• Journal of Technologic Dentistry
• /
• v.23 no.2
• /
• pp.203-210
• /
• 2002

This test is to conduct applied research the reaction area of the Ti-cast metal body which is made use of Dental Phosphate-silica alumina bonded investment material selling at a market, and the cooling method is how to effect on the acicular. The experimentation is as followings, 1. Experimental specimens After invest with Dental Phosphate-silica alumina bonded investment material, the $10{\times}10{\times}1.0mm^3$ wax pattern was casted by Dental high vacuum argon centrifugal casting machine. 2. Test We can analyze SEM/EDS, XRD utilize the fractography(an optical microscope). 3. Conclusion The pure cast metal body constituted of reaction products layer, stability layer and contamination layer. This pure cast have no connection with the cooling condition. The pure Titanium shows difference in a component distribution according to the cooling condition. Through this experimentation we can establish that acicular in the pure Ti-cast metal is consist of Hexagonal structure a=2.9505$\AA$, c=4.6826$\AA$.

• Journal of Korea Foundry Society
• /
• v.29 no.2
• /
• pp.70-77
• /
• 2009

The aim of this study was to develop a Mo and V free low alloy cast steel materials, enabling the significant cost- and time-savings in manufacturing and maintaining the insert of cold pressing die without impairment of the important properties. For this purpose, the effects of Si content on combinations of important properties such as hardness, hardenability, and weldability, and strength were systematically investigated. In order to evaluate the applicability as the insert of cold pressing die, the mechanical properties were measured after spheroidization annealing, quenching and tempering, and flame hardening heat treatments, respectively. After the Q/T and F.H. treatments, the developed 0.8${\sim}$1.6%Si containing Mo and V free low alloy cast steels showed excellent matrix strengthening effect, hardenability, and weldability, fulfilling the industrial criterion of the mechanical properties for automobile cold pressing die insert.

• Journal of Korea Foundry Society
• /
• v.40 no.3
• /
• pp.76-84
• /
• 2020

The effects of Alloying Element and Heat Treatment on the mechanical properties of ductile cast iron poured into shell stack molds were investigated. The strength and hardness were increased and the elongation was decreased roughly with the increased amounts of tin and copper added, respectively. Those were greatly increased with the increased amount of tin added and the elongation was roughly decreased with it. In the simultaneous addition of copper and tin, the strength and hardness of the tin increased, but the elongation rate decreased. Those were greatly increased and this was decreased with normalizing. In the case of specimens with smaller section sizes during austempering processing, the strength and hardness were higher than those with larger sections, but the elongation rate was lower.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.3
• /
• pp.43-51
• /
• 2000

The effect of time, temperature and gas composition on the case hardened thickness, hardness and nitride formation in the surface of ductile cast iron(GCD400) have been studied by micro-pulse plasma technique. Typically, external compound layer and internal diffusion layer which is much thicker than compound layer was observed in the nitride hardening of ductile cast iron. The relative amount kind of phases formed in the nitrided hardening changed with the change of nitriding conditions. Generally, only nitride phases such as $\gamma^'$($Fe_4N$), or $\varepsilon$($Fe_{2-3}N$) phases were detected in compound layer by XRD analysis. The thickness of compound layer increased with the increase of nitrogen content in the gas composition. The optimum nitriding temperature was obtained at $520^{\circ}C$. The nitrided hardening thickness parabolically with nitriding time(t) and thus, the case hardened layer(d) fits well with the typical parabolic equation ; d=kt. The material constant k for GCD400 nitrided at $520^{\circ}C$ was $0.04919\times10^3{\mu}m.hr^{-1/2}$.

