| A Study on Characteristics of Dissimilar Welds between Super Duplex Stainless Steel UNS S32750 and Carbon Steel A516-70 with FCAW |
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In-June Moon*, Bok-Su Jang*, Se-Cheol Kim*, Jin-Hyun Koh* |
Correspondence:
Jin-Hyun Koh,
Email: jhkoh@koreatech.ac.kr
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| Abstract |
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The metallurgical and mechanical characteristics, toughness and corrosion resistance of dissimilar welds between super duplex stainless steel UNS S32750 and carbon steel ASTM A516Gr.70 have been evaluated. Three heat inputs of 21.12, 24.00, 26.88kJ/cm were employed to make joints of dissimilar metals with flux cored arc welding(FCAW). Based on microstructural examination, vermicular ferrite was formed in the first layer of weld at low heat input(21.12kJ/cm) and Creq/Nieq of 1.61 while acicular ferrite was formed in last layer of weld at high heat input(26.88kJ/cm) and Creq/Nieq of 1.72. Ferrite percentage in dissimilar welds was lowest in the first layer of weld regardless of heat inputs and it gradually increased in the second and third layers of weld. Heat affected zone showed higher hardness than the weld metal although reheated zone showed lower hardness than weld metal due to the formation of secondary austenite. Tensile strengths of dissimilar welds increased with heat input and there was 100MPa difference. The corrosion test by ferric chloride solution showed that carbon steel had poor corrosion resistance and pitting corrosion occurred in the first layer(root pass) of weld due to the presence of reheated zone where secondary austenite was formed. The salt spray test of carbon steel showed that the surface only corroded but the amount of weight loss was extremely low. |
| Key Words:
Super duplex stainless steel, FCA multipass, pitting corrosion, Secondary austenite, Dissimilar weld |
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