Microscopic characteristics of scratch defects in strip steel coiling under different processes

The different characteristics of the scratch defects during coiling on the surface of hot rolled, acid washed plates, and zinc iron alloy plates were analyzed using macroscopic observation, chemical composition analysis, microscopic analysis. The results show that all three types of scratch defects were generated during hot rolling and had similar macroscopic morphology. They were all horizontally distributed and composed of dense point scratches. The iron oxide scale on the surface of the hot roll was damaged, and there were metal accumulation and iron oxide at the defect site. There were small and deformed grains in the microstructure. The iron oxide scale on the surface of the acid washed roll was washed away by acid, and there were small and deformed grains in the microstructure. The flatness of the surface of zinc iron alloy plates varies, and the degree of alloying was relatively light. No iron oxide was found in the substrate, and only small grains were present in the microstructure. Accurate process separation could be achieved through grain characteristics.