17-4PH不锈钢热变形行为研究

发布时间：2018-06-20 08:34

本文选题：17-4PH不锈钢 + 高温塑性变形　；参考：《江苏大学》2017年硕士论文

【摘要】：17-4PH不锈钢作为重要的核反应堆结构材料,被西方大国广泛应用于如轻水反应堆(LWR)和压水反应堆(PWR)的阀杆等核电站结构材料。近年来对其的研究主要集中在17-4PH不锈钢的热处理工艺方面,在热变形行为方面的研究鲜有报道。本文采用Gleeble-3500热力模拟试验机对该钢进行热压缩实验,采集相关实验数据,通过回归拟合等数学计算了17-4PH不锈钢高温塑性变形过程中的流变应力、应变速率、形变温度之间的定量关系。并通过OM、TEM等手段对材料在热压缩过程中的组织进行了研究,最后基于实验结果并利用材料动态模型建立17-4PH不锈钢的热加工图,根据对该热加工图提出合理的热加工工艺参数区域,研究主要结论如下:(1)17-4PH不锈钢在高温压缩过程中,流变应力随应变速率的降低而降低,表明17-4PH不锈钢为正应变速率敏感材料。当温度的升高时,流变应力也会降低。同为T=1000℃,ps从e·=0.01s-1时113.42MPa增长至e·=5s-1时的232.04MPa;同为e0.01s1·-(28),ps从T=1100℃的140.57MPa增高至T=950℃的249.49MPa。温度和应变速率的共同作用可以通过lnZ值进行反映。(2)在热变形过程中,当T=1100℃、e·=0.01s-1和T=1050℃、e·=0.01s-1时,出现明显的峰值应力特征,此时动态再结晶软化机制占据主导作用,而在T≤1100℃、·-1ε≤5s其他大部分条件下,材料的动态回复作为主导作用的情况居多。(3)当变形温度恒定时,不同的应变速率下的17-PH不锈钢热压缩试样微观组织形态存在显著差异,随着应变速率的提高,加工硬化作用越来越明显,晶粒沿流变方向拉长,动态软化程度降低。当应变速率恒定时,随着温度的升高,再结晶程度变大,晶粒畸变程度降低,动态再结晶晶粒的体积分数相应增加。(4)17-4PH不锈钢峰值应力本构方程为:其与实际测量平均误差为5.62%,在误差允许范围内。(5)根据动态再结晶理论,建立起了动态再结晶的临界应变模型,当ce3e,材料在热压缩过程中开始发生动态再结晶:30.154exp(47474.95 9.04 / 8.314)X10pe eT-·(28)0.8c pe(28)e(6)基于动态材料模型绘制了17-4PH不锈钢的热加工图。变形初期材料容易发生失稳。当e=0.3、0.6,热加工图特征变化不显著,流变失稳区所对应的功率耗散效率均迅速下降,当e=0.1时,失稳区域所对应功率耗散效率小于0.16,低于耗散峰值的一半,同样,e=0.3、0.6时,失稳区耗散效率分别小于0.12和0.15,均远远低于峰值耗散效率。(7)当e=0.6时,17-4PH不锈钢适宜的加工参数区间为T=1062℃~1100℃、e·≤0.023s-1。不宜进行加工的参数区间为T=950℃~1028℃、e·=0.27s-1~5s-1。
[Abstract]:As an important structural material for nuclear reactor, 17-4PH stainless steel has been widely used in the western countries as the structural materials of the stem of the valve stem such as the light water reactor (LWR) and the pressurized water reactor (PWR). In recent years, the research on the thermal treatment of 17-4PH stainless steel is mainly concentrated on the thermal deformation behavior, and the research on the thermal deformation behavior is rarely reported. The hot compression test of the steel was carried out by the Gleeble-3500 thermal simulation test machine, and the relevant experimental data were collected. The quantitative relationship between the rheological stress, the strain rate and the deformation temperature in the high temperature plastic deformation process of the 17-4PH stainless steel was calculated by regression fitting and so on. The microstructure of the material in the process of thermal compression was carried out by means of OM and TEM. In the end, based on the experimental results and using the dynamic model of the material to establish the hot working diagram of 17-4PH stainless steel, the main conclusions are as follows: (1) in the process of high temperature compression, the flow strain of 17-4PH stainless steel decreases with the decrease of the strain rate, indicating that 17-4PH is not. Rust steel is a positive strain rate sensitive material. When the temperature rises, the rheological stress will also decrease. The same is the 232.04MPa at T=1000 C, PS from e to =0.01s-1 to e. =5s-1, and the same as e0.01s1. (28), the common effect of PS from T=1100 to the temperature and the strain rate can be carried out through the values. (2) (2) during the process of thermal deformation, when T=1100, e. =0.01s-1 and T=1050 C, e. =0.01s-1, there is obvious peak stress characteristics. At this time, the dynamic recrystallization softening mechanism occupies the dominant role, while the dynamic recovery of the material is dominant under the T < 1100 C, -1 e or less 5S. (3) deformation temperature At constant time, there are significant differences in the microstructure of 17-PH stainless steel under different strain rates. With the increase of the strain rate, the working hardening is becoming more and more obvious, the grain grows along the flow direction and the dynamic softening degree decreases. When the strain rate is constant, the degree of recrystallization becomes larger and the grain distortion is changed with the increase of temperature. The volume fraction of the dynamic recrystallized grain increases correspondingly. (4) the constitutive equation of the peak stress stress of 17-4PH stainless steel is: the average error is 5.62% and within the allowable range of error. (5) the critical strain model of dynamic recrystallization is established according to the dynamic recrystallization theory. When ce3e, the material begins to occur during the thermal compression process. Dynamic recrystallization: 30.154exp (47474.95 9.04 / 8.314) X10pe eT-. (28) 0.8C PE (28) e (6) based on the dynamic material model to draw a hot working diagram of the 17-4PH stainless steel. The initial deformation of the material is easy to be unstable. When e=0.3,0.6, the characteristics of the thermal processing diagram are not significant, the power dissipation efficiency of the rheological instability zone decreases rapidly, when e=0.1, The power dissipation efficiency of the unstable region is less than 0.16, which is lower than half of the dissipative peak, and the dissipation efficiency of the unstable region is less than 0.12 and 0.15, respectively, when e=0.3,0.6 is far below the peak dissipation efficiency. (7) when e=0.6, the suitable processing parameters of 17-4PH stainless steel are T= 1062 C ~1100, e. < 0.023s-1. is not suitable for processing parameters. The interval is T=950 C ~1028 C, e. =0.27s-1~5s-1.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.71

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