Si含量对9%Cr铁素体马氏体钢微观结构和力学性能的影响

铁素体马氏体（F/M）钢是铅冷快堆堆芯的主要候选材料之一，提高Si含量可提高其抗腐蚀性能，但影响其微观结构和力学性能。为研发兼顾力学性能和抗腐蚀性能的高Si含量F/M钢，本文对Si含量（质量分数为034%、061%、080%、098%和120%）对9%Cr F/M钢微观结构和力学性能的影响进行了研究。结果显示，室温下通过正火（1 050 ℃，05 h，空冷）+回火（760 ℃，15 h，空冷）热处理制备的F/M钢均为全马氏体组织。钢的屈服强度和抗拉强度均随Si含量的增加而增加。Si含量对钢的组织及冲击性能的影响可分为两个阶段，当F/M钢中Si含量为034%~080%时，其组织、冲击性能变化很小；Si含量为098%~120%时，F/M钢中的第二相尺寸、数量增加，沿马氏体板条界面析出少量的Laves相，F/M钢的冲击韧性降低。本研究9%Cr F/M钢中Si元素的最优添加量应低于08%，使钢在保持较高强度的同时兼具良好的韧性。

Effect of Si Content on Microstructure and Mechanical Property of 9%Cr Ferrite Martensitic Steel

The 9%-12%Cr ferritic Martensitic (F/M) steel has the advantages of excellent creep performance at high temperature, remarkable irradiation resistance, high thermal conductivity, small thermal expansion coefficient, good economy and mature engineering application. The 9% 12%Cr F/M steel is one of the main candidate materials for lead cooled fast reactor core. The corrosion resistances of liquid Pb and Bi were improved by increasing Si content, and the microstructure and mechanical properties of F/M steel, especially the plasticity of F/M steel were affected simultaneously. The 5 types of 9%Cr F/M steels with Si content (mass fractions of 034%, 061%, 080%, 098% and 120%) were designed and prepared to develop the mechanical properties and corrosion resistance of the high Si content F/M steel. The samples of 9%Cr F/M steels were named Z1 Z5 according to different Si contents. And the sheet metal samples with thickness of 8 mm were prepared by vacuum melting, forging, hot rolling and final heat treatment. Optical microscope, scanning electron microscope, transmission electron microscope and energy spectrometer were used to characterize the microstructure of F/M steel matrix, M23C6 and Laves phase. The room temperature tensile properties and room temperature impact properties of F/M steel were tested in accordance with national standards of China. In result, the microstructure of F/M steel prepared by normalizing (1 050 ℃, 05 h, air cooling) and subsequently heated (760 ℃, 15 h, air cooling) at room temperature is all Martensitic. The grain size and Martensite lath width are not affected by the Si content. The yield strength and tensile strength of F/M steel at room temperature both increase as the increase of Si content. The influence of Si content on the structure and room temperature impact properties of F/M steel is divided into two stages. When the Si content in the steel is 034% 080% (mass fraction), the structure and room temperature impact properties of the steel change little. When the Si content in the steel is 0.98%-1.20%, the size and quantity of the second phase in the steel increase, and a small amount of Laves phase is precipitated along the Martensite lath interface, and the room temperature impact performance of the steel decreases. In this study, the optimal addition amount of Si element in the 9%Cr F/M steel is less than 08%, so that the steel has remarkable properties while maintaining high strength.