• Journal of Korean Society of Water and Wastewater
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• v.36 no.5
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• pp.261-273
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• 2022

In this study, we collect water control valves that have had accidents due to existing cracks, etc. are collected, and propose investigation items for strengthening the valve structural safety evaluation through a series of analyzes from valve specifications to physicochemical properties are proposed. The results of this study are as follows. First, there was a large variation in the thickness of the body or flange of the valves to be investigated, which is considered to be very important factor, because it may affect the safety of the valve body against internal pressure and the flange connected with the bolt nut. Second, 60% of the valves under investigation had many voids in the valve body and flange, etc. and the decrease in thickness due to corrosion was relatively large on the inner surface in contact with water rather than the outer surface. It is judged that the investigation of depth included voids is very important factor. Third, all valves to be investigated are made of gray cast iron foam, and therefore it is judged that there is no major problem in chemical composition. It is judged that the chemical composition should be investigated. Fourth, as a physical investigation item, the analysis of metal morphology structure seems to be a very important factor for nodular cast iron from rather than a gray cast iron foam water valve with a flake structure. As it was found to be 46.7~68.8% of the standard recommended by KS, it could have a direct effect on damage such as cracks, and therefore it is judged that the evaluation of tensile strength is very important in evaluating the safety of the valve.

• Journal of Korea Foundry Society
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• v.31 no.3
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• pp.137-144
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• 2011

The effects of thickness, base element and inoculants on the number of eutectic cells and chill depth of gray cast iron plate casting were investigated. Meanwhile the number of eutectic cells increased by inoculation, chill depth decreased. The former decreased and the latter increased by holding the melt at the temperature range between 1,450 and $1,500^{\circ}C$. The former was more for the thinner casting with the thickness of 5 mm than the other. The result of thermal analysis coincided well with the change of macrostructure. The former increased and the latter decreased with the increased contents of carbon, silicon and the silicon content by inoculation. The former decreased and the latter increased with increased manganese content. The performance of the Superseed Extra was the best among 5 inoculants.

• Journal of Korea Foundry Society
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• v.32 no.6
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• pp.261-268
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• 2012

The effects of thickness, base element and additive to inoculant on the number of eutectic cells and chill depth of thin-section gray cast iron were investigated. Meanwhile the number of eutectic cells increased by inoculation, chill depth decreased. The former decreased and the latter increased by holding the melt at the temperature range between 1,450 and $1,500^{\circ}C$. The former was more for the thinner casting with the thickness of 5 mm than the other. The result of thermal analysis coincided well with the change of macrostructure. The former increased and the latter decreased with the increased contents of carbon, silicon and the silicon content by inoculation. The former decreased and the latter increased with increased manganese content. The number of eutectic cells decreased as the amounts of rare earth and the bismuth added to this inoculant increased. With the addition of sulfur of 0.10 wt% of the weight of this inoculant, the maximum number of eutectic cells was obtained.

• Journal of Korea Foundry Society
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• v.1 no.3
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• pp.2-13
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• 1981

It was one of the most important studies in materials to obtain high strength in cant iron. Therefore, malleable cast iron and spheroidal graphite cast iron were developed. However, due to the large demand of gray cast iron, a study on the development for high strength in is very important. The author published a paper on the study on the effect of Al addition. In this study, the effect of Cu addition will be assessed on strength improvement in cast iron. Copper is known as the element of graphitization and pearlitization, so it is expected to obtain valuable results. The results obtained from this study are as follows ; 1. When copper was added to cast iron, tensile strength increased by 30%, and hardness increased by 13%. 2. The tensile strength showed a maximum when copper was added 1.0%.

• Resources Recycling
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• v.27 no.3
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• pp.48-57
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• 2018

In this study, we developed a method for manufacturing high strength gray cast irons by adding a rare earth element (R.E.) included in a spent permanent magnet scrap to gray cast irons. The improvement of the mechanical properties of gray cast irons is attributed to A-type graphite formation promoted by complex sulfide, which was formed by R.E. in the spent magnets during a solidification process. The cast specimen inoculated by R.E. in the spent magnet scrap showed excellent tensile strength up to 306 MPa, and is similar to that of the specimen inoculated by expensive misch-metal. In this regards, we concluded that the cheap spent magnets scrap is a very efficient inoculation agent in fabrication of high performance gray cast irons.

