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利用自制拉伸装量在光学显微镜下对球状石墨铸铁焊缝冷裂纹的萌生与扩展进行了动态观察.在拉应力作用下,塑性变形集中在铁素体区.裂纹的萌生部位有:(a)铁素体应变集中处,特别是近邻球状石墨之间的基体桥及表层下存在球状石墨的薄层铁素体处;(b)铁素体与珠光体交界处;(c)珠光体应变集中处.裂纹选择铁素体比例大的区域,穿过球状石墨间的基体桥,连接距离较近的球状石墨扩展.
Under the light microscope, the initiation and propagation of cold crack in the spheroidal graphite cast iron weld were observed under dynamic tension loading. Under the tensile stress, the plastic deformation was concentrated in the ferrite region.The crack initiation sites were: (a ) Ferrite strain concentrates, especially the base bridge between the adjacent spheroidal graphite and the thin-layer ferrite with spherical graphite under the surface; (b) the junction of ferrite and pearlite; (c) pearlite strain Concentration. Crack Choose a large proportion of ferrite area, through the substrate between the spherical graphite bridge, the connection of the distance closer to the expansion of spherical graphite.