Nanomodification is an effective way of forming a fine-grained structure of a weld metal. Part I. Factors determining the stability of the weld seam against embrittlement

Steel constructions are the most important objects of the construction industry. The main method of connecting individual elements and assemblies of such structures is fusion welding (electric arc, plasma, electron beam). One of the main problems of metal structures is their tendency to brittle fractures that occur suddenly, without noticeable previous deformations, often at below zero temperatures and loads. In this case, 70-80% of such damage is associated with welding. The nature of the destruction depends not only on temperature, but also on the type of crystal lattice. Metals with a body-centered cubic (bcc) lattice (tungsten, molybdenum, α-iron) are plastic at a relatively high temperature, but become brittle when negative. And metals with a face-centered cubic (fcc) lattice (aluminum, nickel, copper and γ-iron) are plastic even at temperatures close to absolute zero. With decreasing temperature, the mobility of dislocations and vacancies decreases, the yield strength os increases, that is, the ductility of the metal decreases...