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저 합금강재(2.25Cr-1.0Mo) 반복 보수용접 열영향부의 특성
이철구,안종석,이남혁,이길재,Lee, Chul-Ku,Ahn, Jong-Seok,Lee, Nam-Hyuck,Lee, Gil-Jae 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.1
A low alloy-steel(2.25Cr-1.0Mo) has been widely used for boiler piping, header and tubes in high temperature and pressure conditions of the thermal power plant. It is common knowledge that the repair welding is permitted two or three times by customary practice rule, but there is no regulation to limit the number of repair welding base on the study heat-affected zone(HAZ), which is the weakest zone when repair welding is under taken, by experiments about the metallographic degradation and mechanical properties. Therefore, this study aims to verify the reliability of 5 times repair welding through conducting the experimental observation in the mechanical and the metallographic change on HAZ varying repair welding times. In results of the experiments, it is concluded that the reliability was kept in HAZ even up to the fifth repairs.
이철구,이우람,김진영,Lee, Chul-Ku,Lee, Woo-Ram,Kim, Jing-Young 한국생산제조학회 2009 한국생산제조학회지 Vol.25 No.1
An experimental study was performed to select cutting parameters for better quality-products in hard metals such as steels. Usually, a hard metal can be cut with a rotary cutting knife and the process provides a good cutting quality result. However, the cutting machine is much sensitive in cutting conditions because of its complicated mechanism. By this reason, careful processing conditions must be taken to improve the quality of the products. This experimental study for better quality products with a rotary cutting knife was carried out with two main factors; cutting speeds and cutting and pooling forces. A two-dimensional profile measuring instrument is used to evaluate its cutting faces and the effects of processing factors are analyzed by a commercial software.
이종재료의 피복아크 용접에서 자기력에 따른 LIBS 해석
이철구,이우람,Lee, Chul Ku,Lee, Wooram 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.4
This paper reports mild steel(SPHC) and stainless steel(STS304) sheets commonly used for railroad cars or commercial vehicles such as in the automobile and shipbuilding industries. The sheets are used in these applications, which are mainly fabricated using the shielded metal arc welding(SMAW) of dissimilar materials. It also reports an interesting application of Laser Induced Breakdown Spectroscopy(LIBS) in order to determine the elemental composition diffusion of SPHC and STS304. Arc blow produced by magnetic force during the electric arc welding prevents the formation from a sound weldment. In particular, the mechanical properties of the joint are influenced by not only by geometrical and mechanical factors but also the welding conditions for the arc welded joint. Therefore, the mechanical properties and performance are evaluated by performing a physicochemical component analysis. And they increase in accordance with content of elements and microstructure in mild steel. As results, appropriate range for magnetic fields could be achieved. Therefore, the effect of magnetic force in a butt weld of mild steel plates was investigated by comparing to the measured data.
Nd:YAG 레이저를 이용한 냉연강판과 스테인레스강판의 용접
이철구,이우람,백운학,Lee, Chul-Ku,Lee, Woo-Ram,Baek, Un-Hak 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.2
We have studied on welding dissimilar materials of cold-reduced carbon steel sheet and stainless steel sheet together by using laser beam. It is well known that stainless steel is so strong againt rust and heat, while cold-reduced carbon steel is widely used in various parts of industry. In this research we have performed some experiments to know the possibility of welding dissimilar materials using laser beam by adjusting the power output of 3kW laser. Other conditions of the experiments were as follows : the welding speed was varied in the range between 2m/min and 7m/min, argon gas and helium gas were used as shield gas, the flow value of shield gas was ranged between $10{\ell}/min$ and $30{\ell}/min$, and the gap of two materials was ranged between 0mm and 0.3mm. In order to ascertain of the welded surface, we have done the tensile strength testing, the hardness testing and the microscope observation. As a result, we have found that tensile strength was the highest at the condition of the welding speed of 4, the flow value of $20{\ell}/min$, the gap of two materials 0, and the use of helium gas. Above testings have also showed that the tensile strength was generally satisfactory since the penetration of welding was almost complete due to the thinness of the materials. In addition, the formation of the welded area was excellent when it had the highest tensile strength.
AISI 316L 클래드강의 맞대기 용접부 입계부식과 예민화 거동에 관한 연구
이철구,박재원,Lee, Chul-Ku,Park, Jae-Won 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.2
We have investigated traits of clad metals in hot-rolled clad steel plates, sensitization and mechanical properties of STS 316 steel plate and carbon steel(A516). Clad steel plates were butt-weld by SAW+SMAW, and with the time of heat treatment as the variable, heat treatment was conducted at $625^{\circ}C$, for 80, 160, 320, 640, 1280 minutes. As a way to evaluate it, sectioned weldments and external surfaces were investigated to reveal the degree of sensitization by mechanical property, etching and those of EPR test, results were compared with it. In short, the purpose of this study is suggesting some considerations in developing on-site techniques to evaluate the sensitization of stainless steels.