【作者】 徐丹；

【导师】 邸新杰；

【作者基本信息】 天津大学 ， 材料工程， 2012， 硕士

【摘要】 随着全球用电消耗量的持续增长,为解决日益突出的能源短缺和环境污染问题,世界各国火力发电机组参数正由亚临界参数向超(超)临界参数的方向发展。9%~12%Cr系铁素体耐热钢因具有良好的强韧性、抗氧化性、耐腐蚀性和较高的蠕变强度已逐渐成为热电厂中主要设备用材和更新换代材料的主选用钢。本文利用焊接热模拟和定量金相结合的方法对改进的新型高Cr铁素体耐热钢的连续冷却转变曲线(SHCCT图)进行了测定,并研究试验用钢在不同冷却速度下的组织构成、组织形态和沉淀物形貌。利用正交试验方法考察热输入和预热温度对试验用钢热影响区(包括粗晶区-CGHAZ、细晶区-FGHAZ、临界区-ICHAZ和二次热循环的过临界粗晶区-SRCGHAZ、临界粗晶区-IRCGHAZ)组织和性能的影响规律。试验结果表明,试验用高Cr铁素体耐热钢CGHAZ的组织为板条马氏体加δ铁素体,不同冷速下组织中马氏体与δ铁素体界面之间均存在脆化的碳化物薄层,而且随着冷速的增加,碳化物薄层的厚度逐渐下降。不同工艺下CGHAZ的室温冲击功均较低,而ICHAZ的室温冲击功均较高。组织中过饱和的马氏体和存在脆性相δ铁素体是造成CGHAZ室温韧性很低的主要原因,δ铁素体的含量越高,韧性越差。ICHAZ马氏体板条上细小的分布均匀的沉淀物能够有效地稳定马氏体基体,提高其韧性。CGHAZ的硬度最高,ICHAZ的硬度最低,IRCGHAZ与CGHAZ相比,硬度下降较多。更多还原

【Abstract】 As global electric power consumption increases fast in recent years, in order to solve the increasingly prominent problem of inadequate energy and environmental pollution, thermal power generating units around the world are transforming from sub-critical parameters to the super (super-) critical parameters. 9~12% ferritic heat-resistant steel has gradually become the primary election material used for main power plant equipment and timber replacement materials for its excellent strength and toughness, oxidation resistance, corrosion resistance, and high creep strength.In this paper, the SHCCT curve of new high Cr ferritic heat-resistant steel was made by thermal simulation and quantitative metallographic method, and studied the organization structure and morphology of precipitation at different cooling rates for testing steel. Orthogonal test was used to investigate the influences of heat input and preheat temperature on the microstructure and mechanical properties of heat affected zone (HAZ) of testing steel. Moreover, the HAZ includes coarse grain heat affected zone (CGHAZ), fine grain heat affected zone (FGHAZ), critical heat affected zone (ICHAZ), super-critically reheated coarse-grained HAZ (SRCGHAZ) and inter-critically reheated coarse-grained HAZ (IRCGHAZ).Test results showed that testing steel CGHAZ was constructed of lath martensite and delta ferrite. The brittle dioxide layer could also be observed in the interface between lath martensite and delta ferrite under different cooling rates, and the thickness of carbon layer decreased with the cooling rate increasing. The CGHAZ impact energy at room temperature was low under the different welding process, but the ICHAZ had high impact energy at room temperature. Saturated martensite and brittleδferrite existed in the CGHAZ microstructure was the main reason for its low impact energy at room temperature, andδferrite content was higher, the worse the toughness. For ICHAZ, some fine precipitation which distributed uniformly in the martensite lath was able to stabilize the martensitic matrix, and the ICHAZ toughness was improved attributed to these fine precipitation. CGHAZ showed the highest hardness, and the ICHAZ hardness was the minimum, compared with CGHAZ, the IRCGHAZ hardness decreased a lot.更多还原