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Tubemaking (on 55th anniversary of RosNITI — the All-Russian Scientific and Research Institute of Tube Industry)
ArticleName Strength and toughness properties of steel for long-distance pipelines in the direction of tube wall thickness
ArticleAuthor I. Yu. Pyshmintsev, A. O. Struin, V. D. Kvashnin, A. V. Gervasyev, R. Kh. Petrov
ArticleAuthorData

All-Russian Scientific and Research Institute of Tube Industry — RosNITI (Chelyabinsk, Russia):

Pyshmintsev I. Yu., Dr. Eng., General director, e-mail: PyshmintsevIU@tmk-group.com
Struin A. O., Cand. Eng., Deputy Head of Department on Direction «Welded Tubes», e-mail: struin@rosniti.ru
Kvashnin V. D., Junior Researcher, e-mail: Kvashnin@rosniti.ru


Gent University (Gent, Belgium):
Gervasyev A. V., Cand. Eng., Researcher, Department of Metal Science, e-mail: GervasyevAM@sinara-group.com
Petrov R. Kh., Dr. Eng., Prof., Department of Metal Science, e-mail: Roumen.Petrov@UGent.be

Abstract

It is shown that anisotropy of strength and toughness properties is observed in the investigated ferrite-bainite steels. Maximal, average and minimal strength values are noted in T-direction, Z-direction and L-direction respectively. Three kinds of anisotropy behaviour (“saw-toothed” “serrated”, yield tooth and continuous strengthening) can be seen on deformation diagrams for small deformation degree values. It is concluded that the kind of deformation diagram does not vary and strength increases with lowering of testing temperature. Toughness anisotropy is displayed more distinctly than strength anisotropy. Impact toughness in Z-direction is significantly lower than in T- and L-directions. Brittle component in fracture of drop-weight testing samples in Z-direction is observed at room testing temperature. The conducted tests allowed to determine power capacity of splitting forming. Impact toughness in Z-direction makes less than 30 J/cm2 at the temperature –20 °C and for notch location on ½ of sample thickness. The tests for determination of static cracking resistance have shown that splitting can occur at the load about 30 % of the load required for start of cracking propagation in T-direction. The analysis of microstructure conducted both previously and in this work allow to conclude that splitting susceptibility in K65 steels is determined by combination of several parameters, and presence of stretched areas with {001}<110> orientation as well as high content of large particles of “secondary” phases can be considered as the main among these parameters.

keywords Steels, strength, impact toughness, testing, microstructure, anisotropy of properties, wall thickness, long-distance pipelines, cracking
References

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