The Effect of Water Jet Overlaps in a Descaler on the Quality of Surface of the Hot Rolled Steel

Abstract

Hot rolling is a highly efficient steel processing method involving the heating and subsequent rolling of semi-finished cast products within mills; however, heating results in the formation of an undesirable, inhomogeneous oxide layer on the surface. Removal of this layer, known as scales, prior to rolling is essential to prevent scales from being rolled into the surface. The scales are removed in the descaler. Most descalers use multiple high-pressure hydraulic descaling nozzles with overlapping sprays. This setting can cause excessive cooling in the overlap area, uneven descaling of the surface, and the presence of residual scales. It can also result in uneven cooling at the finishing line. This study illustrates a typical nozzle configuration commonly used in industrial plants in the hydraulic descaling process and compares its results with a new configuration. The research focuses on examining the overlap area and the washout area of the sprays. The goal is to address the inhomogeneous descaling problem and propose procedures to prevent residual scales. It was shown that one of the problematic areas is the washout area, where the average thickness of the remaining scales was more than four times higher than other descaling areas. Reducing the offset angle has proven to be a good way to eliminate the washout area and achieve a homogeneous descaling process.Hot rolling is a highly efficient steel processing method involving the heating and subsequent rolling of semi-finished cast products within mills; however, heating results in the formation of an undesirable, inhomogeneous oxide layer on the surface. Removal of this layer, known as scales, prior to rolling is essential to prevent scales from being rolled into the surface. The scales are removed in the descaler. Most descalers use multiple high-pressure hydraulic descaling nozzles with overlapping sprays. This setting can cause excessive cooling in the overlap area, uneven descaling of the surface, and the presence of residual scales. It can also result in uneven cooling at the finishing line. This study illustrates a typical nozzle configuration commonly used in industrial plants in the hydraulic descaling process and compares its results with a new configuration. The research focuses on examining the overlap area and the washout area of the sprays. The goal is to address the inhomogeneous descaling problem and propose procedures to prevent residual scales. It was shown that one of the problematic areas is the washout area, where the average thickness of the remaining scales was more than four times higher than other descaling areas. Reducing the offset angle has proven to be a good way to eliminate the washout area and achieve a homogeneous descaling process.