Use Of Thermomechanical Treatment Research Articles

On the applicability of hardening mechanisms to low-carbon and low-alloy steels

On the basis of experimental studies, the approximate contribution of various hardening mechanisms to the yield point of low-carbon and low-alloy steels is estimated. It has been established that for hot-rolled steels (St.3sp and St5ps), solid-solution and grain-boundary hardening (54.0% and 29.0, %) make the greatest contribution to the yield point. The predominant strengthening mechanism of low-alloy steel 10HNDP is solid solution, a high proportion of which in this steel is explained by the resistance to moving dislocations from the side of dissolved atoms of Ni, Cu, P, and Cr in α-Fe. In low-alloy steel 16G2AF, along with these hardening components, the role of precipitation hardening is noticeable (20.0%). It is shown that thermomechanical treatment of steel grade St.5ps leads to an increase in the value of dislocation hardening up to 27.0% due to an increase in the density of dislocations and the retention of most of the dislocations in the rolled stock during accelerated cooling of hot-deformed austenite. It is noted that solid solution hardening with alloying with cheap alloying elements (Mn, Si), as well as dislocation and dispersion hardening through the use of thermomechanical treatment in combination with the addition of carbide and nitride-forming elements V (C, N).

Study of the Adhesion Strength of the Coating with Different Coating Methods to the Surface of Parts of «Shaft» Type

The article deals with the strength of adhesion of coatings with the parts of type «shaft». In accordance with the above separation, gas-thermal methods of spraying and thermal power sintering have an adhesive interaction of particles and coatings. The use of thermomechanical treatment of preformed coatings (applied by thermal spraying) makes it possible to increase the adhesion strength of coatings with parts of «shaft» type. For a quantitative assessment of the adhesion strength of coatings with the base metal, a shear coating method was used. An experiment to determine the adhesion strength of samples of steel with various applied coatings is considered. It was concluded that the adhesion strength of the coatings obtained using the hydrogen-propane mixture was slightly superior.

The Influence of the Regimes of Thermomechanical Treatments on the Features of Heterophase and Grain Structure of A V–Cr–Zr–Ta Alloy

A comparative investigation of the influence of thermomechanical treatment modes on the structural-phase state and mechanical properties of a V–Cr–Zr–Ta low-activation vanadium alloy is performed. It is demonstrated that the use of thermomechanical treatment improves the level of short-term strength at room and elevated temperatures. The alloy is characterized by high ductility in a wide range of temperatures irrespective of the regimes of thermomechanical treatment. It is found out that the V–Cr–Zr–Ta alloy possesses higher thermal microstructure stability and mechanical properties compared to those of the V–Ti–Cr alloys.

The investigation of the influence of thermomechanical treatment of the material of rotary cutter bit toolholders on its hardness

The causes of failure of the tangential rotary cutter bits of the road header during stonedrift in rocks of medium strength are analyzed in the article. It was revealed that the most typical cause of failure of cutter bits is premature wear of the toolholder (body) of the cutter bit. It is well known that the most effective way to improve the wear resistance is to increase hardness. The influence of the thermomechanical treatment of the material of the cutter bit toolholder on its hardness is studied. It was established that the thermomechanical treatment of the cutter bit toolholder material results in the increase of its hardness. It was found that the increase of material hardness is proportional to the increase of material strain intensity during thermomechanical treatment. It was concluded that the use of thermomechanical treatment can lead to the increase of both the hardness and wear resistance of the cutter bit material.

Elaboration of forging conditions on the basis of the precipitation analysis of MX-type phases in microalloyed steels

The paper presents analysis of the precipitation of MX-type (M—microalloying element, X—interstitial element) phases in austenite of constructional steels microalloyed with Nb, Ti, V and B, assigned for production of forged elements with the use of thermo-mechanical treatment. The calculations were conducted basing on the dependence of solubility product of MX-type phases in austenite as a function of temperature. The analysis was done on the basis of a simplified thermodynamic model for equilibrium conditions, assuming that individual MX-type phases are soluble in austenite. The solubility of TiN, TiC and NbC as a function of temperature as well as the simplified temperature sequence of precipitation of these phases have been determined. The effect of austenitizing temperature in a range from 900 to 1200°C on grain size of prior austenite was investigated to verify the analysis. A grain growth corresponds well with a course of a precipitation process, though the limitation of the current model arising from a lack of consideration of complex carbonitrides and the kinetics of a precipitation process should be taken into account. The studies provide the basis for proper design of manufacturing process of thermo-mechanical treatment for high strength forged elements of microalloyed steels.

Effect of the thermomechanical treatment of skelp steel of strength class K60 on its characteristics

Process parameters are determined for the production of cold-resistant skelp steel of strength class K60 in thicknesses up to 37 mm. The steel is obtained with the use of thermomechanical treatment (TMT). It is shown how the main parameters of TMT affect the structure and properties of the steel.

Crack resistance of rolled semiproducts made of alloys of the system Al-Cu-Mg in different structural states

1. An increase of the volume fraction of particles of excess phase from 1 to 2.7\2-3.5% leads to a decrease of Kcy by 5\2-10% and an increase of the growth rate of the fatigue crack by a factor of 1.5\2-2 for \gDK=850\2-1000 N/mm3/2. When the volume fraction of excess phases is 4.5%, the growth rate of the fatigue crack increases even with low values of ΔK. 2. In comparison with natural aging, artificial aging leads to reduced characteristics of static crack resistance and increased growth rate of the fatigue crack in the entire investigated range of \gDK. 3. The use of thermomechanical treatment in the production of rolled plates makes it possible to increase the strength properties approximately by 10% while the rupture work of the specimen with crack is reduced and the growth rate of the fatigue crack increases.