Where single-sided welding is applied to fabrication and erection of piping made of low alloy steels, stainless steels (SS) and nonferrous alloys, back shielding by inert gas and its maintenance for the first few layers is required to obtain good weldability and to prevent oxidation of welds. In order to save consumption of inert gas, isolations to make a chamber for inert gas purging are placed inside piping for the joint and the adjacent areas to be welded, instead of inert gas purging for the whole piping length. However, placing the isolations before welding and removal of them after welding are sometimes impractical due to piping layout and construction sequence such as closure joints. To solve this issue, practices for omission of back shielding, such as use of flux cored welding filler rods for gas tungsten arc welding (GTAW) or high silicon welding wires for gas metal arc welding in modified wave short circuit mode (GMAW-S), had been developed and achieved the objective. These practices, however, require special training and qualifications for welders, close dimensional tolerance for fit-up, and special welding power source equipped with electrical waveform control. Also, welding quality such as remaining slag or spatters on piping internal is sometimes an issue. To make up for these shortcomings, high silicon solid welding filler rod was introduced to stainless steel welding by GTAW to eliminate back shielding, and mock-up tests were conducted. The properties of the welds were studied by comparison to the welds produced by the other welding processes such as GTAW with back shielding, GTAW with flux cored filler rod without back shielding, and GMAW-S using high silicon solid wire without back shielding. This paper discusses and evaluates the potential of the GTAW with high silicon solid filler rod which can eliminate the inert gas back shielding.
{"title":"Evaluation of Stainless Steels Welds Produced by Gas Tungsten Arc Welding With High Silicon Containing Solid Welding Filler Rod to Omit Back Shielding","authors":"A. Takahashi","doi":"10.1115/pvp2022-80246","DOIUrl":"https://doi.org/10.1115/pvp2022-80246","url":null,"abstract":"\u0000 Where single-sided welding is applied to fabrication and erection of piping made of low alloy steels, stainless steels (SS) and nonferrous alloys, back shielding by inert gas and its maintenance for the first few layers is required to obtain good weldability and to prevent oxidation of welds.\u0000 In order to save consumption of inert gas, isolations to make a chamber for inert gas purging are placed inside piping for the joint and the adjacent areas to be welded, instead of inert gas purging for the whole piping length. However, placing the isolations before welding and removal of them after welding are sometimes impractical due to piping layout and construction sequence such as closure joints. To solve this issue, practices for omission of back shielding, such as use of flux cored welding filler rods for gas tungsten arc welding (GTAW) or high silicon welding wires for gas metal arc welding in modified wave short circuit mode (GMAW-S), had been developed and achieved the objective. These practices, however, require special training and qualifications for welders, close dimensional tolerance for fit-up, and special welding power source equipped with electrical waveform control. Also, welding quality such as remaining slag or spatters on piping internal is sometimes an issue.\u0000 To make up for these shortcomings, high silicon solid welding filler rod was introduced to stainless steel welding by GTAW to eliminate back shielding, and mock-up tests were conducted. The properties of the welds were studied by comparison to the welds produced by the other welding processes such as GTAW with back shielding, GTAW with flux cored filler rod without back shielding, and GMAW-S using high silicon solid wire without back shielding. This paper discusses and evaluates the potential of the GTAW with high silicon solid filler rod which can eliminate the inert gas back shielding.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122999954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yiyu Wang, Wei Zhang, Yanli Wang, Zhili Feng, J. Siefert, Alex Bridges, S. Kung
In this work, multi-scale metallurgical characterizations with advanced microscopy techniques were conducted on an ex-service girth weld between a SA-182 forge 91 (F91) steel reducer to a SA335 pipe 91 (P91) steel header after 141,000 hours (16 years) service at a coal-red power plant between 1991 and 2015. Multiple metallurgical factors, including compositions, inclusions, precipitates, and hardness, were analyzed in comparison for the F91 and P91 steels. The results not only gain an in-depth understanding of creep deformation mechanisms in 9Cr steel welds, but also provide baseline information for remaining lifetime assessments of those service-aged steam components. The results show highly nonuniform creep degradation and damages were observed on the F91 and P91 sides. Base metal and heat affected zone (HAZ) on the F91 steel side experienced a higher degree of microstructure degradation with lower hardness and a higher fraction of creep cavities. Softened zones with lower hardness values were identified in both HAZs of F91 side and P91 side. However, the most creep damaged zones (CDZ) with the highest number density of cavities are not the identified softened zones. In the CDZ, creep cavities are always associated with coarse precipitates (Laves phase, Z phase) and large inclusions (Al oxides, AlN, MnS). A higher fraction of inclusions, coarser precipitates, and larger grain size in F91 steel put itself and its HAZ more vulnerable to creep damages, especially the infamous Type IV cracking.
