Стабілізація низькотемпературної ударної в’язкості товстих плит із конструкційних марок сталей коригуванням параметрів нормалізуючої прокатки

The article focuses on optimizing the production technology for structural steel plates with a thickness of 51-100 mm to stabilize low-temperature impact toughness. The study investigates the influence of normalizing rolling parameters, microstructural characteristics, and chemical composition on the fracture energy of steel at –20oC. Based on the analysis of automated data («Detailing rolling protocol») and Charpy impact test results, it was established that the decisive factor for forming a fine-grained structure (grain size No. 8-10) is the strict adherence to the regulation of the roughing and finishing stages of normalizing rolling, ensuring the necessary deformation forces and inter-pass pauses. It is shown that to ensure stable impact toughness (fracture energy exceeding 27 J), the total reduction in the finishing stand must be at least 15-20% with forces of 29.4-34.3 MN (3000-3500 tf) during the initial passes. It was found that a decrease in these parameters leads to the formation of an inhomogeneous structure with coarse grains, which sharply reduces cold resistance. Additionally, the qualitative influence of non-metallic inclusions and carbon content on mechanical properties was determined. Practical recommendations have been formulated to improve the technological regulations for normalizing rolling, allowing for the avoidance of costs associated with additional thermal treatment of the plates