Efeitos do revenimento realizado a baixa temperatura na resistência ao impacto em aços carbono e ligados temperados

• Ano de defesa: 2011
• Autor(a) principal: Oliveira, Bruno Ozi Silva Rosalin de
• Orientador(a): Vatavuk, Jan
• Banca de defesa: Couto, Antonio Augusto , Colósio, Marco Antonio
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Presbiteriana Mackenzie
• Programa de Pós-Graduação: Engenharia de Materiais
• Departamento: Engenharia de Materiais
• País: BR
• Palavras-chave em Português: revenimento; mecanismos de fratura; revenido; têmpera
• Palavras-chave em Inglês: tempering; fractography mechanism; temper; quenching
• Área do conhecimento CNPq: CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA
• Link de acesso: http://dspace.mackenzie.br/handle/10899/24147

This work has as main objective the determination of mechanical behavior, specially the impact resistance of martensitic structures based on carbon and on alloyed steels. The main concern is the response of these alloys when tempering at low temperatures (below 180°C). Heat treatments were performed by quenching in water and oil in order to determine the severity of the medium through testing the hardness, impact, micrographic and fractographic analysis. The SAE1045 and SAE4140 steels were also subjected to heat treatment tempering at low temperatures, 100°C, 140°C and 180°C, to verify the increase of toughness and possible changes in microstructure of these materials. It was the largest recorded hardenability of SAE4140 steel over SAE1045 steel, in agreement with the literature, through the results of hardness and micrographic analysis performed. The quenching in oil of the SAE4140 steel showed a predominantly martensitic microstructure which generated a hardness greater than SAE1045 steel showed a microstructure of martensite with islands of fine pearlite and ferrite. At all the tempering carried out for SAE1045 stel there is an increase in absorbed energy on impact with increasing temperature, and that these low-temperature tempering have significant influences on the material toughness. The tempering have higher increases of energy absorption and lateral expansion of SAE1045 steel in the conditions of quenching in water than in quenching in oil. For SAE4140 steel quenching in water (not very usual in practice) generated cracks in some specimens, since tempering in oil gave high values of absorbed energy during impact and showed no significant changes in the low-temperature tempering. It follows that for SAE1045 steel the low tempering temperature cause a significant increase in material toughness regardless of the quenching medium, however for tempering SAE4140 steel in water makes it impossible to evaluate because of the cracks generated in the coolong and quenching in oil no improvement in toughness can be observed.