Comparison of Creep Behavior of 2.25Cr-1.6W/Mod. 9Cr-1Mo Dissimilar Weld Joint with Each Matching Filler Metal

2005 ◽  
Vol 297-300 ◽  
pp. 1452-1457
Author(s):  
Jong Jin Park ◽  
Cheol Hong Joo ◽  
Jeong Tae Kim ◽  
Hyu Sun Yu
Keyword(s):  
Creep Behavior ◽  
Creep Strength ◽  
Weld Joint ◽  
Filler Metal ◽  
Welded Joint ◽  
Creep Damage ◽  
Creep Rupture ◽  
Dissimilar Weld ◽  
Weld Joints ◽  
Carbon Migration

This paper describes the evaluation of the creep behavior with two types of matching filler metals for 2.25Cr-1.6W(T23)/Mod. 9Cr-1Mo(T91) dissimilar weld joint. Through the welding procedure qualification tests prior to the creep tests, optimum PWHT holding times at 745±5oC were determined as 30minutes for T23 matching filler metal and 60minutes for T91 matching filler metal. It was also confirmed that carbon migration across the weld interfaces and the softened area at HAZ occurred during PWHT. Creep rupture tests were carried out at 575-650oC and 70-220MPa for two dissimilar metal welds manufactured by an optimum PWHT condition. From the comparison of creep rupture strength, it was shown that the creep strength of the welded joint including T23 matching filler metal was similar to that of T23 base material and somewhat higher than that of the welded joint including T91 matching filler metal. From metallurgical study on the crept specimen, the creep damage of T23/T91 dissimilar weld joints could occur at T23 side IC HAZ and near the T23/T91 weld interface simultaneously. However, the final failure locations seemed to depend on the filler metal and the cause of this phenomenon might be regarded as the additional effect of carbon migration across the weld interfaces. It is thought that the dissimilar weld including T91 filler metal which failures at T23 side CG HAZ subject to both metallurgical notch and carbon migration become more susceptible to creep damage than that including T23 filler metal in which the carbon depletion occurs at the T23 filler metal with higher creep strength than T23 HAZ. T23 filler metal can therefore be proposed for matching filler metal of T23/T91 dissimilar weld joints

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.

Evaluation of Creep Strength Reduction Factors for Welded Joints of Modified 9Cr-1Mo Steel (P91)

2006 ◽  
Author(s):  
Masaaki Tabuchi ◽  
Yukio Takahashi
Keyword(s):  
Base Metal ◽  
Creep Strength ◽  
Welded Joints ◽  
Welded Joint ◽  
Rupture Strength ◽  
Reduction Factor ◽  
Creep Rupture ◽  
Type Iv ◽  
Rupture Data ◽  
Term Creep

In order to review the allowable creep strength of high Cr ferritic steels, creep rupture data of base metal and welded joints have been collected and long-term creep strength have been analyzed in the SHC committee in Japan since 2004. In the present paper, the creep rupture data of 370 points for welded joint specimens of modified 9Cr-1Mo steel (ASME Grade 91) offered from seven Japanese companies and institutes were analyzed. These data clearly indicated that the creep strength of welded joints was lower than that of base metal due to Type IV fracture in HAZ at or above 600°C. From the activities of this committee, the master curve for life evaluation of welded joints of Gr.91 steel could be represented as follows: LMP==34154+3494(logσ)−2574(logσ)2,C=31.4 The reduction factor of 100,000 hours creep rupture strength of welded joint to base metal was concluded to be 0.75 at 600°C and 0.70 at 650°C for the Gr.91 steel.

J0310301 Creep Strength of Dissimilar Weld Joint for A-USC Boiler

2015 ◽  
Vol 2015 (0) ◽  
pp. _J0310301--_J0310301-
Author(s):  
Masaaki TABUCHI ◽  
Hiromichi HONGO ◽  
Tetsuya MATSUNAGA ◽  
Fujio ABE
Keyword(s):  
Creep Strength ◽  
Weld Joint ◽  
Dissimilar Weld

A Study for Proposal of Welded Joint Strength Reduction Factors of Modified 9Cr-1Mo Steel for Japan Sodium Cooled Fast Reactor (JSFR)

2013 ◽  
Author(s):  
Takashi Wakai ◽  
Takashi Onizawa ◽  
Takehiko Kato ◽  
Shingo Date ◽  
Koichi Kikuchi ◽  
...  
Keyword(s):  
Base Metal ◽  
Creep Strength ◽  
Welded Joints ◽  
Welded Joint ◽  
Polynomial Equation ◽  
Creep Rupture ◽  
Short Term ◽  
Type Iv ◽  
Rupture Data

