Evaluation of Long-Term Creep Strength of Welded Joints of ASME Grades 91, 92 and 122 Type Steels

Yaguchi, Masatsugu; Matsumura, Takuro; Hoshino, Katsuaki

doi:10.1115/pvp2012-78393

Cited by 23 publications

(8 citation statements)

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“…The grain structure in a PT, OT-PT, PT-PT, or CT-PT region can be varied from a completely reaustenitized refined grain structure upon peak temperatures of close to the Ac 3 temperature to a partially reaustenitized grain structure upon peak temperatures of close to the Ac 1 temperature, which is consistent with the observations from the existing literature. [15,25] The partially reaustenitized matrix, which exhibits significant microstructural heterogeneities, has been linked to the presence of HAZ failures in a recent article. [26] Further work is under way to link the observations provided here to actual longterm creep test HAZ failures in an effort to better establish the influence of the welding thermal cycle on …”

Section: Microstructural Influence On Creep Propertiesmentioning

confidence: 99%

Microstructural Characterization of the Heat-Affected Zones in Grade 92 Steel Welds: Double-Pass and Multipass Welds

West

Siefert³

et al. 2018

Metall Mater Trans A

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The microstructure in the heat-affected zone (HAZ) of multipass welds typical of those used in power plants and made from 9 wt pct chromium martensitic Grade 92 steel is complex. Therefore, there is a need for systematic microstructural investigations to define the different regions of the microstructure across the HAZ of Grade 92 steel welds manufactured using the traditional arc welding processes in order to understand possible failure mechanisms after long-term service. In this study, the microstructure in the HAZ of an as-fabricated two-pass bead-on-plate weld on a parent metal of Grade 92 steel has been systematically investigated and compared to a complex, multipass thick section weldment using an extensive range of electron and ion-microscopy-based techniques. A dilatometer has been used to apply controlled thermal cycles to simulate the microstructures in distinctly different regions in a multipass HAZ using sequential thermal cycles. A wide range of microstructural properties in the simulated materials were characterized and compared with the experimental observations from the weld HAZ. It has been found that the microstructure in the HAZ can be categorized by a combination of sequential thermal cycles experienced by the different zones within the complex weld metal, using the terminology developed for these regions based on a simpler, single-pass bead-on-plate weld, categorized as complete transformation, partial transformation, and overtempered.

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Section: Microstructural Influence On Creep Propertiesmentioning

confidence: 99%

Microstructural Characterization of the Heat-Affected Zones in Grade 92 Steel Welds: Double-Pass and Multipass Welds

West

Siefert³

et al. 2018

Metall Mater Trans A

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“…The temperature in the header component is kept at 600 • C during the whole loading procedure. Remark: In [16], the creep rupture data for compound crossweld specimens are reported. Strictly speaking, the material parameters determined based on these testing data are not exactly the material parameters of the HAZ, because the weld joints also contain the base and the weld metal regions.…”

Section: Simulation Of the Type-iv Creep Testmentioning

confidence: 94%

“…To achieve a more accurate simulation, a finer mesh has been used in the HAZ. The material parameters (related to creep strain) identified for P92 weld joints (by using the experimental results reported in [16]) are applied in the HAZ, while the material in the other part of the header component is supposed to be the general P92 steel. The loading procedure of the type-IV creep test is illustrated in Fig.…”

Section: Simulation Of the Type-iv Creep Testmentioning

confidence: 99%

“…Besides the data sources of ECCC and NIMS, the creep properties of high-Cr steels have also been reported in some other works [6,7,8,9,10,11,12]. Some recent testing results regarding the type-IV cracking in high-Cr steel weldments can be found in [10,13,14,15,16]. Besides the creep properties, the low-cycle fatigue properties of high-Cr steels have also been extensively studied.…”

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Simulation of creep and cyclic viscoplastic strains in high-Cr steel components based on a modified Becker–Hackenberg model

