Conditions Forming to Blow-Hole Defects in Casting

Abstract:

This study investigates the relationship between core gas pressure, solid phase fraction in the sand core, and gas porosity formation in casting processes. The experiments were conducted using EN AC-45500 aluminium alloy, varying casting temperatures and casting diameters. The maximum core gas pressure was measured and correlated closely with the solid phase fraction at the sand core-metal interface. Notably, the study reveals that gas breakthroughs can occur even at core gas pressures lower than the metallostatic pressure. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to analyse the blow-holes imprints and their chemical composition, confirming that the observed porosity originates from core gas. The results underline the importance of the solid phase fraction in controlling gas porosity formation and provide new insights into the mechanisms of blow-holes formation in aluminium alloy casting.

• Periodical: Materials Science Forum (Volume 1153)
• Pages: 13-22
• DOI: https://doi.org/10.4028/p-Ewe9jz
• Online since: June 2025
• Authors: Laura Mádi*, Dániel Molnár
• Keywords: Blow-Holes (Gas Bubble), Casting Defect, Core Gas, Gas Pressure

References

[1] L. Winardi, H.E. Littleton, C.E. Bates: Pressures in Sand Cores, AFS Transactions, vol.115., Paper 07-062(04).pdf, (2007) 303-312

[2] Y. Maeda1, H. Nomura, Y. Otsuka, H. Tomishige, Y. Mori "Numerical simulation of gas flow through sand core" Int. J. Cast Metals Res., (2002), 15, 441-444

DOI: 10.1080/13640461.2003.11819525

[3] Laurentiu Nastac, Shian Jia, Mihaela N. Nastac & Robert Wood: Numerical modeling of the gas evolution in furan binder-silica sand mold castings- International Journal of Cast Metals Research VOL. 29. NO. 4, (2016) 194-201

DOI: 10.1080/13640461.2015.1125983

[4] Hassan Khawaja: Semi-implicit method for pressure-linked equations (SIMPLE) ⇓ solution in MATLAB- Int. Jnl. of Multiphysics Volume 12, Number 4, (2018) 313-325

DOI: 10.21152/1750-9548.12.4.313

[5] Worman, R.A., Nieman, J.R.: A Mathematical System for Exercising Preventive Control over Core Gas Defectes in Gray Iron Castings, TAFS 81, (1973) 170–179

[6] A. Starobin, D. Goettsch, M. Walker, D. Burch: Gas Pressure in Aluminum Block Water Jacket Cores, International Journal of Metalcasting/Summer, (2011) 57-64

DOI: 10.1007/bf03355518

[7] A.J. Starobin and C.W. Hirt: FLOW-3D Core Gas Model: Binder Gas Generation and Transport in Sand Cores and Molds- Flow Science Report 04-14 (2014)

[8] Andrei Starobin, C.W. Hirt, D. Goettsch: A Model for Binder Gas Generation and Transport In Sand Cores And Molds, Modeling of Casting, Welding, and Solidification Processes XII TMS (The Minerals, Metals & Materials Society) (2009)

[9] P. Scarber, C.E. Bates, "Simulation of Core Gas production During Mold Fill,", AFS Transaction, vol. 114, paper no. 138 (2006)

[10] S.Ravi, J. Thiel: Prediction of Core Gas Pressure from Chemically Bonded Sand Molds Using Process Simulation Software, AFS Transactions, Paper 17-097 v125 - Page 1 of 8 (2017)

[11] KIMATSUKA Akihiko, KUROKI Yasunori: Mold Filling Simulation for Predicting Gas Porosity, Engineering Review, Vol. 40. No. 2., pp.83-88 (2007)

[12] IKO-Erbslöh, Jörg Baier, Martin Köpper: Manual of Casting Defects, Incidence and avoidance of defects attributable to molding sands, (1994), P: 51-55.

[13] P.Scraber, C.Bates, J.Griffin: Avoiding gas defects through mould and core package design. Modern Casting, v. 96, issue 12, (2006), pp.38-40.

[14] John Campbell: Complete Casting Handbook- 10.5. Rule 5: 'Avoid core blows' 635-659

[15] Bates CE, Monroe RW: Mold binder decomposition and its relation to gas defects in castings. AFS Trans 89:671–686 (1981)

[16] H. Gerard Levelink, F.P.M.A. Julien und H.C.J. De Man, Apeldoorn: Gasentwicklung in Formen und Kernen als Ursache von Gußfehlern, Gießerei 67 (1980) Nr. 5-3 März, S.: 109-115.

