Control of Precipitation Kinetics of High-Niobium and Nitrogen-Nickel-Based Alloy During Continuous Casting

A nickel-based alloy, enriched with niobium and nitrogen, has been developed for core equipment in polysilicon production within the photovoltaic industry. However, it exhibits strong susceptibility to cracking driven by precipitates during continuous casting production. Thermal simulation of the actual cooling process of the continuous casting slab was carried out using high-temperature confocal method, and the transformation kinetic behavior of different precipitated phases was obtained. Our experimental results reveal two precipitation phases in high niobium and nitrogen nickel-based alloys: NbN and Cr₂₃C₆, with the starting precipitation temperature ranges being between 1092 °C to 889 °C and 989 °C to 892 °C, respectively. Furthermore, the kinetic behavior of the precipitated phase was integrated into the heat transfer solidification model of the continuous casting slab, and the developed framework was used to analyze the solid-state phase transformation law of the particles in the secondary cooling zone under different processes. The results show that reducing the casting speed and casting temperature as well as increasing the secondary cooling water ratio will reduce the phase transformation rate and transformation amount of the continuous casting slab. Based on this research, a new cooling scheme for continuous casting production of high niobium and nitrogen nickel-based alloys was developed to inhibit the kinetic behavior of NbN and Cr₂₃C₆ precipitation directly from the γ phase and improve the hot plasticity of the slab.