An application of high-strength steels in industry is associated with their improved technical and economic indicators, namely: improved performance characteristics with a simultaneous reduction in the mass of the product, higher strength and plastic properties compared to conventional structural steels. However, the weldability of high-strength steels is limited due to defects in welded joints and a decrease in their strength relative to the base metal. Applying to high-strength steels a technology of a pulsed flux cored arc welding with an additional hot wire has been developed. Flux-cored wire 50ACr20TiAl was used as a welding wire and a hot filler, which makes it possible to obtain a structure of metastable austenite in a welded joint. This technology was used to weld high-strength steel of the 45Cr2NiMoVNbA type of 6.3 mm thickness. An analysis of the structure and changes in the hardness of the welded joint was carried out. It is shown that the use of this technology makes it possible to obtain defect-free welded joints, which are characterized by strength indicators comparable to the base metal. At the same time, they are capable to self-hardening under the action of an extreme mechanical load. The microhardness of the weld is HV0.1 400…450. After intense dynamic impact, load 1500 MPa, its microhardness increases to HV0.1 700…750. On the basis of previous studies of the authors, it was concluded that with the welding technology used, metastable austenite is formed in the seam. With subsequent intense external dynamic action, the weld metal is strengthened due to the formation of deformation martensite.