• Journal of Korea Foundry Society
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• v.38 no.6
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• pp.121-131
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• 2018

The effect of additives on the castability of the AC2BS aluminum alloy, which contains 35% recycled scrap, was investigated. For the wide utilization of the recycled scrap AC2BS aluminum alloy, the research results were compared to those with the AC2B virgin alloy, which is typical Al-Si-Cu alloy system. It was confirmed that the addition of Al-5%Ti-1%B increased the ${\alpha}$-Al nucleation temperature during solidification and decreased the grain size through cooling curve and microstructural observations of the recycled alloy. It was also found that an addition of Al-10%Sr decreased the eutectic Si growth temperature during the solidification process and modified the shape of the eutectic Si of the recycled alloy. The characteristics of fluidity, shrinkage and solidification crack strength were evaluated. For the AC2BS aluminum alloy containing 35% recycled scrap, both ${\alpha}$-Al grain refinement due to Ti-B and eutectic Si modifications due to Sr contributed to the improvement of the fluidity. The macro- shrinkage ratio increased with additions of both Al-10%Sr and Al-5%Ti-1%B and the micro-shrinkage ratio increased with the addition of Al-10%Sr but decreased with the addition of Al-5%Ti-1%B. The casting characteristics of TiB and Sr-treated AC2BS aluminum alloy containing 35% recycled scrap are similar to those of AC2B virgin alloy. The improvement of the solidification crack strength of the AC2BS aluminum alloy was possible by the reduction of the grain boundary the stress concentration through the enhancement by both ${\bullet}{\cdot}$-Al refinement and eutectic Si modification. More extensive use of the AC2BS aluminum alloy containing 35% recycled scrap can be expected in the future.

• Journal of Korea Foundry Society
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• v.29 no.2
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• pp.59-63
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• 2009

Effects of Ti on damping capacity and mechanical properties are investigated in hot rolled Fe-17%Mn alloy. The existing damping alloy with Fe-Mn binary system was limited the use by high production cost, however in case of using scrap iron instead of pure iron although the content of carbon is higher it is possible to be applied wider field especially construction items because the production cost is lower. However, the excellent specific damping capacity is dropped due to the high content of carbon, we developed advanced type of damping alloy included Ti. TiC is formed with added Ti and it holds the specific damping capacity similar to existing damping alloy. The effect of Ti on damping capacity is found to be beneficial in carbon-containing alloy, which is attributed to the depletion of carbon solute due to the formation of TiC.

• Journal of Korea Foundry Society
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• v.38 no.5
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• pp.87-94
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• 2018

The effects of Sr and (Ti-B) additives on the tensile properties of AC4A recycled (35% scrap content) aluminum alloys were investigated. An acicular morphology of the eutectic Si phase of as-cast specimens was converted to a fibrous morphology upon the addition of Sr. Moreover, morphology of the Sr modified eutectic Si phase became finer due to a T6 heat treatment. The grain size of the ${\alpha}$-solid solution was decreased by the addition of (Ti-B) additives. Depending on the treatment conditions of the as-cast specimens, i.e., no addition, a Sr addition and a (Ti-B)+Sr addition, the tensile strength levels of the as-cast specimens were 182, 192, and 204MPa, respectively. The corresponding strengths of T6 heat-treated specimens were 293, 308, and 318MPa. Elongations of the as-cast specimens were 2.2, 3.1, and 5.6%, and the corresponding elongations of the T6 heat-treated specimens were 4.6, 6.1, and 7.6%. The percentage of the reduced section area in the tensile specimens was also increased by the Sr and (Ti-B) additives. Sr and (Ti-B) additives changed the microstructure and the distribution of defects in the castings, resulting in an improvement of the tensile properties of AC4A aluminum alloys. According to our test results, recycled (35% scrap content) AC4A aluminum alloy met all of the KS requirements of the tensile strength and elongation values of AC4A aluminum alloy except for the elongation value of the one specimen condition, in this case the as-cast no-addition condition.

• Journal of Korea Foundry Society
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• v.39 no.4
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• pp.61-74
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• 2019

The effects of Sr and (Ti-B) additives on the impact and fatigue properties of recycled (35% scrap content) AC4A aluminum alloy are investigated here. The acicular morphology of the eutectic Si phase of as-cast specimens was converted to the fibrous one with Sr additives. The grain size of the α-solid solution decreased by the addition of (Ti-B) additives. The crack initiation energy (E_i) of the impact absorption energy decreased due to the incorporation of an oxide film and inclusions depending on the scrap used. The modification of the eutectic Si morphology by Sr additives is considered as the main factor of the increase of the average impact absorption energy (E_t). The addition of (Ti-B) additives contributed to an increase in the occurrence of crack deflections due to the refining of α-Al grains, resulting in improved fatigue properties.

