热老化对核电主管道Z3CN20.09M不锈钢点蚀性能的影响

采用极化曲线和电化学交流阻抗法研究了400℃长期热老化对压水堆核电站一回路主管道用Z3CN20.09M铸造奥氏体不锈钢点蚀性能的影响.结果显示,材料的点蚀击破电位和电荷转移电阻随着热老化时间的延长而降低.热老化材料经550℃退火处理1 h后的点蚀击破电位和电荷转移电阻值均恢复到未老化材料的水平.研究表明此时α'相已经回溶,G相仍然存在,导致热老化试样点蚀性能下降的主要原因是α'相的析出.      

核电主管道用316LN不锈钢焊缝热老化脆化的趋势

开展了核电站主管道用316LN不锈钢焊缝在325、365和400℃下1.5万h的加速热老化试验,测量了不同热老化时间下焊缝的冲击性能和焊缝铁素体的纳米硬度。以纳米硬度作为热老化脆化参量,利用Arrhenius方程得出该焊缝热老化激活能约为93.1kJ/mol;并以焊缝室温冲击功为预测参数,通过拟合的方法获得了焊缝热老化脆化预测方程;利用热老化激活能和热老化脆化预测方程预测了主管道用316LN焊缝在服役温度下60年寿命期内的热老化脆化趋势。试验结果表明,随着热老化时间的增加,焊缝的冲击韧性显著下降,焊缝中铁素体纳米硬度快速增加。预测结果表明,在运行15年内主管道焊缝韧性迅速下降,在随后的运行过程中下降趋缓。     

核电主管道铸造不锈钢的热老化脆化

为了研究中国核电主管道铸造不锈钢Z3CN20-09M的热老化,在300、350和400℃下,对Z3CN20-09M进行了长达30000h的加速热老化实验.对不同热老化时间下的样品进行了冲击性能和铁素体纳米硬度测定.以夏比冲击功作为热老化脆化参量,利用拟合的方法得出该材料的热老化激活能为51.962kJ·mol-1.通过热老化因子P得出了用夏比冲击功表示的热老化脆化动力学公式.利用热老化激活能和热老化动力学公式预测了Z3CN20-09M在实际运行温度下服役40a内的夏比冲击功和铁素体显微硬度变化.预测结果表明在运行5a内是该材料韧性迅速下降的时期,随后的运行过程中下降过程趋缓.      

长期热老化对铝基碳化硼中子吸收材料性能的影响

采用粉末冶金工艺制备的铝基碳化硼中子吸收板,经过400℃、8 000 h长期加热处理后,观察了热老化处理后样品表面状态,测试了厚度、密度、力学性能、B4C质量分数、10B同位素含量、10B面密度及微观组织,并与热老化处理前进行了对比,热老化处理后样品表面没有出现裂纹、气孔、鼓泡等现象,抗拉强度、延伸率略有增加,其他各项性能指标与热老化处理前几乎无变化。     

AP1000主管道冷弯壁厚减薄

提出了一种改进的Johnson-Cook模型,用于室温和低应变速率下AP1000核电站主管道316LN奥氏体不锈钢的塑性变形过程研究.借助有限元软件ANSYS/LS-DYNA,对AP1000核电一回路主管道热段管冷弯成形过程进行模拟仿真,分析管道壁厚、相对弯曲半径、摩擦系数等工艺参数对壁厚减薄率的影响规律,拟合出壁厚减薄率的经验公式.全尺寸主管道冷弯试验结果表明,数值模拟结果准确可靠.      

双相不锈钢热老化前后拉伸变形行为的电子背散射衍射表征

通过电子背散射衍射实验分析方法,研究变形量和热老化因素对双相不锈钢的拉伸性能、相边界、局部应变分布、重位点阵特殊晶界和取向分布的影响.研究结果表明:热老化后,双相不锈钢的强度提高,韧性降低;在大变形条件下铁素体晶粒内小角度晶界的数量和密度略有增加;热老化材料的铁素体的塑性变形和局部应变能力下降,大变形破坏初始奥氏体和铁素体以及Σ3孪晶边界的分布.      

