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Vol.59, No.12, 893 ~ 904, 2021
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| Title |
| The Effect of Preheating Current on the Melting Behavior of Bolt Projection Welding of Al-Si Coated Hot-Stamped Boron Steel |
| 김재훈 Jae-hun Kim , 전현욱 Hyun-uk Jun , 천주용 Joo-yong Cheon , 김재원 Jae-won Kim , 김재득 Jae-deuk Kim , 지창욱 Changwook Ji |
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| Abstract |
| This study evaluated the effect of preheating on early stage melting behavior of a Al-Si coated hot stamped boron steel bolt during projection welding. A large amount of heat was generated in the early stage of projection welding. Because of the large heat generation, a rapid collapse of the projection occurred and a molten coating layer remained on the interface of the welded part. This caused welding defects such as expulsion and porosity. However, preheating helped remove the molten Al-Si coating layer by pushing it out toward the outer edge of the molten pool. This suggests that preheating can effectively minimize or remove the molten coating layer within the weld. Preheating also prevented the rapid collapse of the projection by partially melting the projection, and thus improving the contact area. These phenomena can prevent the concentration of current density at the weld interface and hence decrease heat generation. Finally, the preheating current improved nugget quality by promoting the stable growth of the melted metal and by preventing expulsion and porosity.
(Received July 23 2021; Accepted August 25, 2021) |
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| Key Words |
| bolt projection welding, preheating current, Al-Si coated hot-stamping steel, initial melting behavior, SORPAS simulation |
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