Tsuchiura City, Japan
Tsuchiura City, Japan

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Nasu S.,I Metal Technology Co. | Fujita S.,I Metal Technology Co. | Furusato N.,I Metal Technology Co. | Yamada S.,I Metal Technology Co. | Hiratsuka S.,Iwate University
72nd World Foundry Congress, WFC 2016 | Year: 2016

The microstructure around casting skin of cast iron changes according to conditions such as the mold and cooling speed. When self-hardened mold is used, the all pearlite is obtained. When green sand mold is used, the microstructure of the pearlite and the ferrite is obtained. In this study, we conducted fatigue tests on two kinds of gray cast iron: one is the sample taken from casting skin consisting of fully pearlite and another one is the sample consisting of pearlite-ferrite mixture, and investigated the effects of fatigue strength. For comparison, tests were also conducted on the sample of perlite matrix whose surfaces have been machined, sampled from inside the material. The fatigue strength of the casting skin compared with the thoroughly machined sample (from the internal part), in case of pearlite casting skin increased 20% and in case of pearlite-ferrite mixed decreased 12%. Because the tensile strength of ferrite is supposed to be lower than one of pearlite, fatigue strength became lower. Comparing thoroughly machined with casting skin both in pearlite matrix, the fatigue strength of casting skin was higher because the cooling rate was faster in the casting surface, graphite size became refiner and the number of eutectic cell was larger than the inside. © 2016, The WFO (The World Foundry Organization Ltd). All rights reserved.


Nakayama H.,I Metal Technology Co. | Zhao B.-R.,I Metal Technology Co. | Furusato N.,I Metal Technology Co. | Yamada S.,I Metal Technology Co.
72nd World Foundry Congress, WFC 2016 | Year: 2016

Chunky graphite is generated in the heavy sectioned castings [1], and will be detrimental to the mechanical properties of cast irons, especially ductility and toughness [2]. However, there is little review showing change of mechanical properties by the amount of chunky graphite quantitatively. In this study, the cylindrical casting which contained some chunky graphites was made. As base metals, highly pure pig iron and steel scrap with Fe-Si and RE-Si alloys were used. We took some specimens from the casting, and measured mechanical properties by the tensile strength test and the brinell hardness test. Tensile strength was not affected until the chunky graphite amount of about 20%. However, when the amount exceeded this percentage, it started to get down gradually, and eventually decreased about 50MPa which is lower than the only spheroidal graphite region. Elongation was not decreased so much when the chunky graphite amount was up to about 20%, however when the amount exceeded 20%, it decreased rapidly to about 40% and remained the same. On the other hand, yield strength and hardness were not affected. © 2016, The WFO (The World Foundry Organization Ltd). All rights reserved.

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