<i>In situ</i> analysis of the strain evolution during welding using low transformation temperature filler materials

Dixneit, Jonny; Vollert, Florian; Kromm, Arne; Gibmeier, Jens; Hannemann, Andreas; Fischer, Torben; Kannengießer, Thomas

doi:10.1080/13621718.2018.1525150

Cited by 9 publications

(6 citation statements)

References 33 publications

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“…The latter approach requires careful control of the LTT alloy chemistry to lower the upper critical temperature (temperature above which the microstructure is 100% FCC) so that the austenitic transformation always occurs during subsequent passes. Like the M s temperature, the upper critical temperature also strongly depends on the alloying additions and is particularly sensitive to the Cr, Ni and C content of the filler material [8,12,13].…”

Section: Introductionmentioning

confidence: 99%

“…However, these techniques do not provide any insights into the mechanism of stress formation during welding and cooling [5], which requires in situ measurements. In situ monitoring techniques such as synchrotron x-ray diffraction [12,13], digital image correlation [14][15][16] and infrared (IR) thermography cameras [17] are commonly used. However, these techniques are not widely available and require extensive post-processing steps.…”

Section: Introductionmentioning

confidence: 99%

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In situ measurement of phase transformations and residual stress evolution during welding using spatially distributed fiber-optic strain sensors*

Petrie

2020

Meas. Sci. Technol.

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Welding of high-strength steels can result in large tensile strains as the base metal and filler material cool from their molten state. To combat these large tensile strains, low-transformation-temperature (LTT) metal fillers have been proposed. These fillers undergo a martensitic phase transformation at a lower temperature which can ultimately reduce the tensile strain or can even introduce compressive strain adjacent to the weld metal. However, the process for optimizing the composition of the LTT material, as well as various weld parameters for each unique weld geometry, can be quite expensive, especially if the acceptance criterion requires using neutrons, x-ray beams, or destructive techniques to characterize residual stresses. This work describes a simple, low-cost method for quantifying residual stresses and phase transformations in situ during welding. Spatially distributed fiber-optic sensors were bonded to a cast iron plate, along with tack-welded thermocouples, to measure temperature and strain during multiple passes with LTT filler metals. Results show that the fiber-optic sensors can successfully resolve compressive strain adjacent to the weld region caused by the martensitic phase transformations in the LTT filler material.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In situ measurement of phase transformations and residual stress evolution during welding using spatially distributed fiber-optic strain sensors*

Petrie

2020

Meas. Sci. Technol.

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“…The volume expansion during martensite formation is more pronounced at lower temperatures due to the higher coefficient of thermal expansion (CTE) for austenite compared to martensite. In-situ analysis using high-energy synchrotron X-ray diffraction during a realistic Metal Active Gas (MAG) welding process showed a significantly higher decrease of residual strain due to the hindered volume expansion for a LTT weld filler material compared to a conventional weld filler material [20,21]. The subsequent residual stress analysis using the contour method, which gives an entire two-dimensional residual stress map, revealed a higher compressive residual stress level for the investigated LTT filler materials compared to a conventional weld filler material [22].…”

Section: Introductionmentioning

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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“…The volume expansion during martensite formation is more pronounced at lower temperatures due to the higher coefficient of thermal expansion (CTE) for austenite compared to martensite. In-situ analysis using high energy synchrotron X-ray diffraction during realistic MAG welding showed a significantly higher decrease of residual strain due to the hindered volume expansion for an LTT weld filler material compared to a conventional weld filler material [3,4]. The subsequent residual stress analysis using the contour method, which gives an entire two-dimensional residual stress map normal to the cut face through the component, revealed a higher compressive residual stress level for the investigated LTT filler materials compared to a conventional weld filler material [5].…”

Section: Introductionmentioning

confidence: 99%

Hot crack assessment of LTT welds using μCT

Vollert¹,

Thomas²,

Kromm³

et al. 2020

eJNDT

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Investigations on weldability often deal with hot cracking, as one of the most popular failure during weld fabrication. The modified varestraint transvarestraint hot cracking test (MVT) is well known for the assessment of the hot cracking susceptibility of materials [1, 2]. The shortcoming of this approach is that the information is only from the very near surface region, which inhibits access to the characteristic of the hot crack network in the bulk. Here, we report about a new approach, illustrated in the example of low transformation temperature (LTT) weld filler materials, to monitor the entire 3D hot crack network after welding by means of microfocus X-ray computer tomography (?CT).

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In situ analysis of the strain evolution during welding using low transformation temperature filler materials

Abstract: In-situ analysis of the strain evolution during welding using low transformation temperature filler materials Short Title: In-situ analysis of the strain evolution during welding using low transformation temperature filler materials Article Type: Research Article

Cited by 9 publications

References 33 publications

In situ measurement of phase transformations and residual stress evolution during welding using spatially distributed fiber-optic strain sensors*

In situ measurement of phase transformations and residual stress evolution during welding using spatially distributed fiber-optic strain sensors*

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

Hot crack assessment of LTT welds using μCT

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