PHYSICO-MECHANICAL PROPERTIES OF WELDED JOINTS OF HIGH-STRENGTH STEEL WITH THE YIELD STRENGTH OF 690...1300 MPa

摘要

The work is devoted to establishing regularities of influence of features of structural-phase composition (grain, subgrain, dislocation structures, etc.) of metal of welded joints of high-strength steels of different strength class on their mechanical characteristics and crack resistance by determining structural criteria providing the necessary set of these properties. The structure and properties of welded joints of high-strength steels with the yield strength from 690 to 1300 MPa was investigated depending on the rates of cooling and welding, alloying welds, heat treatment conditions and welding methods (mechanized arc, laser, hybrid laser-arc welding): bainite-ferrite and bainite-martensite type; high-carbon ferrite-pearlite type; alloyed medium-carbon steels of martensiticbainite type of special purpose. The relationship of structural parameters with such set of properties as strength, fracture toughness, level of localized deformation and local inner stresses in the metal of welded joints was established. It was shown that in compliance with certain ratios of structural-phase components, the characteristics of dislocation and subgrain structure are decisive for providing strength and crack resistance of welded joints metal of high-strength steels. The indices of the level of localized deformation in the metal of welded joints of high-strength steels were obtained and it was established how structural components affect crack resistance of the metal. In order to provide the operational reliability of structures in the creation of science-intensive and promising technologies for welding of high-strength steels on the basis of material experimental and theoretical studies, structural criteria were established to provide the required set of mechanical properties and crack resistance of the mentioned joints.