ННІ "Дніпровський металургійний інститут" (ДМетІ)

Permanent URI for this community

https://crust.ust.edu.ua/handle/123456789/19780
ENG: Dnipro Metallurgical Institute

Browse

Browsing ННІ "Дніпровський металургійний інститут" (ДМетІ) by Author "Aftandiliants, Yevhenii"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Influence of K2ZrF6 and SiO2 on Refining Ability of Flux for Manufacturing Bimetallic Castings
    (Latvia University of Life Sciences and Technologies, Jelgava, 2024) Aftandiliants, Yevhenii; Gnyloskurenko, Svyatoslav; Meniailo, Helena V.; Khrychikov, Valerii Ye.; Lomakin, Viktor
    ENG: Bimetallic material is considered as an advanced functional material due to the unique physical and mechanical properties varied over the layers. Formation of bimetallic castings with steel base greatly depends on diffusion coupling with the second material working layer at elevated temperatures. The common technological problem is to remove the oxide films from the solid steel surface while its heating prior pouring melt of the working layer. This work studies the protective refining fluxes matching the selected requirements of good wetting the surfaces of solidified metal, effective protection against oxidation in the working temperature range, easy separation after pouring liquid metal and high refining capacity for oxides. The most effective fluxes based on Na2B4O7 and B2O3 compounds were used. To improve their ability to enhance wetting, work of adhesion and reduce surface decarbonization addition of K2ZrF6 and SiO2 to the flux in the amount of 3-4 wt.% was proposed and investigated. It was established that such additions increased wettability up to 9 and 20%, respectively and reduced the average rate of decarburization in the temperature range from 800 to 1000 ºС on 57 and 37%. The complete reduction of iron from scale on the steel surface was observed, while in the case of Na2B4O7 – B2O3 system it achieved 30-40% only. The mechanism explaining such a result is proposed to be due to the prevailing effect of zirconium in protecting the surface of the steel base from the oxidation and decarburization. The important result of the study is the recommendation of optimal flux composition (wt.%): Na2B4O7 – from 60 to 80; B2O3 – from 10 to 30; K2ZrF6 - from 3 to 4; SiO2 from 3 to 4. Thus, such flux could improve the production of steel based bimetallic castings and increase their properties.
  • Thumbnail Image
    Item
    Influence of Technological Factors on Formation Process of Bimetallic Castings
    (Latvia University of Life Sciences and Technologies, Jelgava, 2023) Aftandiliants, Yevhenii; Gnyloskurenko, Svyatoslav; Meniailo, Helena V.; Khrychikov, Valerii Ye.
    ENG: The analysis of the modern state of wear-resistant metallic material production showed that one of the promising directions for improving their quality is the use of bimetallic steel-cast iron castings, which have a complex of properties differentiated over the volume and surface of the products. However, the problem of obtaining a high-quality joint of the steel base and the working cast iron layers is not completely solved at present. So, the research aims to determine the quality criterion of a good diffusion joint and to study the selected technological factor influence on the formation process of bimetallic castings using the developed mathematical model. The paper examines the effect of the steel base temperature at liquid cast iron pouring over it, the temperature of pouring cast iron, as well as the ratio of liquid cast iron mass to the unit surface of the steel base on the contact surface temperature as selected quality criteria, and the structure of the transition diffusion layer of bimetallic castings. It was determined that a high-quality joint is realized when this temperature is larger than the solidus temperature of the cast iron. Moreover, the results of the mathematical model application showed maximum contribution of the liquid cast iron mass/steel unit surface ratio, less effect of the pouring iron temperature and minimum influence of the solidified steel base temperature onto the quality criteria. The metallographic analysis established the diffusion joint formation in the transition steel-cast iron layer consisting of pearlite on the side of the steel base and without the carbide matrix area on the side of the working iron layer. The results obtained are of great importance for the designing bimetallic machine parts worked under intensive wear conditions.
  • Thumbnail Image
    Item
    Optimization of Production Process of Structural Steel Modified with Nitrogen and Vanadium
    (Latvia University of Life Sciences and Technologies, Jelgava, 2022) Aftandiliants, Yevhenii; Gnyloskurenko, Svyatoslav; Meniailo, Helena V.; Khrychikov, Valerii Ye.
    ENG: Structural steels are the most promising material, particularly in machine design. An important issue is to match their properties with the exploitation demands. It can be achieved by the optimization of the steel production process, i.e. formation of the primary and secondary structure under modification with nitrogen and vanadium, proposed in this research. At the experiments the structural steels were melted, modified with nitrogen and vanadium, subsequently deoxidized with aluminium, cerium and lanthanum. The steel samples were tested to reveal the mechanical properties and study the effect of modifying processing. The results have shown that some decrease in plastic properties, the impact strength and an increase in the critical temperature of brittleness is not due to vanadium nitride hardening of steel, but could be associated with imperfect technology. The final deoxidation of steel is often performed with aluminum of at least 0.05% in order to stabilize the grain of the structure during austenitizing heating. It was established that the necessary condition for the effective influence of nitrogen and vanadium should be a higher formation temperature of vanadium nitrides than aluminum nitrides in steels. Calculations showed that this condition is realized when the content of aluminum in steel is less than 0.03% and vanadium - 0.10%. The results of the performed experiments have shown that in this case there is a simultaneous increase in the strength properties and impact toughness of steel. Based on the obtained results the recommendations for the industrial process of steel making was formulated as below. In foundry shops with inductional melting furnaces it is necessary to additionally deoxidize steel with cerium and lanthanum. So, comprehensive optimization of the content of nitrogen, vanadium and deoxidizers in steel, as well as the temperature of austenitizing heating ensure increase in mechanical properties without reduction in plasticity and toughness.