Abstract:Fracture of the SWRM6 wire coil occurred after the customer drawing . The investigations of the test of macroscopic observation, metallographic microstructure analysis and EMPA analysis showed that there were cracks existed at the margin of the sample and there were slags where the carbon content was higher than the basal body lied at the side of the cracks. Because of the existence of slags, on one hand the low plasticity led to the cracking during rolling and drawing, on the other hand, the formation of abnormal tissue martensite and carbide network due to the carburizing from rich carbon layer to the substrate surface accelerated the fracture during drawing.