A review of a dilatometric analysis of selected Fe-C-Mn high-strength steel shielded metal arc weld metals showed that balanced Ti, B, Al, O, and N additions reduced the austenite-to-ferrite transformation-start (TS) temperature. These microalloy additions must match the following aim levels for composition control: Ti at 400 ppm (0.04 wt-%), B at 40 ppm (0.004 wt-%), Al at 200 ppm (0.020 wt-%), O at 400 ppm (0.04 wt-%), and N preferably below 80 ppm (0.008 wt-%) to ensure effective deoxidation, form complex inclusions, and distribute them to enable development of highly fracture-resistant refined weld metal microstructures. It may be wiser to avoid the rich and lean ends for these microalloy additions, except N, which should be held at the lean end, preferably much below 80 ppm (0.008 wt-%). The balanced Ti, B, Al, O, and N additions offered nearly a 100°C shift in lowering the Charpy V-notch (CVN) test temperature for either 28 or 100 J absorbed energy. Dilatometric evaluations of reheated weld metals showed that 1) the balanced Ti, B, Al, O, and N additions lowered the actual TS temperature by about 60°C compared to the calculated austenite-to-ferrite transformation temperature obtained from the constitutional equation; 2) N with more than 100 ppm (0.010 wt-%) effectively nullified the beneficial effects of Ti, B, and Al additions in lowering the transformation temperature; and 3) at N content much below 80 ppm (0.008 wt-%), both a lower TS temperature and a narrow start-to-finish (TS–Tf) temperature range helped in achieving exceptional weld metal CVN impact toughness.
{"title":"Metallurgical Design Rules for High-Strength Steel Weld Metals","authors":"K. Sampath","doi":"10.29391/2022.101.010","DOIUrl":"https://doi.org/10.29391/2022.101.010","url":null,"abstract":"A review of a dilatometric analysis of selected Fe-C-Mn high-strength steel shielded metal arc weld metals showed that balanced Ti, B, Al, O, and N additions reduced the austenite-to-ferrite transformation-start (TS) temperature. These microalloy additions must match the following aim levels for composition control: Ti at 400 ppm (0.04 wt-%), B at 40 ppm (0.004 wt-%), Al at 200 ppm (0.020 wt-%), O at 400 ppm (0.04 wt-%), and N preferably below 80 ppm (0.008 wt-%) to ensure effective deoxidation, form complex inclusions, and distribute them to enable development of highly fracture-resistant refined weld metal microstructures. It may be wiser to avoid the rich and lean ends for these microalloy additions, except N, which should be held at the lean end, preferably much below 80 ppm (0.008 wt-%). The balanced Ti, B, Al, O, and N additions offered nearly a 100°C shift in lowering the Charpy V-notch (CVN) test temperature for either 28 or 100 J absorbed energy. Dilatometric evaluations of reheated weld metals showed that 1) the balanced Ti, B, Al, O, and N additions lowered the actual TS temperature by about 60°C compared to the calculated austenite-to-ferrite transformation temperature obtained from the constitutional equation; 2) N with more than 100 ppm (0.010 wt-%) effectively nullified the beneficial effects of Ti, B, and Al additions in lowering the transformation temperature; and 3) at N content much below 80 ppm (0.008 wt-%), both a lower TS temperature and a narrow start-to-finish (TS–Tf) temperature range helped in achieving exceptional weld metal CVN impact toughness.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48841646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding structure-parameter-property relationships in friction stir welding of aluminum alloys is a challenge despite its wide application in load-bearing components. In this paper, we propose a combined strategy for mapping the macro- and microstructural responses of these joints. A combined model based on experiment validation was adopted for the prediction of tensile strength. This included the computational fluid dynamics model, precipitation evolution model, dynamic recrystallization and recovery model, and computational solid mechanics model. The comparison between the experimental results and the combined model proved the rationality and accuracy of this numerical model.
