Pub Date : 2026-01-28DOI: 10.1016/j.ijpvp.2026.105765
Qiaoling Chu , Zhikun Wang , Dan Yang , Junyao Wang , Fanghua Liao , Zhe Chang , Kai Cao , Saifei Zhang
The microstructural evolution and mechanical property changes of CMT-fabricated Inconel 625 cladding layers under accelerated thermal aging (700 and 800 °C, up to 480 h) were systematically investigated. The as-deposited microstructure consisted of columnar grains with interdendritic chain-like Laves phases. Thermal aging promoted the precipitation of carbides and intermetallic phases, particularly δ-Ni3Nb, whose content increased significantly with rising temperature (700 → 800 °C) and prolonged exposure time at 800 °C. The γ-Ni grain size of Inconel 625 remained stable during aging, contrasting with notable grain coarsening in the 15CrMoG base metals. Mechanical properties exhibited temperature- and time-dependent degradation: hardness increased while bending ductility decreased with extended aging, attributable to δ-Ni3Nb embrittlement. To mitigate δ-Ni3Nb-induced brittleness, the operational temperature of Inconel 625 claddings on boiler tubes should be limited to below 700 °C.
{"title":"Microstructural evolutions and mechanical behavior of Inconel 625 CMT cladding layers during accelerated thermal aging","authors":"Qiaoling Chu , Zhikun Wang , Dan Yang , Junyao Wang , Fanghua Liao , Zhe Chang , Kai Cao , Saifei Zhang","doi":"10.1016/j.ijpvp.2026.105765","DOIUrl":"10.1016/j.ijpvp.2026.105765","url":null,"abstract":"<div><div>The microstructural evolution and mechanical property changes of CMT-fabricated Inconel 625 cladding layers under accelerated thermal aging (700 and 800 °C, up to 480 h) were systematically investigated. The as-deposited microstructure consisted of columnar grains with interdendritic chain-like Laves phases. Thermal aging promoted the precipitation of carbides and intermetallic phases, particularly δ-Ni<sub>3</sub>Nb, whose content increased significantly with rising temperature (700 → 800 °C) and prolonged exposure time at 800 °C. The γ-Ni grain size of Inconel 625 remained stable during aging, contrasting with notable grain coarsening in the 15CrMoG base metals. Mechanical properties exhibited temperature- and time-dependent degradation: hardness increased while bending ductility decreased with extended aging, attributable to δ-Ni<sub>3</sub>Nb embrittlement. To mitigate δ-Ni<sub>3</sub>Nb-induced brittleness, the operational temperature of Inconel 625 claddings on boiler tubes should be limited to below 700 °C.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105765"},"PeriodicalIF":3.5,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146078174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Creep is a dominant failure mode for high-temperature structural components and is inherently characterized by pronounced scatter. However, creep constitutive models capable of describing probabilistic creep rupture remain limited. In this work, the microvoid growth mechanism and statistical distribution characteristics are incorporated into the creep damage accumulation process, then a probabilistic creep damage model is developed. Combined with a Monte Carlo simulation strategy, the proposed model is applied to investigate the scatter in small punch creep tests (SPCT) and uniaxial tensile creep tests of P91 steel. It is found that the 95 % confidence interval of the rupture life predicted for SPCT agrees closely with the experimentally measured 95 % confidence interval from the European Union Joint Research Centre Materials Database engineering materials database, demonstrating that this model can effectively quantify the uncertainty in SPCT rupture life. In addition, the model successfully reproduces the statistical difference in scatter between the two test types, showing that the 95 % confidence interval width of SPCT rupture life is approximately 1.3 times that of uniaxial tensile creep tests data. The proposed probabilistic creep damage model and the associated simulation methodology provide a new theoretical tool for creep data analysis and life prediction, and are of significant engineering value for ensuring highly reliable service of high-temperature components.
