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Byoungchul Hwang - One of the best experts on this subject based on the ideXlab platform.
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correlation of microstructure and charpy impact properties in api x70 and x80 line pipe steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Sang Yong Shin, Byoungchul HwangAbstract:This study aims at correlating microstructure and Charpy impact properties in high-toughness API X70 and X80 line-pipe steels. Three kinds of steels were fabricated by varying alloying elements and hot rolling conditions, and their microstructures and Charpy impact properties were investigated. In addition, their effective grain sizes were characterized by the electron back-scatter diffraction (EBSD) analysis. The Charpy impact test results indicated that the steels rolled in the single Phase Region had the higher upper shelf energy (USE) than the steel rolled in the two Phase Region because their microstructures were composed of acicular ferrites. In the X80 steel rolled in the single Phase Region, the decreased energy transition temperature (ETT) could be explained by the decrease in the overall effective grain size due to the presence of acicular ferrite having smaller effective grain size. Thus, it had excellent mechanical properties in yield and tensile strengths, absorbed energy, and transition temperature, except in ductility.
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effects of notch shape and specimen thickness on drop weight tear test properties of api x70 and x80 line pipe steels
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2007Co-Authors: Sang Yong Shin, Byoungchul Hwang, Ki Bong KangAbstract:In the present study, effects of notch shape and specimen thickness on drop-weight tear test (DWTT) properties of API X70 and X80 line-pipe steels fabricated by varying hot-rolling conditions were investigated. The DWTT was conducted on the rolled steels, and the results were discussed in comparison with the Charpy V-notch (CVN) impact test and crack-tip opening angle (CTOA) test data. The DWTT results indicated that the steels rolled in the single-Phase Region had the higher upper shelf energy (USE) than the steel rolled in the two-Phase Region, because their microstructures were composed of acicular ferrite (AF). The DWTT energy transition temperature (ETT) of the steel rolled in the two-Phase Region was the lowest, because it had a finer effective grain size and the lowest volume fraction of hard secondary Phases. Chevron notch (CN) DWTT energy density did not increase much with increasing specimen thickness, whereas pressed notch (PN) DWTT energy density increased by 1 to 3 J/ mm 2 , because the total energy of the CN DWTT increased less than that of the PN DWTT due to the larger stress concentration at the CN. The ETT increased with increasing specimen thickness due to the increase in constraint state, and the ETT of the CN DWTT was slightly lower than that of PN DWTT. The measured CTOA showed better correlation with the DWTT propagation energy than with the CVN or DWTT total energy because it was related to the crack propagation speed. The value of sin (2CTOA) reliably showed a linearly proportional relation with the DWTT propagation energy density.
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correlation of crack tip opening angle for stable crack propagation with charpy and drop weight tear test properties in high toughness api x70 pipeline steels
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006Co-Authors: Byoungchul Hwang, Sang Yong Shin, Sunghak Lee, Nack J Kim, Sangho Kim, Ki Bong KangAbstract:Correlation between Charpy V-notch (CVN) impact properties, drop-weight tear test (DWTT) properties, and crack-tip opening angles for stable crack propagation (CTOAsc) in high-toughness API X70 pipeline steels was investigated in this study. Two-specimen CTOA test (TSCT) was conducted on the rolled steel materials to measure the CTOAsc, and the test results were compared to the CVN and DWTT data to find correlations between them. The CVN total energy density showed an almost 1:1 linear correlation with the DWTT initiation energy density. The TSCT results indicated that the materials rolled in the single-Phase Region had the larger CTOAsc as well as the higher CVN and DWTT energy density than those rolled in the two-Phase Region because their microstructures were composed of acicular ferrites and fine polygonal ferrites. The CTOAsc had a better correlation with the DWTT propagation energy density or the CVN total energy density than the DWTT total energy density. In particular, the value of sin (2CTOAsc) reliably represented a linear proportional relation to the DWTT propagation energy density.
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effective grain size and charpy impact properties of high toughness x70 pipeline steels
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2005Co-Authors: Byoungchul HwangAbstract:The correlation of microstructure and Charpy V-notch (CVN) impact properties of a high-toughness API X70 pipeline steel was investigated in this study. Six kinds of steel were fabricated by varying the hot-rolling conditions, and their microstructures, effective grain sizes, and CVN impact properties were analyzed. The CVN impact test results indicated that the steels rolled in the single-Phase Region had higher upper-shelf energies (USEs) and lower energy-transition temperatures (ETTs) than the steels rolled in the two-Phase Region because their microstructures were composed of acicular ferrite (AF) and fine polygonal ferrite (PF). The decreased ETT in the steels rolled in the single-Phase Region could be explained by the decrease in the overall effective grain size due to the presence of AF having a smaller effective grain size. On the other hand, the absorbed energy of the steels rolled in the two-Phase Region was considerably lower because a large amount of dislocations were generated inside PFs during rolling. It was further decreased when coarse martensite or cementite was formed during the cooling process.