{"title":"Entire Process Simulation of Friction Stir Welding — Part 1: Experiments and Simulation","authors":"Yuming Xie, Xiangchen Meng, Yongxian Huang","doi":"10.29391/2022.101.011","DOIUrl":"https://doi.org/10.29391/2022.101.011","url":null,"abstract":"Understanding structure-parameter-property relationships in friction stir welding of aluminum alloys is a challenge despite its wide application in load-bearing components. In this paper, we propose a combined strategy for mapping the macro- and microstructural responses of these joints. A combined model based on experiment validation was adopted for the prediction of tensile strength. This included the computational fluid dynamics model, precipitation evolution model, dynamic recrystallization and recovery model, and computational solid mechanics model. The comparison between the experimental results and the combined model proved the rationality and accuracy of this numerical model.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46321784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Given the limited build volumes for most current additive manufacturing (AM) machines, a method for taking advantage of the unique capabilities offered by AM while combining it with traditional manufacturing methods is needed. Welding of AM-produced components is a solution to this challenge. The objective of this study was to determine the feasibility of using friction stir welding (FSW) to join AlSi10Mg melted with laser powder bed fusion (PBF-L) and examine the effects of postweld heat treatment (HT) and hot isostatic pressing (HIP) on overall joint quality and mechanical performance. Samples were examined using optical microscopy, scanning electron microscopy, hardness testing, and tensile testing. Examination of the samples that underwent a postweld annealing HT revealed cracking along the stir zone and the thermomechanically affected zone (TMAZ) boundary. Examination of the crack revealed evidence of liquation near single-phase silicon precipitates in the TMAZ despite the annealing temperature being 27°C (81°F) below the solidus temperature of the material according to the material specification. Using a calculated pseudobinary phase diagram of AlSi10Mg, the annealing HT was determined to be in the partial liquation regime for AlSi10Mg. The voids and crack formation mechanisms were determined to be caused by constitutional liquation coupled with the unique TMAZ microstructure and stress state. The as-welded and HIP coupons were void and defect free, and FSW was determined to be a feasible method of joining PBF-L aluminum alloys with minimal knockdown in tensile strength.
{"title":"The Effects of Postweld Processing on Friction Stir Welded, Additive Manufactured AlSi10Mg","authors":"M. Eff, Drew Shipley, H. Hack, Seth Shira","doi":"10.29391/2022.101.009","DOIUrl":"https://doi.org/10.29391/2022.101.009","url":null,"abstract":"Given the limited build volumes for most current additive manufacturing (AM) machines, a method for taking advantage of the unique capabilities offered by AM while combining it with traditional manufacturing methods is needed. Welding of AM-produced components is a solution to this challenge. The objective of this study was to determine the feasibility of using friction stir welding (FSW) to join AlSi10Mg melted with laser powder bed fusion (PBF-L) and examine the effects of postweld heat treatment (HT) and hot isostatic pressing (HIP) on overall joint quality and mechanical performance. Samples were examined using optical microscopy, scanning electron microscopy, hardness testing, and tensile testing. Examination of the samples that underwent a postweld annealing HT revealed cracking along the stir zone and the thermomechanically affected zone (TMAZ) boundary. Examination of the crack revealed evidence of liquation near single-phase silicon precipitates in the TMAZ despite the annealing temperature being 27°C (81°F) below the solidus temperature of the material according to the material specification. Using a calculated pseudobinary phase diagram of AlSi10Mg, the annealing HT was determined to be in the partial liquation regime for AlSi10Mg. The voids and crack formation mechanisms were determined to be caused by constitutional liquation coupled with the unique TMAZ microstructure and stress state. The as-welded and HIP coupons were void and defect free, and FSW was determined to be a feasible method of joining PBF-L aluminum alloys with minimal knockdown in tensile strength.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70004246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During robotic welding, several streams of heterogeneous data can be collected. To gain a systemic understanding of the welding process, these data streams have to be combined precisely and accurately, especially if our goal is to develop online weld quality assessments. Establishing correspondence among temporal and spatially based data is a nontrivial effort. This article presents a data collection system using a novel methodology for establishing correspondence across multiple data sources of robotic gas metal arc welding for objective quality assessment. First, correspondence between the weld process data and the resulting weld required time synchronization and spatial alignment. Second, an objective weld quality extraction technique that assigns quantitative measures at a resolution of 1 mm of linear weld travel was developed to evaluate weld quality. Specifically, in addition to developing a method for objective weld profile assessment, we developed an objective analysis of radiographic data for the occurrence of subsurface porosity to assess defects and demonstrate how to objectively quantify the occurrence of surface porosity. While some aspects of this paper have been addressed individually and separately by other research, this paper presents an integrated approach to these operations for a wide variety of weld data types and develops objective weld quality metrics that can be used for machine learning of weld quality for robotic welding.
