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Improving creep strength of the fine-grained heat-affected zone of novel 9Cr martensitic heat-resistant steel via modified thermo-mechanical treatment 被引量:1
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作者 Jingwen Zhang Liming Yu +6 位作者 Yongchang Liu Ran Ding Chenxi Liu Zongqing Ma Huijun Li Qiuzhi Gao Hui Wang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2024年第5期1037-1047,共11页
The infamous type Ⅳ failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants.In this work,the traditional the... The infamous type Ⅳ failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants.In this work,the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling,i.e.,normalizing,cold rolling,and tempering (NCT),which was developed to improve the creep strength of the FGHAZ in G115 steel weldments.The NCT treatment effectively promoted the dissolution of preformed M_(23)C_(6)particles and relieved the boundary segregation of C and Cr during welding thermal cycling,which accelerated the dispersed reprecipitation of M_(23)C_(6) particles within the fresh reaustenitized grains during post-weld heat treatment.In addition,the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations.As a result,the interacting actions between precipitates,dislocations,and boundaries during creep were reinforced considerably.Following this strategy,the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%,which can further push the application of G115 steel in USC power plants. 展开更多
关键词 G115 steel fine-grained heat-affected zone creep strength element segregation nano-sized precipitates
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High-Efficiency Dynamic Scanning Strategy for Powder Bed Fusion by Controlling Temperature Field of the Heat-Affected Zone
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作者 Xiaokang Huang Xiaoyong Tian +5 位作者 Qi Zhong Shunwen He Cunbao Huo Yi Cao Zhiqiang Tong Dichen Li 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2024年第1期203-214,共12页
Improvement of fabrication efficiency and part performance was the main challenge for the large-scale powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature fiel... Improvement of fabrication efficiency and part performance was the main challenge for the large-scale powder bed fusion(PBF)process.In this study,a dynamic monitoring and feedback system of powder bed temperature field using an infrared thermal imager has been established and integrated into a four-laser PBF equipment with a working area of 2000 mm×2000 mm.The heat-affected zone(HAZ)temperature field has been controlled by adjusting the scanning speed dynamically.Simultaneously,the relationship among spot size,HAZ temperature,and part performance has been established.The fluctuation of the HAZ temperature in four-laser scanning areas was decreased from 30.85℃to 17.41℃.Thus,the consistency of the sintering performance of the produced large component has been improved.Based on the controllable temperature field,a dynamically adjusting strategy for laser spot size was proposed,by which the fabrication efficiency was improved up to 65.38%.The current research results were of great significance to the further industrial applications of large-scale PBF equipment. 展开更多
关键词 Powder bed fusion EFFICIENCY LARGE-SCALE Spot size heat-affected zone(HAZ)
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Effect of Dynamic Strain Aging on Hardness in the Heat-Affected Zone of SUS316 Steel Welds
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作者 Lina Yu Kazutoshi Nishimoto Kazuyoshi Saida 《材料科学与工程(中英文A版)》 2023年第1期13-25,共13页
DSA(dynamic strain aging)phenomenon in SUS316 steel was investigated using isothermal and non-isothermal tensile tests of simulated HAZ(heat-affected zone)thermal cycles.Isothermal tensile tests were performed on SUS3... DSA(dynamic strain aging)phenomenon in SUS316 steel was investigated using isothermal and non-isothermal tensile tests of simulated HAZ(heat-affected zone)thermal cycles.Isothermal tensile tests were performed on SUS316 in the peak temperature range of 20-700°C,with strain rates varying from 4.2×10^(-3)to 4.2×10^(-5)s^(-1).Based on the appearance of discontinuous plastic flows,expressed as serrations,and the hardening phenomenon of the tensile samples,the conditions for the occurrence of DSA in the SUS316 steel were investigated.Furthermore,the extent of hardening due to DSA was evaluated by comparing the hardness values of the SUS316 and SUS316EHP steels after the tensile tests.To confirm the effect of DSA on hardness in the HAZ of the welded SUS316 steel,non-isothermal tensile tests of the simulated HAZ thermal cycles were performed using a Thermec Master.The relationship between the increase in Vickers hardness due to DSA and the strain in the HAZ was determined;the effect of DSA on hardness in the HAZ could be predicted.The DSA in SUS316 steel was found to be mainly attributed to the dynamic interaction of dislocations with C and N interstitial atoms during high-temperature deformation. 展开更多
