Influência da variação de resfriamento na normalização do aço Aisi 434

Abstract

AISI 4340 steel is widely used in various industries due to its excellent mechanical properties, including high strength, hardness, toughness, and wear resistance, making it extensively employed in critical components in the aerospace, automotive, and oil drilling industries. After normalization heat treatment, this steel acquires a refined pearlitic and ferritic structure, enhancing its mechanical and microstructural properties. The present work aims to study the changes in the mechanical properties, microstructural characteristics, and magnetic behavior of AISI 4340 steel subjected to normalization heat treatment under different cooling conditions. Devices for forced air cooling were designed, and heat treatments were carried out with calm air cooling and forced air cooling at airflow rates of 61 m³/h and 129 m³/h, followed by microstructural analyses, Rockwell hardness, Vickers microhardness, and magnetic tests using a Hall sensor. The results showed that the cooling devices allowed normalization with different airflow rates, resulting in the expected ferritic and pearlitic microstructures. The NF2 sample, subjected to the highest forced cooling airflow, presented the smallest grain size and the highest amount of pearlite, reflecting a refined microstructure and a slight increase in hardness. Magnetic tests indicated good homogeneity in the magnetic flux density in the forced cooling samples. The combination of mechanical, microstructural, and magnetic analyses proved essential for understanding and optimizing the behavior of AISI 4340 steel under different heat treatment conditions, highlighting the potential of forced cooling to improve its properties.