• 공업화학
• /
• 제26권4호
• /
• pp.477-482
• /
• 2015

본 연구에서는 순환골재와 순환골재/제강슬래그 조합을 이용하여 수용액상에서 $Cr^{6+}$과 $As^{3+}$ 흡착 특성을 평가하였다. 순환골재와 제강슬래그의 주요 성분(CaO, $SiO_2$, $Al_2O_3$, $Fe_2O_3$)이 각각 91%와 86.9% 함유되어 흡착제로서 유리한 조성을 가지고 있다. 순환골재와 순환골재/제강슬래그 조합에 있어서 $Cr^{6+}$과 $As^{3+}$의 동역학적 평형은 각각 180 min과 360 min 이후에 도달하였다. 동적흡착결과를 유사 1차 모델과 유사 2차 모델로 분석한 결과 두 모델 모두 더딘 평형 결과를 나타냈다. 순환골재와 순환골재/제강슬래그 조합에 있어서, 평형흡착 실험은 Freundlich 모델에 잘 부합했고, $Cr^{6+}$보다 $As^{3+}$의 흡착량이 더 높았다. 용액의 pH가 6에서 10으로 증가함에 따라서 $As^{3+}$의 흡착률은 증가하는 것으로 나타났다. 한편, $Cr^{6+}$는 감소를 나타냈다. 본 연구 결과를 통해 순환골재 및 순환골재/제강슬래그 조합은 중금속($Cr^{6+}$, $As^{3+}$)을 효율적으로 제거할 수 있는 흡착제로 판단된다.

• 한국표면공학회지
• /
• 제52권3호
• /
• pp.111-116
• /
• 2019

Chromium was coated on a steel substrate by the Cr(III) electroplating method, and corroded at $500-900^{\circ}C$ for 5 h in $N_2/0.1%H_2S-mixed$ gas to study the high-temperature corrosion behavior of the Cr(III) coating in the highly corrosive $H_2S-environment$. The coating consisted of (C, O)-supersaturated, nodular chromium grains with microcracks. Corrosion was dominated by oxidation owing to thermodynamic stability of oxides compared to sulfides and nitrides. Corrosion initially led to formation of the thin $Cr_2O_3$ layer, below which (S, O)-dissolved, thin, porous region developed. As corrosion progressed, a $Fe_2Cr_2O_4$ layer formed below the $Cr_2O_3$ layer. The coating displayed relatively good corrosion resistance due to formation of the $Cr_2O_3$ scale and progressive sealing of microcracks.

• Journal of Welding and Joining
• /
• 제18권2호
• /
• pp.49-56
• /
• 2000

Recently developed Austenite stainless steel, 309L was used to overlay on 3Cr-1Mo-V-Ti-B steels, using Electroslag welding process, which wide electrodes were adopted. Transition region in welding interlayer relating to disbonding crack was investigated. Also, the effect of welding condition on the width of transition region and coarsening grains of the austenite were studied. 1) With increasing welding speed the width of martensite at transient region was increased, but the amount of delta ferrite in weld metal was reduced, being fine grained. 2) The form of martensite at the transition region was occurred by reversible transformation during cooling since the interdiffusion of Cr and Ni from weld metal and Fe and C from base metals at the transition region, causes to lowering the concentration of Cr and Ni at the transition region, leading to increasing Ms point. 3) With increasing welding speed, the grain of austenite formed at the welding interface was finer. With increasing welding current under the same welding speed, the grain size of the austenite was finer. At high current, original grain size of the austenite is coarse, but the austenite has fine grains because the austenite was transformed to martensite during cooling. 4) In the case of high welding speed, the width of martensite at the welding interface was increased, but the grain size of austenite at the welding interface was finer. This indicates that the inhibition of disbonding crack may be achieved through dispersening fine carbides in the gain boundary.

