Creep properties of 12% Cr and improved 9% Cr weldments

deWitte, Mark; Coussement, Carine

doi:10.1080/09603409.1991.11689658

Cited by 28 publications

(4 citation statements)

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“…The HAZ area which governs the creep failure has already been identified. 4) A fracture mechanism map has been proposed, 4) where the evolution of damage mechanism in weldments from intragranular to intergranular fracture is represented. These results are to be confirmed by the present study.…”

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High Temperature Creep Flow and Damage Properties of the Weakest Area of 9Cr1Mo-NbV Martensitic Steel Weldments

2005

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In the present study, creep flow and damage behaviour of modified P91 steel weldments are investigated. Premature creep failure of weldments (with respect to base metal) occurs in the intercritical heat affected zone (ICHAZ). This microstructure is reproduced by thermal simulation applied to blanks cut from the base metal. Metallurgical investigations of what happens during the welding cycle show that the weakest part of the heat affected zone is heated slightly below complete austenitisation, with little (if any) carbide dissolution. During the post-weld heat treatment, extensive recovery is allowed by carbide coarsening. The intrinsic creep behaviour of the resulting microstructure is experimentally determined under controlled constraint conditions. The welding cycle strongly decreases the creep strength by increasing the creep strain rate, but not necessarily by decreasing the ductility, at least for lifetimes up to 3 500 h.KEY WORDS: 9Cr1Mo-NbV martensitic steel; intercritical heat affected zone; Gleeble 1 500 thermalmechanical simulator; High temperature creep flow and damage.in the microstructure of interest was not known, just as for cross-weld specimens. The key point of the present study is thus to determine the properties of the weakest HAZ while eliminating, as much as possible, the constraint effects due to the surrounding materials. Material and Experimental Procedures MaterialsThe study focuses on a V-shaped, circumferentially welded joint of two pipes of 295 mm in outer diameter and 55 mm in thickness. It was fabricated by submerged metal arc welding in seventeen runs followed by a post weld heat treatment (PWHT) of 2 h at 760°C. The base metal is a tempered, modified P91 martensitic steel (see Table 1 for chemical composition). Its microstructure consists of lath martensite packets with M 23 C 6 (100 nm in mean size) and MX precipitates. The filler metal has nearly the same chemical composition as the base metal (Table 1). Simulation of Welding Thermal CyclesWelding thermal cycles were applied by using a Gleeble 1 500 thermal-mechanical simulator capable of heating specimens by Joule effect at very high heating rates, corresponding to those encountered in welding conditions (i.e. 100 to 250°C · s Ϫ1). The temperature is controlled by a thermocouple spot welded onto the specimen surface. Round bars of 5 mm in diameter were used to optimise the thermal cycle and 12 mm round blanks were treated and used to machine mechanical testing specimens respectively. For each of these two geometries, the closed-loop parameters of the Gleeble 1 500 simulator were carefully adjusted in order to ensure an uncertainty lower than 2°C for the value of T peak and smaller than 1 s for the value of the cooling parameter Dt 800→500 . For specimens of 5 mm in diameter, phase transformations were continuously monitored using in-situ dilatometric measurement of the specimen diameter. To prevent from extensive oxidation of the specimen, heat treatments were performed under primary vacuum (0.1 Pa). Phase transformations moni...

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“…Similar observations are reported in the temperature range 575-650°C. 4,29,46) Therefore, it is assumed that the thermal cycle corresponding to the weakest HAZ is characterised by a peak temperature: 885°CϽT peak Ͻ1 060°C (i.e. in the intercritical domain).…”

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High Temperature Creep Flow and Damage Properties of the Weakest Area of 9Cr1Mo-NbV Martensitic Steel Weldments

2005

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“…Half-tempered weld joint has reported a superior creep strength than conventional weld joint for short-term creep test [16]. The half-tempering technique utilized the partial tempering of base metal before the welding and completes the tempering as PWHT.…”

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Study on microstructure characterization of fracture frontier of post welds heat treatment and type IV cracking of P92 steel welded joint

Pal¹,

Singh²

2022

UJMEMS

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In the research work presented in this study microstructure evolution at fracture frontier of crept P92 weld, creep rupture life and effect of creep exposure time on microstructure evolution in fine-grained heat affected zone were performed. Microstructure evolution and creep rupture behavior of metal arc welded joint of P92 steel plate in the as-welded have been studied. The different states of post weld heat treatment (PWHT). (i). post welded heat treatment at 760 o C for the 2h (ii). re-austenitizing at 1040 o C for 60 min and air cooled and tempering at 760 o C for 2h. In PWHT condition, most common type IV cracking was observed creep exposure 620 o C / 150 MPa. The martensitic matrix fracture is also observed in PWNT 1 condition. A move away from the fracture frontier, the cavities still remain in the microstructure while the martensitic matrix fracture is difficult to observe. The line mapping also confirmed the increase in weight percentage of Cr and Mo in M 23 C 6 . The elemental mapping of PWHT 2 condition is also carried out in FGHAZ which confirm the formation of Mo and Cr-rich M 23 C 6 precipitates.

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“…It plays an important roll in ferritic steel especially in combination with molybdenum to improve its temper resistance and solid solution strengthening [6]. Considering the wide ranged applications of this steel, the properties like creep behavior, welding-characteristics, micrographic-heterogeneities, high temperature oxidation, electrochemical studies and fatigue behavior are investigated [7][8][9][10][11]. However, the effects of recrystallization-annealing in cold rolled condition associated with large strain energy due to high defect concentration (high dislocation density) are rarely studied.…”

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Recrystallization Annealing of Cold Rolled 9Cr 1Mo Ferritic Steel Containing Silicon

Mungole

Surender

Balasubramaniam

et al. 2009

DDF

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9Cr-1Mo ferritic steel samples containing 0.2 and 0.5 wt % silicon in 40 % cold rolled state were recrystallize-annealed at 1100, 1200 and 1300 K. The grain growth and mechanical properties after recrystallization-annealing for 20 hr to 100 hr were investigated. No significant grain growth was observed even after 100 hr annealing at 1100 and 1200 K. The recrystallization-annealing at 1200 K resulted grains smaller in size than those at 1100 K. Annealing at 1300 K exhibited the enhanced grain growth with decorative microstructures. Initial annealing after cold rolling at 1100 K exhibited low hardness which further increased with annealing temperature. Annealing at 1100 K for 20 hrs exhibited low yield strength and ultimate tensile strength compared to those of as received samples. However, for 100 hrs annealing these properties remained nearly constant for 0.2 Si composition and increased marginally for 0.5 Si composition. Recrystallization-annealing exhibited improved ductility for both the compositions.

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Creep properties of 12% Cr and improved 9% Cr weldments

Cited by 28 publications

References 1 publication

High Temperature Creep Flow and Damage Properties of the Weakest Area of 9Cr1Mo-NbV Martensitic Steel Weldments

High Temperature Creep Flow and Damage Properties of the Weakest Area of 9Cr1Mo-NbV Martensitic Steel Weldments

Study on microstructure characterization of fracture frontier of post welds heat treatment and type IV cracking of P92 steel welded joint

Recrystallization Annealing of Cold Rolled 9Cr 1Mo Ferritic Steel Containing Silicon

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