• Transactions of Materials Processing
• /
• v.15 no.8 s.89
• /
• pp.586-590
• /
• 2006

42Ni-Fe Invar alloy strips were fabricated using conventional ingot casting and melt drag casting followed by rolling. Mechanical properties such as tensile strength, elongation and blanking deformability of the strips were evaluated. The properties were strongly depended on fabrication methods. Tensile strength and elongation of all strips were in the range of $40-60kg/mm^{2}$ and 26-35%, respectively, which are enough values for the manufacture of the final products. In some of the strips, however, burrs occurred at deformed surface. The properties of strips were explained in terms of microstructure such as grain size and texture formation during rolling. Additionally, strips by melt drag casting method were compared to those by conventional ingot casting.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1995.10a
• /
• pp.102-108
• /
• 1995

Internal contact scheme between two free surfaces on one deforming body has been proposed by using the penalty method. It has been imposed to be internal boundary condition on two-dimensional thermo-viscoplastic finite element method so as to analyze one deforming body, which has two free surfaces penetrating each others. Analysis of side pressing with a circular void and a inclined elliptic hole have been carried out in order to verity the proposed contact scheme. A finite element code imposed internal boundary condition has been applied to two-dimensional analysis of free forging of large ingot with a void. Through the analysis, effects of working parameters in order to consolidate voids have been investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1997.06a
• /
• pp.183-195
• /
• 1997

The micorstructural characteristics, particularly $\alpha$-halo formation, in semi-solid state processed hypereutectic Al-Si alloy was investigated. The microstructural changes during reheating of wedge type mold cast ingot, hot-rolled sheet, and Si particulate reinforced Al composite was compared with those occurred during stirring of semi-solid state hypereutectic alloy. In the case of semi-solid state reheating of wedge type ingot and hot-rolled sheet, fine particles of Si as well as $\alpha$-halo formed after heat treatment. Although there seemed to be no coarsening with variations of holding time, the region of $\alpha$-halo decreased due to homogenization. Nucleation and recrystallization was accelerated with the addition of alloying elements during hot rolling resulting in primary Si particle size decrease and $\alpha$-halo formation. In the case of extruded specimens, very little morphological change of reinforcing Si particles was observed. Almost no $\alpha$-halo formed during reheating because of the oxide film formed on the reinforcing Si particles which acted as a diffusion barrier between the matrix and the primary Si particles.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.964-968
• /
• 1996

The demands of size and quality of large steel shaft forgings for ship building, power plant, steel plant, etc. are rapidly increasing, and some of these productions are manufactured from ingot weighing more than 300 tons. For use as rotating components. shafts require toughness, strength and homogeneity, and therefore are produced through a variety of heat treatments. According to the increase of ingot size, micro- and macrosegregation and also mass effect of the product increase. Thus, special care should be paid to the heat treatment of such large shaft forgings. In this paper, the heat treatment of large shaft forgings such as rotor and back-up roll is calculated using the commercial finite element code SYSWELD. Calculated distributions of temperature and phase are compared with experimental data. The continuous cooling transformation diagram, thermal and mechanical properites of each phase are used. The phase proportion, hardness and residual stress during water quenching are discussed.

• Journal of Korea Foundry Society
• /
• v.22 no.1
• /
• pp.35-41
• /
• 2002

To improve the reliability of solder joints, a composite solder which consists of solder matrix and intermetallic reinforcements was manufactured by a new method. The cast ingot of Sn-6.9Cu-2.9Ag alloy had primary Cu6Sn5 intermetallics in the form of dendrites. After rolling the ingot, the intermetallic dendrites were crushed into fine particles and distributed uniformly throughout the solder matrix. As the rolled strips became thinner, the average size of the crushed particles reached a critical size which did not decrease any more by further rolling. The critical size was nearly the same as the average width of intermetallic dendrite trunk. The crushed intermetallic particles did not melt and remained in solid state during reflow soldering due to their high meltingterm-perature. The coarsening and gravitational segregation of the particles were observed during reflow soldering.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.94-97
• /
• 2009

Cast defect in large steel ingots are estimated in quality and compared each other cast conditions on simulation results by now. The cast defects, micro-crack, shrinkage, pin hole which are predictable in simulation with a reasonable accuracy. In this study, 15 ton steel ingot casting was simulated for solidification model and cast defect prediction. And the real cast was carried out in a foundry for the compeer to the simulation results, the cast defect prediction. Also, the quantity of predicted defect was tried to measuring with the defect mach counting for the various simulated cast conditions. The defect quantity work was used to find the optimized cast condition in DOE(design of experiment) procedure.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.05a
• /
• pp.479-482
• /
• 2005

To improve the efficiency of fossil power plant, the higher steam temperature and pressure are required. Ultra super critical(USC) system meets very well this requirement. The HIP rotor is one of the most important parts of turbine in USC system and its material is easy to crack during hot forging. In this study, the upsetting and cogging process far $12\%Cr$ ESR ingot was analyzed and it is suggested a optimum process to avoid surface crack. The results were verified by test product with 4,200 tonnage press.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.05a
• /
• pp.71-74
• /
• 2008

In order to resolve the problems which appear after the clean large ingot production process, the impurities which are involved in the steel smelting process should be removed by developing cleaner materials. Through the rationalization of cogging process that is the first forging process of large ingot the quality is to be improved. For the sake of the optimization of an open die forging process and the improvement of the subject matter frequency ratio, a hazard precise die forging process must be developed and a Near Net Shape Forming accomplished. As a result, energy can be reduced by minimizing an after control process. In order to produce large axes and other forming parts, processing techniques are to be developed. In this context, this paper is a study about a reduction ratio, dies width ratio and rotary angles, the amount of overlap, and intends to analysis cogging processes, utilizing Deform-3D cogging module

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1999.11a
• /
• pp.48-48
• /
• 1999

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2005.06a
• /
• pp.396-397
• /
• 2005