摘要
采用化学成分C为0．13％～0．19％、Si为0．15％～0．25％、Mn为0．50%～0．70％、P为0．01％～0．025％、S为0．01％～0．03％的连铸坯，在首钢中厚板厂3500mm轧机上试制表层组织细品化的Q235钢中板。与正常生产同规格Q235钢中板一起进行了疲劳性能对比实验。采用扫描电镜观察了疲劳断口形貌。结果表明：表层组织细化的Q235钢中板，铁素体平均晶粒尺寸14．1μm．表层晶粒尺寸11μm，而正常生产钢板表层铁素体晶粒度25．8μm，平均26．4μm，表层与中心无明显差异。与正常生产同规格Q235钢板材比较，屈服强度提高40MPa左右。表层细晶化中板的疲劳性能优于正常生产晶粒较粗的板材。相近应力状态下，表层细晶化钢板的疲劳寿命是通常钢板的3．5倍以上，疲劳裂纹扩展第一阶段延长，扩展第二阶段的疲劳纹尺寸也减小。在承受比通常钢板应力高40MPa的前提下．表层细晶化钢板的疲劳寿命仍比通常钢板的长37％。因此，表层细晶化可使钢板的疲劳性能明显提高。
Q235 steel plates with fine grained ferrite in surface layers industrially produced by a special thermo-mechanical control process（TMCP）were tested for investigating the effect of ferrite grain refinement on fatigue behavior of the steel plates.And fatigue fractographs were observed and analyzed with the scanning electron microscope（SEM）.For the plates rolled by the special TMCP（named special plates）, the ferrite grain size approaches 11μm in surface layers and reaches 14.1μm in average while for the usually rolled plates,the grain size is 25.8μm in surface layers and 26.4μm in average.The yield strength of the special plates is 40 MPa higher than that of usually rolled plates. In a similar stress condition,the fatigue lifetime of the special plates is more than 3.5 times as long as that of usual plates, and the first stage of fatigue crack-propagation can be pro-longed, and the secondary fatigue cracks are smaller than that of usually hot-rolled plates.With the lifetime 37% more than that of usual plates,the special plates can sustain a stress range 40 MPa more than that the usual plates can sustain. Therefore, the fatigue properties have been obviously improved for the special plates with fine grains in surface layers.
出处
《首钢科技》
2005年第4期14-21,共8页
Shougang Science and Technology
基金
此项目为北京市科技新星计划资助项目（H013610320111）