{"title":"Heterogeneous Measurement System for Data Mining Robotic GMAW Weld Quality","authors":"Adewole Ayoade, J. Steele","doi":"10.29391/2022.101.008","DOIUrl":"https://doi.org/10.29391/2022.101.008","url":null,"abstract":"During robotic welding, several streams of heterogeneous data can be collected. To gain a systemic understanding of the welding process, these data streams have to be combined precisely and accurately, especially if our goal is to develop online weld quality assessments. Establishing correspondence among temporal and spatially based data is a nontrivial effort. This article presents a data collection system using a novel methodology for establishing correspondence across multiple data sources of robotic gas metal arc welding for objective quality assessment. First, correspondence between the weld process data and the resulting weld required time synchronization and spatial alignment. Second, an objective weld quality extraction technique that assigns quantitative measures at a resolution of 1 mm of linear weld travel was developed to evaluate weld quality. Specifically, in addition to developing a method for objective weld profile assessment, we developed an objective analysis of radiographic data for the occurrence of subsurface porosity to assess defects and demonstrate how to objectively quantify the occurrence of surface porosity. While some aspects of this paper have been addressed individually and separately by other research, this paper presents an integrated approach to these operations for a wide variety of weld data types and develops objective weld quality metrics that can be used for machine learning of weld quality for robotic welding.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42019625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Schneiderman, O. Denonno, J. Klemm-Toole, Zhenzhen Yu
The performance of a newly developed multiprincipal-element alloy (MPEA) filler metal for brazing of nickel-based superalloys was directly compared to a conventional boron- and silicon-suppressed filler (BSSF) metal. The comparison was demonstrated on an Alloy 600 substrate with a brazing temperature of 1200°C. Single-phase solidification behavior and the absence of boron and silicon in the MPEA led to a joint microstructure devoid of eutectic constituents or brittle phases in brazes employing this filler metal. In the brazes using the conventional BSSF metal, incomplete isothermal solidification and subsequent athermal solidification of the residual liquid resulted in large particles of a chromium-rich boride phase distributed throughout the microstructure. Tensile testing of brazed butt joints at both room temperature and 600°C testing conditions demonstrated that the MPEA joints exhibited total ductility values at least one order of magnitude greater than that of BSSF joints, but they showed comparable yield strengths in both testing conditions. Fractographic assessment confirmed that boride phases nucleated cracks and resulted in brittle failure in the BSSF joints, while the MPEA joints exhibited extensive ductile microvoid coalescence. Fine-scale porosity and oxide inclusions may be the dominant factors limiting the overall ductility observed in the MPEA brazes.
