高强度管线钢连续冷却转变及组织研究

Continuous cooling transformation and microstructure of high strength pipeline steel

研究低碳微合金X80和X100管线钢分别在未变形和变形条件下的连续冷却转变（CCT）行为。用Gleeble-2000热模拟试验机,结合OM、SEM和TEM等方法测定未变形和变形奥氏体的连续冷却转变曲线,并对不同冷速和变形条件下的组织进行观察分析。结果表明,冷速较低时,连续冷却转变组织主要为多边形铁素体和珠光体,随着冷速提高依次出现块状铁素体,粒状铁素体,针状铁素体,贝氏体铁素体等组织。热变形能强烈促进针状铁素体的形成,使针状铁素体的相变温度提高50-100℃,并使CCT曲线向左上角移动，同时使晶粒细化及取向更加无序。

Continuous cooling transformation（CCT）behaviors of X80 and X100 low-carbon microalloyed pipeline steels were investigated under the undeformed and deformed conditions,respectively.The corresponding CCT diagrams were constructed by using a Gleeble-2000 thermomechanical simulator,and microstructure of the steels at different cooling rates and deformation conditions was observed by OM,SEM and TEM.The results show that polygonal ferrite and pearlite can be formed at low cooling rates,massive ferrite,granular ferrite,acicular ferrite and bainitic ferrite can be obtained with increase of the cooling rate.Furthermore,hot deformation can strongly promote the formation of acicular ferrite,that is,the transformation temperature of acicular ferrite is increased by 50-100 ℃,this leads to CCT curves move towards the top left corner,which results in grain refining and more random orientation.