Structure and properties of 17G1S-U low-carbon pipe steel microalloyed by boron

The results of analysis of the influence of boron microalloying on structure and properties of 17G1S-U pipe steel are given in the paper. Studies of metal structure were performed by electron microscopy and local X-ray spectral analysis. It has been established that metal containing 0.006 % of boron is characterized by an increased volume concentration to 0.029 % of oxide (OS) and oxysulfide (OSB) inclusions, whose content in metal without boron reaches 0.006 %. Separate sulphide inclusions (CB), whose concentration does not exceed 0.004 % against 0.029 % in a metal without boron, containing 0.01 % S is practically absent in the metal with boron containing 0.003 % S. The microalloying of pipe steel by boron has ensured the preferential formation of small nonmetallic inclusions, evenly distributed in the volume of metal. The proportion of nonmetallic inclusions with size less than 2 (rm is 76.1 %, whereas in steel without boron it is only 58.5 %. In this case, large nonmetallic inclusions of more than 10 rm are practically absent in the sample with boron. Their share does not exceed 0.6 %, which is 22 times less than their amount in the sample without boron. The structure of the sample without boron consists mainly of ferrite and a small amount of perlite, and the sample with boron is represented by a dispersed ferritic-bainitic structure. Increasing the microhardness of both ferrite and pearlite 80 and 100 HV10, respectively, is observed by adding boron to steel. The mechanical properties of 10 mm hot rolled metal from boron-containing 17G1S-U pipe steel are characterized by increased strength properties with preservation of plastic characteristics, due to the formation of predominantly small nonmetallic inclusions and a finely dispersed ferritic-bainitic structure. The absolute values of the yield stress and the time resistance of pipe steel containing in mass %: 0.006 B and 0.003 S are achieved without heat treatment at 585 and 685 MPa, respectively, and meet the X80 strength class, while retaining sufficiently high plastic characteristics. The pipe steel without boron containing 0.01 % of S belongs to the X70 strength class and is characterized by tensile strength lowered to 540 and 610 MPa and a temporary resistance, respectively.

1. Uglov V.A., Zaitsev A.N. Main directions of development of metallurgical technology to ensure modern requirements for the level and stability of service characteristics of steel. Chernaya metallur-giya. Byul. in-ta “Chermetinformatsiya”. 2012, no. 3, pp. 85-93. (In Russ.).

2. Shakhpazov E.Kh., Zaitsev A.I., Rodionova I.G. Current problems in the steel metallurgy and materiology. Metallurgist. 2009, vol. 53, no. 3-4, pp. 187-195.

3. Arabei A.B. Development of technical specifications for pipe-line steels. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 2010, no. 7, pp. 3-10. (In Russ.).

4. Dyudkin D.A., Kisilenko V.V. Proizvodstvo stali. T. 3. Vnepechnaya metallurgiya stali [Steel production. 3. Out-of-furnace steel metallurgy]. Moscow: Teplotekhnik, 2010, 544 p. (In Russ.).

5. Chumakov S.M., Lamukhin A.M., Zinchenko S.D. etc. The concept of production of low-sulfur steels at Severstal OJSC, taking into account its technological aspects. In: Trudy VI kongressa staleplavil’shchikov [Proc. of the 6th Congress of Steel Makers]. Moscow: AO “Chermetinformatsiya”, 2001, pp. 63-66. (In Russ.).

6. Sokolov G.A. Vnepechnoe rafinirovanie stali [Out-of-furnace steel refining]. Moscow: Metallurgiya, 1977, 208 p. (In Russ.).

7. Nurhudin, Maulud Hidagat, Windu Basuki. Deep desulfurization process for producing ultra low sulfur steel at PT Krakatau Steel. SEA&S& Quarterly. 2004, vol. 33, no. 2, pp. 29-34.

8. Golubtsov V.A., Lunev V.V. Modifitsirovanie stali dlya otlivok i slitkov [Modification of steel for castings and ingots]. Chelyabinsk - Zaporizhia: ZNTU, 2009, 356 p. (In Russ.).

