http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
조선용강재의 레이저-아크 하이브리드 용접금속부 충격인성에 미치는 용접변수의 영향
홍승갑,이종봉,Hong, Seung-Gab,Lee, Jong-Bong 대한용접접합학회 2006 대한용접·접합학회지 Vol.24 No.6
Since the 1990's, European shipbuilding industries introduced hybrid welding process in order to decrease thermal distortion of welded joints in passenger shipbuilding. In this study, we investigated effects of hybrid welding parameters on the toughness of weld metal using DH36 steel in order to obtain more sound welds in passenger shipbuilding. Type of leading process, joint gap distance and chemical composition of consumables were considerably correlated with the toughness of weld metal. Especially, the toughness was considerably increased with high-Ti containing consumables. In addition, hybrid welding speed increased by using plasma cut edges, the oxides layer of which increased absorption efficiency of laser beam.
슈퍼 듀플렉스 스테인리스강(UNS S32506) 레이저 조관용접 튜브의 용접 후 열처리에 따른 부식거동
조동민(Dong Min Cho),박진성(Jin-seong Park),홍승갑(Seung Gab Hong),황중기(Joong-Ki Hwang),김성진(Sung Jin Kim) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.3
The corrosion behaviors of laser-welded super duplex stainless steel tubes with post-weld heat treatment(PWHT) conditions(950, 1000, 1050, 1100 ℃ for 5 and 30 min) were evaluated by electrochemical potentiodynamic polarization and critical pitting temperature measurements. This study showed that the critical metallurgical factors affecting the degradation of corrosion resistance of a steel tube in as-welded condition were the unbalanced phase fraction(ferrite:austenite = 94:4), Cr₂N precipitation, and phase transformation from the austenite phase to ɛ-martensite(via stress-induced phase transformation). The improvement in the corrosion resistance of the welded specimen depends greatly on the PWHT conditions. The specimens after PWHT conducted below 1000 ℃ showed inferior corrosion resistance, caused by precipitation of the sigma phase enriched with Cr and Mo. At 1100 ℃ for a longer duration in PWHT, the ferrite phase grows, and its fraction increases, leading to an unbalanced phase fraction in the microstructure. As a result, pitting can be initiated primarily at the interface between the ferrite/austenite phase, particularly in base metal.
소둔 및 용접후열처리가 슈퍼 오스테나이트계 스테인리스강의 부식거동에 미치는 영향
윤덕빈 ( Duck Bin Yun ),박진성 ( Jin Sung Park ),조동민 ( Dong Min Cho ),홍승갑 ( Seung Gab Hong ),김성진 ( Sung Jin Kim ) 한국부식방식학회 2021 Corrosion Science and Technology Vol.20 No.6
The effect of two different annealing temperatures on the level of the second phase precipitated in the microstructure and the corrosion behaviors of super austenitic stainless steel were examined. The sample annealed at a higher temperature had a significantly lower fraction of the sigma phase enriched with Cr and Mo elements, showing more stable passivity behavior during the potentiodynamic polarization measurement. However, after the welding process with Inconel-type welding material, severe corrosion damage along the interface between the base metal and the weld metal was observed regardless of the annealing temperature. This was closely associated with the precipitation of the fine sigma phase with a high Mo concentration in the unmixed zone (UMZ) during the welding process, leading to the local depletion of Mo concentrations around the sigma phase. On the other hand, the fraction of the newly precipitated fine sigma phase in the UMZ was greatly reduced by post-weld heat treatment (PWHT), and the corrosion resistance was greatly improved. Based on the results, it is proposed that the alloy composition of welding materials and PWHT conditions should be further optimized to ensure the superior corrosion resistance of welded super austenitic stainless steel.
화력발전소용 슈퍼 듀플렉스 스테인리스 강(STS 329J4L) 조관 튜브 및 핀-튜브재의 부식거동
박진성 ( Jin Sung Park ),김용현 ( Yong Hyeon Kim ),홍승갑 ( Seung Gab Hong ),김성진 ( Sung Jin Kim ) 한국부식방식학회 2023 Corrosion Science and Technology Vol.22 No.6
Corrosion behaviors of laser-welded super duplex stainless steel (SDSS) tubes after exposure to an actual power plant environment for one year and those of fin-tube welded SDSS were evaluated. Results showed that corrosion damage on the back side of the SDSS tube in the direction of hot air was higher than that on the front side regardless of weldment location. However, corrosion damage showed no difference between weldment and base metal due to recovery of phase fraction in the weldment through post weld heat treatment (PWHT). Nevertheless, the SDSS tube showed severe corrosion damage along grain boundary due to surface phase transformation (δ → γ) and Cr<sub>2</sub>N precipitation caused by PWHT with a high N<sub>2</sub> atmosphere. Corrosion resistance of the SDSS tube was recovered when degraded surface was removed. Corrosion sensitivity of a fin-tube increased significantly due to pre-existing crevice, unbalanced phase fraction, and σ phase precipitation adjacent to the fusion line. Although corrosion resistance was improved by recovered phase fraction and sufficient dissolution of σ phase during PWHT, corrosion reaction was concentrated at the pre-existing crevice. These results suggest that welding conditions for fin-tube steel should be optimized to improve corrosion resistance by removing pre-existing crevice in the weldment.
