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페라이트계 강의 인성 및 내식성에 미치는 알루미늄과 칼슘의 영향
金熙山 홍익대학교 산업기술연구소 2003 産業技術 Vol.13 No.-
The effects of aluminum and calcium on toughness and corrosion were studied as a series of basic studies for optimizing the concentrations of minor alloying elements. Toughness was closely related to the concentration of oxide and dissolved oxygen, depending on aluminum and calcium as an alloying element, in ferritic steels not containing titanium. However, the toughness of Ti added steels were independent of the addition of aluminum and/or calcium playing a role of reducing the concentrations of oxide and dissolved oxygen. It indicates the presence of Ti-containing secondary phase formation more susceptible to toughness that oxide inclusion. The corrosion resistance was degraded by the addition of aluminum and calcium but their causes were different. The formation of calcium sulfide chemically unstable provided a site for crevice corrosion and pitting corrosion. The micro-crevice formed at matrix-alumina interface give a site for pitting corrosion but not for crevice corrosion.
고 크롬 페라이트계 강의 인성 및 내식성에 미치는 티타늄의 영향
金熙山 홍익대학교 산업기술연구소 2002 産業技術 Vol.12 No.-
Lower toughness and intergranular corrosion resistance of ferritic stainless steels(SSs) than austenitic SSs limited the applications of ferritic SSs. The effects of Ti on toughness and corrosion were studied as a series of basic studies for optimizing the concentrations of minor alloying elements. Toughness was closely related to the formation of an angular shaped inclusion(TiN) rather than the concentration of Ti. It is due to that the edge of TiN acts as a stress concentrator. In addition, TiN on surface induces surface defect during mechanical deformation, providing a site for corrosion. It seems to be contradictory to the fact that titanium removes sulfur in steels and improves corrosion resistance. However, electrochemical noise(EN) tests showed that titanium added as much as not forming large angular TiN did not deteriorate corrosion resistance. Hence, the addition of Ti is expected to improve corrosion resistance without degrading toughness if titanium is added under the controls to prevent TiN from forming.
재부동태 속도를 이용한 스테인리스강의 응력부식 민감성 예측
金熙山,金星猷 弘益大學校 産業技術硏究所 2004 産業技術 Vol.14 No.-
The recent development of method analyzing repassivation rate using a rapid scratch test and high field conduction model in which log i(t) is proportional to 1/q(t), makes it possible to predict SCC susceptibility more quantitatively, as well as to conduct the test more easily from the viewpoint of cost and timesaving. Since scratched surface is affected by the shape of scratching tip as well as mechanical properties, the inconsistency of scratched surface area having significant influence on the analyzed repassivation rate causes it difficult to distinguish the repassivation rates with a little difference. The validity of the proposed test was confirmed by examination of the effect of the alloy elements(W, Ni) on the repassivation rates of ferritic stainless steels obtained from both rapid scratch tests and the proposed tests.
염수 및 Sour gas환경에서 고 망간강의 내식성에 미치는 합금원소 Mn, Cr의 영향
김희산,현영민,이순기 한국표면공학회 2013 한국표면공학회 학술발표회 초록집 Vol.2013 No.5
자동차 및 에너지 산업의 적용을 목표로 고망간강의 기계적 성질 향상 연구가 활발히 진행된 반면 내식성 연구는 미비하다. 본 연구에서는 염수 환경 및 H2S 환경에서 4종의 고망간강의 내식성에 미치는 크롬 및 망간의 영향을 조사하였다. 비교재로 사용된 탄소강 대비 실험재의 부식 속도는 침지 실험을 통해 얻어졌다. 또한 내식성 기구 고찰을 위하여 상평형 프로그램을 통하여 녹 층을 예측하고, 침지실험으로부터 얻어진 녹 층을 XRD, SEM-EDS 및 TEM-EDS로 분석하였다. 3.5% NaCl 용액에서 크롬 및 망간이 모두 내식성을 향상시킨 반면, synthetic seawater에서는 크롬만이 내식성을 향상시켰다. 또한 이들 염수 환경과 달리 H2S 환경에서 크롬과 망간 모두 내식성을 향상시키지 못했다. 환경에 따라 강의 내식성에 미치는 합금 원소의 영향이 상이한 원인은 각각의 환경에서 형성된 녹층의 구성 물질의 차이에 의한 것으로 이에 대하여는 본문의 된 녹 층 분석 결과에서 자세히 설명되었다.