• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.125-130
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• 2017

Automotive materials and plant modules need to be prepared for freezing parts to operate in extreme areas such as Eastern Europe, Russia, and Canada. However, the only thing that has been done for ultra-qualifying materials for extremely low operating materials is that only the effects at low temperatures are conducted at room temperature, and the effects at low temperatures are only identified at low speeds. Therefore, this study examined the low-temperature characteristics of materials by conducting comparative tests on the mechanical properties of the room at the temperature and temperature of TP304 and TP316 materials, which are the most common materials.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.9
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• pp.1166-1174
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• 2000

This work presents a two-dimensional quasi-steady state model to study the fluid flow and heat transfer in high-power density welding process of thin AISI-304 stainless steel plates. The enthalpy method and the finite volume method were used for a numerical analysis of the mushy region phase change as well as the heat flow at the weld pool and the heat-affected zone. The results show that the mushy region distributed around the weld pool becomes wider downstream and the surface heat losses by convection and radiation can be significant factors in welding process especially when a welding speed is relatively low.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.465-474
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• 2001

Type 304SS coatings were performed at 200$\square$ onto AISI 1045 carbon steel substrate using unbalanced magnetron sputtering (UBMS) with an austenitic AISI 304 stainless steel (SS) target of 100mm diameter. The total deposition pressure in the active Ar gas was 2$\times$10$^{-3}$ Torr. Coatings were done at various target power densities and bias voltages. Chemical compositions of metallic elements of the coatings were measured by energy dispersive X-rays spectroscopy (EDS). The structure and the morphology of Type 304SS coatings were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Corrosion properties of the coated specimens were examined using electrochemical polarization measurements and electrochemical impedance spectroscopy in a deaerated 3.5% NaCl solution. The porosity rate was obtained from a comparison of the dc polarization resistance of the uncoated and coated substrates. Scratch adhesion testing was used to compare the critical loads for different coatings. XRD results showed that the sputtered films exhibit a ferritic b.c.c. $\alpha$-phase. Potentiodynamic polarization curves indicated that all samples had much higher corrosion potential and better corrosion resistance than the bare steel substrate. The corrosion performance increased with increasing power density and the adhesion was enhanced at the bias voltage of -50V. An improvement in the corrosion resistance can be obtained with a better coating adhesion. Finally, an optimized deposition condition for corrosion protection was found as $40W/cm^2$ and -50V.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2638-2641
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• 2007

The magnetohydrodynamic(MHD) pressure drop along a liquid sodium flow was measured in a rectangular duct under a transverse magnetic field. The test section was made of a 3 mm thick stainless steel SUS304 with a $74{\times}5mm^2$ rectangular flow channel. The range of experimental parameters was roughly B=0${\sim}$0.18T and U=0${\sim}$0.9m/s at around $200^{\circ}C$. The differential pressure was measured by a diaphragm seal-type pressure transmitter filled with a high temperature silicon oil within 0.1MPa. The experimental results show a similar pressure drop with the theoretical estimation according to a change of the flow velocity and the magnetic field.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.979-980
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• 2004

A multi-channel mechanical test machine for HANARO was designed and fabricated based on the design criteria of the multi-channel mechanical test machine sustained at the working conditions of $<400{\square}$, 3 W/g of gamma heating rate, $5{\times}10^{20}\;n/cm^2$, neutron flux and maximum load of 200 MPa. The multi-channel mechanical test machine made of 304 stainless steel consisted of four modules. Two of them locate upper part of the machine and the others locate lower part with 90 degree rotation. Each module was evaluated by determine load-displacement curve of zirconium specimen. Thermal insulators were also made by electron spark-machining of pure aluminum which was prepared in a domestic company.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.6
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• pp.371-377
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• 2001

