Causes of Cold Bending Cracking of Q960 High Strength Steel Plate forConstruction Machinery

The cracking causes of Q960 high strength steel plate for construction machinery during cold bending process were analyzed by macromorphology observation, chemical composition analysis, microstructure observation, fracture morphology analysis, micro-hardness test, and instrumented impact test. The results show that the cracking property at the cold bending location of Q960 high strength steel plate was microcrack initiation and propagation induced by tensile stresses. During the cold bending process, the bending circular surface of the steel plate was subjected to tensile stresses, so cracks were initiated at the large TiN inclusions in the original slab. The cracks propagated along the transverse and longitudinal directions, leading to cracking of the steel plate. To avoid the recurrence of similar failure, the titanium mass fraction should be reduced from 0.18% to 0.15%, and the nitrogen mass fraction should be controlled within the range of no more than 0.003% to reduce the amount of large TiN inclusion precipitate.