# Investigation of Impact Behavior of STS304L Steel Plate Under Cryogenic Temperature
## 4 Conclusions  
This study investigated the temperature sensitivity of the mechanical behavior of STS304L under impact loading using drop-weight impact tests. As a metastable austenitic stainless steel, STS304L exhibits a negative temperature sensitivity in terms of its stiffness and impact energy absorption capacity. To determine the cause of this phenomenon, deformation measurements and martensite fraction analysis were conducted. The key findings are summarized as follows. 1. The stiffness of STS304L increased with a decreasing temperature, rising by 59.63% at \(-\)100 \({}^{\circ}\)C and 68.80% at \(-\)193 \({}^{\circ}\)C compared with that at 20 \({}^{\circ}\)C. The impact energy absorption capacity also increased, reaching 109 J at 20 \({}^{\circ}\)C, 174 J at \(-\)100 \({}^{\circ}\)C, and 184 J at \(-\)193 \({}^{\circ}\)C. The impact energy was stored in STS304L in the form of elastic deformation, plastic deformation, heat dissipation, and phase transformation (austenite to martensite). 2. The deformation mechanism did not exhibit temperature sensitivity under hemispherical impact conditions. The measured plastic deformations were 10.89 mm at 20 \({}^{\circ}\)C, 11.02 mm at \(-\)100 \({}^{\circ}\)C, and 11.12 mm at \(-\)193 \({}^{\circ}\)C, showing no significant variation. However, the negative temperature sensitivity of the stiffness indicated an increase in stored energy within STS304L. 3. Strain-induced martensitic transformation increased as the temperature decreased, as shown in the EBSD analysis. The martensite fraction increased progressively from Region 1 to Region 4, confirming that strain-induced martensitic transformation contributed to the negative temperature sensitivity of STS304L by increasing the stored energy in the form of phase transformation. * Adiabatic heating due to high strain rates was the primary cause of reduced energy absorption at 20 \({}^{\circ}\)C. Localized temperature increases suppressed strain-induced martensitic transformation, leading to premature cracking owing to softening effects. * The negative temperature sensitivity in stiffness and strain-induced martensitic transformation caused distinct differences in the mechanical behavior of STS304L between cryogenic and 20 \({}^{\circ}\)C conditions. Notably, adiabatic heating at 20 \({}^{\circ}\)C resulted in significantly altered mechanical behavior compared with that at cryogenic conditions. This study provides insights into the relationship between temperature and mechanical behavior under large plastic deformation induced by a hemispherical impactor. However, the hemispherical impactor does not fully replicate the sloshing impacts experienced in actual applications. Therefore, further evaluation of impact resistance using various impactor shapes is necessary to accurately simulate sloshing and assess temperature sensitivity in real-world environments. Conceptualization, [PERSON]-M.K. and [PERSON]-T.K. ; methodology, [PERSON]-M.K. and [PERSON]-K.H. ; validation, [PERSON]-M.K. and [PERSON]-T.K. ; formal analysis, [PERSON]-M.K. and D.-H.L. ; investigation, [PERSON]-M.K. and D.-H.L. ; resources, [PERSON]-H.K. and J.-M.L. ; data curation, [PERSON]-M.K., [PERSON]-K.H. and D.-H.L. ; writing--original draft preparation, [PERSON]-M.K. and [PERSON]-K.H. ; writing--review and editing, [PERSON]-H.K. and [PERSON]-M.L. ; visualization, [PERSON]-M.K., [PERSON]-K.H. and [PERSON]-T.K. ; supervision, J.-M.L. ; project administration, J.-H.K. ; funding acquisition, J.-M.L. All authors have read and agreed to the published version of the manuscript. This work was supported by the Technology Innovation Program (RS-2024-00437088) funded by the Ministry of Trade, Industry & Energy(MOTIE, Korea). This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Ministry of Trade, Industry & Energy (MOTIE) of the Republic of Korea (2022400000090). Not applicable. The original contributions presented in this study are included in the article, further inquiries can be directed to the corresponding author.