<p>The evolution and distribution of cryogenic toughness were investigated within the multi-pass welding heat affected zone (HAZ) of a high Mn austenitic steel. The results reveal that thermal cycles exceeding 1000 °C induce enhancements in cryogenic toughness due to grain growth. Unusually, the evolution of cryogenic toughness is governed by M₂₃C₆ carbide variation within regions below 1000 °C, which act to reduce the cryogenic toughness. The peak temperature (Tp) of final thermal cycle is a key determinant of cryogenic toughness, as it determines whether the M₂₃C₆ carbide precipitate or remelt. The regions exhibiting poor cryogenic toughness spatially overlap with intergranular corrosion grain boundaries (ICGB) zone, because M₂₃C₆ carbide also reduce intergranular corrosion resistance. ICGB zone is cross-ringed in HAZ, and its size and position is governed by welding heat input and bead layout. This study provides valuable insights into controlling and testing performance of welded joint.</p> Graphical Abstract <p></p>