Bubble Size Measurement in a Continuous Casting Mold Using Physical Modeling and Shadowgraphy

Argon gas injection into a continuous casting mold (vessel with moving liquid) helps in increasing the casting sequence length by avoiding SEN clogging. Bubble formation may create bubble-related steel defects at specific operating conditions. Parametric estimation of bubble size distribution (BSD) and mean bubble diameter may identify the type of unforeseen defect in cast slab. Physical modeling experiments were performed to estimate Sauter mean diameter (SMD) of the bubbles for different input parameters such as gas/liquid flow rates and liquid properties. High-speed high-resolution imaging and advanced image processing were used to capture images from the physical model. Four different simulating liquids were used in the physical modeling experiment. Bubble characteristic data were used to measure the SMDs (output data). Different values of SMDs were correlated with the input parameters using direct multilinear regression (DMR). Experimental and predicted values were found well in agreement with high R2. A dimensionless equation was also determined using the same data and compared with the DMR correlation. DMR correlation was compared and validated with the previous work related to the bubbly flows in stagnant and moving liquid flow regimes. As a result, it was concluded that an increasing gas flow rate, a decreasing liquid flow rate, an increasing surface tension, and an increasing viscosity increase the SMD of bubbles formed in the mold.