锌锅用热轧钢板解理断裂行为分析简

 通过断裂试样断口的宏观和显微分析、显微组织表征、拉伸和冲击试验以及解理断裂应力条件,讨论分析了锌锅用低强度级别钢板弯曲成形断裂的微观解理断裂行为。结果表明,钢板发生解理断裂的微观机制与冲击试样断裂相同，即晶粒尺寸控制的穿过晶界的裂纹扩展是解理断裂的临界事件。粗大的铁素体晶粒的面积分数过高显著降低了裂纹扩展阶段所需的局部解理断裂应力σf。断口宏观分析判断在钢板边部应存在导致应力集中的初始裂纹源，这极大降低了启动解理断裂的断裂应力并同时提高裂纹源前端的正应力σyy，扩大了解理断裂活跃区至初始裂纹前端，从而不可避免地发生脆性解理断裂。

Analysis of Cleavage Fracture Behavior of Hot-Rolled Steel Plate for Zinc Boiler

The cleavage fracture behavior during bending of the hot-rolled steel plate for zinc boiler was investigated by both visual and microscopic analysis on fractography, microstructural characterization, tension and Charpy impact test, and discussion of cleavage fracture stress. The critical importance of crack propagation across ferrite grain boundaries, which is controlled by high fraction of coarse grains, for the cleavage fracture development of the plate was confirmed by Charpy impact test. The local cleavage fracture stress σf required by the cleavage crack propagation decreases remarkably when the crack tip is surrounded by the coarse-grain zone, which was statistically measured with high area fraction in the steel. The macrofractographic examination indicates the pre-exist crack initiation on the one edge-side section of the plate, which can concentrate the normal stress σyy in front of the crack initiation and also lower the cleavage fracture stress dramatically. Thus the active zone of cleavage fracture is expand to the root of crack tip and the cleavage fracture is unavoidable.