Study of pinholes genesis in iron castings

• Autorzy: Elbel, T. , Hampl, J. , Senkypl, M.
• Języki publikacji: EN

Abstrakty

EN

Purpose: The study concerns the formation of pinholes in castings formed by reaction between a green foundry mould and lamellar graphite cast iron. Great numbers of works have been aimed at clarifying the causes of pinholes formation in iron castings. In spite of this there exists no united opinion on the pinholes formation (genesis) and the authors of this contribution having studied this phenomenon in compacted graphite and spheroidal graphite iron castings were also aimed at lamellar graphite cast iron and they applied for it their knowledge gained in study of reoxidation processes during casting of ferrous alloys. Methodology: Experiments were done on castings of stepped bars moulded in green bentonite mixtures with s graduated moisture and with use of two types of carbonaceous matters. Metal was melted in a 100 kg induction furnace from the same charge. Inoculation was done in a ladle after pouring out from the furnace. Aluminium was dosed in the ladle in some cases and the inoculator kind was changed too. Results: Pinholes were present on castings as small flat pits; on horizontal surfaces sooner singly, on casting edges in clusters. The formation of pinholes wasn't caused by high moisture of moulds but the defect was sensitive to aluminium content in metal. In castings with high aluminium content > 0.01 % the pinholes were present in great numbers, and namely both under low, and also high moistures of moulding mixtures. In melts with low content of Al < 0.01 % the pinholes occurred less extensively only. Practical implications: Conclusions from literature about influence of Al on pinholes occurrence were confirmed in such a way. Study of the defect morphology has shown that the question is a oxidation reaction type of pinholes caused by oxidation of the residual melt between dendrites with formation of CO.

Słowa kluczowe

PL

wada odlewania; otwór w żeliwie; żeliwo

EN

casting defect; pinholes; cast iron

• Czasopismo: Archives of Foundry Engineering
• Rocznik: 2011
• Tom: Vol. 11, iss. 1
• Strony: 21-26
• Opis fizyczny: Bibliogr. 15 poz., rys., tab., wykr.,

Twórcy

autor

Elbel, T.

autor

Hampl, J.

autor

Senkypl, M.

• Department of Foundry Engineering, Technical University of Ostrava, Tr. 17. listopadu, 708 33 Ostrava - Poruba, Czech Republic,

Bibliografia

• [1] T. Elbel et al.: Vady odlitků ze slitin železa. MATECS, Brno 1992. (In Czech).
• [2] P. Levíček,K. Stránský: Metalurgické vady ocelových odlitků. SNTL, Praha, 1984 (In Czech).
• [3] International atlas of casting defects, American Foundrymen´s Society,Inc. Des Plainjes, IL.,1993.
• [4] S. Hasse.: Guss- und Gefügefehler. Schiele & Schön, Berlin 1999.
• [5] T. Elbel. J. Hampl: Influence of aluminium on the formation of pinholes in cast irons. Archives of Foundry Engineering, vol. 6,issue 2/2008,27-32.
• [6] J. Hampl, T. Elbel, L. Kocián: The formation of pinholes in SG iron castings. Transactions of the VŠB - Technical University of Ostrava. Metallurgical Series, vol 49, issue 1/2006, s. 57-64, (In Czech).
• [7] T. Elbel, J. Senberger, A. Zadera. J. Hampl: Behaviour of oxygen in cast irons. Archives of Materials Science and Engineering, vol.33,issue2/2008, s.111-116.
• [8] M. Hecht; V. Castelhano: La formation des piqures par reaction entre la fonte a graphite lamellaire et le sable vert. FONDERIE Fońdeur d aujourd´hui, Part I, No 251, janvier 2006, s. 12-32. Part II. No 256, juin-juillet 2006, s. 13-28. Part III, No 257, aout-septembre 2006, s. 10-24.
• [9] Y. Kurokawa et al.: Observation of Pinhole Defects in Cast Iron Castings by Surface Analysis. AFS Transactions 2002, vol. 110, pp. 629-637.
• [10] R. Foret.: Analysis of pinholes in a casting of cover from GJS. Slévárenství, LVII, 2009, č. 7/8, s. 245-248 (In Czech).
• [11] M. Senkypl: Diploma thesis. VŠB - TU Ostrava, 2010. (In Czech).
• [12] S. Katz: New Theory for Aluminium-Induced Gas Defects in Iron Castings and Potential Solutions. AFS Transactions, vol. 114, 2006, s. 775 - 782.
• [13] J. Mocek; A. Chojecki: Evolution of the gas atmosphere during filing the sand moulds with iron alloys. Archives of Foundry Engineering, vol. 9, isme 4/2009,s. 135-140.
• [14] A. Chojecki: Hydrogen in reoxidation process. Technológ, vol. II, special issue,april 2010, s. 71-76.
• [15] A. Zadera; J.Senberger; T. Elbel: Reoxidation processes at casting from ferrous alloys. CSS, Brno 2009.(In Czech).