中国低活化马氏体钢CLAM研究进展

低活化铁素体/马氏体钢(RAFM钢)被普遍认为是未来聚变示范堆和聚变动力堆的首选结构材料。国际上给予了高度重视,许多国家都在研发其特有的RAFM钢。中科院等离子体物理研究所在与国内外多家单位的合作下发展了中国低活化马氏体钢———CLAM。本文总结了CLAM钢研制发展的主要进展,包括其成分优化设计、冶炼加工制备工艺、物理性能、机械性能、辐照性能及与液态LiPb的相容性等测试与研究以及各种焊接工艺研究等,并对今后的发展方向进行了展望。     

中国低活化马氏体钢CLAM在液态锂铅中腐蚀的初步实验研究

液态金属锂铅包层是最具发展潜力的聚变堆包层之一,其首选结构材料为低活化铁素体/马氏体钢,而它与液态锂铅的相容性是聚变堆材料研究领域的关键问题之一.本文介绍中国低活化马氏体钢CLAM在液态金属锂铅回路DRAGON-1热对流工况下的实验情况及500 h 480 ℃下初步腐蚀实验结果,并与同样工况下316L奥氏体钢腐蚀结果进行了对比分析.结果显示CLAM钢与液态锂铅的相容性优于316L钢.     

中国液态锂铅包层材料研究进展

液态锂铅包层是国际上普遍关注和最有发展潜力的聚变堆包层概念设计之一,而包层材料是液态锂铅包层的核心问题之一.目前,液态锂铅包层普遍选用低活化铁素体/马氏体钢(RAFM钢)作为结构材料,液态锂铅作为中子倍增剂及氚增殖剂.另外,部分设计采用了耐高温、电绝缘流道插件作为功能材料,以降低磁流体动力学效应及提高冷却剂出口温度(高于700℃).为适应液态包层的发展需求,中国科学院等离子体物理研究所FDS团队联合国内外相关研究单位,进行了具有中国自主知识产权的中国低活化马氏体钢(CLAM钢)及液态锂铅包层功能材料研发,并开展了锂铅热对流及强迫对流回路的设计、研制及腐蚀实验研究,以研究液态金属锂铅的流动特性及其与结构和功能材料的相容性.同时建立了聚变堆材料数据库平台,为促进中国聚变堆液态包层及材料技术的研究和发展提供数据支持.     

69 马氏体不锈钢辐照效应研究

低活化马氏体钢具有良好的抗辐照肿胀热物理性能，所以最有希望成为实验聚变堆第1壁和包层结构材料，也是正在进行研究设计的聚变堆次临界系统（Fusion Driven Sub—critical System，FDS）的首选结构材料之一。     

聚变驱动次临界堆双冷嬗变包层结构设计与分析

给出聚变驱动次临界堆液态金属LiPb/He气双冷嬗变包层参考结构概念,采用了低活化铁素体/马氏体RAFM钢(如CLAM)作为结构材料、简单液态金属流道、两个独立氦气冷却系统以及燃料球/颗粒等设计方案。重点分析了嬗变包层第一壁、重金属区与裂变产物嬗变区的结构设计特点。     

先进快堆外套管材料铁素体/马氏体钢研究进展

介绍了快堆外套管材料的使用要求以及国内外快堆外套管材料的选用情况,论述了快堆中中子辐照对铁素体/马氏体钢的微观结构和力学性能的影响,并介绍了国产快堆外套管材料铁索体/马氏体钢的研发计划.铁索体/马氏体钢具有优异的抗辐照肿胀性能,T92钢作为第三代铁索体/马氏体钢同时具有良好的高温强度,被作为国产快堆外套管的首要候选材料...     

聚变制氢堆高温液态包层热工水力学新概念研究

在深入分析聚变堆包层设计要求和目前技术发展水平的基础上,根据热化学工艺制氢需要高温热的要求,提出了一个基于技术相对成熟的低活化铁素体/马氏体钢作为主要结构材料、高压氦气与液态LiPb合金作为冷却剂、具有创新性“多层流道插件”结构方案以获得高温热能的包层热工水力学概念,建立了热工水力学模型,在利用有限元数值模拟程序进行模拟计算的基础上分析了这种新概念包层的可行性。     

低活化铁素体/马氏体钢CLF-1氢氘的渗透行为

低活化铁素体/马氏体钢（RAFM钢）作为聚变堆结构材料中最有前景的候选材料,其氢同位素渗透行为备受关注。采用氢同位素气相驱动渗透的方法,对中国低活化铁素体/马氏体钢CLF-1的氢同位素渗透行为进行了研究,研究了温度、气体压强、样品表面状态等因素对其渗透行为的影响。结果表明：氢、氘在RAFM CLF-1钢中渗透扩散过程为体扩散控制,渗透率与温度的关系式均遵循Arrhenius关系;在实验测试过程中,由于样品表面发生氧化现象和缺陷捕获造成H₂和D₂渗透实验中渗透通量出现下降的现象。     

