Plastic Strain and Residual Stress Distributions in an AISI 304 Stainless Steel BWR Pipe Weld

Saukkonen, Tapio; Aalto, Miikka; Virkkunen, Iikka; Ehrnstén, Ulla; Hänninen, Hannu

doi:10.1002/9781118456835.ch244

“…Welds can have microstructures where definition of individual grains is ambiguous due to discontinuities in the grain boundaries, and thus clusters of multiple grains can be detected as a single grain. This has been demonstrated for stainless steel pipe welds by Saukkonen et al [37], also showing the robustness of the linear intercept method to EBSD indexing errors and the consequent grain detection. Furthermore, the circle equivalent diameter is not well suited for high aspect ratio grains by itself, and more information about the shape of the grain is required [38].…”

Section: Discussionmentioning

confidence: 82%

Characterisation of local grain size variation of welded structural steel

Lehto

¹

,

Romanoff

²

,

Remes

³

et al. 2016

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Previously, it has been shown that the grain size distribution plays an important role in the mechanical properties of welded steel. In the previous investigation, the volume-weighted average grain size has been shown to capture the influence of grain size distribution, resulting in a better fitting Hall-Petch relationship between grain size and hardness. However, the previous studies exclude the effects arising from local variation in grain size. In this paper, the grain size measurement methods are extended for the characterisation of the local grain size variation, which is significant for welded joints and can have an adverse effect on mechanical properties. The local gradient of grain size variation and its dependency on measurement direction are considered. In addition, examples of grain size and hardness variation are shown for S355 base metal and two weld metals, and characteristic differences are highlighted and discussed. The coarse-grained areas of a heterogeneous microstructure are found to have lower hardness than fine-grained areas. However, the surrounding microstructure, i.e. local grain size gradient, has an influence on the measured hardness values.

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“…Šavovi mogu imati mikrostrukturu gde je dvosmisleno definisano pojedino zrno zbog diskontinuiteta u granicama zrna tako da klaster više zrna može biti prepoznat kao zrno. To je demonstrirano na zavarenim spojevima čeličnih cevi po Saukkonen i dr. [37], takođe pokazuje robusnost metode linearnog preklapanja na EBSD indeksiranje grešaka i posledično otkrivanje zrna. Osim toga, krug ekvivalentnog prečnika nije dobro prilagođen za visoki aspekt zrna po sebi, a potrebno je i više informacija o obliku zrna [38].…”

Section: Diskusijaunclassified

Characterisation of local grain size variation of welded structural steel

Lehto¹,

Romanoff²,

Remes³

et al. 2016

Zavarivanje i zavarene konstrukcije

0

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Previously, it has been shown that the grain size distribution plays an important role in the mechanical properties of welded steel. In the previous investigation, the volume-weighted average grain size has been shown to capture the influence of grain size distribution, resulting in a better fitting Hall-Petch relationship between grain size and hardness. However, the previous studies exclude the effects arising from local variation in grain size. In this paper, the grain size measurement methods are extended for the characterisation of the local grain size variation, which is significant for welded joints and can have an adverse effect on mechanical properties. The local gradient of grain size variation and its dependency on measurement direction are considered. In addition, examples of grain size and hardness variation are shown for S355 base metal and two weld metals, and characteristic differences are highlighted and discussed. The coarse-grained areas of a heterogeneous microstructure are found to have lower hardness than fine-grained areas. However, the surrounding microstructure, i.e. local grain size gradient, has an influence on the measured hardness values. RezimeRanije je pokazano da distribucija veličine zrna igra važnu ulogu vezanu za mehanička svojstva zavarenog čelika. U prethodnom istraživanju, zapreminski procenjena prosečna veličina zrna je pokazala uticaj distribucije veličine zrna, što je rezultovalo u boljem ispunjenju Hall-Petch-og odnosa između veličine zrna i tvrdoće. Međutim, prethodne studije isključuju učinke koji proizlaze iz lokalnih varijacija u veličini zrna. U ovom radu, metode merenja veličine zrna su proširene na karakterizaciju varijacije lokalne veličine zrna, što je značajno za zavarene spojeve jer mogu imati negativan uticaj na mehanička svojstva. Razmatraju se lokalni gradijent varijacije veličine zrna i njegova zavisnost od smera merenja. Osim toga, primeri veličine zrna i varijacije tvrdoće su prikazani za S355 kao osnovni materijal i dva šava metala, a karakteristične razlike su istaknute i o njima se diskutuje. Za područja krupnozrne heterogene mikrostrukture utvrđeno je da imaju manju tvrdoću od sitnozrnog područja. Međutim, okružujuća mikrostruktura, t.j. gradijent lokalne veličine zrna, ima uticaj na izmerene vrednosti tvrdoće.

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“…According to the research results obtained for thick structures, compressive stress can be generated in an area adjacent to a repair weld [9]. Saukkonen et al [23] researched the residual stress distribution in the weld cross-section by a contour method, and the residual stress distribution is used to evaluate the EAC susceptibility of various areas of the pipe weld. Hicks et al [24] evaluated the residual stresses induced by repairs to small diameter stainless steel pipe welds.…”

Section: Introductionmentioning

confidence: 99%

Introducing Compressive Residual Stresses into a Stainless-Steel T-Pipe Joint by an Overlay Weld

Chu

¹

,

Kong

²

,

Tan

³

2021

Metals

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Microcracks are always present in the deposited metal of nickel-based alloys and austenitic stainless steels, which affects the safety of the pressure pipes. If compressive stress can be introduced into the cracked position by overlay welding, the time required with ordinary gouging repair welding technology will be significantly reduced, which is practical significance for pressure pipes repair welding. In this work, a stainless-steel T-pipe joint was fabricated using manual metal arc welding with an ER316L wire, and an overlay weld was fabricated using tungsten inert gas arc welding with an ERNiCrFe-7A wire. The overlay thickness was about 10 mm. The contour method was employed to measure the residual stress in the T-pipe joint. The results show that compressive residual stress about 50 MPa is formed in the original ER316L weld, which proves that the residual compressive stress can be obtained in the original weld by surfacing 10 mm thick nickel base alloy on the original weld surface.

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Plastic Strain and Residual Stress Distributions in an AISI 304 Stainless Steel BWR Pipe Weld

Cited by 5 publications

References 15 publications

Characterisation of local grain size variation of welded structural steel

Characterisation of local grain size variation of welded structural steel

Characterisation of local grain size variation of welded structural steel

Introducing Compressive Residual Stresses into a Stainless-Steel T-Pipe Joint by an Overlay Weld

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