细晶高强IF钢中第二相粒子固溶与析出规律的研究

发布时间：2018-04-19 09:25

  本文选题：细晶高强IF钢 + 奥氏体晶粒　； 参考：《辽宁科技大学》2015年硕士论文

【摘要】：近年来,由于人们对环境污染和能源问题越来越重视,要求汽车生产向轻量化方向发展,汽车用钢的高强度化是实现汽车生产轻量化的有效途径。无间隙原子钢(IF钢)兼具较高的强度与优异的深冲性能,在现代汽车生产中得到了大量的应用。随着汽车产业的蓬勃发展,对IF钢性能的要求也在不断提高,因此对IF钢做进一步的研发显得尤为重要。本文以细晶高强IF钢为研究对象,在不同的加热温度和保温时间条件下对实验钢进行回溶实验,然后利用光学显微镜观察实验钢中显微组织的变化规律,并采用透射电子显微镜对实验钢中第二相粒子的固溶析出规律与无沉淀析出区的形成机制进行研究,同时对实验钢进行力学性能检测。主要研究结果如下:1.细晶高强IF钢在加热过程中,随着加热温度的升高、保温时间的延长,第二相粒子的数量逐渐减少且尺寸逐渐增大,同时奥氏体晶粒逐渐长大。对OM实验数据进行非线性回归,拟合得到加热过程中奥氏体晶粒长大的数学模型为:2.由OM实验结果可知,细晶高强IF钢的奥氏体晶粒粗化温度为1050℃,奥氏体晶粒粗化时间为40 min。因此,实际生产中最好将加热温度控制在1050℃~1100℃、保温时间控制在30 min~40 min。3.TEM实验结果显示,实验钢中未溶的第二相粒子在低温时主要是呈圆形、椭圆形的富Nb析出相,在高温时主要是呈方形、长方形的富Ti析出相,当加热温度达到1150℃时,Nb元素基本完全固溶于铁基体中。理论计算表明,含Nb第二相粒子的全固溶温度为1130℃,理论计算结果与实验现象基本吻合。4.实验钢中由于析出相粒子的固溶和粗大化与晶界迁移造成的扫动效应,导致仅在晶界迁移方向的后方,形成独特的无沉淀析出区,且在退火过程中无沉淀析出区优先在晶界经过的区域形成。5.在退火过程中,随着退火温度的升高,细晶高强IF钢的屈服强度逐渐降低,n值逐渐增加,无沉淀析出区的平均宽度逐渐增大。因此可以推测,无沉淀析出区的平均宽度是影响细晶高强IF钢屈服行为和加工硬化行为的原因之一。
[Abstract]:In recent years, because people pay more and more attention to the environmental pollution and energy problems, the automobile production is required to develop to the direction of light weight. The high strength of automobile steel is an effective way to realize the light weight of automobile production.Non-gap atomic steel (if steel) has both high strength and excellent deep drawing performance, and has been widely used in modern automobile production.With the rapid development of automobile industry, the requirements of if steel properties are also increasing, so it is very important to further develop if steel.In this paper, the high-strength if steel with fine grain was used as the research object. The experimental steel was redissolved at different heating temperature and holding time, and the microstructure of the steel was observed by optical microscope.The rule of solid solution precipitation of the second phase particles and the formation mechanism of the precipitation zone without precipitation were studied by transmission electron microscope, and the mechanical properties of the experimental steel were tested.The main results are as follows: 1.With the increase of heating temperature and the prolongation of holding time, the number and size of the second phase of fine grained high strength if steel decrease gradually and the austenite grain grows gradually.The mathematical model of austenite grain growth during heating is obtained by nonlinear regression of OM experimental data.The results of OM experiment show that the austenite grain coarsening temperature is 1050 鈩，

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