Influence of Dehydrogenation Heat Treatment on Hydrogen Distribution in Multi-Layer Welds Of Cr-Mo-V Steel

Abe, Masamitsu; Nakatani, Mitsuyoshi; Namatame, Naomi; Terasaki, Toshio

doi:10.1007/bf03321355

Cited by 12 publications

(17 citation statements)

References 7 publications

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“…Various temperature-dependent diffusion coefficients are available in literature. These can be used to give recommendations on HRHT temperature or holding time like in [17][18][19][20] and are especially useful in numerical calculations. In this context, the necessary holding time for a given plate thickness decreases with increasing temperature.…”

Section: Background On Diffusion In Creep-resistant 9% Cr Steelsmentioning

confidence: 99%

“…As shown in Table 3, the AW diffusion coefficients (only "D IP " shown) had been approximately 4 to 7 times smaller compared with the PWHT condition. Hence, a possible risk for delayed HAC consequently increases in as-welded and hard microstructure (like martensite in weld metal or HAZ) by significantly delayed diffusion [18][19][20].…”

Section: B Influence Of Microstructure Texture On Possible Preferredmentioning

confidence: 99%

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Hydrogen diffusion in creep-resistant 9% Cr P91 multi-layer weld metal

et al. 2019

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Welded components of P91 9% Cr steel demand for careful welding fabrication with necessary post weld heat treatment (PWHT). Before the PWHT, a hydrogen removal heat treatment is necessary for avoidance of hydrogen assisted cracking (HAC). In this context, the microstructure and temperature-dependent hydrogen diffusion is important, and reliable diffusion coefficients of P91 weld metal are rare. For that reason, the diffusion behavior of P91 multi-layer weld metal was investigated for as-welded (AW) and PWHT condition by electrochemical permeation experiments at room temperature and carrier gas hot extraction (CGHE) from 100 to 400°C. Hydrogen diffusion coefficients were calculated, and the corresponding hydrogen concentration was measured. It was ascertained that both heat treatment conditions show significant differences. At room temperature the AW condition showed significant hydrogen trapping expressed by to seven times lower diffusion coefficients. A preferred diffusion direction was found in perpendicular direction expressed by high permeability. The CGHE experiments revealed lower diffusion coefficients for the AW condition up to 400°C. In this context, a hydrogen concentration of approximately 21 ml/100 g was still trapped at 100°C. For that reason, a certain HAC susceptibility of as-welded P91 weld metal cannot be excluded, and hydrogen removal should be done before PWHT.

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Section: Background On Diffusion In Creep-resistant 9% Cr Steelsmentioning

confidence: 99%

Section: B Influence Of Microstructure Texture On Possible Preferredmentioning

confidence: 99%

Hydrogen diffusion in creep-resistant 9% Cr P91 multi-layer weld metal

et al. 2019

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“…The welding method was submerged arc welding (SAW). The welding process parameters were welding current 580 A, arc voltage 32 V, welding speed 60 cm/min, the heat efficiency 0.8–0.9 [ 20 ], preheating temperature 200 °C before welding, and inter-pass temperature not more than 250 °C.…”

Section: Materials and Experimentsmentioning

confidence: 99%

“…The test process of welded joint and the results of hydrogen content detection in welded joint refer to [ 20 ]. In the hydrogen measurement test, the double V-shaped groove of 2.25Cr-1Mo-0.25V steel (SA542D Type D Class 4a) was used to welding by SAW process at practical welding condition.…”

Section: Materials and Experimentsmentioning

confidence: 99%

“…Secondly, the trap character in case of the base material changed to irreversible at decreased temperature. Abe used experimental and numerical methods to measure hydrogen diffusivity and the influence of DHT on Cr-Mo-V steel welds, they demonstrated that even at temperatures as low as 280 degrees C held over longer time periods, and there was an equivalent dehydrogenation effect as in the existing conditions [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

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Study on Hydrogen Diffusion Behavior during Welding of Heavy Plate

2020

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For the multi-layer and multi-pass welding process of the heavy plate, the hydrogen diffusion behavior was numerically simulated to study the effect of solid-state phase transition (SSPT) on the hydrogen diffusion in the thickness direction, and the influence of the residual stress-induced diffusion after SSPT. The calculation results were compared with the experimental results. The comparison shows that the distribution of hydrogen concentration in the direction of thickness was in good agreement. The position with the most severe cold cracking sensitivity was located at a 20–30 mm depth from the top surface in this article. After welding, the hydrogen concentration in this position was kept at a high level for a long time under the effect of the size-constraint effect of the heavy plate and the existence of welding residual stress gradient. In addition, the SSPT reduced the residual stress level of weld metal (WM) significantly, increased that of the heat affected zone (HAZ), and the hydrogen was redistributed under the influence of stress. In the process of phase transformation, the parameters of hydrogen diffusion property of the material changed dramatically in a short time, the hydrogen diffusion coefficient increased in order of magnitude, and the solubility decreased in order of magnitude. This directly led to the upward diffusion of hydrogen in WM, and produced a self-gathering effect. For a welded joint of heavy plate, the self-gathering effect between passes was effective in the short-range and ineffective in the long-range.

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Characterization of Hydrogen Diffusion in Offshore Steel S420G2+M Multi-layer Submerged Arc Welded Joint

Rhode

Nietzke

Mente

et al. 2022

J. of Materi Eng and Perform

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As onshore installation capacity is limited, the increase in the number of offshore wind turbines (OWT) is a major goal. In that connection, the OWTs continuously increase in size and weight and demand adequate foundations concepts like monopiles or tripods. These components are typically manufactured from welded mild steel plates with thickness up to 200 mm. The predominant welding technique is submerged arc welding (SAW). In accordance with the standards, the occurrence of hydrogen-assisted cracking is anticipated by either a minimum waiting time (MWT, before non-destructive testing of the welded joint is allowed) at ambient or a hydrogen removal heat treatment (HRHT) at elevated temperatures. The effectiveness of both can be estimated by calculation of the diffusion time, i.e., diffusion coefficients. In this study, these coefficients are obtained for the first time for a thick-walled S420G2+M offshore steel grade and its multi-layer SAW joint. The electrochemical permeation technique at ambient temperature is used for the determination of diffusion coefficients for both the base material and the weld metal. The coefficients are within a range of 10−5 to 10−4 mm2/s (whereas the weld metal had the lowest) and are used for an analytical and numerical calculation of the hydrogen diffusion and the related MWT. The results showed that long MWT can occur, which would be necessary to significantly decrease the hydrogen concentration. Weld metal diffusion coefficients at elevated temperatures were calculated from hydrogen desorption experiments by carrier gas hot extraction. They are within a range of 10−3 mm2/s and used for the characterization of a HRHT dwell-time. The analytical calculation shows the same tendency of long necessary times also at elevated temperatures. That means the necessary time is strongly influenced by the considered plate thickness and the estimation of any MWT/HRHT via diffusion coefficients should be critically discussed.

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Influence of Dehydrogenation Heat Treatment on Hydrogen Distribution in Multi-Layer Welds Of Cr-Mo-V Steel

Cited by 12 publications

References 7 publications

Hydrogen diffusion in creep-resistant 9% Cr P91 multi-layer weld metal

Hydrogen diffusion in creep-resistant 9% Cr P91 multi-layer weld metal

Study on Hydrogen Diffusion Behavior during Welding of Heavy Plate

Characterization of Hydrogen Diffusion in Offshore Steel S420G2+M Multi-layer Submerged Arc Welded Joint

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