Influence of aluminum and titanium on the structure and properties of type 3Cr3Mo3 steel
DOI:
https://doi.org/10.15407/mom2025.03.058Keywords:
steel, titanium, aluminum, carbides, oxides, fracture, structure, mechanical propertiesAbstract
The influence of aluminum and titanium on steel type 3Cr3Mo3, which was melted in laboratory conditions using chamber electroslag remelting (ESR) of the electrode obtained by vacuum induction remelting, was investigated.
It was found that aluminum in the structure of the steel combines with oxygen and forms Al2O3 oxides. Cartographic studies of the concentration of aluminum and oxygen in the fracture area showed the presence of these oxides..
Due to the small amount of oxygen in the steel and its uniform distribution mainly along the high- and low-angle boundaries of primary and secondary grains, aluminum oxides are located precisely along the grain boundaries and have small sizes, up to 1-2 microns. But taking into account the amount of aluminum (0.6 wt.%), these inclusions have a significant negative impact on the energy intensity of fracture.
The work revealed that the presence of titanium in the structure of 3Сr3Mo3 steels does not contribute to the formation of compounds with harmful impurities (sulfur and phosphorus), which must be removed from the metal into the slag during the refining process. Titanium is part of large (about 4 microns), complex carbides, which are formed from the supersaturated melt of strong carbide-forming elements and carbon pressed out during the peritectic transformation process. Titanium is not a mystic in the matrix, but only reacts with carbon, oxygen and nitrogen. It acts as an unnecessary ballast in the formation of primary complex carbides from a liquid of eutectic composition. Its function is only to increase their size due to its relatively low density.
Due to the small number of modifiers in the composition of the steel under study, the volume percentage of large (up to 4 μm in size) complex carbides additionally containing titanium is not high (no more than 0.25%), but the presence of these large carbides on the facets of the quasi-cleavage proves that the fracture begins precisely with these stress concentrators.
Thus, the distribution features of aluminum compounds negatively affect interfacial adhesion and increase stress concentrations during steel fracture and, as a result, reduce fracture energy. The negative effect of titanium on the structure of 3X3M3 steel is due to the contribution of this chemical element to an increase in the size of eutectic carbides, which, as stress concentrators, reduce impact toughness.
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