• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.236-239
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• 2000

It is important to evaluate austenitic heat resistant stainless steel because of low weldability of austenitic heat resistant stainless steel containing high Si. This study took varestraint test for evaluation of solidification cracking sensitivity and Erichsen test for evaluation of weld metal ductility. As a result of tests, solidification crack sensitivity increased with adding $N_2$ to shielding gas, and W had detrimental effect on crack resistance, but Ce had beneficial effect on crack resistance. Under same heat input, ductility of weld metal increased with welding speed.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.806-813
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• 1999

The effect of Post-Weld Heat Treatment(PWHT) of SS400 Steel was investigated with parameters such as micro vickers hardness corrosion potential polarization behaviors galvanic current Al anode generating current Al anode weight loss etc. Hardness of each parts(HAZ, BM, WM)by PWHT is lower than that of each parts by Non Post-Weld Heat Treatment(NPWHT) However hardness of WM of HAZ part was the highest among those three parts and HAZ area were also acted as cathode without any case of heat treatment. Potential difference between each three parts by PWHT was also smaller compared to NPWHT. Therefore it is suggested that Corrosion resistance property is increased by PWHT. However both Al anode generating current and anode weight loss was also decreased by PWHT compared to NPWHT when SS400 steel is cathodically protected by Al anode.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.704-713
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• 2003

The effect of partial substitution of tungsten for molybdenum on the microstructure and corrosion resistance in 22Cr-5Ni-3Mo duplex stainless steel(DSS) aging heat treated in a temperature range of 600~$1000^{\circ}C$ has been investigated. Electrochemical tests were carried out for the evaluation of corrosion resistance. Aging treatment had hardly influenced the general corrosion resistance. With the increase of aging time, the pitting corrosion resistance of the DSS had decreased, After aging for 2min at 700~$900^{\circ}C$, the pitting potential of the 3Mo steel decreased remarkably, while that of the W-substituted steel hardly changed. During aging. the intermetallic $\sigma$ and secondary austenite ($\gamma_2$) phases were precipitated. and the pitting corrosion and intergranular corrosion resistance were significantly decreased after aging at 700~$750^{\circ}C$ for 10 h, which could be caused by the $\gamma_2$ formation. The ${\gamma}$$_2$ phase could affect the depletion of molybdenum and chromium in the $\gamma_2/\alpha and \gamma_2/\sigma$ boundaries.

• Steel and Composite Structures
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• v.37 no.5
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• pp.589-603
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• 2020

This paper presents an investigation of the thermal performance of composite floor slabs with profiled steel decking exposed to fire effects from floor. A detailed finite-element model has been developed by representing the concrete slab with steel decking under of it and steel beam both steel parts protected by intumescent coating. Although this type of floor systems offers a better fire resistance, passive fire protection materials should be applied when a higher fire resistance is desired. Moreover, fire exposed side is so crucial for composite slab systems as the total fire behaviour of the floor system changes dramatically. When the fire attack from steel parts, the temperature rises rapidly resulting in a sudden decrease on the strength of the beam and decking. Herein this paper, the fire attack side is assumed from the face of the concrete floor (top of the concrete assembly). Therefore, the heat is transferred through concrete to the steel decking and reaching finally to the steel beam both protected by intumescent coating. In this work, the numerical model has been established to predict the heat transfer performance including material properties such as thermal conductivity, specific heat and dry film thickness of intumescent coating. The developed numerical model has been divided into different layers to understand the sensitivity of steel temperature to the number of layers of intumescent coating. Results show that the protected composite floors offer a higher fire resistance as the temperature of the steel section remains below 60℃ even after 60-minute Standard (ISO) fire and Fast fire exposure. Obtaining lower temperatures in steel due to the great fire performance of the concrete itself results in lesser reductions of strength and stiffness hence, lesser deflections.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.10a
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• pp.166-173
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• 1996

There are kinds of materials for protective heat shield, i.e.Zn-coated steel, AI-coated steel and aluminum alloy sheets. This study compare formability, corrosion resistance, heat protectability, weight, and cost of these materials for heat protective shield. Generally aluminum alloy sheets are less formable than steel sheets, but A1100 alloy sheet shows almost same press quality of steel parts, using the press dies which producing steel parts. The heat shields using aluminum alloy sheet and steel sheet show almost same heat protectibility. It is the conclusion that Zn-coated merit, and AI-coated steel sheet and aluminum alloy sheet can be used to protect functional corrosion in severely corrosive market area. The material cost of AI-coated steel sheet and aluminum alloy sheet for a mid-size car is almost same, so aluminum alloy sheet is more recommendable in the point of weight reduction of vehicle.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.163-166
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• 2000

