Investigation into the Effect of Manufacturing Technology on the Fracture Toughness and Durability of Steam Pipes Made o
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Vol. 54, No. 4, November, 2020
INVESTIGATION INTO THE EFFECT OF MANUFACTURING TECHNOLOGY ON THE FRACTURE TOUGHNESS AND DURABILITY OF STEAM PIPES MADE OF 10Kh9MFB-Sh STEEL V. I. Gladshtein1 and A. P. Kolesova1 Translated from Élektricheskie Stantsii, No. 6, June 2020, pp. 41 – 46.
Notched sample modeling was used to demonstrate effect of technology used for manufacturing pipes from steel 10Kh9MFB-Sh (piercing-broaching or electroslag remelting) on metal fracture toughness under creep conditions of 600°C at subcritical and avalanche stages of destruction. According to the subcritical crack growth and metal fracture toughness resistance determined on the samples, the lifespan of pipes having initial defects was evaluated. Calculations were carried out for pipes of two types including a hot reheat (HRH) steam line operating under a pressure of 4.1 MPa and a main steam (MS) line operating under a pressure of 14.0 MPa. Taking into account the obtained characteristics of fracture toughness, the use of electroslag remelting technology was shown to provide a durability of about 3 times that of piercing-broaching approaches. Differences in the pressure level and wall thickness shown to result in a tenfold increase in the durability of the HRH and MS steam pipelines at 600°C justify a different cracking risk classification, which should be taken into account in conducting operational monitoring. Keywords: pipe; technology; durability; metal; creep; crack; toughness; destruction; sample; notch; opening; fracture; break; kinetics.
following the formation of cracks on the outer surface due to creep, it is extremely important to estimate the period of time to catastrophic failure. Initial cracks can occur in steam pipelines due to unregulated weld tacks, imperfect controls, and the development of permissible defects. This also becomes important due to such defects failing to meet the criteria of expert organizations, requiring power plant operators to reweld a large number of junctions. In the cases where organizations have insufficient guidelines for assessing the admissibility of such rewelds, this can itself give rise to additional defects. In order to estimate service life at the stage of crack growth, it was proposed [2] to carry out a modeling using a cylindrical sample with a notch in the case of fracture mechanism coincidence and K1 stress intensity factor (SIF) equality at the end of the crack. In this study, an attempt is also made to expand the capabilities of the computational method by distributing the results obtained on samples cut from a specific product to duplicate parts made using a similar technology. This significantly expands the ability to predict service life for a large number of products. However, in this case, it is necessary to take into account possible errors associated with the influence of a specific shape and dimensions on the actual properties of the metal. Therefore, methods
The development of high-chromium heat-resistant steel of the Russian 10Kh9MFB-Sh type (analogous to R91 steel) for the
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