• Journal of Korea Foundry Society
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• v.34 no.3
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• pp.94-99
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• 2014

A commercially used Zr-based amorphous alloy was recycled and the effects of introducing carbon during recycling on the glass forming ability and mechanical properties of the alloy were investigated. The initial carbon content used in this study was 229ppm. The carbon content was gradually increased as the number of recycling iterations was increased and after the $4^{th}$ recycling it rapidly increased. As return scrap was recycled, polygonal particles precipitated, and they were identified as ZrC. The amount of the precipitates also increased with recycling. Tg, Tx and ${\Delta}T$ of the base alloy were 615 K, 696 K and 81 Kr respectively and they changed to 634 K, 706 K and 72 K after the $10^{th}$ recycling. The decrease of the ${\Delta}T$ value indicates deterioration of the glass forming ability. Hardness was not changed during three iterations of recycling but after the $4^{th}$ recycling it significantly increased. This is ascribed to an increase of amount of the hard particles, namely ZrC.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.85-96
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• 2020

The effect of an aluminum scrap addition ratio on the tensile and solidification cracking properties of the AC4A aluminum alloy in the as-cast state and heat-treated state were investigated in this study. Generally, the expected problem of using scrap in aluminum casting is an increase of hydrogen and Fe element inside the aluminum melt. Another issue is an oxide film which has a weak interface with the molten aluminum and acts as potent nucleation sites for internal porosity and crack initiation. Solidification cracking is one of the critical defects that must be resolved to produce high quality castings. A conventional evaluation method for solidification cracking is a relative and qualitative analysis method which does not provide quantitative data on the thermal stress in the solidification process. Therefore, a newly designed solidification cracking test apparatus was used in this study, and the device can provide quantitative data. As a result, after conducting experiments with different scrap addition ratios (0%, 20%, 35%, 50%), the tensile strengths and elongations in the as-cast state were 214, 187.7, 182.1 and 170.4MPa and 4.6%, 3.4%, 3.1% and 2.3%, respectively. In the case of the T6 heat-treated state, the tensile strengths and elongations were 314.9, 294.6, 293.1 and 271.1MPa and 5.4%, 4.6%, 3.8% and 3.1%, respectively. The strength of the solidification cracking was 3.1, 2.4, 2.2and 1.6MPa as the scrap addition ratio increases.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.1-8
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• 2017

Fe-9.8Si-6.0Al mother alloy was manufactured using by Fe-3.5Si recycled scrap and Si powder. And then, soft magnetic alloy powder of $D_{50}$ size and sphere type were prepared by gas atomization process. To obtain the soft magnetic powder of a high aspect ratio, in the first, we conducted the ball milling process for 8 hours. And heat treatment was performed under $650^{\circ}C$, 2 hours and $N_2$ atmosphere condition for reducing the residual stress of the powder. Based on these process, we made around $50{\mu}m$ diameter Fe-9.8Si-6.0Al powder, which morphology and shape was a similar to the commercial Fe-Si-Al powder. Finally, the soft magnetic sheets were prepared by tape casting process using by those powders. The permeability of the tape casting sheet was measured, and we confirmed the possibility of reusing to the soft magnetic materials of Fe-Si electric sheet scrap.

• Journal of Adhesion and Interface
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• v.9 no.2
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• pp.16-23
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• 2008

In this study, novel waste wool/polypropylene NFRPs (natural fiber reinforced polymer composites), which are constituted with waste wool discarded as industrial scrap during manufacturing processes of woven fabrics and general purpose thermoplastic polypropylene (PP), were fabricated by means of compressionmolding and their mechanical and thermal properties were characterized. The mechanical properties of PP resin were significantly improved by an introduction of waste wool to PP. In particular, as the loading of waste wool was 50 vol% in the NFRP, the flexural strength of the NFRP was increased about 20%, the flexural modulus about 143%, the tensile strength about 76%, and the tensile modulus about 90% in comparison with each of PP control. In addition, the maximum value of the heat deflection temperature (HDT) obtained with the NFRP was $138^{\circ}C$ at a 50 vol% loading of waste wool. This is $21^{\circ}C$ higher than the HDT of PP control. The result here suggests that waste wool be a potential candidate for a reinforcing material of thermoplastic matrix resins.

• Resources Recycling
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• v.11 no.4
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• pp.11-16
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• 2002

Analysis and separation of constituent materials of old car have been performed by using the industrial shredding line. For this aim, three old cars made by domestic automobile manufacturers, Sonata II, Sephia and Prince were chosen and delivered in pressed form without engine, tires and doors, etc. Shredding line was substantially composed of pre- and main-shredder. cyclone, magnetic separation, eddy current separation and man-power separation. From the separation of shredder products, iron scrap was observed to be the major material of old car accounting for 60.1 ％ of total weight and non-ferrous metals involving Al, Cu and Zn, etc. were about 2％. Light fluff, about 90％ of total fluff product, was comprised with plastic, fiber and sponge, etc. and the fraction of 5 cm undersize in light fluff was 70.5%. In case of heavy fluff, however. rubber and plastic were found to be the major constituent materials of it. Among the constituent materials of fluff, plastic showed the highest calorific value, more than 10,000 cal/gr and leather and rubber showed relatively high chlorine content, 10.3 and 2.55 wt%, respectively.

