• Journal of the Korean Institute of Gas
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• v.7 no.2 s.19
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• pp.22-32
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• 2003

Al-brass material is generally used at the state of plastic deformation, for example; bending, extension of bell mouth at shell and tube type heat exchanger. And SCC(stress corrosion cracking) of Al-brass material will be affected by residual stress as plastic deformation. SCC results from synergism between mechanical factor and corrosion environment. Mechanical factor is stress that directly relates with stress intensity factor at the crack tip. This paper was studied on the effect of stress on SCC of Al-brass tube under in $3.5\%$ NaCl. + $0.1\%\;NH_4OH$ solution by constant displacement tester. Increasing of acidified water flow into sea and speeds up corrosion rate of Al-brass which is used as a tube material of vessel heat exchanger by polluted coast seawater. The experimental results are as follow The latent time of SCC occurrence gets longer as the initial stress intensity factor($K_{Ii}$) gets lower The main crack was propagated as the initial stress intensity factor($K_{Ii}$) gets higher, and secondary cracks occurred by electro-chemical factor a(ter stage of released stress. Dezincification phase showed around the crack, and the range of dezincification gets wider as the initial stress intensity factor($K_{Ii}$) gets higher.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.291-297
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• 2003

Al-brass is usually used as the tube material of vessel's heat exchanger for seawater cooling system because it has high thermal conductivity and good mechanical properties and high corrosion resistance due to cuprous oxide (Cu20) layer against seawater. However, Al-brass tubes of heat exchanger for vessel at the actual environment is reported that local corrosion such as stress corrosion cracking occurred by synergism effect between mechanical factor and corrosion environment In this paper, the effect of corrosion environment on the stress corrosion cracking of Al-brass in various NH4OH of 3.5% NaCl solution, under flow by constant displacement tester. Based on the test results, the behavior of polarization, stress corrosion crack propagation and dezincification phenomenon of Al-brass are investigated. The main results are as follows：(1) Increasing range of potential from open circuit potential to repassivation gets lower, as the contain rate of NH4OH gets higher. (2) As contain rate of NH4OH gets higher, SCC of Al-brass is become activation but the protection film(Cu20) of Al-brass is created in 3.5% NaCl solution. (3) According as content of NH4OH increases in 3.5% NaCl solution, the dezincifiction area is spread. It is concluded that dezincification occurred by localized preferential anodic dissolution at stress focusing region.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.05a
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• pp.19-20
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• 2000

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.69-74
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• 2004

In general, the protection method of Shell and Tube Type heat exchanger for a vessel has been applied as a sacrificial anode, which is attached at the inner side of the shell. However, this is an insufficient protection method for tube. Therefore, a more suitable method, such as the impressed current cathodic protection for tube protection, is required. Al-brass is the raw material of tubes for heat exchanger of a vessel where seawater is used for cooling the water. It has a high level of heat conductivity, excellent mechanical properties, and a high level of corrosion resistance, due to a cuprous oxide (Cu$_2$O) layer against th seawater. However, in actuality, it has been reported that Al-brass tubes for heat exchanger of a vessel can produce local corrosion, such as stress corrosion cracking (SCC). This paper studied the effect of impressed potential on the stress corrosion cracking of Al-brass for impressed current cathodic protection in 3.5% NaCl +0.1% NH$_4$OH solution, under flow by a constant displacement tester. Based on the test results, the latent time of SCC, stress corrosion crack propagation, and the dezincification phase of Al-brass are investigated.

• Proceedings of the KWS Conference
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• v.43
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• pp.194-195
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• 2004

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.162-163
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• 2021

그래핀수지로 기존에 황동(Ni-Al-Bronze) 프로펠러 대체 가능 제품의로 고가의 황동을 그래핀수지 특히 재생 플라스틱 활용으로 저가로 공급 가능하다. 또한, 재활용이 가능한 친환경 프로펠러임, 가벼운 소재를 이용하여 연료 효율 증대, 연료 효율을 향상시켜 연안해운 저탄소 실현, 마찰저항을 최소화하여 선박의 추진성능 개선, 해양생물 부착 방지(방오기능)를 통한 프로펠러 수명연장 기대, 프로펠러 검사 및보수 유지비용 절약 기대, 향후 폐기물에 그래핀을 혼합한 재생 자재로 활용 가능이 크다.

• Journal of the Korean Institute of Gas
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• v.5 no.2 s.14
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• pp.14-21
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• 2001

In order to investigate the damage mechanism of the coupler transferring LPG, microstructural observation and chemical analysis of the couplers operated for the long time in the LPG stations and virgin 6/4 forged-brass corrosion-tested were conducted. Their microstructure was consisted of two phases that bright $\beta$ precipitates were irregularly dispersed in $\alpha$ matrix. The chemical compositions of oxide layer on the surface of the used coupler were composed of S, C, O, Al, Si, etc. as well as Cu and Zn. In environmental corrosion tests of both $10\%$ HCl and Mattsson solutions, no apparent deviations in mechanical impact strength of forged-brass was observed. While, in U-bend stress corrosion cracking specimen, some microcracks were observed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.399-406
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• 2006

The natural frequencies of Al square plates with a brass inclusion were analyzed by the rule of mixtures. The rule of mixtures is the method to derive natural frequency mutiplying effective inplane wane speed and nondimensional frequency parameters. Numerical models were Al square plates with an inclusion with cantilever type, 2 clamped edge-2 free edge type, 3 clamped edge-1 free edge type and fully clamped edge type. In cantilever type plates, 2 clamped edge-2 free edge type plates and 3 clamped edge-1 free edge plates with an inclusion, good agreement within 10% obtained from rule of mixtures' results and numerical analysis results within inclusion area ratio 1/9. It was found that the natural frequencies of the cantilever type, 2 clamped edge-2 free edge type and 3 clamped edge-1 free edge type plates with an inclusion decrease as the size of inclusion increases when inclusion is located center of plates. And when the density of inclusion is less than the plates, natural frequency of plates with an inclusion increases as the size of inclusion increases.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.117-120
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• 2002

The addition of minor alloying elements such as Al, Si, Mg, Cr, Zr, and Sn changed the microstructure and the oxidation characteristics of the Cu-40%Zn alloys. Detailed microstructure, scale morphology and the oxidation mechanism were described.

• Journal of Korea Foundry Society
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• v.19 no.6
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• pp.484-492
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• 1999

The microstructures and mechanical properties of high strength yellow brass, Al bronze and Sn bronze alloys fabricated by gravity die casting and squeeze casting were investigated. A rapid cooling of casting was enhanced by pressure applied during solidification of Cu alloys, the cooling rate of casting was more great for high strength yellow brass alloy than other Cu alloys. Grain size and phases of the squeeze cast products become refined to 1/2 level compared to gravity die castings. Squeeze cast Al bronze and high strength yellow brass has about 10-20% higher yield and tensile strength and slighter decreased or nearly same elongation, compared to gravity die cast ones. Sn bronze has nearly same strength and hardness, but shows increased in elongation, compared to gravity die cast ones.