【摘要】：采用OM、TEM和EDS分析技術,研究了1000 MPa級Nb-Ti微合金化超高強度鋼在不同加熱溫度下保溫不同時間時奧氏體晶粒粗化行為與微合金元素碳氮化物溶解行為。結果表明,鑄坯中存在尺寸與形狀明顯不同的3類析出物:尺寸大于1μm的方形Ti N粒子;尺寸在500 nm以下的球形、橢球形或方形Nb、Ti復合析出物;少量方形或橢球形Ti S或Ti(C,S)析出物。隨著溫度的升高,原始奧氏體晶粒尺寸呈現出單調增大的趨勢,當加熱溫度超過1200℃時奧氏體晶粒發(fā)生快速長大,而析出物數量不斷減少、尺寸逐漸增大、Ti/Nb原子比逐漸升高,EDS顯示均為Ti、Nb復合析出。隨著保溫時間的延長,原始奧氏體平均晶粒尺寸呈拋物線規(guī)律長大,小尺寸的球形、橢球形的析出物逐漸溶解,大尺寸方形析出物數量逐漸增加且棱角變得模糊。綜合考慮加熱溫度和保溫時間對Nb、Ti微合金元素的固溶行為和奧氏體晶粒粗化行為的影響,1000 MPa級Nb-Ti微合金化超高強度鋼的加熱溫度和保溫時間分別為1250℃和80 min較合適。
[Abstract]:The coarsening behavior of austenite grain and dissolution behavior of microalloyed carbon nitride of 1000 MPa Nb-Ti microalloyed ultra-high strength steel at different heating temperatures and different time were studied by means of OM,TEM and EDS analysis techniques. The results show that there are three kinds of precipitates which are obviously different in size and shape: square Ti N particles larger than 1 渭 m in size, spherical, ellipsoidal or square Nb,Ti composite precipitates in size less than 500 nm. A small amount of square or ellipsoidal Ti S or Ti (C, S) precipitates. With the increase of temperature, the grain size of original austenite increases monotonously. When the heating temperature exceeds 1200 鈩，

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