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오스테나이트 스테인리스 주강의 미세 조직 및 고온 산화 특성에 미치는 합금원소의 영향
김순태 ( Soon Tae Kim ),이인성 ( In Sung Lee ),전순혁 ( Soon Hyeok Jeon ),이정석 ( Jung Suk Lee ),고영상 ( Young Sang Ko ),김종명 ( Jong Myoung Kim ) 한국주조공학회 2010 한국주조공학회지 Vol.30 No.5
To elucidate the effects of alloying elements on the characteristics of microstructure and high temperature oxidation of cast austenitic stainless steel, a thermodynamic calculation, a cyclic oxidation test, a X-ray diffraction, a scanning electron microscopy-back scattered electron, a electron probe microanalysis were conducted. The thermodynamic calculation for the effect of vanadium (V) addition on the formation of various precipitates leads to a decrease of chromium (Cr)-rich M23C6 carbides due to the formation of M (C, N) carbo-nitrides containing V and / or niobium (Nb). The V added alloy increased the resistance to high temperature oxidation due to a decrease of Cr-depleted zone deteriorating the oxidation resistance and due to the V-enriched oxide layer formed in inner oxide layer blocking the outward transport of cations.
질소 보호 가스 첨가가 하이퍼 듀플렉스 스테인리스 밀봉용접재의 마모부식 저항성에 미치는 영향
김혜진 ( Hye Jin Kim ),전순혁 ( Soon Hyeok Jeon ),김순태 ( Soon Tae Kim ),이인성 ( In Sung Lee ),박용수 ( Yong Soo Park ) 한국부식방식학회(구 한국부식학회) 2014 Corrosion Science and Technology Vol.13 No.2
Duplex stainless steels with nearly equal fraction of the ferrite(α) phase and austenite(γ) phase have been increasingly used for various applications such as power plants, desalination facilities due to their high resistance to corrosion, good weldability, and excellent mechanical properties. Hyper duplex stainless steel (HDSS) is defined as the future duplex stainless steel with a pitting resistance equivalent (PRE= wt.%Cr+3.3(wt.%Mo+0.5wt.%W)+30wt.%N) of above 50. However, when HDSS is welded with gas tungsten arc (GTA), incorporation of nitrogen in the Ar shielding gas are very important because the volume fraction of α-phase and γ-phase is changed and harmful secondary phases can be formed in the welded zone. In other words, the balance of corrosion resistance between two phases and reduction of Cr2N are the key points of this study. The primary results of this study are as follows. The addition of N2 to the Ar shielding gas provides phase balance under weld-cooling conditions and increases the transformation temperature of the α-phase to γ-phase, increasing the fraction of γ-phase as well as decreasing the precipitation of Cr2N. In the anodic polarization test, the addition of nitrogen gas in the Ar shielding gas improved values of the electrochemical parameters, compared to the Pure Ar. Also, in the erosion-corrosion test, the HDSS welded with shielding gas containing N2 decreased the weight loss, compared to HDSS welded with the Ar pure gas. This result showed the resistance of erosion-corrosion was increased due to increasing the fraction of γ-phase and the stability of passive film according to the addition N2 gas to the Ar shielding gas. As a result, the addition of nitrogen gas to the shielding gas improved the resistance of erosion-corrosion.
슈퍼 듀플렉스 스테인리스강의 캐비테이션 마모 특성에 대한 연구
이인성 ( In Sung Lee ),박용수 ( Yong Soo Park ),김순태 ( Soon Tae Kim ),전순혁 ( Soon Hyeok Jeon ) 한국주조공학회 2010 한국주조공학회지 Vol.30 No.4
To elucidate the characteristics of cavitation erosion of super duplex stainless steel, a cavitation erosion test, an optical micro- structure, a hardness test, and a transmission electron microscope (TEM) analysis were conducted. As aging time at 475°C increased, the hardness of ferrite phase increased whereas that of austenite phase was nearly constant. The reason why the cavitation erosion resistance increased with an increase ofaging time was due to the formation of W-rich phases (a`) of a nanometer scale with the high hardness that were precipitated within a-grains and at a-grain boundaries during aging, compared with that of the solution annealed alloy.