Creep Strength Evaluation of Mod.9Cr-1Mo Steel Welded Joint by Using Miniature Specimens.

2021 ◽  
Vol 2021.27 (0) ◽  
pp. 10B04
Author(s):  
Ryotaro NEGISHI ◽  
Takashi OGATA
Keyword(s):  
Creep Strength ◽  
Welded Joint ◽  
Strength Evaluation ◽  
Miniature Specimens

scholarly journals Stress Relaxation Testing of Service Exposed IN738 for Creep Strength Evaluation

1999 ◽  
Author(s):  
David A. Woodford
Keyword(s):  
Stress Relaxation ◽  
Creep Strength ◽  
Standard Size ◽  
Strength Evaluation ◽  
Management Procedure ◽  
Section Size ◽  
Long Time ◽  
Evaluation Measurement ◽  
Miniature Specimens ◽  
Base Data

Standard size and miniature specimens of IN738 were taken from a service exposed turbine blade and vane for comparative stress relaxation testing at 800C, 850C and 900C. Base data taken from root section material were used to construct stress vs. creep rate parametric curves which could be used directly in design. Up to five decades in creep rates were obtained at each temperature from tests lasting less than one day. The data were also presented in the form of stress vs. predicted times to 0.5% creep which compared well with available long time creep data. Differences were noted in specimens taken from different locations in the airfoil regions which probably resulted from differences in grain size or orientation. Based on these measurements it was concluded that there was no significant effect of section size on creep strength as defined by this test, and that the alloy was quite insensitive to prior deformation and thermal exposures. A life management procedure, using a combination or creep strength evaluation based on the stress relaxation test and a separate fracture evaluation measurement, is outlined in which end of useful life is defined in terms of minimum acceptable performance levels.

Stress Relaxation Testing of Service Exposed IN738 for Creep Strength Evaluation

2000 ◽  
Vol 122 (3) ◽  
pp. 451-456 ◽  
Author(s):  
David A. Woodford
Keyword(s):  
Stress Relaxation ◽  
Creep Strength ◽  
Standard Size ◽  
Strength Evaluation ◽  
Management Procedure ◽  
Section Size ◽  
Long Time ◽  
Evaluation Measurement ◽  
Miniature Specimens ◽  
Base Data

Standard size and miniature specimens of IN738 were taken from a service exposed turbine blade and vane for comparative stress relaxation testing at 800C, 850C, and 900C. Base data taken from root section material were used to construct stress versus creep rate parametric curves which could be used directly in design. Up to five decades in creep rates were obtained at each temperature from tests lasting less than one day. The data were also presented in the form of stress versus predicted times to 0.5 percent creep which compared well with available long time creep data. Differences were noted in specimens taken from different locations in the airfoil regions which probably resulted from differences in grain size or orientation. Based on these measurements it was concluded that there was no significant effect of section size on creep strength as defined by this test, and that the alloy was quite insensitive to prior deformation and thermal exposures. A life management procedure, using a combination of creep strength evaluation based on the stress relaxation test and a separate fracture evaluation measurement, is outlined in which end of useful life is defined in terms of minimum acceptable performance levels. [S0742-4795(00)01803-2]

scholarly journals Effects of Full Annealing Heat Treatment on Long-term Creep Strength of 2.25Cr-1Mo Steel Welded Joint

2003 ◽  
Vol 21 (2) ◽  
pp. 195-203 ◽  
Author(s):  
Kazuhiro KIMURA ◽  
Takashi WATANABE ◽  
Hiromichi HONGO ◽  
Masayoshi YAMAZAKI ◽  
Jun-ichi KINUGAWA ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Creep Strength ◽  
Welded Joint ◽  
Annealing Heat Treatment ◽  
Full Annealing ◽  
Term Creep ◽  
Annealing Heat

scholarly journals Fatigue Strength Evaluation of Welded Joint in Pressure Vessel by Probabilistic Fracture Mechanics.

1997 ◽  
Vol 46 (7) ◽  
pp. 795-800
Author(s):  
Shuichi TANI ◽  
Akemi HIJIKATA ◽  
Yuujirou MATSUSIMA ◽  
Akio INOUE ◽  
Sumio YOSHIOKA
Keyword(s):  
Fatigue Strength ◽  
Fracture Mechanics ◽  
Pressure Vessel ◽  
Welded Joint ◽  
Strength Evaluation ◽  
Probabilistic Fracture Mechanics

Creep Strength Evaluation of Welded Joint Made of Modified 9Cr-1Mo Steel for Japanese Sodium Cooled Fast Reactor (JSFR)

2010 ◽  
Author(s):  
Takashi Wakai ◽  
Yuji Nagae ◽  
Takashi Onizawa ◽  
Satoshi Obara ◽  
Yang Xu ◽  
...  
Keyword(s):  
Creep Strength ◽  
Welded Joints ◽  
Welded Joint ◽  
Strength Degradation ◽  
Creep Rupture ◽  
Primary Circuit ◽  
Allowable Stress ◽  
Type Iv ◽  
Term Creep

This paper describes a proposal of provisional allowable stress for the welded joints made of modified 9Cr-1Mo steel (ASME Gr.91) applicable to the structural design of Japanese Sodium cooled Fast Reactor (JSFR). For the early commercialization of the SFRs, economic competitiveness is one of the most essential requirements. One of the most practical means to reduce the construction costs is to diminish the total amount of structural materials. To meet the requirements, modified 9Cr-1Mo steel has attractive characteristics as a main structural material of SFRs, because the steel has both excellent thermal properties and high temperature strength. Employing the steel to the main pipe material, remarkable compact plant design can be achieved. There is only one elbow in the hot leg pipe of the primary circuit. However, in such a compact piping, it is difficult to keep enough distance between welded joint and high stress portion. In the welded joints of creep strength enhanced ferritic steels including ASME Gr.91 (modified 9Cr-1Mo) steel, creep strength may obviously degrade especially in long-term region. This phenomenon is known as “Type-IV” damage. Though obvious strength degradation has not observed at 550°C yet for the welded joint made of modified 9Cr-1Mo steel, it is proper to suppose strength degradation must take place in very long-term creep. Therefore, taking strength degradation due to “Type-IV” damage into account, the allowable stress applicable to JSFR pipe design was proposed based on creep rupture test data acquired in temperature accelerated conditions. Available creep rupture test data of welded joints made of modified 9Cr-1Mo steel provided by Japanese steel vender were collected. The database was analyzed by region partition method. The creep rupture data were divided into two regions of short-term and long-term and those were individually evaluated by regression analyses with Larson Miller Parameter (LMP). Boundary condition between short-term and long-term was half of 0.2% proof stress of base metal at corresponding temperature. First order equation of logarithm stress was applied. For conservativeness, allowable stress was proposed provisionally considering design factor for each region. Present design of JSFR hot leg pipe of primary circuit was evaluated using the proposed allowable stress. As a result, it was successfully demonstrated that the compact pipe design was assured. For validation of the provisional allowable stress, a series of long-term creep tests were started. In future, the provisional allowable stress will be properly reexamined when longer creep rupture data are obtained. In addition, some techniques to improve the performance of welded joints were surveyed and introduced.

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