{"title":"A probabilistic creep damage model for studying the dispersion of small punch creep test and uniaxial tensile creep test","authors":"Manlin Huang , Jinyuan Wu , Yihan Wang , Jiru Zhong , Kaishu Guan , Bintao Yu","doi":"10.1016/j.ijpvp.2026.105764","DOIUrl":"10.1016/j.ijpvp.2026.105764","url":null,"abstract":"<div><div>Creep is a dominant failure mode for high-temperature structural components and is inherently characterized by pronounced scatter. However, creep constitutive models capable of describing probabilistic creep rupture remain limited. In this work, the microvoid growth mechanism and statistical distribution characteristics are incorporated into the creep damage accumulation process, then a probabilistic creep damage model is developed. Combined with a Monte Carlo simulation strategy, the proposed model is applied to investigate the scatter in small punch creep tests (SPCT) and uniaxial tensile creep tests of P91 steel. It is found that the 95 % confidence interval of the rupture life predicted for SPCT agrees closely with the experimentally measured 95 % confidence interval from the European Union Joint Research Centre Materials Database engineering materials database, demonstrating that this model can effectively quantify the uncertainty in SPCT rupture life. In addition, the model successfully reproduces the statistical difference in scatter between the two test types, showing that the 95 % confidence interval width of SPCT rupture life is approximately 1.3 times that of uniaxial tensile creep tests data. The proposed probabilistic creep damage model and the associated simulation methodology provide a new theoretical tool for creep data analysis and life prediction, and are of significant engineering value for ensuring highly reliable service of high-temperature components.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"222 ","pages":"Article 105764"},"PeriodicalIF":3.5,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146096206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-27DOI: 10.1016/j.ijpvp.2026.105763
Masayuki Kamaya
This study proposes a procedure applicable to fitness-for-service codes to predict ductile failure of a cracked pipe subjected to a bending load. The procedure requires only the yield (proof) and tensile strengths as material properties to predict the failure moment. First, a four-point bending test was conducted using eight stainless steel specimens. The specimens failed due to crack penetration or buckling of the pipe. Then, based on finite element analysis, the moment at ductile crack penetration was predicted using a stress–strain curve accounting for the work hardening properties of the material and a failure criterion for the specimen. The specimen was assumed to have failed when the equivalent stress at a monitoring point reached the flow stress. It was demonstrated that the proposed procedure reasonably predicted the critical moment for ductile crack penetration. On the other hand, the procedure was not suitable for predicting failure due to buckling of the pipe. By introducing a threshold stress, defined as twice the yield strength, to account for failure due to pipe buckling, the failure moment obtained by the tests could be predicted with reasonable accuracy.
{"title":"A procedure for predicting failure moment of stainless steel pipes with a circumferential crack under bending load","authors":"Masayuki Kamaya","doi":"10.1016/j.ijpvp.2026.105763","DOIUrl":"10.1016/j.ijpvp.2026.105763","url":null,"abstract":"<div><div>This study proposes a procedure applicable to fitness-for-service codes to predict ductile failure of a cracked pipe subjected to a bending load. The procedure requires only the yield (proof) and tensile strengths as material properties to predict the failure moment. First, a four-point bending test was conducted using eight stainless steel specimens. The specimens failed due to crack penetration or buckling of the pipe. Then, based on finite element analysis, the moment at ductile crack penetration was predicted using a stress–strain curve accounting for the work hardening properties of the material and a failure criterion for the specimen. The specimen was assumed to have failed when the equivalent stress at a monitoring point reached the flow stress. It was demonstrated that the proposed procedure reasonably predicted the critical moment for ductile crack penetration. On the other hand, the procedure was not suitable for predicting failure due to buckling of the pipe. By introducing a threshold stress, defined as twice the yield strength, to account for failure due to pipe buckling, the failure moment obtained by the tests could be predicted with reasonable accuracy.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105763"},"PeriodicalIF":3.5,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146078076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.ijpvp.2026.105761
Tongtong Yu , Shitong Wei , Shanping Lu
To improve the high-temperature stability of high-Si 9Cr steel weld metals for lead-cooled fast reactors, this work examines how nickel (Ni) affects the microstructure and properties of 9Cr-1.07Si deposited metals during long-term aging and creep rupture. Tests were conducted at 550 °C on two Ni levels samples (0.61 wt% and 1.46 wt%) to compare their thermal aging and creep rupture behaviors. The results indicate that Ni promotes the formation of M6X. This phase acts as an intermediate between M23C6 and Laves phases, facilitating the development of large-sized precipitate clusters and consequently degrading the mechanical properties during aging. Furthermore, post-weld heat treatment (PWHT) enhances microstructural stability during thermal exposure by forming fine M23C6 pinning the grain boundaries. After aging for 10,000 h, the average size of precipitates of specimen without PWHT is 14 % larger than that of specimen with PWHT. Creep rupture tests were thus performed on the PWHT specimens to assess their creep rupture performance. As the precipitates coarsen, their grain-boundary pinning effect weakens, reducing creep resistance, inducing cavities and ultimately leading to fracture through combining cavity growth and deformation. Furthermore, the promotion of M6X coarsening by the increasing Ni content results in lower creep resistance in high-Ni specimen. Under 225 MPa, the average rupture life of 146Ni (89 h) is significantly lower than that of 61Ni (4282 h).
