核主泵屏蔽套用薄板激光焊接变形预测及调控

发布时间：2018-01-24 03:24

本文关键词： 核主泵屏蔽套脉冲激光焊接 Hastelloy C-276 数值模拟残余变形　出处：《大连理工大学》2014年博士论文　论文类型：学位论文

【摘要】：第三代核电站(AP1000)反应堆冷却剂泵(核主泵)采用了屏蔽式电机,而屏蔽式电机中屏蔽套的制造质量是保证核主泵安全可靠运行的重要基础。屏蔽套主要由哈氏合金(Hastelloy C-276)薄板经过剪裁和焊接工艺制造而成。由于定子屏蔽套壁厚在0.3～0.5mmin之间,长度达3000mm以上,直径为565mm,而且其直径偏差仅为±0.076mm,使役寿命更长达60年,因此屏蔽套的制造工艺精度要求非常高。本文针对屏蔽套成形制造高精度和长寿命的设计要求,采用脉冲激光焊接技术,以数值模拟为主要研究手段,分析了Hastelloy C-276薄板脉冲激光焊接应力应变及变形分布规律,提出了等效热载荷的计算方法及焊接应力变形的调控策略,揭示了调控参数与屏蔽套尺寸精度的映射关系,为核主泵屏蔽套的自主化制造提供理论基础和工程指导。主要研究内容及结论如下： (1)建立了Hastelloy C-276薄板脉冲激光焊接热力过程的有限元模型,模型中考虑了材料随温度变化的热物理和力学性能以及脉冲激光能量间歇加载方式。分析了脉冲激光焊接温度场、瞬态及残余应力应变和变形场的分布特点。通过焊接实验及相关检测设备,测量了温度场和残余变形,两者吻合较好,验证了模拟结果的准确性。 (2)通过横向塑性应变的演变历程,分析了横向收缩变形的产生机制,发现了压缩塑性应变是横向收缩变形的直接原因,提出了考虑横向挠曲变形的表征方法,并获得了工件尺寸对横向收缩变形的影响规律。以纵向残余应力分布特征为基础,提出了一种利用纵向残余应力沿横截面分布的函数关系并考虑夹具拘束来确定等效热载荷的计算方法,并采用弹性屈曲分析,实现了对超薄大长径比屏蔽套焊后结构稳定性的判断。 (3)采用位移约束假设代替夹具刚性固定拘束的方法,分析了拘束距离对焊接瞬态及残余应力应变和变形的影响规律。随着拘束距离的减小,纵向残余压应力和横向残余拉应力的峰值都呈减小趋势,而纵向残余拉应力的峰值则呈增大趋势；焊接纵向和横向挠曲变形及横向收缩变形都表现为减小的趋势,特别是横向收缩变形的减小幅度非常明显；采用减小拘束距离的方法,能够实现屏蔽套周长尺寸精度的有效控制。 (4)针对夹具刚性固定拘束对纵向残余拉应力调控效果的不足,提出了基于一定拘束条件下采用动态温差拉伸对纵向残余应力与失稳变形进行调控的方法。研究了热沉参数对焊接温度场、瞬态及残余应力和变形场的影响规律。随着激冷位置靠近热源或激冷强度增加,纵向残余应力和挠曲变形呈显著减小趋势,而横向收缩变形却呈增大趋势。通过优选方法确定调控参数,能为核主泵屏蔽套高精度低应力焊接制造提供生产指导。
[Abstract]:The third generation nuclear power plant AP1000) reactor coolant pump (nuclear main pump) uses the shielded motor. The manufacturing quality of the shield sleeve in the shielded motor is an important basis to ensure the safe and reliable operation of the nuclear main pump. The shield sleeve is mainly made of Hastelloy C-276). The thin plate is made by cutting and welding process. The thickness of stator shield sleeve is between 0.3 min and 0.5mmin. The length is more than 3000 mm, the diameter is 565 mm, and the diameter deviation is only 卤0.076 mm, so the service life is even longer than 60 years. Therefore, the manufacturing precision of the shield sleeve is very high. In this paper, the pulse laser welding technology is adopted to design the high precision and long life of the shield sleeve. Numerical simulation is the main research method. The distribution of stress, strain and deformation in pulsed laser welding of Hastelloy C-276 thin plate is analyzed. The calculation method of equivalent thermal load and the control strategy of welding stress and deformation are put forward. The mapping relationship between the control parameters and the dimensional accuracy of the shield sleeve is revealed, which provides the theoretical basis and engineering guidance for the autonomic manufacture of the nuclear main pump shield sleeve. The main research contents and conclusions are as follows: 1) the finite element model of thermal process for pulsed laser welding of Hastelloy C-276 thin plate is established. The thermal physical and mechanical properties of the material with temperature variation and the intermittent loading mode of pulsed laser energy are considered in the model. The temperature field of pulsed laser welding is analyzed. The distribution characteristics of transient and residual stress strain and deformation field. The temperature field and residual deformation are measured by welding experiment and related testing equipment. The results are in good agreement with each other and verify the accuracy of the simulation results. 2) through the evolution of transverse plastic strain, the mechanism of transverse shrinkage deformation is analyzed, and the direct cause of transverse shrinkage deformation is found out. A representation method considering transverse flexural deformation is proposed, and the influence of workpiece size on transverse shrinkage and deformation is obtained, which is based on the longitudinal residual stress distribution. A method for determining the equivalent thermal load by using the functional relation of longitudinal residual stress distribution along the cross section and the constraint of the fixture is proposed, and the elastic buckling analysis is used. The structure stability of the shield sleeve with super thin and large aspect ratio is judged. (3) the influence of restraint distance on welding transient, residual stress, strain and deformation is analyzed by using displacement constraint hypothesis instead of rigid fixation constraint of fixture. With the decrease of restraint distance, the effect of restraint distance on welding transient, residual stress, strain and deformation is analyzed. The peak value of longitudinal residual compressive stress and transverse residual tensile stress decreased, while the peak value of longitudinal residual tensile stress increased. The longitudinal and transverse bending deformation and the transverse shrinkage deformation of the welding show a decreasing trend, especially the amplitude of the transverse shrinkage deformation is very obvious. The precision of circumference of shield sleeve can be controlled effectively by reducing the constraint distance. 4) the effect of rigid fixation on the longitudinal residual tensile stress is insufficient. A method of controlling longitudinal residual stress and unstable deformation by dynamic temperature differential tension under certain restraint conditions is proposed. The effect of heat sink parameters on welding temperature field is studied. The effect of transient and residual stress and deformation field. The longitudinal residual stress and flexural deformation decreased significantly with the increase of the cooling position near the heat source or the intensity of the cooling. However, the transverse shrinkage and deformation show an increasing trend, and the optimal selection method can be used to determine the control parameters, which can provide the production guidance for the manufacture of high precision and low stress welding of the shield sleeve of the nuclear main pump.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM623;TG456.7

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