微量稀土元素对Q235B钢组织和性能的影响

Effect of micro-RE element on microstructures and mechanical properties of Q235B steel

为研究微量稀土元素对Q235B钢的夹杂物形态转化和细晶化及钢材强韧性能的影响,用真空感应炉熔化、精炼、制备了不同微稀土质量分数的钢样,用成分、OM、SEM、EDS和图像分析仪等方法,分析研究了微量稀土元素对Q235B钢微观组织和力学性能的影响.结果表明:在本研究条件下,随稀土量的增加,铁素体晶粒由24μm减小至12μm,珠光体组织被细化;MnS夹杂物由长条形变为小球形,氧化夹杂物由多棱角形变为椭球形,其尺度亦减小10倍;钢材力学性能直线增大,在稀土质量分数为36×10-6时,钢材的屈服强度、抗拉强度和冲击韧性分别达到382 MPa、555 MPa、172 J/cm2.

To study the effect of trace RE on the change of foreign inclusion shape,grain refining and obdurability of Q235B steel,the tested steel samples was refined with the addition of micro-rare earth alloy in a vacuum induction furnace,and optical microscope,SEM,EDS and image analysis were used to analyze the influence of rare earth element on microstructure and mechanical properties.The results show that,when the RE content was 0~36×10-6（mass fraction）,with the increase of RE content in the sample,the average ferrite grain size was reduced from 24 to 12 μm,and the structure of pearlite was obviously refined.The multi-angular oxide inclusions were changed into ellipsoidal oxide inclusions,and the strip MnS inclusions were changed into spherical inclusions.The mechanical properties of samples were substantially improved.When the RE content was 36×10-6,the yield strength,tensile strength and impact toughness value are 382 MPa,555 MPa and 172 J/cm2,respectively.