Wang

Steinmann

Rudolph³

et al. 2015

International Journal of Pressure Vessels and Piping

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“…MARBN exhibits not only much higher creep rupture strength of base metal than P92 but also substantially no degradation in creep rupture strength of welded joints compared with base metal, indicating no Type IV fracture. It has been reported that Gr.91, Gr.92 and Gr.122 exhibit the significant degradation in creep rupture strength of welded joints due to Type IV fracture in HAZ at temperatures above 600 o C [16]. Fig.15 Creep rupture data for base metal and welded joints of MARBN and P92 at 650 o C.…”

Section: Suppression Of Type IV Fracture In Haz Of Welded Jointsmentioning

confidence: 97%

Alloy Design of Creep- and Oxidation-Resistant 9Cr-Boron Steel Beyond Grades 91, 92 and 122

Abe

Tabuchi

Tsukamoto

et al. 2014

ASME 2014 Symposium on Elevated Temperature Application of Materials for Fossil, Nuclear, and Petrochemical Industries

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The addition of boron and nitrogen without the formation of any boron nitrides during normalizing heat treatment at high temperature improves long-term creep strength and rupture ductility of base metal and suppresses Type IV fracture in welded joints of 9Cr ferritic power plant steel at 650 o C. The enrichment of soluble boron near prior austenite grain boundaries (PAGBs) by the segregation is essential for the stabilization of fine distribution of M 23 C 6 carbides along boundaries in the vicinity of PAGBs, enhancing the boundary and subboundary hardening.9Cr-3W-3Co-VNb steel (MARBN) with 120-150 ppm boron and 60-90 ppm nitrogen, in which no boron nitride formed during normalizing, exhibits not only much higher creep strength and rupture ductility of base metal than Gr.92 but also substantially no degradation in creep strength due to Type IV fracture in welded joints at 650 o C. The formation of protective Cr 2 O 3 -rich oxide scale is achieved on the surface of MARBN by pre-oxidation treatment in argon gas, which significantly improves the oxidation resistance in steam. The present results suggest that MARBN is superior to Gr.91, Gr.92, and Gr.122 in terms of creep strength of base metal and welded joints and can be applied to boiler components in next-generation USC power plant. EXPERIMENTAL PROCEDUREThe 9Cr-3W-3Co-0.2V-0.05Nb steel with different boron concentrations of 0, 48, 92 and 139 ppm was used to investigate the effect of boron on creep strength of 9Cr boron steel base metals [2]. Nitrogen was not added to the steel to avoid the formation of BN during normalizing heat treatment at high temperature. The 9Cr-3W-3Co-0.2V-0.05Nb steel with 140 ppm boron but different nitrogen concentrations was used to investigate the effect of nitrogen on creep strength of 9Cr boron steel [3]. The steels were basically prepared by vacuum induction melting to 50 kg ingots. Hot forging and hot rolling were performed to produce plates of 20 mm in thickness. Creep tests were carried out at 650 o C for up to about 7 x 10 4 h, using specimens of 10 mm in gauge diameter and 50 mm in gauge length.The welded joints were prepared by means of multi-layered Gas Tungsten Arc (GTA) welding [4]. The simulated heataffected-zone (HAZ) specimens were also prepared. Finally, the post-weld heat-treatment (PWHT) was carried out for each specimen including the base metal at 740 o C for 4.7 h. RESULTS AND DISCUSSION Effect of boron on creep strength and microstructure1Published with permission.

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Evaluation of Long-Term Creep Strength of Welded Joints of ASME Grades 91, 92 and 122 Type Steels

Cited by 23 publications

References 0 publications

Microstructural Characterization of the Heat-Affected Zones in Grade 92 Steel Welds: Double-Pass and Multipass Welds

Microstructural Characterization of the Heat-Affected Zones in Grade 92 Steel Welds: Double-Pass and Multipass Welds

Simulation of creep and cyclic viscoplastic strains in high-Cr steel components based on a modified Becker–Hackenberg model

Alloy Design of Creep- and Oxidation-Resistant 9Cr-Boron Steel Beyond Grades 91, 92 and 122

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