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金属学报  2017, Vol. 53 Issue (1): 57-69    DOI: 10.11900/0412.1961.2016.00135
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国产核电安全端异种金属焊接件的微观结构及局部性能研究
明洪亮1,2,张志明1,王俭秋1(),韩恩厚1,苏明星3
1 中国科学院金属研究所核用材料与安全评价重点实验室, 辽宁省核电材料安全与评价技术重点实验室 沈阳 110016
2 中国科学院大学 北京 100049
3 上海核电装备焊接及检测工程技术研究中心 上海 201306
Microstructure and Local Properties of a Domestic Safe-End Dissimilar Metal Weld Joint by Using Hot-Wire GTAW
Hongliang MING1,2,Zhiming ZHANG1,Jianqiu WANG1(),En-Hou HAN1,Mingxing SU3
1 Liaoning Key Laboratory for Safety and Assessment Technique of Nuclear Materials, Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
3 Shanghai Research Center for Weld and Detection Engineering Technique of Nuclear Equipment, Shanghai 201306, China
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摘要: 

利用OM、SEM、显微硬度仪、微小试样拉伸实验及慢应变速率拉伸实验对国产带热丝隔离层核电安全端焊接件不同部位的微观结构及局部的力学性能和应力腐蚀敏感性进行了研究。发现,在SA508/52Mb界面处的52Mb中具有大量的对应力腐蚀敏感的I型晶界及II型晶界,导致此界面具有最高的应力腐蚀敏感性;SA508热影响区存在明显的组织过渡;316LN热影响区中随着距熔合线距离的增加,重位点阵(CSL)晶界的数量分数逐渐增大,Σ3晶界与理想的Σ3晶界的偏差角减小,残余应变逐渐减小,残余应变的最高值出现在对接焊底焊位置处的316LN热影响区中,导致316LN的热影响区也具有较高的应力腐蚀敏感性。焊接件不同部位的力学性能存在较大的差异。对于硬度分布而言,显微硬度变化最剧烈的位置在SA508/52Mb界面附近,且此界面附近的52Mb具有最高的硬度,此界面附近的SA508脱C区具有最低的硬度。强度的变化趋势与硬度的变化趋势类似。一般强度高的地方断裂应变低。焊接件不同位置的性能差异主要取决于不同部位的微观结构(包含组织、成分等)差异。

关键词 异种金属焊接微观结构局部力学性能应力腐蚀敏感性残余应变    
Abstract

Dissimilar metal weld joints (DMWJ) widely exist in the nuclear power plants to join the different parts which are made of different structural materials. Among these DMWJs, safe-end DMWJ has attracted much attention of researchers and operating enterprises, as premature failures, mainly stress corrosion cracking failures, have occurred in these kinds of joints. However, DMWJ with 52M as filler metal in the nuclear power plants has no in-service experience. To ensure the structural integrity of the weld joint and the safe operation of the future plants, the microstructure and local properties of a domestic safe-end DMWJ by using hot-wire gas tungsten arc welding (GTAW) technology was studied in detail by OM, SEM, micro-hardness testing, local mechanical tensile testing and slow strain rate tests. The tensile tests were performed at room temperature with the tensile speed of 5 μm/s while the slow strain rate tests were conducted in simulated primary water containing 1500 mg/L B as H3BO3 and 2.3 mg/L Li as LiOH with 2 mg/L dissolved oxygen at 325 ℃. A large amount of type I boundaries and type II boundaries which are susceptible to stress corrosion cracking (SCC) exist in 52Mb near the SA508/52Mb interface and result in the highest SCC susceptibility of this interface. Microstructure transition was found in the SA508 heat affected zone (HAZ). In 316LN HAZ, increasing the distance from the fusion boundary, the number fraction of CSL boundaries increase while the residual strain decreases, resulting in the second-highest SCC susceptibility of 316LN HAZ. In 52M, residual strain distributes randomly but not uniformly, the residual strain is prone to accumulate at the grain boundaries. Dramatic changes of mechanical properties are observed across the joint, especially at the SA508/52M interface. The differences of the local microstructure and chemical composition lead to the differences of the local properties of the weld joint.

Key wordsdissimilar metal    weld joint,    microstructure,    local mechanical property,    stress corrosion cracking susceptibility,    residual strain
收稿日期: 2016-04-13      出版日期: 2016-10-09
基金资助:资助项目 国家自然科学基金项目No.51301183,上海市科委项目No.14DZ2250300和中国科学院前沿科学重点研究项目No.QYZDY-SSW-JSC012

引用本文:

明洪亮,张志明,王俭秋,韩恩厚,苏明星. 国产核电安全端异种金属焊接件的微观结构及局部性能研究[J]. 金属学报, 2017, 53(1): 57-69.
Hongliang MING,Zhiming ZHANG,Jianqiu WANG,En-Hou HAN,Mingxing SU. Microstructure and Local Properties of a Domestic Safe-End Dissimilar Metal Weld Joint by Using Hot-Wire GTAW. Acta Metall, 2017, 53(1): 57-69.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2016.00135      或      http://www.ams.org.cn/CN/Y2017/V53/I1/57

表1  焊接件不同部位主要化学成分
图1  焊接实物图和焊接件截面示意图及取样示意图
图2  小尺寸拉伸试样尺寸示意图
图3  慢应变速率拉伸实验试样尺寸示意图
图4  小尺寸拉伸试样在焊接件中的位置示意图
图5  SA508母材、316LN母材、 52Mb和 52Mw 的OM像
图6  SA508/52Mb界面和52Mw/316LN界面的OM像
图7  SA508低合金钢热影响区的OM像
图8  316LN热影响区的OM像
图9  无马氏体区的SA508/52Mb界面形貌及主要金属元素分布
图10  带有马氏体区的SA508/52Mb界面形貌及主要金属元素分布
图11  52Mw/316LN界面形貌及主要金属元素分布
图12  H1、H4及H6试样EBSD分析
图13  H4试样SA508/52Mb界面的图像质量(image quality, IQ)图、IPF、KAM图及相分布图
图14  沿图1b中L1线的显微硬度分布及界面处显微硬度压痕
图15  沿图1b中L2线的显微硬度分布及界面处显微硬度压痕
图16  沿图1b中L3线的显微硬度分布及界面处显微硬度压痕
图17  SA508/52Mb界面的SEM像及C元素分布
图18  焊接件不同部位室温下屈服强度、抗拉强度及断裂应变
图19  焊接件不同部位在模拟核电高温高压水环境中慢应变速率拉伸实验结果
图20  H1试样中316LN侧距熔合线不同距离位置处Σ3晶界与理想的Σ3晶界偏差角分布图
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