• 한국산학기술학회논문지
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• 제13권6호
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• pp.2465-2471
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• 2012

선박이나 심해저 해양플랜트와 같이 가혹한 해양환경에서 사용되는 강구조물에서 부식피로는 설계수명과 관련하여 해결을 요하는 중요한 문제이다. 본 연구에서는 전기방식중 과도한 전기방식이 부식피로균열 전파거동에 미치는 영향을 고찰하기 위하여 근래 사용이 확대되고 있는 고장력 TMCP에 대하여 합성해수중 -950mV vs. SCE의 과방식 인가전압 환경에서 부식피로균열 전파시험을 실시하고 da/dN-${\Delta}K$ 선도를 구하였다. 이 선도에서 저 ${\Delta}K$ 영역에서는 해수중 전파속도보다 빠른 균열전파속도를 나타내었으나, 고 ${\Delta}K$영역으로 갈수록 해수중 보다 늦은 균열전파속도를 나타내었다. 부식피로균열 전파속도에 영향을 미치는 인자로서 가속요인과 감속요인으로 나누고 각각 수소기체와 석회질생성물의 역할에 대하여 고찰하였다.

• 한국산업융합학회 논문집
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• 제26권1호
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• pp.87-94
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• 2023

TMCP(Thermo Mechanical Control Process) steel was continuously cast (CC) by varying the argon gas flow rate and vacuum time in the Ruhrstahl Heraeus (RH) refining process. Using the CC specimens, the distribution of the inclusions and the mechanical properties were evaluated. A lot of oxides and Al-O type inclusions were observed. The average Vickers hardness did not show a constant, but showed dispersion in a certain range. The shape and scale parameters of the CC specimen with an argon gas flow rate of 160Nm³ and a vacuum time of 12 minutes was the best. Mechanical properties (tensile strength, yield strength and elongation) were consistent with the Weibull probability distribution analysis results. The impact resistance was the best for CC specimens with an argon flow rate of 140 Nm³ and a vacuum time of 12 minutes. Although the inclusions and mechanical properties of the CC specimens were evaluated according to the argon gas flow rate and vacuum time, these values were no significant difference.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.79-81
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• 2005

Bridges constructed recently are preferred to have long spans and simple structure details considering not only the function as bridge but scenic beauty, maintenance, construction term and life cycle cost, etc. Therefore, they require high performance steels like extra-thick plate steels and TMCP steels. A TMCP steel produced by themo-mechanical control process is now spot lighted due to the weldability for less carbon equivalent. It improved at strength and toughness in microstructure. Recently, the SM570-TMC steel which is a high strength TMCP steel whose tensile strength is 600MPa has been developed and applied to steel structures. But, for the application of this steel to steel structures, it is necessary to elucidate not only the material characteristics but also the mechanical characteristic of welded joints. In this study, the characteristics of residual stresses in welded joints of SM570-TMC steel were studied through the three-dimensional thermal elastic-plastic analyses on the basis of mechanical properties at high temperatures obtained from the elevated temperature tensile test.

• Journal of Welding and Joining
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• 제7권3호
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• pp.44-54
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• 1989

This study was undertaken to evaluate the allowable welding heat input range for high strength steels manufactured by various processes and to compare the weldability of TMCP steel for high heat input welding with that of conventional Ti-added normalized steel. The allowable welding heat input ranges for conventional 50kg/$mm^2$ steel to guarantee D or E grade of ship structural steel were below 150 and 80kJ/cm respectively. Such a limit in welding heat input was closely related with the formation of undesirable microstructures, such as grain boundary ferrite and ferrite side plate in the coarse grain HAZ. In case of 60 and 80kg/$mm^2$ quenched and tempered steels, for securing toughness in weldments over toughness requirements for base metal, each welding heat input had to be restricted below 60 and 40kJ/cm, that was mainly due to coarsened polygonal ferrite in weld metal and lower temperature transformation products in coarse grain HAZ. The TMCP steel could be appropriate as a grade E ship hull steel up to 200kJ/cm, but the Ti-added normalized steel could be applied only below 130kJ/cm under the same rule. This difference was partly owing to whether uniform and fine intragranular ferrite microstructure was well developed in HAZ or not.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.93-93
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• 2009

본 연구에서는 EGW, FCAW 공정 적용에 따른 고강도 극후판 EH36-TMCP강 용접부의 역학적 거동 및 파괴인성 $K_{IC}$ 을 규명하기 위해, 먼저 열분포, 열탄소성 수치해석을 통하여 용접부의 역학적 거동(용접잔류응력, 소성변형율 등의 크기, 분포, 발생기구)을 고찰하였다. 그리고 이때 얻어진 잔류응력을 초기응력으로 하여, 잔류응력과 외력의 복합하중에 대한 파괴인성 $K_{Ic}$ 특성을 해석하였다. 용접공정별 균열이 존재하는 용접부의 파괴기준을 살펴보면, EGW용접부의 경우가 FCAW용접부의 경우에 비해 균열의 성장이 다소 용이하여 $K_{IC}$ 값이 다소 낮게 나타났다. EGW용접부의 파괴인성 $K_{IC}$ 경우 중첩된 경우(복합하중)가 순수 외력만 작용하는 경우보다 파괴 인성치가 다소 감소하는 경향을 보이고, a/W가 작을 경우 중첩의 경우가 순수 외력만의 경우보다 파괴인성치 차이가 크나, a/W가 증가함에 따라 그 차이가 점차 없어지는 것으로 나타났다. 반면, FCAW용접부의 경우 균열길이가 작은 범위에서는 중첩된 경우가 순수 외력만 작용 할 경우보다 파괴 인성치가 다소 증가함을 보이지만, a/W가 증가함에 따라 순수 외력만의 작용의 경우와 중첩의 경우의 파괴인성 차이가 없는 것으로 나타났다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1994년도 특별강연 및 추계학술발표 개요집
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• pp.35-37
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• 1994

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 춘계학술발표 개요집
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• pp.87-90
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• 1995

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1993년도 특별강연 및 추계학술발표 개요집
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• pp.133-136
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• 1993

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1993년도 특별강연 및 추계학술발표 개요집
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• pp.137-140
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• 1993

• Journal of Welding and Joining
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• 제26권3호
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• pp.51-60
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• 2008

This paper is to evaluate fracture characteristics of API 2W Gr.50 TMCP steel weldment typically applied for offshore structures, with the focus on the influence of heat input arising from flux cored arc welding. Based on the results and insights developed from this study, it is found that the toughness for both CTOD and impact exhibits a tendency to decrease as the weld heat input increases. The reheated zone of weldmetal exhibit lower hardness than solidified zone and microstructure that are liable to affect the toughness are acicular ferrite and martensite-austenite constituents (M-A). In particular, M-A is a more effective micro-phase for CTOD toughness than impact toughness.