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600㎫급 자동차용 고장력강판의 CO₂ 레이저 용접부의 특성에 미치는 보호가스의 영향
한태교(Tae-Kyo Han),이봉근(Bong-Keun Lee),강정윤(Chung-Yun Kang) 한국레이저가공학회 2004 한국레이저가공학회지 Vol.7 No.2
The effect of shield gas on the weldability, mechanical properties and formability of CO₂ laser weld joint in 600㎫ grade high strength steel was investigated. Bead on plate welds were made under various welding speed and shield gas. Tensile test was carried out under the load of perpendicular and parallel direction to the weld line. Formability of the joint was evaluated by Erichsen test.<BR> As the welding speed increases, the porosity fraction decreases. The porosity fraction in the joint used Ar-50%He mixed gas as a shield gas was lower than that of the joint used Ar gas. Hardness at the weld metal of full penetrated joint was nearly equal to that of water quenched raw metal. In a tensile test under a perpendicular load to the weld axis, strength and elongation of joint produced by optimum condition were nearly equal to those of base metal. However, the strength of joint in a tensile test under a parallel load to weld axis was higher than that of raw metal, but the elongation of joint was lower than that of raw metal. Elongation and formability were further increased by the method of using Ar+He mixed gas as a shield gas as compared with Ar gas. Formabilities of joints were recorded ranging from 58% to 70% of that of base metal with different shield gases.
600MPa급 TRIP강의 $CO_2$ 및 Nd:YAG 레이저 용접부의 특성
한태교,김성준,이봉근,김대업,강정윤,Han, Tae-Kyo,Kim, Seung-Jun,Lee, Bong-Keun,Kim, Dae-Up,Kang, Chung-Yun 대한용접접합학회 2006 대한용접·접합학회지 Vol.24 No.1
The characteristics of $CO_2$ or Nd:YAG laser welded 600MPa ade TRIP steel was investigated. He or Ar gas was used as a shield gas in case of $CO_2$ laser welding, but the shield gas was not used in case of Nd:YAG laser welding. Bead on plate welding was performed with various welding conditions. Defects in the joints of both welding type occurred at 1.8m/min but were not observed over the welding speed of 2.1m/min in case of Nd:YAG laser welding. However, porosity occurred in $CO_2$ laser welding and the tendency of decreasing with the increase of welding speed. The hardness was the highest at heat affected zone near fusion zone as well as at the fusion zone and decreased on approaching the base metal. In a perpendicular tensile test to the weld line, all specimens that have been welded at optimum conditions were fractured at the base metal, and the tensile properties showed the rather higher than those of raw material. In a parallel tensile test, the strength of the joints was higher than that of the base metal. Elongation was found to be lower than that of the raw material. Forming height by Erichsen test and elongation were deeply related with the ratio of base metal/weld metal and the maximum hardness of the weld metal. Also porosity induced to decrease the strength and the elongation. The maximum formability was recorded at approximately 80% as compared with that of the raw material with the optimum condition.
정태교 ( Tae Kyo Chung ),현성열 ( Sung Youl Hyun ),김진주 ( Jin Joo Kim ),류일 ( Eell Ryoo ),이근 ( Kun Lee ),조진성 ( Jin Seung Cho ),황성연 ( Sung Yun Hwang ),이석기 ( Suk Ki Lee ) 대한외상학회 2005 大韓外傷學會誌 Vol.18 No.2
Background: Blunt thoracic trauma in children has a high morbidity and mortality. In this study, we assessed the significance of the injury pattern, mechanism and initial status in emergency department on severity and prognosis in pediatric blunt thoracic trauma patients. Method: We retrospectively reviewed medical records and chest X-ray and CT images of 111 pediatric blunt thoracic trauma patients from October 2000 to June 2005. Data recorded age, gender, season, injury mechanism, injury pattern, associated injury, length of hospital stay and cause of death. Result: Of all 111 patients, 68 patients were injured by motor vehicle accidents, 30 were falls, 5 were motorcycle accidents, 3 were sports accidents and 5 were miscellaneous. In thoracic trauma, single injury of lung contusion were 35 patients and 32 patients had multiple thoracic injuries. Hospital stay in school age group were longer than preschool age group. The causes of death were brain injury in 9, respiratory distress in 4, and hypovolemic shock in 2 patients. Emergently transfused and mechanically ventilated patients had higher mortality rates than other patients. Patients required emergency operation and patients with multiple thoracic injuries had higher mortality rates. Conclusion: In this study, patients with combined injury, emergency transfusion, mechanical ventilation, emergency operation, multiple injuries in chest X-ray had higher mortality rates. Therefore in these pediatric blunt thoracic trauma patients, accurate initial diagnosis and proper management is required.
Ca(OH)<sub>2</sub>를 이용한 레늄 산화물의 포집반응 특성 연구
이태교 ( Tae-kyo Lee ),은희철 ( Hee-chul Eun ),최정훈 ( Jung-hoon Choi ),이기락 ( Ki-rak Lee ),한승엽 ( Seung-youb Han ),박환서 ( Hwan-seo Park ) 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.1
The objective of this study was to obtain basic data for trapping gaseous technetium (Tc) oxide generated from the voloxidation process in spent nuclear fuel pyroprocessing. Rhenium (Re) and Ca(OH)<sub>2</sub> were used as surrogates for the technetium and a trapping material, respectively. The trapping characteristics of rhenium oxide were investigated with changing temperatures and molar ratios of calcium (Ca) over rhenium, and the thermal behaviors of the trapping products were observed. The products following after the trapping test were identified as Ca(ReO<sub>4</sub>)<sub>2</sub> and Ca<sub>5</sub>Re<sub>2</sub>O<sub>12</sub>. The conversion to Ca5Re<sub>2</sub>O<sub>12</sub> was preferred with increasing temperatures, and the trapping products were completely converted into Ca<sub>5</sub>Re<sub>2</sub>O<sub>12</sub> under conditions exceeding 800 ℃, or when maintained at 750 ℃ for 4 hr. The trapping efficiency at a molar ratio of 2.5 (Ca:Re=5:2) was significantly superior to that at the molar ratio of 2. (Received July 6, 2016; Accepted July 29, 2016)