{"title":"Microstructure evolution and creep property of Ni-bearing 9Cr heat-resistant steel deposited metals","authors":"Tongtong Yu , Shitong Wei , Shanping Lu","doi":"10.1016/j.ijpvp.2026.105761","DOIUrl":"10.1016/j.ijpvp.2026.105761","url":null,"abstract":"<div><div>To improve the high-temperature stability of high-Si 9Cr steel weld metals for lead-cooled fast reactors, this work examines how nickel (Ni) affects the microstructure and properties of 9Cr-1.07Si deposited metals during long-term aging and creep rupture. Tests were conducted at 550 °C on two Ni levels samples (0.61 wt% and 1.46 wt%) to compare their thermal aging and creep rupture behaviors. The results indicate that Ni promotes the formation of M<sub>6</sub>X. This phase acts as an intermediate between M<sub>23</sub>C<sub>6</sub> and Laves phases, facilitating the development of large-sized precipitate clusters and consequently degrading the mechanical properties during aging. Furthermore, post-weld heat treatment (PWHT) enhances microstructural stability during thermal exposure by forming fine M<sub>23</sub>C<sub>6</sub> pinning the grain boundaries. After aging for 10,000 h, the average size of precipitates of specimen without PWHT is 14 % larger than that of specimen with PWHT. <strong>C</strong>reep rupture tests <strong>were thus</strong> performed on the PWHT specimens to assess their creep rupture performance. As the precipitates coarsen, their grain-boundary pinning effect weakens, reducing creep resistance, inducing cavities and ultimately leading to fracture through combining cavity growth and deformation. Furthermore, the promotion of M<sub>6</sub>X coarsening by the increasing Ni content results in lower creep resistance in high-Ni specimen. Under 225 MPa, the average rupture life of 146Ni (89 h) is significantly lower than that of 61Ni (4282 h).</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105761"},"PeriodicalIF":3.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-19DOI: 10.1016/j.ijpvp.2026.105762
Chenshuo Cui , Jiaxu Liu , Xin Wang , Fei Teng , Guolin Guo , Tao Meng , Zhengbing Lv , Xuezhi Li , Lijia He , Xiaonan Wang , Xiuhua Gao
With the development of ultra-supercritical units toward higher operating temperatures and pressures, fourth-generation heat-resistant steels have become critical materials for enhancing the service life of key pressure-bearing components. This study investigated the high-temperature oxidation behavior of a novel martensitic heat-resistant steel exposed to air at temperatures ranging from 600 °C to 900 °C for 8 h. The oxidation behavior and mechanisms were analyzed through thermodynamic analysis, weight gain assessment, and microstructural characterization. At different temperatures, the oxidation weight gain curves followed linear, parabolic, and logarithmic patterns. With the increase of temperature, the oxide film gradually changes from thin and continuous dense to discontinuous and loose, covering the whole substrate surface. The increase in oxide layer thickness significantly hindered the mutual diffusion of Fe and O. At 900 °C, the porous oxide layer stratified into a Cr- and Fe-rich inner layer and an Fe-rich outer layer. Fe and O were uniformly distributed in the oxidation products, while Cr tended to enrich in the inner oxide layer. The thickening of the oxide layer and its morphological transformation from granular to dense layered significantly enhance the high-temperature oxidation resistance of heat-resistant steels.
