Presented are the theoretical and practical information on an important scientific and practice problem consisting in development of scientific basis for forming of microstructure and substructure during the plastic deformation, and also to the thermomechanical treatment of large-diameter wire rod, cold-worked semifinished product and finished fabricated metal products made of the perlitic grade steels based on the results of experimental researches of austenite disintegration kinetics for creation and commercial implementation of package of production engineering measures aimed on manufacture of high-strength building construction components with reduction material and energy costs.
This work reviews the current state of production and identifies the most meaningful process design aspects affecting the formation of hot-rolled steel properties. Bearing in mind the foreign standards requirements, perspective steel chemical compositions for production of high-strength cold-worked fabricated metal products were substantiated. For research purposes, steels with the following content of main chemical elements are selected: carbon 0.80…0.88 %, manganese 0.50…0.80 %, silicon 0.10…0.30 %. Chrome, vanadium and boron are selected as additional chemical elements for enhancement of initial strength grade of wire rod.
Revealing of alternative influence capabilities due to the reasonable combination of hot deformation completion temperature, post-deformation interval duration, austenite stability, cooling onset temperature and cooling method parameters at the finishing stage of thermomechanical treatment enabled purposeful influence upon the structure formation processes at making the wire rod of 8.0…16.0 mm in diameter of С82DCr, С82DV, С82DCrV, С86DВ steels.
Investigated was impact of temperature-strain parameters on the austenite dynamic recrystallization kinetics in steels with carbon content of up to 0.88 % within the temperature interval form 900 C to 1200 C. Obtained results enable sound approach to the correction of rolling conditions calibration tables and making the proper changes to the temperature-time specifications of fabrication process at the end stage of thermomechanical treatment of wire rod.
Impact of hot deformation dislocation substructure on the perlite transformation behavior was investigated. At the high-carbon steel cooling, interaction between the dislocations and carbon, boron, nitrogen atoms and their complex compounds determines the instantaneous formation of cementite and ferrite nuclei (longitudinal front of perlite colony). In particular, transversal (diffusion) front accounts for the ferrite and cementite lamellas width increase, and admixture atoms contribute in perlite deformation substructure inheritance. Additional factor impacting the perlitic transformation behavior is the presence of non-metal inclusions, which are rather common at the conjunction of perlite colonies.
Investigated are features of deformation evolution of thin-lamellar perlite substructure at drawing of hot-rolled steel C86DB with the low, moderate and high deformation ratios.
The energy-efficient schemes are introduced into the industry for the production of high-strength structural building components complying with the requirements of international and national standards: 5.0Вр1400-Р1 and 6.0Вр1400-Р1 rebars for pre-stressed reinforced concrete structures; cold-worked reinforcing bars of nominal 9.6 mm in diameter for manufacturing the new generation reinforced concrete sleepers; 5.0B1500-P1 semifinished billet for production of steel PSC strands used for containments of the nuclear power plant safety localization system structures; 17 design PSC strands of 9.3 mm; 12.5 mm and 15.2 mm in diameter for pre-stressed reinforced concrete structures.
Actual economic benefits achieved at production and reprocessing of C86DB perlite grade steel wire rod into the high-strength cold-worked metal products for the pre-stressed building structures in amount of 1,007.813 tons made UAH 1,348,867.26, which is equivalent to UAH 1,338.41 per 1 ton of finished steel products.
Keywords: wire rod, microstructure, substructure, properties, perlitic transformation, interphase boundaries, deformation, non-metal inclusions, high strength metal products.
