轧制与冷却工艺对高强度管线用宽厚钢板组织与性能的影响

Influence of Rolling and Cooling Processes on Microstructure and Performance of High-strength Wide and Heavy Steel Plate for Pipeline

利用工业试验和热模拟试验研究了未再结晶区轧制温度、弛豫时间、终冷温度对X80级管线用宽厚钢板微观组织和性能的影响。结果表明:在770~880℃的温度范围内,随着未再结晶区轧制温度的降低,钢中位错密度和形核位置增加,奥氏体向铁素体转变温度升高,铁素体体积分数增大,试验钢的屈服强度升高、韧性改善;终轧温度为790℃时,奥氏体晶界附近形成了细小连续的铁素体;弛豫过程通过对位错、溶质原子、析出相、微观组织等多方面的影响来引起性能的变化;终冷温度的降低会促进贝氏体铁素体(BF)的形成,并抑制Nb(CN)析出,使钢板获得良好的韧性和更小的屈强比。

Effects of non-recrystallization rolling temperature,relaxation time and final cooling temperature on the microstructure and performance of X80-grade wide and heavy steel plate for pipeline were investigated by industrial and thermal simulated tests.The results indicated that in the temperature range of 770℃to 880℃,with the decrease in rolling temperature in the non-recrystallization zone,the dislocation density and nucleation sites in the steel increased,the transformation temperature from austenite to ferrite increased,and the volume fraction of ferrite increased,thus the yield strength and toughness of test steel increased.Fine and continuously distributed ferrite was formed near austenite grain boundary after finishing rolling at temperature of 790℃.The relaxation process caused the chang of performance through affecting dislocations,solute atoms,precipitations and microstructures,etc.The decrease in the final cooling temperature could promote the formation of bainite ferrite(BF)and inhibit the precipitation of Nb(CN),resulting in good toughness and lower yield ratio of steel plate.