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열교환기용 BAS111합금 고주파유도용접관에서 인발조건이 기계적 특성에 미치는 영향
국진선,김낙찬,송중근,전동태 대한용접접합학회 2004 대한용접·접합학회지 Vol.22 No.4
The aim of this study is to investigate the optimum drawing parameter for BAS111 welded tubes. The BAS111 aluminium alloy tubes with 25.4mm in external diameter and 1.5mm in thickness for heat-exchangers were manufactured by high frequency induction welding with the V shaped convergence angle 6.8$^{\circ}$ and power input 50㎾. With increasing the reduction of area (1.6, 5.8, 11.5, 14.2, 18.5, 22.5%) by drawing, tensile strength was increased and elongation was decreased. With increasing the reduction of area by drawing, hardness in weld metal increased rapidly, while that of base metal increased slowly. In the specimen with the outer diameter smaller than 22mm, hardness of weld metal was higher than that of base metal. The optimum drawing parameter of area reduction was estimated about 15% because of the work hardening of welds.
MR-EMR 복합공정에 의한 탄탈륨분말의 제조시 과잉첨가 환원제 양에 따른 분말의 특성
배인성,윤재식,박형호,김병일,이현우,김낙찬,설경원 한국분말야금학회 2004 한국분말재료학회지 (KPMI) Vol.11 No.4
In this study, tantalum powder has been producted by MR-EMR combination process. MR-EMR combination process is a method that is able to improve demerits of MR(metallothermic reduction) and EMR(electronically mediated reaction) process. This study examined the characteristics of powder with the amount of reductant excess using $K_2$TaF$_{7}$ as feed materials, Na as a reductant and KCl/KF as a diluent. In addition, this study examined acid treatment that affect the high purification of powder. The impurities contained in powder was removed in various conditions of acid treatment. The total charge passed through external circuit and average particle size(FSSS) were increased with increasing amount of sodium excess. The proportion of fine particle(-325mesh) was decreased with increasing amount of sodium excess. The yield was improved from 70% to 76% with increasing amount of sodium excess. Considering the impurities, charge, morphology, particle size and yield, an amount of sodium excess of 10wt% were found to be optimum conditions for MR-EMR combination process.s.