Combined measuring system for an improved non-destructive determination of the mechanical/technological material properties of steel sheet

The main objective of the project was to develop and to test a pilot measuring facility based on a non-destructive multi-parameter testing method for rapid determination of direction-dependent material characteristics such as yield strength Rp0.2 and tensile strength Rm of steel sheet. This technology had to adapt the current state of development in non-destructive testing to operative requirements. The reduction of the measurement uncertainty to the required values could be shown at global correlation functions being applied to a combination of different material groups, where the target data Rp0.2 and Rm were spread across a sufficiently large range. Additionally, a detailed analysis of the disturbing influences and error sources led to the result that the measurement certainty reached at this time is nearly the optimum. This was also the reason why the combination of the two systems 3MA and HACOM was not realised. It was found that both systems were able to deliver measurement data of such quality, that a combination would lead to nearly no further increase in measurement certainty. So a decision was made to optimise each system separately. During the project, a second HACOM system was installed at the hot dip galvanising (HDG) line 2 in Salzgitter and a 3MA system in a HDG line in Duisburg. Regarding the transferability of the results, it could be shown during the installation that the basic set-up being used in the HDG line 1 in Salzgitter could be transferred to the system in the HDG line 2. In the same way, the basic parameters for the 3MA system used during the online tests in the HDG line 1 in Salzgitter could be used at the installation in a galvanising line in Duisburg. Modifications regarding the coefficient values of the correlation polynomals in both cases were necessary due to the different material treatment and environmental situation on each production line. Nevertheless, the correlation functions were able to use the same variables.