{"title":"High-temperature oxidation behavior of novel martensitic heat-resistant steel exposed to an ambient air atmosphere","authors":"Chenshuo Cui , Jiaxu Liu , Xin Wang , Fei Teng , Guolin Guo , Tao Meng , Zhengbing Lv , Xuezhi Li , Lijia He , Xiaonan Wang , Xiuhua Gao","doi":"10.1016/j.ijpvp.2026.105762","DOIUrl":"10.1016/j.ijpvp.2026.105762","url":null,"abstract":"<div><div>With the development of ultra-supercritical units toward higher operating temperatures and pressures, fourth-generation heat-resistant steels have become critical materials for enhancing the service life of key pressure-bearing components. This study investigated the high-temperature oxidation behavior of a novel martensitic heat-resistant steel exposed to air at temperatures ranging from 600 °C to 900 °C for 8 h. The oxidation behavior and mechanisms were analyzed through thermodynamic analysis, weight gain assessment, and microstructural characterization. At different temperatures, the oxidation weight gain curves followed linear, parabolic, and logarithmic patterns. With the increase of temperature, the oxide film gradually changes from thin and continuous dense to discontinuous and loose, covering the whole substrate surface. The increase in oxide layer thickness significantly hindered the mutual diffusion of Fe and O. At 900 °C, the porous oxide layer stratified into a Cr- and Fe-rich inner layer and an Fe-rich outer layer. Fe and O were uniformly distributed in the oxidation products, while Cr tended to enrich in the inner oxide layer. The thickening of the oxide layer and its morphological transformation from granular to dense layered significantly enhance the high-temperature oxidation resistance of heat-resistant steels.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105762"},"PeriodicalIF":3.5,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-17DOI: 10.1016/j.ijpvp.2026.105756
Yong Gyun Shin, Yoon-Suk Chang
Ensuring the integrity of spent nuclear fuel (SNF) transport cask during extreme accident as well as normal conditions is essential for public and environmental safety. In this study, a series of explosion analyses were conducted for an SNF transport cask and fuel cladding based on a representative hypothetical explosion scenario. First, three numerical methods, namely the conventional weapons effects program, smoothed particle hydrodynamics and coupled Eulerian-Lagrangian, were benchmarked against experimental data from a steel pipe explosion to identify the most reliable one. Finite element (FE) analyses of the transport cask were then primarily performed by considering different detonation angles and configurations with and without the impact limiters. The influence of explosive shapes including cube, cylinder, and sphere was also examined by comparing the resulting shock wave propagation in each cask component. The structural integrity assessment revealed that the factor of safety for all cask components exceeded 1.5 except in the case of a 0° detonation angle. Accordingly, the detailed FE model of an SNF assembly was developed and its integrity was assessed. The subsequent FE analyses showed that the resulting strains remained well below the strain-based failure criterion for all detonation angles in both configurations, suggesting that the limited damage to the cask would not compromise the integrity of the SNF fuel cladding.
{"title":"Structural integrity assessments of SNF transport cask and fuel cladding under hypothetical explosion scenario","authors":"Yong Gyun Shin, Yoon-Suk Chang","doi":"10.1016/j.ijpvp.2026.105756","DOIUrl":"10.1016/j.ijpvp.2026.105756","url":null,"abstract":"<div><div>Ensuring the integrity of spent nuclear fuel (SNF) transport cask during extreme accident as well as normal conditions is essential for public and environmental safety. In this study, a series of explosion analyses were conducted for an SNF transport cask and fuel cladding based on a representative hypothetical explosion scenario. First, three numerical methods, namely the conventional weapons effects program, smoothed particle hydrodynamics and coupled Eulerian-Lagrangian, were benchmarked against experimental data from a steel pipe explosion to identify the most reliable one. Finite element (FE) analyses of the transport cask were then primarily performed by considering different detonation angles and configurations with and without the impact limiters. The influence of explosive shapes including cube, cylinder, and sphere was also examined by comparing the resulting shock wave propagation in each cask component. The structural integrity assessment revealed that the factor of safety for all cask components exceeded 1.5 except in the case of a 0° detonation angle. Accordingly, the detailed FE model of an SNF assembly was developed and its integrity was assessed. The subsequent FE analyses showed that the resulting strains remained well below the strain-based failure criterion for all detonation angles in both configurations, suggesting that the limited damage to the cask would not compromise the integrity of the SNF fuel cladding.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105756"},"PeriodicalIF":3.5,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-17DOI: 10.1016/j.ijpvp.2026.105760
Ting Jin , Yang Liu , Dasheng Wang , Yuebao Lei , Yuebing Li
The limit loads of typical cylinder nozzles with an internal corner crack under combined internal pressure, nozzle axial force and nozzle bending moment are investigated. A plate model with a through-wall crack representing the nozzle hole and the corner crack is recommended for estimating the local limit loads of the corner crack under complex loading conditions. This model is verified by comparing the J values estimated via the reference stress method in R6 using the local limit loads obtained from the plate model and the elastoplastic FE J results for 320 cases. The results show that the FE J results can be predicted reasonably and conservatively by the reference stress method when the local limit load is used. In other words, the local limit load estimated using the plate model is conservative when it is used in structural integrity assessment of the nozzle structures with corner cracks.
