Fatigue strength improvement of box‐welded joints using low transformation temperature welding material

Ota, Akihiko; Shiga, Chiaki; Maeda, Yasuhiro; Suzuki, Naoyuki; Watanabe, Osamu; Kubo, Takahiro; Matsuoka, Kazumi; Nishijima, Satoshi

doi:10.1080/09507110009549271

Cited by 32 publications

(15 citation statements)

References 9 publications

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“…The strains caused by displacive phase transformations are manipulated to cancel the thermal contraction as welded joints cool to ambient temperature. The technological benefit of doing this is to dramatically improve the fatigue performance of the joints (Ohta et al 1999b). Therefore, it would be useful to be able to estimate not only the development of transformation texture, but also the anisotropic transformation strains caused by the biased microstructure that develops under the influence of stress.…”

Section: Introductionmentioning

confidence: 99%

Crystallographic texture of stress-affected bainite

2007

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A method is presented for calculating both the macroscopic strains and the crystallographic bias which develop when a polycrystalline sample of austenitic steel is transformed into bainite or martensite under the influence of an applied stress or a system of stresses. Any texture present in the austenite prior to transformation is taken into account, as is the detailed crystallography of the transformation. Comparisons with experimental data are encouraging. A strong correlation has been observed between the proportion of the driving force for transformation that is attributed to stress and the extent of variant selection.

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Section: Introductionmentioning

confidence: 99%

Crystallographic texture of stress-affected bainite

2007

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“…We focused our investigation on a Cr/Ni based LTT alloy (e.g., References [1,41]) that shows a conspicuous hot cracking characteristic [23]. The investigated samples were standardized MVT specimens with dimensions 100 mm × 40 mm × 10 mm.…”

Section: Materials and Mvt-testingmentioning

confidence: 99%

Solidification Cracking Assessment of LTT Filler Materials by Means of Varestraint Testing and µCT

et al. 2020

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Investigations of the weldability of metals often deal with hot cracking, as one of the most dreaded imperfections during weld fabrication. The hot cracking investigations presented in this paper were carried out as part of a study on the development of low transformation temperature (LTT) weld filler materials. These alloys allow to mitigate tensile residual stresses that usually arise during welding using conventional weld filler materials. By this means, higher fatigue strength and higher lifetimes of the weld can be achieved. However, LTT weld filler materials are for example, high-alloyed Cr/Ni steels that are susceptible to the formation of hot cracks. To assess hot cracking, we applied the standardized modified varestraint transvarestraint hot cracking test (MVT), which is well appropriate to evaluate different base or filler materials with regard to their hot cracking susceptibility. In order to consider the complete material volume for the assessment of hot cracking, we additionally applied microfocus X-ray computer tomography (µCT). It is shown that by a suitable selection of welding and MVT parameter the analysis of the complete 3D hot crack network can provide additional information with regard to the hot cracking model following Prokhorov. It is now possible to determine easy accessible substitute values (e.g., maximum crack depth) for the extent of the Brittleness Temperature Range (BTR) and the minimum critical strain P m i n .

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“…Murakawa et al reported that compressive residual stress increased as Ms decreases up to approximately 200 o C [6]. Many researchers have found not only a reduction in residual stress but also an improvement in fatigue strength [17,[19][20][21][22] and the suppression of distortions [23][24][25][26] in weldments when using LTT welding materials. By tuning the temperature so that the transformation from γ to α'-martensite occurs at a lower temperature, the volume expansion accompanied by strain can compensate thermal shrinkage that occurs with cooling after welding [14,27,28].…”

Section: Introductionmentioning

confidence: 99%

Effect of Low Transformation Temperature Welding Consumable on Microstructure, Mechanical Properties and Residual Stress in Welded Joint of A516 Carbon Steel

Choi¹,

Lee²,

Kwon³

2021

Korean J. Met. Mater.

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The microstructure, mechanical properties and residual stress of flux-cored arc welded ASTM A516-70N carbon steel using a Mn-based low-temperature transformation (LTT) welding consumable were investigated. Microstructural analysis with X-ray diffraction, an electron backscattered diffractometer and a field-emission scanning electron microscope showed that the LTT weld metal was made up of ferrite, austenite, martensite, and bainite with phase fractions 50.5%, 0.2%, 40.2% and 9.1%, respectively. The increase in hardness and the decrease in absorbed impact energy of the LTT weld metal compared with conventional consumable welds were confirmed to be due to the relatively high fraction of martensite phase in the weld metal. The welding residual stress distributions in three coupons (LTT, conventional and postweld heat-treated conventional weld) were compared by the results using instrumented indentation testing. The LTT weld coupon showed compressive residual stress distributed in the weld metal and heat-affected zone (HAZ), confirming previous studies in which this residual stress was attributed to a martensitic phase transformation at relatively low temperature. PWHT in the conventionally welded coupon considerably reduced the tensile residual stress distributed in the weld metal and HAZ. The LTT consumable, however, showed a significant advantage in welding residual stress, even compared with the heat-treated conventional consumable.

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Fatigue strength improvement of box‐welded joints using low transformation temperature welding material

Cited by 32 publications

References 9 publications

Crystallographic texture of stress-affected bainite

Crystallographic texture of stress-affected bainite

Solidification Cracking Assessment of LTT Filler Materials by Means of Varestraint Testing and µCT

Effect of Low Transformation Temperature Welding Consumable on Microstructure, Mechanical Properties and Residual Stress in Welded Joint of A516 Carbon Steel

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