S元素含量对IF钢热轧析出物的影响

在Gleeble-3500热模拟试验机上,利用模拟轧制和卷取方法研究了不同S含量Ti-IF钢热轧成品第二相粒子的析出行为。试验结果表明,Ti-IF钢的析出物类型随着S含量的增加出现明显变化,当S质量分数为140×10^-6时,大尺寸析出物中出现TiS单独析出情况,同时随着钢中S含量的增加,大尺寸析出物(200 nm以上)逐渐增多,主要析出物类型为TiS和Ti₄C₂S₂;而小尺寸析出物(20 nm以下)逐渐减少,主要析出物类型为TiC。结合钢种的热力学分析可知,当S含量增加时,基体内固溶的C原子,首先满足Ti₄C₂S₂形成的需要,其次再以TiC的形式析出,可见S元素对固定间隙C原子有明显作用,由此提出钢种设计时S元素含量按下限设定的理论。

Effect of sulfur element content on precipitates of IF steel during hot rolling

The precipitation behavior of the second phase particles in the hot rolled products of Ti-IF steel with different sulfur content were studied by simulated rolling and coiling on Gleeble-3500.The results show that the precipitate type of Ti-IF steel changes obviously with the increase of sulfur content.When sulfur content increases to 140×10^-6,the large-size precipitate (TiS) will be separated.At the same time,with the increase of sulfur content in steel,the large-size precipitate (above 200 nm) will be gradually increased,the main precipitate types are TiS and Ti₄C₂S₂,the small-size precipitate (below 20nm) will be gradually decreased,the main precipitate type is TiC.According to the thermodynamic analysis of steel,when the content of sulfur increases,the first,precipitation is to complete the formation of Ti₄C₂S₂,the second step is to complete the formation of TiC.It can be seen that sulfur has a significant effect on fixed the atom C.Therefore,the lower limit of sulfur content is proposed in the process design of steel grades.