{"title":"Local limit load for RPV nozzles with corner cracks under combined internal pressure and nozzle external loads","authors":"Ting Jin , Yang Liu , Dasheng Wang , Yuebao Lei , Yuebing Li","doi":"10.1016/j.ijpvp.2026.105760","DOIUrl":"10.1016/j.ijpvp.2026.105760","url":null,"abstract":"<div><div>The limit loads of typical cylinder nozzles with an internal corner crack under combined internal pressure, nozzle axial force and nozzle bending moment are investigated. A plate model with a through-wall crack representing the nozzle hole and the corner crack is recommended for estimating the local limit loads of the corner crack under complex loading conditions. This model is verified by comparing the <em>J</em> values estimated via the reference stress method in R6 using the local limit loads obtained from the plate model and the elastoplastic FE <em>J</em> results for 320 cases. The results show that the FE <em>J</em> results can be predicted reasonably and conservatively by the reference stress method when the local limit load is used. In other words, the local limit load estimated using the plate model is conservative when it is used in structural integrity assessment of the nozzle structures with corner cracks.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105760"},"PeriodicalIF":3.5,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-13DOI: 10.1016/j.ijpvp.2026.105759
Qingmei Jiang , Xiaoqiang Zhang , Yuguang Cao , Yaya He , Ying Zhen , Guiyi Wu
The global oil and gas pipeline industry has experienced rapid development, with a significant number of pipelines located in geologically challenging areas prone to earthquakes, permafrost, landslides, and other conditions that induce large deformations. For the safety design and assessment of large-deformation pipelines, strain-based criteria offer a more rational approach, especially for girth welds, which are the primary weak points in pipeline integrity. The tensile strain capacity model for pipeline girth welds serves as an effective strain-based criterion. However, existing research provides limited modeling approaches specifically for wide-groove girth welds produced by flux cored arc welding (FCAW) and shielded metal arc welding (SMAW). Existing models inadequately account for key factors influencing strain capacity, such as heat affected zone (HAZ) softening rates, low-strength matching coefficients, internal pressure, and high-low misalignment. Furthermore, these models are based on static crack methodologies, failing to fully capture the ductile tearing characteristics of girth welds, thereby underestimating their strain capacity. To address these gaps, this study employs a dynamic fracture numerical analysis method for pipeline girth welds to comprehensively investigate the factors affecting the strain capacity of combined automatic welding. Based on research patterns and numerical experimental data, an accurate and effective tensile strain capacity model for FCAW/SMAW girth welds is developed. The reliability of the proposed model is validated through comparisons with published experimental results, establishing a strain-based evaluation framework for engineering applications involving FCAW/SMAW girth welds.
