Effect of repair weld length on microstructure evolution and mechanical properties of 30CrMnSiNi2A ultra-high strength steel

OM, SEM, EBSD and a series of mechanical property tests were used to study the influence of different welding lengths on the original welded joints. The results show that the filler welding area is austenitic structure due to the introduction of nickel base alloy. There are martensite and ferrite at the bottom of both the original weld and the repair weld. With the increase of the repair weld length, the number of martensite decreases gradually. Weld length has little effect on the grain growth direction at the bottom of the weld. The grain size at the bottom of the weld is affected by the thermal cycle of the weld and the nickel base filler metal, and the number of large Angle grain boundaries with dislocation hin-dering effect decreases. In addition, the reason for microstructure change is explained by a mathematical model. The tensile strength and microhardness decreased continuously after the repair welding, and the impact toughness increased significantly due to the in-crease of the austenite structure.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).