ESTUDO DO ENVELHECIMENTO DINÂMICO EM UM AÇO Nb-Mn-cr-mo
DYNAMIC STRAIN AGING STUDY IN A Nb-Mn-Cr-Mo STEEL
Castro, Cynthia Serra B.; Gonzalez, Berenice Mendonça; Barbosa, Ronaldo
http://dx.doi.org/10.4322/tmm.00502011
Tecnol. Metal. Mater., vol.5, n2, p.121-125, 2008
Resumo
Neste projeto foi estudada a susceptibilidade ao envelhecimento dinâmico do aço resistente ao fogo e do mecanismo responsável pelo processo. Esta susceptibilidade foi determinada pela variação das propriedades mecânicas em tração com a temperatura e a taxa de deformação. Os testes foram feitos para temperaturas (T) variando entre 25°C e 600ºC e para as seguintes taxas de deformação (•ε): 10–1, 10–2 e 10–3s–1. As energias de ativação aparentes associadas ao início do serrilhado nas curvas tensão-deformação e ao máximo na variação do limite de resistência, com a temperatura foram calculadas pela relação entre os valores de •ε e de T para os quais esses efeitos foram observados. O aço estudado apresentou manifestações típicas relacionadas ao DSA (Dynamic Strain Aging), como a presença de platô e de máximos na variação do limite de escoamento, σe, e do limite de resistência, σr, com T, e a presença de mínimos na variação do alongamento com T, bem como efeito PLC (Portevin-LeChatelier) para certas combinações de •ε e T. Os resultados indicam que o envelhecimento dinâmico do aço considerado, provavelmente associado à interação dinâmica entre deslocações e dipolos C-elemento de liga, é um importante fator na manutenção da resistência mecânica a alta temperatura.
Palavras-chave
Envelhecimento dinâmico, Aço resistente ao fogo, Aço estrutural
Abstract
The dynamic strain aging susceptibility of the fire resistant steel was studied and the mechanism responsible for this strengthening process were determined by mean of tensile tests performed at different temperatures and strain rates. The tests were done in temperatures between 25°C and 600ºC and strain rates of 10–1, 10–2 e 10–3s–1. The values of the activation energies related to the appearance of the Portevin-LeChatelier effect and to maxima on the tensile strength versus temperature curves were determined by the relation between strain rate and the temperature. Typical features of DSA was observed, such as the presence of plateau, maximum in yield strength, ultimate tensile strength and a minimum elongation versus temperature curves. It was also observed the serrated flow in the stress-strain curves (the Portevin-LeChatelier – PLC effect), for some conditions of strain rates and temperatures. The results indicate also that dynamic strain aging of the fire steel is probably associated to the dynamic interaction between dislocations and interstitials-substitutional dipole. This strengthening mechanism is an important contribution to the fire steel mechanical properties in high temperature.
Keywords
Dynamic strain aging, Fire resistant steel, Structural steel.
Referências
1 LESLIE, W. C. The physical metallurgy of steels. Tokyo: McGraw-Hill, 1982.
2 GUNDUZ, S. Dynamic strain aging effects in niobium mycroalloyed steel. Ironmaking and Steelmaking, v. 29, n. 5, p. 341-56, 2002.
3 GUNDUZ, S. COCHRANE, R.C. Effect of dynamic strain aging on mechanical properties of vanadium microalloyed steel. Materials Science and Technology, v. 19, n. 4, p.422-8, Apr. 2003.
4 KLUEH, R.L. Interaction solid-solution hardening in 2,25C-1Mo steel. Materials Science and Engineering, v. 35, n. 35, p. 239-53, Jan. 1978.
5 SHA, W.; KELLY, F.S.; BROWNE, P.; BLACKMORE, S.P.O.; Microstructure and properties of Nippon fire resistant steels. Journal of Materials Engineering and Performance, v. 8, n. 5, p. 606-612, Oct. 2002.
6 SHA, W.; KELLY, F.S. Atom probe field ion microscopy study of commercial and experimental structural steels with fire resistant microstructures. Materials Science and Technology, v. 20, n. 4, p. 449-57, Apr. 2004.
