不锈钢堆焊层在Cl-溶液中的腐蚀性能研究

采用浸泡腐蚀试验方法,研究了不锈钢堆焊层材料在Cl^-溶液中的腐蚀情况,并通过金相显微镜、扫描电子显微镜、能谱分析观察表面形貌。研究表明,室温条件下堆焊层材料未发生任何腐蚀。在高温条件下,Cl^-的存在诱导了点腐蚀的发生,且随着Cl^-浓度的增加,点腐蚀加剧;较高浓度的Cl^-可导致缝隙内金属元素Cr的流失,缝隙腐蚀加深;应力腐蚀裂纹有沿晶开裂的特征,应力腐蚀敏感性随Cl^-浓度的增加有提高的趋势。     

核级不锈钢堆焊材料腐蚀性能研究

采用GB43 3 4 7 84和法国RCC MMC1 3 1 0对国产两种堆焊材料进行了点腐蚀、晶间腐蚀试验 ,在模拟压水堆核电站介质 (温度 3 45℃ ,80 0mg/LB ,2mg/LLi)条件下 ,研究了堆焊材料的应力腐蚀和均匀腐蚀性能。试验结果表明 :在高温含B水中 ,U型试样试验 5 0 0 0h后无应力腐蚀破裂 ,静态月平均腐蚀速率小于 2mg/dm2 。两种堆焊材料均具有优良的耐腐蚀性。     

小波在不锈钢堆焊层下裂纹楞边检测中的应用

根据噪声、材料杂波、裂纹回波、楞边回波等在Ｃα空间中Ｌｉｐｓｃｈｉｔｚ常数α的差异提出了在不锈钢堆焊层下裂纹的超声检测信号模型。经采样且模型化信号的小波变换模极大值因α的值不同而随分辨尺度ｊ的变化关系不同。通过小波分析实现了裂纹楞边回波的检测。     

反应堆压力容器接管堆焊层缺陷分析及处理

从焊接工艺角度出发,介绍了某反应堆压力容器接管简体组件的出口接管堆焊层的质量问题及其缺陷处理.在分析不锈钢堆焊层脱层原因基础上,论述了相应的处理和返修工艺.     

核承压设备不锈钢堆焊层碳元素含量质量控制

针对核承压设备制造过程中多次出现的不锈钢堆焊层碳元素含量超标问题,为找出相应解决控制措施,从材料、工艺方法和参数、堆焊环境条件、检测过程控制等方面进行了全面分析研究。分析研究表明,要有效控制堆焊层的碳元素含量须从多个方面综合采取措施,实践来看,能够起到较好效果且可操作性较强的方式依次为:选取碳含量较低的合适焊材、调整工艺增加堆焊层数、严格控制堆焊环境清洁度等。     

热壁加氢反应器堆焊层表面裂纹疲劳扩展的数值模拟

介绍了应用三维断裂分析软件FRANC3D(Fracture Analysis Code in 3Dimensions)进行疲劳裂纹扩展分析的相关原理,利用该程序对热壁加氢反应器堆焊层表面裂纹在疲劳载荷作用下的扩展进行了数值分析;将数值模拟结果和相关试验结果进行了对比.结果表明:数值模拟和实际表面裂纹扩展路径基本相似;在加氢反应器使用寿命范围内,用FRANC3D程序预测的裂纹扩展速率比实验值保守.     

核级316L不锈钢管道射线插塞孔开裂原因分析

为查明某核电厂核级316L奥氏体不锈钢管道射线插塞孔裂纹显示的成因,对含插塞孔不锈钢管段的宏/微观形貌、化学成分、力学性能、维氏硬度、断口形貌、腐蚀产物、应力分布等进行了分析。结果表明：裂纹以沿晶方式扩展,断口呈冰糖块脆性断裂花样并伴有大量氧化腐蚀产物,属于典型的压水堆一回路水介质条件下由插塞孔局部应变-硬化导致的晶间应力腐蚀开裂。引起应变-硬化的主要原因是插塞孔和插塞的过盈配合以及射线插塞孔密封焊缝焊接残余应力过高。建议加强在役机组同类结构的检查,减少新建机组类似结构的使用。     

