Modification the weld metal structure of hsla steels by refractory nanoparticles

Purpose. The aim of study was to investigate the impact of nano-dispersed particles of refractory metals in the molten metal of the weld pool and the crystallization kinetics of austenite in the metal joints of high-strength low-alloy steels. The results of studies of the metal structure of high-strength low-alloy steel joints 14HGNDTS, which were introduced into the melt. Nanopowder particles of various refractory compounds - oxides, nitrides and carbides (TiC, TiN, SiC, VC, NbC, TiO2, Al2O3, MgO, ZrO2). The studies showed the effectiveness of nanooxides TiO2 titanium and zirconium ZrO2, thus ensuring high values of the mechanical properties of the weld metal (Rm -708 MPa and 621MPa, KCV-20 - 60 J / cm2 and 72.9 J / cm 2, δ - 21 and 19%), due to the formation of the complex and needle bainitic structures. Using Gleeble 3800 installation simulating thermal cycles it possible to establish the relationship between the temperature conversion interval, the number of structural components and the type of modifying nanoparticles. Originality. Modification of metal nanoparticles seams titanium and zirconium oxide ZrO2 TiO2 leads to the development of transformation at high temperatures to form bainite acicular ferrite, which complex has a favorable strength, plastic and viscous properties. Carbides TiC, SiC and nitrides of TiN, NbN lowering the bainite start temperature lead to the formation of bainitic-martensitic structures (lower bainite, microphase MAK-phase), which have reduced viscous and plastic properties. Compounds of VN, VC and ZrC are readily soluble in the molten metal of the weld pool and therefore, they are of little use as effective metal structure modifiers seams. Practical value. The results will be used to enhance the performance properties of HSLA steel welded joints.