This paper proposes provisional welded joint strength reduction factors (WJSRF) of modified 9Cr-1Mo steel (ASME Gr.91) applicable to the structural designing of “Japan sodium cooled fast reactor (JSFR)”. In the welded joints of creep strength enhanced ferritic steels including modified 9Cr-1Mo steel, creep strength may obviously degrade especially in long-term region. This phenomenon is known as “Type-IV” damage. The authors had proposed provisional allowable stress for the welded joints made of the steel in PVP 2010 conference, taking creep strength degradation due to “Type-IV” damage into account. Available creep rupture data of the welded joints made of the steel provided by Japanese steel venders were collected. The temperature range was from 500 to 650°C. The database was analyzed by stress range partitioning 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). The difference in the creep failure mechanisms between short-term and long-term regions is taken into account in this method. Boundary between these regions was half of 0.2% proof stress of the base metal at corresponding temperature. First order polynomial equation of logarithm stress was applied. For conservativeness, allowable stress was proposed provisionally considering design factor for each region. JSME (Japan Society of Mechanical Engineers) published a revised version of the elevated temperature design code in last year. Modified 9Cr-1Mo steel was officially registered in the code as a new structural material for sodium cooled fast reactors. The creep rupture curve for the base metal of the steel was standardized by employing stress range partitioning method, same as for the welded joint. However, second order polynomial equation of logarithm stress was applied in the analysis for the base metal. In addition, the creep rupture data obtained at 700°C were included in the database and data ruptured in very short term, i.e. smaller than 100 hours, were excluded from the analysis. Thus, there are some differences between the procedures to determine the creep rupture curves for base metal and welded joint made of modified 9Cr-1Mo steel. This paper discusses the most feasible procedure to determine the creep rupture curve of the welded joint of the steel by performing some case studies to focus on physical adequacy and harmonization with the determination procedure of the creep rupture curve for the base metal. Then, the WJSRF are provisionally proposed based on the design creep rupture stress intensities. In addition, the design of JSFR pipes was reviewed taking WJSRF into account.

Quantification of Creep Cavitation in Welded Joint and Evaluation of Material Characteristics of Simulated Heat-Affected Zone in X 20 CrMoV 12 1 Steel

2000 ◽  
Vol 123 (1) ◽  
pp. 112-117 ◽  
Author(s):  
Yong-Keun Chung ◽  
Cheol-Hong Joo ◽  
Jong-Jin Park ◽  
Ik-Man Park ◽  
Hyo-Jin Kim
Keyword(s):  
Base Metal ◽  
Heat Affected Zone ◽  
Power Plants ◽  
Welded Joint ◽  
Charpy Impact ◽  
Creep Damage ◽  
Average Diameter ◽  
Damage Mechanism ◽  
Creep Rupture ◽  
Creep Cavitation

X 20 CrMoV 12 1(DIN 17 175) steel has been used for components subjected to high temperature in power plants and chemical and petroleum industries. Therefore, extensive studies have been made on this steel. However, these studies focused mainly on the base metal, and few studies on the welded joint have been reported. Actually, a large number of failures have occurred at the welded joint, so there is increasing need to investigate the characteristics of X 20 CrMoV 12 1 weldment. In this study, the interrupted and creep rupture tests were carried out and quantification of the creep damage was attempted for the X 20 CrMoV 12 1 welded joint. The interrupted and creep rupture tests were performed at four conditions\M650-60, 600-100, 600-120, and 575-150(|SDC-MPa)\Mon the X 20 CrMoV 12 1 welded joint specimens, respectively. It was revealed from the experimental results that creep damage mechanism of a welded joint was mainly creep cavitation, and that the intensively damaged area by creep cavitations was the transition region from fine-grained heat-affected zone (HAZ) to unaffected base metal, namely intercritical HAZ. For both the interrupted and ruptured specimens, quantification of creep damage was attempted by evaluating cavitated area fraction, average diameter, and the number of cavities with creep life fraction. In addition, on the basis of the heat input during the welding, microstructure, microhardness, and grain size of the actual intercritical HAZ, simulated HAZ was made in order to evaluate its material properties. For the simulated HAZ specimens, tensile, charpy impact, and creep rupture tests were carried out. As a result, yield, tensile strength, and elongation of simulated HAZ were similar to those of base metal, respectively, and impact property of simulated HAZ was slightly above base metal. Also, it was found that creep strength of simulated HAZ was inferior to that of the base metal.

Stress Corrosion Cracking Behavior of an Alloy 182-A533B Weld Joint with Continuous Material Properties

2013 ◽  
Vol 716 ◽  
pp. 355-359 ◽  
Author(s):  
Ling Yan Zhao ◽  
He Xue ◽  
Kang Jiao ◽  
Wei Tang
Keyword(s):  
Mechanical Property ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Weld Joint ◽  
Corrosion Cracking ◽  
Mechanical Heterogeneity ◽  
Cracking Behavior ◽  
Dissimilar Weld ◽  
Weld Joints ◽  
Dividing Line

Primary loop recirculation (PLR) piping weld joints in light water reactor (LWR) environments are more susceptible to stress corrosion cracking (SCC). Limited experimental work also suggested the complicated material and mechanical property of the fusion zone and the heat affected zone (HAZ) especially in dissimilar weld joints might play an important role in promoting SCC growth. In our study, different from the former sandwich like weld joint, a model of continuous heterogeneity mechanical property was established, the effect of welded mechanical heterogeneity on the stress-strain field and J-integral along the crack fronts at different locations were simulated in an Alloy 182-A533B dissimilar weld joint by the elastic-plastic finite element method (EPFEM). The results indicate that the crack near the dividing line of base metal (BM) and HAZ has higher resistance to SCC. At the dividing line of HAZ and weld metal (WM), the crack is prone to propagate into the WM, and will present more complex crack morphology and behaviors.

