[en] Fatigue characteristics were assessed for cyclic load of steel 15Kh2NMFA used for the production of nuclear reactor pressure vessels. An equation is given describing the curve of the fatigue crack propagation rate, as is the threshold value of the amplitude of the stress intensity factor for the steel. Crack formation and propagation are assessed for sharp cracks, cavities and inclusions, and a surface notch. (E.S.)

[en] Process of calibration and deep centring of blanks before broaching is developed and studied. Investigations are performed at a semi-industrial screw rolling mill MISiS-100 T. Blanks made of 40Kh, 60, 50, 45KhN2MFA, 30KhGSNA steels 80, 85, and 90 mm in diameter and 300 mm long were calibrated and centered after heating in a furnace to a depth of 200 mm at shafts and faces with different calibration. 30KhN2MFA steel is chosen for face material; heat treatment is conducted under the following conditions: heating up to 950-1000 deg C and hold-up during 30-35 min with the following cooling in the air. The above experimental investigations reveal that the process of calibration and deep centring accomplished at a three-shaft screw rolling mill is rather stable and provides a high accuracy of centering hollow marking

[en] 15Kh2NMFA steel of Czechoslovak and Soviet make was ussed for the experiment which involved tests of low-cycle and high-cycle fatigue at temperatures of 20 degC and 350 degC. Cyclic deformation curves and lifetime curves were obtained in form of a Manson-Coffin dependence. It was found that fatigue properties of the two steels are very similar. The Soviet steel is more suitable for uses under conditions of controlled stress amplitude, the Czechoslovak type is more suitable for areas with limited lifetime. (E.S.)

[en] The paper describes a procedure and results of research in the effect of preliminary cyclic overload and underload on the vibration decrement and residual life the cyclically strengthened 40Kh steel. It is shown that ageing results in a decrease of the vibration decrement irrespective of an increase or a decrease in residual life of the material under study

[en] 15CrNiMoV steel was used for the experiments; its chemical composition is tabulated. Samples annealed for 1 hour at a temperature of 950 degC, deformed at the same temperature by 5% or 20% and quickly cooled only showed initial stages of recrystallization. Partial recrystallization at zero dwell was manifested in samples annealed for 1 hour at 1200 degC, cooled to 1050 degC and deformed. Dynamic recrystallization at zero dwell took place in samples annealed for 1 hour at 1200 degC and deformed at this temperature. The dependence of the diameter of austenitic grain on dwell and annealing temperature is shown graphically. It was found that very coarse austenitic grain could be refined to grain size 20 - 45 μm by as few as two recrystallizations. The basic mechanical properties of completely heat-treated steel met technical conditions. Samples with higher temperatures of forming had higher yield point with the same treatment than samples with lower forming temperatures. Hardness was investigated of martensitic and bainitic structures with the same tempering. The hardness of bainite tempered at 640 degC at dwells of more than 2 hrs was higher that the hardness of martensite tempered in the same way. The structures of tempered bainite and martensite had better transient temperatures and brittle crack characteristics than tempered bainitic-ferritic structures at comparable yield points. (E.S.)

[en] Aimed to study experimentally the behaviour of solidified crust when a continuous casting leaves a casting mold steel billets of rectangular (350x460, 480x480) and round (500 mm) sections were cast. Solidified crust experiences ferrostatic pressure of liquid metal and can be deformed. The dependence of deformation on temperature and continuous casting velosity is determined. For steels types 45, 40Kh and 12KhN3A permissible casting rates are estimated which allow one to avoid solid crust rupture.8 refs., 6 figs., 1 tab

[en] The evolution of steelmaking practices has continually improved steel quality by reducing the impurities content to extra-low levels and the intensity of segregations. The paper illustrates the effects on the weldability of steel, in particular: Of extra-low sulphur content on the sensitivity to cold cracking of low alloyed steels for off-shore construction, for nuclear reactor pressure vessels, etc; of reducing segregations areas on the sensitivity to reheat cracking of nuclear steels; of extra-low phosphorus content on the toughness of HAZ of steels for petrochemical reactors and steels for containment vessels for the transport of irradiated fuels. (orig.)

[en] The 40 Kh steel is taken as an example to investigate the dependence of electrochemical parameters in the crack tip and characteristics of corrosion static cracking resistance of martensitic steel on the composition of environment. The tests are performed in acidic and alkaline solutions prepared by adding HC or NaOH in distilled water. It is established that growth of pH value of initial solutions trom 0 to 13 brings about linear increase of a threshold stress intensity factor. It is found that acidic medium in the crack tip preserves up to pH 13 of initial medium. The possibility of corrosion crack propagation in alkaline solutions according to the mechanism of hydrogen embrittlement is proved

[en] The change in the structure and phase composition of 12Kh1MF steel depending on residual content of nitrogen and aluminium has been considered. Steel with nitrogen content from O.010 to 0.040% and aluminium content from 0.010 to 0.060% has been studied. Steel samples after normalization and tempering, as well as additional prolonged ageing, have been subjected to phase, chemical and X-ray structural analyses. Prolonged ageing of the samples, imitating conditions of exploitation, is carried out under laboratory conditions at the temperature 570 deg C without strain, so as to study structural changes in the steel. Later a calculation according to parametric dependence for the operating temperature 540 deg C is made and ageing duration of 97500 hr lthe calculated service time of power units is 100 thousand h) is obtained. It is shown, that increased nitrogen content (up to 0.025-0.040%) and aluminium (up to 0.052-0.060%) in steel 12Kh1MF produces effect on the amount, type and dispersion of carbide phases precipitated. At the increased nitrogen content instead of hardening phase-carbide Mel-large particles of vanadium nitrides are precipitated as well as carbide Me²³C₆, mainly on grain boundaries. At high content of aluminium vanadium carbide dispersion decreases and aluminium nitrides are precipitated, in some cases in the form of segregations. Such changes in the structure result in brittle fracture, ductility loss and decrease in long-time strength. To obtain high refractory properties of chromium-molybdenum-vanadium steel

[en] Results of an experimental study of the 40Kh steel hardening law are given. The hardening of the material of concern is shown to be complicated, for there occurs a widening of the surface, its displacement towards plastic strain, which results in a partial variation of the surface shape. Equations are given describing this type of hardening