Tecnologia em Metalurgia, Materiais e Mineração
https://tecnologiammm.com.br/article/doi/10.4322/tmm.2011.035
Tecnologia em Metalurgia, Materiais e Mineração
Artigo Original

ADEQUAÇÃO DA COMPOSIÇÃO QUÍMICA E DO TRATAMENTO TÉRMICO DE FERROS FUNDIDOS DE ALTO CROMO UTILIZANDO TERMODINÂMICA COMPUTACIONAL

OPTIMIZING HEAT TREATMENT OF HIGH CHROMIUM CAST IRONS USING COMPUTATIONAL THERMODYNAMICS

Albertin, Eduardo; Beneduce Neto, Flavio; Teixeira, Ivênio de Oliveira

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Resumo

O objetivo do presente trabalho é a aplicação dos recursos de termodinâmica computacional para a otimização dos tratamentos térmicos dos ferros fundidos de alto cromo. Apresentam-se as características das ligas comerciais baseadas no sistema Fe-Cr-C e as etapas de aplicação da termodinâmica computacional para auxiliar na previsão das microestruturas e propriedades que podem ser obtidas em função das composições químicas e tratamentos térmicos das ligas. São apresentados os resultados de dois casos práticos. Foi desenvolvida uma liga com 31%Cr e adição de nitrogênio, combinando resistência ao desgaste e à corrosão, graças à obtenção de uma matriz martensítica com dureza acima de 700 HV, contendo mais de 14% de cromo dissolvido. Para obter resistência ao desgaste e a impactos foi desenvolvida uma liga com 17%Cr com adição de 1,5%Mo. A análise por termodinâmica computacional permite prever a composição química da liga e o tratamento térmico necessários para atingir 0,8%Mo dissolvido na austenita antes da têmpera, o que favorece a obtenção de dureza secundária durante o tratamento de revenimento.

Palavras-chave

Ferro fundido alto cromo, Termodinâmica computacional

Abstract

A methodology for using computational thermodynamics to optimize heat treatments of high chromium cast irons is presented. The main characteristics of the commercial alloys based on the Fe-Cr-C system are discussed, together with the steps to be applied using computational thermodynamics to preview microstructures and properties that can be achieved, resulting from different alloy compositions and heat treatments. The results of application of the method for two practical cases are presented. A 31%Cr alloy (all percentages are by mass, unless otherwise stated), with nitrogen addition, was developed to resist to abrasion and corrosion, a result obtained thanks to a martensitic matrix with hardness over 700 HV, containing over 14% dissolved chromium. An abrasion and impact resistant alloy was developed using computational thermodynamics to establish the chemical composition and heat treatment to obtain 0.8%Mo dissolved in the austenite previously to the quenching treatment, leading to secondary hardening during tempering.

Keywords

High chromium cast iron, Computational thermodynamics

Referências

1 THORPE W.R.; CHICCHO, B. The Fe-rich corner of the metastable C-Cr-Fe liquidus surface. Metallurgical Transactions A, v. 16, n. 9, p. 1541-8, Sep. 1985. http://dx.doi.org/10.1007/BF02663011

2 ALBERTIN. E.; SINATORA, A. Effect of carbide fraction and matrix microstructure on the wear of cast iron balls tested in a laboratory ball mill. Wear, v. 250, n 1, p. 492-501, Oct. 2001. http://dx.doi.org/10.1016/S0043- 1648(01)00664-0

3 MARATRAY, F.; USSEGLIO-NANOT, R. Factors affecting the structure of chromium and chromium-molybdenum white irons. Paris: Climax Molibdenum, 1970.

4 TABRETT, C.P.; SARE, I.R. The effect of heat treatment on the abrasion resistance of alloy white irons. Wear, v. 203, n. 1, p. 206-19, Mar. 1997. http://dx.doi.org/10.1016/S0043-1648(96)07390-5

5 SARE, I.R; ARNOLD, B.K. The influence of heat treatment on the high-stress abrasion resistance and fracture toughness of alloy white irons. Metallurgical and Materials Transactions A, v. 26, n. 7, p. 1785-93, July 1995. http://dx.doi.org/10.1007/BF02670766

6 MARATRAY, F.; USSEGLIO-NANOT, R. Transformation characteristics of chromium and chromium-molybdenum white irons (atlas). Paris: Climax Molibdenum, 1970.

