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고주파 유도가열을 이용한 철강재의 마찰교반용접 특성평가
천현필(Jason Cheon),박태순(Taesoon Park),윤진영(Jin-young Yoon),김철희(Cheolhee Kim) 대한용접·접합학회 2019 대한용접·접합학회지 Vol.37 No.5
Friction stir welding of carbon steel causes tool wear and system deformation issues because of its relatively high strength compared to aluminum. As a countermeasure, additional high-frequency induction heating is suggested to solve this problem. An inline high-frequency induction heating assisted friction stir welding process was studied on 450 MPa and 980 MPa grade carbon steel sheets. As a pre-experiment, the heating performance of the high-frequency induction heating system was quantified. Then the effective welding speed range, vertical load history, and weldment performance were investigated to evaluate the characteristics of the process. Those results were compared with a conventional friction stir welding process conducted under equivalent process conditions. For the 440 MPa steel, about 40% faster maximum welding speed was achieved by applying the 4 kW induction heating. No tensile strength degradation of the weldment was found. Also, the maximum vertical load was decreased by 26% compared to the conventional friction stir welding process. No significant degradation of hardness was observed in the welds on 440 MPa and 980 MPa steel.
레이저빔 용접과 마찰교반용접을 이용한 6천 및 7천계열 알루미늄 판재 접합부의 인장강도비교
천현필(Jason Cheon),강민정(Minjung Kang),윤진영(Jin-young Yoon),김철희(Cheolhee Kim) 대한용접·접합학회 2019 대한용접·접합학회지 Vol.37 No.3
Due to the high thermal diffusivity and metallurgical sensitivity, the proper welding processes of the aluminum are required. The Laser beam welding and friction stir welding processes have been focused as the appropriated welding processes for aluminum. The heat treated 6xxx series and 7xxx series aluminum sheet were welded by the laser beam welding and friction stir welding processes. Also, the effects of heat input through the welding parameters were investigated. The tensile strength of weldments was evaluated respectively and compared by the processes and heat input level. The insignificant tensile strength differences were found for the 6xxx series by the welding processes. However, the friction stir welded 7xxx series weldments were shown 82~89% joint efficiency while laser beam welded weldment were shown 48~58%. Overall, the effect of heat input level was not revealed in this experiment range. The degradations in hardness of weldments tended to be in proportion to the joint efficiency loss.
동축 고주파 유도가열 하이브리드 마찰교반용접의 고강도강 적용 특성평가
윤진영(Jin-young Yoon),천현필(Jason Cheon),김철희(Cheolhee Kim) 대한용접·접합학회 2019 대한용접·접합학회지 Vol.37 No.6
The thermo-mechanical properties of high strength steel limit the use of the friction stir welding(FSW) process in terms of quality and productivity. In this study, hybrid FSW(HFSW) using coaxial induction heating was designed to be applied to high strength steel and to ensure directional flexibility. The performance and characteristics of the HFSW process were evaluated on 590 and 980 dual phased high strength steel. The range of welding speeds adequate for the FSW and HFSW processes were compared, to evaluate the productivity of the HFSW process. During FSW, system deflection, vertical load and torque were measured to understand the process behavior. In HFSW, welding speeds were increased by 75% and 50%, respectively, for 590 DP and 980 DP steels compared to the conventional FSW processes. Furthermore, a relatively deeper heat-affected zone was achieved. The deeper heat-affected zone was produced by deeper tool plunging depth due to reduced system deflection. Earlier stabilization of the vertical load and torque is another feature of HFSW, due to the preheating effect. Employing the HFSW process, with its simple system configuration and process flexibility, can improve productivity and quality for welding high strength steels.