{"title":"Metallurgical Characterization of a 114,000-Hour Service-Aged Forge 91-Pipe 91 Steel Header Weldment","authors":"Yiyu Wang, Wei Zhang, Yanli Wang, Zhili Feng, J. Siefert, Alex Bridges, S. Kung","doi":"10.1115/pvp2022-85319","DOIUrl":"https://doi.org/10.1115/pvp2022-85319","url":null,"abstract":"\u0000 In this work, multi-scale metallurgical characterizations with advanced microscopy techniques were conducted on an ex-service girth weld between a SA-182 forge 91 (F91) steel reducer to a SA335 pipe 91 (P91) steel header after 141,000 hours (16 years) service at a coal-red power plant between 1991 and 2015. Multiple metallurgical factors, including compositions, inclusions, precipitates, and hardness, were analyzed in comparison for the F91 and P91 steels. The results not only gain an in-depth understanding of creep deformation mechanisms in 9Cr steel welds, but also provide baseline information for remaining lifetime assessments of those service-aged steam components. The results show highly nonuniform creep degradation and damages were observed on the F91 and P91 sides. Base metal and heat affected zone (HAZ) on the F91 steel side experienced a higher degree of microstructure degradation with lower hardness and a higher fraction of creep cavities. Softened zones with lower hardness values were identified in both HAZs of F91 side and P91 side. However, the most creep damaged zones (CDZ) with the highest number density of cavities are not the identified softened zones. In the CDZ, creep cavities are always associated with coarse precipitates (Laves phase, Z phase) and large inclusions (Al oxides, AlN, MnS). A higher fraction of inclusions, coarser precipitates, and larger grain size in F91 steel put itself and its HAZ more vulnerable to creep damages, especially the infamous Type IV cracking.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125449647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The traditional manual welding in pipeline construction is being gradually replaced by semi-automatic and automatic welding in China. Semi-automatic welding is especially applied to X80 pipeline girth weld welding widely. Compared with semi-automatic welding, automatic welding has features of more efficiency, better quality and higher reliability. As the strength of pipeline steel increasing and the length, diameter as well as wall thickness of pipeline enlarging, automatic welding becomes the main trend at the development of the pipeline welding technology in the foreseeable future. Grasping the mechanical properties of X80 pipeline girth weld is crucial to ensuring the safety of pipeline operation. In order to determine the mechanical properties of X80 pipeline girth weld welded by semi-automatic and automatic welding, the experimental specimens were extracted from X80 pipeline girth weld welded by semi-automatic and automatic welding respectively to carry out the uniaxial tensile tests, fracture toughness tests and Charpy impact tests. In the tensile tests, the ultimate tensile strength of X80 pipeline girth weld welded by automatic welding (GWA) was higher than that of X80 pipeline girth weld welded by semi-automatic welding (GWSA) and the former had smaller dispersions. The fracture toughness tests showed that the fracture toughness of GWA was higher than that of GWSA. The Charpy impact tests results revealed that the impact energy of GWA was higher than that of GWSA. From the overall point of view, the mechanical properties of GWA are better than that of GWSA. The automatic welding technique is recommended for the welding of X80 pipeline, which is vitally important to maintain the structural integrity of X80 pipeline.