The production technology of high strength and toughness wear resistance steel involves attempt to application of severe wear parts for the construction machinery. A well balanced alloy content ensures that optimum tensile properties are achieved for the high strength. After high temperature deformation like as rolling or forging it has bainite microstructure and lower yield rato(under 80%) The effectiveness of the research approach is illustrated with experimental results on good steel cleanliness(O2 :12.2 ppm, 0,004% S, 0.008%, P nonmetalic inclusion dT: 0.10) and excellent mechanical properties (TS$\geq$140kgf/mm2 El $\geq$10% IV$\geq$20j/cm2) Therefore this should be wear resistance steel which develops high strength and high toughness without heat treatment

• Journal of Advanced Marine Engineering and Technology
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• v.13 no.2
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• pp.64-77
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• 1989

In this study, the experiments were carried out for the purpose of establishment of aluminium cementation to steel surface by diffusible heat treatment after making the coated film onto the substrate by arc spray method. Also, the microstructure and mechanical properties of the cementation layer produced by this study were inspected for various heat treatment and spraying conditions. Main results obtained are as follow ; 1. The coating film characteristics which have excellent errosion-resistance, high temperature oxidation-resistance are obtained by aluminium penetration heat treatment after making the sprayed aluminum coating film onto the steel substrate. 2. Aluminium diffusion penetration takes place at higher temperature than 660.deg.C, and the more heat treatment time and the higher heat treatment temperature adopted, the deeper diffusion layer obtained. 3. Insert gas arc spraying using argon gas as the carrier gas higher improvement of mechanical property than that of compressed air environment. 4. The coating film characteristics appeared to be improvement of adhesive property, porosity plugging effect by heat treatment in air environment.

• 연구논문집
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• s.26
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• pp.121-132
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• 1996

The carburising surface modification treatment of the die steel has been used for improving wear resistance and heat cycle strength of the die and preventing a pitting on the surface because the carbides are forming in the matrix during carburising. Generally, the hot forging die was used after quenching-tempering treatment or nitriding after quenching-tempering treatment. The nitriding after carburising on the surface of a hot die steel and a wear resistance die steels was suggested by SOUCHARD, JACQUOT. and BUVRON. This surface modification treatment improved the adhesive and abrasive wear resistance and friction coefficient. The process was introduced to the forging die of stainless steel, titanium alloy steel, alloy and medium carbon steel and the physical properties of the die after the treatment were improved. The surface hardening treatment of the nitriding, the carburising, the boriding, and TD process were used to improved the life time of the forging die. Also, the coating process of PVD, CVD and PCVD were used and the hard chromium plating was occasionally used. Therefore, this study analyzed the effects of the carburising time and the conditions of nitriding on STD61 steel. The case depth, the surface hardness, the forming carbide size and shape during overcarburising process on the die steel were also examined.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.736-743
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• 2007

Laser welding has the advantage of high welding speed and Provides low heat distortion Thus laser welding is a very attractive process for joining thin steel sheet and surface treated steel sheet. And the major item in market for surface treated steel sheet is zinc coated steel. However. the laser welding of zinc coated steel is very difficult because of its low boiling point. Compared with zinc, on the other hand, aluminum has a high boiling point. Thus, laser weldability of aluminized steel is better than that of zinc coated steel. Moreover aluminized steel sheet is a material with excellent heat resistance, thermal reflection and corrosion resistance. The results of laser weldability of the aluminized steel for the full penetration welding will be described in this paper We focused on the investigation of the phenomenons caused by coating condition and behavior of aluminum in weld.

• Journal of Welding and Joining
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• v.22 no.5
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• pp.58-64
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• 2004

Although leakage at a low carbon steel pipe made by electrical resistance welding (ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. In order to clarify the main cause, failure analysis on the leaked pipe was carried out, followed by metallographic investigation and corrosion test for the various ERW pipe made with different welding heat input. The microstructure, particularly inclusion content, of the weldment is dependant on the welding heat input applied. For an improper low heat input, the amount of inclusion at the weld was high. High inclusion content accelerated grooving corrosion at the weld. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion resistance of the ERW pipe.