Early interlaminar cracks and tensile fractures in Non-oriented electrical sheets caused by uncoordinated deformations during cold rolling

Abstract

Uncoordinated deformations in non-oriented electrical sheets during cold rolling were investigated for exploring their destruction behaviors. The sheets with interlaminar failures or tensile failures were observed for displaying the influence of matrix factors on crack initiations and growths by using a scanning electron microscope (SEM), equipped with an electron backscattered diffraction (EBSD) detector. The interlaminar failures would grow along the boundaries between deformed layers and undeformed layers, or within seriously deformed layers. According to strain contouring (SC) or local misorientation (LM) maps, the cracks adjoining with dense strain centers or serious local misorientations belonged to plastic failures. And brittle cracks preferred to exist in undeformed layers. In addition, the tensile failures were often located in laminated layers with alternately diverse deformations. The regions adjoining to this kind of tensile cracks were alternately covered by the deformed layers and undeformed layers. All failures above were caused by uncoordinated deformations, showing different intensities of strain centers in each laminated layer. And the uncoordinated deformations could be caused by differences of deformation ability or borne deformation component of each layer. The grains with poor deformation ability and serious deformation component would achieve deformation limits and be broken early, causing crack initiations. And the grain layers with predominant deformation loads would originally attract excessive deformation components and be broken early. Adopting even sheets or high-tension rolling could even the deformation distribution and fill the disadvantage of insufficient deformation ability of some layers for reducing early failures. This investigation would benefit avoiding early failures during cold rolling processes and reducing correlative scrap products and extra energy consumptions. Meanwhile, economic performance and energy conservation would be achieved, also benefitting steel mill factories and long-term environments.