Development of a new irradiation-embrittlement prediction model for reactor pressure-vessel steels

Predicting the transition-temperature shift(TTS)induced by neutron irradiation in reactor pressure-vessel(RPV)steels is important for the evaluation and extension of nuclear power-plant lifetimes.Current prediction models may fail to properly describe the embrittlement trend curves of Chinese domestic RPV steels with relatively low Cu content.Based on the screened surveillance data of Chinese domestic and similar international RPV steels,we have developed a new fluencedependent model for predicting the irradiation-embrittlement trend.The fast neutron fluence(E>1 MeV)exhibited the highest correlation coefficient with the measured TTS data;thus,it is a crucial parameter in the prediction model.The chemical composition has little relevance to the TTS residual calculated by the fluence-dependent model.The results show that the newly developed model with a simple power-law functional form of the neutron fluence is suitable for predicting the irradiation-embrittlement trend of Chinese domestic RPVs,regardless of the effect of the chemical composition.

Load Bearing Capacity and Safety Analysis for Strain-hardening Austenitic Stainless Steel Pressure Vessels

By increasing the yield strengths of austenitic stainless steels for pressure vessels with strain hardening techniques,the elastic load bearing capacity of austenitic stainless steel pressure vessels can be significantly improved.Two kinds of strain hardening methods are often used for austenitic stainless steel pressure vessels：Avesta model for ambient temperature applications and Ardeform model for cryogenic temperature applications.Both methods are obtained from conventional design rules based on the linear elastic theory,and only consider the hardening effect from materials.Consequently this limits the applications of strain hardening techniques for austenitic stainless steel pressure vessels because of safety concerns.This paper investigates the effect of strain hardening on the load bearing capacity of austenitic stainless steel pressure vessels under large deformation,based on the elastic-plastic theory.Firstly,to understand the effect of strain hardening on material behavior,the plastic instability loads of a round tensile bar specimen are derived under two different loading paths and validated by experiments.Secondly,to investigate the effect of strain hardening on pressure vessels strength, the plastic instability pressure under strain hardening is derived and further validated by finite element simulations.Further,the safety margin of pressure vessels after strain hardening is analyzed by comparing the safety factor values calculated from bursting tests,finite element analyses,and standards.The researching results show that the load bearing capacity of pressure vessels at ambient temperature is independent of the loading history when the effects of both material strain hardening and structural deformation are considered.Finite element simulations and bursting tests results show that the minimum safety factor of austenitic stainless steel pressure vessels with 5% strain hardening is close to the recommended value for common pressure vessels specified in the European pressure vessel standard.The proposed study also shows that in the strain hardening design of austenitic stainless steel pressure vessels,the calculation for plastic instability pressure could use theoretical formula or finite element analyses based on geometrical dimensions and material property parameters before strain hardening,but a 5%strain should be employed as a design limit.The proposed research can be used for the strain hardening design of austenitic stainless steel pressure vessels safely.

Research on reasonable winding angle of ribbons of Flat Steel Ribbon Wound Pressure Vessel

Flat Steel Ribbon Wound Pressure Vessels (FSRWPVs) are used in many important industry areas. There is no such kind of pressure vessel exploding on operation for its reasonable structure design. Many explosion experiments on Flat Steel Ribbon Wound Pressure Vessel showed that their limited load pressure is related to the winding angle of the steel ribbons. FSRWPVs with reasonable winding angle have better security and lower cost. Reasonable angels given at the end of this paper facilitate engineering design.

Recent development in standards of steels used for pressure vessels in China

In this paper,five items of standards of steels used for pressure vessels which are issued recently or about to be issued and put into effect have been introduced.The differences of standards mentioned above and the former standards and the primary qualifications have been formulated.These qualifications indicate that,some qualifications of national standards of steels used for pressure vessels are on the international advanced level.

