Têmpera de superfície a laser em aço vergalhão
Data
2023-06-30
Autores
Sojo, Élder da Silva 
Orientadores
Capella, Aline Gonçalves
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Para cada aplicação onde o aço é empregado é necessária uma combinação adequada de propriedades do material. Para isso são aplicados tratamentos térmicos, como é o caso da têmpera de superfície em aços, que permite obter uma superfície com dureza superficial e resistência ao desgaste elevadas, com a permanência de um núcleo dúctil. Tais características são associadas à presença da fase martensítica, na região tratada, e de fases difusionais mais dúcteis no núcleo, como as proeutetóides e a perlita. A têmpera de superfície em aços pode ser realizada por diferentes processos, como a tecnologia do laser, por exemplo. Neste contexto, o presente trabalho visou empregar a têmpera de superfície a laser em amostras de aço 1626D, empregado como vergalhões na construção civil, avaliando os resultados microestruturais e o comportamento de dureza obtidos. Para isto, amostras normalizadas foram submetidas à têmpera de superfície a laser, considerando variação de parâmetros entre 100-300 W de potência e 150-250 mm/s de velocidade de varredura. Após os tratamentos, a superfície das amostras foram caracterizadas microestruturalmente e mecanicamente via técnicas de microscopias ópticas e eletrônica de varredura (MEV), difratometria de raios x, além de ensaios de dureza. Resultados mostram camadas tratadas com microestrutura martensítica-bainítica, com espessura variando entre 60-230 µm, sendo que para maiores intensidades do feixe resultam em maiores espessuras da camada. Já o perfil de dureza variou de 490 HV (superfície tratada) a 200 HV (base). Foi observado ainda que os maiores valores de dureza são obtidos para as menores energias de laser, consequência da microestrutura resultante. Conclui-se que a têmpera de superfície a laser é uma alternativa ao processamento térmico já empregado na empresa Gerdau que, a partir do controle de parâmetros de processo pode resultar em superfícies de aço com microestrutura desejável e que possam atender os requisitos mecânicos do produto fabricado.
For each application where steel is employed, an appropriate combination of material properties is required. For this purpose, heat treatments are applied, such as surface tempering in steels, which allows for obtaining a surface with high surface hardness and high wear resistance, with the permanence of a ductile core. Such characteristics are associated with the presence of the martensitic phase, in the treated region, and more ductile diffusional phases in the core, such as proeutectoid and pearlite. Surface hardening of steels can be performed using different processes, such as laser technology, for example. In this context, the present work aimed to use laser surface tempering on a 1626D steel sample, used as rebar in civil construction, evaluating the microstructural results and the hardness behavior obtained. For this, the normalized samples were maintained at the laser surface temperature, considering the variation of parameters between 100-300 W of power and 150-250 mm/s of scanning speed. After treatment, the surface of the samples was observed microstructurally and mechanically using optical and scanning electron microscopy (SEM), x-ray diffraction, and hardness tests. The results show treated layers with martensitic-bainitic microstructure, with thicknesses ranging from 60-230 µm, with higher beam intensities resulting in greater layer thickness. The hardness profile ranges from 490 HV (treated surface) to 200 HV (core). It was also observed that the highest hardness values were obtained for the lowest laser energies, as a consequence of the resulting microstructure. It is concluded that laser surface hardening is an alternative to thermal processing already used at Gerdau which, through the control of process parameters, can result in steel surfaces with a desirable microstructure and which can reach the mechanical requirements of the manufactured product.
For each application where steel is employed, an appropriate combination of material properties is required. For this purpose, heat treatments are applied, such as surface tempering in steels, which allows for obtaining a surface with high surface hardness and high wear resistance, with the permanence of a ductile core. Such characteristics are associated with the presence of the martensitic phase, in the treated region, and more ductile diffusional phases in the core, such as proeutectoid and pearlite. Surface hardening of steels can be performed using different processes, such as laser technology, for example. In this context, the present work aimed to use laser surface tempering on a 1626D steel sample, used as rebar in civil construction, evaluating the microstructural results and the hardness behavior obtained. For this, the normalized samples were maintained at the laser surface temperature, considering the variation of parameters between 100-300 W of power and 150-250 mm/s of scanning speed. After treatment, the surface of the samples was observed microstructurally and mechanically using optical and scanning electron microscopy (SEM), x-ray diffraction, and hardness tests. The results show treated layers with martensitic-bainitic microstructure, with thicknesses ranging from 60-230 µm, with higher beam intensities resulting in greater layer thickness. The hardness profile ranges from 490 HV (treated surface) to 200 HV (core). It was also observed that the highest hardness values were obtained for the lowest laser energies, as a consequence of the resulting microstructure. It is concluded that laser surface hardening is an alternative to thermal processing already used at Gerdau which, through the control of process parameters, can result in steel surfaces with a desirable microstructure and which can reach the mechanical requirements of the manufactured product.