Efeito da espessura do fundido (de 3,2 a 5,8 mm) no limite de resistência de ferro fundido cinzento perlítico
Effect of the casting thickness (3.2 to 5.8 mm) on the tensile strength of grey cast iron
Felipe Fonseca de Oliveira Lima, Cesar Roberto de Farias Azevedo
Resumo
O limite de resistência e a macro e microestruturas de ferro fundido cinzento perlítico com carbono equivalente igual a 4,25% foram investigados para espessuras de parede variando entre 3,2 e 5,8 mm (velocidade de resfriamento entre 29 e 6°C/s). Foram empregadas técnicas de caracterização microscópica para quantificar os principais parâmetros macro e microestruturais. A redução da espessura do fundido promoveu o refino do espaçamento secundário dos braços de dendritas de austenita (SDAS), do tamanho médio das células eutéticas (TMCE), do tamanho médio das colônias de perlita (TMCP), do espaçamento interlamelar médio da perlita (λperlita) e do diâmetro hidráulico interdendrítico (DHid). Como consequência, ocorreu um aumento no valor máximo do limite de resistência à tração de 274 para 420 MPa com o aumento da velocidade de resfriamento. Esses resultados foram usados para testar dois modelos matemáticos de predição do limite de resistência de ferros fundidos cinzentos perlíticos em função de seus parâmetros macro e microestruturais.
Palavras-chave
Abstract
The tensile strength and the macro and microstructures of pearlitic grey cast iron with wall thickness varying from 3.2 to 5.8 mm (cooling velocity between 29 e 6°C/s) were investigated. Microscopic characterization techniques were employed to quantify the main macro and microstructural parameters. The reduction in cast thickness refined the austenite dendrite arm spacing (SDAS), the mean size of the eutectic cell (TMCE), the mean size of the pearlite colonies (TMCP), the pearlitic interlamellar spacing (λpearlita) and the interdendritic hydraulic diameter (DHid). Consequently, there was an increase in the average value of the tensile strength from 274 to 420 MPa due to the increase of the cooling velocity. These results were used to test two mathematical models, which use the macro and microstructural parameters of the pearlitic grey cast irons to predict their tensile strength.
Keywords
References
1 Elliott R. Cast Iron technology. London: Butterworth & Co.; 1988.
2 Campbell J. Complete casting handbook - metal casting processes, metallurgy, techniques and design. USA: Elsevier; 2015.
3 Stefanescu DM. Science and engineering of cast solidification. USA: Springer; 2009.
4 Górny M, Tyrala E. Effect of cooling rate on microstructure and mechanical properties of thin-walled ductile iron castings. Journal of Materials Engineering and Performance. 2013;22:300-305.
5 Santos ABS, Branco CHC. Metalurgia dos feros fundidos cinzentos e nodulares. São Paulo: IPT; 1989.
6 Beste F, Schöffmann W, Marquard R. Lightweight design - a challenge for modern passenger car engines. Seoul: Age International; 2000. FISITA World Automotive Congress.
7 Guesser WL, Cabezas CS, Guedes LC, Zanatta AM. High temperature strength of cast irons for cylinder heads. Materials Science Forum. 2018;925:385-392.
8 Stefanescu DM. Lightweight iron castings – can they replace aluminum castings? In: Proceedings of the 65th World Foundry Congress; 2002; Gyeongju, Korea. Seoul: The Korean Foundrymen’s Society. p. 71-77.
9 Frás E, Górny M, Lopez H. Thin wall ductile iron castings as substitutes for aluminium alloy castings. Archives of Metallurgy and Materials. 2014;59(2). http://dx.doi.org/10.2478/amm-2014-0076.
10 Du Pont. [online] Du Pont. [cited 2016 Apr 5]. Available at: http://www.dupont.com/industries/automotive/articles/lightweighting.html
11 Granta Design. CES Edupack. USA: Granta Design; 2019. Software.
12 Lima FFO. Influência da espessura e do carbono equivalente nas propriedades mecânicas de tração de ferros fundidos cinzentos com espessura fina de parede [dissertação]. São Paulo: Universidade de São Paulo; 2020.
13 Vazehrad S. Shrinkage porosity characterization in compacted cast iron components [thesis]. Stockholm: Royal Institute of Technology; 2011.
14 Collini L, Nicoletto G, Konecná G. Microstructure and mechanical properties of pearlitic gray cast iron. Materials Science and Engineering A. 2008;488:529-539.
15 Behnam MMJ, Davami P, Varahram N. Effect of cooling rate on microstructure and mechanical properties of gray cast iron. Materials Science and Engineering A. 2010;528:583-588.
16 Fourlakidis V, Diaconu LV, Diószegi A. Effects of carbon content on the ultimate tensile strength in gray cast iron. 2010;649:511-516.
17 Fourlakidis V, Diószegi A. A generic model to predict the ultimate tensile strength in pearlitic lamellar graphite iron. Materials Science and Engineering A. 2014;618:161-167.
18 Anderson TL. Fracture mechanics - fundamentals and applications. 4th ed. Boca Raton: CRC Press; 2017.
19 Hyzak JM, Bernstein IM. The role of microstructure on the strength and toughness of fully pearlitic steels. Metallurgical Transactions A. 1976(7):1217-1224.
20 Kavishe FPL, Baker TJ. Effect of prior austenite grain size and pearlite interlamellar spacing on strength and fracture toughness of a eutectoid rail steel. Materials Science and Technology, 1986;2(8):816-822.
21 Modi OP, Desmukh N, Mondal DP, Jha AK, Yegneswaran AH, Khaira HK. Effect of interlamellar spacing on the mechanical properties of 0.65% C steel. Materials Characterization. 2006;46:347-352.
22 Foulakidis V, Diaconu LV, Diószegi A. Strength prediction of lamellar graphite iron: from Griffith’s to Hall-Petch modified equation. Materials Science Forum. 2018;925:272-279.
23 Fourlakidis V, Belov I, Diószegi A. Strength prediction for pearlitic lamellar graphite ion: model validation. Metals. 2018;8(9):684.
24 ASTM International. ASTM E8/E8M - 16a: Standard Test Method for tension test of Metallic Materials. West Conshohocken: ASTM International; 2016.
25 Rivera GL, Boeri RE, Sikora JA. Revealing the solidification structure of nodular iron. Cast Metals. 1995;8(1):1-5
Submitted date:
04/01/2020
Accepted date:
07/20/2020
Facebook
Google+
Twitter
LinkedIn
Mendeley
StumbleUpon
CiteULike
Reddit
Email