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.

To achieve the required mechanical properties in the heat treatment of steel, it is necessary to have an adequate cooling rate and to achieve the desired final temperature of the product. This should be achieved with one cooling unit for different product sizes. In order to provide the high variability of the cooling system, different types of nozzles are used in modern cooling systems. Designers often use simplified, inaccurate correlations to predict the heat transfer coefficient, resulting in the oversizing of the designed cooling system or failure to provide the required cooling regime. This typically results in longer commissioning times and higher manufacturing costs of the new cooling system. Accurate information about the required cooling regime and the heat transfer coefficient of the designed cooling is critical. This paper presents a design approach based on laboratory measurements. Firstly, the way to find or validate the required cooling regime is presented. The paper then focuses on nozzle selection and presents laboratory measurements that provide accurate heat transfer coefficients as a function of position and surface temperature for different cooling configurations. Numerical simulations using the measured heat transfer coefficients allow the optimum design to be found for different product sizes.

To achieve the required mechanical properties in the heat treatment of steel, it is necessary to have an adequate cooling rate and to achieve the desired final temperature of the product. This should be achieved with one cooling unit for different product sizes. In order to provide high variability of the cooling system, different types of nozzles are used in modern cooling systems. Designers often use simplified, inaccurate correlations to predict the heat transfer coefficient, resulting in oversizing of the designed cooling or failure to provide the required cooling regime. This typically results in longer commissioning times and higher manufacturing costs of the new cooling system. Accurate information about the required cooling regime and the heat transfer coefficient of the designed cooling is critical. This paper presents a design approach based on laboratory measurements. Firstly, the way to find or validate the required cooling regime is presented. The paper then focuses on nozzle selection and presents laboratory measurements that provide accurate heat transfer coefficients as a function of position and surface temperature for different cooling configurations. Numerical simulations using the measured heat transfer coefficients allow the optimum design to be found for different product sizes.