The alloying of aluminum, boron, and titanium significantly influences the microstructure and the mechanical properties of microalloyed steel. Al is used as a deoxidizer in the steel production process, and aluminum nitride (AlN) plays a crucial role in grain size control due to its strong pinning effect [1]. Boron, as segregated at grain boundaries rather than precipitated as boron nitride (BN), acts as an economically very interesting hardenability promoter [2]. Titanium further protects boron from forming BN and facilitates the nucleation of acicular ferrite, enhancing the steel toughness [3]. These elements exhibit a complex interplay, competing for nitrogen, with titanium showing the highest affinity, followed by boron and aluminum [4]. This competition affects the formation and distribution of nitrides, which in turn impacts the microstructural steel characteristics. The influence of precipitates such as AlN, BN, and TiN on grain growth kinetics in austenite is governed by Zener drag [5], which impedes the movement of grain boundaries. Among these, AlN exhibits the most significant effect in retarding grain growth [1], while fine TiN particles also notably contribute [3]. Moreover, the presence of Ti and B modulates the availability of nitrogen for Al. Thus, especially for B-alloying, it has been reported to significantly increase the austenite grain size [2]. This study investigates the grain growth behavior in high-purity vacuum induction melted alloys with varying fractions of Al, B, and Ti. The resulting microstructures are characterized metallographically by employing light optical microscopy (LOM), scanning electron microscopy (SEM), and electron-backscatter diffraction (EBSD). By using the present experimental results, we simulate the grain size evolution using a mean-field approach, as implemented in the software package MatCalc [6] and the Calphad-type open-licensed MatCalc database mc_fe_v2.060.tdb. References 1. Wilson FG, Gladman T (1988) Aluminium Nitride in Steel. International Materials Reviews 33(1): 221–286. doi: 10.1179/imr.1988.33.1.221 2. Sharma M, Ortlepp I, Bleck W (2019) Boron in Heat‐Treatable Steels: A Review. steel research international 90(11): 1900133. doi: 10.1002/srin.201900133 3. Baker TN Titanium Microalloyed Steels. 0301-9233 46(1): 1–55. doi: 10.1080/03019233.2018.1446496 4. Wang WS, Zhu HY, Sun J et al. (2019) Thermodynamic analysis of BN, AlN AND TiN Precipitation in boron-bearing steel. Metalurgija 58(3-4): 199–202 5. Manohar PA, Ferry M, Chandra T (1998) Five Decades of the Zener Equation. ISIJ Int. 38(9): 913–924. doi: 10.2355/isijinternational.38.913 6. Kozeschnik E (2022) Mean-Field Microstructure Kinetics Modeling(In: Francisca G. Caballero (ed.), Encyclopedia of Materials: Metals and Alloys. vol. 4,): 521–526. doi: 10.1016/b978-0-12-819726-4.00055-7