The Use of Nanopowders of Refractory Compounds in Welding

We present investigation of the inoculation of nano-sized powders of refractory oxides $\mathrm{Al}_{2} \mathrm{O}_{3}, \mathrm{TiO}_{2}, \mathbf{M g O}$, ZrO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> into the welding pool. We show that oxides’ inoculation with a low level of mismatch to the $\delta$-Fe lattice and increased wetting with liquid iron ($\mathrm{MgO}, \mathrm{ZrO}_{2}$) into the weld pool contributes to the dendrites growth, which are formed during melt crystallization. Metal modification with $\mathbf{M g O}, \mathbf{Z r O}_{2}$ oxides contributes to decrease of the polygonal ferrite hardness and increase in the lower bainite content in the microstructure. This leads to overall increase of metal resistance against brittle fracture. Metal modification with Al<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> and TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> contributes to increase of polygonal ferrite hardness and the upper bainite content in the microstructure, resulting in improvement of strength indicators of low-alloy steel welds.