THE INFLUENCE OF THERMAL CYCLIC TREATMENT ON THE SERVICE DURABILITY OF WELDED ELEMENTS WITH SOFT INTERLAYER


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Abstract

The authors studied the influence of structural and mechanical heterogeneity of welded joints on bearing capacity characteristics of high-strength steels of K52 (09G2S and 17G1SU brands), K56 (09G2FB), K66 (10HSND) and K70 (10G2FBYU) grades. The authors identified the topography of mechanical heterogeneity of welded elements having soft interlayers in the welded seam area and (or) the near-weld area, the range of thickness ratio of which varies from 0.6 to 0.8. It is proved that the soft interlayers in the welded joints cause the reduction of strength index up to 30%, and the specific fracture work up to 50%. The influence of mechanical heterogeneity on the resistance to breakage in the result of reaction of aggressive corrosive petroleum products was estimated on the example of environmentat tests of welded elements of connection units. The study showed the corrosion velocity increase and the substantial reduction of plasticity index for the soft interlayer metal (near-weld area) in comparison with the base metal during the whole lifetime.

The significant decline of parameters of fracture toughness during the operating time, which is especially intensively manifested during the first three years of operation, was revealed. The authors estimated the influence of thermal cyclic treatment on the mechanical heterogeneity and the indicators of fracture resistance of welded elements. The quantitative assessment of the influence of thermal treatment on the survivability of welded structure elements as the ability to resist destruction in the presence of damages was fulfilled. The analysis of test results for static and cyclic crack resistance allowed to determine the limiting size of damages and residual life of welded elements, as well as to analyze their changes after the thermal treatment. The transformation of the strain-stress state nature during the thermal cyclic treatment is shown.

About the authors

Lyudmila Sergeevna Dinmukhametova

Orsk Branch of Samara State University of Railroads, Orsk

Author for correspondence.
Email: info@orsksamgups.ru

candidate of technical sciences, head of the laboratories

Россия

Ekaterina Vasilievna Poyarkova

Orenburg State University, Orenburg

Email: sopromosu@rambler.ru

candidate of technical sciences, Associate Professor, assistant professor of the department «Mechanical Engineering»

Россия

References

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