[17] Walter Schlesiger, Johannes W interhalter und Wilfried Siefer: Zur Gasabführung aus Kernen, Giesserei, Nr. 4 16. Februar, (1987) 76-84

[18] W. BAUER: Einfluß der chemischen Zusammensetzung und des Formstoffes auf Gasblasenfehler in Gußeisen, GIESSEREI-PRAXIS Nr. 12, (1984) 198-205

[19] Vivek V. Yadav, Shailesh J. Shaha: Quality Analysis of Automotive Casting for Productivity Improvement by Minimizing Rejection, International Journal of Mechanical And Production Engineering, ISSN: 2320-2092, Volume- 4, Issue-6 (2016)

[20] Doru Michael Stefanescu: Surface Quality, Penetration Defects and Casting Skin, Course Metallurgy, solidification and modeling of cast iron castings 5th edition, Presentation, Jönköping, Sweden (2017)

[21] A.Chojecki, J. Mocek: Gas pressure in sand mould poured with cast iron, Archives of Foundry Engineering Volume 11, Issue, 1/2011, 9-14

[22] Yamamoto Y et al: Gas pressure in shell mold cores made of olivine sand during casting. AFS Int Cast Met J 5(2):60–65 (1980)

[23] T. Szmigielski: Measurement of gas pressure in sand mould. Archives of Mechanical Technology 24, (2004), nr 3, pp.163-171.

[24] Toth L., Nandori Gy.: Verringerung gasbedingter Fehler in Gußstücken, Sov. Cast Technol. P. 4-7 (engl.) Litejnoe proizvodstvo 1988, P- 6-7 (russ.) (1988)

[25] J. Svidró, A. Diószegi, L. Tóth, J.T. Svidró: The Influence of Thermal Expansion of Unbonded Foundry Sands on The Deformation of Resin Bonded Cores, Arch. Metall. Mater. 62 (2017), 2, 795-798, Doi: 10.1515/Amm-2017-0118 (2017)

DOI: 10.1515/amm-2017-0118

[26] M. Divandari, J. Campbell: Morphology of oxide films of Al–5Mg alloy in dynamic conditions in casting, International Journal of Cast Metals Research 2005 Vol. 18 No. 3 P. 187-192, (2005)

DOI: 10.1179/136404605225023000

[27] John Campbell: Leakage Defects Via Bubble Trails In Grey Iron Castings, International Journal of Metalcasting/Fall 07-20 (2007)

DOI: 10.1007/bf03355414

[28] Gábor Gyarmati, Gy. Fegyverneki, T. Mende, M. Tokár: Characterization of the double oxide film content of liquid aluminum alloys by computed tomography, Materials Characterization 157, 109925https://doi.org/10.1016/j.matchar.2019.109925 (2019)

DOI: 10.1016/j.matchar.2019.109925

[29] G. Gyarmati, Gy. Fegyverneki, Z. Kéri, D. Molnár, M. Tokár, L. Varga, T. Mende : Controlled precipitation of intermetallic (Al,Si)3Ti compound particles on double oxide films in liquid aluminum alloys, Materials Characterization, Volume 181, 111467 (2021)

DOI: 10.1016/j.matchar.2021.111467

[30] S.Ravi, J. Thiel: Prediction of Core Gas Pressure from Chemically Bonded Sand Molds Using Process Simulation Software, AFS Transactions, Paper 17-097 v125 - Page 1 of 8 (2017)

[31] A.Chojecki, J. Mocek: Gas pressure in sand mould poured with cast iron, Archives of Foundry Engineering Volume 11, Issue, 1/2011, 9-14 (2011)

[32] M. B. Djurdjevic, Z. Odanovic, J. Pavlivic-Krstic: Melt Quality Control az aluminum Casting Plants, MJoM Vol 16 (1) 2010 pp.63-76) (2010)

[33] G. Gyarmati, Gy. Fegyvereneki, M. Tokár: The effects of rotary degassing treatments on the melt quality of an Al–Si casting alloy, International Journal of Metalcasting/Volume 15, Issue 1, pp.141-151 (2021)

DOI: 10.1007/s40962-020-00428-z