Modern production of bimetallic materials widely uses, among others, such a method for their production as explosive welding. It is used especially effectively to create layered composites from dissimilar metals, when traditional methods of welding (joining) do not work due to the large difference both in thermal and mechanical properties. In some modern industries, bimetallic joints of steel sheets and aluminum sheets with a greater thickness than for cladding are required. However, with an increase in the thickness of the flayer (aluminum) plate, the kinetic energy of separation also increases, which leads to the formation of microcracks, and, consequently, to a decrease in the strength of the joint. Experimental studies of a series of steel - aluminum bimetallic composites obtained by explosive welding at various values of the thickness of the flayer (aluminum) plate, schemes and welding parameters have been carried out. The limited influence of such energy criteria of welding success as the value of kinetic energy losses, as well as the energy of plastic deformation on the fundamental possibility of obtaining a high-quality welded joint steel - thick aluminum plate is found. Based on the analysis of standard criteria for weldability, microstructure and phase composition of the contact area, as well as the mechanical properties of the obtained welded joints, an assumption was made about the critical role of the pressure of residual detonation products. The practical possibility of obtaining by explosive welding a composite material thick sheet aluminum - steel with a bonding strength for separation of the cladding layer of more than 100 MPa is shown.