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RISS 인기검색어
- 검색키워드
- 저자 : 안현모(Hyun-Mo Ann) (검색결과 3 건)
- 무료
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HT 후판강재의 용접 열영향부(HAZ)에서 발생하는 용접균열의 민감도에 관한 고찰
안현모(Hyun-Mo Ann),이종식(Jong-Sik Lee) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.1
The welding crack susceptibility around of heat affected zone in welded thick(HT80 steel) joint is very important, and especially the welded structure for industrial structure such as plant, shipping, bulding, car parts welding is needed various welding method. In joining method of welding structure, welding residual stresses inevitably occur welded joints after welding, the evaluation of welding cracking susceptibility in HT80 steel was performed using thermally simulated heat affected zones. So, this paper deals with investigations into the testing of electric shield metal arc welding(SMAW) process that is frequently in welding HT80 steel that are quenched and tempered after welding. It has been carried out to study the weldability using test of welded specimen in welding cracking of HT80 steel that frequently occur after reheating. Also, are selected for examining the mechanism of welding crack-occurrence and way to reliability in cracking of the welded metal. This examinations were carried out in terms of micro-structural characterization, micro-hardness measurement and welded bend test. It was found that welding cracking susceptibility increased as hardness increased and cooling speed of weld heat cycle, Cooling curve Diagram HT80 steel shows what can be prevented in the weld metal and heat-affected zone when be controlled by hardness value in heat treatment from 800℃ to 500℃, and welding crack susceptibility of HT80 is not occur when bead pass below about multi 10 pass. It evident that welding cracking susceptibility can be eliminated or reduced by controlling the welding parameters such as the realation of cooling cycly, max. hardness value in HAZ, affect of residual stress according to reheating cycle or In view of the results, welding crack is not occur below about 490MPa(50kgf/mm2) in reinforcement and welding pass is below about 10 pass. For the improving of Welding crack can be controlled of various parameters(decrease of HAZ hardness, stress-relief in HAZ, micro-structural characterization, cooling cycle, etc.) in welding.
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마찰교반용접(FSW)을 이용한 Cu/Al 이종합금 용접의 특성
이종식(Jong Sik Lee),안현모(Hyun Mo Ann) 산업기술교육훈련학회 2018 산업기술연구논문지 (JITR) Vol.23 No.3
In this research paper, we evaluated the weldability of dissimilar materials, copper and aluminum, using friction stir welding (FSW), The specimens used to perform FSW were a copper plate material (2 mm thick) and an aluminum plate material (2 mm thick). The two joining configurations, butt joint and lap joint, were welded using FSW. In order to investigate the weldability of the joints, hardness and tensile tests were carried out on the base material, heat affected zone (HAZ), thermo-mechanically affected zone (TMAZ), and stir zone (SZ). Optical microscopy was also performed to investigate the microstructure of joints. As a result of these tests, the yield strength and tensile strength of the lap joint were measured to be lower than the butt joint. Additionally, these tests caused the center part to elongate in fibrous shape and the heat-affected part was easily broken, resulting in the appearance of a dimple type fracture surface and a microstructure. In the lap joint, specimens showed the cleaved fracture surface with Chevron V-type mark that appeared in the brittle fracture at the shear stage. The analysis of the friction stir welds showed a finer structure than the base metals. Furthermore, the results revealed that the butt joint welds tend to appear clearly than the lap joint welds due to the rotational speed of the tool during the friction welding. Specifically, butt joints exhibited better mechanical and structural properties than lap joints.
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마찰교반용접(FSW)을 이용한 순 티타늄 판재의 용접부 특성 대한 연구
이종식(Jong-Sik Lee),안현모(Hyun-Mo Ann) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.4
Titanium and titanium alloy is widely used in heat exchangers due to its unique character of corrosion resistance from the sea water and big in specific strength. Especially the pure titanium is optimum to make heat exchange panels, as pure titanium is good for mold-ability. However there is a potential risk of a flaw in welding when using titanium, due to its strong chemical attraction with oxygen, nitrogen and hydrogen and the characteristic of welded part which is weaker and lighter compared to the deposited metal zone and the parent metal. As a consequence, instead of typical connection methods of fusion welding such as MIG (metal inert gas), TIG (tungsten inert gas) welding, GMAW(gas metal arc welding), laser welding or electron beam welding, the friction stir welding is perceived as more eco friendly, and economic connection method since it is unnecessary to use additional heat source, welding rod and filler metal, as well as there is no spatter, harmful ray or material while connecting. Friction stir welding is when materials near the tool area becomes soften by the friction heat occurred from the friction between the tool and binder, while the materials on the sides of the composite plane are forced to blend by the plastic deformation and flow from the rotary motion of the tool, and the binder joints after cool down. There are 4 major types of titanium – pure titanium, α alloy, α+β alloy and β alloy. Pure titanium Grade 2, one of the most popularly used types of titanium also has been used in this study. Angle butt joint and lap joint of 2mm thick pure titanium panels will be executed using friction stir welding, and then a macroscopic observation will be undertaken about each welding method’s micro Vickers hardness test, maximum load resistance test, the ultimate strength, stress-strain diagram, of the welded part using the produced specimen. The examination results of the tension test, hardness test and modified structure after the execution of butt joint and lap joint friction stir welding using the pure titanium panels are as follow: ⑴ The result demonstrated that the tension and hardness under lap joint welding measured lower than butt joint welding, as the tension force decreased due to the welded part highly affected by the friction heat which lead to weaken of it. ⑵ Having checked on the fractured part after the tension test, butt joint welding method showed typical dimple type refined structure due to ductile fracture while lap joint welding method showed cleavage type microstructural feature due to brittle fracture. ⑶Having observed on the microscopic organization after friction stir welding, it has been revealed that it transforms into a different structure from the parent metal. The structure on the stir zone becomes more fineness structural than the parent metal, and such incident happened more on the lap joint welding which has a higher revolution speed of welding roll. ⑷ When executing friction stir welding using 2mm thick pure titanium panel, butt joint welding seems to be more ideal than lap joint welding in terms of mechanical characterization and microstructural characterization.
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