Grinenko Dar'ya Vasil'evna
Author's abstract of master work
"INFLUENCE OF DEFORMATION AND THERMAL PROCESSING ON STRUCTURE AND PROPERTY OF STEEL 10Ã2ÔÁ WITH VARIOUS INITIAL CONDITION"
Scientific adviser: Doctor of Philosophy Gorbatenko Vladimir Petrovich
Controlled rolling is the most widespread way of manufacture of sheets from , low-carbon steel. Prominent feature of steel, processed on controlled rolling, are formation foliated structures and anisotropy of properties which reduce quality of metal and reduce service life of pipe plates. Foliated structure is kept even after carrying out of additional thermal processing. Therefore studying of the possible reasons of its display and opportunities of elimination is the important and actual problem.
Material and technique: researches were carried out on samples of steel 10Ã2ÔÁ, selected from a cast slab (further cast), and also from a plate thickness of 15,7 mm, rolled on technology controllable controlled rolling (further rolled) Tc.rolling=720-7400C.
The given samples processed on a following regime: having heated up to temperatures 950 – 1150 0Ñ, the first pass of deformation (ε=25-30%), cooling with the furnace up to temperature 640 – 660 0Ñ, the second pass of deformation (ε=50-60%) and cooling on air. After deformation samples were subjected to thermal processing at 500, 550, 600 and 650 0Ñ in during 18 minutes. On samples magnetic properties, hardness, microhardness were measured, a microstructure were studied, and also defined quantity and the size of structural components in longitudinal- and cross-section.
The purpose of the given work is comparative studying structure and property of steel 10Ã2ÔÁ with a different initial condition after controlled rolling on the regulated regime and the further thermal treatment.
Results of measurement of hardness have shown, that rise in temperature rolling leads to increase in values of hardness of "cast" samples and to decrease in its values in «rolled» samples. Microhardness of ferrite of "cast" samples decreases with rise in temperature of heating to rolling, thus in «rolled» samples it practically does not change.
Carrying out of annealing leads to increase in hardness. At increase in temperature of annealing (500-650 0Ñ) hardness decreases in comparison with 5000Ñ. Value of hardness after annealing at 6500Ñ is less than value in an initial condition, however in the cast sample (Ò rolling=9500Ñ) hardness above than in an initial condition.
Results of measurement of residual magnetization have shown, that rise in temperature of rolling leads to reduction of values Í1 in samples. Thus value of residual magnetization Í1 in «rolled» samples above than at "cast" samples. Carrying out of annealing leads to reduction of value of residual magnetization.
It is known, that formation of foliated structures in controlled rolling steel is caused by carrying out of deformation in α-γ areas when processes of recrystallization are practically suppressed. The scheme of deformation of samples excludes to rolling in biphase area that should lead to formation of regular ferrite-perlite structures. However irrespective of temperature of heating in «rolled» samples the foliated structure is formed. The initial "cast" samples were deformed on close regimes, practically did not possess such feature of structure.
Researches have shown, that the initial condition of steel can render essential influence on processes of structurization at the subsequent hot plastic deformation in connection with demonstration of a structural heredity.