The effects of composition and carbide precipitation on temper embrittlement of 2.25 Cr-1 Mo steel: Part I. Effects of P and Sn

Yu, Jin; McMahon, C.J.

doi:10.1007/bf02660632

Cited by 152 publications

(19 citation statements)

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“…A literatura é vasta sobre o assunto de fragilidade de revenido, (21)(22)(23)(24)(25)(26)(27)(28)(29) dividida em dois fenômenos nos aços baixa liga. (21)(22)(23) O primeiro, da fragilidade de revenido clássica, presente após revenido em alta temperatura, (21)(22)(23) entre 500°C e 600°C.…”

Section: Resultados Do Presente Trabalho E Correlação Com a Fragilidaunclassified

“…O segundo mecanismo é a fragilidade de baixa temperatura, em torno de 350ºC, (21,(24)(25)(26)(27)(28)(29)(30)(31) conhecido como fragilidade da martensita revenida (temper martensite embrittlement). É não reversível e, conforme a literatura, (16,21,(28)(29)(30)(31) causado no início da precipitação da cementita, em agulhas muito finas.…”

Section: Resultados Do Presente Trabalho E Correlação Com a Fragilidaunclassified

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Aços Ferramenta Para Trabalho a Quente Com Baixo Teor De Silício: Caracterização E Aplicações

Mesquita¹,

Barbosa²,

Gonçalves³

et al. 2008

TMM

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ResumoOs aços ferramenta para trabalho a quente são empregados como matrizes para conformação de metais em alta temperatura. Recentemente, novos aços ferramenta, com menor teor de silício, têm sido utilizados, gerando substancial melhoria de desempenho das matrizes. O presente trabalho discute resultados da caracterização mecânica e microestrutural de tais aços, também apresentando algumas análises de casos. As propriedades mecânicas foram avaliadas quanto à dureza e tenacidade em impacto, em função da temperatura de revenimento. Para caracterização microestrutural, foi utilizada a técnica de microscopia eletrônica de transmissão, com o objetivo de caracterizar os carbonetos secundários, os principais responsáveis pelo endurecimento dos materiais. São observadas diferenças significativas dos carbonetos secundários em função do teor de silício, estando relacionadas, diretamente, às propriedades mecânicas avaliadas. A redução do teor de silício diminui a presença de carbonetos finos e agulhados; isto pode explicar a menor tenacidade dos aços ferramenta de alto teor de silício, sendo proposto um possível mecanismo. Desta forma, os resultados mecânicos e microestruturais justificam o aumento de desempenho desta nova classe de aços ferramenta para trabalho a quente, com menor teor de silício. Palavras-chave: Aço-ferramenta; Silício; Tenacidade; Desempenho. LOW SILICON HOT WORK TOOL STEELS: CHARACTERIZATION AND APPLICATIONS AbstractHot work tool steels are mainly used as dies for hot forming processes. New grades have been recently developed, with lower silicon content, leading to a substantial performance increase. The present paper describes the mechanical properties and microstructural characterization of such hot work steels, as well as case studies. Hardness and toughness were determined for a wide range of tempering temperatures; concerning microstructural characterization, transmission electron microcopy was used for observing secondary carbides -the main responsible for the hot strength of these steels. Important differences were observed on the secondary carbides, which are considered responsible for the differences on the mechanical properties. The reduction in silicon content reduces the amount of fine needle shaped carbides; this can explain the lower toughness of high silicon content grades and a possible mechanism is proposed. Therefore, the microstructural and mechanical results enable the understanding of the higher performance of this new class of hot work tool steels, with lower silicon content.