{"title":"Investigation on Mechanical Properties of X80 Pipeline Girth Weld Welded by Semi-Automatic and Automatic Welding","authors":"W. Ren, J. Shuai","doi":"10.1115/pvp2022-83663","DOIUrl":"https://doi.org/10.1115/pvp2022-83663","url":null,"abstract":"\u0000 The traditional manual welding in pipeline construction is being gradually replaced by semi-automatic and automatic welding in China. Semi-automatic welding is especially applied to X80 pipeline girth weld welding widely. Compared with semi-automatic welding, automatic welding has features of more efficiency, better quality and higher reliability. As the strength of pipeline steel increasing and the length, diameter as well as wall thickness of pipeline enlarging, automatic welding becomes the main trend at the development of the pipeline welding technology in the foreseeable future. Grasping the mechanical properties of X80 pipeline girth weld is crucial to ensuring the safety of pipeline operation. In order to determine the mechanical properties of X80 pipeline girth weld welded by semi-automatic and automatic welding, the experimental specimens were extracted from X80 pipeline girth weld welded by semi-automatic and automatic welding respectively to carry out the uniaxial tensile tests, fracture toughness tests and Charpy impact tests. In the tensile tests, the ultimate tensile strength of X80 pipeline girth weld welded by automatic welding (GWA) was higher than that of X80 pipeline girth weld welded by semi-automatic welding (GWSA) and the former had smaller dispersions. The fracture toughness tests showed that the fracture toughness of GWA was higher than that of GWSA. The Charpy impact tests results revealed that the impact energy of GWA was higher than that of GWSA. From the overall point of view, the mechanical properties of GWA are better than that of GWSA. The automatic welding technique is recommended for the welding of X80 pipeline, which is vitally important to maintain the structural integrity of X80 pipeline.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125453397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xian-Kui Zhu, B. Wiersma, R. Sindelar, W. R. Johnson
The classical Tresca and von Mises strength theories have been utilized extensively for pressure vessel and pipeline design. For pressure vessel design, ASME B&PV code was developed using both Tresca and von Mises strength theories, where the yield strength (YS) was used for an elastic design and the ultimate tensile strength (UTS) was used for an elastic-plastic design. For pipeline design, ASME B31.3, B31G, or other codes were developed using the Tresca strength theory coupled with the YS or a flow stress. The flow stress was introduced to reduce over conservatism from the YS and avoid overestimation from the UTS for many steels. It has been widely accepted that the burst strength of pipelines depends on the UTS and strain hardening rate, n, of the ductile steel. The average shear stress yield theory was thus developed, and the associated burst pressure solution was obtained as a function of UTS and n. Experiments showed that the Zhu-Leis solution provides a reliable prediction of the burst pressure for defect-free thin-wall pipes. In order to extend the Zhu-Leis solution to thick-wall pressure vessels, this work modified the traditional strength theories and obtained new burst pressure solutions for thick-wall pressure vessels. Three new flow stresses were proposed to describe the tensile strength and plastic flow response for a strain hardening material. The associated strength theories were then developed in terms of the Tresca, von Mises and Zhu-Leis yield criteria. From these new strength theories, three burst pressure solutions were obtained for thick-wall cylinders, where the von Mises solution is an upper bound prediction, Tresca solution is a lower bound prediction, and the Zhu-Leis solution is an averaged prediction of burst pressure for thick-wall vessels. Subsequently, the proposed burst solutions were validated by a large dataset of full-scale burst tests.
