An electrofusion 45° elbow is a specialized pipe fitting used to connect two sections of high-density polyethylene (HDPE) or other plastic pipes at a 45-degree angle, allowing for a change in the direction of flow within a pipeline. It employs electrofusion welding, a process where an electric current heats embedded coils within the fitting to melt and fuse the pipe and fitting together, creating a strong, leak-proof joint.