材料期刊网

研究了一种低碳含铜NV-F690钢连续冷却相变规律,设计了控制轧制＋直接淬火（DQ）＋两相区淬火（L）＋回火（T）新工艺（DQ-LT）,研究了试验钢分别在传统的淬火回火、DQ-T和DQ-LT等条件下组织性能随工艺参数的变化规律。结果表明：试验钢经水淬（WQ）后的显微组织为板条马氏体（LM）,经650℃回火1 h后达到最佳强韧性匹配;经油淬（OQ）得到粒状贝氏体（GB）,其韧性降低。DQ-T钢板具有抗回火软化性,经过680～705℃回火1 h后其强韧性匹配达到最佳。经过DQ-LT工艺处理钢板的显微组织为作为软质相的准多边形铁素体（QPF）和作为硬质相的含弥散富Cu析出相的LM和LB晶粒,韧性得到进一步改善。DQ-LT钢最佳强韧性匹配为：屈服强度（Rp0.2）=793 MPa、抗拉强度（Rm）=908 MPa、伸长率（A）=19%,夏比冲击吸收能量KV2（-80℃）=83 J。

Continuous cooling transformation（CCT） behavior of a low-carbon copper bearing NV-F690 steel was studied.Microstructure and properties of the steel plates processed by conventional reheating,quenching and tempering,controlled-rolling and accelerated-cooling followed by tempering（DQ-T）,and reheating into α＋γ region followed by quenching and tempering（DQ-LT） were investigated.Microstructure of the steel is lath-like martensite（LM） after water quenched（WQ） and yields balanced strength and toughness of the steel after tempering at 650 ℃ for 1 h is best.Granular bainite（GB） is obtained by oil quenching（OQ） which deteriorates the toughness.High strength accompanied with high toughness achieved in the DQ-T treated plate is due to tempering resistance of the steel at 680-705 ℃.The microstructure of steel plate treated by the DQ-LT process is consisted of quasispolygonal ferrite（QPF） with coarse Cu containing particles as soft phase and tempered LB grains with dispersed Cu containing precipitates as hard phase leading to improvement of low temperature toughness over the DQ-T steel plate.Balanced combination of strength and toughness achieved in the DQ-LT treated steel plate is as follow： Rp0.2 of 793 MPa,Rm of 908 MPa,total elongation（A） of 19% and Charpy impact energy（KV2） of 83 J at-80 ℃.