Asymptotic creep deformation behavior of modified HP steel after long-term service

Yu, Jong Min; Dao, Van Hung; Lok, Vanno; Le, Thi Giang; Yoon, Kee Bong

doi:10.1007/s12206-020-0421-z

Cited by 6 publications

(5 citation statements)

References 25 publications

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“…The total creep strain rate (

\overset{ε}{true}

) is assumed to be equal to the SC strain rate (

{\dot{ε}}_{SC}

). The minimum creep strain rate (

{\dot{ε}}_{m}

) as a function of applied stress ( σ ) was described by Norton's power‐law creep constitutive equation, as expressed in Equation (1):

\overset{ε}{true} goodbreak= {\dot{ε}}_{SC} goodbreak= {\dot{ε}}_{m} goodbreak= A σ^{n}

where

A

and

n

are the SC coefficient and SC exponent, respectively 24 …”

Section: Methodsmentioning

confidence: 99%

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Creep life estimation of a service‐exposed P91 cross‐weld joint based on a primary‐secondary creep deformation model

Lok

Yoon

2022

Fatigue Fract Eng Mat Struct

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Creep deformation and rupture behavior of welded joints from service‐exposed P91 steel were investigated by creep tests and microstructure examination. A series of miniature tensile creep tests were conducted at 569°C under applied stresses ranging from 182.5 to 286 MPa for the heat‐affected zone (HAZ), base metal, and weld metal. Creep deformation behavior was modeled using the experimentally measured creep strain data as the primary creep‐secondary creep (PC‐SC) model and fitting closely with the measured creep curves of each metal. Power‐law type creep equations were employed to describe the primary and secondary creep behavior. The creep rupture life of the cross‐weld specimen was predicted using the PC‐SC model with HAZ properties. An accurate prediction was possible if the stress in estimation was increased to 1.14 times of the actual applied stress. The creep test results with the cross‐weld specimens were used for verification. Applying the Monkman–Grant relationship and the creep damage tolerance factors to the cross‐weld joint life prediction are also discussed.

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“…The total creep strain rate (

\overset{ε}{true}

) is assumed to be equal to the SC strain rate (

{\dot{ε}}_{SC}

). The minimum creep strain rate (

{\dot{ε}}_{m}

) as a function of applied stress ( σ ) was described by Norton's power‐law creep constitutive equation, as expressed in Equation (1):

\overset{ε}{true} goodbreak= {\dot{ε}}_{SC} goodbreak= {\dot{ε}}_{m} goodbreak= A σ^{n}

where

A

and

n

are the SC coefficient and SC exponent, respectively 24 …”

Section: Methodsmentioning

confidence: 99%

“…where A and n are the SC coefficient and SC exponent, respectively. 24 In the combined PC-SC model, the contribution of the PC strain rate was considered, which was neglected in the SC creep model. The total creep strain rate was a summation of the PC strain rate and secondary one as depicted in Equation (2).…”

Section: Creep Deformation Modelingmentioning

confidence: 99%

Creep life estimation of a service‐exposed P91 cross‐weld joint based on a primary‐secondary creep deformation model

Lok

Yoon

2022

Fatigue Fract Eng Mat Struct

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“…The detailed steps using ImageJ software to quantitatively analyze the precipitates were in line with a previously reported method [16,17]. The area fraction of the precipitate is defined as the area ratio of the precipitates to the image [3]. The mean precipitate size was determined by applying the ImageJ software to measure the areas of the precipitates in the OM images, following which the precipitate areas were converted to equivalent radii [18][19][20][21].…”

Section: Methodsmentioning

confidence: 99%

“…4, the OM images are converted to the corresponding precipitate morphologies such that the precipitate regions can be simply distinguished. It is seen that the precipitate morphologies at the grain boundaries and within the austenitic matrix can be accurately characterized by image analysis [3]. The measured area fractions of the precipitates are given in Table 3.…”

Section: Relationship Between Area Fraction Of Precipitate and Service Periodmentioning

confidence: 99%

“…Austenitic heat-resistant steel, HP40Nb, is one of the types of high-temperature steels that are used to fabricate steam reforming tubes in process plants to produce hydrogen-rich gases from mixtures of hydrocarbons and steam at high temperatures [1][2][3]. The HP40Nb steel is a modified version of the HK40 type, with added niobium and titanium to ensure good creep resistance and mechanical properties at high temperatures in the range of 900-1050 °C [3]. The normal designed life of a reformer tube based on the API standard is 100000 h [4,5].…”

Section: Introductionmentioning

confidence: 99%

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Quantitative study on area fraction of precipitated carbides of HP40Nb steel as a function of service period

Bang

Kim

et al. 2021

J Mech Sci Technol

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Life assessment predictions of reformer tubes of HP40Nb grade steel used in the petrochemical industry were investigated by quantitative metallographic evaluations of the area fractions of precipitated carbides. Correlations were established between the field-service periods and area fractions of the carbides via microstructural analysis. The microstructures of the virgin and other tubes were examined using optical microscopy (OM) for service periods of 1.8, 6.0, 7.2, 8.5, 9.7, and 16.2 years at 950 °C. The area fractions of the precipitates were measured by image analysis using ImageJ software. The results showed that increase in the area fractions of the precipitates was almost proportional to increase their service times. The relationships between area fractions of the precipitates and service times were also discussed for a 6-year cracked tube and a tube that had been in service for 11.5 years at another furnace. The obtained relationship can thus be used via the surface replication method for on-site residual life assessments.

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Changes in creep property and precipitates due to aging of T91 steel after long-term service

Lok

et al. 2020

J Mech Sci Technol

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Asymptotic creep deformation behavior of modified HP steel after long-term service

Cited by 6 publications

References 25 publications

Creep life estimation of a service‐exposed P91 cross‐weld joint based on a primary‐secondary creep deformation model

Creep life estimation of a service‐exposed P91 cross‐weld joint based on a primary‐secondary creep deformation model

Quantitative study on area fraction of precipitated carbides of HP40Nb steel as a function of service period

Changes in creep property and precipitates due to aging of T91 steel after long-term service

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