Analysis of the evolution behavior of voids during the hot rolling process of medium plates

Void defects such as porosity, shrinkage, and the formation of gas cavities cannot be completely avoided during the casting process. One current method that improves the quality of these products is the use of a forging or rolling process. Further research on the evolution behavior of voids during processing is necessary. To this effect, the present study investigates the evolution behavior of a few different sizes of voids during the hot rolling process. Evolution behavior is analyzed by finite-element simulation and laboratory experimentation. Analysis focused on the stress field surrounding a void during the rolling process. Results showed that voids changed shape from spherical to ellipsoid, and as the rolling pass increased became smaller and more irregular. The upper and lower surfaces of the voids bonded together after the last rolling pass. Voids of varying size change shape in a similar manner, however, by analyzing their hydrostatic integration it was observed that smaller voids bond more readily than larger ones. The results demonstrate favorable agreement between experimental and simulated results.