The work is concerned with the study of the process of joint formation during pressure welding by pulse current through a layer of hydrocarbon substance. During the development of this welding method, there was no necessary amount of scientific knowledge about concomitant physicochemical processes. Interdisciplinary experimental studies performed by different authors have allowed establishing scientific facts necessary for the formation of a hypothesis about the mechanism of formation of a welded joint. Carbon nanoformations are found and their properties are studied. The phenomena accompanying the passage of pulse electric current through them are studied. The phenomena of anomalous mass transfer under the action of shock loading during diffusion welding of dissimilar materials are studied. It is experimentally proved that electroexplosive and electromagnetic phenomena as well as shock waves activate diffusion processes, when applied to the surface layers of metal. The hypothesis assumes that, when a pulsed electric current of constant polarity is passed, an electrical explosion of contacting metallic microblasts occurs. The formation and subsequent microexplosions of conductive carbon particles occur. Microexplosions and shock waves activate diffusion processes on the surfaces to be joined. The process is completed after the ‘Coulomb explosion’ and the release of pyrolysis products from the central part of the joint of the welded surfaces. It is experimentally proved that the formation of the joint occurs at temperatures below the melting point of the materials to be welded. The time of joint formation at the same temperature is much shorter than during diffusion welding in vacuum. The structure of the welded joint is similar to the structure obtained by diffusion welding in vacuum. The methodology is developed, and experimental studies are carried out. The obtained results confirm the put forward hypothesis and correspond to the previously performed interdisciplinary studies of specialists.