超超临界转子锻件热锻缺陷演变机制及控制基础

The 9%－12%Cr heat resistant steel for ultra supercritical rotor is hard deoformation materials.The controlling of crack and coarse grain in hot forging is the key to mastering the manufacturing technology. Taking the 9%-12% steel as the research subject, the internal mechanism during the as-cast microstructure of ESR ingot transforming into the forged microstructure completely and the relationship between the microstructure, performance and deformation conditions are studied by integrating physical simulation and numerical simulation and technology tests. The characterization parameter and critical criterion of forging penetration are obtained. The mechanisms of crack initiation and propagation are studied in hot forging process. Considering the effect of thermodynamic condition, microstructure of material and size effect of forging, the models of crack initiation and fracture with high precision are established.The quantitative relationships between grain nonuniform degree in the inner of forgings and deformation temperature and loading way and forging ratio and nonuniform deformation degree and so on in forging process are studied to ascertain the formation mechanism of coarse grain. The technology tolerance to control the coarse grain is obtained. The precipitation and dissolution mechanisms and the evolution laws of δ ferrite, M23C6, MX, Laves phase and Z phase in heat treatment process and their effects on the performance of the rotor during service period are studied. The key data of heat treatment process for improving the performance of heat resistant steel during service period are determined. The breakthrough in the formation mechanism and process controlling of hot forging defects of heat resistant steel is achieved by project study. It has important scientific significance and application value for the independent production of China's ultra supercritical rotor heavy forgings.

超超临界转子用9%－12%Cr耐热钢为难变形材料，其热锻裂纹、粗晶等缺陷控制是掌握制造技术的关键。本项目以9%－12%Cr钢为研究对象，采用物理模拟、数值模拟及工艺试验集成方法，研究ESR钢锭铸态组织转变为锻态组织内在机制及变形条件与组织性能的影响关系，获得锻透表征参数和临界判据；研究热锻裂纹萌生扩展机理，综合考虑热力条件、材料微观组织和锻件尺寸效应的影响，并建立较高精度的裂纹萌生及断裂模型；研究成形锻造过程变形温度、加载方式、锻比及变形不均匀程度对锻件内部晶粒非均匀程度的影响，探明粗晶形成机理并获得粗晶控制工艺容限。研究热处理过程δ铁素体、M23C6、MX、Laves相、Z相的演变规律及其对转子服役期性能的影响，确定提高耐热钢服役期性能的热处理工艺关键数据。项目研究在耐热钢热锻缺陷形成机理及工艺控制方面取得突破，对于我国超超临界转子大锻件的自主制造具有重要的科学意义和应用价值。

超超临界转子用9%－12%Cr耐热钢为难变形材料，其热锻裂纹、粗晶和混晶等缺陷控制是其制造技术自主化的关键。本项目采用物理模拟、数值模拟及工艺试验集成方法，研究ESR钢锭铸态组织转变为锻态组织内在机制及变形条件与组织性能的影响关系，获得了针对轴类锻件成形过程锻透表征参数，并建立判定锻透临界值的数学模型；基于对耐热钢高温拉伸行为与断裂行为的研究，分析了热锻裂纹萌生和扩展机理，综合考虑热力条件、材料微观组织和锻件尺寸效应的影响，建立了较高精度的裂纹萌生及断裂模型，损伤进程模型和损伤演化模型；从锻造和热处理全方位视角研究耐热钢热加工过程中的晶粒不均匀演化行为，提出了混晶评价新方法，厘清了粗晶和混晶形成机理，揭示了锻造-热处理工艺界面上的混晶度演变及作用，确定锻造晶粒不均匀的工艺容限，并探索和提出面向转子终锻工艺的反向控制锻造工艺分析与设计方法；通过测定耐热钢的CCT曲线，研究热处理过程δ铁素体析出与消除规律，无锻比加热时第二相颗粒的演变规律，确定了提高耐热钢服役期性能热处理工艺的关键数据。项目研究在耐热钢热锻缺陷形成机理及工艺控制方面取得突破，对于我国超超临界转子大锻件的自主制造具有重要的科学意义和应用价值。