AUTHOR'S ABSTRACT
on a theme: «Research of influence of additional heating on structure and properties lowalloyed trumpet steels supervised proskating rinks for the purpose of realisation of hereditary hardening of products in the course of thermal processing
Author's: Lozovskaya Anna Viktorovna
Supervised a proskating rink more than 30 years are applied at manufacturing of thick sheets from the microalloyed trumpet steels, providing a demanded complex of mechanical properties at the expense of crushing of structure without application of additional heat treatment. Quite often after carrying out supervised proskating rinks in separate sites of sheets the non-uniform structure is formed, mainly with a point ferite grains 8-10 microns, however meet also large grains of ferite to 30 microns. Besides, on a thickness of sheet the structure is often observed non-uniform crystallography. It is strongly expressed ferrito-perlitnaja poloschatost. At the moment there is no accurate explanation of the reasons of occurrence of these phenomena. Heterogeneity of a microstructure and by crystallography structures in a condition after supervised proskating rinks leads to decrease in impact strength and resistance of metal to fragile destruction.
The work urgency is caused by necessity of increase of a complex of mechanical properties of sheets of the microalloyed steels for gazo-petrowire pipes of the big diameter of responsible appointment and finding-out in this connection mechanisms of structurization under the influence of hot plastic deformation and search of the technological decisions directed on perfection of structure, increase of its uniformity and dispersion at the expense of application of optimum modes of temperaturno-deformation influence on tolstolistovom a camp 3600 Open Societies "ÌÊ" Azovstal ».
As material for research samples served became 10Ã2ÔÁ, selected from a cast slab (further cast), and also from sheet rolled on technology supervised proskating rinks (further katanye). A part of samples were exposed to training from temperatures 700, 750, 800, 850, 900, 950°Ñ in water. A part of samples were exposed to annealing at temperature 930-950°Ñ with endurance of 15 mines and cooling to 550°Ñ with the furnace, the further cooling on air, then training from the same temperatures. On the received samples studied structure, defined the size of grain a secant method, and also measured hardness.
Results of measurement of hardness have shown that training rise in temperature leads to growth of values of hardness of a steel, thus hardness of samples, rolled from initial "cast" preparation, reaches the maximum values at training temperatures 900-950°Ñ, and hardness of samples received of preliminary deformed preparation – at 850-900°Ñ. It is necessary to notice that hardness of samples preliminary anneal above hardness of samples tempered without application of preliminary heat treatment.
Difficult conditions of working out of oil both gas deposits and necessity of more reliable and their economic transportation on pipelines from extraction places to the consumer become motive power for working out of new steels and technological process of their manufacture. For realisation of these problems development of trumpet manufacture will proceed in the XXI-st century with higher efficiency.
For the decision of a problem of accident-free operation main petro- and gas pipelines detailed studying of processes of destruction of metal of pipes, laws of change of thin structure and properties of trumpet steels is necessary at long operation of oil pipelines.
© DonNtU Lozovskaya A. V.
2009 |