{"title":"New Strength Theory and Its Application to Determine Burst Pressure of Thick-Wall Pressure Vessels","authors":"Xian-Kui Zhu, B. Wiersma, R. Sindelar, W. R. Johnson","doi":"10.1115/pvp2022-84902","DOIUrl":"https://doi.org/10.1115/pvp2022-84902","url":null,"abstract":"\u0000 The classical Tresca and von Mises strength theories have been utilized extensively for pressure vessel and pipeline design. For pressure vessel design, ASME B&PV code was developed using both Tresca and von Mises strength theories, where the yield strength (YS) was used for an elastic design and the ultimate tensile strength (UTS) was used for an elastic-plastic design. For pipeline design, ASME B31.3, B31G, or other codes were developed using the Tresca strength theory coupled with the YS or a flow stress. The flow stress was introduced to reduce over conservatism from the YS and avoid overestimation from the UTS for many steels.\u0000 It has been widely accepted that the burst strength of pipelines depends on the UTS and strain hardening rate, n, of the ductile steel. The average shear stress yield theory was thus developed, and the associated burst pressure solution was obtained as a function of UTS and n. Experiments showed that the Zhu-Leis solution provides a reliable prediction of the burst pressure for defect-free thin-wall pipes. In order to extend the Zhu-Leis solution to thick-wall pressure vessels, this work modified the traditional strength theories and obtained new burst pressure solutions for thick-wall pressure vessels.\u0000 Three new flow stresses were proposed to describe the tensile strength and plastic flow response for a strain hardening material. The associated strength theories were then developed in terms of the Tresca, von Mises and Zhu-Leis yield criteria. From these new strength theories, three burst pressure solutions were obtained for thick-wall cylinders, where the von Mises solution is an upper bound prediction, Tresca solution is a lower bound prediction, and the Zhu-Leis solution is an averaged prediction of burst pressure for thick-wall vessels. Subsequently, the proposed burst solutions were validated by a large dataset of full-scale burst tests.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127977767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Shrestha, J. Ronevich, Lisa D. Fring, K. Simmons, N. Meeks, Zachary E. Lowe, Timothy J. Harris, C. San Marchi
Numerous projects are looking into distributing blends of natural gas and different amounts of gaseous hydrogen through the existing natural gas distribution system, which is widely composed of medium density polyethylene (MDPE) line pipes. The mechanical behavior of MDPE with hydrogen is not well understood; therefore, the effect of gaseous H2 on the mechanical properties of MDPE needs to be examined. In the current study, we investigate the effects of gaseous H2 on fatigue life and fracture resistance of MDPE in the presence of 3.4 MPa gaseous H2. Fatigue life tests were also conducted at a pressure of 21 MPa to investigate the effect of gas pressure on the fatigue behavior of MDPE. Results showed that the presence of gaseous H2 did not degrade the fatigue life nor the fracture resistance of MDPE. Additionally, based on the value of fracture resistance calculated, a failure assessment diagram was constructed to determine the applicability of using MDPE pipeline for distribution of gaseous H2. Even in the presence of a large internal crack, the failure assessment evaluation indicated that the MDPE pipes lie within the safe region under typical service conditions of natural gas distribution pipeline system.
