SOLDAGEM A PONTO POR FRICÇÃO E MISTURA MECÂNICA DE UM AÇO TRIP: CARACTERIZAÇÃO MICROESTRUTURAL
FRICTION STIR SPOT WELDING OF A TRIP STEEL: MICROSTRUCTURAL CHARACTERIZATION
Mazzaferro, Cíntia Cristiane P.; Ramos, Fabiano Dornelles; Mazzaferro, José Antônio E.; Rosendo, Tonilson; Tier, Marco Antônio D.; Silva, Antônio Mônaco da; Santos, Jorge Fernandez dos; Strohaecker, Telmo Roberto
http://dx.doi.org/10.4322/tmm.00603003
Tecnol. Metal. Mater. Min., vol.6, n3, p.136-141, 2013
Resumo
Este trabalho tem como objetivo investigar a influência da velocidade de rotação (1.600 RPM e 2.400 RPM) no desenvolvimento microestrutural de um aço TRIP soldado a ponto por fricção e mistura mecânica. Após a execução das soldas, devido aos ciclos térmicos e deformações impostas pelo processo, são observadas três diferentes zonas nas juntas: a zona de mistura (ZM), a zona termomecanicamente afetada (ZTMA), e a zona termicamente afetada (ZTA). O aumento da velocidade de rotação causou um aumento na quantidade de ferrita alotriomorfa formada na ZM, assim como redução na quantidade e tamanho de bainita coalescida e martensita. Na ZTMA a microestrutura é constituída por ferrita, austenita, bainita coalescida e martensita. Enquanto que na ZTA1 a microestrutura é composta por ferrita e austenita retida em todas as velocidades usadas, na ZTA2 há maior transformação da austenita em bainita com o aumento da velocidade de rotação.
Palavras-chave
Microestrutura, Aço TRIP, Soldagem a ponto, Soldagem por fricção
Abstract
The aim of this work is to verify the influence of the rotational speed (1600 and 2400 RPM) in the microstructural development of a friction stir spot welded TRIP steel. After the welding, due to the thermal cycles and deformations imposed by the process, three different zones are observed in the joints: the stir zone (SZ), the thermomecanically affected zone (TMAZ), and the heat affected zone (HAZ). The increase in the rotational speed caused an increase in the amount of allotriomorphic ferrite formed in the SZ, and a decrease in the amount and width of the coalesced bainite and martensite. In the TMAZ, the microstructure is composed by ferrite, austenite, coalesced bainite and martensite. While in the HAZ1 the microstructure is constituted by ferrite and retained austenite in all rotational speeds employed, in the HAZ2 there is an increase in the transformation of austenite into bainite by increasing the rotational speed.
Keywords
Microstructure, TRIP Steel, Spot welding, Friction welding
Referências
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8 GIRAULT, E., et al. Metallographic methods for revealing the multiphase microstructure of TRIP-assisted steels. Materials Characterization, v. 40, n. 2, p. 111-8, Feb. 1998.
9 JACQUES, P.J. et al. The developments of cold-rolled TRIP-assisted multiphase steels. Al-alloyed TRIP-assisted multiphase steels. ISIJ International, v. 41, n. 9, p. 1068-74, 2001.
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11 BHADESHIA, H.K.D.H. Possible effects of stress on steel weld microstructures. In: CERJAK, H., ed. Mathematical modelling of weld phenomena. London: Institute of Materials, 1995. p. 71-118.
12 HANLON, D.N.; SIETSMA, J.; VAN DER ZWAAG, S. The effect of plastic deformation of austenite on the kinetics of subsequent ferrite formation. ISIJ International, v. 41, n. 9, p. 1028-36. 2001.
13 RYU, H. B.; SPEER, J.G.; WISE, J.P. Effect of thermomechanical processing on the retained austenite content in a Si-Mn transformation induced plasticity steel. Metallurgical and Materials Transactions A, v. 33, n. 9, p. 2811-6, Sep. 2002.
14 HONG, S.C. et al. Effect of undercooling of austenite on strain induced ferrite transformation behavior. ISIJ International, v. 43, n. 3, p. 394-9, 2003.
15 LIU, X.; SOLBERG, J.K.; GJENGEDAL, R. Measurement of austenite-to-ferrite transformation temperature after multi-pass deformation of steels. Materials Science and Engineering A, v. 194, n. 1, p. 15-8, Apr. 1995.