Microstructure and properties of S30403+Q345R roll-bonded clad steel plate for pressure vessels

To meet the demand of the domestic pressure vessel industry for roll-bonded clad steel plates, Baosteel has developed an S30403 ＋ Q345R roll-bonded clad steel plate. Comprehensive inspections of the composition, microstructure, and properties are made to systematically evaluate the steel plate in the normalized and normalized ＋ stress relieved states. The results show the cladding interface of the S30403 ＋ Q345R roll-bonded clad steel plate has high shear strength, the base metal has good properties, and the mechanical properties of the steel plate head and tail are uniform. The performance is fully consistent with the technical requirements of the roll-bonded clad steel plate for pressure vessels.

ESTIMATE OF BURSTING PRESSURE OF MILD STEEL PRESSURE VESSEL AND PRESENTATION OF BURSTING FORMULA

In order to get more precise bursting pressure formula of mild steel, hundreds of bursting experiments of mild steel pressure vessels such as Q235（Gr.D） and 20R（1020） are done. Based on statistical data of bursting pressure and modification of Faupel formula, a more precise modified formula is given out according to the experimental data. It is proved to be more accurate after examining other bursting pressure value presented in many references. This bursting formula is very accurate in these experiments using pressure vessels with different diameter and shell thickness. Obviously, this modified bursting formula can be used in mild steel pressure vessels with different diameter and thickness of shell.

Effect of Pre-Deformation Enhanced Thermal Aging on Precipitation and Microhardness of a Reactor Pressure Vessel Steel

Microstructure evolution in neutron irradiated Reactor Pressure Vessel （RPV） steels was experimentally simulated through an improved degradation procedure in this study. The degradation procedure includes austenitizing at 1 150℃ and water quench, deformation 10% and 30% respectively, and then thermal aging at 500℃ for different period of time. The microstructure of the specimens was analyzed in details using transmission electron microscopy （TEM）. The micro-hardness test results showed that all the hardness curves of undeformed, 10% pre-deformed and 30% pre-deformed specimens have two micro-hardness peaks with the first peak value corresponding to different thermal aging time of 1 hour, 5 hours and 10 hours, respectively. It was revealed that the hardness curves were influenced by the precipitation of Cu-rich precipitates （CRPs） and carbides, deposition of martensite and work hardening.

Development of S11306+SA516Gr70 roll-bonded clad steel plate for pressure vessels

To meet the demand of the pressure vessel industry, Baosteel has developed an S11306 ＋ SA516Gr70 roll-bonded clad steel plate. Comprehensive inspections of the composition, microstructure, and properties are performed to systematically evaluate the steel plate in normalized state and normalized ＋ stress relieved state. The results show the cladding interface of the Sl1306 ＋ SA516Gr70 roll-bonded clad steel plate has high shear strength, and the base metal has good mechanical properties. The performance is fully consistent with the technical requirements of the roll-bonded clad steel plate for pressure vessels.

INVESTIGATION OF INFLUENCE OF HYDROGEN ATTACK ONFATIGUE PROPERTIES OF PRESSURE VESSEL STEELS

Influence of hydrogen attack on mechanical and fatigue properties of 1020, 15CrMo and 2.25Cr-1Mo steels has been studied, which were exposed to gaseous hydrogen at pressure of 18MPa and 300-480℃ for up to 480h. The results of fatigue test showed that hydrogen attack (HA) resulted in an obvious change in fatigue properties of 1020 and 15CrMo steels, however, 2.25Cr-1Mo steel showed a lower susceptibility to hydrogen attack due to the addition of Cr and Mo. Fatigue crack behaviour for 1020 steel is attributed to hydrogen attack damage and the crack closure induced by the rough cracking surface, which lead to a valley on △Kth～HA% plot. The change in the fatigue behaviour of 15CrMo steel is possibly caused by severe surface decarburization.

Stress Corrosion Cracking of Pressure Vessel Steel and Countermeasures by Titanium-Based & Cerium-Based Inhibitors in Subcritical Aqueous Environment

An overview of a severe kind of environmentally-assisted cracking-stress corrosion cracking (SCC) of pressure vessel steel (PVS),such as stainless steel 304, alloy 600,690 and other nickel-based alloys in subcritical (～300 ℃) aqueous environment was given. The mechanisms of SCC of metals under this inclement surrounding were briefly generalized. Herein,some pragmatic solutions to mitigate the SCC susceptibility and retard its propagation were presented. The titanium and cerium-based inhibitors addition countermeasure was highlighted.