• 한국기계가공학회지
• /
• 제3권3호
• /
• pp.52-57
• /
• 2004

Many kinds of gases, such as erosion gas, dilution gas, and toxic gas have been used in manufacturing process of LCD at semiconductor. In order to increase accumulation rate of manufacturing process, high degree of purity in these gases and minimized metalllic dust are required. All wetted stainless steel surface must be 316L electro-polished with $0254{\mu}m$ in average. Based on the AES analysis, Cr/Fe 11 and $Cr_2O_3$ thickness $25{\AA}$ are measured Molybdenum and silicon contaminants which is characteristic of stainless steel and oxygen were found on the surface.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2015년도 추계학술대회 논문집
• /
• pp.291-292
• /
• 2015

Duplex Stainless Steel의 Plasma Nitriding 처리 시 가스량과 처리온도가 표면 특성에 미치는 영향을 조사하였다. $N_2$함량 및 처리 온도가 각각 10%에서 25%로 $400^{\circ}C$에서 $430^{\circ}C$로 증가함에 따라서 질소가 과고용된 S-phase의 두께 및 표면 경도가 증가하였으나, 내부 식성은 $Cr_2N$ 및 $(Fe,Cr)_4N$이 석출하여 감소하였다. 질소를 10%로 고정하고 $CH_4$함량을 증가시키면 1%일 때 S-phase의 두께가 최대가 되며 그이후로 감소하였다. 처리온도 $400^{\circ}C$일 때 질소함량이 10%, $CH_4$ 함량이 5%일 경우 내식성이 모재보다 증가하였다.

• 열처리공학회지
• /
• 제26권3호
• /
• pp.105-112
• /
• 2013

The microstructural changes of Fe-20Mn-12Cr-1Cu alloy have been studied during high temperature gas nitriding (HTGN) at the range of $1000^{\circ}C{\sim}1150^{\circ}C$ in an atmosphere of nitrogen gas. The mixed microstructure of austenite and ${\varepsilon}$-martensite of as-received alloy was changed to austenite single phase after HTGN treatment at the nitrogen-permeated surface layer, however the interior region that was not affected nitrogen permeation remained the structure of austenite and ${\varepsilon}$-martensite. With raising the HTGN treatment temperature, the concentration and permeation depth of nitrogen, which is known as the austenite stabilizing element, were increased. Accordingly, the depth of austenite single phase region was increased. The outmost surface of HTGN treated alloy at $1000^{\circ}C$ appeared Cr nitride. And this was in good agreement with the thermodynamically calculated phase diagram. The grain growth was delayed after HTGN treatment temperature ranges of $1000^{\circ}C{\sim}1100^{\circ}C$ due to the grain boundary precipitates. For the HTGN treatment temperature of $1150^{\circ}C$, the fine grain region was shown at the near surface due to the grain boundary precipitates, however, owing to the depletion of grain boundary precipitates, coarse grain was appeared at the depth far from the surface. This depletion may come from the strong affinity between nitrogen and substitutional element of Al and Ti leading the diffusion of these elements from interior to surface. Because of the nitrogen dissolution at the nitrogen-permeated surface layer by HTGN treatment, the surface hardness was increased above 150 Hv compared to the interior region that was consisted with the mixed microstructure of austenite and ${\varepsilon}$-martensite.

• Journal of Welding and Joining
• /
• 제16권1호
• /
• pp.88-97
• /
• 1998

The surface characteristics of 13Cr stainless steel systems by plasma nitriding were investigated. The plasma nitriding for the 13Cr steels, in which the nitriding forming elements such as Ti, V, W, Nb, Al, Zr and Si were added about 2~3wt.%, respectively, was performed. In all nitrided specimens, .epsilon.-F $e_{2-3}$N, UPSILON.'-F $e_{4}$N and CrN were detected as the nitrides with the a-Fe in the nitrided layer. VN and .betha.- $W_{2}$N were also detected in 13Cr-3V and 13Cr-3W alloys. The growth of the nitrided layer was controlled by the diffusion process. The thickness of the nitrided layer was similar in the 13Cr-2Nb and 3Zr specimens to that of 13Cr(BM) specimen, while the others exhibited the thinner layer. The activation energy for the growth of the nitrided layer in the temperature range of 773-873K was about 130kJ/mol in 13Cr(BM), 13Cr-2Ti, 3W, 3Al, 3Zr and 3Si alloys. The hardness of the nitrided specimens was significantly increased above Hv1000, comparing to the non-nitrided specimen. The specimens with the nitrided forming elements revealed much higher hardness values and, especially, 13Cr-3Al, 3V and 3Si specimens were significantly hardened up to Hv1300.v1300.0.

