M. V. Maisuradze

Numerical Simulation of Pearlitic Transformation in Steel 45Kh5MF

A dilatometric study of steel 45Kh5MF used for making rolling mill rolls is performed. The results of the dilatometric and metallographic analyses are used to determine the kinetics of the perlitic transformation in the steel under continuous cooling. The developed method of numerical simulation of structural transformations under continuous cooling is used to solve the inverse problem and to plot a computational isothermal diagram of decomposition of supercooled austenite in steel 45Kh5MF in the range of perlitic transformation. To check the solution obtained an experimental isothermal diagram of decomposition of austenite in steel 45Kh5MF in the perlitic range is plotted. The data of both diagrams match accurately enough.

Design of Water-Drip Cooling Facilities for Heat Treatment of Mill Rollers

Water-drip cooling devices based on centrifugal jet atomizers are studied experimentally. Their main operating characteristics such as the irrigation density, the uniformity of the distribution of irrigation over the cooled surface, the dependence of the heat transfer factor on the surface temperature, etc. are determined. The effect of the design and production parameters of the quenching facilities on their operating characteristics and mode of cooling of large steel articles is considered for mill rollers as an example. The results of the tests are used to design cooling facilities and heat treatment processes for mill rollers with the use of water-drip quenching.

Experience in Improving Silicon Steel Component Heat Treatment Quality

Inspection of the heat treatment section is performed on the basis of studying results of supercooled austenite transformation in silicon steel and modeling for heat treatment in a Heat Treatment Solution (SYSWELD) program. Deviations are revealed for the hardening production process, after whose avoidance uniform distribution of structural components and hardness is achieved through the cross section of components, and this provides an improvement for finished object set of properties.

Heat Treatment Technology for High-Strength Engineering Steel Variable Cross-Section Components

Heat treatment parameters providing a required level of mechanical properties for different component parts are determined on the basis of experimental data about supercooled austenite transformation in engineering chromium-molybdenum steel, and also results of numerical modeling of variable cross-section components of this steel in a QForm 7 program.

Transformations of Supercooled Austenite in a Promising High-Strength Steel Grade Under Continuous Cooling Conditions

Special features of the transformations of supercooled austenite occurring under continuous cooling of a promising high-strength steel grade not standardized in the Russian Federation are determined. A method for evaluating the volume fractions of structure constituents formed in the steel as a result of cooling from 925°C at various constant rates within 0.025 – 75 K/sec is proposed and tested. The results are generalized in the form of a thermokinetic diagram of transformations of supercooled austenite.

Investigation and Development of Spray Cooling Device for Heat Treatment of Large Steel Forgings

Methods for determining the main service characteristics of cooling devices (irrigation density, its distribution on the cooling surface, and dependence of the heat-transfer coefficient versus temperature) are described. An investigation of technological and design parameters of spraying jets and their effect on cooling capability of large steel forgings (e.g., hot-rolling mill rolls) are presented. The technological parameters under consideration are water pressure in spraying jets and the number of spraying jets in a cooling device. The varied design parameters of spraying jets are the diameters of the channels in spraying jets, the distance between the jets, and the distance from the cooling surface. The results of the experiments were applied to obtain the dependency between technological and design parameters versus main service characteristics of spraying jets to develop and optimize the technology of heat treatment of large steel forgings. These relations were applied for modeling spray cooling of hot-rolling mill rolls.

Cooling Capacity of Jet Spraying Devices for Large Steel Parts Heat Treatment

Basic technological characteristics of a designed water-drop cooling device (irrigation density, its distribution on the cooled surface, and temperature dependence of the heat transfer coefficient) were determined. The effect of technological and design spraying jet parameters on the cooling capacity of large steel parts (hot rolling mill rolls) was obtained. Among the technological parameters under consideration was the water pressure in front of spraying jets and the number of spraying jets in a cooling device. The varied design parameters were the diameters of the spraying jet channels, the distance between the jets, the distance to the cooled surface, and the operating mode of the cooling device. The experimental data was used to obtain the correlation between listed parameters and basic technological characteristics of spraying jets in order to apply the uniform cooling of mill rolls during heat treatment.

Thermal Stabilization of Austenite During Quenching and Partitioning of Austenite for Automotive Steels

Published sources are reviewed devoted to use of heat treatment for high-strength automotive steels based on the phenomenon of carbon redistribution between martensite and untransformed austenite during quenching and partitioning. The possibility of implementing quenching and partitioning heat treatment providing presence of an increased amount of retained austenite in the microstructure is shown by experiment on the example of silicon-containing steels with good hardenability.

Describing the isothermal bainitic transformation in structural steels by a logistical function

A new analytical description for the bainitic transformations in steel on isothermal holding is proposed, on the basis of a logistical function of the holding time (in logarithmic form). The model is characterized by the parameters a and b, which are constant in the given experimental conditions (austenitization temperature, isothermal holding temperature and time, chemical composition of the steel, etc.). The calculated temperature dependence of a and b is in good agreement with experimental data. In further research, the physical significance of coefficients a and b in the logistical function should be refined.

Quantitative Evaluation of Structural Alloy Steel Banded Structure

Quantitative estimation of structural banding in alloy steels 40KhN2MA, 38KhGMA, and 20KhN3A is performed. The dependence of anisotropy index according to GOST R 54570 (ASTM E 1268) on the steel bar diameter and sample selection position is determined. It is shown that there is a direct relationship between structural banding, specified by the anisotropy index and steel mechanical properties (scatter of the microhardness values and anisotropy of the impact strength).