• Journal of Korea Foundry Society
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• v.41 no.2
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• pp.139-143
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• 2021

A type of titanium alloy, ferro-titanium, is the main material used to manufacture steel and stainless steel. Considering economic aspects, ferro-titanium ingots are intended to be manufactured using low-cost titanium scrap, and the best pretreatment process for removing impurities from recycled titanium scrap surfaces was studied here. Instead of ordinary acid or organic solvents, ecofriendly methods were researched and applied, and chip scrap materials were used. A high-quality ferro-titanium ingot was manufactured from titanium scrap after a pretreatment process was applied, and the impurities and properties were analyzed and compared with commercial material standards through a component analysis.

• Clean Technology
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• v.19 no.2
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• pp.75-83
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• 2013

In the present paper, we review recycling and applications of titanium binary alloy scraps. The recycling techniques are to successfully prepare low oxygen content ingots using hydrogen plasma arc melting (HPAM) and to produce low oxygen content titanium alloy powders by Hydrogenation-dehydrogenation (HDH) and Deoxidation in solid state (DOSS) process. In addition, as applications of the titanium binary alloy scraps, Ti based solid-solution carbide powders, which would be used for producing Ti based solid-solution cermets with high toughness, were prepared using the titanium binary alloy scraps. These results confirmed that the titanium alloy scraps could be recycled and refined using the HPAM. The resulting oxygen content of the titanium alloy powders were below 1,000 ppm after powderizing. Finally, we had confirmed that the refined titanium alloy powders were able to be utilized as raw materials for preparing the toughened cermets.

• Resources Recycling
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• v.26 no.6
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• pp.3-9
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• 2017

In this study, plasma arc remelting behaviors according to arc current, arc voltage, and types of plasma gas were investigated using Kroll processed Ti sponges as anode. In the discharge pressure range of vacuum pump ($200{\sim}300kgf/cm^2$), the arc voltage did not vary greatly with the increase of discharge pressure at a given arc length. This means that the pressure in the vacuum chamber during operation hardly changes and the atmospheric pressure maintains. Under various conditions of arc currents (700~900A), the arc voltage slightly increased with arc current. The effects of anode materials and operational variables on the arc length-arc voltage relationship were compared with the results in previous studies. When the atmospheric gas changed from argon to helium, double effect of improvement on the output of the steady state was observed. The increase of output in the plasma arc device was accompanied by an increase in the melting rate of the Ti sponge and the quality of the ingot surface was also improved. The plasma arc remelting of the new scrap titanium and the old scrap zirconium alloy could result in the fabrication of an ingot with high surface quality.

• Resources Recycling
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• v.21 no.1
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• pp.60-65
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• 2012

The Ti-6Al-4V alloys were prepared by recycling of dental Ti pure scraps using vacuum arc melting process, and their physical properties were evaluated the Ti-6Al-4V alloys with different oxygen concentrations. For the preparation of Ti-6Al-4V alloys, Ti pure scraps used for dental implant were utilized as a raw material, and their different oxygen concentrations were ranged from G1 to G4 grade in ASTM standards. It was confirmed that the weight loss of Al in the composition of Ti-6Al-4V alloy could be controlled under the Ar pressure of 875 torr during the melting of alloy. The oxygen concentrations of the Ti-6Al-4V alloys were ranged from 1170 to 3340 ppm. The vickers hardness change of the Ti-6Al-4V alloys showed a similar behavior with that of pure Ti. As a result, we confirmed a possibility of preparation of Ti-6Al-4V alloy by recycling of dental Ti scraps using vacuum arc melting process in this study.

• Analytical Science and Technology
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• v.8 no.1
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• pp.85-90
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• 1995

Corrosion characteristics of 4 kinds of the Fe-Al damping alloys has been studied in the 3.5% NaCl solution and compared with a cold rolled mild steel and pure Ti, No passivation, besides Ti, was observed in the Fe-Al damping alloys and a cold rolled mild steel. Corrosion rate was decreased with lower carbon concentration. In the case of Mn addition for improving damping capacity, corrosion rate was decreased in scrap iron but was not decreased in electrolytic iron. It has been shown that corrosion rate of Fe-Al damping alloys lays between that of the pure Ti and that of a cold rolled mild steel.