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Vol.57, No.12, 778 ~ 787, 2019
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| Title |
| Effect of Hot Stamping Heat Treatment Temperature on Resistance Spot Weldability of Al-10% Si Coated 30MnB5 Steel |
| 손성국 Seong Guk Son , 황연정 Yeonjung Hwang , 이창욱 Chang Wook Lee , 유지홍 Ji Hong Yoo , 최민수 Minsu Choi |
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| Abstract |
| Hot stamping is the most efficient manufacturing process to produce high strength automotive parts with reduced springback. Recently, 30MnB5 steel has been developed for hot stamping steel which can provide above 1700 MPa. However, resistance spot weldability of this steel is insufficient due to the need for a large amount of carbon addition. In this study, the effect of the hot stamping heat treatment temperature on resistance spot weldability of Al-10% Si coated 30MnB5 was evaluated to improve the resistance spot weldability of 30MnB5. In terms of nugget diameter, weldable current range, tensile shear strength and cross tension strength, the specimen heat treated at 850 ℃ achieved better performance than the specimen heat treated at 950 ℃. There was a coating microstructure difference between the specimens heat treated at 850 ℃ and 950 ℃ whereas both specimens had similar microstructure and mechanical properties of their substrates. The Fe-rich layer of the specimen heat treated at 950 ℃ was twice as thick as the specimen heat treated at 850 ℃ because the diffusion rate was much higher at 950 ℃. The thick Fe-rich layer deteriorated the resistance spot weldability due to high electrical resistivity during resistance spot welding.
(Received August 22, 2019; Accepted October 6, 2019) |
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| Key Words |
| hot stamping, Al-10%Si coating, 30MnB5, resistance spot welding, dynamic resistance |
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