Abstract Abstract Most of automotive components are bonded by resistance spot welding of thin Zn-coated advanced Most of automotive components are bonded by resistance spot welding of thin Zn-coated advanced high strength steel (AHSS) sheets. During the spot welding process Zn coating layer is molten by the high strength steel (AHSS) sheets. During the spot welding process Zn coating layer is molten by the heat generation, and often infiltrates into grain boundaries, causing intergranular cracking, known as heat generation, and often infiltrates into grain boundaries, causing intergranular cracking, known as liquid metal embrittlement (LME). Thus, the LME is a critical hurdle to apply the Zn-coated AHSS in liquid metal embrittlement (LME). Thus, the LME is a critical hurdle to apply the Zn-coated AHSS in automotive industries. Although there are many factors which affect LME, the effects of material automotive industries. Although there are many factors which affect LME, the effects of material factors such as alloying element (Si), and microstructural components will be introduced in this factors such as alloying element (Si), and microstructural components will be introduced in this presentation. Among many elements in the steel sheets, Si is the most harmful one on LME. We found presentation. Among many elements in the steel sheets, Si is the most harmful one on LME. We found that Si in the steel delayed the dissolution of Fe into the coating from the steel, which suspended the that Si in the steel delayed the dissolution of Fe into the coating from the steel, which suspended the active reaction of Fe-Zn and cannot prevent the steel from contacting the liquid Zn during welding. As active reaction of Fe-Zn and cannot prevent the steel from contacting the liquid Zn during welding. As a second factor, the importance of austenite fraction during spot welding is introduced and we suggest a second factor, the importance of austenite fraction during spot welding is introduced and we suggest WIP) steel, based on our a novel method to prevent LME of Zn-coated twining induced plasticity (Ta novel method to prevent LME of Zn-coated twining induced plasticity (TWIP) steel, based on our findings. findings. Photo Photo Understanding Understanding Graduate Institute of Ferrous and Eco materials Technology (GIFT), Graduate Institute of Ferrous and Eco materials Technology (GIFT), Pohang University of Science and Technology (POSTECH), Korea Pohang University of Science and Technology (POSTECH), Korea Prof. Sung-Joon Kim is currently Dean of Graduate Institute of Ferrous and Energy Materials Technology (GIFT), POSTECH, Korea. He graduated from University of Illinois at Urbana-Champaign and received Prof. Sung-Joon Kim is currently Dean of Graduate Institute of Ferrous and Energy Materials Technology Ph.D in 1990. Before joining POSTCEH in 2011, he had been working in the Korea Institute of Materials (GIFT), POSTECH, Korea. He graduated from University of Illinois at Urbana-Champaign and received Science (KIMS) in Changwon, Korea for more than 20 years as a principal researcher leading research and Ph.D in 1990. Before joining POSTCEH in 2011, he had been working in the Korea Institute of Materials development of various kinds of steels, and later served as the vice president of the KIMS. for 3 years. He Science (KIMS) in Changwon, Korea for more than 20 years as a principal researcher leading research and also served as the president of Korean Institute of Metals and Materials in 2019, and currently he is a development of various kinds of steels, and later served as the vice president of the KIMS. for 3 years. He member of the National Academy of Engineering of Korea. He is the author of more than 280 peer-also served as the president of Korean Institute of Metals and Materials in 2019, and currently he is a reviewed publications. His major interest areas are alloy design of stainless steels, LME and hydrogen member of the National Academy of Engineering of Korea. He is the author of more than 280 peer-embrittlement, etc. reviewed publications. His major interest areas are alloy design of stainless steels, LME and hydrogen embrittlement, etc. NIMS Award Symposium 2023Material Factors on Liquid Material Factors on Liquid Sensitivity of Zn-coated AHSS Sensitivity of Zn-coated AHSS NIMS Award SessionSung-Joon Kim Sung-Joon Kim Metal Embrittlement Metal Embrittlement Invited Talk NA-4 Invited Talk NA-4 19
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