{"title":"Ductile Braze Repairs for Ni-Based Superalloys Using Novel MPEA Filler Metal","authors":"B. Schneiderman, O. Denonno, J. Klemm-Toole, Zhenzhen Yu","doi":"10.29391/2022.101.007","DOIUrl":"https://doi.org/10.29391/2022.101.007","url":null,"abstract":"The performance of a newly developed multiprincipal-element alloy (MPEA) filler metal for brazing of nickel-based superalloys was directly compared to a conventional boron- and silicon-suppressed filler (BSSF) metal. The comparison was demonstrated on an Alloy 600 substrate with a brazing temperature of 1200°C. Single-phase solidification behavior and the absence of boron and silicon in the MPEA led to a joint microstructure devoid of eutectic constituents or brittle phases in brazes employing this filler metal. In the brazes using the conventional BSSF metal, incomplete isothermal solidification and subsequent athermal solidification of the residual liquid resulted in large particles of a chromium-rich boride phase distributed throughout the microstructure. Tensile testing of brazed butt joints at both room temperature and 600°C testing conditions demonstrated that the MPEA joints exhibited total ductility values at least one order of magnitude greater than that of BSSF joints, but they showed comparable yield strengths in both testing conditions. Fractographic assessment confirmed that boride phases nucleated cracks and resulted in brittle failure in the BSSF joints, while the MPEA joints exhibited extensive ductile microvoid coalescence. Fine-scale porosity and oxide inclusions may be the dominant factors limiting the overall ductility observed in the MPEA brazes.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46696823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aluminum is a key lightweight material for reducing vehicle weight and improving fuel efficiency and is used in wrought, extruded, and cast forms. There is little research on resistance spot welding (RSW) of wrought-to-cast dissimilar aluminum alloys. For this paper, two types of electrodes were developed, and 2.3-mm 5182-O wrought and 4-mm AlSi10MnMg die cast sheets were welded by RSW with different electrode combinations. The results demonstrate that electrode geometry significantly influences the weld nugget morphology, weld performance, and failure mode. The proprietary Newton ring electrode produces the largest weld nugget size and consistent weld performance. Through the optimized electrode combination, severe weld nugget migration problems can be addressed for RSW of dissimilar aluminum alloys. Furthermore, the fracture crack under the tensile shear load always starts from the AlSi10MnMg side but not on the 5182-O side due to work hardening and concentration of stress regardless of whether the welds failed in the interfacial failure or pullout failure modes.
铝是减轻车辆重量和提高燃油效率的关键轻质材料，用于锻造，挤压和铸造形式。目前国内外对异种铝合金的电阻点焊技术研究较少。本文研制了两种电极，采用不同电极组合的RSW焊接了2.3 mm 5182-O锻造和4 mm AlSi10MnMg压铸板材。结果表明，电极几何形状对焊缝熔核形貌、焊缝性能和失效模式有显著影响。专利牛顿环电极产生最大的焊接熔核尺寸和一致的焊接性能。通过优化的电极组合，可以解决异种铝合金RSW中严重的焊核迁移问题。此外，在拉伸剪切载荷作用下，无论焊缝是界面破坏还是拉拔破坏，由于加工硬化和应力集中，断裂裂纹总是从AlSi10MnMg侧开始，而不是从5182-O侧开始。
{"title":"Effects of Electrode Combinations on RSW of 5182-O/AlSi10MnMg Aluminum","authors":"Yanjun Wang, Shanglu Yang","doi":"10.29391/2022.101.005","DOIUrl":"https://doi.org/10.29391/2022.101.005","url":null,"abstract":"Aluminum is a key lightweight material for reducing vehicle weight and improving fuel efficiency and is used in wrought, extruded, and cast forms. There is little research on resistance spot welding (RSW) of wrought-to-cast dissimilar aluminum alloys. For this paper, two types of electrodes were developed, and 2.3-mm 5182-O wrought and 4-mm AlSi10MnMg die cast sheets were welded by RSW with different electrode combinations. The results demonstrate that electrode geometry significantly influences the weld nugget morphology, weld performance, and failure mode. The proprietary Newton ring electrode produces the largest weld nugget size and consistent weld performance. Through the optimized electrode combination, severe weld nugget migration problems can be addressed for RSW of dissimilar aluminum alloys. Furthermore, the fracture crack under the tensile shear load always starts from the AlSi10MnMg side but not on the 5182-O side due to work hardening and concentration of stress regardless of whether the welds failed in the interfacial failure or pullout failure modes.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48202105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, the use of resistance welding in the joining of polymeric materials and polymer composites in the aviation, marine, and automotive industries has been gradually increasing. However, challenges continue in regard to improving product quality as affected by several parameters. This study focused on the effects of wire geometries and wire diameters on the characteristics of polypropylene (PP) sheets united by resistance implant welding. Here, PP sheets manufactured by the injection molding method were joined via the resistance upset welding method with three different wire geometries, including spiral, wavy, and M-shaped, and two different wire diameters of 0.3 and 0.5 mm. Mechanical properties, morphological properties, and heating characteristics were examined. The results showed that wire diameter and wire geometry affected amount of heat formation in the weld zone and, therefore, weld performance in terms of the mechanical properties. The results obtained from the study can be used as a reference in similar applications.
