Abstract: The three-roll skew rolling process is an excellent method for fabricating bimetallic composite pipes, offering advantages such as low energy consumption and high interfacial bonding strength after rolling. Prior to rolling, the ends of the pipe billets must be seal-welded to prevent oxidation of the mating metal surfaces and to ensure interfacial bonding performance. Experimental results indicate that the quality of end-sealing welds significantly affects the bonding strength and yield rate of the rolled composite pipes. Based on this observation, this study integrates mechanical performance testing and microstructural characterization to investigate the effects of different welding qualities on deformation compatibility during rolling, interfacial bonding performance after rolling, and the metallurgical bonding length. The results show that pipe billets with high-quality welds can effectively coordinate the deformation of the inner and outer metallic components during the composite rolling process, while also preventing oxidation of the mating metal surfaces. Consequently, a uniformly distributed, high-strength metallurgical bond is formed at the carbon steel/stainless steel interface in the rolled composite pipes. These findings highlight that superior end-sealing weld quality is crucial for the efficient fabrication of bimetallic composite pipes.