Sang Yong Shin - One of the best experts on this subject based on the ideXlab platform.
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effects of strain rate and test temperature on torsional deformation behavior of api x70 and x80 linepipe steels
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2010Co-Authors: Yongjin Kim, Sang Yong Shin, Nack J Kim, Yang Gon Kim, Sunghak LeeAbstract:This study aimed at investigating effects of strain rate and test temperature on deformation and fracture behavior of three API X70 and X80 linepipe steels fabricated by varying alloying elements and hot-rolling conditions. Quasi-static and dynamic torsional tests were conducted on these steels having different grain sizes and volume fractions of acicular ferrite and polygonal ferrite, using a torsional Kolsky bar, and then the test data were compared via microstructures, tensile properties, and adiabatic shear band formation. The dynamic torsional test results indicated that the steels rolled in the single-Phase Region had the higher maximum shear stress than the steel rolled in the two-Phase Region, because their microstructures were composed mainly of acicular ferrites. Particularly in the API X80 steel rolled in the single-Phase Region, increased dynamic torsional properties could be explained by the decrease in the overall effective grain size due to the presence of acicular ferrite having smaller effective grain size. The possibility of the adiabatic shear band formation at low temperatures was also analyzed by the energy required for void initiation and difference in effective grain size.
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correlation of microstructure and charpy impact properties in api x70 and x80 line pipe steels
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Sang Yong Shin, Byoungchul HwangAbstract:This study aims at correlating microstructure and Charpy impact properties in high-toughness API X70 and X80 line-pipe steels. Three kinds of steels were fabricated by varying alloying elements and hot rolling conditions, and their microstructures and Charpy impact properties were investigated. In addition, their effective grain sizes were characterized by the electron back-scatter diffraction (EBSD) analysis. The Charpy impact test results indicated that the steels rolled in the single Phase Region had the higher upper shelf energy (USE) than the steel rolled in the two Phase Region because their microstructures were composed of acicular ferrites. In the X80 steel rolled in the single Phase Region, the decreased energy transition temperature (ETT) could be explained by the decrease in the overall effective grain size due to the presence of acicular ferrite having smaller effective grain size. Thus, it had excellent mechanical properties in yield and tensile strengths, absorbed energy, and transition temperature, except in ductility.
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effects of notch shape and specimen thickness on drop weight tear test properties of api x70 and x80 line pipe steels
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2007Co-Authors: Sang Yong Shin, Byoungchul Hwang, Ki Bong KangAbstract:In the present study, effects of notch shape and specimen thickness on drop-weight tear test (DWTT) properties of API X70 and X80 line-pipe steels fabricated by varying hot-rolling conditions were investigated. The DWTT was conducted on the rolled steels, and the results were discussed in comparison with the Charpy V-notch (CVN) impact test and crack-tip opening angle (CTOA) test data. The DWTT results indicated that the steels rolled in the single-Phase Region had the higher upper shelf energy (USE) than the steel rolled in the two-Phase Region, because their microstructures were composed of acicular ferrite (AF). The DWTT energy transition temperature (ETT) of the steel rolled in the two-Phase Region was the lowest, because it had a finer effective grain size and the lowest volume fraction of hard secondary Phases. Chevron notch (CN) DWTT energy density did not increase much with increasing specimen thickness, whereas pressed notch (PN) DWTT energy density increased by 1 to 3 J/ mm 2 , because the total energy of the CN DWTT increased less than that of the PN DWTT due to the larger stress concentration at the CN. The ETT increased with increasing specimen thickness due to the increase in constraint state, and the ETT of the CN DWTT was slightly lower than that of PN DWTT. The measured CTOA showed better correlation with the DWTT propagation energy than with the CVN or DWTT total energy because it was related to the crack propagation speed. The value of sin (2CTOA) reliably showed a linearly proportional relation with the DWTT propagation energy density.
