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Estudo da reversão martensítica em um aço inoxidável austenítico 201LN submetido à laminação criogênica
(Universidade Federal de São Carlos, 2024-06-09) Oliveira, Paulo Otavio Nascimento Ferreira de; Magalhães, Danielle Cristina Camilo; https://lattes.cnpq.br/5486724956564584
With the progress of society, the demand for new materials that meet human needs is becoming increasingly greater. In this context, austenitic stainless steels (ASS) have attracted significant interest, primarily due to their excellent corrosion resistance. The 300 series ASS are the most commonly used among these steels. However, the microstructural refinement of 201LN steel, achieved through cryogenic deformation followed by heat treatment, enhances its mechanical properties, making it a cost-effective alternative to the 300 series, as nickel (Ni) is replaced by nitrogen (N) and manganese (Mn). The high susceptibility of ASS to the effect of transformation-induced plasticity (TRIP) when subjected to deformation justifies this observed improvement since 201LN ASS is more prone to this phenomenon than 304, due to its lower stacking fault energy (SFE). As a result, the transformation from the austenite phase to martensite (γ → α’) is facilitated. Thus, the goal was to induce the γ → α’ transformation through cryogenic rolling, in order to evaluate the effects of this transformation before and after the α’ → γ reversion. For this purpose, the sample was solution-treated, deformed at cryogenic temperature to thickness reductions of 10, 20, and 30%, and subsequently annealed for 30 minutes at 400, 500, 600, 700, and 800 ºC. To analyze the evolution of deformation-induced martensite (DIM) and its subsequent reversion, the following techniques were applied: metallography, X-ray diffraction (XRD), Vickers hardness, and Electron Backscatter Diffraction (EBSD). In summary, the results demonstrated that the greater the plastic deformation at cryogenic temperature, the higher the volume fraction of DIM in 201LN ASS, and consequently, the hardness increases. XRD data indicated the presence of approximately 43% α' after 30% cryogenic deformation, while the EBSD technique showed a volume fraction of around 50%. After annealing for 30 minutes at 800 ºC, the resulting grains exhibited a mean size reduced by almost 10 times, which resulted in an increase of about 2 times in hardness compared to the solution-treated sample.
Análise do setor metalúrgico de capital aberto no Brasil: indicadores de crescimento, empregabilidade e sustentabilidade
(Universidade Federal de São Carlos, 2024-06-09) Maganha, Matheus Christovam; Magalhães, Danielle Cristina Camilo; https://lattes.cnpq.br/5486724956564584
The study of growth, employability, and sustainability indicators allows for predicting the activity levels of these companies over the next five years. Analyzing the sector's growth indicators is essential to understanding the economic dynamics, financial health of the companies, and their expansion prospects. Beyond financial aspects, sector analysis must also consider employability and sustainability. Thus, the general objective of this study was to analyze the publicly traded metallurgical sector in Brazil, focusing on four companies: Gerdau, Vale, Usiminas, and Aura Minerals. Additionally, it aimed to evaluate these companies' growth, employability, and sustainability indicators, understanding how they contribute to the country's socioeconomic and environmental development, as well as identifying the presence of engineers in their operations and the correlation between the improvement of indicators and the total number of active engineers, with analyses over a ten-year period. For the development of this study, reports and data from investment-specialized companies were used, as well as interviews with human resources departments and sustainability reports. Quantitative and qualitative forecasting methods were applied to identify trends and possible future scenarios, following best practices recommended by PwC (PricewaterhouseCoopers International Limited). The results indicated that all the companies studied showed consistent growth, with an average increase of 4.75% in gross revenue. Projections for the next five years suggest a continued increase in investments in sustainable technologies and energy efficiency, resulting in an average reduction of 3.7% in CO2 emissions, as well as a 1.3% average reduction in energy consumption. The employability analysis indicated an average increase of 16% in the number of direct jobs in the sector, with engineers comprising 5% of the total workforce, directly correlating with improvements in efficiency and sustainability indicators.