Surface defect of IF steel after the deep drawing process

Abstract

The aim of this project is to run large EBSD analysis in samples of IF steel in order to look for unusual crystallographic patterns that can provide an explanation for the defects that are observed after the deep drawing process. The analysed samples are obtained from two identical IF steel sheets that belong to the same coil, just before these are subjected to the deep drawing process. Since these defects have never been observed before in mild steels, very few is known about this problem. The main objective of the project is to run EBSD analyses embracing an area sufficiently big to observe variations along the surface. However, before starting with the EBSD scans, a good technique is required for the sample preparation procedure, since the reliability of these analysis lie on the perfectibility of the samples. Furthermore, before starting with the EBSD analysis, a first approach is done using a digital microscope in order to study the geometry of the undulations once they can be observed after the deep drawing. This exploratory study with the digital microscope sheds a little light to the problem and provides an idea on how the EBSD analysis have to be done. The main drawback derived of the EBSD technique for obtaining crystallographic information is that the length of the scans must be of several millimetres. Generally, before doing an EBSD analysis a very important part consists on choosing a representative zone for the scan, so that the information obtained can be extrapolated to a bigger area. In the case of study, a really big area is required. There is not a specific method to run large scans, but the main possibility is to run several analysis in consecutive parts of the sample and, afterwards, merge them together in one big analysis. Therefore, the geometry of each consecutive scan has to be very precise so that the merging process can be successfully done and the results can be reliable.