EMBRITTLEMENT OF A Cr-Mo LOW-ALLOY STEEL DUE TO LOW-TEMPERATURE NEUTRON IRRADIATION

Embrittlement of a Cr-Mo2.25CrlMo steel stemming from neutron irradiation at 270℃ is studied by virtue of small punch testing in conjunction with scanning electron microscopy. The ductile-brittle transition temperature determined by the small punch test is much lower than that determined by the standard Charpy test. There is some irradiation-induced embrittlement effect after the steel is irradiated for 46 days with a neutron dose rate of 1.05×10^18dpa/s （displacement per atom per second）.

三代核电反应堆压力容器低合金钢焊缝性能对比分析

通过模拟国内三代核电压水堆反应堆压力容器环焊缝,分别采用国产焊接材料和进口焊接材料,在焊接工艺性能、焊缝金属化学成分、拉伸、冲击韧性、落锤和低周疲劳试验等方面进行了对比分析。结果表明,国产和进口焊接材料的焊接工艺性能和焊缝金属力学性能均相当;焊接试件不同厚度取样位置的焊缝金属-28.3℃冲击吸收能量平均值都大于90 J,有较大的设计裕量。该国产焊接材料已应用于国内某三代核电机组反应堆压力容器,为进一步推广应用提供技术支撑。

大壁厚不锈钢复合板压力容器建造关键技术及应用

在大壁厚不锈钢复合板压力容器的建造过程中,通过深入研究其技术要点和难点,优化焊接接头结构设计,成功形成了一套完整的新型建造关键技术。这套技术不仅优化了焊接接头结构,还创新了一系列施工方法,包括筒体加热卷制、接头坡口机加工、接管内壁耐蚀层TIG/FCAW自动堆焊、不锈钢衬管液氮冷套、球形封头内壁耐蚀层带极埋弧堆焊、纵环缝窄间隙埋弧自动焊以及管口接头马鞍型埋弧焊等。这些新型建造关键技术的应用,在提高压力容器质量效果的同时,也带来了显著的经济效益,为行业同类型设备的建造提供借鉴。在未来的研究中,可以进一步探索这些技术在其他领域的应用,以实现更广泛的技术交流和合作。同时,对于大壁厚不锈钢复合板压力容器的建造,仍需不断深入研究其材料特性、工艺参数和施工方法,以不断提高设备的性能和安全性。

抗压容器钢在模拟工业码头大气环境下的腐蚀行为研究

为探究抗压容器钢在模拟工业码头大气环境下的腐蚀行为,利用失重分析、EDS、XRD和电化学方法研究了不同模拟加速试验周期下抗压容器钢Q235和16MnNiVR钢的腐蚀行为。结果表明:抗压容器钢Q235和16MnNiVR钢在模拟工业海洋大气环境试验中,其腐蚀速率先呈现上升趋势,随着锈层由疏松逐渐变致密,腐蚀速率会发生不同程度地下降。在此加速试验下2种钢的腐蚀产物化学性质一致,所发生的腐蚀行为差异是由金属基材表面腐蚀产物致密性所致,在东南沿海工业海洋大气环境腐蚀因子作用下,16MnNiVR钢的耐蚀性可达到Q235钢的1.6倍。

高压储氢容器用高强度可焊接钢板Q690DR的研发

以ASME SA517 Gr.F为对标材料,设计高压储氢压力容器用可焊接高强度钢板Q690DR。通过优化化学成分、热处理工艺精准调控,可获得屈服强度不小于690 MPa,抗拉强度800~900 MPa,冲击性能良好的高强度可焊接Q690DR钢板。经系列抗氢性能评价试验,Q690DR具有良好的抗氢脆性能,较低的氢脆敏感性。对比10 MPa氢气与同压力的氮气环境下的慢拉伸试验结果,Q690DR的相对延伸率约为96.4%,相对断面收缩率约为97.0%,具有较低的氢脆敏感性。10 MPa氢气环境下Q690DR测得的断裂韧度K_(IH)约为305 MPa·m^(0.5)。整体看,工业试制的Q690DR钢板各项指标性能优良稳定,符合相关标准及用户技术条件,可以用于实际工程项目高压储氢容器的建造。