{"title":"Compatibility of Medium Density Polyethylene (MDPE) for Distribution of Gaseous Hydrogen","authors":"R. Shrestha, J. Ronevich, Lisa D. Fring, K. Simmons, N. Meeks, Zachary E. Lowe, Timothy J. Harris, C. San Marchi","doi":"10.1115/pvp2022-84791","DOIUrl":"https://doi.org/10.1115/pvp2022-84791","url":null,"abstract":"\u0000 Numerous projects are looking into distributing blends of natural gas and different amounts of gaseous hydrogen through the existing natural gas distribution system, which is widely composed of medium density polyethylene (MDPE) line pipes. The mechanical behavior of MDPE with hydrogen is not well understood; therefore, the effect of gaseous H2 on the mechanical properties of MDPE needs to be examined. In the current study, we investigate the effects of gaseous H2 on fatigue life and fracture resistance of MDPE in the presence of 3.4 MPa gaseous H2. Fatigue life tests were also conducted at a pressure of 21 MPa to investigate the effect of gas pressure on the fatigue behavior of MDPE. Results showed that the presence of gaseous H2 did not degrade the fatigue life nor the fracture resistance of MDPE. Additionally, based on the value of fracture resistance calculated, a failure assessment diagram was constructed to determine the applicability of using MDPE pipeline for distribution of gaseous H2. Even in the presence of a large internal crack, the failure assessment evaluation indicated that the MDPE pipes lie within the safe region under typical service conditions of natural gas distribution pipeline system.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"102 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114023247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Ronevich, B. Kagay, C. San Marchi, Yiyu Wang, Zhili Feng, Yanli Wang, K. Findley
Despite their susceptibility to hydrogen-assisted fracture, ferritic steels make up a large portion of the hydrogen infrastructure. It is impractical and too costly to build large scale components such as pipelines and pressure vessels out of more hydrogen-resistant materials such as austenitic stainless steels. Therefore, it is necessary to understand the fracture behavior of ferritic steels in high-pressure hydrogen environments to manage design margins and reduce costs. Quenched and tempered (Q&T) martensite is the predominant microstructure of high-pressure hydrogen pressure vessels, and higher strength grades of this steel type are more susceptible to hydrogen degradation than lower strength grades. In this study, a single heat of 4340 alloy was heat treated to develop alternative microstructures for evaluation of fracture resistance in hydrogen gas. Fracture tests of several microstructures, such as lower bainite and upper bainite with similar strength to the baseline Q&T martensite, were tested at 21 and 105 MPa H2. Despite a higher MnS inclusion content in the tested 4340 alloy which reduced the fracture toughness in air, the fracture behavior in hydrogen gas fit a similar trend to other previously tested Q&T martensitic steels. The lower bainite microstructure performed similar to the Q&T martensite, whereas the upper bainite microstructure performed slightly worse. In this paper, we extend the range of high-strength microstructures evaluated for hydrogen-assisted fracture beyond conventional Q&T martensitic steels.
{"title":"Investigating the Role of Ferritic Steel Microstructure and Strength in Fracture Resistance in High-Pressure Hydrogen Gas","authors":"J. Ronevich, B. Kagay, C. San Marchi, Yiyu Wang, Zhili Feng, Yanli Wang, K. Findley","doi":"10.1115/pvp2022-83915","DOIUrl":"https://doi.org/10.1115/pvp2022-83915","url":null,"abstract":"\u0000 Despite their susceptibility to hydrogen-assisted fracture, ferritic steels make up a large portion of the hydrogen infrastructure. It is impractical and too costly to build large scale components such as pipelines and pressure vessels out of more hydrogen-resistant materials such as austenitic stainless steels. Therefore, it is necessary to understand the fracture behavior of ferritic steels in high-pressure hydrogen environments to manage design margins and reduce costs. Quenched and tempered (Q&T) martensite is the predominant microstructure of high-pressure hydrogen pressure vessels, and higher strength grades of this steel type are more susceptible to hydrogen degradation than lower strength grades. In this study, a single heat of 4340 alloy was heat treated to develop alternative microstructures for evaluation of fracture resistance in hydrogen gas. Fracture tests of several microstructures, such as lower bainite and upper bainite with similar strength to the baseline Q&T martensite, were tested at 21 and 105 MPa H2. Despite a higher MnS inclusion content in the tested 4340 alloy which reduced the fracture toughness in air, the fracture behavior in hydrogen gas fit a similar trend to other previously tested Q&T martensitic steels. The lower bainite microstructure performed similar to the Q&T martensite, whereas the upper bainite microstructure performed slightly worse. In this paper, we extend the range of high-strength microstructures evaluated for hydrogen-assisted fracture beyond conventional Q&T martensitic steels.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126086170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High strength austenite-ferrite duplex stainless steels are a potential alternative to austenitic stainless steels for components in hydrogen gas storage systems. Since these components experience cyclic loading from frequent pressurization and depressurization, the effect of hydrogen on the fatigue behavior of duplex stainless steel must be understood. To determine the influence of hydrogen on fatigue crack initiation and fatigue life of a 255 super duplex stainless steel, circumferentially notched tensile (CNT) specimens were fatigue tested in the as-received condition in air, with pre-charged internal hydrogen in air, and in the as-received condition in high pressure hydrogen gas. The direct current potential difference (DCPD) method was used to detect crack initiation so that S-N curves could be produced for both (i) cycles to crack initiation and (ii) cycles to failure. An electropolished CNT specimen was also cycled in the as-received and hydrogen pre-charged conditions but interrupted just after crack initiation. The microstructural locations of small fatigue cracks were then identified with scanning electron microscopy and electron backscatter diffraction (EBSD). High pressure hydrogen gas and pre-charged hydrogen decreased the fatigue life of 255 duplex stainless steel by a nearly identical amount. The effects of hydrogen on fatigue crack initiation and fatigue life of 255 duplex stainless steel are discussed and compared to austenitic stainless steels.