用于制造KOHCSBTBM低活化铁素体／马氏体不锈钢的焊接技术的开发

韩国氦冷固体氚增殖堆试验包层模块的概念设计已经完成，还研究了试验包层模块概念的制造可行性。因此，很有必要研究开发其制造技术，如结构材料的连接技术，这是因为低活化铁素体／马氏体钢被公认为是韩国氦冷固体氚增殖堆试验包层模块的结构材料。几种类型的低活化铁索体／马氏体钢已得到推荐，但是它们的焊接性仍然在研究之中。本文详细地调查研究了低活化铁素体／马氏体钢的电子柬焊接技术，包括焊接样品在焊后热处理之前和焊后热处理之后的拉伸、硬度、冲击及微观结构等性能。结果显示焊接质量和本文应用的工艺是合理的。     

钇对9Cr-2WVTa低活化马氏体钢力学性能的影响

研究了稀土合金元素钇对聚变堆用低活化马氏体钢9Cr-2WVTa力学性能的影响,分析了钇在低活化马氏体钢中的冶金行为.研究结果表明,钇元素容易在钢中聚集形成富钇的块状夹杂,割裂了基体的连续性,容易破裂形成微孔;轧板中这些富钇块夹杂沿着轧制方向成条线状分布,使得在拉伸和冲击断裂时出现断口分层现象,降低了钢的力学性能.     

430℃下2.98dpa中子辐照后CLAM钢的拉伸和冲击性能

利用高通量工程试验堆HFETR开展了CLAM钢430℃下2.98dpa的中子辐照实验,通过辐照前后拉伸和冲击性能测试与对比分析,研究了CLAM钢的中子辐照硬化和脆化效应。结果显示,CLAM钢辐照后室温测试的抗拉强度和屈服强度分别为710 MPa和615 MPa,较辐照前分别下降16 MPa和-0.5MPa,总延伸率减小1%,断面收缩率下降4%,保持良好的强度、塑性和韧性。冲击测试表明,CLAM钢辐照前后韧脆转变温度基本相同,上平台能量无明显变化,约为217J,未出现明显辐照脆化。CLAM钢的抗辐照性能略优于其他低活化铁素体/马氏体RAFM钢在类似辐照条件下的性能。     

Assessment of thermo-mechanical behavior in CLAM steel first wall structures

The temperature and strain distributions of the mockup with distinct structural material (SS316L or China Low Activation Martensitic steel (CLAM)) in two-dimensional model were calculated and analyzed, based on a high heat flux (HHF) test recently reported with heat flux of 3.2 MW/m². The calculated temperature and strain results in the first wall (FW), in which SS316L is as the structural material, showed good agreement with HHF test. By substituting CLAM steel for SS316L the contrast analysis indicates that the thermo-mechanical property for CLAM steel is better than that of SS316 at the same condition. Furthermore, the thermo-mechanical behavior of the FW was analyzed under the condition of normal ITER operation combined effect of plasma heat flux and neutron heating.     

Effect of direct and reheated quenching on microstructure and mechanical properties of CLAM steels

Direct and reheated quenching on microstructural mechanical properties of China Low Activation Martensitic (CLAM) steel was investigated. Three direct quenching and tempering (DQ&T) CLAM steels were rolled at the same finish rolling temperature with different quenching rate, and their microstructures and mechanical properties were compared with those of a reheated quenching and tempering (RQ&T) CLAM steel. DQ&T process was proven to strengthen the tensile property but lower the toughness compared to RQ&T process due to the finer austenite grain size formed under RQ&T process. Tensile property first increased with quenching rate and then decreased. The reason for this was discussed.     

Low cycle fatigue properties of CLAM steel at room temperature

The low cycle fatigue (LCF) properties and the fracture behavior of China Low Activation Martensitic (CLAM) steel have been studied over a range of total strain amplitudes from 0.2 to 2.0%. The specimens were cycled using tension-compression loading under total strain amplitude control. The CLAM steel displayed initial hardening followed by continuous softening to failure at room temperature in air. The relationship between strain and fatigue life was predicted using the parameters obtained from fatigue test. The factors effecting on low cycle fatigue of CLAM steel consisted of initial state of matrix dislocation arrangement, magnitude of cyclic stress, magnitude of total strain amplitude and microstructure. The potential mechanisms controlling the stress response, cyclic strain resistance and low cycle fatigue life have been evaluated.     

