• Title/Summary/Keyword: FCAW-S

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Low Heat Input Welding to Improve Impact Toughness of Multipass FCAW-S Weld Metal

  • Bang, Kook-soo;Park, Chan;Jeong, Ho-shin
    • Journal of Ocean Engineering and Technology
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    • v.28 no.6
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    • pp.540-545
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    • 2014
  • Multipass self-shielded flux cored arc welding with different heat inputs (1.3–2.0 kJ/mm) was conducted to determine the effects of the heat input on the proportion of the reheated region, impact toughness, and diffusible hydrogen content in the weld metal. The reheated region showed twice the impact toughness of the as-deposited region because of its fine grained ferritic-pearlitic microstructure. With decreasing heat input, the proportion of the reheated region in the weld metal became higher, even if the depth of the region became shallower. Accordingly, the greatest impact toughness, 69 J at −40℃, was obtained for the lowest heat input welding, 1.3 kJ/mm. Irrespective of the heat input, little difference was observed in the hardness and diffusible hydrogen content in the weld metal. This result implies that low heat input welding with 1.3 kJ/mm can be performed to obtain a higher proportion of reheated region and thus greater impact toughness for the weld metal without the concern of hydrogen cracking.

Effects of Welding Parameters on Diffusible Hydrogen Contents in FCAW-S Weld Metal (셀프실드아크 용접금속의 확산성수소량에 미치는 용접변수의 영향)

  • Bang, Kook-Soo;Park, Chan
    • Journal of Ocean Engineering and Technology
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    • v.27 no.5
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    • pp.77-81
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    • 2013
  • The effects of the welding parameters, contact tip-to-workpiece distance (CTWD), current, and voltage on the diffusible hydrogen content in weld metal deposited by self-shielded flux cored arc welding were investigated and rationalized by comparing the amount of heat generated in the extension length of the wire. This showed that as CTWD increased from 15mm to 25mm, the amount of heat generated was increased from 71.1J to 174.8J, and the hydrogen content was decreased from 11.3mL/100g to 5.9mL/100 g. Even if little difference was observed in the amount of heat generated, the hydrogen content was increased with an increase in voltage because of the longer arc length. A regression analysis showed that the regression coefficient of voltage in self-shielded flux cored arc welding is greater than that in $CO_2$ arc welding. This implies that voltage control is more important in self-shielded flux cored arc welding than in $CO_2$ arc welding.