• Journal of the Korean Chemical Society
• /
• v.7 no.1
• /
• pp.51-57
• /
• 1963

It is well known that the graphite flakes become spherulite, when a suitable amount of nodulizing element, such as cerium or magnesium, is added to the cast iron. The change of graphite from flake to nodular shape improves not only the tensile strength but the ductility as well. However, the mechanism of spheroidization of graphite in cast iron has not yet been clearly understood, and various theories proposed by a number of investigators were such that it may be due to the special nucleation effect, prevention of flake formation by the adsorption of magnesium vapour on the graphite surface or file surface free energy difference between plain graphite and magnesium-adsorbed graphite. Regardless of the speculations of spheroidizing mechanism of the graphite in the cast iron, the final phenomenon comes to the conclusion that it may be due to the lack of wettability between graphite and iron matrix. In order to collaborate this fact through an experimental method, the authors have constructed a vacuum arc furnace for the wettability measurement as its first step. Our study and experiments were then directed to the comparison of the wettability between iron and graphite on the two cases (namely, the one where magnesium was preliminarily coated on the graphite surface and the other not coated), by means of contact angle measurements. The result was such that a significant difference of the contact angles has been shown between the above two cases. indicating the spheroidization of graphite which might have resulted from the lack of wettability between magnesium-adsorbed graphite and iron matrix.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.6 s.237
• /
• pp.815-821
• /
• 2005

Biaxial low cycle fatigue test was carried out to predict fatigue life under combined axial-torsional-loading condition which is that of in-phase and out-of-phase for CF8M cast stainless steels. Fatemi-Socie(FS) parameter which is based on critical plane approach is not only one of methods but also the best method that can predict fatigue life under biaxial loading condition. But the result showed that, biaxial fatigue life prediction by using FS parameter with several different parameters for the CF8M cast stainless steels is not conservative but best results. So in this present research, we proposed new fatigue life prediction parameter considering effective shear stress instead of FS parameter which considers the maximum normal stress acting on maximum shear strain and its effectiveness was verified.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.3
• /
• pp.331-337
• /
• 1999

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules welding reparis of cylinder block made of cast irons are generally not permitted. However such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the clinder blocks made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding meth-ods of packing seat and o-ring seat of cylinder block and apply them to the practice. The following conclusions are botained :1 The tensile strength of weld of cast iron more than that of base metal can be obtained by means of preheating keeping temperature above $100^{\circ}C$ between welding pass-es preventing slag inclusion peening and cramping weld metal by studs. 2. The suspected crack by a magnetic particle test due to different magnetic permeability can be identified which are not associated with a mechanical discotinuity.

• Journal of Korea Foundry Society
• /
• v.16 no.2
• /
• pp.141-148
• /
• 1996

In high chromium cast iron, the control of matrix microstructure as well as carbide structure is important to the performance as a wear resistant material. In this study, 3.0% C-24.0% Cr white cast irons with various molybdenum contents(residual, 1.0%, 3.0% and 5.0%) were solidified conventionally and unidirectionally for studying their effects on the microstructure and hardness. In the conventional casting, two sets of castings were poured from each melt. One set of the castings consisted of cylindrical bars of 10 and 20mm by 155mm long. The second set of the castings was a cylindrical bar of 30mm by 200mm long. On the other hand, a pep-set mold set on the Cu plate was employed to make the solidification unidirectionally. X-ray diffraction method was used to observe retained austenite and carbides in the high chromium cast iron. The morphology of eutectic $M_7C_3$ carbides changed from needle-like type to nodular type with the increase of Mo content. And, the presence of $M_2C$ carbides was identified in the sample where Mo was added over 3.0 %. Primary and eutectic carbides appeared as rod type and corngrain type, respectively in the unidirectionally solidified samples which were cut to parallel to the solidification direction. In the EDX analysis, Cr concentration was higher in the primary and eutectic $M_7C_3$ carbides, Mo in the $M_2C$ carbides, and Fe in the matrix.

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

• Korean Journal of Materials Research
• /
• v.11 no.4
• /
• pp.300-304
• /
• 2001

Effect of Cd addition on the fatigue properties of Al-Cu-Mn cast alloy was investigated by low and high cycle fatigue tests. With increasing Cd content, fatigue life and tensile strength were increased. It was found that the fatigue strength was 115MPa and the fatigue ratio was 0.31. Metallographic observation revealed that the fatigue crack initiated at the surface and propagated along the grain boundary. This propagation path was attributed to the presence of PFZ along the grain boundary. The tensile strength increased from 330MPa in the Cd-free Al-Cu- Mn cast alloy to 401MPa in the 0.15%Cd-containing alloy.