V. V. V’yukhin

A computer-aided plant for studying the kinematic viscosity of high-temperature metallic melts

A system for studying damping of torsional vibrations of a crucible with a melt is described. Reasons for errors and their values are analyzed. The patented technical solutions decreasing errors of measuring the kinematic viscosity to 3% are designed and implemented. The system is intended to reduce measurement times and simplify operation of the plant’s operator.

Viscosity of high-entropy melts in Cu-Sn-Pb-Bi-Ga, G-Sn, Cu-Pb, Cu-Ga, and Cu-Bi equiatomic compositions

Temperature dependences of kinematic viscosity of high-entropy melts (HEM) of the composition, at %, Cu-20Sn-20Pb-20Bi-20Ga, Cu-50Sn, Cu-50Pb, Cu-50Ga, and Cu-50Bi are investigated in a temperature range from 1550 to 1300°C. It is shown that melt overheating above a definite temperature (thom) leads to the appearance of viscosity hysteresis, which indicates a variation in the structural state of the HEM. The values of thom for all studied samples are in limits of 925–1185°C. It is found that heating the HEM to definite temperatures (t*) leads to a variation in the activation energy of viscous flow (E) and entropy multiplier (A) in the Arrhenius equation: ν = Aexp[E/(RT)]. Entropy of viscous flow (ΔS#) for studied HEMs is investigated in terms of the Airing theory. It is revealed that the magnitude of ΔS# for a five-component Cu-Sn-Pb-Bi-Ga melt in a cooling mode is smaller than during heating by a factor of 2.6. The rheological characteristics of HEMs allow us to consider these melts promising functional materials: solders, heat carriers, and electric contacts.

Influence of defects on the ductility of liquid 9X2MΦ and 75X3MΦ steel

Viscosimetric data on liquid 9X2MΦ and 75X3MΦ steel taken from working rollers of a reversible rolling mill with different ultrasonic behavior illustrate the influence of defects recorded in ultrasound monitoring on the temperature and time dependence of the liquid steel’s kinematic viscosity. A Krautkremer ultrasonic defectoscope is employed in monitoring. The viscosity of the liquid steel is measured by means of damping torsional oscillations of a crucible with melt in heating and subsequent cooling in the range 1500–1580°C.

Relation between the Crystal Structure of 35KhGF Steel and the Viscous Flow Characteristics of the Forming Melt

The effect of the crystal structure of 35KhGF steel on the temperature dependence of the kinematic viscosity of the melt has been studied at temperatures of 1450–1780°C. The crystal structure of 35KhGF steel changes as a result of heat treatment, namely, normalizing and tempering. EBSD analysis is used to study the crystal structure of the steel. The kinematic viscosity of the liquid steel is measured by the oscillating crucible method during heating and subsequent cooling. The supercooling of the liquid metal before solidification and the activation energy of viscous flow are dependent on the heat-treatment conditions. This correlation is discussed in terms of metallurgical inheritance.

Measurement of the electrical resistivity of liquid 32G2 and 32G1 steels by the rotating magnetic field method

The resistivity of liquid 32G2 and 32G1 steels are measured using the rotating magnetic field method to obtain information on their liquid structures. The technique of measurements is described and the influence of self-induction and viscosity on the resistivity is estimated. The results are discussed in the framework of a microheterogeneous structure of a metallic melt. A conclusion is made about the character of the influence of slag inclusions detected by magnetic powder and ultrasonic methods on the temperature dependences of the resistivities of liquid 32G2 and 32G1 steels. The change in the temperature coefficient of the resistivity of the melt on heating to 1700°C is interpreted using the Nagel–Tauc model.

Effect of slag inclusions on the density and the surface tension of liquid 32G2 and 32G1 steels

The density and the surface tension of liquid 32G2 and 32G1 steels are experimentally studied. Samples are cut from oil-and-gas pipes having different degrees of imperfection. The experimental results are used to find the effect of the defects detected by magnetic-powder and ultrasonic inspection methods on the temperature dependences of the density and the surface tension of liquid 32G2 and 32G1 steels. The results obtained are interpreted in terms of the concepts of a microheterogeneous structure of metallic melts. Microheterogeneities are irreversibly destroyed when the liquid 32G2 steel is heated to 1700°C and the 32G1 steel, to 1750°C.

Surface tension of liquid high-entropy equiatomic alloys of a Cu–Sn–Bi–In–Pb system

An experimental study of the temperature dependences of the surface tension of liquid high-entropy equiatomic alloys of a Cu–Sn–Bi–In–Pb system is conducted. Measurements are made within the temperature range of tL to 1300°C in the mode of heating and subsequent cooling of a sample. Overcooling of a melt prior to crystallization is detected. The depth of overcooling grows along with the number of components in the melt, while the temperature coefficient of surface tension falls. The experimental results qualitatively interpreted within the concepts of the specific surface entropy of a liquid.

Influence of the chromium concentration on structure formation in liquid chromonickel alloys

The electrical resistivity of liquid nickel–chromium alloys is studied as a function of the temperature and concentration. Experimental data indicate that the dependence of the alloys’ electrical-resistance isotherms on the concentration is nonlinear. On the basis of the temperature and concentration dependence of the electrical resistivity of nickel and chromium alloys, the optimal conditions for the formation of microhomogeneous and equilibrium structure in the melt may be determined. The electrical-resistance isotherms of chromonickel alloys may be qualitatively explained on the basis of percolation theory and a quasi-chemical model of the microheterogeneous structure of molten metal alloys. The structure formation of chromonickel melts with increase in chromium concentration is characterized by the successive formation of clusters with different structure and dimensions.

ВЛИЯНИЕ КОНЦЕНТРАЦИИ ХРОМА НА ПРОЦЕСС СТРУКТУРООБРАЗОВАНИЯ ЖИДКИХ ХРОМОНИКЕЛЕВЫХ СПЛАВОВ

The temperature and concentration dependences of the electrical resistivity of the nickel-chromium alloys in the liquid state have been studied. Experimental data suggest a nonlinear concentration dependence of the electrical resistivity isotherms of the studied alloys. The results of studies of the temperature and concentration dependencies of the electrical resistivity of nickel-chromium alloys allow determining the optimal conditions for the formation of microhomogeneous and the equilibrium structure of the melt. Using of percolation theory and quasichemical model of microheterogeneous structure of liquid metal alloys gives the possibility to explain the nature of the isotherms of the electrical resistivity of nickel-chromium melts. The process of structure formation of nickel-chromium melts with increasing chromium concentration has been presented in the form of schemes, reflecting the gradual formation of different clusters, featuring by their structure and size.

Influence of defects on the viscosity of liquid 32Γ1 and 32Γ2 steel

Liquid 32Γ1 and 32Γ2 steel samples obtained from oil and gas pipe with different defect contents are studied viscosimetrically. The influence of the defects recorded by magnetic-powder and ultrasound methods on the temperature and time dependences of the kinematic viscosity for liquid 32Γ1 and 32Γ2 steel is determined. The MACNDT Echomac instrument employed is designed for the ultrasonic detection of defects in oil and gas lines. The viscosity of the liquid steels is measured by means of damping torsional oscillations of a crucible with the melt during heating and subsequent cooling of the samples in the range 1460–1810°C.