Effect of welding process and groove angle on type IV cracking behaviour of weld joints of a ferritic steel

Albert, Shaju K.; Tabuchi, Masaaki; Hongo, Hiromichi; Watanabe, Takashi; Kubo, Kiyoshi; Matsui, Masanao

doi:10.1179/174329305x36034

Cited by 46 publications

(40 citation statements)

References 15 publications

(23 reference statements)

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“…[12] The linear increase in the creep rupture strength of the weld joint with preheat, as predicted by Francis et al [29] is a bit difficult to visualize, particularly for a higher preheat temperature. On the other hand, a longer creep rupture life with a narrower HAZ has been reported by Albert et al [30] and Avar et al [31] in the Cr-Mo steel weld joint. The width of the HAZ was varied, employing different fusion welding techniques having different heat inputs.…”

Section: Measures To Improve Type IV Cracking Resistancementioning

confidence: 76%

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Characterization of Microstructures across the Heat-Affected Zone of the Modified 9Cr-1Mo Weld Joint to Understand Its Role in Promoting Type IV Cracking

Laha

Chandravathi

Parameswaran

et al. 2007

Metall Mater Trans A

168

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In the postweld heat-treated (PWHT) fusion welded modified 9Cr-1Mo steel joint, a soft zone was identified at the outer edge of the heat-affected zone (HAZ) of the base metal adjacent to the deposited weld metal. Hardness and tensile tests were performed on the base metal subjected to soaking for 5 minutes at temperatures below Ac 1 to above Ac 3 and tempering at the PWHT condition. These tests indicated that the soft zone in the weld joint corresponds to the intercritical region of HAZ. Creep tests were conducted on the base metal and cross weld joint. At relatively lower stresses and higher test temperatures, the weld joint possessed lower creep rupture life than the base metal, and the difference in creep rupture life increased with the decrease in stress and increase in temperature. Preferential accumulation of creep deformation coupled with extensive creep cavitation in the intercritical region of HAZ led to the premature failure of the weld joint in the intercritical region of the HAZ, commonly known as type IV cracking. The microstructures across the HAZ of the weld joint have been characterized to understand the role of microstructure in promoting type IV cracking. Strength reduction in the intercritical HAZ of the joint resulted from the combined effects of coarsening of dislocation substructures and precipitates. Constrained deformation of the soft intercritical HAZ sandwich between relatively stronger constitutes of the joint induced creep cavitation in the soft zone resulting in premature failure.

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Section: Measures To Improve Type IV Cracking Resistancementioning

confidence: 76%

“…Several measures have been suggested to minimize the effect of type IV cracking in the weld joint of Cr-Mo steels; [26][27][28][29][30][31][32][33][34][35][36][37] these measures could be categorized as (1) heat treatment, (2) welding technique, and (3) adjustment of composition.…”

Section: Measures To Improve Type IV Cracking Resistancementioning

confidence: 99%

Characterization of Microstructures across the Heat-Affected Zone of the Modified 9Cr-1Mo Weld Joint to Understand Its Role in Promoting Type IV Cracking

Laha

Chandravathi

Parameswaran

et al. 2007

Metall Mater Trans A

168

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“…In the case of weld joint, deformation of weak FGHAZ/ICHAZ are constricted by relatively strong base metal on one side and CGHAZ on the other side during creep resulting in triaxial stress state which results in cavitation and final fracture in this zone with very little ductility. Figure 6 shows a schematic representation of type IV cracking in the creep test of ferritic steel weld joint (Albert et al 2005). Although it is difficult to avoid type IV cracking, several methods are being adopted to improve type IV cracking resistance.…”

Section: Type IV Cracking Of Ferritic Steel Weld Jointsmentioning

confidence: 99%

Materials science research for sodium cooled fast reactors

Raj

2009

Bull Mater Sci

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The paper gives an insight into basic as well as applied research being carried out at the Indira Gandhi Centre for Atomic Research for the development of advanced materials for sodium cooled fast reactors towards extending the life of reactors to nearly 100 years and the burnup of fuel to 2,00,000 MWd/t with an objective of providing fast reactor electricity at an affordable and competitive price.

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“…This is in contrast to little deformation reported in the case of type IV fracture of the other conventional ferritic steel weld-joint specimens with similar specimen geometries. [16] In order to find out the optimum boron level in the steel that gives highest rupture life for a given stress, the rupture lives of both the parent metal and the weld joint were plotted as a function of the boron content, as shown in Figure 10. For a given stress, 90 ppm B steel has the highest rupture life for the parent metal, while for weld joints, 130 ppm B steel has the best results.…”

Section: B Creep Propertiesmentioning

confidence: 99%

Improving the creep properties of 9Cr-3W-3Co-NbV steels and their weld joints by the addition of boron

Albert

Kondo

Tabuchi

et al. 2005

Metall Mater Trans A

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New ferritic steels with a controlled addition of boron have been developed recently for ultrasupercritical fossil power plants. These steels possess excellent creep resistance compared to conventional steels like P91, P92, P122, etc., and this has been attributed to the delay in coarsening of the carbides during creep owing to partial replacement of carbon by boron in these carbides. However, the susceptibility of the weld joints of the boron-containing ferritic steels to type IV cracking, which significantly brings down the rupture life of the weld joints, has not been investigated so far. In the present work, the creep properties of recently developed 9Cr-3W-3Co-NbV steels with boron contents varying from 47 to 180 ppm and of their weld joints have been studied. Creep tests were carried out at 923 K in the stress range of 140 to 80 MPa. Specimens were examined for particle coarsening using field-emission scanning electron microscopy, and the boron content in the precipitates was estimated using field-emission auger electron spectroscopy (FE-AES). The grain size of the parent metal and the heat-affected zone (HAZ) were estimated using electron backscattered pattern (EBSP) imaging. Results showed that the creep properties of the steels with 90 and 130 ppm boron and of their weld joints are superior to those of the P92 steels and its weld joints. Further, no weld joints exhibited type IV cracking. No significant coarsening of the carbides was observed, not only in the parent metal but also in the HAZ of the steels with Ն90 ppm of boron. In addition to the delay in carbide coarsening, the large prior-austenite grain size of the parent metal and the absence of a conventional fine-grained HAZ (FGHAZ) in the weld joints also seem to have a beneficial effect on improving the creep properties of these steels and their weld joints.

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Effect of welding process and groove angle on type IV cracking behaviour of weld joints of a ferritic steel

Cited by 46 publications

References 15 publications

Characterization of Microstructures across the Heat-Affected Zone of the Modified 9Cr-1Mo Weld Joint to Understand Its Role in Promoting Type IV Cracking

Characterization of Microstructures across the Heat-Affected Zone of the Modified 9Cr-1Mo Weld Joint to Understand Its Role in Promoting Type IV Cracking

Materials science research for sodium cooled fast reactors

Improving the creep properties of 9Cr-3W-3Co-NbV steels and their weld joints by the addition of boron

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