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Cu-Sn 삽입금속을 이용한 DP강의 아크 브레이징 접합부의 미세조직과 인장특성
조욱제,조영호,윤중길,강정윤,Cho, Wook-Je,Cho, Young-Ho,Yun, Jung-Gil,Kang, Chung-Yun 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.1
The following results were obtained, microstructures and tensile properties in arc brazed joints of DP(dual phase) steel using Cu-5.3wt%Sn insert metal was investigated as function of brazing current. 1) The Fusion Zone was composed of ${\alpha}Fe+{\gamma}Cu$ and Cu23Sn2. The reason for the formation of these solid solutions. Despite, Fe & Cu were impossible to solid solution at room temperature. It's melting & reaction to something of insert metal & Base Metal (DP Steel) by Arc. Brazing Process has faster cooling rate then Cast Process, Supersaturated solid solution at room temperature. 2) The increase Hardness of Fusion Zone was directly proportional to the rise of welding current. Because, ${\alpha}Fe+{\gamma}Cu$ phase (higher hardness than the Cu23Sn2.(104.1Hv < 271.9Hv)) Volume fraction was Growth, due to increasing the amount of base metal melting by High current. 3) The results of tensile shear test by Brazing, All specimens happen to fracture in Fusion Zone. On the other hand, when Brazing Current increasing tend to rise tensile load. but it was very small, about 26-30% of the base metal. 4) The result of fracture analysis, The crack initiate at Triple Point for meet to Upper B.M/Under B.M/Fusion Zone. This Crack propagated to Fusion zone. So ruptured by tensile strength. The Reason to in the fusion zone fracture, Fusion zone by Brazing of hardness (strength) was very lower then the base metal (DP steel). In addition the Fusion Zone's thickness in triple point was thin than the base metal's thickness in triple point.
Ni가 첨가된 고망간 용접봉의 입열량에 따른 인장 특성과 미세조직의 영향
한일욱(Il-Wook Han),윤중길(Jung-Gil Yun),이봉근(Bong-Geun Lee),강정윤(Chung-Yun Kang) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.1
The cryogenic high manganese steel is designed for tanks that transport liquefied natural gas, which has increased in demand globally. For this purpose, high manganese steel weld wire with ni added for Flux Cored Wire welding was welded under various heat input conditions. Then, a tensile test was measured to evaluate the mechanical properties. As a result, the heat input condition satisfying the required yield strength was 1.5 kJ. The reason for this phenomenon is that a small amount of Cu contained in the base metal and the welding rod is generated in grain boundaries of Cu₂O during solidification, causing liquefaction cracking.
고(<24%)Mn 플럭스코어드와이어를 사용한 다층 용접 시 초층 응고조직의 결정면방위에 따른 미세조직과 경도
한일욱(Il-Wook Han),엄정복(Jung-Bok Eom),윤중길(Joong-Gil Yun),이봉근(Bong-Geun Lee),강정윤(Chung-Yun Kang) 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.5
In this study, Microstructure and hardness of 1st layer with crystallographic orientation were investigated about solidification structure in multipass weld using high Mn-Ni flux cored wire. Microstructure of solidification consisted of austenite matrix and a little ε-phase in grain boundaries. Orientation of grains was usually (001), (101), (111). According to crystallographic orientation, morphology of primary dendrite was different. The depletion of Fe and the segregation of Mn, C, Ni, Si, Cu, Cr, O were found along the grain boundaries. The area of segregation was wide with an order of (001), (101), (111) grains. And hardness of grains with crystallographic orientation increased with an order of (001), (101), (111) grains because of the segregation along dendrite boundary.
Yb:YAG 디스크 레이저로 표면 오버랩 용융된 냉간금형강, STD11의 미세조직과 경도
이광현(Kwang-Hyeon Lee),최성원(Seong-Won Choi),윤중길(Jung Gil Yun),오명환(Myeong-Hwan Oh),김병민(Byung Min Kim),강정윤(Chung-Yun Kang) 대한용접·접합학회 2015 대한용접·접합학회지 Vol.33 No.5
Laser surface Melting Process is getting hardening layer that has enough depth of hardening layer as well as no defects by melting surface of substrate. This study used CW(Continuous Wave) Yb:YAG and STD11. Laser beam speed, power and beam interval are fixed at 70㎜/sec, 2.8㎾ and 800㎛ respectively. Hardness in the weld zone are equal to 400Hv regardless of melting zone, remelting zone overlapped by next beam and HAZ. Similarly, microstructures in all weld zone consist of dendrite structure that arm spacing is 3~4㎛, matrix is γ(Austenite) and dendrite boundary consists of γ and M₇C₃ of eutectic phase. This microstructure crystallizes from liquid to γ of primary crystal and residual liquid forms γ and M₇C₃ of eutectic phase by eutectic reaction at 1266℃. After solidification is complete, primary crystal and eutectic phase remain at room temperature without phase transformation by quenching. On the other hand, microstructures of substrate consist of ferrite, fine M23C₆ and coarse M₇C₃ that have 210Hv. Microstructures in the HAZ consist of fine M23C₆ and coarse M₇C₃ like substrate. But, M23C6 increases and matrix was changed from ferrite to bainite that has hardness above 400Hv. Partial Melted Zone is formed between melting zone and HAZ. Partial Melted Zone near the melting zone consists of γ, M₇C₃ and martensite and Partial Melted Zone near the HAZ consists of eutectic phase around γ and M₇C₃. Hardness is maximum 557Hv in the partial melted zone.