退火工艺对Nb-Ti IF钢组织和织构的影响

EFFECT OF ANNEALING PROCESS ON THE MICROSTRUCTURE AND TEXTURE OF IF STEEL MICRO-ALLOYED WITH Ti AND Nb

以典型成分Nb-Ti IF钢冷轧硬卷为研究材料,结合改良森吉米尔法和美钢联法连续热镀锌线的工艺特点,采用Gleeble-1500模拟退火方法和金相、X射线织构测试和硬度测试等分析手段,系统研究了退火工艺对试验钢组织和织构的影响。研究结果表明,退火加热温度在720℃以上时为完全再结晶组织,加热温度在720℃至840℃间变化时,铁素体晶粒度在10.0级左右,加热温度为880℃时,铁素体晶粒度为9.0级,模拟2号线工艺相对模拟1号线工艺而言,在相同的加热温度条件下,铁素体晶粒稍粗大一些;随加热温度的升高,试验钢的硬度下降,当加热温度为920℃,因保温后快速冷却得到非等轴组织,虽然组织粗化,但硬度却有所提高,2号线相对1号线工艺而言,由于铁素体晶粒尺寸较粗大,因而显微硬度较低;当加热温度为840℃时,保温时间在30s至60s间变化时,铁素体晶体尺寸变化较小,但当加热时间从30s增加到45s时,显微硬度明显降低,加热时间进一步增加到60s时,显微硬度变化不大。试验钢退火后具有较强的{223}<110>和{114}<110>织构,且退火工艺条件对它们的影响较小,随着退火温度的升高,{554}<225>、{111}<112>和{111}<110>等组分的取向密度增加趋势较明显,特别是在模拟2号线工艺条件下。

Combined with the improved Sendzimir coating process and the continuous galvanizing line of USS, the annealing process of the cold rolled IF steel bearing with Ti and Nb is studied especially its effect on the microstructure and texture of the test steel. Experimental result shows when annealed above 720℃, the microstrueture is re-crystallized totally. While annealed between 720℃ and 840 ℃, the grain size number is 10, but at 880℃, it is 9. The hardness of the steel lowers as the annealing temperature gets high. However, as the temperature reaches at 920℃, though the grain size gets bigger, the hardness gets higher oppositely since the non-equiaxed grain is obtained after quick cooling. When soaking at 840℃, the soaking time changes from 30 to 60s, the grain size changes quite less. After annealing, the microstructure exhibits strong texture of {223}〈110〉 and {114}〈110〉, which are less affected by the annealing process. When temperature rises, the density of {554}〈225〉, {111}〈112〉 and {111}〈110〉 texture gets higher.