超快冷工艺对X70管线钢组织的影响

Influence of ultra-fast cooling on the microstructure of X70 pipeline steel

通过热模拟机研究超快冷工艺中冷却速率和终轧温度对X70管线钢组织细化及马氏体/奥氏体小岛的影响.随着冷却速率的增大,铁素体晶粒尺寸减小,M/A岛的体积分数先增大后降低,M/A岛的尺寸变化则相反.提高终轧温度,铁素体晶粒尺寸略微增大,M/A岛的体积分数增加;但在900～940℃范围内,随着终轧温度的升高,试样中M/A岛的体积分数略减小,尺寸增大.

The effects of cooling rate and finish rolling temperature on the microstructure refinement and marten- site/austenite （M/A） islands in X70 pipeline steel were studied with a Gleeble thermal-mechanical simulation machine. When the cooling rate increasing, the grain size of ferrite decreases, the volume fraction of M/A islands increases first and then decreases, but the dimensional change of M/A islands is opposite to the volume fraction. With the finish rolling temperature rising, ferrite in the steel slightly grows up and the volume fraction of M/A islands increases; but when the finish roiling temperature increases from 900 to 940℃, the volume fraction of M/A islands slightly decreases and the size of M/A islands increases.