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.

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.

Creep Fracture Analysis of W Strengthened 9% Cr Steel Weldment

2010 ◽  
Vol 154-155 ◽  
pp. 1699-1704
Author(s):  
Xue Wang ◽  
Qian Gang Pan ◽  
Zi Jun Liu ◽  
Hui Qiang Zeng ◽  
Yong Shun Tao
Keyword(s):  
Arc Welding ◽  
Rupture Strength ◽  
Fracture Analysis ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Creep Tests ◽  
P92 Steel ◽  
Fine Grained ◽  
Weld Joints ◽  
M23c6 Carbides

The creep rupture behaviour,hardness distribution and microstructure of weldment made by submerge arc welding for W strengthened P92 steel are described in this paper. The cross-weld creep tests were carried out at 923K under stresses in the ranges 130-100MPa. For stress below 120MPa, weld-joints were ruptured by the Type crack, which located in their fine-grained heat affected zone(FGHAZ)with the smallest measured cross-weld hardness. A strong drop in creep rupture strength of weldment was induced by brittle type failure. In addition to coarsening of M23C6 carbides and an equiaxed fine grains in FGHAZ, intermetallic Fe2(Mo,W)Laves phase precipitated on grain boundaries during creep is probably the significant factor caused the type failure.

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.

Modelling creep rupture strength of ferritic steel welds

2000 ◽  
Vol 5 (2) ◽  
pp. 81-89 ◽  
Author(s):  
D. Cole ◽  
C. Martin-Moran ◽  
A.G. Sheard ◽  
H.K.D.H. Bhadeshia ◽  
D.J.C. MacKay
Keyword(s):  
Ferritic Steel ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Steel Welds

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.

Weld Repair of 2-1/4Cr-1Mo Service-Aged Header Welds

1999 ◽  
Vol 121 (4) ◽  
pp. 345-352 ◽  
Author(s):  
R. Viswanathan ◽  
D. Gandy ◽  
S. Findlan
Keyword(s):  
Heat Treatment ◽  
Arc Welding ◽  
Rupture Life ◽  
Postweld Heat Treatment ◽  
Creep Rupture ◽  
Shielded Metal Arc Welding ◽  
Weld Repair ◽  
Metal Arc Welding ◽  
Girth Welds ◽  
Postweld Heat

The objective of this investigation was to evaluate the efficacy of different weld repair techniques as applied to service-aged 2-1/4Cr-1Mo steel weldments. A header which had been in service for 244,000 h at 1050°F (565°C) was utilized for the study. Three girth welds were partially excavated and subjected to repairs using gas tungsten arc welding (GTAW), shielded metal arc welding (SMAW) with postweld heat treatment (PWHT), and without postweld heat treatment using a temperbead technique. Results show that all the weld repairs improved the creep rupture lives of the ex-service weldments and that remaining lives of several decades could be achieved in the repaired condition. The SMAW-temperbead repairs resulted in increase of rupture life, tensile strength, and impact toughness compared to the SMAW-PWHT repairs. The GTAW-PWHT repairs also produced a superior combination of mechanical properties. Remaining creep rupture lives were a function of the extrapolation procedure and specimen size. These results are described here and discussed in comparison with results previously reported for a less severely degraded condition of the steel in order to delineate the effect of prior degradation on weld repair performance.

Effect of Microstructure on Mechanical Behavior of a Combined Steam Turbine Rotor Steel

2015 ◽  
Author(s):  
Ming-Liang Zhu ◽  
Lin-Bo Mei ◽  
Fu-Zhen Xuan
Keyword(s):  
Power Plants ◽  
Rupture Strength ◽  
Plastic Zone Size ◽  
Turbine Rotor ◽  
Combined Cycle ◽  
Load Shedding ◽  
Rotor Steel ◽  
Fracture Appearance Transition Temperature ◽  
Fracture Appearance ◽  
Lower Temperature

High-pressure low-pressure (HLP) combined rotors have been gradually used in advanced power plants. In the present work, tensile, impact, fatigue and creep experiments were conducted to comprehensively investigate mechanical properties of a newly developed combined rotor steel 25Cr2NiMo1V based on microstructure influence. Fatigue crack growth (FCG) rates were obtained by both constant amplitude method and the load-shedding technique. A new method based on cyclic plastic zone size being equalling to grain size was introduced to defferentiate corresponding FCG data in the Paris regime and the near-threshold regime. Results show that 25Cr2NiMo1V steel has sufficient lower temperature strength and toughness in LP zone, and good high temperature creep properties in HP zone. Fracture Appearance Transition Temperature (FATT) at center core of LP is lower than 3°C with a tensile strength of 850 MPa, and creep rupture strength of HP for 105 h is respected to reach 165 MPa at 566°C. By comparison with other combined rotor materials in literature, the properties of 25Cr2NiMo1V steel enable it particularly suitable to HLP rotor material for advanced combined cycle power plants.

INCO-WELD B ELECTRODE

Alloy Digest ◽  
1984 ◽  
Vol 33 (12) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Tensile Properties ◽  
Arc Welding ◽  
Base Alloy ◽  
Heat Treating ◽  
Alternating Current ◽  
Nickel Base Alloy ◽  
Shielded Metal Arc Welding ◽  
Metal Arc Welding ◽  
Nickel Base

Abstract INCO-WELD B is a nickel-base alloy developed for shielded metal-arc welding of nickel steels for cryogenic applications. It is similar to INCO-WELD A Electrode (Alloy Digest Ni-305, November 1984) except that it is designed for use with alternating current to minimize magnetic arc blow. It can be operated in all welding positions. This datasheet provides information on composition and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-307. Producer or source: Huntington Alloys.

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