Deformation Degree Influence of Austenitic Steels Welded Joints on Structural State and Internal Stress Fields in Weld Line Zone

• Published in: Steel in translation Vol. 51; no. 8; pp. 514 - 521
• Main Authors: Smirnov, A. N., Popova, N. A., Ababkov, N. V., Knyaz’kov, K. V., Nikonenko, E. L.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.08.2021; Springer Nature B.V
• Subjects: Arc welding; Austenitic stainless steels; Automatic control; Automatic welding; Base metal; Chemistry and Materials Science; Deformation effects; Droplets; High pressure; Materials Science; Plastic deformation; Quality assessment; Residual stress; Scientific papers; Steel; Stress distribution; Test equipment; Weld lines; Welded joints; Yield point; internal stress fields; plastic deformation; manual arc welding; existential contours; austenitic steel; modulated current welding; dislocation density; substructure
• ISSN: 0967-0912; 1935-0988
• DOI: 10.3103/S0967091221080131

Nowadays, initial assessment of welding quality is performed by testing equipment with increased loads (high pressure) at technical devices of hazardous production facilities. Test requirements are regulated by standards of the Federal Service for Environmental, Technological and Nuclear Oversight of Russia (Rostekhnadzor). Recently, along with traditional tests, a “stress test” was used—the essence of which is to load pipeline sections to the yield point, followed by leak test. However, in scientific publications, there is practically no information about physical processes occurring in the base metal and in welded joints during such tests. In addition, effect of preload (deformation) on the parameters of substructure and internal stress field in welded joints of austenitic steels and, consequently, on the further trouble-free operation of the tested equipment was not evaluated. The paper analyzes changes in the structural state and values of internal stresses in the austenitic steel samples under the action of high loads, which substantiates the use of modulated current welding with automatic control of heat input process in molten weld bath. The allowed limits of plastic deformation are substantiated when testing technical devices with high pressure for this type of steel. In order to reduce the risk of damage to austenitic steel welded joints of technical devices of hazardous industrial facilities, performed by pulsed welding with small-droplet transfer and to exclude formation of microdefects in them, high pressure tests (stress test) should be performed under loads that create deformations in metal that do not exceed 5%. For joints welded by manual arc welding, deformations should be less than 5%. Welded joints made by pulsed welding with large-droplets transfer (with and without defects) are not recommended to be tested at high pressure.