工艺参数对非涂层刀具耐用度的影响规律。结果表明,微量润滑方式有利于提高刀具耐用度,刀具磨损形式以后刀面磨损和主、副切削刃处的沟槽磨损为主,扩散磨损、氧化磨损和黏结磨损是其主要磨损机理。分析了冷却润滑方式对刀具耐用度的影响机制,提出了采用K313+WS2和KC5010涂层刀具并结合MQL方式可有效提高纯铁精加工过程的刀具耐用度。(4)从切削过程力-热耦合角度研究了工艺参数对工件表面完整性的影响规律。结果表明,纯铁已加工表面产生撕裂、沟槽、碎屑、凹坑、鳞刺、塑性和侧向流动等缺陷;实测表面粗糙度远大于理论值,且表面加工硬化现象严重,表层晶粒呈扭曲、拉伸状塑性变形;工件表面切向和轴向均呈残余拉应力,且切向应力大于轴向应力。(5)分析了影响纯铁薄壁球壳加工精度的关键因素,探讨了刀具对刀误差及刀尖半径轮廓误差对球面轮廓精度的影响规律及控制措施。结合有限元方法,研究了装夹力、端面平面度误差和切削力对工件变形的影响,优化了装夹方法、切削工艺参数并提出平面度误差控制方法,加工的纯铁薄壁球壳尺寸精度、表面质量均满足设计要求。
[Abstract]:The thin wall spherical shell of pure iron with high size accuracy, high surface quality and high wall thickness uniformity is the key part in a certain test. However, chip deformation is large and chip nodules are easily formed in pure iron cutting, and the cutting force is large and the tool wear is serious.It is difficult to guarantee the manufacturing accuracy of pure iron thin wall spherical shell effectively. It is urgent to study and test the basic scientific problems and key technologies that affect and restrict the machining accuracy of pure iron thin wall spherical shell.So as to promote the technological progress of pure iron thin-wall spherical shell.In this paper, the chip-forming mechanism of pure iron chip and the influence of technological parameters on chip deformation are analyzed.The results show that pure iron is a kind of typical high plasticity and high toughness refractory material. It has the characteristics of large cutting force, serious chip deformation, large contact length of cutter and chip, and obvious shear slip deformation, and adopts high cutting speed.Water cooling method and large front angle cutter are beneficial to improve the machinability of pure iron material. (2) the dynamic and quasi-static mechanical properties of pure iron material are tested by separate Hopkinson compression bar and material testing machine.The stress-strain curves at high temperature (20-800 鈩，

本文编号：1720057