This work investigated the effects of Mo (0.3 wt%, 0.1 wt%) and Mn contentsMn content (0.9 wt%, 1.24 wt%) on the prior austenite grain sizesGrain size of the oil drill pipe jointOil drill pipe joint steelsSteel at different austenitizing temperaturesTemperature (840–1010 °C) and varying austenitizing times (1, 2, and 3 h). Optical microscopy was used to statistically evaluate the prior austenite grain sizesGrain size under different heat treatmentHeat treatment conditions. The results indicate that grain sizeGrain size increases significantly with higher austenitizing temperatureTemperature and prolonged holding time. When the Mo content was reduced from 0.3 to 0.1 wt%, the grain sizeGrain size increased under identical thermal conditions. Conversely, increasing the Mn contentMn content from 0.9 to 1.24 wt% resulted in a slight reductionReduction in grain sizeGrain size under the same conditions. A Sellars model fits the relationship among austenitizing temperatureTemperature, holding time, and grain growth kineticsKinetic. The grain growth kineticsKinetic model for steelSteel sample 3# (0.1 wt% Mo, 1.24 wt% Mn) was determined as follows: \(D_{3} = 16424.25t^{0.29} \exp \left( { - \frac{77516.92}{{RT}}} \right)\) .