Energy power parameter effect of hot rolling on the formation of the structure and properties of low-alloy steels

The temperature and degree of hot deformation for steel 10HFTBch have been determined. This made it possible to ensure an increase in the mechanical properties of this steel, namely, the ultimate strength up to 540–560 MPa, as well as the relative elongation up to 25–29 %. As a result, it became possible to increase the service life of wheels with increased carrying capacity. This, in turn, will make it possible to increase the load of the transported cargo by motor vehicles several times. The mechanism of the influence of the energy-power parameters of rolling on the formation of the macro- and microstructure of a two-phase steel in the process of hot deformation is disclosed. The applied scheme provided an increase in the homogeneity of the structure of the developed steel, which saved the central part of the rolled section from overheating. It has been established that a decrease in the temperature of the end of deformation leads to a decrease in the size of the recrystallized austenite grain, and, consequently, to a refinement of the ferrite grain. Also an important factor in preventing the growth of ferrite grains in the upper part of the ferritic region is the abolition of cooling of the steel in coils. The recommended mode for multicomponent alloy steel 10HFTBch is as follows: the temperature of the end of rolling is 850 °C, the beginning of accelerated cooling is 750 °C, and the temperature of strip coiling into a coil is 600 °C. The basis for ensuring the increased strength of two-phase steels is the ratio and distribution of structural fractions – ferrite (initial and precipitated from austenite), as well as martensite. When hardened by such traditional "martensite formations" as manganese, the ability to control properties is limited. This is reflected in a narrow range of variation in the strength and ductility of the developed steel. The optimal combination of strength characteristics of plastic properties reduces the metal consumption of the product by 15–25 %.

Effect of Hot Rolling on Microstructural Evolution and Wear Behaviors of G20CrNi2MoA Bearing Steel

Hot rolling can improve the mechanical properties after heat treatment by improving the microstructure. The effect of hot rolling (HR) deformation on the microstructural transformation of G20CrNi2MoA bearing steel in the subsequent CQT (carburizing-quenching and tempering) and RQT (reheating-quenching and tempering) processes was studied. The results indicate that the austenite grain size decreased by 20% after 45% hot rolling reduction, and the number of large-angle grain boundaries increased due to the recovery and recrystallization induced by hot deformation. The refinement effect of hot deformation on austenite grains was retained after dual austenitizing, and the large-angle grain boundaries and massive dislocation in the grains caused by hot deformation promoted the diffusion of carbon atoms during carburization, resulting in a higher surface carbon concentration. The refined grains and higher carbon concentration affected the volume fraction and size of undissolved carbides in RQT specimens. When the initial hot rolling reduction reached 45%, the average particle size of carbides decreased by 40%, and the area volume fraction increased by 37%. The Vickers hardness increased, but the friction coefficient and wear rate were significantly reduced with the increase in the initial hot rolling reduction. The main reasons for the improved wear resistance were fine grains, superior carbide distribution and high hardness.

Effect of Hot Rolling on the Intrinsic Properties of Aluminium-Titanium Bonded by PTFE/ C -Cyanoacrylate

The concern of this study shows the effect of hot rolling on the properties of a composite sheet prepared from aluminium bonded to titanium metals sandwiching PTFE (Du Pont)/graphite emulsion in perfluoro kerosene. The metals were soaked in hot oxygenated water and dried at 80 °C for 5 - 10 minutes to create a thin film of oxide. The metals were bonded with cyanoacrylate blended to the polymer emulsion that applied to the oxidized surface of the clean metals. Two coated surfaces sandwich the polytetrafluoroethylene (PTFE)/graphite emulsion followed by ‎hot-rolling. The rolling process was matched at 500- 560 °C (≈ 150 °C, over the melting point of the PTFE) under a pressure of 150-200 KPa. The obtained composite sheet was annealed at 550 °C to remove any residual stresses. Results revealed that upon cooling, the mix microphase would separate with the OH radicals on the metal surface and the CF displaced away. The temperature and time of cyanoacrylate application enhanced the extent of adhesion to create a homogeneous composite metal sheet. The effect of the hot rolling conditions was ascribed to the PTFE underactivity and incompatibility. Rolling imparts squeezing of the metals and changes the intrinsic properties. Linear thermal expansion coefficient of the composite sheet confirms partial diffusion of the soft metal in the harder one across the adhesive. The applied technique deforms the PTFE particles without inhibiting the adhesion strength of the cyanoacrylate. The prepared sheet has physical properties that would be suitable for bailiwick and structural ‎application.