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Vol.49, No.1, 64 ~ 73, 2011
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| Title |
| Assessment of Resistance Spot Weldability of Dissimilar Joints of Austenitic Stainless Steels/IF Steels and Ferritic Stainless Steels/IF Steels |
| 이진범 Jin Beom Lee , 김동철 Dong Cheol Kim , 남대근 Dae Geun Nam , 강남현 Nam Hyun Kang , 김순국 Soon Kook Kim , 유지훈 Ji Hun Yu , 임영목 Young Mok Rhym , 박영도 Yeong Do Park |
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| Abstract |
| The spot weldability of dissimilar metal joints between austenitic stainless steels (STS316)/IF steels and ferritic stainless steels (STS430)/IF steels was investigated. This study was aimed to determine the spot welding parameters for a dissimilar metal joint and to evaluate the dissimilar metal joint`s weldability, including its welding nugget shape, tensile-shear strength, hardness, and microstructure. The comparison of these results was described in terms of fracture behavior. Compared with the weld lobe of similar metal joints, dissimilar metal joints (STS430/IF) had reduced weld current range. However, the weld lobe of STS316/IF steel joint showed increased weld current range. This is because the dilution of chemical composition in the molten weld pool suppressed the heat input being caused by Joule heat with current flow through the samples. The microstructure of the fusion zone was fully martensite and mixture of ferrite and martensite for austenitic stainless steel/IF steel and ferritic stainless steel/IF steel combination, respectively. The experimental results showed that the shape of nugget was asymmetric, in which the fusion zone of the austenitic and ferritic stainless steel sheet was larger due to the higher bulk-resistance. The predicted microstructure by using the Schaeffler diagram was well matched with experimental results. After peel test, the fracture was initiated from heat affected zone of ferritic stainless steel sheet side, however the final fracture was propagated into the IF steel sheet side due to its lower strength. |
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| Key Words |
| alloys, joining, fracture, tensile test, dissimilar joints |
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