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Zhao X.-K.,Tangshan Jianlong Industrial Co. | Sun B.-L.,Tangshan Jianlong Industrial Co. | Li C.-Y.,Tangshan Jianlong Industrial Co. | Han Z.-X.,Tangshan Jianlong Industrial Co.
Guocheng Gongcheng Xuebao/The Chinese Journal of Process Engineering | Year: 2010

SEM, EDS and metallographic microscope were been used to study flakes peel-like defects on the surface of cold-rolled strip steel combined with mathematical simulation. The analytical results show that the flakes peeling was induced by non-metallic inclusions and scales. Inclusions could be derived from steel de-oxidation or slag entrapment, and scales, initiating cracks inside billet, which could be exposed to the surface on cold-rolling process, were caused by de-carbonization because of improper heating mode or time. Numerical simulation shows that after pouring within the first 6 s, temperature dropped to 124.9°C/s and solidified shrinkage rate to 0.07 mm/s, that makes corner cracks. Crack index of solidified front increased up to 0.75 at the end of solidification, with formation of porosity and shrinkage cavity. Crack index was over 1 near the surface from the edge to 41 mm thickness, where middle cracks formed. Temperature rally in the secondary cooling zone II resulted in extension of middle cracks along columnar grain boundary.

Zhao X.-K.,Tangshan Jianlong Industrial Co. | Liu J.-W.,Tangshan Jianlong Industrial Co. | Liu X.-F.,Tangshan Jianlong Industrial Co. | Ju W.,Tangshan Jianlong Industrial Co.
Kang T'ieh/Iron and Steel (Peking) | Year: 2010

The production of low carbon Al-killed steel has been separated into CCR and TSCR. Though analysis of microstructure, SEM, EDS and texture, the stamping properties have been studied on structure, grain, free cement and main texture. Furthermore, the reasons of stamping cracking have been investigated. Practice shows if three critical factors, including free cement, ferrite grain and AlN precipitation, were controlled reasonably in traditional process, the stamping properties could satisfy the requirement of DC04, up to micro-carbon mechanical, making enormous economic benefits.

Li X.,University of Science and Technology Beijing | Yang P.,University of Science and Technology Beijing | Lin R.-M.,Tangshan Jianlong Industrial Corporation Ltd | Liu X.-F.,Tangshan Jianlong Industrial Corporation Ltd | Chen L.,University of Science and Technology Beijing
Beijing Keji Daxue Xuebao/Journal of University of Science and Technology Beijing | Year: 2010

Taking batch annealed SPCD steel sheets as an example, orange peel defects in the surface of sheet stamping concerning with their formation mechanism and dependence on grain orientation were investigated by means of SEM, XRD and electron backscatter diffraction (EBSD) techniques. The results show that the orange peel defects are resulted from excessively coarse ferrite grains, whereas weak favorable {111} texture and a larger stamping value might be the key factors aggravating the formation of orange peel defects. Different morphologies featured by smooth and rough zones on the free surface of orange peel do not show remarkable dependence on grain orientation, and both display orientation feature with dominant {112} <110> and {111} <110> textures. The surface contact condition plays an important role in the surface morphology.

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