Induction surface hardening of 42CrMo4 steel tubes designed for rotary percussive drilling equipment

42CrMo4 steel tubes are subjected to multiple induction heat treatments to obtain various hardened layer depths after spray water quenching. Current frequency, induction unit power and coil movement velocity along the tube axis are under consideration. The hardened layer depth is estimated along the transverse direction of the tubes using metallographic studies and microhardness measurements. An empirical equation is obtained for the hardened layer depth as a function of the induction heat treatment parameters. The laboratory test results are employed to develop the technology of the production of 42CrMo4 steel tubes designed for rotary percussive drilling equipment. The service life of induction hardened tubes during abrasive wear resistance field tests is approximately twice as long as that of conventionally nitrided ones. © 2016 Author(s)

The dependency of mechanical properties on the microstructure anisotropy index of some alloyed steels

The microstructure banding of the 4340, 42CrMo4 and 20NC11 alloyed steels is estimated using the approach of the ASTM E 1268 standard. The values of the anisotropy index and microhardness are obtained on the longitudinal specimens at various distances from the center of round steel bars with various diameters. Impact strength values in the transversal and longitudinal directions of the bars are obtained. The correlation of the anisotropy index values and the mechanical properties (microhardness and impact strength) of the steels under consideration is derived. © 2017 Author(s).Research are carried out (conducted) with the financial support of the state represented by the Ministry of Education and Science of the Russian Federation. Agreement (contract) no 14.578.21.0114 27.10.2015. Unique project Identifier: RFMEFI57815X0114

Improving the impact toughness of the Hy-Tuf steel by austempering

The microstructure and mechanical properties of the high-strength Hy-Tuf steel are studied after different heat treatment modes - conventional oil quenching and tempering, austempering in the bainite transformation temperature range. It is shown that the tempering embrittlement of the Hy-Tuf steel can be observed at temperatures ranging between 400 and 500 °C. The highest impact toughness of the studied steel for the case of conventional oil quenching and tempering (1.2 MJ/m2) can be achieved after high temperature tempering (600 °C), which also leads to the deterioration of tensile strength down to 800...900 MPa. The unique combination of high tensile strength (above 1300 MPa), elongation (up to 15%) and impact toughness (1.1 MJ/m2) is obtained after austempering at a low transformation temperature. © 2018 Author(s)

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. © 2013 Springer Science+Business Media New York

Anisotropic superconducting properties of single-crystalline FeSe0.5Te0.5

Iron-chalcogenide single crystals with the nominal composition FeSe$_{0.5}$Te$_{0.5}$ and a transition temperature of $T_{c}\simeq14.6$ K were synthesized by the Bridgman method. The structural and anisotropic superconducting properties of those crystals were investigated by means of single crystal X-ray and neutron powder diffraction, SQUID and torque magnetometry, and muon-spin rotation. Room temperature neutron powder diffraction reveals that 95% of the crystal volume is of the same tetragonal structure as PbO. The structure refinement yields a stoichiometry of Fe_1.045Se_0.406Te_0.594. Additionally, a minor hexagonal Fe_7Se_8 impurity phase was identified. The magnetic penetration depth \lambda at zero temperature was found to be 491(8) nm in the ab-plane and 1320(14) nm along the c-axis. The zero-temperature value of the superfluid density \rho_s(0) \lambda^-2(0) obeys the empirical Uemura relation observed for various unconventional superconductors, including cuprates and iron-pnictides. The temperature dependences of both \lambda_ab and \lambda_c are well described by a two-gap s+s-wave model with the zero-temperature gap values of \Delta_S(0)=0.51(3) meV and \Delta_L(0)=2.61(9) meV for the small and the large gap, respectively. The magnetic penetration depth anisotropy parameter \gamma_\lambda(T)=\lambda_c(T)/\lambda_{ab}(T) increases with decreasing temperature, in agreement with \gamma_\lambda(T) observed in the iron-pnictide superconductors

