Application of Surface Cracking Process to Improve Impact Toughness of High Mn Steel Using Surface Cracking Process

抄録

Cryogenic applications require careful material selection due to severe property degradation at low temperatures. Face-centered cubic (FCC) alloys like high-manganese steel offer good low-temperature toughness but become brittle at cryogenic temperatures. This brittleness increases safety risks due to sudden, unpredictable fractures. Therefore, novel technologies are urgently needed to improve the mechanical properties of FCC alloys for cryogenic applications. This research presents a new surface-cracking process for high-manganese steels to address the degradation of mechanical properties at cryogenic temperatures. This technique involves the intentional introduction of surface micro-cracks, which significantly enhances the Charpy impact toughness of the steel at low temperatures. To observe the effect of surface cracks, specimens with varying crack densities were fabricated: 5 lines (5L) and 10 lines (10L). These were compared with a standard specimen without surface cracks (0L). Microstructural observations reveal that the dispersion of crack propagation energy by the surface micro-cracks improves Charpy impact toughness, promoting a ductile fracture mode even under cryogenic conditions.

Fig. 5 The fracture surface of high-Mn steels with a surface-cracking process, showing the area around the notch and the center of the impact-fractured specimen at 20°C, −100°C, and −196°C. (online color)