不锈钢论文：环境对不锈钢断裂韧性及断裂行为的影响.doc

304不锈钢论文：环境对304不锈钢断裂韧性及断裂行为的影响

【中文摘要】核电站反应堆堆内构件是核电站运行的“心脏”,与堆芯直接接触,是影响电站寿命的关键部件,其主要用材为核级304不锈钢。由此,针对304不锈钢在核电的应用问题,开展了大量的研究工作。迄今为止已经对304不锈钢的力学性能、腐蚀等问题进行了系统研究。考虑到材料的微裂纹及其带来的使用安全问题,考察核电环境条件对304不锈钢断裂韧性以及断裂行为的影响规律,探讨其断裂机理,既具有实际意义,亦具有学术价值。本文以核级304不锈钢为对象,在模拟核电站回路环境下考察环境因素对不锈钢的断裂韧性及断裂行为的影响,以期为核电设备的安全提供基础数据。研究选取三点弯曲试样、采用J积分方法表征304不锈钢不同环境下断裂韧性。通过考察304不锈钢在大气中由室温至350℃、水浴中由室温到90℃、室温含氢温水中及试样充氢后的断裂韧性,探讨环境条件对其断裂韧性的影响。研究表明,304不锈钢的JQ值在大气及水浴条件下随温度的升高逐渐降低,但水浴及含氢温水对其没有明显影响,试样充氢后JQ值随试样氢含量的增加大幅降低。采用OM、SEM、XRD等分析了304不锈钢各种试验条件下断裂韧性试样的断裂行为。发现304不锈钢无论在室温还是高温下均以微孔聚合型韧性断裂为主,但室温断口以大尺寸韧窝通过次级韧窝连接为主要特征,随温度的升高断口的韧窝逐渐变小、变浅,350℃下已经观察不到次级韧窝。室温含氢温水条件下,由于水浴中饱和氢的浓度较低,致使裂纹尖端富集的氢未达到临界浓度,固此对304不锈钢的断裂韧性无明显的影响。充氢后的试样,由于形变时氢加剧了诱导基体发生马氏体相变,在马氏体处产生氢致微裂纹,使试样发生准解理脆性断裂,导致304不锈钢的断裂韧性大幅降低。
【英文摘要】Reactor internals of nuclear reactor are said to be the heart of nuclear power plant, which direct contact the reactor core, and are the key components for the life of nuclear power station. The main materials of reactor internals are the nuclear grade 304 stainless steel. The nuclear power application problems of 304 stainless steel have been studied abundantly. Up to now, the strength and corrosion of 304 stainless steel have been studied systematically. For considering microcracks and the servicing safe, the understanding for fracture toughness and fracture mechanism of 304 stainless steel have not only practical significance, but also have academic value. Based on such background, the effects of environmental factors on the fracture toughness and fracture behavior of the nuclear grade 304 stainless steel were carried out in the present research.Three-point bending specimens are used for characterizing the fracture toughness of 304 stainless steel, in this study. The effects of environmental factors on the fracture toughness of 304 stainless steel, such as temperature, water bath, warm water with hydrogen and hydrogen-charged specimens, were discussed.The results show that JQ of 304 stainless steel decreased gradually in air and water bath with the increasing temperature, but JQ don’t be influenced significantly by the water bath and warm water of containing hydrogen. JQ of charged 304 stainless steel decreased obviously with the increasing of hydrogen content in the specimens.Fracture behavior of 304 stainless steel in different testing environment was analyzed using Optical Microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD) technology. The morphology of 304 stainless steel appears mainly to be microvoid coalescence at room and elevated temperatures, and the dimples were connected by secondary dimples. The diameter and depth of dimples was decreased with the increasing temperature, and the secondary dimples could not be found at 350℃. For the low concentration of saturated hydrogen in the water bath, hydrogen concentration at the crack tip can’t reach a degree that influence crack propagation significantly so that fracture toughness of 304 stainless steel have no influence on warm water of containing hydrogen condition at room temperature. Hydrogen-induced martensite transformation in the matrix varied the fracture mechanism of 304 stainless steel. Hydrogen-induced microcrack occurred in the vicinity of martensite and induced quasi-cleavage brittle fracture. Therefore, fracture toughness of 304 stainless steel decrease greatly.
【关键词】304不锈钢 断裂韧性 温度 水浴 氢致马氏体
【英文关键词】304 stainless steel fracture toughness testing temperature water bath hydrogen-induced martensite

【目录】环境对304不锈钢断裂韧性及断裂行为的影响

摘要

5-6

Abstract

6-7

目录

8-11

第1章 绪论

11-27

1.1 引言

11-13

1.1.1 世界核电行业发展态势

11-12

1.1.2 中国核电发展现状

12-13

1.2 堆内构件设计要求和结构简述

13-14

1.3 堆内构件用不锈钢

14

1.4 宏观断裂力学的发展概况

14-17

1.5 断裂韧性简介

17-18

1.6 J积分

18-25

1.6.1 J积分定义

18-20

1.6.2 J积分的性质

20-21

1.6.3 J积分测试标准

21-22

1.6.4 J积分测试方法

22-23

1.6.5 J积分和裂纹扩展曲线

23

1.6.6 J积分的应用

23-24

1.6.7 延性断裂韧性J_(Ic)的研究现状

24-25

1.6.8 影响断裂韧度的因素

25

1.7 本研究的目的、意义及主要研究内容

25-27

1.7.1 本研究的目的、意义

25-26

1.7.2 主要研究内容

26-27

第2章 试验材料及方法

27-35

2.1 试验材料

27

2.2 试验方法

27-35

2.2.1 显微组织观察

27

2.2.2 拉伸试验

27-29

2.2.3 充氢试验

29

2.2.4 断裂韧性试验

29-34

2.2.5 扫描电子显微镜(SEM)观察

34

2.2.6 X射线衍射(物相)(XRD)观察

34-35

第3章 温度对304不锈钢断裂韧性的影响

35-45

3.1 试验结果

35-42

3.1.1 显微组织

35

3.1.2 拉伸试验

35-36

3.1.3 加载速率对含氢温水中304不锈钢断裂韧性的影响

36-38

3.1.4 温度对大气中304不锈钢断裂韧性的影响

38-39

3.1.5 温度对水浴中304不锈钢断裂韧性的影响

39-40

3.1.6 断口分析

40-42

3.2 温度对断裂韧性影响机理分析

42

3.3 韧窝的形成机制

42-44

3.4 本章小结

44-45

第4章 充氢对304不锈钢断裂韧性的影响

45-52

4.1 试验结果

45-49

4.1.1 充氢试验

45

4.1.2 充氢对304不锈钢断裂韧性的影响

45-46

4.1.3 X射线衍射(物相)分析

46-48

4.1.4 断口分析

48-49

4.2 氢对断裂韧性影响机理分析

49-51

4.2.1 氢诱发304不锈钢产生马氏体相变

49

4.2.2 静水应力致氢在马氏体处富集

49-50

4.2.3 氢致马氏体导致304不锈钢准解理断裂

50-51

4.3 本章小结

51-52

第5章 结论

52-53

参考文献

53-57