Ti对700 MPa级汽车大梁钢奥氏体晶粒长大的影响  

Effect of Ti on austenite grain growth behavior of automobile beam steel with yield strength of 700 MPa

作　　者：李永亮[1] 王福明[1] 李长荣[2] 杨占兵[1] 郭亚婷[1] 何煜天 

机构地区：[1]北京科技大学冶金与生态工程学院,北京100083 [2]北京科技大学材料科学与工程学院,北京100083

出　　处：《材料热处理学报》2016年第7期117-122,共6页Transactions of Materials and Heat Treatment

基　　金：国家自然科学基金(51174020;51374018);国家高技术研究发展计划(2013AA031601)

摘　　要：利用光学显微镜(OM)、扫描电镜(SEM)等研究了Ti含量对700 MPa级汽车大梁钢奥氏体晶粒长大和析出相的影响。结果表明,添加Ti后的实验钢中主要析出相由单一Nb C转变为(Nb,Ti)C和Ti(C,N),随着Ti含量的增加,奥氏体晶粒得到有效细化。Thermo-calc热力学计算表明,钢中的(Nb,Ti)(C,N)和Ti(C,N)析出相析出温度比Nb C明显提高,因而能够在更高温度下稳定存在并对晶界迁移起到抑制作用。用Beck方程对奥氏体晶粒的长大行为进行了描述,并给出了晶粒长大的数学模型。随着Ti含量的增加,Beck方程的时间指数n呈现降低趋势,但晶界生长的扩散激活能反而升高。Ti的碳氮化物对晶界的钉扎和拖曳效应是晶界迁移扩散激活能升高的主要原因。The effects of Ti content on austenite grain growth behavior and carbonitride precipitation of automobile beam steel with yield strength of 700 MPa were studied by means of optical microscope, cold cathode field emission scanning microscopy （FE-SEM）. The results show that the grains are refined with the increasing of Ti content. Equilibrium phase diagrams calculated by Thermo-calc show that the initial precipitation temperature of the （ Nb, Ti） （ C, N） or Ti（ C, N） is higher than that of NbC. Therefore, they are much more stable at high temperatures, and can hinder the mobility of grain boundary at higher temperatures. The Beck equation is utilized of describing the grain growth behavior, and the mathematical model of grain growth is provided. The time exponent n declines with the increasing of Ti content, but the activation energy of grain growth increases at the same time. The increasing of activation energy is attributed to the dragging or pinning effect of earbonitride precipitates of Ti.

关 键 词：奥氏体晶粒 碳氮化物 Beck方程 扩散激活能 

分 类 号：TG142.4[一般工业技术—材料科学与工程]