高强度奥氏体-铁素体双相不锈钢是氢气储存系统中奥氏体不锈钢的潜在替代品。由于这些部件经历了频繁加压和减压的循环加载，因此必须了解氢对双相不锈钢疲劳行为的影响。为确定氢对255超级双相不锈钢疲劳裂纹萌生和疲劳寿命的影响，对环形缺口拉伸(CNT)试样在空气中、空气中预充氢和高压氢气中进行了疲劳试验。采用直流电位差(direct current potential difference, DCPD)方法检测裂纹起裂，从而得到裂纹起裂周期和失效周期的S-N曲线。电抛光碳纳米管样品也在接收和氢气预充条件下循环，但在裂纹萌生后中断。然后利用扫描电镜和电子背散射衍射(EBSD)确定了小疲劳裂纹的显微组织位置。高压氢气和预充氢对255双相不锈钢疲劳寿命的影响几乎相同。讨论了氢对255双相不锈钢疲劳裂纹萌生和疲劳寿命的影响，并与奥氏体不锈钢进行了比较。
{"title":"Influence of High-Pressure Hydrogen Gas and Pre-Charged Hydrogen on Fatigue Crack Initiation and Fatigue Life of 255 Super Duplex Stainless Steel","authors":"B. Kagay, J. Ronevich, C. San Marchi","doi":"10.1115/pvp2022-84797","DOIUrl":"https://doi.org/10.1115/pvp2022-84797","url":null,"abstract":"\u0000 High strength austenite-ferrite duplex stainless steels are a potential alternative to austenitic stainless steels for components in hydrogen gas storage systems. Since these components experience cyclic loading from frequent pressurization and depressurization, the effect of hydrogen on the fatigue behavior of duplex stainless steel must be understood. To determine the influence of hydrogen on fatigue crack initiation and fatigue life of a 255 super duplex stainless steel, circumferentially notched tensile (CNT) specimens were fatigue tested in the as-received condition in air, with pre-charged internal hydrogen in air, and in the as-received condition in high pressure hydrogen gas. The direct current potential difference (DCPD) method was used to detect crack initiation so that S-N curves could be produced for both (i) cycles to crack initiation and (ii) cycles to failure. An electropolished CNT specimen was also cycled in the as-received and hydrogen pre-charged conditions but interrupted just after crack initiation. The microstructural locations of small fatigue cracks were then identified with scanning electron microscopy and electron backscatter diffraction (EBSD). High pressure hydrogen gas and pre-charged hydrogen decreased the fatigue life of 255 duplex stainless steel by a nearly identical amount. The effects of hydrogen on fatigue crack initiation and fatigue life of 255 duplex stainless steel are discussed and compared to austenitic stainless steels.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133704351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Decarbonizing natural gas networks is a challenging enterprise. Replacing natural gas with renewable hydrogen is one option under global consideration to decarbonize heating, power and residential uses of natural gas. Hydrogen is known to degrade fatigue and fracture properties of structural steels, including pipeline steels. In this study, we describe environmental testing strategies aimed at generating baseline fatigue and fracture trends with efficient use of testing resources. For example, by controlling the stress intensity factor (K) in both K-increasing and K-decreasing modes, fatigue crack growth can be measured for multiple load ratios with a single specimen. Additionally, tests can be designed such that fracture tests can be performed at the conclusion of the fatigue crack growth test, further reducing the resources needed to evaluate the fracture mechanics parameters utilized in design. These testing strategies are employed to establish the fatigue crack growth behavior and fracture resistance of API grade steels in gaseous hydrogen environments. In particular, we explore the effects of load ratio and hydrogen partial pressure on the baseline fatigue and fracture trends of line pipe steels in gaseous hydrogen. These data are then used to test the applicability of a simple, universal fatigue crack growth model that accounts for both load ratio and hydrogen partial pressure. The appropriateness of this model for use as an upper bound fatigue crack growth is discussed.