{"title":"Investigation and Optimization of Resistance Implant Welding of Polypropylene Sheets","authors":"H. Bakirci, İ. Karagöz, M. Kaya","doi":"10.29391/2022.101.004","DOIUrl":"https://doi.org/10.29391/2022.101.004","url":null,"abstract":"Recently, the use of resistance welding in the joining of polymeric materials and polymer composites in the aviation, marine, and automotive industries has been gradually increasing. However, challenges continue in regard to improving product quality as affected by several parameters. This study focused on the effects of wire geometries and wire diameters on the characteristics of polypropylene (PP) sheets united by resistance implant welding. Here, PP sheets manufactured by the injection molding method were joined via the resistance upset welding method with three different wire geometries, including spiral, wavy, and M-shaped, and two different wire diameters of 0.3 and 0.5 mm. Mechanical properties, morphological properties, and heating characteristics were examined. The results showed that wire diameter and wire geometry affected amount of heat formation in the weld zone and, therefore, weld performance in terms of the mechanical properties. The results obtained from the study can be used as a reference in similar applications.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44549216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Dai, Zhili Feng, Doug Kyle, S. David, K. Sebeck, Demetrios A. Tzelepis, Katherine Vieau, M. Rogers
Low-temperature phase transformation (LTPT) welding consumables are a new class of welding wires developed to mitigate hydrogen-induced cracking in the welding of high-strength steels without preheating or postweld heat treatment. LTPT weld metals have a high strength, but their toughness needs further investigation. LTPT weld metals predominately contain a martensite microstructure, which is necessary to achieve high strength; however, martensitic weld metals containing oxide inclusions have relatively poor toughness. Three welding processes — gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and hot wire GTAW — were investigated. Optical microscopy, scanning electron microscopes, and transmission electron microscopes were employed for characterization. The role of the shielding gas in the formation of oxide inclusions in LTPT weld metals was investigated. The formation of oxide inclusions in the weld metals was related to the CO2 in the shielding gas. When 100% Ar or a pure inert shielding gas mixture was used for all three welding processes, oxide inclusions were greatly reduced, and the weld metal toughness improved considerably, matching the base metal toughness. The mechanism by which inclusions promote fracture propagation in the weld metal was proposed.
{"title":"The Toughness of High-Strength Steel Weld Metals","authors":"T. Dai, Zhili Feng, Doug Kyle, S. David, K. Sebeck, Demetrios A. Tzelepis, Katherine Vieau, M. Rogers","doi":"10.29391/2022.101.006","DOIUrl":"https://doi.org/10.29391/2022.101.006","url":null,"abstract":"Low-temperature phase transformation (LTPT) welding consumables are a new class of welding wires developed to mitigate hydrogen-induced cracking in the welding of high-strength steels without preheating or postweld heat treatment. LTPT weld metals have a high strength, but their toughness needs further investigation. LTPT weld metals predominately contain a martensite microstructure, which is necessary to achieve high strength; however, martensitic weld metals containing oxide inclusions have relatively poor toughness. Three welding processes — gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and hot wire GTAW — were investigated. Optical microscopy, scanning electron microscopes, and transmission electron microscopes were employed for characterization. The role of the shielding gas in the formation of oxide inclusions in LTPT weld metals was investigated. The formation of oxide inclusions in the weld metals was related to the CO2 in the shielding gas. When 100% Ar or a pure inert shielding gas mixture was used for all three welding processes, oxide inclusions were greatly reduced, and the weld metal toughness improved considerably, matching the base metal toughness. The mechanism by which inclusions promote fracture propagation in the weld metal was proposed.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46143523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhiwei Gao, Dong-po Wang, B. Gong, C. Deng, Shaojie Wu, Hai Zhang
Fatigue tests of cruciform welded joints made of Q355B steel at very-high-cycle fatigue (VHCF) regimes were carried out on as-welded specimens using highfrequency mechanical impact (HFMI) treatment in dry air and water-spray environments, respectively. The influence of the environment on fatigue life was more obvious in the VHCF regime. It was found that S-N curves became flat over the range of 106–108 cycles for as-welded specimens, while a continuously decreasing S-N curve existed for HFMI-treated specimens. Fatigue cracks initiated from the weld toe of the as-welded specimens in dry air and water-spray environments. Due to residual stress, the crack initiation site transition of HFMI-treated specimens from the weld toe to the weld root and base metal was observed at lower stress levels. Moreover, hydrogen-assisted quasi-cleavage and intergranular fracture were captured using a scanning electron microscope and a hydrogen permeation test.