• Resources Recycling
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• v.21 no.3
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• pp.56-64
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• 2012

It is generally well known that PCB (Printed Circuit Board) is an electric component assembled by various metals mixed with plastics and ceramics. Accordingly, it is very important to extract metallic components from used PCBs from the point of view of recycling of used resources as well as an environmental protection. In this paper, patents and paper on the recycling technologies of PCB were analyzed. The range of search was limited in the open patents of USA (US), European Union (EP), Japan (JP), Korea (KR) and SCI journals from 1980 to 2011. Patents and journals were collected using key-words searching and filtered by filtering criteria. The trends of the patents and journals was analyzed by the years, countries, companies, and technologies.

• Journal of Korea Foundry Society
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• v.36 no.2
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• pp.67-74
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• 2016

The effects of scrap content on the hot tearing property and tensile property were investigated in AC2BS alloy. The hot tearing strengths were $16.4kgf/cm^2$, $15.2kgf/cm^2$, $14.9kgf/cm^2$ and $13.3kgf/cm^2$, respectively, under the constant solid fraction of 29.3% when the scrap contents of the specimens were 0%, 20%, 35% and 50%. In the same way, tensile strengths of the as-cast condition were $24.5kgf/mm^2$, $23.7kgf/mm^2$, $17.3kgf/mm^2$ and $16.0kgf/mm^2$, respectively, and the corresponding tensile strengths of the T6 heat treatment condition were $27.2kgf/mm^2$, $26.7kgf/mm^2$, $24.2kgf/mm^2$ and $23.9kgf/mm^2$. Hot tearing strength and tensile strength decreased as scrap content of the specimen increased. According to the evaluation of the quantitative hot tearing and tensile test results, the decrease of these strengths is due to the presence of oxide films which act as crack initiation site of the specimens. Therefore, elimination of oxide films of aluminum melt to maintain melt cleanliness is required.

• Korean Journal of Materials Research
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• v.13 no.4
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• pp.239-245
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• 2003

In order to explore the possibility to extract precious metals from PCB(Printed Circuit Board) scrap by gravity separation, a high temperature melting process was adopted, from the recycling view point, to investigate the influence of viscosity on A1$_2$$O_3$-CaO$-SiO_2$ slag system composed of PCB scrap. For optimizing the pre-treatment process of PCB scrap, an experimental condition for the complete calcination and oxidation of organic materials in PCB scrap was established and a quantitative analysis of oxidized PCB scrap was also carrie out. It was found that 6 hours were enough for the complete oxidation of PCB scrap at 1273 K in an atmosphere condition. A slag, l5wt%$A1_2$$O_3$-45wt%CaO-40wt%SiO$_2$, was chosen as a basic slag composition which is determined based on the quantitative analysis of PCB scrap. Viscosities were measured in slag systems both made from pure fluxes and from PCB scrap with additional fluxes. Slag viscosities composed of pure fluxes were measured to be 5.29 poise and 30.52 poise at temperatures of 1773 and 1573 K, whereas that of PCB scrap with additional fluxes were 3.37 poise and 69.89 poise, respectively.

• Journal of the Korean Applied Science and Technology
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• v.25 no.1
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• pp.58-64
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• 2008

Pretreatment of eliminating FFA is needed to make biodiesel from animal fat recovered from leather wastes because its acid value is high. This study was carried out to investigate the influence of 4 different pretreatment methods, which are heterogeneous catalyst method, ion exchange resin method, low pressure.high temperature method, and alkali method on the eliminating FFA and fatty acid composition. The results showed that the rate of eliminating FFA increased in the order of alkali method > catalyst method > low pressure high temperature method > ion exchange method. In the case of pretreatment of alkali method using NaOH, the rate of eliminating FFA appeared more than 86% regardless of acid value. Therefore, it was considered that alkali method using NaOH was the most effective in the view of economical and productive aspects, taking it into account that the acid value of animal fat recovered from fleshing scrap generated during leather making processes was 7 to 8.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.267-273
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• 2012

This study is performed to evaluate the flexural performance of reinforced concrete columns with electric arc furnace oxidizing slag aggregates. Electric arc furnace slag is a by-product obtained from the process of refining scrap steel. The electric arc furnace slag can be used as a concrete aggregate, because it mainly consists of CaO and $SiO_2$, similar to natural rocks and minerals. Three rectangular columns with various types of aggregate were cast to test in flexure. All of the test specimens had a cross-section of $250{\times}250$mm and a height of 1,500 mm in test region. The specimens were designed to apply reversed cyclic antisymmetric moment and constant axial force. The experimental results showed that the specimens with electronic arc furnace oxidizing slag aggregates had superior flexural performance than the specimen with natural aggregates.