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Effects of Fluoride in the Flux on Hydrogen Content in Weld Metal and Operating Behavior in FCAW-S
길웅,신명준,방국수 대한용접접합학회 2017 대한용접·접합학회지 Vol.35 No.5
Various fluorides, CaF2, K2SiF6, NaF, and LiF were added to self-shielded flux cored arc welding wires and their effects on the diffusible hydrogen content in the weld metal and the operating behavior were compared. Because of their easier vaporization and active reactions with hydrogen in the arc, K2SiF6, NaF, and LiF were more effective than CaF2 in reducing hydrogen content in weld metals. Even if slag basicity was varied from 1.92 to 2.53 depending on the fluoride added, no clear relationship was observed between the slag basicity and the hydrogen content, implying that a small variation of slag basicity has little influence on the hydrogen content in FCAW-S, which generates a large amount of gas during welding. The wires with K2SiF6, NaF, and LiF gave a more aggressive and violent arc, and resulted in a larger amount of spattering, especially large size spatters, than the wire with CaF2. It is believed that excessive volumes of vaporized gas in the wires with K2SiF6, NaF, and LiF hinder droplet detachment and lead to droplet of larger sizes. Moreover, the wires with K2SiF6, NaF, and LiF produced somewhat rough and irregular surfaces, having a slightly inconsistent bead height and width, resulting in restricted current and voltage ranges within which they can operate satisfactorily.
셀프실드용접 와이어의 Al 첨가량에 따른 용접금속 인성 및 기공형성 변화
방국수,박찬,길웅,장웅성,Bang, Kook-Soo,Park, Chan,Woong, Kil,Chang, Woong-Seong 대한용접접합학회 2011 대한용접·접합학회지 Vol.29 No.1
Three different welding wires were used to study the effects of Al content on weld metal toughness and porosity formation in self-shielded arc welding. Weld metal microstructure showed that while wire with 1.3% Al content contains coarse $\delta$-ferrite, wires with less than 0.5% Al content showed no such phase. In addition to the microstructural differences, cleanliness in weld metal was also different among wires. It showed that weld metal toughness was influenced by the $\delta$-ferrite formation, cleanliness and Ni addition. Even though wires with less than 0.5% Al content showed higher weld metal toughness, they showed relatively poor workability, forming porosities in weld bead in lower arc voltages.
오스테나이트계 스테인리스강 FCW 오버레이 용접 시 입열량에 따른 조직변화와 굽힘균열 특성
임희대 ( Hee Dae Im ),길웅 ( Woong Kil ),신기삼 ( Keesam Shin ),구본흔 ( Bon Heun Koo ) 대한금속재료학회(구 대한금속학회) 2013 대한금속·재료학회지 Vol.51 No.4
This study investigated the effect of heat input in overlay welding using stainless steel FCW on the dilution ratio and characteristics of microstructural evolution, initiation and propagation of a bending crack in the overlay weldment. When the heat input was varied in the range of 3.2-19.8 kJ/cm by adjusting welding parameters such as current, voltage and speed, the dilution ratio was the highest in 7.9- 9.9 kJ/cm with the lowest values of Creq and Nieq, for which the formation of martensite was predicted by the Schaeffler diagram, and its existence was confirmed by optical microscopy. In addition, the width of the transition zone was the largest in heat input of 7.9-9.9 kJ/ cm, and martensite was observed in the transition zone of the first weld layer of E309LT1-1 (welding material) and ASTM A516 Gr.70 (base metal). According to the bending test, cracks were observed in the specimens with heat input of 8.6-9.5 kJ/cm.