INFLUENCE OF COIL COOLING CONDITIONS ON THE MICROSTRUCTURE AND PROPERTIES OF HOT-ROLLED STRIP STEEL

Аннотация

Improving the quality of hot-rolled sheet steel is one of the key challenges in modern metallurgical production, since cooling conditions at different stages of the technological process have a significant influence on the formation of the microstructure and the mechanical properties of the metal. The aim of this study was to establish the patterns of structural transformations in low-carbon steel under various cooling regimes and to determine the optimal thermomechanical processing parameters for improving the quality of hot-rolled products.

The research was carried out on samples of hot-rolled St3sp steel using optical metallography, scanning electron microscopy, and energy-dispersive microanalysis. The influence of cooling regimes on the formation of the metal microstructure was evaluated, and the features of structural changes occurring during coil cooling after coiling were investigated.

It was established that the temperature–time parameters of cooling have a decisive effect on grain size, the morphology of structural constituents, and the nature of phase transformations in steel. It was shown that the selection of an optimal cooling regime ensures the formation of a more homogeneous fine-grained microstructure and reduces the likelihood of unfavorable structural constituents. It was found that changes in the properties of the metal during coil cooling are more closely associated with cementite spheroidization processes than with ferrite grain growth. A relationship was established between the degree of cementite spheroidization and changes in the mechanical properties of hot-rolled steel.

The obtained results can be used to improve cooling practices on hot strip mills in order to enhance the quality of sheet products and ensure the stability of their service performance characteristics.