<p>The types, distribution, trends, and scale of internal defects often reflect whether the welding process parameters are reasonable and indicate directions for optimization, and the analysis of these can help to provide a scientific basis and guidance for the gaps generated by various welding process parameters. To provide more necessary data and perspectives, this paper proposes a method for analyzing the size of internal welding defects using segmentation algorithms combined with phased array ultrasonic technology. The design of the segmentation algorithm for welding phased array images follows the idea of simplifying scenarios by downplaying deeper conceptual understanding. The proposed method also introduces the equilibrium value (EV) to represent the balance between over-segmentation and under-segmentation. In order to verify whether the complete method can achieve the expected results, the paper demonstrates the plausibility of the existence of EV and which shows the relationship with the metric’s ability to balance positive and negative deviations. And multiple comparative experiments are conducted to illustrate the feasibility and advantages of the proposed model, OCRNet-CPD, from various aspects, which achieve the simplification of the whole system and potentially reduce the computational complexity while ensuring its segmentation accuracy. Finally, the proposed method was used to establish a relative size chart for specific weldments, offering the possibility of addressing issues in welding processes from both numerical and image perspectives.</p>