低活化铁素体钢高温构件均质连接及可靠性评价

The large-scale nuclear construction project makes urgent requirements for the localization of key components of nuclear power equipment, which has been limited by complicated structures of high-temperature components, long-term cycles in developing and assessing high-temperature structural materials, and especially high control levels in quality and manufacture technology. It is necessary to develop homogeneous manufacturing techniques for complex reactor components. This project is focused on the complicated cladding structure used in the nuclear reactor, and the ways to achieve consistent high-temperature performance across the entire structure will be explored on the basis of the compositional optimization of reduced activation ferritic steels, process optimization of vacuum diffusion bonding, and the strengthening of the interface between diffusion bonded steels. Moreover, extra attentions will be paid to clarify the effects of applied stress on the microstructure and mechanical performance of the diffusion bonded joint of reduced activation ferritic steel, to the mechanisms for creep strength degradation of the joint as well as its strengthening methods. The project mainly involves: 1) Designing compositions of the reduced activation ferritic steel based on the high Cr ferritic steels previously developed, according to the selecting principles for reduced-activation elements; 2) Combining the experimentally-determined kinetic information with the analytical phase transformation models to clarify the phase transformation behaviors and strengthening mechanisms of the reduced activation ferritic steel; 3) Producing complex nuclear components by vacuum diffusion bonding techniques; Improving the creep rupture strength of the bonded joints by using effective interlayers, and by ensuring the homogenization between parent materials and interface in microstructure and mechanical performances; 4) Proposing appropriate criteria for elevating the reliability of the diffusion bonded joints of reduced activation ferritic steel, in order to ensure the safe and reliable service of the nuclear reactor at high temperature.

大规模核电建设对关键核电部件的国产化提出了紧迫要求。核电高温部件结构复杂、材料开发与验证周期长、制造和质量水平要求高，迫切需要发展复杂高温部件的均质制造技术。本项目以核电机组复杂包层结构为研究对象，通过全面考虑低活化铁素体耐热钢成分优化、真空扩散连接工艺优化及连接接头界面强化方法来实现构件整体高温性能一致的目标，将重点阐明扩散连接过程外加应力对低活化钢组织和性能的影响以及连接接头蠕变强度退化机制，并提出相应的强化方法。拟在前期高Cr铁素体耐热钢研发的基础上，根据非活化元素选取原则来完成钢材的成分设计；综合采用实验研究与相变解析模型分析来阐明其相变行为与强化机制；通过真空扩散连接技术实现复杂构件的制造，并通过中间连接片层的有效引入来提高接头的高温强度，实现母材和连接界面高温性能的均质化；发展低活化铁素体钢连接接头的可靠性评价方法，从而确保核电机组在高温服役条件下安全可靠地运行。

大规模核电建设对关键核电部件的国产化提出了紧迫要求。核电高温部件结构复杂、材料开发与验证周期长、制造和质量水平要求高，迫切需要发展基于高温性能一致的复杂部件的均质制造技术。本项目研发了新型低活化、高持久强度的核电机组包层用铁素体耐热钢，澄清了其固相转变行为、强化机制与组织演变规律，考察了高Cr大规模核电建设对关键核电部件的国产化提出了紧迫要求。核电高温部件结构复杂、材料开发与验证周期长、制造和质量水平要求高，迫切需要发展基于高温性能一致的复杂部件的均质制造技术。本项目研发了新型低活化、高持久强度的核电机组包层用铁素体耐热钢，澄清了其固相转变行为、强化机制与组织演变规律，考察了铁素体耐热钢微小弹性变形对马氏体相变过程的影响机制，发现外加弹性变形对马氏体相变无显著影响，增大外加应力将抑制相变的进行，从而使马氏体板条细化；低活化铁素体钢中加入Ta后可导致M23C6型沉淀相析出量减少，纳米MX型沉淀相析出量增多，强化MX对晶界和板条界的钉扎作用并提高铁素体耐热钢的蠕变性能，高温服役时维持钢材组织中的马氏体板条形态并有效避免性能退化。针对传统铁素体钢焊缝及周围热影响区性能劣化的不足，开发了扩散连接构件制造真空扩散连接技术并完成了构件制造，其接头蠕变性能优于传统熔焊接头（甚至略高于母材），实现了母材和连接界面高温性能的均质化。在核电、石化用热轧无缝钢管成形与加工过程精细组织控制方面，发明了微变形马氏体板条细化、针状铁素体控制、高合金低碳含氮钢冶炼技术，形成系列产品已用于16个CPR1000机组建设，已累计实现销售收入3.18亿元，并获天津市技术发明二等奖和科技进步二等奖各1项；培养博士后2人、博士5人、硕士9人；研究团队入选天津市131科技创新团队；获中国金属学会冶金青年科技奖、J Mater Sci Technol优秀论文奖；完成邀请报告12次；授权中国发明专利6件，以第一/通讯作者发表标注资助SCI收录论文20篇。