A flexible ferromagnetic strip is used to induction-weld seams in polymer pipes. The strip is a blend of strontium ferrite, a surfactant, and an LDPE binder. A process to produce the profile is to mix the ingredients together followed by granulation and extrusion or calendering. The strip is used in conjunction with an induction coil sized to fit over a polymer pipe coupling containing the strip and separate segments of polymer pipe. The strip is heated by induction current induced by an electromagnetic field generated by the coil. The heated strip causes the polymer pipe segments to be thermoplastically welded together.