International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

This study presents the effect of carbonation on 1020 carbonate, low fatigue. The carbonation of the samples was carried out at a temperature of 900 ° C and at a variable time of 5-9 hours. After the process of carbonization, the process was carried out with a temperature of 500 ° C and 30 minutes. The hardness of the sample was tested before the Chemical heat treatment was 206.5 HB and the hardness of the carbonated samples at 900 ° C and at 5 hours was 209.3HB and the hardness of the carbonated samples at 900 ° C and for 6 hours was 209.5 HB. The carbonated sample salad was 900 ° C and 9 hours 211.4 HB. The boxes were heated at (850-900) ºC in an electric furnace for different durations or times. Fatigue was tested for samples before and after carbonation carburizing contributed to the improvement in fatigue strength in different proportions. The degree of improvement depended on the depth (thickness) of the hardened layer and on the microstructure of a carburized steel.

A technique for determining the generalized degree of covalence of the interatomic Fe – C bond is proposed by the addition rule taking into account the fractions of Fe2C, Fe4C and Fe6C clusters and cementite in steel. The correlation dependence of the generalized degree of covalence of the interatomic Fe – C bond with the hardness of microstructures observed in eutectoid carbon steel, as well as the hardness of ferrite and cementite, is revealed. A functional relationship between the generalized degree of covalence of the Fe-C interatomic bond and the martensite hardness at different mass content of carbon is established, which ensures the correspondence of the
calculated and experimental data.

The impact of the parameters of thermomechanical treatment on the structural changes and micro-hardness of low- and medium carbon steels under a high hydrostatic pressure at high pressure torsion (HPT) is investigated. It is established that for HPT the deformation temperature has a decisive impact on the efficiency of refinement and hardening. This is caused by the effect of dynamic strain ageing (DSA) at 250 and 400оС during HPT. At the same time the level of accumulated strain in the sample intensifies the refinement under the effect of dynamic strain ageing (DSA). It should be noted that an increase of the carbon content to 0.2 % and 0.45% in steel leads to an increase in the temperature of dynamic strain ageing (DSA) to 400оС. It is stated that HPT under the effect of dynamic strain ageing (DSA) results in the formation of a gradient structure in the samples after five rotations of the anvil (емах=6.26) at a hydrostatic pressure of 6 GPa.

The effect of modes of electron beam welding on geometry of joint welds of constructional steels has been analyzed using steel 40X as an example. Microstructure and microhardness distribution in joint welds have been investigated. Necessity of preheating and subsequent heat treatment of metal in order to avoid hot cracking at electron beam welding has been determined.

The non-equilibrium thermodynamics analysis of the eutectoid transformation is executed into carbon steel. Onsager’s equations of motion are built for the model thermodynamics system describing eutectoid transformation. Dependences of basic kinetic pa-rameters of process are expected are speeds of height of pearlite and inter-plates distance from the size of subcooling became for the sta-tionary process of eutectoid transformation.