压水堆压力壳堆焊不锈钢的动电位再活化行为与晶间应力腐蚀破裂敏感性

用动电位再活化方法研究了压水堆压力壳堆焊不锈钢衬里材料的活化与再活化行为以及晶界形貌,用高温水恒变形和慢应变速率应力腐蚀破裂试验比较了晶间应力腐蚀破裂的敏感程应。结果表明再活化行为与晶间应力腐蚀破裂敏感性之间有一致关系。动电位再活化有可能作为核动力装置中不锈钢焊接件晶间应力腐蚀破裂敏感程度的无损检验方法。     

Nb-1Zr与316L不锈钢爆炸焊高温退火扩散层的显微组织分析

研究了Nb-1Zr合金与316L不锈钢爆炸焊在1 300 ℃退火后形成的互扩散层.该互扩散层宽度约为80 μm.用透射电子显微镜(TEM)分析观测到该扩散层中有大量针状析出相产生.经选区电子衍射(SADP)技术测定,析出相为亚稳定的ζ-(Nb, Ni)相,基体相为(Ni,Cr,Nb,C)Fe-α合金.     

国产汽动泵平衡盘司太立合金堆焊层裂纹原因分析及改进

国产首台汽动泵在大修解体中发现其平衡盘的司太立合金堆焊层存在裂纹,本文通过对裂纹的微观形貌、能谱测量及裂纹剖面观察,得出裂纹产生的诱因。经过研究汽动泵转子的轴向力的计算过程、梳理司太立合金堆焊工艺和机械加工工艺的不足,总结出裂纹产生的根本原因。采取相应措施后,使用新工艺制造的平衡盘经过出厂试验验证,显著提升了司太立合金堆焊层抗裂纹产生及扩展能力,提升了设备可靠性,为后续华龙机组国产汽动泵优化改进提供了良好的工程参考。     

321不锈钢在低酸度硝酸铀酰溶液中的腐蚀特性

用称量法和电化学法研究了321不锈钢在不同浓度和pH值的硝酸铀酰溶液中的高温均匀腐蚀和电化学府蚀行为。均匀腐蚀试验结果表明．在选定的腐蚀条件下，321不锈钢样品在960h内，其表面光洁度无明显变化．腐蚀速率小于0．04mg/m^2.h，在低酸度的硝酸铀酰溶液中耐蚀。用腐蚀电入学法研究了321不锈钢在有溶解氧的硝酸铀酰溶液中的腐蚀电化学特性，测量了电极的腐蚀电位、腐蚀电流密度。经AES分析表明，电化学腐蚀后的样品在腐蚀膜中有一定量的铀．深度剖析含铀腐蚀膜的厚度为10—15nm。     

核级不锈钢焊接接头钝化膜耐蚀性能和半导体特性研究

采用电化学阻抗谱(EIS)、场发射扫描电子显微镜(SEM)、Auger扫描能谱仪(AES)以及容抗测试技术(M-S曲线),研究了316LN/316L不锈钢焊接接头在模拟压水堆一回路高温高压水中形成的钝化膜的耐蚀性能和半导体特性。结果表明,焊缝区、热影响区和母材区形成的钝化膜的耐蚀性能不同,热影响区钝化膜开路电位及电化学阻抗等均低于其他区域,说明热影响区钝化膜的耐蚀性能最差,这主要与钝化膜的致密程度、厚度及Cr氧化物的含量有关。M-S曲线表明,母材区钝化膜平带电位为-0.7V,较其他区域(-0.4V)负移,表明有BO-3等阴离子在钝化膜表面吸附,加之具有较低的施主和受主浓度,可排斥侵蚀离子的腐蚀,使之较其他区域有更强的耐蚀性能。     

焊接残余应力对316LN不锈钢应力腐蚀裂纹扩展速率的影响

核电站不锈钢管道焊接过程中引入的残余应力对焊接接头的应力腐蚀开裂性能有较大影响。本文针对一AP1000主管道316LN不锈钢焊接模拟件进行残余应力分析和应力腐蚀裂纹扩展速率测量,得到了焊后原始状态和去应力热处理状态的焊接热影响区材料在高温高压水中的应力腐蚀裂纹扩展速率。实验结果表明,焊接残余应力明显提高了热影响区的应力腐蚀裂纹扩展速率,且在含氢的压水堆一回路正常水化学下焊接残余应力的影响更加显著。     

Corrosion of Austenitic Stainless Steel in Steam Containing Cesium Hydroxide

Corrosion behavior of SUS-304L SS, which is used as a typical material for reactor structures has been studied under the steam containing CsOH at temperatures of 450~750°C. The steam was supplied by heating the aqueous solution of CsOH with concentrations 0~320 mM at 110°C. The mass gain by oxygen uptake increases parabolically with reaction time. Since the activation energy of reaction rate constant is consistent with that of self diffusion of Fe in Fe₃O₄, it can be considered that the corrosion reaction is determined by the diffusion rate of Fe atoms in the outer oxide layer. The effect of CsOH on the corrosion reaction under the steam is large in the initial stage of the reaction, but small in the final stage. The mechanism of corrosion reaction has been discussed on the basis of microstructure and composition of the reaction layers.     

