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金属学报  2020, Vol. 56 Issue (8): 1057-1066    DOI: 10.11900/0412.1961.2019.00449
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不锈钢堆焊层稀释率对核电接管安全端试环焊接接头组织和力学性能的影响
张茂龙1,2, 鲁艳红1, 陈胜虎3, 戎利建3(), 陆皓2
1 上海电气核电设备有限公司 上海 201306
2 上海交通大学材料科学与工程学院 上海 200240
3 中国科学院金属研究所中国科学院核用材料与安全评价重点实验室 沈阳 110016
Effect of Dilution Ratio of the First 309L Cladding Layer on the Microstructure and Mechanical Properties of Weld Joint of Connecting Pipe-Nozzle to Safe-End in Nuclear Power Plant
ZHANG Maolong1,2, LU Yanhong1, CHEN Shenghu3, RONG Lijian3(), LU Hao2
1 Shanghai Electric Nuclear Power Equipment Co. Ltd. , Shanghai 201306, China
2 School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
3 Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
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摘要: 

利用OM、SEM、XRD、EPMA和EBSD等手段,分析了2种堆焊工艺制备核电接管安全端试环中309L堆焊层的微观组织及其对焊接接头力学性能的影响。结果表明,不同堆焊工艺制备试环的309L堆焊层组织均为奥氏体和马氏体,但堆焊稀释率决定了马氏体的形态和数量。较低的堆焊稀释率下,堆焊层组织为奥氏体和板条马氏体,而较高的堆焊稀释率会显著提高板条马氏体的数量,当稀释率超过某一临界值后,促进针状马氏体的形成。堆焊稀释率直接影响试环接头的力学性能,较高的堆焊稀释率下,接头经180°侧弯后出现309L堆焊层引起的开裂现象,同时拉伸强度和延伸率显著降低。变形过程中,高的堆焊稀释率下309L堆焊层中形成的针状马氏体与奥氏体之间变形不协调,进而在界面处产生应力集中,易诱发裂纹,导致309L堆焊层成为优先开裂位置,是造成接头力学性能下降的主要原因。

关键词 堆焊稀释率微观组织力学性能开裂机理    
Abstract

The transition joint between austenitic stainless steel pipe and low alloy steel nozzle of the pressure vessel has attracted much attention due to the occurrence of failure during application. Usually, the low alloy steel vessel nozzle should be firstly buttered with several layers of austenitic stainless steel and then welded to the austenitic stainless steel pipe. Cracking phenomenon in the austenitic cladding layer sometimes occurs during fabrication of the transition joint, and the cracking mechanism is not very clear. It is worth noting that microstructure in the first buttering layer is largely dependent on the welding condition, because the variation of the buttering welding parameters would lead to different dilution ratios in the cladding layer. Therefore, it is essential to investigate the effect of dilution ratio of the cladding layer on the mechanical properties of the weld joint. In this work, microstructure of the 309L cladding layer under two kinds of buttering welding parameters was analyzed using OM, SEM, XRD, EPMA and EBSD, and its effects on the mechanical properties of the weld joints were further studied. The results show that duplex microstructure (austenite+martensite) are present in the 309L cladding layers under two kinds of buttering welding parameters, but the dilution ratio could determine the morphology and amount of martensite phase. Microstructure consisting of austenite and lath martensite is found in the 309L cladding layer with a lower dilution ratio. A higher dilution ratio could increase the amount of lath martensite. The formation of needle-like martensite occurs when the dilution ratio exceeds a critical value. The dilution ratio in the 309L cladding layers directly affects the mechanical properties of weld joint. For the weld joint with a lower dilution ratio, no cracking phenomonen is observed during three-point bending test, and the specimens fracture at the weld fusion zone after tensile test. For the weld joint with a higher dilution ratio, cracking phenomenon initiated at the 309L cladding layer is present during three-point bending test, and a significat reduction in the tensile strength and elongation is observed. During deformation, the strain incompatibility between needle-like martensite and austenite is produced, leading to the formation of microcracks at the interfaces. The preferential cracking at the 309L cladding layer with a higher dilution ratio leads to the degradation of mechanical properties of the weld joint.

Key wordsbuttering welding    dilution ratio    microstructure    mechanical property    cracking mechanism
收稿日期: 2019-12-25     
ZTFLH:  TG44  
基金资助:国家自然科学基金项目(51871218);中国科学院核用材料与安全评价重点实验室开放课题项目(2019NMSAKF03)
通讯作者: 戎利建     E-mail: ljrong@imr.ac.cn
Corresponding author: RONG Lijian     E-mail: ljrong@imr.ac.cn
作者简介: 张茂龙,男,1965年生,教授级高工

引用本文:

张茂龙, 鲁艳红, 陈胜虎, 戎利建, 陆皓. 不锈钢堆焊层稀释率对核电接管安全端试环焊接接头组织和力学性能的影响[J]. 金属学报, 2020, 56(8): 1057-1066.
Maolong ZHANG, Yanhong LU, Shenghu CHEN, Lijian RONG, Hao LU. Effect of Dilution Ratio of the First 309L Cladding Layer on the Microstructure and Mechanical Properties of Weld Joint of Connecting Pipe-Nozzle to Safe-End in Nuclear Power Plant. Acta Metall Sin, 2020, 56(8): 1057-1066.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2019.00449      或      https://www.ams.org.cn/CN/Y2020/V56/I8/1057

MaterialCSiMnPSNiCrMoCuCoAlTiNFe
SA5080.2100.221.350.0040.0030.870.21-0.04-0.02-0.01Bal.
316LN0.0140.381.100.0240.00411.216.22.13-0.01--0.11Bal.
EQ309L0.0120.371.630.0130.00313.224.00.060.030.04-0.0070.04Bal.
EQ308L0.0120.341.630.0130.00310.120.60.090.030.04-0.0060.04Bal.
ERNiCrFe-70.0240.160.240.0030.00160.428.90.010.01<0.010.70.50.019.09
表1  接管安全端焊接试环件中各部分材料的化学成分 (mass fraciton / %)
图1  接管安全端焊接试环的异种金属焊接接头示意图及不锈钢堆焊层形貌
图2  侧弯试样及拉伸试样示意图
图3  2种埋弧焊(SAW)工艺制备接管安全端试环中309L堆焊层微观组织的OM和SEM像
图4  2种SAW工艺制备接管安全端试环中不锈钢堆焊层的XRD谱
图5  2种SAW工艺制备接管安全端试环中不锈钢堆焊层的元素分布
图6  2种SAW工艺制备接管安全端试环接头经180°侧弯后的宏观形貌
图7  2种SAW工艺制备接管安全端试环接头的拉伸应力-应变曲线
图8  2种SAW工艺制备接管安全端试环接头的拉伸断口侧面和S2试环的断口形貌
图9  S2试环接头拉伸断口附近截面组织的OM像
图10  基于Schaeffler相图预判的309L堆焊层微观组织[18]
图11  2种SAW工艺制备接管安全端试环中309L堆焊层的相分布图
Weld jointMass fraction of element / %

Dilution ratio

%

CSiMnNiCr[Ni][Cr]
S10.0760.571.388.8115.7211.7816.5836
S20.0910.511.337.8613.6911.2614.4645
表2  2种SAW工艺制备接管安全端试环中309L堆焊层的合金元素含量及稀释率
图12  2种SAW工艺制备接管安全端试环接头的显微硬度分布
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