The Study on Annealing Temperature and Rolling Speed Effects in Relation with Microstructure, Mechanical Properties and Surface Quality of Hot Rolled S450J0 Steel

Abstract

This study investigates the impact of annealing temperature and rolling speed on the microstructure, mechanical properties and surface quality of hot-rolled S450J0 structural steel, focusing on the production of HP 305x305x223 kg/m H-beams. Various annealing temperatures and rolling speeds were utilized to determine their effects on the product quality. Results indicate that annealing temperature significantly influences mechanical properties, with higher temperatures increasing yield and tensile strengths but potentially reducing elongation and impact toughness. In contrast, variation in rolling speed has minimal impact on mechanical properties due to the consistent finishing temperatures. Microstructure analysis reveals that higher annealing temperatures lead to smaller grain sizes, while lower temperatures result in clear ferrite grain alignment. Surface defects on steel surfaces, including crack patterns, are shaped by both annealing temperature and rolling speed. SEM analysis confirms the depth and characteristics of surface cracks, aligning with optical microscope observations. Overall, optimizing annealing temperature and rolling speed is essential for minimizing surface defects and enhancing product quality during the hot rolling process of H-beams.