7 SINATORA, A.; MATSUBARA, Y. Effects of de-stabilization conditions on the precipitation of secondary carbide and martensite transformation of high chromium cast iron. In: CONGRESSO ANUAL DA ABM, 52.; CONGRESSO INTERNACIONAL DE TECNOLOGIA E DE MATERIAIS, 2., 1997, São Paulo. São Paulo: ABM, 1997.

8 AMORIM, P. et al. Soft annealing of high chromium white cast iron. Materials Science Forum, v. 455-456, p. 290-4, May 2004. http://dx.doi.org/10.4028/www.scientific.net/MSF.455-456.290

9 PATTYN, R.L. Tratamento térmico de ferros brancos de alto cromo. Fundição e Serviços, v. 6, n. 38, p. 47-57, fev. 1996.

10 CIAS, W. W. Austenite transformation kinectis and hardenability of heat-treated 17.5%Cr wite cast irons. AFS Transactions, v. 82, p. 317-28, 1974.

11 WINCHELL, P.G.; COHEN, M. The effect of carbon on the hardness of martensite and austenite. Transactions of the Metallurgical Society of AIME, v. 224, p. 639, 1962 apud BHADESHIA, H. et al. Steels microstructure and properties. Oxford: Butterworth-Heinemann, 2006.

12 BELL, T. Martensitic and massive transformations in ferrous alloys. In: PETTY, E. R.(ed.). Martensite: fundamentals and technology. London: Longmans,1970 (apud BHADESHIA, H. et al. Steels microstructure and properties. Oxford: Butterworth-Heinemann, 2006.

13 BENZ, R.; ELLIOT,J. F.; CHIPMAN, J. Thermodynamics of the Carbides in the system Fe-Cr-C. Metallurgical and Materials Transactions B, v. 5, n. 10, p. 2235-10, Oct. 1974.

14 JACKSON, R. S. The Austenite liquidus surface and constitutional diagram for the Fe-Cr-C metastable system. Journal Iron And Steel Institute, v. 208, p. 163-7, 1970.

15 BUNGARDT, K.; KUNZE, E.; HORN, E. Untersuchungen über den Aufbau des Systems Eisen-Chrom-Kohlenstoff. Archif für das Eisenhüttenwessen, v. 29, p. 193-203, 1958.

16 INTHIDECH, S. et al. Behavior of hardness and retained austenite in heat treatment of high chromium cast iron for abrasive wear resistance. Transactions American Foundry Society, v. 112, p. 899-910, 2004.

17 ANDREWS, K.W. Empirical formulae for the calculation of some transformations temperatures. Journal Iron and Steel Institute, v. 203, p. 721-27, 1965.

18 CAPDEVILLA, C.; CABALLERO, F. G.; GARCIA DE ANDRÉS, C. Determination of Ms temperatures in steels: a Bayesian neural network model. Journal Iron and Steel Institute of Japan International, v. 42, n. 8, p. 894-902, Aug. 2002. http://dx.doi.org/10.2355/isijinternational.42.894

19 ISHIDA, K. Calculation of the effect of alloying elements on the Ms temperature in steels. Journal of Alloys and Compounds, v. 220, n. 1, p. 126-31, Apr. 1995. http://dx.doi.org/10.1016/0925-8388(94)06002-9

20 BELL, T. Martensite transformation start temperature in iron-nitrogen alloys. Journal Iron and Steel Institute, v. 206, n. 10 p. 1017-21, Oct. 1968.

21 MITTEMEIJER, E. J. et al Tempering of iron-nitrogen martensite. Zeitschrift für Metalkunde, v. 74, n. 7, p. 473-483, 1983.

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