304奥氏体不锈钢在硝酸溶液体系中的电化学腐蚀行为

采用极化曲线测量法对304不锈钢在硝酸溶液体系中的电化学耐蚀性能进行了测试,分别研究了在硝酸溶液中添加硝酸盐、草酸、乙酸、柠檬酸等成分对304不锈钢电化学腐蚀行为的影响。结果表明,在硝酸溶液中,硝酸盐的加入能够抑制不锈钢的电化学腐蚀,而草酸能够显著增强溶液对不锈钢的电化学腐蚀能力,在硝酸和草酸溶液体系中加入1g/L柠檬酸后,自腐蚀电流由6.02μA/cm~2上升到22.8μA/cm~2,对电流腐蚀有较明显的促进作用。     

Corrosion of Type 304L Stainless Steel in Concentrated Plutonium Nitrate Solution

Dryout experiments of water have been conducted in an annulus with inside heating (heat flux from inner wall only) under high-pressure, low-flow and mixed inlet conditions which are of importance in the core thermal-hydraulic behavior during a loss-of-coolant accident (LOCA) and also partially during an anticipated transient without scram (ATWS) of a nuclear reactor. The experimental conditions have covered ranges of pressure of 3 MPa, mass flux from 105 to 320 kg/m²·s and inlet quality from 0.15 to 0.90. The dryout data have been compared with several existing empirical critical heat flux (CHF) correlations and a new correlation. The Katto correlation predicts best the CHF among the existing correlations examined. However, even the Katto correlation overpredicts the CHF by factors up to 2 at about 1/6 data points of the present dryout data. The present dryout data are divided into two groups (regions) according to the value of a non-dimensional number l _bo/d _he, where l _bo is the assumed boiling length and dh, the heated equivalent diameter. A new correlation covering both the regions has been developed by correlating the present dryout data in terms of two non-dimensional numbers. The new correlation performs best among the correlations examined in predicting the present dryout data.     

冷变形316不锈钢在高温水中的应力腐蚀开裂行为

对不同冷变形量的核级316和316L不锈钢在高温水中的应力腐蚀开裂(SCC)行为进行了研究。通过试验,对溶解氧、氯离子和温度对裂纹扩展速率的影响进行了深入探讨和分析。试验结果显示,溶解氧和氯离子能明显加快材料的应力腐蚀开裂速率。当水化学条件一致时,325℃时的裂纹扩展速率较288℃时的裂纹扩展速率高。     

The Influence of Dissolved Hydrogen on the Corrosion of Type 304 Stainless Steels Treated with Inhibitive Chemicals in High Temperature Pure Water

In order to assess the influence of dissolved hydrogen on the intergranular stress corrosion cracking (IGSCC) characteristics of Type 304 stainless steels treated with inhibitive chemicals, electrochemical corrosion potential (ECP) measurements and slow strain rate tensile (SSRT) tests were conducted in high temperature pure water. A number of thermally sensitized specimens were prepared and then pre-oxidized in a 288°C pure water environment with the presence of 300ppb dissolved oxygen for 360h. Most of the specimens were then separately treated with various inhibitive chemicals including powdered zirconium oxide (ZrO₂), powdered titanium oxide (TiO₂), and zirconyl nitrate [ZrO(NO₃)₂] via hydrothermal deposition at 150°C. Test environments with a dissolved oxygen concentration of 300ppb and various dissolved hydrogen concentrations at 288°C were created. Test results showed that the ECPs of the treated specimens were lower than that of the untreated one no matter what the dissolved hydrogen concentration was. In addition, IGSCC was observed on all specimens (treated or untreated) in all tested environments. However, the untreated specimen exhibited lower elongation, shorter failure time, and more secondary cracks on the lateral surfaces. It was therefore suggested that inhibitive chemicals such as ZrO₂, TiO₂, and ZrO(NO₂)₂ did provide a certain degree of enhancement in improving the mechanical behavior of the treated specimens and in prolonging IGSCC initiation times.