EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

Flatness is an essential property for the quality of heavy plates. To achieve the flatness required by the customer, levelling machines are used for many types of plates. Today, flatness is described by means of the deviation of the plate topography from a 1 or 2 m ruler according to DIN EN 10029. This measurement method does not provide any further information about the type of flatness defects. The commonly known value I-unit is used to determine unwindable flatness defects such as centre buckles or edge waves but does not provide information about windable flatness defects. In this work, a new method is presented to determine and quantify both windable and unwindable flatness defects as well as ski defects by means of characteristic values before levelling. The characteristic values are received from online measurements of the flatness gauge. Applying this characterisation method to real plates shows that the determined values are suitable for the characterisation of flatness defects of hot rolled plates. The data of type and magnitude of the flatness defects can be used to determine machine settings and strategies in hot plate levelling.