Economically alloyed steels with a strength level of 2200-2600 MPa
The possibility of obtaining high-purity steels 65С2А and 65С2ВА melted in a vacuum induction furnace, with the level of strength of about 2500 MPa is studied. It is shown that without the use of special processing methods this level of strength can't be achieved. Using high-temperature thermomechanical treatment (HTMT) and treatment to ultrafine grain gives the opportunity to get tensile strength σ <sub>B</sub> ≈ 2600 MPa, ψ = 20-35% and КСU= 0.25-0.4 MJ/m <sup>2</sup>. Upon alloying mild steel by carbide-forming elements (65С2А steel) the ductility КСU= 0.4 MJ/m <sup>2</sup> is provided, but plasticity is relatively low ψ < 20%. Without the carbide-forming elements (65С2А steel) value of КСU is 0.25-0.30 MJ/m <sup>2</sup>, but the value of plasticity is ψ = 35-40%. Study of the fracture structure showed that due to HTMT the dimensions of the chipping surfaces are reduced, intergranular fracture sites are disappeared and the most important thing is that the area of the fracture occupied pits is increased. It can be assumed, that this is a consequence of the general dispersion structure in HTMT.