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슈퍼 듀플렉스 스테인리스강 UNS S32750의 FCA 용접 후 열처리가 공식에 미치는 영향
장복수,문인준,김세철,고진현,Jang, Bok-Su,Moon, In-June,Kim, Se-Cheol,Koh, Jin-Hyun 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.5
This study was carried out to investigate the influence of a sigma phase precipitation on the pitting corrosion resistance and microstructural change of super duplex stainless steels(UNS S32750). The welds made by FCAW (Flux Cored Arc Welding) were heat treated ($930^{\circ}C$, $1080^{\circ}C$, $1230^{\circ}C$) and quenched. Based on the microstructural examination, it was found that the ${\sigma}$ phase was formed in base metals and welds heat treated at $930^{\circ}C$ while there were little ${\sigma}$phases formed in base metals and weld metal experienced the relatively fast cooling from $1080^{\circ}C$ and $1230^{\circ}C$. On the other hand, the most weight loss due to pitting corrosion occurred in base and weld metals heat treated at $930^{\circ}C$. It was confirmed that the pitting corrosion occurred in the phase boundaries of ferrite/sigma and austenite/sigma. The pitting corrosion resistance decreased owing to an increase in Cr, Mo depleted areas adjacent to the intermetallic phases such as ${\sigma}$phases. The hardness was greatly increased due to the precipitation ${\sigma}$phases.
CTCS(Condenser Tube Cleaning System) 튜브 스케일 제거용 스폰지 볼의 선별을 위한 Ball Sorter 개발
장복수 한국산업기술융합학회 2022 산업기술연구논문지 (JITR) Vol.27 No.2
This study has been conducted to develop a device that automatically removes foreign bodies and tube scale deposits by evaluating the effect on a sponge ball in a condenser tube. The device was used to increase thermal efficiency and involves the condensation of steam on a heat exchanger and condenser during turbine operation in nuclear and thermal power plants. In all experimental cases, the ball sorter satisfied all target achievement evaluation indicators of the ball sorter certification test, with sorting accuracy exceeding 95%, at a speed of 500 sponge balls per 15 min, and a noise of less than 85dB. .
슈퍼 듀플렉스 스테인리스강 UNS S32750의 FCA 다층 용접부의 용접 후 열처리 영향
장복수,문인준,임명진,김세철,김수성,이정원,박해웅,고진현,Jang, Bok-Su,Moon, In-June,Lim, Myung-Jin,Kim, Se-Cheol,Kim, Soo-Sung,Lee, Jung-Won,Park, Hai-Woong,Koh, Jin-Hyun 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.2
This study was carried out to investigate the effect of postweld heat treatment(PWHT, 930, 1080, $1230^{\circ}C$) on the microstructure, phase formation, pitting corrosion and mechanical properties such as hardness, tensile strength and impact values of super duplex stainless steel(UNS S32750) multipass welds. Based on the microstructural examination and X-ray diffraction analysis, it was found that the ${\sigma}$ phase was formed in the welds heat treated at $930^{\circ}C$ in which the ferrite content greatly decreased into 5~10% in the welds. The secondary austenite was formed in the reheated zone of welds and redissolved into ferrite with increasing heat treatment temperatures. The tensile strength and impact values of welds heat treated at $930^{\circ}C$ were the lowest and revealed the brittle fracture surface. The weight loss by pitting corrosion increased with test temperatures. It was confirmed that pitting corrosion occurred mainly in secondary austenite of reheated zones. The postweld heat treatment temperature is recommended to be in the range of $1050{\sim}1150^{\circ}C$.
아연도금강관의 가스메탈아크용접에서 용접인자가 기공형성에 미치는 영향
임영민,장복수,고진현,Lim, Young-Min,Jang, Bok-Su,Koh, Jin-Hyun 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.5
This study was carried out to investigate the effect of welding parameters such as shielding gas compositions welding voltage and welding current on the pore formation in the weld beads of galvanized steel pipes produced with gas metal arc welding. The porosity was evaluated and rated by metallography and radiographic test in terms of weight percentage, number and distribution of pores in weld beads. The porosity increased with increasing welding voltage and current, in which Ar gas produced the most porosity while $Ar+5%O_2$ generated the least porosity. It was found that the porosity could be reduced by selection of the proper gas mixture composition such as $Ar+5%O_2$ and $Ar+10%CO_2$ and by using current (130~150A) and voltage(16~20V).
슈퍼듀플렉스 스테인리스강 UNS S32750과 탄소강 A516-70의 이종금속 FCA 용접 특성에 대한 연구
문인준,장복수,김세철,고진현,Moon, In-June,Jang, Bok-Su,Kim, Se-Cheol,Koh, Jin-Hyun 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.4
The metallurgical and mechanical characteristics, toughness and corrosion resistance of dissimilar welds between super duplex stainless steel UNS S32750 and carbon steel ASTM A516Gr.70 have been evaluated. Three heat inputs of 21.12, 24.00, 26.88kJ/cm were employed to make joints of dissimilar metals with flux cored arc welding(FCAW). Based on microstructural examination, vermicular ferrite was formed in the first layer of weld at low heat input(21.12kJ/cm) and $Cr_{eq}/Ni_{eq}$ of 1.61 while acicular ferrite was formed in last layer of weld at high heat input(26.88kJ/cm) and $Cr_{eq}/Ni_{eq}$ of 1.72. Ferrite percentage in dissimilar welds was lowest in the first layer of weld regardless of heat inputs and it gradually increased in the second and third layers of weld. Heat affected zone showed higher hardness than the weld metal although reheated zone showed lower hardness than weld metal due to the formation of secondary austenite. Tensile strengths of dissimilar welds increased with heat input and there was 100MPa difference. The corrosion test by ferric chloride solution showed that carbon steel had poor corrosion resistance and pitting corrosion occurred in the first layer(root pass) of weld due to the presence of reheated zone where secondary austenite was formed. The salt spray test of carbon steel showed that the surface only corroded but the amount of weight loss was extremely low.
국정한,성호현,장복수,김남훈 한국기술교육대학교 2003 論文集 Vol.10 No.1
In this study, welding characteristic and mechanical properties of electro slag welding were systematically studied for SM490A and TMCP steel.In the electro slag welding which is widely used SM490A and TMCP steel materials are mainly used in a steel structures and complex building. As SM80G, ZO60 and SM70G are usually used welding wire. In this study, mechanical properties such as tensile strength, elongation and impact energy were measured for each welding conditions to determine the optimum processing conditions. In addition, hardness and microstructural analysis were conducted to characterize the welding properties. There results indicate that TMCP is suitable base material and SM80G, and ZO60 are the good welding electrodes for the electro slag welding.