{"title":"VHCF Behavior of Welded Joints with HFMI Treatment under Moisture Conditions","authors":"Zhiwei Gao, Dong-po Wang, B. Gong, C. Deng, Shaojie Wu, Hai Zhang","doi":"10.29391/2022.101.003","DOIUrl":"https://doi.org/10.29391/2022.101.003","url":null,"abstract":"Fatigue tests of cruciform welded joints made of Q355B steel at very-high-cycle fatigue (VHCF) regimes were carried out on as-welded specimens using highfrequency mechanical impact (HFMI) treatment in dry air and water-spray environments, respectively. The influence of the environment on fatigue life was more obvious in the VHCF regime. It was found that S-N curves became flat over the range of 106–108 cycles for as-welded specimens, while a continuously decreasing S-N curve existed for HFMI-treated specimens. Fatigue cracks initiated from the weld toe of the as-welded specimens in dry air and water-spray environments. Due to residual stress, the crack initiation site transition of HFMI-treated specimens from the weld toe to the weld root and base metal was observed at lower stress levels. Moreover, hydrogen-assisted quasi-cleavage and intergranular fracture were captured using a scanning electron microscope and a hydrogen permeation test.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70004149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ömer Üstündağ, S. Gook, A. Gumenyuk, M. Rethmeier, N. Bakir
The application of hybrid laser-arc welding (HLAW) for joining closed circumferential welds is a challenge due to the high risk of forming a defective overlap area with a shrinkage void or solidification cracks in the material thickness. A series of HLAW experiments were performed to understand the development of a faulty overlap area when closing the circumferential weld. Welding trials on flat specimens and pipe segments were supported by numerical analyses in which the thermomechanical behavior of the welds in the overlap area was investigated. Different process control strategies were tested, including variations in defocusing levels and the overlap length. The newly developed HLAW head, including laser optics with a motor-driven collimation system, made it possible to defocus the laser beam during welding without disturbing the stability of the welding process. High-level defocusing of the laser beam of more than 40 mm relative to the specimen surface with a resulting beam diameter of > 2.9 mm, and in combination with a short overlap length of 15 mm, was promising with respect to the formation of a desired cup-shaped weld profile that is resistant to solidification cracks.
{"title":"Hybrid Laser-Arc Welding of Thick-Walled, Closed, Circumferential Pipe Welds","authors":"Ömer Üstündağ, S. Gook, A. Gumenyuk, M. Rethmeier, N. Bakir","doi":"10.29391/2022.101.002","DOIUrl":"https://doi.org/10.29391/2022.101.002","url":null,"abstract":"The application of hybrid laser-arc welding (HLAW) for joining closed circumferential welds is a challenge due to the high risk of forming a defective overlap area with a shrinkage void or solidification cracks in the material thickness. A series of HLAW experiments were performed to understand the development of a faulty overlap area when closing the circumferential weld. Welding trials on flat specimens and pipe segments were supported by numerical analyses in which the thermomechanical behavior of the welds in the overlap area was investigated. Different process control strategies were tested, including variations in defocusing levels and the overlap length. The newly developed HLAW head, including laser optics with a motor-driven collimation system, made it possible to defocus the laser beam during welding without disturbing the stability of the welding process. High-level defocusing of the laser beam of more than 40 mm relative to the specimen surface with a resulting beam diameter of > 2.9 mm, and in combination with a short overlap length of 15 mm, was promising with respect to the formation of a desired cup-shaped weld profile that is resistant to solidification cracks.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43285401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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