| Abstrakt: |
The problem of increasing the efficiency of 13ХFА pipe steel for oil and gas wells by using selective selection of charges for smelting them in an electric arc furnace is considered. 4 batches of different chemical heterogeneity were studied. It was found that melt 1 from a purer charge 1 contains a smaller amount of harmful impurities in the form of surface-active substances (surfactants), which affect grain growth when samples are heated for quenching. Thus, melts 1 and 2, containing a smaller amount of surfactants in the charge, have a greater tendency to austenite grain growth and lower hardenability compared to melts 3 and 4, the charge of which is relatively heavily contaminated with surfactants. This is due to the low relatively free energy of melts 3 and 4. The study showed that at a relatively low tempering temperature (300 °С) there was an insignificant change in the mechanical properties of the samples (Rm, KC, etc.). Hydrogenation of steels significantly reduces the strength of steels from all melts, however, an increase in tempering time leads to an increase in long-term strength. In this case, the maximum impact strength (KC) of all melts is observed after normalization, but samples from melt 1 have a higher IC. When the samples were held (570 °С), the near-boundary layers of steel grains were enriched with P, Sb, Sn, As, leading to embrittlement and weakening of intergrain cohesion and a decrease in the energy of boundaries. In the process of testing at –80 °С, cracks along the grain boundaries are visible on the fractures of the samples after brittle tempering. By increasing the purity of metal waste for smelting pipe steel, it is possible to improve the complex of its properties, and hence the durability of seamless pipes for the oil and gas industry produced from it. [ABSTRACT FROM AUTHOR] |