화력발전용 슈퍼 듀플렉스 스테인리스 강 조관재의 용접 후 열처리 조건이 국부부식 저항성에 미치는 영향
이준호(Jun Ho Lee),박진성(Jin sung Park),조동민(Dong Min Cho),홍승갑(Seung Gab Hong),김성진(Sung Jin Kim) 한국표면공학회 2021 한국표면공학회지 Vol.54 No.5
This study examined the influence of post weld heat treatment (PWHT) conditions on corrosion behaviors of laser-welded super duplex stainless steel tube. Due to the high cooling rate of laser welding, the phase fraction of ferrite and austenite in the weld metal became unbalanced significantly. In addition, the Cr₂N particles were precipitated adjacent to the fusion line, which can be susceptible to the localized corrosion. On the other hand, the phase fraction in the weld metal was restored at a ratio of 5:5 when exposed to temperatures above 1060 ℃ during the post weld heat treatment. Nevertheless, the high beltline speed during the PWHT, leading to the insufficient cooling rate, caused a precipitation of σ phase at the interface between ferrite/austenite in both weld metal and base metal. This resulted in the severe corrosion damages and significant decrease in critical pitting temperature (CPT), which was even lower than that measured in as-welded condition. Moreover, the fraction of σ phase in the center region of post weld heat treated steel tube was obtained to be higher than in the surface region. These results suggest that the PWHT conditions for the steel tube should be optimized to ensure the high corrosion resistance by excluding the precipitation of σ phase even in center region.
고강도 9Cr-0.5Mo-1.8WVNb 강의 미세구조와 기계적 특성에 미치는 W 효과
박찬경,홍승갑,이원범 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.9
The microstructure and mechanical properties of high strength 9Cr-0.5Mo-1.8WVNb steel have been investigated to identify the effects of W addition into the 9Cr-1MoVNb steel. The W-added Cr-Mo steel (9Cr-0.5Mo-1.8WVNb) revealed better high-temperature tensile strength regardless of tempering temperature, but exhibited somewhat brittle fracture at higher tempering temperature region, in comparison to those of 9Cr-1MoVNb steel. Transmission electron microscopy also revealed that the evolution of polygonized substructures was delayed by the W addition. The EDS analysis on the structural change of the precipitates, especially (Cr,Fe)₂(C,N), indicated that the W addition increased the ratio of Cr/Fe of (Cr,Fe)₂(C,N), resulting in the stabilization of (Cr,Fe)₂(C,N) through the lattice expansion. It is believed that the stabilized (Cr,Fe)₂(C,N) can enhance the pinning effects on both the movement of dislocation and the growth of lath boundaries. Therefore, it is concluded that the enhanced high-temperature strength of the 9Cr-0.5Mo-1.8WVNb steel is mainly attributed to the retardation of dislocation recovery and the stabilization of carbo-nitrides, caused by the W addition.
열간 압연된 Cr-Mo 첨가 내화강의 탄화물과 고온 강도의 변화
박성호,김기호,박찬경,홍승갑,이원범 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.3
The effects of Mo addition on both the precipitation kinetics of Nb carbide and the high temperature strength have been investigated in hot rolled HSLA steels containing Cr and Mo. These steels were hot-rolled and coiled at 550, 600, and 650℃ respectively. Microstructural analysis of the carbides has been made using Field-Emission-Gun TEM attached EDS. The steels containing Cr and Mo exhibited higher strengths both at room temperature and high temperature(600℃) in comparison to the conventional HSLA steel containing only Cr. Refined bainitic structure could be obtained in the Cr-Mo contained steels due to the increase of hardenability and the fraction of bainitic phase increased with the increase of Mo content. TEM observations revealed that the Cr-Mo contained steels exhibited fine($lt;10 nm) and uniformly distributed Nb carbides, while the Cr contained steel exhibited coarse and sparsely distributed. The EDS analysis also indicated that the fine carbides was composed of complex form of carbide (Nb, Mo)C and the Mo content was higher in the finer carbides. The results clearly indicated that the addition of Mo affected the initial stage of Nb carbide precipitation. That is, Mo caused both transformation hardening and the uniform distribution of fine Nb carbides.