9. Pilyushenko V.L., Vikhleshchuk V.A. Nauchnye i tekhnologicheskie osnovy mikrolegirovaniya stali [Scientific and technological basis of steel microalloying]. Moscow: Metallurgiya, 2000, 384 p. (In Russ.).

10. Lyakishev N.P., Pliner Yu.L., Lappo S.I. Borsoderzhashchie stali i splavy [Boron-containing steels and alloys]. Moscow: Metallurgiya, 1986, 191 p. (In Russ.).

11. Sofrygina O.A., Zhukova S.Yu., Bityukov S.M., Pyshmintsev I.Yu. Development of HSLA-steels for production of high-strenth oil country tubular goods of API Spec5CT. IzvestiyaVUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 2010, no. 7, pp. 43-49. (In Russ.).

12. Babenko A.A., Zhuchkov V.I., Smirnov L.A., Sychev A.V., Ak-berdin A.A., Kim A.S., Vitushchenko M.F., Dobromilov A.A. Production technology for low-carbon, low-sulfur boron steel. Steel in Translation. 2015, vol. 45, no. 11, pp. 883-886.

13. Machikin V.I., Manyak N.A., Manyak L.K., Melakh A.G., Akulov V.V., Volkova V.V. Boron and non-metallic inclusions in low-alloy steel. Metallurgicheskaya i gornorudnaya promyshlennost’. 1986, no. 3, pp. 15-16. (In Russ.).

14. Heckmann C.J., Ormston D., Grimpe F., Hillenbrand H.-G., Jansen J.-P. Development of low carbon Nb-Ti-B microalloyed steels for high strength large diameter linepipe. Ironmaking and Steelmaking. 2005, vol. 32, no. 4, pp. 337-341.

15. Vangaru Narasimha-Rao V., Koo Jayoung, Luton Michael J., etc. Ultra-high strength, weldable, boron-containing steels with superior toughness. Patent 6228183 US. Publ. 08.05.2001.

16. Asakhi Kh., Khaara T., Tzuru E., etc. Razrabotka ul’travysoko-prochnykh trub X120 UEO [Development of ultra-high-strength X120 UEO pipes]. In:Mezhdunarodnyiseminar "Sovremennyestali dlya gazonefteprovodnykh trub, problemy i perspektivy”: sb. dokla-dov [Int. seminar “Modern steels for gas and oil pipes, problems and prospects”: Coll. of papers]. Moscow: Metallurgizdat, 2006, pp. 123-130. (In Russ.).

17. Tekhnologicheskaya instruktsiya TISK-01-2007 "Vyplavka stali v kislorodnykh konverterakh” [TI SK-01-2007 technological instruction “Steel melting in oxygen converters”]. Temirtau: AO “Arselor-Mittal Temirtau”, 2007. (In Russ.).

18. Tekhnologicheskaya instruktsiya TISK-07-2007 "Vnepechnaya ob-rabotka stali dlya slyabovykh MNLZ” [TI SK-07-2007 technological instruction “Out-of-furnace processing of steel for slab CCM”]. Temirtau: AO “ArselorMittal Temirtau”, 2007. (In Russ.).

19. Babenko A.A., Zhuchkov V.I., Selivanov E.N., Sychev A.V., Zo-lin A.N., Dobromilov A.A., Kutdusova Kh. Sh., Savrasov A.I., Kim A.S., Akberdin A.A. Shlakovaya smes’dlya obrabotki stali v kovshe [Slag mixture for steel processing in a ladle]. Patent no. 2562849 RF. Byulleten' izobretenii. 2004, no. 25. (In Russ.).

20. Babenko A.A., Zhuchkov V.I., Selivanov E.N., Sychev A.V. Shlakovaya smes’ dlya obrabotki stali v kovshe [Slag mixture for steel processing in a ladle]. Patent no. 30964 RK. 2016. (In Russ.).

21. Zaitsev A.I., Kraposhin V.S., Rodionova I.G., etc. Kompleksnye nemetallicheskie vklyucheniya i svoistva stali [Complex non-metallic inclusions and properties of steel]. Moscow: Metallurgizdat, 2015, 276 p. (In Russ.).