回火温度对控制冷却贝氏体钢组织与性能的影响

Effect of tempering temperature on microstructure and properties of bainitic steel with controlled cooling process

采用力学试验机、光学显微镜、透射电镜、X射线衍射仪研究了回火温度对控制冷却贝氏体钢组织与性能的影响。研究了试验钢3%塑性变形后残留奥氏体的稳定性。结果表明,200~350℃,随着回火温度的提高,抗拉强度、横断面硬度、残留奥氏体含量均缓慢降低,而规定塑性延伸强度、屈强比、断面收缩率和冲击性能随之提高,450℃回火时强韧性指标均大幅降低。3%塑性变形后残留奥氏体转变比例随回火温度提高呈先增加后降低趋势。显微组织与TEM分析表明,450℃回火时性能变化与贝氏体铁素体多边形化以及原有板条铁素体与薄膜残留奥氏体交替排列的结构改变有关。350℃是该钢适宜的回火温度。

Effect of tempering temperature on microstructure and properties of bainitic steel with controlled cooling process was studied by using mechanical test machine,optical microscope,transmission electron microscope and X-ray diffractometer. stability of retained austensite after 3% plastic deformation was also studied. The results indicate that the tensile strength,cross-section hardness and the content of retained austensite decrease slowly while the specified plastic extension strength,yield/tensile ratio,reduction of area and impact property increase with the rise of tempering temperature within 200-350 ℃. Both the strength and toughness index all substantially reduce at 450 ℃.The transition ratio of retained austensite increases first and then decreases after 3% plastic deformation with the rising of tempering temperature. Microstructure and TEM analysis show that changes of the properties of the steel tempered at 450 ℃ are relevant to bainiteferrite polygonization and the arranged alternately between the retained austensite film and the existing lath ferrite. 350 ℃ is the appropriate tempering temperature of the tested steel.