核岛用P280GH碳锰钢热老化的组织和性能

 P280GH碳锰钢用于制造压水堆核电站核岛蒸汽系统和辅助系统管道,其在280～350 ℃的长时服役过程中易于出现老化现象。为了研究其热老化机理,在400 ℃温度下进行了P280GH碳锰钢的10 000 h的加速热老化试验。测定了不同老化时间下铁素体和珠光体的显微硬度、试样拉伸性能和冲击性能。结果表明,铁素体和珠光体的显微硬度随老化时间的增长而逐渐减小;老化时间少于300 h时,拉伸强度和屈服强度随老化时间增长而增加,老化时间大于300 h后,抗拉强度逐步降低,屈服强度缓慢降低;冲击吸收功随老化时间的增加而减小。上述力学性能变化与热老化过程中的珠光体形貌变化及铁素体中的位错移动有关。     

永磁材料长期稳定性研究进展

永磁材料的长期稳定性对永磁应用器件的长期可靠使用是极为重要的。本文介绍了永磁材料长期稳定的理论模型的发展和在不同永磁材料中的应用,总结了温度、耐蚀性、镀层防护、永磁体的L/D因素等对烧结钐钴稀土永磁材料短期和长期稳定性的影响,讨论了烧结钕铁硼永磁材料的热稳定性、耐蚀性差的缺点,科技人员近年来所进行的研究和改善的途径,提出解决烧结钕铁硼永磁材料的长期稳定性应用应采取的途径。     

三元乙丙橡胶紫外老化表观行为及纳米防老化剂作用机制

基于荧光紫外加速老化实验,追踪三元乙丙橡胶的老化过程,研究添加纳米防老化剂对材料表观老化行为和抗老化能力的影响,并利用傅里叶红外光谱和紫外吸收光谱分析纳米防老化剂的作用机制.随着老化时间的延长,试样表面粗糙度增加,色差和失光率变大,羰基指数上升,紫外吸收率下降.傅里叶红外光谱分析显示,表面二氧化硅膜包覆抑制了纳米二氧化钛的光催化作用,延缓了三元乙丙橡胶的老化进程.添加纳米防老化剂后,试样表面孔洞密度减少,色差和失光率分别降低0.97和22.29%,羰基指数下降0.06,紫外光吸收率升高3.92%,三元乙丙橡胶的抗紫外老化能力提高.      

浅谈炉卷Cr25Ni20Si2钢的可焊接性及工艺性

针对炉卷长期在高温下运行所产生的严重热裂纹,从分析母材的可焊性及焊接材料方面入手,寻找出了适合解决炉卷热裂纹的焊接技术和焊接材料,达到了焊接省时、省力且消耗低的目的。     

Phase transitions in rapidly solidified stainless steels cathodically hydrogen charged

The effects of cathodic hydrogen charging and subsequent aging on phase transitions and microstructures of rapidly solidified (RS) austenitic stainless steels (types 310 RS, 316 RS, and 316TiM RS) were investigated. The behavior of the martensitic phases,α′(bcc) andε(hcp), as well as the austenite phase,γ (fcc), of the RS steels during aging after charging was compared to the behavior of these phases of equivalent conventionally processed commercial solution-treated (ST) austenitic stainless steels (types 310 ST, 316L ST, and 316TiM ST) following identical cathodic-charging conditions by means of X-ray and electron diffraction techniques. The behavior of theα′ phase of both RS and ST steels (that formα′ phase) during aging was found to be very similar, while the behavior of bothγ andε phases during aging of all of the RS steels studied, as compared to the equivalent ST steels, was different. The development of lower internal stresses and minor lattice expansion of the RS steels, as compared to the ST steels, is probably due to a different distribution of hydrogen within the near-surface layer of the RS steels than that of the ST steels, which appears to be related to the markedly different microstructural characterizations of the RS steels from the ST steels. Scanning and transmission electron microscopy (SEM and TEM) observations indicated that the tendency toward cracking along the columnar-like structure is typical of all of the charged RS steels studied. Formerly Research Associate, Department of Materials Engineering, Ben Gurion University of the Negev     

Phase transitions in rapidly solidified stainless steels cathodically hydrogen charged

