OTIMIZAÇÃO DOS PARÂMETROS DE AUSTENIZAÇÃO DE UM FERRO NODULAR AUSTEMPERADO A PARTIR DA ZONA CRÍTICA
OPTIMIZATION OF AUSTENITIZING PARAMETERS OF A DUCTILE IRON AUSTEMPERED FROM THE CRITICAL ZONE
Franco, Eliana; Costa, César Edil da; Stahlschmidt, Joânesson; Guesser, Wilson Luiz
http://dx.doi.org/10.4322/tmm.00603004
Tecnol. Metal. Mater. Min., vol.6, n3, p.142-146, 2010
Resumo
O ferro fundido nodular austemperado a partir da zona crítica, denominado NAZC neste trabalho, tem se apresentado como um material emergente devido ao seu interessante conjunto de propriedades mecânicas. O principal objetivo deste trabalho é avaliar os parâmetros de austenitização para a fabricação do NAZC. Inicialmente, amostras de ferro nodular foram austenitizadas dentro da zona crítica e temperadas para avaliação da parcela de austenita (martensita na temperatura ambiente), a qual se transformaria em ausferrita no estudo posterior de austêmpera. O tratamento de austêmpera resulta em uma microestrutura constituída por ausferrita e ferrita pró-eutetóide. A partir da análise dos resultados de têmpera, foram realizados tratamentos de austêmpera e então observados os parâmetros que levam a determinadas microestruturas. Em ambos os tratamentos, as amostras foram caracterizadas por microscopia óptica e análise de imagem. Tratamentos de austêmpera realizados a uma temperatura de austenitização de 790°C e tempos de 3 h e 4 h levaram a uma microestrutura final que deve apresentar um interessante conjunto de propriedades mecânicas.
Palavras-chave
Ferro nodular austemperado, Austêmpera, Ferrita, Ausferrita
Abstract
The austempered ductile cast iron from the critical zone, named NAZC in this work, has been presented as an emerging material due to its interesting range of mechanical properties. The main objective of this study is to evaluate the austenitizing parameters for NAZC manufacturing. Initially, ductile iron specimens were austenitized within the critical zone and quenched to evaluate the amount of austenite (martensite at room temperature), which would become ausferrite later in the study of austempering. The treatment of austempering results in a microstructure consisting of ausferrite and proeutectoid ferrite. From the analysis of quenching results, austempering treatments were performed and then the parameters that lead to certain microstructure were observed. In both treatments, the specimens were characterized by optical microscopy and image analysis. Austempering treatments performed at a temperature of 790°C and intervals of 3 h and 4 h led to a final microstructure which should present an interesting set of mechanical properties.
Keywords
Austempered ductile iron, Austempering, Ferrite, Ausferrite
Referências
1 DRUSCHITZ, A. P.; FITZGERALD, D. C. Madi: Introducing a new, machinable, austempered ductile iron. In: SAE
WORLD CONGRESS, 2003, Detroit. Warrendale: SAE International, 2003.
2 ROUSIÈRE, D.; ARANZABAL, J. Development of mixed (ferrito-ausferritic) structures for spheroidal graphite irons. Metallurgical Science and Technology, v. 18, n. 1, p. 24-9, 2000.
3 ERDOGAN, M.; KILICLI, V.; DEMIR, B. Transformation characteristics of ductile iron austempered from intercritical austenitizing temperature ranges. Journal of Materials Science, v. 44, n. 5, p. 1394-403, Mar. 2009.
4 DRUSCHITZ, A. P.; FITZGERALD, D. C. Machinable austempered cast iron article having improved machinability, fatigue performance, and resistence to environmental cracking and a method of making the same. US Patent 70706664, July 2006.
5 HAYRYNEN, K. L. The production of austempered ductile iron (ADI). In: WORLD CONFEFENCE ON ADI, 2002, Louisville. Illinois: American Foundry Society, 2002. p. 1-6.
6 TRUDEL, A.; GAGNÉ, M. Effect of composition and heat treatment parameters on the characteristics of austempered ductile irons. Canadian Metallurgical Quarterly, v. 36, n. 5, p. 289-98, Dec. 1997.
7 GERVAL, V.; LACAZE, J. Critical temperature range in spheroidal graphite cast irons. ISIJ International, v. 40, p. 386-92, 2000.
8 VERDU, C.; ADRIEN, J.; REYNAUD, A. Contribuition of dual phase (α,G,β) heat treatment to the fadigue properties of SG cast irons. Giessereiforschung, v. 57, n. 4, p. 34-41. 2005.
9 KILICLI, V.; ERDOGAN, M. Tensile properties of partially austenitized and austempered ductile irons with dual matrix structures. Materials Science and Technology, v. 22, n. 8, p. 919-28, 2006.
10 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 6916: Ferro fundido nodular ou ferro fundido com grafita esferoidal. Rio de Janeiro, 1981.
2 ROUSIÈRE, D.; ARANZABAL, J. Development of mixed (ferrito-ausferritic) structures for spheroidal graphite irons. Metallurgical Science and Technology, v. 18, n. 1, p. 24-9, 2000.
3 ERDOGAN, M.; KILICLI, V.; DEMIR, B. Transformation characteristics of ductile iron austempered from intercritical austenitizing temperature ranges. Journal of Materials Science, v. 44, n. 5, p. 1394-403, Mar. 2009.
4 DRUSCHITZ, A. P.; FITZGERALD, D. C. Machinable austempered cast iron article having improved machinability, fatigue performance, and resistence to environmental cracking and a method of making the same. US Patent 70706664, July 2006.
5 HAYRYNEN, K. L. The production of austempered ductile iron (ADI). In: WORLD CONFEFENCE ON ADI, 2002, Louisville. Illinois: American Foundry Society, 2002. p. 1-6.
6 TRUDEL, A.; GAGNÉ, M. Effect of composition and heat treatment parameters on the characteristics of austempered ductile irons. Canadian Metallurgical Quarterly, v. 36, n. 5, p. 289-98, Dec. 1997.
7 GERVAL, V.; LACAZE, J. Critical temperature range in spheroidal graphite cast irons. ISIJ International, v. 40, p. 386-92, 2000.
8 VERDU, C.; ADRIEN, J.; REYNAUD, A. Contribuition of dual phase (α,G,β) heat treatment to the fadigue properties of SG cast irons. Giessereiforschung, v. 57, n. 4, p. 34-41. 2005.
9 KILICLI, V.; ERDOGAN, M. Tensile properties of partially austenitized and austempered ductile irons with dual matrix structures. Materials Science and Technology, v. 22, n. 8, p. 919-28, 2006.
10 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 6916: Ferro fundido nodular ou ferro fundido com grafita esferoidal. Rio de Janeiro, 1981.
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