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Section: Resultados Do Presente Trabalho E Correlação Com a Fragilidaunclassified

Aços Ferramenta Para Trabalho a Quente Com Baixo Teor De Silício: Caracterização E Aplicações

Mesquita¹,

Barbosa²,

Gonçalves³

et al. 2008

TMM

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“…Phosphorus must then segregate to the austenite grain boundaries during the austenitizing treatment and cause intergranular fracture, as is well documented [22][23][24].…”

Section: Mechanical Propertiesmentioning

confidence: 99%

A study of the effect of precipitated austenite on the fracture of a ferritic cryogenic steel

Frear

Morris

1986

Metall Trans A

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The effect of precipitated austenite on the fracture of an Fe-8Ni-2Mn-0.1Ti steel was investigated.The study attempted to correlate microstructure, mechanical properties, and the fracture surface appearance of specimens heat treated to contain austenite or to be austenite free.The fracture surfaces were quantitatively studied using a 3D imaging technique in. the SE.M. It was found that the presence of austenite had a beneficial influence of lowering the ductile-to brittle transition temperature.Part of this decrease was found to be due to the austenite gettering deleterious elements off the grain boundaries. Specimens that contained precipitsted austenite were also found to have a smaller median facet size, when fractured in a brittle transgran.ular mode, than specimens witll 110. austenite. The smaller facet size is shown to be associated with a decrease in ductile-to brittle temperature.

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“…However, it must be underlined that two embrittlement mechanisms superimpose for these types of alloys during aging in the embrittlement temperature range, namely: (a) the gradual migration 2 However, it must be underlined that two embrittlement mechanisms superimpose for these types of alloys during aging in the embrittlement temperature range, namely: (a) the gradual migration of impurity elements such as P, Sn, As, and Sb to prior austenite grain boundaries, which results in the so-called reverse temper embrittlement [17][18][19] and (b) changes in the size and morphology of carbides for long aging times, which also cause brittleness of the steels [20,21]. Both impurity migration and carbide modification are known to be temperature-activated phenomena.…”

Section: Introductionmentioning

confidence: 99%

On the Step Cooling Treatment for the Assessment of Temper Embrittlement Susceptibility of Heavy Forgings in Superclean Steels

Roberti

Faccoli

2016

Metals

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When subjected to extended exposure to intermediate service temperatures, Cr-Mo steels, Ni-Cr steels, and 5% Ni steels can become embrittled, with an associated decrease in fracture toughness and a shift in the ductile-to-brittle transition temperature to higher temperatures. Two methods for the investigation of temper embrittlement phenomena are isothermal aging or the use of a step cooling aging treatment, which is less time consuming and is considered to be the most severe test to evaluate steel's susceptibility to this phenomenon. In the present work, the effectiveness of the step cooling treatment in the assessment of temper embrittlement in a superclean 26NiCrMoV14.5 steel for heavy section forgings has been studied. Some isothermal aging treatments in the critical temperature range have also been carried out. Results of a Charpy V impact test on not-aged and aged specimens, and observation of the fracture surfaces led to the following conclusions: the steel does not undergo temper embrittlement upon step cooling treatment or after aging at different temperatures and times in the critical temperature range; the most negative effect on the shift of the ductile-to-brittle transition curve-compared with not aged steel-has been observed after aging at 593 • C for 2 h (∆T54J = 9 • C); further aging up to 8 h produced a ∆T54J of only 1 • C. Neither step cooling nor aging at various critical temperatures gave rise to an intergranular brittle fracture; the amount of embrittling impurity elements in a superclean steel does not seem to be enough to cause embrittlement and a pure intergranular decohesion.

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The effects of composition and carbide precipitation on temper embrittlement of 2.25 Cr-1 Mo steel: Part I. Effects of P and Sn

Cited by 152 publications

References 16 publications

Aços Ferramenta Para Trabalho a Quente Com Baixo Teor De Silício: Caracterização E Aplicações

Aços Ferramenta Para Trabalho a Quente Com Baixo Teor De Silício: Caracterização E Aplicações

A study of the effect of precipitated austenite on the fracture of a ferritic cryogenic steel

On the Step Cooling Treatment for the Assessment of Temper Embrittlement Susceptibility of Heavy Forgings in Superclean Steels

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