16 WANG, J.; VAN DER ZWAAG, S. Stabilization mechanisms of retained austenite in transformation-induced plasticity steel. Metallurgical and Materials Transactions A, v. 32, n. 6, p. 1527-39, June 2001.
17 JIMENEZ-MELERO, E. et al. Martensitic transformation of individual grains in low-alloyed TRIP steels. Scripta Materialia, v. 56, n. 5, p. 421-4, 2007.
18 FURNÉMONT, Q. et al. On the measurement of nanohardness of the constitutive phases of TRIP-assisted multiphase steels. Materials Science and Engineering A, v. 328, n.1-2, p. 26-32, May 2002.
2 MATSUMURA, O.; SAKUMA, Y.; TAKECHI, H. Enhancement of elongation by retained austenite in intercritical annealed 0.4C-1.5Si-0.8Mn steel. Transactions of ISIJ, v. 27, n. 7, p. 570-9, 1987.
3 HULKA, K. The role of niobium in cold rolled TRIP steel. Materials Science Forum, v. 473-474, p. 91-102, Jan. 2005.
4 SILVA, A. M. et al. Friction spot and friction spot welding processes: a literature review. Bulletin of the National R&D Institute for Welding and Material Testing, v. 3, p. 36-44, 2007.
5 KHAN, M.I. et al. Resistance and friction stir spot welding of DP600: a comparative study. Science and Technology of Welding and Joining, v. 12, n. 2, p. 175-182, Feb. 2007.
6 FENG, Z. et al. Friction stir spot welding of advanced high-strength steels: a feasibility study. SAE SP, n. 1959, p. 85-92, 2005. (Technical paper, 2005-01-1248).
7 MAZZAFERRO, C.C.P. Soldagem a ponto por fricção e mistura mecânica de um aço TRIP 800: processo, microestrutura e propriedades. 2008. 99p.(Tese de Doutorado – Programa de Pós-Graduação em Engenharia de Minas, Metalurgia e Materiais) Universidade Federal do Rio Grande do Sul, Porto Alegre, 2008.
8 GIRAULT, E., et al. Metallographic methods for revealing the multiphase microstructure of TRIP-assisted steels. Materials Characterization, v. 40, n. 2, p. 111-8, Feb. 1998.
9 JACQUES, P.J. et al. The developments of cold-rolled TRIP-assisted multiphase steels. Al-alloyed TRIP-assisted multiphase steels. ISIJ International, v. 41, n. 9, p. 1068-74, 2001.
10 CULLITY, B.D.; STOCK, S.R. Elements of X-ray diffraction. 2. ed. Massachusetts: Addison-Wesley, 1978.
11 BHADESHIA, H.K.D.H. Possible effects of stress on steel weld microstructures. In: CERJAK, H., ed. Mathematical modelling of weld phenomena. London: Institute of Materials, 1995. p. 71-118.
12 HANLON, D.N.; SIETSMA, J.; VAN DER ZWAAG, S. The effect of plastic deformation of austenite on the kinetics of subsequent ferrite formation. ISIJ International, v. 41, n. 9, p. 1028-36. 2001.
13 RYU, H. B.; SPEER, J.G.; WISE, J.P. Effect of thermomechanical processing on the retained austenite content in a Si-Mn transformation induced plasticity steel. Metallurgical and Materials Transactions A, v. 33, n. 9, p. 2811-6, Sep. 2002.
14 HONG, S.C. et al. Effect of undercooling of austenite on strain induced ferrite transformation behavior. ISIJ International, v. 43, n. 3, p. 394-9, 2003.
15 LIU, X.; SOLBERG, J.K.; GJENGEDAL, R. Measurement of austenite-to-ferrite transformation temperature after multi-pass deformation of steels. Materials Science and Engineering A, v. 194, n. 1, p. 15-8, Apr. 1995.
16 WANG, J.; VAN DER ZWAAG, S. Stabilization mechanisms of retained austenite in transformation-induced plasticity steel. Metallurgical and Materials Transactions A, v. 32, n. 6, p. 1527-39, June 2001.
17 JIMENEZ-MELERO, E. et al. Martensitic transformation of individual grains in low-alloyed TRIP steels. Scripta Materialia, v. 56, n. 5, p. 421-4, 2007.
18 FURNÉMONT, Q. et al. On the measurement of nanohardness of the constitutive phases of TRIP-assisted multiphase steels. Materials Science and Engineering A, v. 328, n.1-2, p. 26-32, May 2002.
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