This study is aimed to analyze the economic feasibility of yellowtail culture using the copper alloy net cage in Gyeongsangbuk-do. First of all, in order to evaluate the copper alloy net cage on yellowtail culture, I review the trend on the yellowtail culture industry and research the concept of copper alloy net cage. The copper-alloy net cage is now recognized as an advantages of its system stability, recycling, antibiosis and food safety. The results were summarized as follows: first, there was significant meaning of the profit model of yellowtail culture by the price difference. Second, I analyzed in the economic feasibility of yellowtail culture using the copper alloy net cage, internal rate of return (IRR) was 51.58%, a benefit-cost ratio was shown to be 2.27 and net present value (NPV) was 1,087,337 thousand won, which indicates the economic feasibility of yellowtail culture using the copper alloy net cage is profitable. Finally, in order to improve the economic valuation, it is necessary to focus more on the developing of technology and cost reduction strategy on the copper alloy net cage.

Alumina dispersion strengthening copper(ADSC) alloy has great potential for use in many industrial applications such as contact supports, frictional break parts, electrode materials for lead wires, and spot welding with relatively high strength and good conductivity. In this study, we investigated the oxidation behavior of ADSC alloys. These alloys were fabricated in forms of plate and round type samples by surface oxidation reaction using Cu-0.8Al, Cu-0.4Al-0.4Ti, and Cu-0.6Al-0.4Ti(wt%) alloys. The alloys were oxidized at 980 oC for 1 h, 2 h, and 4 h in ambient atmosphere. The microstructure was observed with an optical microscope(OM) and a scanning electron microscope(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS). Characterization of alumina was carried out using a 200 kV field-emission transmission electron microscope(TEM). As a result, various oxides including Ti were formed in the oxidation layer, in addition to γ-alumina. The thickness of the oxidation layer increased with Ti addition to the Cu-Al alloy and with the oxidation time. The corrected diffusion equation for the plate and round type samples showed different oxidation layer thickness under the same conditions. Diffusion length of the round type specimen had a value higher than that of its plate counterpart because the oxygen concentration per unit area of the round type specimen was higher than that of the plate type specimen at the same diffusiondepth.

본 연구에서는 내식성이 우수한 동합금에 대하여 내구성 향상을 위해 쇼트피닝 시간을 변수로 표면 개질하여 전기화학적 특성과 조직 변화를 관찰하였다. 그 결과 쇼트피닝 후 표면에 전체적으로 요철이 발생하였으며, 시간이 증가할수록 커버리지 향상에 따른 균질화 현상이 관찰되었다. 또한 쇼트피닝된 모든 시험편에서 경도가 향상되었으며, 쇼트피닝 시간이 3.5분일 때 52 %의 경도향상을 나타냈다. 그리고 이때 전기화학적 특성은 쇼트피닝을 실시하지 않은 경우와 유사하였다

The microstructure and mechanical properties of a copper alloy sheet processed by differential speed rolling (DSR) were investigated in detail. A copper alloy with thickness of 3 mm was rolled to a 50% reduction at ambient temperature without lubrication and with a differential speed ratio of 2.0:1. For comparison, conventional rolling (CR), in which the rolling speeds of the upper and lower rolls is 2.0 m/min, was also performed under the same rolling conditions. The shear strain of the sample processed by CR showed positive values at the positions of the upper roll side and negative values at the positions of the lower roll side. On the other hand, the sample processed by the DSR showed zero or positive shear strain values at all positions. However, the microstructure and mechanical properties of the as-rolled copper alloys did not show such significant differences between the CR and the DSR. The samples rolled by the CR and the DSR exhibited a typical deformation structure. In addition, the DSR processed samples showed a typical rolling texture in which 112<111>, 011<211> and 123<634> components were developed at all positions. Therefore, it is concluded that the DSR was very effective for the introduction of a uniform microstructure throughout the thickness of the copper alloy.

The effects of conventional rolling (CR) and differential speed rolling (DSR) on the microstructure and mechanical properties of a copper alloy sheet were investigated in detail. A copper alloy with thickness of 3 mm was rolled to a 50% reduction at ambient temperature without lubrication with a differential speed ratio of 2:1; sample was then annealed for 0.5h at various temperatures from 100 to 800˚C. Conventional rolling, in which the rolling speed of the upper and lower rolls is identical, was performed under the same rolling conditions. The shear strain introduced by the CR showed positive values at positions on the upper roll side and negative values at positions on the lower roll side. However, the shear strain showed a zero or positive value at all positions for the samples rolled by the DSR. The microstrucure and mechanical properties of the as-rolled copper alloy did not show very significant differences between the CR and DSR for the microstructure and mechanical properties. However, those properties showed very significant differences in the case of the annealed samples. The effects of rolling method on the microstructure and mechanical properties of the as-rolled and subsequently annealed materials are discussed in terms of the shear strain.

Benzotriazole (B.T.A) which has been mainly used for the stabilization processing method of excavated copper and bronze artifacts is vaporized within 2~3 years after the usage because it is unstable at the acid conditions and cannot protect the surface of artifacts. In this study, NaOH method which has been used for the steel artifacts was applied as a stabilization process for the method of copper and bronze artifacts to gush chlorine ion out. For the reproduction of excavated samples, copper and bronze plates were dipped in 0.1M HCl for 26 hrs to form CuCl, rusted at 70˚C with RH 75% for the formation of corrosion products, and desalted in 0.1 M NaOH solution. The concentration of chlorine ion was measured by using ionchromatography. During the desalting process, a large quantity of chlorine ions was gushed out in early period and corrosion products were not additionally generated through the re-corrosion experiment. This NaOH desalting process was found to be a method of stabilization process for copper and bronze artifacts from the formation of Tenorite (CuO) during desalting as a protection layer for corrosion.