{"title":"Fatigue and Fracture of Pipeline Steels in High-Pressure Hydrogen Gas","authors":"Christopher San Marchi, J. Ronevich","doi":"10.1115/pvp2022-84757","DOIUrl":"https://doi.org/10.1115/pvp2022-84757","url":null,"abstract":"\u0000 Decarbonizing natural gas networks is a challenging enterprise. Replacing natural gas with renewable hydrogen is one option under global consideration to decarbonize heating, power and residential uses of natural gas. Hydrogen is known to degrade fatigue and fracture properties of structural steels, including pipeline steels. In this study, we describe environmental testing strategies aimed at generating baseline fatigue and fracture trends with efficient use of testing resources. For example, by controlling the stress intensity factor (K) in both K-increasing and K-decreasing modes, fatigue crack growth can be measured for multiple load ratios with a single specimen. Additionally, tests can be designed such that fracture tests can be performed at the conclusion of the fatigue crack growth test, further reducing the resources needed to evaluate the fracture mechanics parameters utilized in design. These testing strategies are employed to establish the fatigue crack growth behavior and fracture resistance of API grade steels in gaseous hydrogen environments. In particular, we explore the effects of load ratio and hydrogen partial pressure on the baseline fatigue and fracture trends of line pipe steels in gaseous hydrogen. These data are then used to test the applicability of a simple, universal fatigue crack growth model that accounts for both load ratio and hydrogen partial pressure. The appropriateness of this model for use as an upper bound fatigue crack growth is discussed.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123878349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiang Chen, K. Field, Dalong Zhang, C. Massey, J. Robertson, K. Linton, A. Nelson
FeCrAl alloys are promising candidate materials for the accident tolerant fuel (ATF) cladding application due to their exceptional resistance to oxidation in elevated temperature steam environments. Currently, limited fracture toughness data are available for the FeCrAl alloys, including the FeCrAl alloys newly developed at Oak Ridge National Laboratory (ORNL) under the U.S. Department of Energy’s Advanced Fuels Campaign (AFC) program. In this study, two Generation II candidate FeCrAl alloys, i.e., C06M (81.8Fe-10Cr-6Al-0.03Y-2Mo-0.2Si) and C36M (78.8Fe-13Cr-6Al-0.03Y-2Mo-0.2Si), were irradiated in the High Flux Isotope Reactor (HFIR) at ORNL to assess the fracture characteristics of these alloys after neutron irradiation. A total of six rabbit capsules were irradiated in HFIR at target temperatures of 200°C, 330°C, and 500°C up to target damage doses of 8 displacements per atom (dpa) and 16 dpa. Post-irradiation fracture toughness testing was performed following the Master Curve method in the ASTM E1921 standard. The main findings of this study are: 1) Both the C06M and C36M alloys exhibited a similar response to irradiation concerning irradiation hardening and embrittlement. 2) The irradiation temperature played different roles in terms of irradiation hardening and embrittlement for both C06M and C36M: after irradiation between 166°C and 204°C, both materials exhibited significant irradiation hardening and embrittlement; after irradiation between 315°C and 343°C, both materials showed small irradiation hardening without irradiation embrittlement. After irradiation between 501°C and 507°C, however, the irradiation softening without irradiation embrittlement was observed in both materials. 3) Comparing the microhardness and Master Curve reference temperature T0q before and after neutron irradiation, we did not observe a linear correlation between the two parameters for both C06M and C36M steels. This should be mainly due to a flat response of the Master Curve reference temperature T0q to the irradiations at 166–204°C and 315–343°C ranges 4) C06M showed a lower T0q, meaning better toughness, than C36M at the unirradiated condition, and such trend was kept even after neutron irradiation except for the 166–204°C irradiation after which both materials had similar T0q. 5) In terms of hardening and embrittlement, the irradiation effect on both C06M and C36M appeared to saturate after an irradiation dose of 7 dpa.