{"title":"Research on tensile strain capacity model for FCAW/SMAW girth weld pipeline","authors":"Qingmei Jiang , Xiaoqiang Zhang , Yuguang Cao , Yaya He , Ying Zhen , Guiyi Wu","doi":"10.1016/j.ijpvp.2026.105759","DOIUrl":"10.1016/j.ijpvp.2026.105759","url":null,"abstract":"<div><div>The global oil and gas pipeline industry has experienced rapid development, with a significant number of pipelines located in geologically challenging areas prone to earthquakes, permafrost, landslides, and other conditions that induce large deformations. For the safety design and assessment of large-deformation pipelines, strain-based criteria offer a more rational approach, especially for girth welds, which are the primary weak points in pipeline integrity. The tensile strain capacity model for pipeline girth welds serves as an effective strain-based criterion. However, existing research provides limited modeling approaches specifically for wide-groove girth welds produced by flux cored arc welding (FCAW) and shielded metal arc welding (SMAW). Existing models inadequately account for key factors influencing strain capacity, such as heat affected zone (HAZ) softening rates, low-strength matching coefficients, internal pressure, and high-low misalignment. Furthermore, these models are based on static crack methodologies, failing to fully capture the ductile tearing characteristics of girth welds, thereby underestimating their strain capacity. To address these gaps, this study employs a dynamic fracture numerical analysis method for pipeline girth welds to comprehensively investigate the factors affecting the strain capacity of combined automatic welding. Based on research patterns and numerical experimental data, an accurate and effective tensile strain capacity model for FCAW/SMAW girth welds is developed. The reliability of the proposed model is validated through comparisons with published experimental results, establishing a strain-based evaluation framework for engineering applications involving FCAW/SMAW girth welds.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105759"},"PeriodicalIF":3.5,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-10DOI: 10.1016/j.ijpvp.2026.105758
Dejia Liu , Haitao Xiao , Guodong Lv , Yanchuang Tang , Shanguo Han
The welding of titanium/steel bimetallic sheets exhibits a great challenge owing to the formation of Fe-Ti intermetallic compounds, which can severely degrade the mechanical properties of the welded joint. In this paper, a FeCrNiCu filler metal was used for laser welding TA2/Q235 bimetallic sheets. The strength-ductility synergy and fracture behavior of the welded joint were investigated. A noteworthy finding was that the FeCrNiCu filler metal could generate a high mixing entropy value in the weld seam, which promoted the formation of a primarily face-centered cubic (FCC) phase and coarse grains within the weld seam. The negative enthalpy variation in the transition zones (TZs) on the TA2 layer resulted in phase structures predominantly composed of Fe2Ti, FCC, and α-Ti phases, accompanied by fine grains. Consequently, extremely high hardness values, ranging from 600 to 764 HV0.2 were observed in the TZ. The fragile zones of the welded joint shifted from the weld seam to the TZ, which played a significant role in promoting crack initiation and propagation in the welded joint during mechanical testing. The welded joint fabricated with the FeCrNiCu filler metal exhibited a favorable strength-ductility synergy. The strength coefficient of the welded joint was up to 92.5 %, with a fracture elongation of 6.9 %. Additionally, the welded joint demonstrated promising bending properties. A bending angle of 180° was achieved with no surface cracks observed on the weld seam during root bending tests (compressive stress on the TA2 layer).
{"title":"Investigation on the strength-ductility synergy in the laser-welded titanium/steel bimetallic sheets used for pressure vessels","authors":"Dejia Liu , Haitao Xiao , Guodong Lv , Yanchuang Tang , Shanguo Han","doi":"10.1016/j.ijpvp.2026.105758","DOIUrl":"10.1016/j.ijpvp.2026.105758","url":null,"abstract":"<div><div>The welding of titanium/steel bimetallic sheets exhibits a great challenge owing to the formation of Fe-Ti intermetallic compounds, which can severely degrade the mechanical properties of the welded joint. In this paper, a FeCrNiCu filler metal was used for laser welding TA2/Q235 bimetallic sheets. The strength-ductility synergy and fracture behavior of the welded joint were investigated. A noteworthy finding was that the FeCrNiCu filler metal could generate a high mixing entropy value in the weld seam, which promoted the formation of a primarily face-centered cubic (FCC) phase and coarse grains within the weld seam. The negative enthalpy variation in the transition zones (TZs) on the TA2 layer resulted in phase structures predominantly composed of Fe<sub>2</sub>Ti, FCC, and α-Ti phases, accompanied by fine grains. Consequently, extremely high hardness values, ranging from 600 to 764 HV<sub>0.2</sub> were observed in the TZ. The fragile zones of the welded joint shifted from the weld seam to the TZ, which played a significant role in promoting crack initiation and propagation in the welded joint during mechanical testing. The welded joint fabricated with the FeCrNiCu filler metal exhibited a favorable strength-ductility synergy. The strength coefficient of the welded joint was up to 92.5 %, with a fracture elongation of 6.9 %. Additionally, the welded joint demonstrated promising bending properties. A bending angle of 180° was achieved with no surface cracks observed on the weld seam during root bending tests (compressive stress on the TA2 layer).</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105758"},"PeriodicalIF":3.5,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145978956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
