Analysis of sheet steel fracture during deep drawing.pdf

Analysis of Sheet Steel Fracture during Deep Drawing (continued) 20 Journal of Failure Analysis and PreventionVolume 5(5) October 2005 Analysis of Sheet Steel Fracture during Deep Drawing J.L. McDougall, M.E. Stevenson, and K. McKeever (Submitted June 27, 2005; in revised form August 2, 2005) Low-carbon steel sheet used for the fabrication of automotive brake components was tearing during deep drawing. The associated mill certificates revealed that the coil met the specified chemical composition and mechanical properties. Metallographic evaluation revealed a severe variation with respect to grain size through the thickness of the steel sheet, as well as a slight segregation of pearlite. Insufficient temperature during hot rolling in combination with a high coiling temperature resulted in the observed microstructural gradient. The anisotropic mechanical properties were amplified by the slight carbon segregation. Keywords: JFAPBC (2005) 5:20-25 ? ASM International DOI: 10.1361/154770205X65972 1547-7029 / $19.00 Introduction In an effort to stay competitive, many metal product manufacturers in the United States have opted for an increased reliance on imported steel. This change in suppliers provides a challenge to the materials specification process and can allow the receipt and use of unacceptable material. The primary driving force behind the decision to change suppliers is generally financial. However, financial savings, while seemingly substantial, can be erased when unforeseen production failure and material deficiencies occur. While the quality and capability of many foreign steel mills meets or exceeds that of domestic mills, the lack of experience in supplying material for a specific operation often translates into the lack of ability to assure the high quality of steel required for the production process. Over the past several years, the authors have observed a significant increase in failures related to steel quality. Product manufacturers that had rarely or