Estudo da taxa de aquecimento de um forno mufla: determinação experimental, modelagem matemática e aplicação no tratamento térmico do aço aisi 4340 /

Abstract

The precise determination of the heating curves of furnaces used in heat treatments is essential to ensure the achievement of the desired mechanical and magnetic properties in steels. In the case of the quenching heat treatment of AISI 4340 steel, such thermal control is crucial for promoting the proper formation of martensite, which in turn enhances its mechanical and magnetic characteristics—key requirements for high-strength applications. In this context, the present study aimed to investigate the heating curve of a muffle furnace through experimental measurements, mathematical modeling, and its application in the quenching process of AISI 4340 steel. Two different control settings (ptol 10 and ptol 20) were evaluated during heating up to the austenitizing temperature, and their influence on the final properties of the material was analyzed. Experimental measurements of heating curves were conducted under both loaded and unloaded conditions, followed by nonlinear regression modeling using various mathematical approaches. Among the tested models, the Gompertz model presented the best fit, with a coefficient of determination (R²) of 0.9995, indicating excellent representation of the furnace's thermal behavior. Results showed that the ptol 10 setting reached the austenitizing temperature (870 °C) in a shorter time (85 minutes) compared to ptol 20 (90 minutes), indicating greater thermal efficiency. Microstructural analyses revealed variations in the fractions of martensite and retained austenite among the samples, directly affecting the measured hardness values. Additionally, sample CP3 exhibited an average magnetization of 721.93 Gauss with a standard deviation of 0.486, indicating higher resistance to magnetization compared to samples CP1 and CP2. Overall, the ptol 10 setting provided a more efficient heat treatment, with reduced processing time and satisfactory microstructural and magnetic results.