12Cr5Mo压力容器制造监督检验及工艺优化

以某单位首次试制造12Cr5Mo耐热钢制压力容器为例,介绍了耐热钢制压力容器制造监督检验过程中的质量控制,重点描述了12Cr5Mo的材料入库检验控制、焊接相关过程的控制、热处理的工艺控制过程。通过分析压力容器本体上不同受压元件之间的焊接结构形式以及12Cr5Mo的材料性能,根据提供的焊接工艺评定、焊工资格项目、热处理工艺,发现相关部分焊评焊工资质不覆盖问题。通过优化热处理工艺和选择合适焊评焊工,最终顺利通过了无损检测及耐压试验。

核压力容器用SA508Gr.3钢的研究进展

核反应堆压力容器是核电站重要组件且具有在全寿命周期内不可更换的特殊性。第二代核压力容器用钢在其焊缝中发现了再热裂纹,已不能够满足使用需求。因此,在此基础上通过添加Mn元素,减少Mo和Cr元素改进设计了SA508Gr.3钢,它具有高强度、高韧性和低辐照脆化敏感性等特点,目前广泛应用于核电压力容器、蒸发器和稳压器等核心构件。本文总结了SA508Gr.3钢的研究进展,重点介绍了合金元素、热处理工艺对其显微组织和力学性能的影响,并详细介绍了SA508Gr.3钢的抗辐照性能。根据核压力容器的服役环境,详细分析了热时效对SA508Gr.3钢显微组织及力学性能的影响机理。随后,总结了显微组织演化对其疲劳性能、疲劳裂纹萌生及疲劳裂纹扩展的影响机制。最后,展望了核压力容器的发展方向和需要进一步研究的内容,为提高SA508Gr.3钢的综合性能和研发下一代核电用钢提供参考。

焊后热处理对核反应堆压力容器用16MND5钢组织和性能的影响

采用光学显微镜、透射电子显微镜,通过拉伸、冲击和落锤试验等方法研究了焊后热处理温度和保温时间对16MND5钢的组织和力学性能的影响。结果表明:经模拟焊后热处理后16MND5钢的室温和350℃抗拉强度和屈服强度都呈下降趋势,且下降幅度随焊后热处理温度的升高和保温时间的延长而增大;焊后热处理时间的延长导致钢的冲击性能小幅度下降,焊后热处理温度对冲击性能的影响并不明显;焊后热处理后的钢基体中弥散分布的细小第二相粒子数量减少、尺寸增大,导致钢的强度降低。

中厚板Q345R延伸率不合格原因分析及改进

锅炉和压力容器用钢板是锅炉等压力容器加工制造中的关键材料,需具有良好的物理性能、力学性能和可加工性,以保证其使用中的安全性。重点针对中厚板生产线容器板Q345R延伸率不合格问题展开研究,分析问题产生原因,并制定相应措施,以提升材料的延伸塑性。

基于机器视觉的钢制压力容器焊缝缺陷X射线检测方法

为降低由钢制压力容器焊缝缺陷引起的事故发生概率,提出基于机器视觉的钢制压力容器焊缝缺陷X射线检测方法。使用机器视觉系统以及X射线技术,获取钢制压力容器焊缝图像并提取焊缝区域特征,将焊缝缺陷整合成熔焊、虚焊、焊穿三大类别;基于焊缝区域特征的提取结果,提取钢制压力容器的焊缝缺陷面积、缺陷亮度以及波形等缺陷特征,构建缺陷分类器,实现钢制压力容器焊缝缺陷X射线检测。实验结果表明:钢制压力容器焊缝缺陷检测时,随着待检测焊缝图像的增加,F1值较高,实际缺陷检测结果的主观判断效果明显,细节检测效果好。