7 KEH, A.S; NAKADAH, Y; LESLIE, W.C. Dislocation dynamics, In: ROSENFIELD, A.R.; HAHN, G.T.; BEMENT JR., A.L.; JAFFEE, R.I. (editors). Dislocation Dynamics. Nova York: McGraw Hill, 1968. p. 81-7.
8 KARIMI TAHERI, A; MACCAGNO, T.M; JONAS, J.J. Dynamic strain aging and the wire drawing of low carbon steel rods. ISIJ International. v. 35, n. 12, p. 1532-40, June 1995.
9 GONZALEZ, B.M.; MARCHI, L.A.; FONSECA, E.J.; MODENESI, P.J.; BUONO, V.T.L. Measurement of dynamic strain aging in perlitic steels by tensile test. ISIJ International, v. 43, n. 3, p. 428-32, Mar. 2003.
10 ROESH, L. Developments in the drawing of metals. The Metals Society International Conference, v. 10, n. 4, p. 210-8, May 1983.
11 TSUZAKI, K.; MATSUZAKI, Y.; MAKI, T.; TAMURA, I. Fatigue deformation accompanying dynamic strain aging in a perlitic eutectoid steel. Materials Science Engineering, v. A142, n. 1, p. 63-70, Ago. 1991.
12 ESPÍNDOLA, M.; WEIDIG, C.; RODRIGUES, P.C.M.; ANDRADE, M.S.; GONZALEZ, B.M. Dynamic strain aging in low carbon steel rods. Wire Journal International, v. 28, n. 1, p. 82-5, Jan. 1995.
2 GUNDUZ, S. Dynamic strain aging effects in niobium mycroalloyed steel. Ironmaking and Steelmaking, v. 29, n. 5, p. 341-56, 2002.
3 GUNDUZ, S. COCHRANE, R.C. Effect of dynamic strain aging on mechanical properties of vanadium microalloyed steel. Materials Science and Technology, v. 19, n. 4, p.422-8, Apr. 2003.
4 KLUEH, R.L. Interaction solid-solution hardening in 2,25C-1Mo steel. Materials Science and Engineering, v. 35, n. 35, p. 239-53, Jan. 1978.
5 SHA, W.; KELLY, F.S.; BROWNE, P.; BLACKMORE, S.P.O.; Microstructure and properties of Nippon fire resistant steels. Journal of Materials Engineering and Performance, v. 8, n. 5, p. 606-612, Oct. 2002.
6 SHA, W.; KELLY, F.S. Atom probe field ion microscopy study of commercial and experimental structural steels with fire resistant microstructures. Materials Science and Technology, v. 20, n. 4, p. 449-57, Apr. 2004.
7 KEH, A.S; NAKADAH, Y; LESLIE, W.C. Dislocation dynamics, In: ROSENFIELD, A.R.; HAHN, G.T.; BEMENT JR., A.L.; JAFFEE, R.I. (editors). Dislocation Dynamics. Nova York: McGraw Hill, 1968. p. 81-7.
8 KARIMI TAHERI, A; MACCAGNO, T.M; JONAS, J.J. Dynamic strain aging and the wire drawing of low carbon steel rods. ISIJ International. v. 35, n. 12, p. 1532-40, June 1995.
9 GONZALEZ, B.M.; MARCHI, L.A.; FONSECA, E.J.; MODENESI, P.J.; BUONO, V.T.L. Measurement of dynamic strain aging in perlitic steels by tensile test. ISIJ International, v. 43, n. 3, p. 428-32, Mar. 2003.
10 ROESH, L. Developments in the drawing of metals. The Metals Society International Conference, v. 10, n. 4, p. 210-8, May 1983.
11 TSUZAKI, K.; MATSUZAKI, Y.; MAKI, T.; TAMURA, I. Fatigue deformation accompanying dynamic strain aging in a perlitic eutectoid steel. Materials Science Engineering, v. A142, n. 1, p. 63-70, Ago. 1991.
12 ESPÍNDOLA, M.; WEIDIG, C.; RODRIGUES, P.C.M.; ANDRADE, M.S.; GONZALEZ, B.M. Dynamic strain aging in low carbon steel rods. Wire Journal International, v. 28, n. 1, p. 82-5, Jan. 1995.
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