Estudo do envelhecimento após deformação em um aço complex phase
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Data
2011-07-22
Autores
Lombardo, Sandro [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Os aços multifásicos Complex Phase são aços desenvolvidos para a indústria automobilística que ainda estão sendo utilizados de uma forma bem tímida. Estes aços podem ser usados na parte estrutural das portas, vigas, pilares B, perfis, reforço de estruturas, pára-choques, tetos, capôs e partes do chassi dos carros. O foco deste trabalho foi estudar o comportamento mecânico destes aços após deformação plástica, em diferentes temperaturas e tempos de envelhecimento. O método utilizado é semelhante ao aplicado atualmente pelas indústrias automobilísticas, durante o processo de pintura, chamado Endurecimento ao Forno (efeito Bake Hardening). O efeito visa melhorar a resistência mecânica e manter a conformabilidade, o baixo peso da estrutura e a resistência ao impacto, característicos deste tipo de aço, possibilitando a redução de espessura/peso sem perda da resistência à formação de mossa (dent resistence). Os parâmetros de temperatura e tempo utilizados foram baseados nos processos de envelhecimento conhecidos pelo mercado para os aços Dual Phase e TRIP (Plasticidade Induzida por Transformação) como base de informações, pois para os aços Complex Phase este processo é pouco estudado. Os ensaios foram executados no material como fornecido, e os parâmetros utilizados foram pré-deformação de 2% ± 1, temperaturas de envelhecimento variando de 25 à 180ºC e tempos que variaram de 300 à 9.000.000 segundos. Foram realizadas análises microestruturais e mecânicas dos corpos-de-prova a fim de definir a melhor condição de envelhecimento para o aço Complex Phase, através de ensaios de tração, dureza, microscopia óptica e microscopia eletrônica de varredura observou-se o aumento da resistência para cerca de 890 MPa, sem significativa perda da ductibilidade. Avaliou-se, também, a lei cinética de envelhecimento visando a caracterização do fenômeno...
The Complex Phase steels are developed for the automotive industry although are being timidly used. These steels could be used in the structural part such as doors, beams, B columns, profiles, stringers, bumpers, roofs, hoods and other body parts. The focus of this work was to study the mechanical behavior of these steels after plastic deformation at different temperatures and aging times. The used method is similar to that currently applied by the automobile during painting, called the Bake Hardening. The aim is to improve the mechanical strength, maintaining the formability, low weight of the structure and impact strength, typical of this kind of steel, allowing the reduction in thickness / weight loss without losing dent resistance. The temperature and time parameters used were based on the aging processes known for Dual Phase and TRIP (Transformation Induced Plasticity) steels since information for the Complex Phase is not well reported. The tests were performed on the material as supplied, and the parameters used were pre-strain of 2% ± 1, aging temperatures ranging from 25 to 180 ºC for periods ranging from 300 to 9.000.000 seconds. Microstructure and mechanical properties of material were analyzed to define the best condition for the aging of Complex Phase Steel through tensile and hardness tests, optical microscopy and scanning electron microscopy was observed a increased resistance around 890 MPa without a significant loss of ductility. It was also studied the aging kinetics, aiming to characterize the phenomenon by varying the value Bake Hardening with time and temperature for pre-strain of 2% in tension. We can conclude that the multiphase steel Complex Phase presents the best condition for the Bake Hardening effect at 180 ºC in accordance with the standards and the literature, this condition improves their resistance, keeps their tenacity, and suggests the best condition ... (Complete abstract click electronic access below)
The Complex Phase steels are developed for the automotive industry although are being timidly used. These steels could be used in the structural part such as doors, beams, B columns, profiles, stringers, bumpers, roofs, hoods and other body parts. The focus of this work was to study the mechanical behavior of these steels after plastic deformation at different temperatures and aging times. The used method is similar to that currently applied by the automobile during painting, called the Bake Hardening. The aim is to improve the mechanical strength, maintaining the formability, low weight of the structure and impact strength, typical of this kind of steel, allowing the reduction in thickness / weight loss without losing dent resistance. The temperature and time parameters used were based on the aging processes known for Dual Phase and TRIP (Transformation Induced Plasticity) steels since information for the Complex Phase is not well reported. The tests were performed on the material as supplied, and the parameters used were pre-strain of 2% ± 1, aging temperatures ranging from 25 to 180 ºC for periods ranging from 300 to 9.000.000 seconds. Microstructure and mechanical properties of material were analyzed to define the best condition for the aging of Complex Phase Steel through tensile and hardness tests, optical microscopy and scanning electron microscopy was observed a increased resistance around 890 MPa without a significant loss of ductility. It was also studied the aging kinetics, aiming to characterize the phenomenon by varying the value Bake Hardening with time and temperature for pre-strain of 2% in tension. We can conclude that the multiphase steel Complex Phase presents the best condition for the Bake Hardening effect at 180 ºC in accordance with the standards and the literature, this condition improves their resistance, keeps their tenacity, and suggests the best condition ... (Complete abstract click electronic access below)
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Ação Católica Operária (Brasil), Steel
Como citar
LOMBARDO, Sandro. Estudo do envelhecimento após deformação em um aço complex phase. 2011. 145 f. Dissertação (mestrado) - Universidade Estadual Paulista, Faculdade de Engenharia de Guaratinguetá, 2011.