5 %Ni steel is a key material for manufacturing cryogenic storage tanks, which are designed to serve in low-temperature environments. However, welding reduces the low-temperature toughness of the structure, making it particularly important to improve the low-temperature impact toughness of welded joints. In this study, post-weld heat treatment tests were performed on MAG-welded joints of 5 % Ni steel employed in the tanks of very large ethane carriers. The effects of tempering temperatures (200–600 °C) on the microstructural evolution and changes in mechanical properties of the weld metal and heat-affected zone of the welded joint were investigated. The results indicate that weld metal consists of austenitic dendrites. Heat-affected zone primarily consists of bainite-ferrite, M-A constituents, and carbides. The fracture location of the welded joint was within the heat-affected zone. The yield strength, ultimate tensile strength, and elongation were 506 MPa, 679 MPa, and 20 %, respectively. The impact energy of the FL microregion at −140 °C is only 39 J. As the tempering temperature increases, BF undergoes recovery in the heat-affected zone. The redistribution of C leads to the gradual decomposition of the M-A constituent. Within the tempering temperature range of 200–500 °C, no significant changes were observed in the microhardness and tensile properties of the heat-affected zone. At a tempering temperature of 600 °C, the microhardness of the HAZ decreased by 5 % compared to the as-welded condition. Yield strength and ultimate tensile strength decreased by 7 % and 4 %, respectively. The impact toughness of the FL microregion increased by 215 % compared to the as-welded condition. This improvement is attributed to tempering enhancing the plasticity and toughness of the bainite-ferrite matrix while simultaneously reducing stress concentration caused by M-A constituents. Post-weld heat treatment improves the overall properties of welded joints. At a tempering temperature of 600 °C, the strength of the welded joint decreases slightly, but low-temperature impact toughness is significantly enhanced. According to the study, the optimal post-weld heat treatment temperature for MAG welded joints in 5 % Ni steel was determined to be 600 °C.
{"title":"Effects of PWHT on microstructure and mechanical properties of the 5 % Ni steel MAG welded joints","authors":"Zhiwei Zeng , Zhiqiang Zhang , Dongxue Jiang , Jialu Sun , Zhimeng Tian , Luyun Zhang , Henan Huang , Junwei Zhang","doi":"10.1016/j.ijpvp.2026.105754","DOIUrl":"10.1016/j.ijpvp.2026.105754","url":null,"abstract":"<div><div>5 %Ni steel is a key material for manufacturing cryogenic storage tanks, which are designed to serve in low-temperature environments. However, welding reduces the low-temperature toughness of the structure, making it particularly important to improve the low-temperature impact toughness of welded joints. In this study, post-weld heat treatment tests were performed on MAG-welded joints of 5 % Ni steel employed in the tanks of very large ethane carriers. The effects of tempering temperatures (200–600 °C) on the microstructural evolution and changes in mechanical properties of the weld metal and heat-affected zone of the welded joint were investigated. The results indicate that weld metal consists of austenitic dendrites. Heat-affected zone primarily consists of bainite-ferrite, M-A constituents, and carbides. The fracture location of the welded joint was within the heat-affected zone. The yield strength, ultimate tensile strength, and elongation were 506 MPa, 679 MPa, and 20 %, respectively. The impact energy of the FL microregion at −140 °C is only 39 J. As the tempering temperature increases, BF undergoes recovery in the heat-affected zone. The redistribution of C leads to the gradual decomposition of the M-A constituent. Within the tempering temperature range of 200–500 °C, no significant changes were observed in the microhardness and tensile properties of the heat-affected zone. At a tempering temperature of 600 °C, the microhardness of the HAZ decreased by 5 % compared to the as-welded condition. Yield strength and ultimate tensile strength decreased by 7 % and 4 %, respectively. The impact toughness of the FL microregion increased by 215 % compared to the as-welded condition. This improvement is attributed to tempering enhancing the plasticity and toughness of the bainite-ferrite matrix while simultaneously reducing stress concentration caused by M-A constituents. Post-weld heat treatment improves the overall properties of welded joints. At a tempering temperature of 600 °C, the strength of the welded joint decreases slightly, but low-temperature impact toughness is significantly enhanced. According to the study, the optimal post-weld heat treatment temperature for MAG welded joints in 5 % Ni steel was determined to be 600 °C.</div></div>","PeriodicalId":54946,"journal":{"name":"International Journal of Pressure Vessels and Piping","volume":"221 ","pages":"Article 105754"},"PeriodicalIF":3.5,"publicationDate":"2026-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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