Creep rupture strength of tungsten-alloyed 9-12 % Cr steels for piping in power plants

1996 ◽  
Vol 67 (9) ◽  
pp. 382-385 ◽  
Author(s):  
Walter Bendick ◽  
Markus Ring
Keyword(s):  
Power Plants ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Cr Steels

Assessment of Creep Rupture Strength for New Martensitic 9% Cr Steels

2007 ◽  
Author(s):  
Walter Bendick ◽  
Jean Gabrel ◽  
Bruno Vandenberghe
Keyword(s):  
Power Plants ◽  
Rupture Strength ◽  
Strength Properties ◽  
Creep Rupture ◽  
Assessment Procedure ◽  
Creep Rupture Strength ◽  
Raw Data ◽  
Cr Steels ◽  
Term Creep

The application of new heat resistant steels in power plants requires reliable long term creep rupture strength values as basis for design. Modern martensitic 9% Cr-steels have complex microstructures that change with service exposure. That is why extrapolations of long term strength properties will be most difficult. Due to new long term test results, re-assessments became necessary for grades 911 and 92. Different methods have been used. Good agreement was obtained between a graphical and the numerical ISO 6303 method. In both cases a two-step assessment procedure was used. First the raw data was prepared in a suitable way, which was followed by mathematical averaging procedures. For comparison a Larson-Miller analysis on the raw data was performed, too. The results turned out to be too optimistic at temperatures higher than 575°C (1050°F). It is shown that a suitable preparation of data can improve the Larson-Miller assessment. As a result of the new assessments the design values had to be reduced for both grades. With respect to previous assessments the new values are up to almost 10% lower. In the case of grade 92 the difference from the former ASME values are even higher. Consequences concerning design and service operation are discussed.

Prediction of Breakdown Transition of Creep Strength in Advanced High Cr Ferritic Steels by Hardness Measurement of Aged Structures at High Temperature

2007 ◽  
Vol 345-346 ◽  
pp. 553-556 ◽  
Author(s):  
Hassan Ghassemi Armaki ◽  
Kouichi Maruyama ◽  
Mitsuru Yoshizawa ◽  
Masaaki Igarashi
Keyword(s):  
Power Plants ◽  
Rupture Strength ◽  
Hardness Measurement ◽  
Creep Rupture ◽  
Ferritic Steels ◽  
Creep Rupture Strength ◽  
Cr Concentration ◽  
Reduction Of Area ◽  
Term Creep

Recent researches have shown the premature breakdown of creep rupture strength in long term creep region of advanced high Cr ferritic steels. As safe operation of power plants becomes a serious problem we should be able to detect and predict the breakdown transition of creep rupture strength. Some methods for detecting the breakdown transition have been presented till now like the measurement of reduction of area after creep rupture and particle size of laves phase. However it will be more economic if we make use of non-destructive tests, for example, hardness testing. In this paper 3 types of ferritic steels with different Cr concentration have been studied. The results suggest that the hardness of aged structures is constant independently of exposure time in short term region, whereas the hardness breaks down in long term region. The boundary of breakdown in hardness coincides with that of breakdown in creep rupture strength.

Predicting Creep Rupture Using Damage Mechanics

2014 ◽  
Author(s):  
Nicola Bonora ◽  
Luca Esposito ◽  
Simone Dichiaro
Keyword(s):  
Power Plants ◽  
Damage Mechanics ◽  
Void Nucleation ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Rupture Time ◽  
Model Parameters ◽  
Strain Accumulation ◽  
Creep Rupture Strength ◽  
Time Data

Creep rupture strength values are basis for design in many high temperature applications. The application of new heat resistant steel in power plants is a typical example where long rupture time data are required. Different assessment methods are available to get the material creep rupture strength in service condition. Mainly these methods are phenomenological in nature or mere procedures of data fitting. The main challenging issue using these methods concerns their reliability of extrapolation from short term creep data. Numerical methods based on continuum damage mechanics (CDM) are largely used to predict creep strain accumulation and creep rupture. Most of the proposed CDM models are based on the Kachanov’s definition of effective stress. Damage accumulates with time (time-fraction) or strain (strain-fraction rule) as a result of void nucleation and growth, and rupture time is predicted to occur when damage reaches a critical value, characteristic for the material. The authors discussed elsewhere the influence of the damage evolution law on the strain accumulation in the tertiary creep stage [1–3]. For a given model formulation, damage model parameters can be identified to reproduce accurately the creep rupture time or the creep rate but usually poor results are obtained in predicting both the strain accumulation in the tertiary stage and the time to rupture. Often a very high value of the critical damage (close to 1) is required to match experimental data, which is not consistent with physical evidences of creep damage. However for time-limited applications a simple linear damage law can be used and a creep rupture formulation can be derived. In this paper the CDM has been used to formulate an engineering approach for creep rupture assessment of metals and alloys.

scholarly journals Effect of PWHT Conditions on Toughness and Creep Rupture Strength in Modified 9Cr-1Mo Steel Welds

2019 ◽  
Vol 38 (2019) ◽  
pp. 739-749 ◽  
Author(s):  
Satoru Nishikawa ◽  
Tadayuki Hasegawa ◽  
Makoto Takahashi
Keyword(s):  
Arc Welding ◽  
Power Plants ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Shielded Metal Arc Welding ◽  
Fracture Appearance Transition Temperature ◽  
Metal Arc Welding ◽  
Fracture Appearance ◽  
Steel Welds

AbstractWe clarified the effect of post weld heat treatment (PWHT) conditions on the toughness and creep rupture strength of modified 9Cr–1Mo steel weldments used for high temperature components of ultra-supercritical power plants. Fracture appearance transition temperature (FATT) decreased as PWHT temperature increased, and for all of the weld metals of tungsten inert gas welding, submerged arc welding and shielded metal arc welding, FATTs were lower than 293 K when the PWHT temperature was higher than 1,008 K. In contrast, in the uniaxial creep test with a loaded stress of 108 MPa, the creep rupture strength of the specimen on which PWHT was carried out for a holding time of 7.2 ks was significantly decreased when the PWHT temperature was more than 1,033 K. Therefore, the appropriate PWHT temperature range to maintain the toughness and creep fracture strength was 1,008 K ≤ T ≤ 1,033 K.

scholarly journals Effect of Carbon, Nitrogen and Nickel on Long-term Creep Rupture Strength of 10 Cr Steels Containing Boron

2011 ◽  
Vol 97 (5) ◽  
pp. 295-304
Author(s):  
Masahiko Arai ◽  
Kentaro Asakura ◽  
Hiroyuki Doi ◽  
Hirotsugu Kawanaka ◽  
Toshihiko Koseki ◽  
...  
Keyword(s):  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Cr Steels ◽  
Term Creep

KUBOTA ALLOY KHR35C

Alloy Digest ◽  
1999 ◽  
Vol 48 (7) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Temperature Performance

Abstract Kubota alloy KHR35C is similar to HP alloy with the addition of niobium to increase its creep-rupture strength. Typical applications include components and assemblies for severe carburizing environments, such as ethylene pyrolysis coils. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as casting and joining. Filing Code: SS-753. Producer or source: Kubota Metal Corporation.

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