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correlation of crack tip opening angle for stable crack propagation with charpy and drop weight tear test properties in high toughness api x70 pipeline steels
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006Co-Authors: Byoungchul Hwang, Sang Yong Shin, Sunghak Lee, Nack J Kim, Sangho Kim, Ki Bong KangAbstract:Correlation between Charpy V-notch (CVN) impact properties, drop-weight tear test (DWTT) properties, and crack-tip opening angles for stable crack propagation (CTOAsc) in high-toughness API X70 pipeline steels was investigated in this study. Two-specimen CTOA test (TSCT) was conducted on the rolled steel materials to measure the CTOAsc, and the test results were compared to the CVN and DWTT data to find correlations between them. The CVN total energy density showed an almost 1:1 linear correlation with the DWTT initiation energy density. The TSCT results indicated that the materials rolled in the single-Phase Region had the larger CTOAsc as well as the higher CVN and DWTT energy density than those rolled in the two-Phase Region because their microstructures were composed of acicular ferrites and fine polygonal ferrites. The CTOAsc had a better correlation with the DWTT propagation energy density or the CVN total energy density than the DWTT total energy density. In particular, the value of sin (2CTOAsc) reliably represented a linear proportional relation to the DWTT propagation energy density.
Jiansheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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effect of moisture content on flow behavior and resistance characteristics of dense Phase pneumatic conveying
Powder Technology, 2021Co-Authors: Zhen Liu, Jiansheng ZhangAbstract:Abstract The flow characteristic of high pressure dense-Phase pneumatic conveying of pulverized coal is essential to the safe and stable operation of the gasifier. In this paper, the effects of coal moisture content on conveying behavior and resistance characteristics of dense-Phase pneumatic conveying were explored. Meanwhile, a model of the additional pressure drop of particles was proposed and compared with the experimental data. The results show that though the resistance and cohesiveness increase with increasing moisture content, its influence is different in dense and dilute Phase. In the dense-Phase Region, the coal with lower moisture content shows a larger solid mass flow rate and solid concentration; while in the dilute-Phase Region, the moisture content has minor effect on conveying characteristics. For the coal with lower moisture content in dense-Phase Region, the solid mass flow rate and solid concentration are larger, and the gas velocity has a small effect on solid friction factor, due to its smaller cohesiveness and resistance, which is showed in our experiments and inferred from our model. The additional pressure drop model was proposed for straight pipes and bends, whose parameters are probably effective than the existing parameters in this kind of model, as the deviation in the vertical rise pipe, horizontal pipe and bend pipe is controlled within ±30%, and the corresponding vertical down pipe are controlled within ±40%.
Hwang B - One of the best experts on this subject based on the ideXlab platform.
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Correlation of microstructure and fracture properties of API X70 pipeline steels
'Indiana University Press (Project Muse)', 2019Co-Authors: Hwang B, Ym Kim, Lee S, Nj Kim, Ss AhnAbstract:Effects of microstructure on fracture toughness and transition temperature of high-toughness X70 pipeline steels were investigated in this study. Three types of steels were fabricated by varying alloying elements such as C, Cu, and Mo, and their microstructures were varied by rolling conditions such as finish rolling temperature and finish cooling temperature. Charpy V-notch (CVN) impact tests and pressed notch drop-weight tear tests (DWTT) were conducted on the rolled steel specimens. The Charpy impact test results indicated that the specimens rolled in the single-Phase Region of the steel containing a reduced amount of C and Mo had the highest upper shelf energy (USE) and the lowest energy transition temperature (ETT) because of the appropriate formation of acicular, quasipolygonal, or polygonal ferrite and the decreased fraction of martensite-austenite constituents. Most of the specimens rolled in the single-Phase Region also showed excellent DWTT properties as the percent shear area (pct SA) well exceeded 85 pct, irrespective of finish cooling temperatures, while their USE was higher than that of the specimens rolled in the two-Phase Region. Thus, overall fracture properties of the specimens rolled in the single-Phase Region were better than those of the specimens rolled in the two-Phase' Region, considering both USE and pet SA.X14
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Effective grain size and charpy impact properties of high-toughness X70 pipeline steels
