微量Mg添加对2.25Cr1Mo压力容器钢板奥氏体晶粒长大行为的影响

Effect of Trace Mg Addition on Austenite Grain Growth in 2.25Cr1MoPressure Vessel Steel Plate

为揭示Mg对低合金钢奥氏体晶粒长大的作用,以2.25Cr1Mo压力容器钢板为研究对象,利用真空感应炉、450型双辊可逆轧机制备不加Mg和加Mg的热轧板材,采用光学显微方法和专业图像软件等分析研究了试验钢在900~1 200℃温度范围内加热时奥氏体晶粒长大行为,并对奥氏体晶粒变温长大动力学方程进行了数学回归分析。结果表明,在900~1 000℃加热时,Mg对奥氏体晶粒有细化作用;在1 100~1 200℃加热时,Mg对奥氏体晶粒无细化作用。数学回归分析表明,Mg添加可增大奥氏体晶粒长大激活能,在900~1 000℃温度范围内阻碍奥氏体晶粒长大。较低温度下Mg添加阻碍奥氏体晶粒长大与其在晶界或相界处碳化物的偏聚发挥钉扎作用有关,由于较高温度下固溶Mg不具有钉扎奥氏体晶粒长大的作用,致使奥氏体晶粒明显粗化。

In order to reveal the effect of Mg addition on austenitic grain growth of low alloy steel,2.25Cr1Mo pressure vessel steel plate was used as the research object,and the hot rolled plate without Mg and with Mg was prepared by vacuum induction furnace and type 450 double⁃stick reversible rolling mill.The austenite grain growth behavior of the test steel was studied by optical microscopy and professional image software in the temperature range of 900~1200℃,and the dynamical equations of austenite grain growth was analyzed by the mathematical regression.The results show that when heated at 900~1000℃,Mg can refine the austenite grains.When heated at 1100~1200℃,Mg has no refining effect on austenite grains.Mathematical regression analysis shows that Mg addition can increase the activation energy of austenite grain growth,and hinder the austenite grain growth in the temperature range of 900~1000℃.The retardation of austenite grain growth by Mg addition at lower temperature is related to the pinning effect of carbide segregation at grain boundaries or phase boundaries.As the solid solution Mg does not have the effect of pinning austenite grain growth at higher temperature,the austenite grain coarser obviously.