On the matter of dislocation-diffusion genesis of lamellar pearlite in high-carbon coil-rod mill products

Purpose. It is of scientific interest to carry out the research of particulars of pearlite transformation process in coil-rod mill products manufactured from steels of 85 and 85P grades in order to determine the influence of dislocation transformations in austenite to the forming of pearlite structure with lamellar morphology. The particular features of the dislocation transformations need to be analyzed. Moreover, it is necessary to reveal the capabilities to implement the controlled pearlite transformation in order to regulate the volumes of strength and plasticity of rolled metal goods from the rolling heat. The purpose of the study is to determine the particular influence of dislocation structure of hot-deformed austenite to the process of pearlite transforming in the steel of 85 and 85P grades establishing the dislocation-diffusion genesis of lamellar pearlite. Methodology. Industrial batches of hot-formed coil-rod mill products made of steel of 85 and 85P grades were the test material for the study. Research methods: metallography (optical, stereo-scanning microscopy) and X-ray crystal analysis. Obtained Results. It was determined that polygonizational dislocation transformations that occur in the sub-structure of hot-formed austenite as the result of thermoplastic deformation prior to the pearlite transformation, as well as interrelation of the dislocations with the interstitial atoms, affect its mechanism and ensure the capabilities of controlling of the structure forming processes in coil-rod rolled metal of large diameters made of steels of 85 and 85P grades. Originality. The particular features of pearlite transformation in steels of 85 and 85P grades which establish the dislocation-diffusion genesis of the lamellar morphology of pearlite. Practical value. Using of the outcomes obtained in the course of study will ensure the development of brand new modes of high-temperature thermo-mechanical treatment of high-carbon coil-rod mill products of wide grade assortment, and to fulfill its power- and resource-saving processing during the metal goods process stage.