'Indiana University Press (Project Muse)', 2019Co-Authors: Hwang B, Ym Kim, Lee S, Nj Kim, Yg Kim, Jy YooAbstract:The correlation of microstructure and Charpy V-notch (CVN) impact properties of a high-toughness API X70 pipeline steel was investigated in this study. Six kinds of steel were fabricated by varying the hot-rolling conditions, and their microstructures, effective grain sizes, and CVN impact properties were analyzed. The CVN impact test results indicated that the steels rolled in the single-Phase Region had higher upper-shelf energies (USES) and lower energy-transition temperatures (ETTs) than the steels rolled in the two-Phase Region because their microstructures were composed of acicular ferrite (AF) and fine polygonal ferrite (PF). The decreased ETT in the steels rolled in the single-Phase Region could be explained by the decrease in the overall effective grain size due to the presence of AF having a smaller effective grain size. On the other hand, the absorbed energy of the steels rolled in the two-Phase Region was considerably lower because a large amount of dislocations were generated inside PFs during rolling. It was further decreased when coarse martensite or cementite was formed during the cooling process.X18
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Effects of molybdenum and vanadium addition on tensile and charpy impact properties of API X70 linepipe steels
'Springer Science and Business Media LLC', 2019Co-Authors: Ym Kim, Hwang B, Lee S, Sy Shin, Lee H, Nj KimAbstract:This study is concerned with the effects of V and Mo addition on tensile and Charpy impact properties of APT X70 linepipe steels. Twelve kinds of steel specimens were produced by varying V and MO additions and rolling conditions. The addition of V and Mo promoted the formation of acicular ferrite (AF), banitic ferrite (BF), and martensite-austenite (MA) constituents, while suppressing the formation of polygonal ferrite (PF) or pearlite (P). The tensile test results indicated that the tensile strength of the specimens rolled in the two-Phase Region increased with the addition of V and Mo, while the yield strength did not vary much in these specimens except the water-cooled specimens, which showed the increased yield strength with addition of Mo. The tensile strength of specimens rolled in the single-Phase Region followed by water cooling increased with increasing V and Mo contents. The yield strength, however, did not vary much with increasing V content or with addition of Mo to the low-V alloy. In these specimens, a Substantial increase in the strengths was achieved only when Mo was added to the high-V alloy. The specimens rolled in the single-Phase Region had higher upper-shelf energy (USE) and lower ductile-brittle transition temperature (DBTT) than the specimens rolled in the two-Phase Region, because their microstructures were composed of AF and fine PF. According to the electron backscatter diffraction (EBSD) analysis data, the effective grain size in AF was determined by crystallographic packets composed of a few fine grains having similar orientations. Thus, the decreased DBTT in the specimens rolled in the single-Phase Region could be explained by the decrease in the overall effective grain size due to the presence of AF having smaller effective,grain size.X13
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Correlation of microstructure and charpy impact properties in API X70 and X80 line-pipe steels
'Elsevier BV', 2019Co-Authors: Sy Shin, Hwang B, Lee S, Nj Kim, Ss AhnAbstract:This study aims at correlating microstructure and Charpy impact properties in high-toughness API X70 and X80 line-pipe steels. Three kinds of steels were fabricated by varying alloying elements and hot rolling conditions, and their microstructures and Charpy impact proper-ties were investigated. In addition, their effective grain sizes were characterized by the electron back-scatter diffraction (EBSD) analysis. The Charpy impact test results indicated that the steels rolled in the single Phase Region had the higher upper shelf energy (USE) than the steel rolled in the two Phase Region because their microstructures were composed of acicular ferrites. In the X80 steel rolled in the single Phase Region, the decreased energy transition temperature (ETT) could be explained by the decrease in the overall effective grain size due to the presence of acicular ferrite having smaller effective grain size. Thus, it had excellent mechanical properties in yield and tensile strengths, absorbed energy, and transition temperature, except in ductility. (c) 2007 Elsevier B.V. All rights reserved.X18
Z Q Sun - One of the best experts on this subject based on the ideXlab platform.
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formation of ultrafine grained ferrite in low carbon steel by heavy deformation in ferrite or dual Phase Region
Journal of Materials Processing Technology, 2003Co-Authors: Y D Huang, W Y Yang, Z Q SunAbstract:Abstract The microstructural refinement supplies an alternative approach to improve the strength of low carbon steel without loss of room temperature ductility. This paper reports the methods to obtain the ultrafine grained ferritic microstructure by the heavy deformation of low carbon steel in ferrite or dual Phase Region. Various initial microstructures before deformation were selected. The deformation microstructure was analyzed by optical microscopy and electron back-scattered diffraction (EBSD) technique. It has been demonstrated that the equiaxed ferritic microstructure with a grain size of around 3 μm was obtained. The coarse pre-eutectoid ferrite dynamically recrystallized to form the ultrafine grained ferrite and the undercooled austenite was transformed to the ultrafine ferrite by the strain-induced austenite to ferrite transformation.
