TiN Precipitation Behavior and Its Influence on Grain Growth in High‐Strength Micro‐Alloyed Steels With Various Ti and N Concentrations

The influence of Ti and N concentrations on the precipitation behavior of TiN particles and the subsequent austenite grain growth was investigated in this study. Two steels with a similar Ti/N ratio but different Ti and N levels were designed. The precipitation behavior of TiN particles was characterized using scanning electron microscopy and transmission electron microscopy combined with carbon replica extraction techniques. The results show that micron‐scale TiN particles are predominantly formed in the steel with higher Ti and N contents due to liquid‐phase precipitation during solidification. In contrast, nanoscale TiN particles are observed in both steels, but their volume fraction does not increase proportionally with higher Ti and N additions. Grain growth experiments reveal that simply increasing Ti and N concentrations does not proportionally enhance the pinning effect. For a given Ti content, an excessive N element is the primary reason for the formation of micron‐scale TiN particles. Therefore, controlling N content based on the actual Ti level to achieve an appropriate Ti/N ratio is an effective strategy to avoid the formation of coarse TiN particles, maximize the utilization of Ti, and promote nanoscale TiN precipitation for austenite grain refinement at high temperatures.