{"title":"Post-Irradiation Fracture Toughness Characterization of Generation II FeCrAl Alloys","authors":"Xiang Chen, K. Field, Dalong Zhang, C. Massey, J. Robertson, K. Linton, A. Nelson","doi":"10.2172/1606843","DOIUrl":"https://doi.org/10.2172/1606843","url":null,"abstract":"\u0000 FeCrAl alloys are promising candidate materials for the accident tolerant fuel (ATF) cladding application due to their exceptional resistance to oxidation in elevated temperature steam environments. Currently, limited fracture toughness data are available for the FeCrAl alloys, including the FeCrAl alloys newly developed at Oak Ridge National Laboratory (ORNL) under the U.S. Department of Energy’s Advanced Fuels Campaign (AFC) program. In this study, two Generation II candidate FeCrAl alloys, i.e., C06M (81.8Fe-10Cr-6Al-0.03Y-2Mo-0.2Si) and C36M (78.8Fe-13Cr-6Al-0.03Y-2Mo-0.2Si), were irradiated in the High Flux Isotope Reactor (HFIR) at ORNL to assess the fracture characteristics of these alloys after neutron irradiation. A total of six rabbit capsules were irradiated in HFIR at target temperatures of 200°C, 330°C, and 500°C up to target damage doses of 8 displacements per atom (dpa) and 16 dpa. Post-irradiation fracture toughness testing was performed following the Master Curve method in the ASTM E1921 standard. The main findings of this study are:\u0000 1) Both the C06M and C36M alloys exhibited a similar response to irradiation concerning irradiation hardening and embrittlement.\u0000 2) The irradiation temperature played different roles in terms of irradiation hardening and embrittlement for both C06M and C36M: after irradiation between 166°C and 204°C, both materials exhibited significant irradiation hardening and embrittlement; after irradiation between 315°C and 343°C, both materials showed small irradiation hardening without irradiation embrittlement. After irradiation between 501°C and 507°C, however, the irradiation softening without irradiation embrittlement was observed in both materials.\u0000 3) Comparing the microhardness and Master Curve reference temperature T0q before and after neutron irradiation, we did not observe a linear correlation between the two parameters for both C06M and C36M steels. This should be mainly due to a flat response of the Master Curve reference temperature T0q to the irradiations at 166–204°C and 315–343°C ranges\u0000 4) C06M showed a lower T0q, meaning better toughness, than C36M at the unirradiated condition, and such trend was kept even after neutron irradiation except for the 166–204°C irradiation after which both materials had similar T0q.\u0000 5) In terms of hardening and embrittlement, the irradiation effect on both C06M and C36M appeared to saturate after an irradiation dose of 7 dpa.","PeriodicalId":434862,"journal":{"name":"Volume 4B: Materials and Fabrication","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129125004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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