The alumina dispersion-strengthened (DS) C15715 Cu alloy fabricated by a powder metallurgy route was annealed at temperatures ranging from in the air and in vacuum. The effect of the annealing on microstructural stability and room-temperature mechanical properties of the alloy was investigated. The microstructure of the cold rolled OS alloy remained stable until the annealing at in the air and in vacuum. No recrystallization of original grains occurred, but the dislocation density decreased and newly formed subgrains were observed. The alloy annealed at in the air experienced recrystallization and grain growth took place, however annealing in vacuum at did not cause the microstructural change. The mechanical property of the alloy was changed slightly with the annealing if the microstructure remained stable. However, the strength of the specimen that was recrystallized decreased drastically.

Recycling technology research in the copper smelting industry is necessary because the recovery of valuable metals from generated waste can offset the cost of raw materials. The cost of imported raw materials, can exert a significant impact on profitability. In order to perform this research review of previous studies about the base characteristics of the target waste was needed. In this study, copper slag and copper alloy smelting slag generated in the process, along with slag, ash, and sludge, were analyzed for particle size, distribution of the waste, physical characteristics, chemical composition, and inclusion of heavy metals. Copper slag and copper alloy particle separation results were able to remove most of the metal pieces that were at least 1 mm in size. In this waste, zinc, copper-containing metal were less than 80%. toxic substances, such as cadmium, arsenic and mercury, were removed by utilizing a hydrometallurgical process. The data suggests that this industry should be able to take advantage of new technologies the recover valuable metals from copper smelting waste.

동 제련 산업의 경우 1960년대까지 소비하는 전량을 수입에 의존하였고, 이후 경제발전과 함께 수요가 대폭증가하면서 국내에서도 동 제련 생산업체가 설립되기 시작하였다. 이와 함께 자동차, 전기･전자, 철강, 건설 및 기계 산업에 주요 기초 소재를 공급하는 역할을 담당하게 되었다. 산업 특성상 수입에 의존하는 원자재의 가격이 수익성에 큰 영향을 미치기 때문에 제련 시 발생하는 폐기물을 이용한 재활용 기술연구가 필요한 실정이다. 국내 동 제련 산업은 원석인 황동광을 파･분쇄하여 제품을 생산하는 1차 동 제련 산업과 폐동스크랩, 폐동파이프 등을 원재료로 하여 동 빌레트, 동 괴, 황동봉을 생산하는 2차 동 제련산업으로 나눌 수 있다. 1차 동 제련산업의 경우 국내 유일업체에서만 생산하고 있으며, 자체 플랜트 사업을 통해 재활용 연구가 활발하게 진행되고 있으나, 2차 동 및 동합금 제련공정의 경우 현재 연구실적이 많지 않다. 공정 에서 발생하는 폐기물에 함유되어있는 Cu, Zn, Pb, Fe 등의 유가금속을 재활용하기 위해서는 반드시 대상 폐기물의 물리･화학적 특성 및 환경성평가가 선행 연구되어야 한다. 본 연구에서는 동 및 동합금 제련공정에서 폐기물의 발생량, 생산제품 등 5개 사업장(C사, D사, S사, P사, H사)을 선정하여 광재, 분진, 오니 폐기물의 기본 특성을 확인하였다. 대상 폐기물의 입도특성, 광물학적 특성 및 화학적 조성을 확인하였고, 입도분포에 따라 광물학적 성상의 변화에 대해 확인하였으며, 대상 폐기물의 중금속 용출･함유량을 확인하였다. 입도특성 결과, C사와 S사 광재의 경우 육안으로 식별 가능하였으며, S,P,H의 광재는 비교적 입도별로 고루 분포되어 있음을 확인할 수 있었다. 입도의 크기가 1 mm 이상에서는 폐기물 내 금속편의 식별이 가능하여 분리가 간편하지만, 1 mm 이하 금속편의 경우 파･분쇄 후 스크리닝(Screening)을 통한 분리공정이 필요하다. 또한 0.1 mm 이하에서 11%의 중량비율을 차지하고 있는 P2시료의 경우 물리적 파･분쇄를 통해 금속편의 회수가 어렵기 때문에 자력선별, 부유선별 등의 습식제련방법을 활용하여 분리해야한다. 황동 원재료 및 황동 제품을 주로 생산하는 D사, H사, P2사의 경우 대부분이 Zn으로 이루어져 있으며, 90% 이상의 높은 함유량을 보이고 있다. 또한 동 빌레트, 동 버스바 및 동 특수합금을 제조하는 사업장의 경우 Cu, Fe. Zn의 함유량이 골고루 분포되어 있어 이를 회수하여 재활용 할 경우 유가금속의 확보와 더불어 대부분의 원자재를 수입에 의존하고 있는 국내 실정에 따라 자체생산에 의한 경제성이 확보될 수 있을 것으로 판단된다. 또한 환경성평가를 통해 높은 용출특성 및 함유량을 지닌 Cd, Hg, As 등의 유해물질이 제거된 폐기물은 공업용 충전제, 절연재, 채움재, 세라믹스 원료 등으로 재활용 확대방안에 기여 할 것으로 판단된다. 본 연구의 동 및 동합금 제련공정 발생폐기물의 입도특성, 광물학적 특성 및 화학적 조성, 유해물질 함유 특성 조사결과를 바탕으로 재활용 및 유가금속의 회수를 위한 기초데이터로 활용할 수 있을 것으로 판단된다.