Papers by Author: A.G. Svyazhin

Abstract: The new high-strength stainless steels alloyed by copper and nitrogen and possessing high resistance to corrosion by active micro-organisms in carbon-oxidizing, heterotrophic and sulfate-regenerating bacteria mediums are developed. The introducing of small addition of nitrogen (about 0.22 %) to the corrosion resistant steel С0.5Cr15Ni5Cu2NMoNbTi results in a decrease of adhesive micro-organisms quantity on a sample surface by 8 times, while increasing of nickel content to 9 % results in their decrease only by 2 times. It is supposed that the effect of nitrogen can be related to formation of biocide substances. High copper (Cu = 2.5-5 %) nitrogen-containing cast steels are in austenitic (non-magnetic) condition. Due to a dendritic segregation, the structure of steel corresponds to a natural composite structure, and it is preserved on heating to high temperatures. After cold deformation with up to 85 % reduction, the steels preserve austenitic structure, and its hardness attains a level close to the hardness level of the martensitic structure. The developed corrosion-resistant antimicrobial steels with the increased hardness can be used as a material for the surgical instrument.

Abstract: Cast structure of ferric, austenitic and dual-phase high-nitrogen alloys and steels saturated with nitrogen at pressures of up to 3.2 MPa and solidified at cooling rates of 2 to 4•104 K/s has been investigated. Increasing the nitrogen concentration in the alloy and decreasing the cooling rate results in smaller nitrogen content in α and γ solutions and in larger content of crystallization nitrides.

Abstract: The structural and phase transformations and the strengthening of nitrogen-containing steels resulting from alloying and thermomechanical treatment have been investigated using X-ray diffraction analysis, optical microscopy, hardness measurements and tensile testing. For the modeling of thermomechanical treatment processes, a DIL 805A/D dilatometer with a deformation capability and a Gleeble 3800 simulator were used. Rational nitrogen or nitrogen plus carbon concentrations are determined by basic composition of an alloy. They are limited by the processes of precipitation of excess phases during crystallization and their dissolution during heating stage of the thermal or thermomechanical treatment. Combined alloying by carbon and nitrogen leads to significant complication of phase and structural transformations in steels, including hot deformation that manifests itself in changes of strain-stress diagram parameters. Effectiveness of increasing of a hot deformation resistance under alloying by nitrogen and carbon depends on a basic composition of steel, C/N ratio and temperature-strain rate deformation conditions.