The Features of Bainite Transformation in Alloyed Steels

The main factors affecting the kinetics of isothermal bainite transformation in alloyed steels were determined using the algorithms of the computer modelling of phase transformations in the solid state. The experimental and calculated transformation kinetics was described and compared using well known Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation and Austin-Rickett (AR) equation. The effect of the initial configuration and the nucleation rate of the new phase nuclei on the parameters of the bainite transformation was analysed. The calculated kinetics of phase transformation at different nucleation rates was compared with the experimentally observed for HY-TUF and D6AC steels. The mechanism of the bainite transformation in alloyed steels was explained. © Published under licence by IOP Publishing Ltd.The work was supported by the Act 211 of Government of the Russian Federation, contract № 02.A03.21.0006, the Ministry of Science and Higher Education of the Russian Federation, project №11.1465.2014/K

An Analytical Model for Calculation of the Steel Hardness after Continuous Cooling

A number of modern engineering steel grades were analyzed using the CCT diagrams plotted by means of the dilatometer. The statistical analysis of the experimental data allowed for the determination of the equations connecting the critical cooling rate to achieve fully martensitic microstructure and the martensite hardness with the chemical composition of the steel. The dependence of the steel hardness on the cooling rate in the range of 0.1...30 C/s was determined. It was shown that this dependence had the logarithmic character for every studied steel grade. The equations connecting the coefficients of the logarithmic function with the chemical composition of steel were obtained. © Published under licence by IOP Publishing Ltd.The work was supported by the Act 211 of Government of the Russian Federation, contract № 02.A03.21.0006, the Ministry of Science and Higher Education of the Russian Federation, project №11.1465.2014/K, and by the state assignment of the M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, theme “Laser”

muSR investigation of magnetism and magnetoelectric coupling in Cu2OSeO3

A detailed zero and transverse field (ZF&TF) muon spin rotation (muSR) investigation of magnetism and the magneto-electric coupling in Cu2OSeO3 is reported. An internal magnetic field B_int(T=0) = 85.37(25) mT was found, in agreement with a ferrimagnetic state below Tc = 57.0(1) K. The temperature dependence of the magnetic order parameter is well described by the relation B_int = B(0)(1-(T/Tc)^2)^b with an effective exponent b = 0.39(1) which is close to the critical exponent B ~ 1/3 for a three dimensional (3D) magnetic system. Just above Tc the muon relaxation rate follows the power low \lambda (T)\propto (T/Tc - 1)^\omega with \omega = 1.06(9), which is characteristic for 3D ferromagnets. Measurements of B_int(T) with and without an applied electrostatic field E = 1.66 x 10^5 V/m suggest a possible electric field effect of magnitude \Delta Bv = Bv(0 V)-Bv(500 V) = - 0.4(4) mT.Comment: 7 pages, 5 figure

DEFECTS IN MODERN ENGINEERING STEELS

Изучены дефекты современных низкоуглеродистых машиностроительных сталей 18Х2Н4МА, 25Х2Н4МА, 25Г2С2Н2МА. Показано, что наиболее часто встречающимися дефектами металлургического передела являются неметаллические включения, структурная полосчатость. Установлено, что включения карбонитрида титана значительно снижают эксплуатационную стойкость тяжелонагруженных деталей. Рассмотрены дефекты, формирующиеся при термической и химико-термической обработке деталей.Defects of modern low-carbon engineering steels 18Kh2N4MA, 25Kh2N4MA, 25G2S2N2MA were studied. It was shown that the most frequently encountered defects in metallurgical processing are: non-metallic inclusions, microstructure banding. It has been established that the inclusion of titanium carbonitride significantly reduces the operational durability of heavily loaded parts. The defects formed during heat treatment and chemical-thermal processing of parts were also considered.Работа выполнена в рамках Гранта Президента РФ для молодых ученых - кандидатов наук МК-7929.2016.8

Dilatometric Research of Cr–Ni–Mo Steels during Isothermal Treatment

В проведенной работе дилатометрическим методом были исследованы Cr-Ni-Mo сталь исходного состава, а также стали с добавлением алюминия и кремния. Определены структура сталей в ходе изотермической обработки, а также влияние на структуру алюминия и кремния.In this work, Cr–Ni–Mo steel of the initial composition and alloyed with aluminum and silicon were investigated by the dilatometric method. The structure of steels during isothermal treatment, as well as the effect on the structure of aluminum and silicon, have been determined