• Journal of Korea Foundry Society
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• v.5 no.4
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• pp.243-257
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• 1985

Many authors have studied the solidification process of cast iron and the effect of grain boundaries in austenite shell on the growth of spheroidal graphite. But, the studies on the melting morphology of cast iron are rare and the effect of grain boundaries in austenite shell on the melting procedure of spheroidal graphite cast iron is unknown. Therefore, in this work, the melting procedure of cast iron and the role of grain boundaries in austenite shell on the melting of spheroidal graphite have been studied. The main results are summarized as follows. 1. In white cast iron containing silicon, melting initiates at the interface between austenite matrix and temper carbon which was decomposed from $Fe_3C$ during heating. 2. In gray cast iron, melting initiates at the boundary of eutectic cell where elements with low melting temperature are condensed. The dissolution of kish graphite is difficult. 3. In spheroidal graphite cast iron containing little phosphor, melting initiates at the outer region of austenite shell in which silicon is condensed. In this case, grain boundaries in austenite shell give little effect on the melting procedure of spheroidal graphite. 4. In spheroidal graphite cast iron containing phosphor above 0.3 wt%, its melting phenomena are changed with heating rate due to the existence of steadite. In this case, it can be concluded that liquid phase of steadite, which segregated on outer region of austenite shell, moves to spheroidal graphite-austenite interface along the grain boundaries in austenite shell.

• Journal of Korea Foundry Society
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• v.6 no.1
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• pp.27-35
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• 1986

The gating design of gray cast iron was programmed in a Personal computer. By this program, casting test was done. The results obtained are as follows. 1. Gating design that can calculate the velocity of metal flow and size in each gate section by knowing the loss coefficient caused by friction loss and bend loss was programmed. 2. In the test casting, the gating ratio was changed into 1.1:1.3:1, 1:2:2, 1:4:4. And sound casting, free of sand washing defect, was obtained at the velocity of 35.5cm/sec in ingate.

• Journal of Korea Foundry Society
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• v.2 no.3
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• pp.2-15
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• 1982

In this study, the influenced of graphite shape on the boriding of cast iron and boride structure was investigated. Gray cast iron, ferritic and pearlitic ductile cast iron were borided at 750,850,900 and $950^{\circ}C$ for 1,3 and 5 hours by powder pack method with the mixture of $B_4C_9\;Na_2B_4O_7$, $KBF_4$ and Shc. The boride layer was consisted of FeB(little), $Fe_2B$ (main) and graphite. Some possibility of the existence of unknown Fe-B-C compound in the boride layer was suggested. And precipitates in the diffusion zone was $Fe_3(B,C)$. The concentration of Si and precipitation of $Fe_3(B,C)$ in the ${\alpha}$ layer raised the hardness of this Zone. The depth and hardness of boride layer increased with the increase of treating temperature and tim. But high temperature (over $950^{\circ}C)$ caused pore at graphite position and long treating time (5hrs) sometimes caused formation of graphite layer beneath the boride layer. So, for the practical application of borided cast iron, treating in short time and at low temperature was recommended. And for ductile cast iron, ferritizing or pearlitizing heat treatment was seemmed to be possible at the same time with boriding. The graphite in the boride layer was deeply concerned with the qualitx and characteristics of the boride layer. And it greatly influenced on the shape of the boride phase, structure of the boride layer. Generally speaking, the existance of graphite restrained the growth of the boride phase. But the boundary between the gsaphite and the matrix acted as the shortcut of boron diffusion. So, for gray cast iron, the graphite layed length-wise led the formation of boride layer.

• Tribology and Lubricants
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• v.20 no.6
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• pp.299-305
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• 2004

The wear properties of clutch facing materials with two different copper amounts were evaluated against the fly-wheel materials used in clutch system, such as gray cast iron and spheroidal graphite cast iron. Sliding wear tests were carried out for four different combinations with these clutch facing materials and flywheel materials at different speeds and applied loads. Results showed that the clutch facing material contained a higher copper amount had the better wear resistance. And using the gray cast iron as the counter material, clutch facing material resulted in the much lower wear rate, regardless of the copper amount. It is obvious that the wear properties of clutch facing material are influenced from the thermal conductivities of the clutch facing material and the counter material.

• Journal of Korea Foundry Society
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• v.24 no.5
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• pp.295-303
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• 2004

The effects of three minor elements, S, Ce and Bi, on the inoculation ability and fading behavior of 1.0 wt%Ba-Fe-Si were investigated through thermal analysis. The performance of 1.0 wt%Ba-Fe-Si inoculant was better and more consistant at the high temperature range of $1,450{\sim}1,500^{\circ}C$ than that of low one of $1,300{\sim}1,400^{\circ}C$. That was improved with individual addition of three minor elements. The optimum amount of addition was 1.0% of the weight of inoculant added, respectively. That was improved also by the simultaneous addition of two or three kinds of minor elements. Even though worse with the addition of two kinds of them simultaneously than with individual addition, that was improved with the simultaneous addition of all three kinds over that with the individual one.