• Title, Summary, Keyword: 알루미늄합금

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Evaluation of Resistance Spot Weldability of SGAFC1180 Steel (SGAFC1180 TRIP강재의 저항 점용접성 평가)

  • Shin, Seok-Woo;Lee, Jong-Hun;Kim, Dae-Hwan;Park, Sang-Heup
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.12
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    • pp.644-649
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    • 2017
  • In the automobile industry, there is growing demand for lightweight vehicles due to environmental problems and rising oil prices. Therefore, aluminum alloys and special materials are being used to reduce the weight of vehicles, but there are still many difficulties to overcome in terms of cost and strength. Therefore, the application of advanced high strength steel (AHSS)is increasing. AHSS has good strength and formability.Safety regulations are becoming stricter, and 1.2-GPa super-high-strength steels are gradually being applied for the center pillar and roof rails. Thus, the application of different kinds of steels in automobile bodiesis also increasing gradually. This study evaluates the resistance point weldability and the characteristics of a welded part of SGAFC1180 1.2t steel. A simulation was used to observe the nugget formation and its growth behavior. The prediction performance showed a similar tendency within an error rate of 10%. Also, the effect of this behavior on the process resistance and dynamic resistance was investigated,along with the correlation between the shear tensile strength and nugget diameter.

An Electrochemical Evaluation of the Corrosion Properties of the Steel with the Type and the Thickness of Metallizing Coatings (금속용사 코팅제의 종류 및 두께에 따른 강재 내식성의 전기화학적 평가)

  • Kang, Myeong-Sik;Eom, Sung-Hyun;Cho, Yeon-Chul;Ahn, Jae-Woo;Kim, Seong-Soo;Lee, Jeong-Bae
    • Journal of the Korean Institute of Resources Recycling
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    • v.25 no.3
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    • pp.55-62
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    • 2016
  • Steel structures exposed to extremely corrosive environment like marine environments and industrial area are generally manufactured by applying various protection treatment to increase their lifetime. Metal spraying is one of the protection methods to overcome some drawbacks of the widely employed technologies. Therefore, lots of research needs to be done to improve the corrosion resistance of steel structures. In this study, the corrosion resistance of steel structures was evaluated with the variation in the type and thickness of metal spray by measuring the corrosion potential and current density. As a raw material for spraying, Zn, Al and their mixture were employed to obtain coating thickness of $30{\sim}100{\mu}m$. Our data indicated that the pure zinc coating with $100{\mu}m$ showed the lowest corrosion potential. In the case of pure Al and Zn 85%-Al 15%, the corrosion potential and current density was decreased compared to pure zinc. It was found that the corrosion potential was decreased with the increase of coating thickness irrespective of the type of the coating.

Optimization of Resistance Spot Weld Condition for Single Lap Joint of Hot Stamped 22MnB5 by Taking Heating Temperature and Heating Time into Consideration (핫스템핑 공정에서 가열온도 및 유지시간을 고려한 22MnB5의 단일겹치기 저항 점용접 조건 최적화)

  • Choi, Hong-Seok;Kim, Byung-Min;Park, Geun-Hwan;Lim, Woo-Seung;Lee, Sun-Bong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.10
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    • pp.1367-1375
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    • 2010
  • In this study, optimization of the process parameters of the resistance spot welding of a sheet of aluminum-coated boron alloyed steel, 22MnB5, used in hot stamping has been performed by a Taguchi method to increase the strength of the weld joint. The process parameters selected were current, electrode force, and weld time. The heating temperature and heating time of 22MnB5 are considered to be noise factors. It was known that the variation in the thickness of the intermetallic compound layer between the aluminum-coated layer and the substrate, which influences on the formation of nugget, was generated due to the difference of diffusion reaction according to heating conditions. From the results of spot weld experiment, the optimum weld condition was determined to be when the current, electrode force, and weld time were 8kA, 4kN, and 18 cycles, respectively. The result of a test performed to verify the optimized weld condition showed that the tensile strength of the weld joint was over 32kN, which is considerably higher than the required strength, i.e., 23kN.

Acoustic Nonlinearity of Narrow-Band Surface Wave Generated by Laser Beam with Line-Arrayed Slit Mask (선배열 슬릿마스크를 이용한 협대역 레이저 여기 표면파의 음향 비선형성)

  • Choi, Sung-Ho;Nam, Tae-Hyung;Lee, Tae-Hun;Kim, Chung-Seok;Jhang, Kyung-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.12
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    • pp.1877-1883
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    • 2010
  • We examined the mechanism of generation of higher harmonics by theoretically analyzing the frequency characteristics of a narrow-band surface wave generated by a laser beam with line-arrayed slit masks. We experimentally analyzed the effects of slit opening width and laser intensity on the acoustic nonlinearity of aluminum 6061-T6 alloy by using single-slit and line-arrayed slit masks. The magnitude of the harmonic wave depended on the slit opening width. In our experiment, we generated a 1.75-MHz surface wave by using an arrayed slit with intervals of 1.67 mm. The magnitude of the second harmonic component decreased about by 80% when the slit opening width was increased from 0.5 mm to 1.0 mm. In addition, the relationship between the magnitudes of the fundamental and the second harmonic wave showed good linearity, which agreed well with the typical behavior of acoustic nonlinearity.

Delamination Evaluation of Thermal Barrier Coating on Turbine Blade owing to Isothermal Degradation Using Ultrasonic C-scan Image (초음파 C-scan을 이용한 터빈 블레이드 열차폐코팅의 등온열화에 의한 박리 평가 기법)

  • Lee, Ho-Girl;Kim, Hak-Joon;Song, Sung-Jin;Seok, Chang-Sung
    • Journal of the Korean Society for Nondestructive Testing
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    • v.36 no.5
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    • pp.353-362
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    • 2016
  • Thermal barrier coating (TBC) is an essential element consisting of a super-alloy base and ceramic coating designed to achieve long operational time under a high temperature and pressure environment. However, the top coat of TBC can be delaminated at certain temperatures with long operation time. As the delamination of TBC is directly related to the blade damage, the coupling status of the TBC should be assured for reliable operation. Conventional studies of nondestructive evaluation have been made for detecting generation of thermally grown oxide (TGO) or qualitatively evaluating delamination in TBC. In this study, the ultrasonic C-scan method was developed to obtain the damage map inside TBC by estimating the delamination in a quantitative way. All specimens were isothermally degraded at $1,100^{\circ}C$ with different time, having different partial delamination area. To detect partial delamination in TBC, the C-scan was performed by a single transducer using pulse-echo method with normal incidence. Partial delamination coefficients of 1 mm to 6 mm were derived by the proportion of the surface reflection signal and flaw signal which were theoretical signals using Rogers-Van Buren and Kim's equations. Using the partial delamination coefficients, the partial delamination maps were obtained. Regardless of the partial delamination coefficient, partial delamination area was increased when degradation time was increased in TBC. In addition, a decrease in partial delamination area in each TBC specimen was observed when the partial delamination coefficient was increased. From the portion of the partial delamination maps, the criterion for delamination was derived.