The Welded Joint Strength Reduction Factors of Modified 9Cr–1Mo Steel for the Advanced Loop-Type Sodium Cooled Fast Reactor

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Takuya Yamashita ◽  
Takashi Wakai ◽  
Takashi Onizawa ◽  
Kenichiro Satoh ◽  
Kenji Yamamoto
Keyword(s):  
Base Metal ◽  
Creep Strength ◽  
Welded Joint ◽  
High Stress ◽  
Strength Degradation ◽  
Creep Rupture ◽  
Analysis Method ◽  
Type Iv ◽  
Region Splitting

Creep strength enhanced ferritic (CSEF) steels including ASME Gr.91 are widely used in fossil power plants. In the advanced loop-type sodium-cooled fast reactor (SFR), modified 9Cr–1Mo steel (ASME Gr.91) is going to be adopted as a structural material. Modified 9Cr–1Mo steel was registered in the Japan Society of Mechanical Engineers (JSME) code as a new structural material for SFRs in the year 2012. The creep-rupture curve of the base metal of this steel was standardized using region splitting analysis method. According to this method, creep-rupture data were divided into two regions, high-stress and low-stress regimes, and those regions were individually evaluated by regression analyses with the Larson–Miller parameter (LMP). The difference in the creep failure mechanisms between the high-stress and low-stress regions was considered in this method. The boundary between these regions was half of the 0.2% proof stress of the base metal at the corresponding temperature. In the modified 9Cr–1Mo steel welded joint, creep strength may markedly degrade, especially in the long-term region. This phenomenon is known as “type-IV” damage due to creep voids and cracks in the fine-grained heat-affected zone (HAZ). There is no precedent for indicating the obvious creep strength degradation of welded joints under SFR temperatures (550 °C or less). Although obvious strength degradation of the welded joints has not yet been observed at 550 °C, it is fair to assume that the strength degradation will occur due to very long-term creep. Therefore, considering strength degradation due to “type-IV” damage is necessary. This paper proposes the creep-rupture curve and the welded joint strength-reduction factor (WJSRF). The creep-rupture curve of the welded joint was proposed by employing a second-order polynomial equation with LMP using region splitting analysis method, which is used for the base metal as well. The WJSRFs were proposed on the basis of design creep-rupture stress strength. The resulting allowable stress was conservative compared with that prescribed in ASME code and the Japan domestic regulation for thermal plants. In addition, the design of the hot-leg pipe in SFR was reviewed considering the WJSRFs.

Microstructural characterization and mechanical behavior of Cr25Ni35NbM alloy dissimilar weld joint for application in a hydrogen reformer furnace

2020 ◽  
Vol 117 (6) ◽  
pp. 612
Author(s):  
Jingfeng Guo ◽  
Wenwen Liu ◽  
Chunxiu Li ◽  
Xiaoming Zhang
Keyword(s):  
Tensile Strength ◽  
Stainless Steel ◽  
High Temperature ◽  
Mechanical Behavior ◽  
Weld Joint ◽  
Room Temperature ◽  
Volume Fraction ◽  
Microstructural Characterization ◽  
Dissimilar Weld ◽  
Weld Joints

The microstructural characterization and mechanical behavior of Cr25Ni35NbM/15CrMo and Cr25Ni35NbM/SUS321 dissimilar weld joints were studied in this paper. The microstructure, room temperature and high temperature (1173 K) tensile strength of dissimilar weld joints were analyzed through optical microscopy (OM), scanning electron microscopy (SEM) and electronic universal tensile testing machine. The microstructure of HAZ in 15CrMo steel of Cr25Ni35NbM/15CrMo dissimilar weld joint transformed from ferrite-pearlite into ferrite-martensite. A large volume fraction of α phase was found to have precipitated in the HAZ of SUS321 austenitic stainless steel for Cr25Ni35NbM/SUS321 dissimilar weld joint. At room temperature, the tensile strength and yield strength of these two type dissimilar weld joints is less than Cr25Ni35NbM alloy similar weld joint. The high temperature tensile strength of these two type dissimilar weld joints is less than Cr25Ni35NbM alloy similar weld joint. Both at room and high temperature, the fracture locations of two types dissimilar weld joints are the HAZ of the base metal 15CrMo and SUS321 stainless steel, respectively. It indicates that the weak part of the Cr25Ni35NbM alloy dissimilar weld joints is the low-performance base metals 15CrMo and SUS321 stainless steel.

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