스테인리스강의 주요 특징은 우수한 내식성에 있다. 그럼에도 불구하고 스테인리스강은 질화시키면 스테인리스강의 주요 특징인 내식성의 저하가 불가피하다. 그러나 경우에 따라서는 내식성이 다소 희생되더라도 내모성 향상을 목적으로 SUS 304소재를 이용한 피스톤링이나 SUS 420 J2소재를 사용하는 마이크로 샤프트 등과 같은 많은 제품에 대하여 질화처리를 실시하고 있다. 스테인리스 제품에 얼룩이 없는 질화처리를 실시하기 위해서는 앞에서 소개한 방법 이외에 표면활성화를 위한 분말처리법 등이 많이 사용되고 있으며, 그 예로 일본의 마테크(주)에서 제조하여 (주)사마루에서 시판하고 있는 활성분체질화제(APN법, DCA)을 사용하여 질화시키는 방법등도 있다. 이와 같이 외국에서는 프라즈마법이 아닌 일반 가스질화에 의한 스테인리스강의 질화에 대한 많은 연구가 이루어지고 산업화 되어 있지만 현재 국내에서는 이에 대한 연구가 거의 이루어지고 있지 않은 실정이다. 따라서 앞으로는 국내에서도 이러한 분야에 대한 보다 많은 관심과 연구 및 기술보고 등이 활성화되어야 할 것으로 생각된다.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2329-2333
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• 2022

Base metal corrosion forms a significant issue during the chemical decontamination of the primary coolant loop in nuclear power plants as it is directly related to the economic and safety viability of decommissioning. In this technical note, potentiodynamic evaluations of several base metals (304 stainless steel, SA106 Grade B carbon steel, and alloy 600) were performed to determine their corrosion behavior during the hydrazine (N₂H₄)-based reductive ion decontamination (HyBRID) process. The results suggested that N₂H₄ protected the surface of the base metals in the HyBRID solution, which is primarily composed of H₂SO₄. The corrosion resistance of the carbon steel was further improved through the addition of CuSO₄ to the solution. The corrosion rate of carbon steel in the H₂SO₄-N₂H₄-CuSO₄ solution was lower than that exhibited in an oxalic acid solution, a commonly used reaction medium during commercial decontamination processes. These results indicate the superiority of the HyBRID process with respect to the base metal stability.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.2
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• pp.1-7
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• 2001

To protect combustion chamber from high temperature combustion gas, regenerative cooling is used for most liquid rocket engine. Although regenerative cooling is the most effective way to protect the chamber from high heat flux, realization of this system requires detail analysis, manufacturing technique and high cost. To demonstrate the possibility of applying regenerative cooling to a real rocket engine, the hot fire test has been carried out for the sub-scale liquid rocket with the water cooling system. The main purpose of the test is to identify the problem area of design, safety and cost effective manufacturing technique. The coolant passage was 3 mm in width and wall thickness was 1 mm with stainless steel. Maximum combustion time and pressure were 60 seconds and 400 psi, respectively. The flow rate of coolant was reduced gradually from 2 kg/s to 0.12 kg/s throughout firing test, combustion chamber was visually examined and no dwfect was observed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.310-313
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• 2009

Several high nitrogen stainless steel ingots(100kg) were fabricated with changing Ni and $[N]_2$ contents by Pressurized Vacuum Induction Melting(P_VIM). After free forging process, chemical compositions, microstructure and mechanical properties were estimated. Hardness was increased with the increase of $[N]_2$ content. Furthermore, microstructure including a lot of tempering twins was observed with optical microscope. Mechanical properties were estimated as function of solution treatment temperature and cooling method(air/water) under duration time of 1 hr on sample that were fabricated with Ni content under the atmospheric $[N]_2$ pressure. At solution treatment range of $1050{\sim}1100^{\circ}C$, hardness was decreased with the increase of solution temperature and there were little discrepancy of microstructure and hardness with cooling method. Computer simulation was carried out in order to inspect pass schedule in cold rolling process. When the condition of simulation was roll speed of 2.5mpm, rolling rate $15{\sim}17%$ per pass, it was ascertained that the formation such as deformation by sticking and lamellar sliver etc. was restricted from a simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.136-140
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• 2006

We are developing a vol-oxidizer which transforms the spent $UO_2$ pellets into the $U_3O_8$ power through oxidizing process. The vol-oxidizer consists of furnace, filter, heater and valve etc. When the filter is blocked by the powder, the internal pressure of the furnace is increased owing to the air flow restriction. Then, the furnace vessel is swelled and deformed by it. In this paper, we proposed a procedure of the thermal analysis for furnace vessel design of spent fuel vol-oxidizer. In this work, we determined the thickness of the furnace through analyzing the internal pressure and the thermal stress of the furnace with respect to various pressure and temperature. To analyze the thermal stress, we used ANSYS 8.0 for constructing a FEM model of the furnace, and then analyzed it based on the ASME code. We also surveyed the material property and yield stress of SUS304 with various temperature. Analysis results are compared with the yield stress of the material. We manufactured the furnace and conduct the verification experiments.