Modified 9Cr-Mo steel is a candidate structural steel for demonstration fast breeder reactors (FBR's). Due to low thermal activatio n, the steel can maintain steady-state deformation during long-term creep. The creep strength of its weldment is lower than that of the base metal. Because of different creep strain rate in the solidified weld metal and heat-affected zone (HAZ), creep deformation in HAZ can be lowered but maximum principal stress augmented in fine-grained HAZ to cause detrimental Type IV crack...
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FEM Analyses of Creep in Welded Modified 9Cr -1 Mo Steel Considering Constraint Effects Induced by Anisotropic Microstructures

The present study has investigated plasticity-induced martensitic phase transformation in fatigue of unnotched SUS304 plates. Martensitic phase transformation occurred in uunotched SUS304 plate specimens fatigued at room temperature in air. Volume fraction Va of a'martensite in the uunotched potion of fatigued s pecimens was measured by ferrite scope. The relations between the maximum value of Vas Va’max, and the number of load cycles N were represented by reverse sigmoidal curves for all the applied stres...
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Evolution of Volume Fraction of Plasticity-Induced Martensitic Phase during Fatigue Process of SUS304 Stainless Steel at Room Temperature in Air

The present paper proposes new creep life prediction methods that can be used in situ as an in-service inspection tool for the condition based monitoring of high-temperature structure components of 316FR stainless steel. The methods are based on two types of the modified theta methods and the combination of the modified and omega methods are applied to creep deformation data measured in the creep tests made at different applied stress levels at 823-923 K in air. Creep lives were predicted by the propos...
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In Situ Creep Life Prediction Methods for Austenitic Stainless Steel 316FR

The present study investigates plasticity-induced martensitic transformation around fatigue cracks in single V-groove butt-welded SUS304 plates at room temperature in air. Distributions of a' phase volume fraction Va around fatigue cracks were measured with ferrit e scope. The results were compared with the distributions of vertical magnetic flux density B, above fatigue cracks in welded specimens magnetized by a strong electromagnet. It was revealed that the B, distributions reflected the spatial distribu...
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Non-Destructive Evaluation of Fatigue Cracks in SUS304 Stainless Steel Weldment by Using Plasticity-Induced Martensitic Transformation

This paper describes a collaborative study on degradation and damage of structural materials and the detection and evaluation methods of degradation and damage in structural components in the course o f the activities of the research committee on the Detection and Evaluation Methods of Degradation and Damage in Structural Materials. The research committee has been established in the Japan Society o f Maintenology since April, 2004 and has attempted to clarify the damage and/or degradation mechanisms caused...
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Degradation and Damage of Structural Materials: Methods of Evaluation andPossibility of Their Applications to the Condition-Based Maintenance

This paper describes shot peening treatment of modified 9Cr steel and 316FR austenitic stainless steel, candidate structural materials for FBR by using YAG laser. A laser peening system has been developed and used to provide laser peening treatment for plate s pecimens of the two types of the steels dipped in water. A high speed digital camera revealed that many small bubbles were initiated along the path of laser light, moved along the path and coalesced with one another to produce a few large bubbles. Th...
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Laser Peening Treatment of modified 9Cr and 316FR Steels

Modified 9Cr-Mo steel is a candidate structural steel for demonstration fast breeder reactors (FBR's). Due to low thermal activation, the steel can maintain steady-state deformation during long-term creep. The creep strength of its weldment is lower than that of the base metal. Because of different creep strain rate in the solidified weld metal and heat-affected zone (HAZ), creep deformation in HAZ can be lowered but maximum principal stress augmented in fine-grained HAZ to cause detrimental Type IV cra ck...
英字タイトル:
FEM Analyses of Creep in Welded Modfied 9Cr Steel Considering Microstructures in Weld and HAZ

Creep-fatigue (Creep fatigue and fatigue) tests of Mod. 9Cr-1Mo steel have been performed by varying stress holding time at 550℃. Creep-fatigue properties are affected by stress holding, and strain rate increases with increasing stress holding time．In Vickers hardness measurements Vickers hardness of creep fatigue damaged specimen is larger than that of fatigue damaged specimen. In magnetic characterization the saturated magnetic flux density and permeability of creep fatigue damaged specimens are larg...
英字タイトル:
Creep-fatigue evaluation and damage characterization for structural materials of advanced fast breeder reactor