• Nuclear Engineering and Technology
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• 제38권5호
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• pp.405-410
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• 2006

Microstructural features and their related mechanical property changes in the 309L cladding and the heat affected zone (HAZ) of SA508 cl.3 steel were investigated through the use of TEM, tensile and small punch (SP) tests. The specimens were irradiated at 563 K up to the neutron fluences of $5.79{\times}10^{19}n/cm^2$ (>1MeV). The microstructure of the clad was mainly composed of a fcc ${\gamma}-phase$, a low percentage of bcc ${\delta}-ferrite$, and a brittle ${\sigma}-phase$. Along the weld fusion line there formed a heavy carbide precipitation with a width of $20{\sim}40{\mu}m$, showing preferential cracking during plastic deformation. The yield stress and ductile-to-brittle transition temperature (DBTT) of the irradiated clads increased. The origin of the hardening and the shift of the DBTT are discussed in terms of the irradiation-produced defect clusters of a fine size and brittle ${\sigma}-phase$.

• 열처리공학회지
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• 제11권3호
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• pp.207-215
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• 1998

13%Cr martensitic stainless steel was microalloyed with 0~1.5%Mo, and the mechanical properties were tested at the various heat treated conditions. Mo addition increased austenitization temperature(Ac1), and had little influence on the hardness and tensile properties at the annealed condition. The higher the austenitizing temperature, the higher the hardness and tensile strength, but Mo addition decreased those properties. The impact energy after austenitization increased with addition of Mo. The decrease of mechanical properties and increase of impact energy of Mo-alloyed steel after austenitization are thought to be caused by formation of ductile ${\delta}$-ferrite phase in the microstructure.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.156-158
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• 2004

The microstructural evolution in a 304 stainless steel weld during FSW was examined. The SZ and TMAZ showed typical dynamically recrystallized and recovered microstructures, respectively, The microstructural observation revealed that sigma phase was formed at the advancing side of the stir zone. A possibility was suggested that the rapid formation of the sigma phase is related to the transformation of austenite to delta-ferrite in the stir zone, from introduction of high strain and dynamic recrystallization during FSW.

• 한국해양공학회지
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• 제22권6호
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• pp.41-45
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• 2008

Effectsof carbon content on the weldability of B-containing 620 grade high Cr ferritic cast steels were investigated. Cast steel with lower carbon content of 0.07% showed lower HAZ hardness because of the formation of lower carbon martensite in HAZ. It also showed less solidification cracking susceptibility in weld metal because of the formation of delta ferrite. However, hot ductility showed no difference between cast steels with lower and higher carbon contents. Cast steel with lower carbon content showed greater HAZ softening after PWHT in the region heated between AC1 and AC3 because of its higher base metal hardness.

• 한국기계연구소 소보
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• 통권19호
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• pp.43-52
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• 1989

Material damage of Unifiner Change Heater: Tube used for nearly 20 years was evaluated and Mechanical tests such as tensile tests and creep-rupture tests were conducted to predict the residual life. After the investigation, any major damage or degradation was not found except the welded zone. Microstructural observation showed that most of delta-ferrite was transformed. to sigma-phase and consequently, the ductility was very much reduced. A KLA(Knife-Line Attack) crack with 60mm in length and 2.8mm in depth was found just near the welded zone, which is believed to be caused by intergranular corrosion. Creep-rupture tests, which are very essential to predict the residual life, showed that both used base and weld metals have similar results with the reference data.

• 전자공학회논문지A
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• 제30A권4호
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• pp.11-19
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• 1993

The complex permittivity and the linewidth of microwave ferrites are measured using the well known cavity perturbation method. The cavity perturbation method has been widely used for the measurement of complex permittivity and conductivity of low loss magnetic and dielectric materials at microwave frequencies. TT1-2000, TT73-2200, and G-113 samples ordered from Trans-Tech Inc, are tested. TE$_{103}$ and TE$_{106}$ rectangular waveguide cavities are fabricated and the ferrite sample of cylidrical rod and sphere shapes are prepared. The error between the measurement values and the supplier's data is less than 1 percent in case of $\varepsilon$’ and about 10 percent in case of linewidth ($\Delta$H). Worst case error analysis shows that our measured results are well within the error bound calculated from the accuracy specification of the measuring instruments.

