employee
RPE Valma (the Materials Science Department, Senior Engineer)
employee
Samara, Samara, Russian Federation
employee
Samara, Samara, Russian Federation
employee
Samara State Technical University (Associate Professor)
employee
Samara, Samara, Russian Federation
UDC 620.193.4
Russian Library and Bibliographic Classification 342
The paper presents the results of evaluating the effect of 20L steel structure on the resistance to sulfide corrosion cracking in mediums with different concentrations of hydrogen sulfide and pH of the medium. During the research, two heat treatment modes were carried out for 20L grade steel, namely temper hardening (the first mode) and normalization (the second mode), and solutions were selected to study the resistance of 20L grade steel to sulfide corrosion cracking. The microstructural analysis showed a significant difference in the phase composition of 20L steel material depending on the heat treatment mode. The study also revealed that all samples subjected to tempering have no resistance to sulfide corrosion cracking and are destroyed before the end of testing, even in the medium with an average content of hydrogen sulfide and a partial pressure in the range from 10,000 to 1,000,000 Pa (K2 according to the technical specifications of PJSC NK Rosneft). At the same time, the samples subjected to normalization showed mixed results, as some of the samples successfully withstood the entire test (720 hours), and some of the samples destroyed before the test was completed. A pattern is also found out that an increase in the concentration of hydrogen sulfide significantly accelerates the process of destruction of 20L steel under the same loads. On samples that destroyed before the end of the test, a study of the microstructure in the zone of destruction showed the presence of sores and microcracks (18 – 120 microns), which may indicate the course of hydrogen cracking. The results of micro-X-ray spectral analysis showed that the corrosion products in the fracture zone are iron sulfides of various compositions. When comparing the structures of the destroyed samples and the samples that survived the tests, it was found out that the destruction occurred on samples in which the size of the ferritic grain is larger, which is most likely the cause of the destruction, since all the cracks are located across the ferritic grain.
research, microstructure, analysis, heat treatment, cracking, stress
1. Ilyinsky VA, Kostyleva LV, Karpova EYu. Features of the structure and properties of cast low-carbon steels. Metal Science and Heat Treatment. 1995;5:2-4
2. V.I. Astashenko, N.N. Zapadnova, T.V. Shveeva, E.A. Zapadnova, I.N. Khalikov. Steel structure and composition requirements for low-temperature purpose improvements. Vestnik of KNRTU named after A.N. Tupolev. 2016. No. 3. pp. 54-59.
3. Ilyinsky VA, Karpova EYu, Kostyleva LV, Gabelchenko NI. Features of morphology and structure of Widmanstätten and polyhedral ferrite in low-carbon steels. Science Journal of Volgograd State University. 1:154-158.
4. Karpova EYu, Karpov YuI, Leonchenko AS. Heat treatment regimes influence on steel quality. Izvestiya. Ferrous Metallurgy. 2012;5:17-19.
5. Yevpak TF, Muravyev KA. Study of corrosion and mechanical resistance of oil equipment. Innovatsii V Nauke. 2013;17:23-36.
6. Konishchev KB, Semenov AM, Chaban AS, Lobanova NA, Kashkovsky RV. Peculiarities of the stress corrosion cracking of metal pipes in media containing hydrogen sulfide and carbon dioxide. Gas Science Bulletin. 2019;3:60-66.
7. Fang B, Eadie R, Elboujdaini M, Chen W, Han E-H. The effect of microstructure on pit-tocrack transition and crack growth in an X-52 pipeline steel in near-neutral pH environment. 7th International Pipeline Conference. 2008. p 215-225.
8. Contreras A, Salazar M, Albiter A, Galván R,Vega O. Assessment of stress corrosion cracking on pipeline steels weldments used in the petroleum industry by slow strain rate tests. Arc Welding. 2011:143-144.
9. Craig B. Research of main gas pipeline (steels X65, X60, 17G1S) susceptibility to stress corrosion cracking, hydrogen uptake and ST 37-2 steel fatigue testing. Calculating the lowest failure pressure for electric resistance welded pipe. 2018;77:61-63.
10. Yusupova EV. Sulfide-corrosion cracking under stress. Russian Student Lomonosov Readings. 2019;1:489-494.
11. Kharina GV, Vedernikov AS, Sadriev RS. Study of the corrosive behavior of 20L steel in aggressive environments. Bulletin of Udmurt University. 2014:8-12.
12. Maltseva AN. Study of the structure and properties of high-strength ferrite-bainite steels intended for high-pressure main pipelines [abstract of dissertation]. [Chelyabinsk (RF)]; 2012.
13. Sergeeva KI. The processes of forming the structure and complex properties of low-alloy high-strength tubular steel [abstract of dissertation]. [Yekaterinburg (RF)]; 2012.
14. Ueda M, Takabe H. Effect of environmental factor and microstructure on morphology of corrosion products in CO2 environments. Corrosion. Houston.TX: NACE International; 1999.
15. Dugstad A, Hemmer H, Seiestein H. Effect of steel microstructure upon corrosion rate and protective iron carbonate film formation. Corrosion. TX: NACE International; 2000.
16. Khudyakov AO. Improving the operational properties of welded joints of high-strength thick-walled straight-seam pipes of large diameter [dissertation]. [Yekaterinburg (RF)]; 2020.