• 대한금속재료학회지
• /
• 제48권6호
• /
• pp.523-532
• /
• 2010

Co-application of organic coating and cathodic protection has not provided enough durability to low-alloyed steels inseawater ballast tank (SBT) environments. An attempt has made to study the effect of alloy elements (Al, Cr, Cu, Mo, Ni, Si, W) on general and localized corrosion resistance of steels as basic research to develop new low-allowed steels resistive to corrosion in SBT environments. For this study, we measured the corrosion rate by the weigh loss method after periodic immersion in synthetic seawater at $60^{\circ}C$, evaluated the localized corrosion resistance by an immersion test in concentrated chloride solution with the critical pH depending on the alloy element (Fe, Cr, Al, Ni), determined the permeability of chloride ion across the rust layer by measuring the membrane potential, and finally, we analyzed the rust layer by EPMA mapping and compared the result with the E-pH diagram calculated in the study. The immersion test of up to 55 days in the synthetic seawater showed that chromium, aluminium, and nickel are beneficial but the other elements are detrimental to corrosion resistance. Among the beneficial elements, chromium and aluminium effectively decreased the corrosion rate of the steels during the initial immersion, while nickel effectively decreased the corrosion rate in a longer than 30-day immersion. The low corrosion rate of Cr- or Al-alloyed steel in the initial period was due to the formation of $Cr_2FeO_4$ or $Al_2FeO_4$, respectively -the predicted oxide in the E-pH diagram- which is known as a more protective oxide than $Fe_3O_4$. The increased corrosion rate of Cr-alloyed steels with alonger than 30-day exposure was due to low localized corrosion resistance, which is explained bythe effect of the alloying element on a critical pH. In the meantime, the low corrosion rate of Ni-alloyed steel with a longer than 30-day exposure wasdue to an Ni enriched layer containing $Fe_2NiO_4$, the predicted oxide in the E-pH diagram. Finally, the measurement of the membrane potential depending on the alloying element showed that a lower permeability of chloride ion does not always result in higher corrosion resistance in seawater.

• 분석과학
• /
• 제17권5호
• /
• pp.416-422
• /
• 2004

시간분해 레이저 유도 파열 분광분석 (TRELIBS) 시스템을 구성하여 원자력발전소 계통재질의 성분을 정성 분석하는 데 응용하였다. 본 연구에서는 탄소강 (A106 Gr. B, A336 P11, A335 P22), 스텐인레스강 (type 304, type 316) 및 인코넬 계열 합금(인코넬 600, 인코넬 690, 인코넬 800) 시료를 사용하였다. 탄소강의 종류는 485~575 nm 파장영역에서 나타난 Cr/Fe과 Mo/Fe의 TRELIBS 피크 비에 의해서 서로 구분 가능하였다. type 304와 type 316 스텐인레스강은 485~575 nm 파장영역에서 나타나는 Mo의 TRELIBS 피크 존재 여부에 의해서 쉽게 구분 가능하였다: type 304는 어떤 Mo의 피크도 나타내지 않지만, type 316은 Mo의 피크를 보여준다. 인코넬 계열 합금강 종류는 420~510 nm 파장영역에서 나타난 Cr/Fe과 Ni/Fe의 TRELIBS 피크비에 의해서 서로 구분 가능하였다. TRELIBS는 시료의 전처리 없이 빠르고 쉽게 합금을 분석할 수 있는 효과적인 분석 기술임이 입증되었다.

• 한국마린엔지니어링학회:학술대회논문집
• /
• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
• /
• pp.232-233
• /
• 2005

Stainless steel has been stably used closed by passivity oxidation films($Cr_2O_3$) is made by neutral atmospheric environment. However, passivity oxidation films of the surface of stainless steel occasionally comes to be destroyed in seawater which is influenced by an environment having halogen ion like $Cl^-$, then, localization corrosion comes to occur. Stainless steel 304 for shaft system material of the small-size FRP fishing boat on seawater environments made an experiment on simulation of sacrifical anode(Al, Zn). Through these experiment and study, following results have been obtained ; According to the field inspection and corrosion simulation, the corrosion on the 2nd class stainless steel shaft(STS 304) in FRP fishing boat has been verified to occur by crevice corrosion and galvanic corrosion etc.. According to the comparison and analysis of Stainless steel 304 shaft materials after simulation leaving unprotected and applying cathodic protection, unprotected shaft specimen of stainless steel 304 was severely corroded, but, protected shaft specimen was not totally corroded. This result is assumed to be made by the facts that anodic reaction, $Fe{\rightarrow}Fe^{2+}$ + $2e^-$, has been restricted by the cathodic protection current of sacrificial anode material.