Navegando por Autor "Souza, Altair Lúcio de"

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Os benefícios da utilização da estratégia tapering na redução das cargas de laminação nas pontas da tira em laminadores steckel.
(2016) Lino, João Júnio Pereira; Borges, Jacson Morais; Souza, Altair Lúcio de; Frenn, John Hanna; Pereira, Maurício Martins; Schuwarten Júnior, Willy; Faria, Geraldo Lúcio de
A laminação de tiras a quente com laminadores Steckel tem como característica um perfil de temperatura mais baixa nas pontas sendo este um dos motivos que geram cargas de laminação muito mais altas nesta região. A carga de laminação elevada tem como consequência no processo a geração de desvios de planicidade e o alto risco de rompimento do material nos passes finais de laminação. Este trabalho tem como objetivo demonstrar os benefícios da utilização da estratégia de Tapering para a laminação de tiras de espessura fina em laminador Steckel que consiste na aplicação de reduções maiores nas pontas da tira em comparação com o corpo. Foi feita a comparação das cargas de laminação do material laminado e o acompanhamento dos resultados de planicidade obtidos antes e depois da implantação desta função. Ao fim do trabalho verificamos que a estratégia de Tapering é essencial para o processamento de materiais finos com laminadores Steckel.
Production of a non-stoichiometric Nb-Ti HSLA steel by thermomechanical processing on a Steckel mill.
(2023) Martins, Cleiton Arlindo; Faria, Geraldo Lúcio de; Mayo, Unai; Isasti, Nerea; Uranga, Pello; Rodríguez Ibabe, Jose Maria; Souza, Altair Lúcio de; Cohn, Jorge Adam Cleto; Rebellato, Marcelo Arantes; Gorni, Antônio Augusto
Obtaining high levels of mechanical properties in steels is directly linked to the use of special mechanical forming processes and the addition of alloying elements during their manufacture. This work presents a study of a hot-rolled steel strip produced to achieve a yield strength above 600 MPa, using a niobium microalloyed HSLA steel with non-stoichiometric titanium (titanium/nitrogen ratio above 3.42), and rolled on a Steckel mill. A major challenge imposed by rolling on a Steckel mill is that the process is reversible, resulting in long interpass times, which facilitates recrystallization and grain growth kinetics. Rolling parameters whose aim was to obtain the maximum degree of microstructural refinement were determined by considering microstructural evolution simulations performed in MicroSim-SM® software and studying the alloy through physical simulations to obtain critical temperatures and determine the CCT diagram. Four ranges of coiling temperatures (525–550 ◦C/550–600 ◦C/600–650 ◦ C/650–700 ◦C) were applied to evaluate their impact on microstructure, precipitation hardening, and mechanical properties, with the results showing a very refined microstructure, with the highest yield strength observed at coiling temperatures of 600–650 ◦C. This scenario is explained by the maximum precipitation of titanium carbide observed at this temperature, leading to a greater contribution of precipitation hardening provided by the presence of a large volume of small-sized precipitates. This paper shows that the combination of optimized industrial parameters based on metallurgical mechanisms and advanced modeling techniques opens up new possibilities for a robust production of high-strength steels using a Steckel mill. The microstructural base for a stable production of high-strength hot-rolled products relies on a consistent grain size refinement provided mainly by the effect of Nb together with appropriate rolling parameters, and the fine precipitation of TiC during cooling provides the additional increase to reach the requested yield strength values.
The use of dilatometry aiming to evaluate the metallurgical aspect of coil slump in a hot‐rolled medium carbon steel.
(2022) Fernandes, João Lucas Ribeiro e; Souza, Altair Lúcio de; Faria, Geraldo Lúcio de
The hot coil slump is a recurrent problem in the manufacturing process of medium and high equivalent carbon steel plates. Even with the success of the hot rolling procedure, the posterior coil slump can occur, representing operational disorder and manufacturing cost increase. Some authors point that the coil slump phenomenon can occur due to metallurgical, mechani- cal and geometric aspects. Preview studies already investigated several possible mechanical and geometric contributions. However, there are few available experimental data about the metallurgical one, that is, the efect of late austenite decom- position during, or after the coiling stage. In this context, this paper presents a study about the application of dilatometry technique aiming to evaluate the infuence of late phase transformations as a relevant cause of a medium carbon steel coil slump. Heating cycles that simulated, with good agreement, some possible plate cooling conditions and isothermal coiling procedures were performed in standardized specimens using a quenching dilatometer. Diferent combinations of cooling rates and coiling temperatures were evaluated. It was possible to conclude that the dilatometry technique application is viable and efcient to evaluate the metallurgical contribution to the coil slump phenomenon. For the studied steel, it was possible to suggest that a decrease of the cooling rate, in association with a slight decrease of coiling temperature, can signifcantly suppress the metallurgical infuence on the coil slump occurrences.