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Master's Dissertation
DOI
10.11606/D.18.2014.tde-02102014-155652
Document
Author
Full name
Robson Silva Bussoloti
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2014
Supervisor
Committee
Canale, Lauralice de Campos Franceschini (President)
Ferrarini, Cleyton Fernandes
Silva Junior, Wilson Carlos da
Title in Portuguese
Ferrita delta em parafusos tratados termicamente: caracterização e consequências
Keywords in Portuguese
Desfosfatização
Fadiga
Ferrita delta
Fosfato
Fragilização
Parafuso
Abstract in Portuguese
Nos processos de fabricação de parafusos, a fosfatização é necessária para servir de ancoradouro aos lubrificantes, e outros redutores de atrito, por facilitarem o processo de deformação a frio. No entanto, antes do início do tratamento térmico de têmpera e revenimento, é importante que o banho de desfosfatização seja eficiente para impedir que, durante a austenitização, o fósforo residual presente na superfície do parafuso se difunda para o aço e forme uma fase frágil, rica em fósforo, denominada ferrita delta (δ). Acredita-se que esta fase, uma vez presente, promove não apenas a diminuição da vida em fadiga mas, também, a fragilização do parafuso. Neste sentido, o presente trabalho objetivou comprovar a influência negativa dessa fase, devidamente caracterizada por MEV, EDS e análise fractográfica, quanto ao desempenho à fadiga, através da comparação das curvas S-N em corpos de prova com e sem ferrita δ. Os resultados obtidos claramente evidenciaram que a presença da fase δ promoveu uma redução de até 40% na vida em fadiga.
Title in English
Delta ferrite in heat treated bolts: characterization and consequences
Keywords in English
Bolts
Delta ferrite
Embrittlement
Fatigue
Phosphate
Phosphorus
Abstract in English
In the process of manufacturing bolts, a coat phosphating is required to serve as anchorage for lubricants and other friction-reducer, facilitating the cold forming process. However, before the beginning heat treatment of quenching and tempering, it is important that the alkaline bath for cleaning be efficient in order to prevent that during austenitizing, the residual phosphorus spread on the steel surface and forms a brittle phase, rich in phosphorus, called delta ferrite (δ). In the presence of this phase, is credited with a decrease in fatigue life of the bolt and embrittlement. The intention in this work was to show the negative influence of this phase on fatigue performance, comparing the S-N curves for specimens with and without ferrite δ. Trials have shown a reduction of up to 40% in life fatigue. The ferrite δ was characterized by SEM, EDS and also performed fractographic analysis.
 
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ME_Corrigida.pdf (3.64 Mbytes)
Publishing Date
2014-10-14
 
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