Optimization of the Chemical Composition of Annealed Semifinished Products Made of the VT22 Titanium Alloy with Increased Strength Properties

A statistical analysis of the chemical composition and mechanical properties of ingots and rods made of the VT22 alloy (Ti—Al—Mo—V—Fe—Cr system) produced at various enterprises of Russia from 1970 to 2014 has been performed. The typical content of alloying elements and impurities in serial semifinished products of the VT22 alloy in terms of the aluminum [Al] $$_{{{\text{eq}}}}^{{{\text{str}}}}$$ and molybdenum [Mo] $$_{{{\text{eq}}}}^{{{\text{str}}}}$$ equivalents and their technological variation are statistically substantiated. The regression dependences of the strength properties of rods with diameters of 60–120 mm made of the VT22 alloy on the aluminum and molybdenum equivalents of alloying elements and impurities and double-annealing regimes are investigated. A classification diagram in the ultimate tensile strength—molybdenum equivalent—aluminum equivalent coordinates is plotted. Relationships are proposed for the rapid evaluation of the strength, plasticity, and impact ductility characteristics depending on the Rockwell hardness level. It has been statistically proved that, in order to achieve the highest strength properties of rods after annealing according to the industrial conditions, the composition of the VT22 alloy must be equivalent to [Al] $$_{{{\text{eq}}}}^{{{\text{str}}}}$$ = 6.5—7.0%, [Mo] $$_{{{\text{eq}}}}^{{{\text{str}}}}$$ = 12.0—13.0%.