Application of Non-Destructive Testing, ANSYS Analysis and Advanced Microstructural Characterization to Detect-Locate-Define and Simulate Defects in AHSS Steel Slabs

During continuously casting of steel slabs production, the presence of surface and internal defects takes place. These defects can include cracks, voids, coarse non-metallic inclusions and heavy local chemical and microstructural segregation. Many NDT techniques have been developed and used to assess the presence of these defects which have a specific “fingerprint” response to sound waves interaction. The factors responsible for these defects are often related to mechanical, thermal, or transformation stresses during the solidification process of the slabs. The high thermal stresses result from the difference in volume expansion or contraction behavior caused by the frequency of the temperature fluctuation during solidification. In order to study the effect of these temperature fluctuations a model of the thermal stress field using ANSYS simulation software was employed. In addition, to validate the model results a NDT-UT system was used to detect and localize the presence of the defects caused by thermal or transformation stresses. The results from the NDT-UT scanning were assessed with the image processing analysis to identify the size of the defects and their location in the slabs. These results were complemented with a systematic advanced microstructural characterization technique. The results of this study will be presented and discussed.

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