Corrosion behavior of CLAM steel weldment in flowing liquid Pb-17Li at 480 °C

CLAM (China Low Activation Martensitic) steel is considered as one of the candidate structural materials in liquid LiPb blanket concepts. Welding is one of the essential technologies for its practical application, CLAM steel weldment shows a great difference with base metal due to the effect of welding thermal cycle. In order to investigate the corrosion behavior and mechanism of CLAM weldments in liquid Pb-17Li, the experiments were performed by exposing the TIG weldment samples in flowing LiPb at 480 °C. The weight loss test of exposed specimens show that in 500 h, 1000 h dynamic conditions, corrosion resistance of CLAM steel weldment is poor, SEM analysis shows that the thicker martensite lath in weld area lead to higher corrosion amount, EDS results show that the influence of corrosion on surface elements is small, and surface corrosion is even, EDX analysis shows that the penetration of Pb-17Li does not exist in the joint. With the increasing of exposure time, the corrosion rate decreases. Metallographic analysis shows that the presence of Cr has great influence on the corrosion resistance of the steel matrix. The area short of Cr in thick martensite lath of CLAM steel weldment is easily corroded. After a series of theoretical and experimental analysis, a basic presumably corrosion behavior model is established, which makes contributions to the in-depth understanding of the corrosion mechanism of CLAM weldments.     

中国抗中子辐照钢的抗辐照设计与验证

聚变堆等未来先进核能系统要求材料在强流高能中子辐照下长期保持良好的结构稳定性和机械性能。为适应未来先进核能技术发展的需要，中国科学院核能安全技术研究所•凤麟团队牵头研发了具有我国自主知识产权的中国抗中子辐照钢--CLAM钢。CLAM钢的设计考虑了未来核能清洁性的要求，以及苛刻服役环境中材料抗辐照、耐高温、耐腐蚀等性能要求。通过中子学计算分析设计了低活化成分范围，基于选择性纳米相析出进行了抗辐照、耐高温性能优化设计。针对材料的抗辐照性能，利用国内外中子、离子、电子及等离子体辐照设施开展了系列辐照考验研究，通过多角度表征辐照前后材料的微观结构和宏观性能，综合评估了材料的辐照性能，并与国际上同类材料在相近或相同条件下的辐照性能进行了对比分析，结果表明CLAM钢具有良好的抗辐照性能。     

Preliminary experiments on the corrosion of CLAM steel in flowing eutectic LiPb

China low activation martensitic steel (CLAM), which is one of the RAFMs and under development in ASIPP, is considered as the primary candidate structural material for blankets in FDS series fusion reactors and will be in contact with the liquid breeder LiPb, so its corrosion behavior is of significance for its successful application. In the thermal convection LiPb loop DRAGON-I, the corrosion experiment of CLAM in flowing LiPb at 480 °C was performed up to about 2500 h to evaluate the corrosion behavior of CLAM in LiPb. The exposed samples were observed and analyzed, respectively, by metallography and scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy after 500, 1000, 1500, 2000 and 2500 h corrosion experiments, respectively. The results show that the corrosive attack started with the dissolution of the passivated oxides formed during the heat treatment on the surface of CLAM steel. Then the corrosive attack continued further into the steel matrix. The weight loss was about 0.38 mg/cm² after 2500 h exposure.     

Measurement and analysis of SHCCT diagram for CLAM steel

China Low Activation Martensitic (CLAM) steel is a leading candidate material for construction of the Chinese fusion reactor Test Blanket Module. The Simulated HAZ Continuous Cooling Transformation (SHCCT) diagram is developed via physical simulation, and the effects of thermal history on the microstructure and mechanical properties of the weld coarse-grain heat-affected zone (CGHAZ) in CLAM steel are evaluated. The results of thermal cycle simulation show that grain size increases and hardness decreases gradually with increasing heat input. Under certain conditions, especially when cooling times from 800 °C to 500 °C (T8/5) are larger than 136 s, delta ferrite may form which is deleterious for the TBM application. The amounts of delta ferrite are given under different T8/5. A SHCCT diagram of CLAM steel is developed using dilatometry and it predicts the AC1, AC3 and the Ms temperatures. With decreased cooling rate (larger T8/5), martensite laths widen and carbide precipitates grow. The results indicate that welding heat input should be taken into consideration and controlled in practical CLAM steel welding process applications.     

Microstructure and its influence on mechanical properties of CLAM steel

The microstructure of China Low Activation Martensitic steel (CLAM) and its influence on mechanical properties were investigated. The tensile test showed that the strength of CLAM (HEAT 0603A) was higher than that of HEAT 0408B at room temperature, and the reverse results were obtained at elevated temperatures. The results indicated that the microstructure was composed of dispersived carbide particles and lath martensite with high dislocation density. The main precipitation phases were Cr-rich M₂₃C₆ carbides precipitated mainly along the lath boundaries and prior-austenite grain boundaries and Ta-rich MX particles precipitated mainly in the laths and lath boundaries. The finer lath was the main reason for the higher strength of HEAT 0603A compared with HEAT 0408B at room temperature; contrasted with the lower strength at high temperature. Heavier hot forging deformation degree was considered as the main possible reason for the decrease of martensite lath width in HEAT 0603A.