Brykov A. Investigation on Structure and Operating Properties of Economically Alloyed High Strength Steel for Different Operating Conditions.

This work may be described by following factors. Object of investigation: high strength steel ДИ74-Ш. Goal: determination of area for rational utilisation ДИ74-Ш steel and developing of manufacturing processes for machine parts of high reliability. Methods of investigation: metallographic and other analyses such as dilatometric and X-ray. Theoretical and practical achievements: as a result of complex investigations of ДИ74-Ш steel determined are it's potential possibilities and basic regimes of heat treatment for different load-bearing components. Newness: isothermal diagram of austenite transformation is created for ДИ74-Ш steel for the first time. Critical points and how are they influenced by heating speed are determined also. Additionally, for the first time the effect of phase transformations in ДИ74-Ш steel on it's physico-mechanical properties and wear resistance is shown. Determined is the influence of degree of martensite tetragonality on microhardness of friction surface and wear resistance at abrasive wear of quenched steels. Application: the expected profit is achieved as a result of producing gears with ДИ74-Ш steel instead of 20ХГНМ when manufacturing "Tavria" cars.