调质工艺对620 MPa级高强钢组织及性能的影响  

Effect of quenching and tempering process on microstructure and properties of 620 MPa grade high strength steel

作　　者：黄乐庆 狄国标[1] 杨永达[1] 王彦锋[1] 麻庆申[1] 王小勇[1] 

机构地区：[1]首钢技术研究院,北京100041 [2]北京市能源用钢工程技术研究中心,北京100041

出　　处：《材料热处理学报》2017年第9期128-136,共9页Transactions of Materials and Heat Treatment

摘　　要：通过拉伸、系列冲击以及NDT落锤试验,采用SEM、TEM及EBSD技术手段,研究了轧后空冷+离线淬火+回火(QT)与轧后在线淬火+回火(DQT)工艺对620 MPa级高强钢组织及力学性能的影响。结果表明,调质后组织均为回火索氏体,但DQT工艺下组织粗大、扁平化且板条更加细长;淬火后试样在回火过程中,随着回火温度的升高,强度降低,塑性升高,且在线淬火试样纵向强度高于横向;在相同的回火工艺下,经DQT工艺处理的试样强度高于QT工艺处理的试样,但QT工艺下的调质钢断后伸长率、韧脆转变温度(FATT)及无塑性转变温度(NDTT)高于DQT工艺处理的试样。离线淬火工艺下的调质钢位错密度低、马氏体板条块尺寸小、残留奥氏体及大角度晶界含量高,该工艺处理后试样具有较低的韧脆转变温度和良好的止裂性能。The effects of QT（ air cooling after rolling and off-line quenching and tempering） and DQT（ on-line quenching and tempering after rolling） process on microstructure and properties of 620 MPa grade high strength steel were studied by means of SEM,TEM and EBSD technique.The results show that the microstructure consists of tempered martensite after QT and DQT process,but the grain is coarser,flatter and slender after DQT process.With the increasing of tempering temperature,the strength of the steel decreases and the ductility increases,and the strength is higher in the longitudinal direction than that in the transverse direction after DQT process.Under the same tempering process,the strength（ Reland Rm）of the steel treated by DQT process is higher than that by the QT process,but the elongation,fracture appearance transition temperature（ FATT） and nil-ductility transition temperature（ NDTT） of the steel treated by QT process are higher than that by the DQT process.The quenched and tempered steel under off-line quenching process has lower dislocation density,smaller martensite plate block size,higher content of retained austenite and high-angle boundaries,and thus has a better toughness performance at low temperature and a good crack arrest performance.

关 键 词：离线淬火 在线淬火 组织与性能 低温韧性 

分 类 号：TG142.7[一般工业技术—材料科学与工程]