Study of Blowholes Formation and its Prevention in Nodular Iron Castings

Abstract:

The content of magnesium in various parts of a nodular iron casting is measured by using spectrum analyzer. The results show that the skin of castings has an enrichment of magnesium, and the inner has a gradient distribution of magnesium, not an average distribution. Discussions on the results indicate that bubbles in the liquid metal would not move upward under the action of buoyancy, but migrate toward all directions and the bubble stranded below the surface of the liquid metal form blowholes, because these bubbles can not migrate with the obstruction of oxide films and dendrites. The results of production practices show that increasing carbon equivalent in the liquid metal is helpful to avoid blowhole defects.

• Periodical: Key Engineering Materials (Volume 584)
• Pages: 67-72
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.584.67
• Online since: September 2013
• Authors: Shao Dong Sun, Shi Jian He, Meng Qun Zhang, Xiang Ma
• Keywords: Blowhole, Bubble Migration, Carbon Equivalent, Extrusion Pressure, Oxide Film

References

[1] LIU Rong, TAN Chuan-miao, ZHOU Song-liu. Analysis of Subskin Blowhole of Nodular Iron in Piston Ring Through Scanning Electronic Microscope[J]. Foundry, v50, n12, pp.756-758, December. (2001).

[2] Wang Jing-de. Influence FactorS and Precautions of Blowholes in Nodular Cast Iron[J]. Foundry, n7, pp.25-29, July (1994).

[3] LE GALL R, DAZELLE G, DANYLOVA O, WITZKE S. Effect of sulfur and phosphorus on ductility of as cast iron-nickel-chromium alloys, direct observation on in-situ fractured surface by AES and TEM. Materials Science Forum, 2003, 426-432(2): 1041-1046.

DOI: 10.4028/www.scientific.net/msf.426-432.1041

[4] SUN Wei-qing, GUO Ling-jun. Summary of Subsurface Blowhole in Nodular Cast Iron[J]. Foundry Technology, n4, pp.32-36, April (1996).

[5] LI Qing-chun. Theoretical Foundation of Casting Formation[M]. Bejing: China Machine Press, p.192, (1982).

[6] NARO R L, PELFREY R L. Gas evolution of synthetic core binders: relationship of blowhole defects [J]. Trans. the American Foundry men's Society, 1983, 91: 365-376.

[7] RYNTZ JR E F, CHAPUT W , RASSENFOSS W O, SCHROEDER R E. Formation of blowhole in nodular iron castings[J]. The American Foundrymen's Society, 1983, 91：161-164.

[8] LU Wen-hua. Cast Iron and Its Melting[M]. Bejing: China Machine Press, p.94, (1986).

[9] XU Jin-feng, ZHAI Qiu-ya, YUAN Sen, WEI Bing. Morphology Characteristic and Growing Manner of Austenite in Hypereutectic Ductile Iron during Solidification Process. Acta Metallurgic Sinica, v39, n2, pp.136-139, February (2003).