The effects of cathodic hydrogen charging and subsequent aging on phase transitions and microstructures of rapidly solidified (RS) austenitic stainless steels (types 310 RS, 316 RS, and 316TiM RS) were investigated. The behavior of the martensitic phases,α′(bcc) andε(hcp), as well as the austenite phase,γ (fcc), of the RS steels during aging after charging was compared to the behavior of these phases of equivalent conventionally processed commercial solution-treated (ST) austenitic stainless steels (types 310 ST, 316L ST, and 316TiM ST) following identical cathodic-charging conditions by means of X-ray and electron diffraction techniques. The behavior of theα′ phase of both RS and ST steels (that formα′ phase) during aging was found to be very similar, while the behavior of bothγ andε phases during aging of all of the RS steels studied, as compared to the equivalent ST steels, was different. The development of lower internal stresses and minor lattice expansion of the RS steels, as compared to the ST steels, is probably due to a different distribution of hydrogen within the near-surface layer of the RS steels than that of the ST steels, which appears to be related to the markedly different microstructural characterizations of the RS steels from the ST steels. Scanning and transmission electron microscopy (SEM and TEM) observations indicated that the tendency toward cracking along the columnar-like structure is typical of all of the charged RS steels studied. Formerly Research Associate, Department of Materials Engineering, Ben Gurion University of the Negev     

奥氏体不锈钢中氮溶解度的热力学计算和实验研究

采用热力学分析方法,对固态不锈钢304、304L、301S和301L(γ-相)以及奥氏体不锈钢熔体中氮溶解度进行了计算,得出了氮溶解度的计算模型;同时通过1 kg MoSi电阻炉对4种奥氏体不锈钢在1520～1580℃和33～100 kPa压力下的渗氮行为进行了实验研究。结果表明,氮在固态奥氏体不锈钢的γ-相中的溶解度最高;在常压冷却、凝固过程中存在的液相、δ-相至γ-相的转变;当不锈钢熔体中相对于δ-相过饱和的氮在钢中以气泡形式析出,则降低了奥氏体钢的氮含量,所以采用常压快速冷却或加压浇注有利于冶炼高氮奥氏体不锈钢。     

硫酸介质中铸造奥氏体不锈钢的腐蚀磨损行为

研究了几种铸造奥氏体不锈钢在含有Ｃｌ－的硫酸介质中的点蚀规律,测定了腐蚀磨损率、摩擦因数和表面钝化膜破坏后的修复时间。实验结果表明,高铬、镍、铜不锈钢有较高的耐蚀性,但其腐蚀磨损失重却高于一般的１８－８型不锈钢     

钛含量对0Cr13Co8Ni5Mo马氏体时效不锈钢冲击韧性的影响

 通过具有不同Ti含量的三炉试验钢,研究了Ti含量对0Cr13Co9Ni5Mo 马氏体时效不锈钢的力学性能、金相组织和奥氏体含量的影响。研究结果表明：添加较多的Ti可显著降低基体组织中的有效C、N含量,大幅降低固溶、时效处理后残余/逆转变奥氏体含量,最终使冷脆转化温度显著上升,在提高强度的同时降低了钢的韧性。     

Constitutive Flow Equation for Cast Austenite–Ferrite Stainless Steels

Metallurgical and Materials Transactions A - Cast duplex (austenite–ferrite) stainless steels are important materials in many domains. Their mechanical properties are altered by thermal...     

Correlation between precipitation reactions and bulk density changes in type 18-12 austenitic stainless steels

Dimensional changes in austenitic stainless steels exposed to fast neutron fluxes have been attributed mainly to void formation and thermal and irradiation induced creep. In this in-vestigation, immersion bulk density measurements were performed on variously preheated AISI Types 304, 316L and 316 stainless steels. The results show that the density changes accompanying sequential precipitation of the various carbide (M₂₃C₈, M₆C) and intermetallic phases (sigma, chi, eta) during thermal aging can be comparable to those attributed to void formation at low fast neutron fluences. Vacuum melted Type 316 stainless steel always den-sified with aging at 725°C or 810°C and exhibited higher rates of precipitation and recovery of cold work during aging than the equivalent air melted steel. The direction of the density change in the air melted material was dependent upon the prior thermomechanical treat-ments. This behavior can be rationalized on the basis of a higher impurity content in the air melted material. A mathematical model was constructed which successfully explains the variation of bulk density due to sequential precipitation in Type 18-12 austenitic stain-less steels.