• 한국안전학회지
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• 제14권1호
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• pp.25-32
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• 1999

The objective of this paper is to evaluate the fracture resistance characteristics of SA508 CL.1a carbon steel, TP347 stainless steel and their associated welds manufactured for primary coolant system of Ulchin 3,4 nuclear power plants. The effect of various parameters such as pipe size, welding method, chemical composition, crack plane orientation, metallography and fractography on the material properties were discussed. Test results showed that the effect of pipe size on fracture toughness is negligible while the effect of welding method on fracture toughness is significant. In addition, the drop of fracture toughness in the field fabrication weld of TP347 stainless steel is probably due to the large amount of $\sigma$-phase precipitated on the $\delta$-ferrite boundary and the large size dimples.

• 한국자기학회지
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• 제5권5호
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• pp.627-630
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• 1995

BaM films have a lot of advantage of chemical stability and mechanical stability as compared with a metallic thin film. In this paper, (Ba.Pb)M films have been prepared by using dc magnetron sputtering system and the dependences of their crystallographic characteristics and magnetic properties on oxygen pressure($Po_{2}$) were studied. The films prepared at $Po_{2}$ of around 0.02mTorr exhibit a fine particle-like structure and ${\Delta}{\theta}_{50}$ is as small as $1^{\circ}$. $Hc_{\bot},\;Hc_{//}$ and Ms of (Ba.Pb)M films are 700-800Oe, 200Oe and 180-230emu/cc, respectively.

• Corrosion Science and Technology
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• 제14권2호
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• pp.93-98
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• 2015

Recently, Stainless steels have been increasingly selected as the fitting or the valve materials of water pipes as the human health issue is getting higher and higher. Therefore, the connectors attached at pipes to deliver water are exposed to more severe environments than the pipes because crevice or galvanic corrosion is apt to occur at the fittings or the valves. Effects of the solid solution annealing, cooling rate after this heat treatment, and passivation on the corrosion properties of the shell mold casted SSC13 (STS304 alloy equivalent) were studied. The heating and quenching treatment more or less reduced hardness but effectively improved corrosion resistance. It was explained by the reduction of delta ferrite contents. Independent of heat treatment, the chemical passivation treatment also lowered corrosion rate but the improvement of corrosion resistance depended on temperature and time for passivation treatment indicating that the optimum conditions for passivation treatment were the bath temperature of $34^{\circ}C$ and operating time of 10 minutes. Therefore it is suggested that the corrosion resistance of SSC13 can be effectively improved with the heat treatment, where SSC13 is heated for 10 minutes at $1120^{\circ}C$ and quenched and passivation treatment, where SSC13 is passivated for at least 10 seconds at $34^{\circ}C$ nitric acid solution.

• 한국세라믹학회지
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• 제40권5호
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• pp.428-433
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• 2003

이 연구에서는 소결온도와 Zr치환에 따른 아이솔레이터/서클레이터용 YIG 페라이트의 미세구조와 전자기적 특성의 변화를 고찰하고자 하였다. 조성은 $Y_{2.1}$C $a_{0.9}$F $e_{4.4-x}$ $V_{0.5}$I $n_{0.05}$A $l_{0.05}$Z $r_{x}$ $O_{12}$에서 x의 값을 0, 0.05, 0.1, 0.2로 변화시켰으며, 일반적인 세라믹 제조 공정으로 YIG페라이트를 제조하였다. 그 결과, Zr이 0.1 mol 정도 치환된 YIG 페라이트가 가장 높은 포화자화(1097 gauss) 값을 나타내었으며, 또한, Zr을 0.2 mol 치환한 경우 격리도 18.60 dB, 삽입손실 0.45 dB의 마이크로파 특성을 나타내었다. 자기 공명 선폭($\Delta$H)은 Zr의 치환량이 증가할수록 감소하는 경향을 보였다.다.다.다.