Nb在超快冷条件下的低温析出行为

 通过热模拟试验和实验室热轧试验，结合含Nb船板钢的CCT曲线，重点研究了超快冷条件下试验钢中Nb在相变区的析出行为。结果表明，试验钢变形后快速冷却至600℃保温不同时间时，得到的组织为针状铁素体组织，而在650℃等温时，组织中多边形铁素体含量随等温时间延长逐渐增多；不同温度下保温，随着保温时间的延长，析出相粒子的数量有所增多，尺寸也有所增大；在实验室条件下采用910℃终轧＋超快速冷却工艺，相比于850℃终轧＋层冷工艺组织中的粒子析出量大大增加，微合金的析出强化作用得到加强，得到轧件的强度相比于低温终轧并没有降低，说明超快速冷工艺不仅可以更好地发挥Nb的析出强化作用，提高含Nb船板钢的强度，而且可以适度提高试验钢的终轧温度，降低轧制力，提高轧制节奏。

Low-Temperature-Precipitation Behavior of Nb Under Ultra-Fast Cooling Process

With a kind of ship plate steel containing Nb, the precipitation behavior of Nb in transformation region was mainly studied through thermal simulator experiments and laboratory rolling test, and the dynamic continuous cooling transformation (CCT) diagrams for tested steel was gained. The results show that: the acicular ferrite is gained when the deformed sample was held at the quickly cooling finish temperature 600℃ for different holding time, while held at 650℃, the content of polygonal ferrite increases with holding time prolonged; the number and the size of precipitation particles also increase with holding time prolonged at different temperatures; in laboratory rolling experiment, comparing with finishing temperature 850℃ using laminar cooling process, finish rolling at 910℃ with ultra-fast cooling(UFC) process can gain more precipitation particles in microstructure, so the precipitation strengthening was enhanced and the strength do not decrease at higher finishing temperature; UFC process not only can improve precipitation hardening for niobium, but also can decrease the rolling load and increase the rolling pace because of higher finishing temperature.