关键词 Dynamic strain aging HARDNESS SERRATION heat-affected zone SUS316
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In situ observation of austenite grain growth behavior in the simulated coarse-grained heat-affected zone of Ti-microalloyed steels 被引量:13
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作者 Xiang-liang Wan Kai-ming Wu +2 位作者 Gang Huang Ran Wei Lin Cheng 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2014年第9期878-885,共8页
The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then gre... The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then grew in different directions through movement of grain boundaries into the ferrite phase. Subsequently, the adjacent austenite grains impinged against each other during the α→γtransformation. After the α→γ transformation, austenite grains coarsened via the coalescence of small grains and via boundary migration between grains. The growth process of austenite grains was a continuous process during heating, isothermal holding, and cooling in simulated thermal cycling. Abundant finely dispersed nanoscale TiN particles in a steel specimen containing 0.012wt% Ti effectively retarded the grain boundary migration, which resulted in refined austenite grains. When the Ti concentration in the steel was increased, the number of TiN particles de- creased and their size coarsened. The big particles were not effective in pinning the austenite grain boundary movement and resulted in coarse austenite grains. 展开更多
关键词 alloy steel AUSTENITE grain growth heat-affected zone COARSENING titanium nitride
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Liquation cracking in the heat-affected zone of IN939 superalloy tungsten inert gas weldments 被引量:4
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作者 Hassan Kazempour-Liasi Mohammad Tajally Hassan Abdollah-Pour 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2020年第6期764-773,共10页
The main aim of this study was to investigate liquation cracking in the heat-affected zone(HAZ)of the IN939 superalloy upon tungsten inert gas welding.A solid solution and age-hardenable filler metals were further stu... The main aim of this study was to investigate liquation cracking in the heat-affected zone(HAZ)of the IN939 superalloy upon tungsten inert gas welding.A solid solution and age-hardenable filler metals were further studied.On the pre-weld heat-treated samples,upon solving the secondaryγ′particles in the matrix,primaryγ′particles in the base metal grew to"ogdoadically diced cubes"of about 2μm in side lengths.The pre-weld heat treatment reduced the hardness of the base metal to about HV 310.Microstructural studies using optical and fieldemission scanning electron microscopy revealed that the IN939 alloy was susceptible to liquation cracking in the HAZ.The constitutional melting of the secondary,eutectic,and Zr-rich phases promoted the liquation cracking in the HAZ.The microstructure of the weld fusion zones showed the presence of fine spheroidalγ′particles with sizes of about 0.2μm after the post-weld heat treatment,which increased the hardness of the weld pools to about HV 350 and 380 for the Hastelloy X and IN718 filler metals,respectively.Application of a suitable solid solution filler metal could partially reduce the liquation cracking in the HAZ of IN939 alloy. 展开更多
关键词 SUPERALLOY tungsten inert gas WELD heat-affected zone liquation cracking
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Microstructure and embrittlement of the fine-grained heat-affected zone of ASTM4130 steel 被引量:2
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作者 Li-ying Li Yong Wang Tao Han Chao-wen Li 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2011年第4期419-423,共5页
The mechanical properties and microstructure features of the fine-grained heat-affected zone(FGHAZ) of ASTM4130 steel was investigated by optical microscope(OM),scanning electron microscope(SEM),transmission ele... The mechanical properties and microstructure features of the fine-grained heat-affected zone(FGHAZ) of ASTM4130 steel was investigated by optical microscope(OM),scanning electron microscope(SEM),transmission electron microscope(TEM),and welding thermal simulation test.It is found that serious embrittlement occurs in the FGHAZ with an 81.37% decrease of toughness,compared with that of the base metal.Microstructure analysis reveals that the FGHAZ is mainly composed of acicular,equiaxed ferrite,granular ferrite,martensite,and martensite-austenite(M-A) constituent.The FGHAZ embrittlement is mainly induced by granular ferrite because of carbides located at its boundaries and sub-boundaries.Meanwhile,the existence of martensite and M-A constituent,which distribute in a discontinuous network,is also detrimental to the mechanical properties. 展开更多
关键词 ASTM4130 steel WELDING heat-affected zone MICROSTRUCTURE EMBRITTLEMENT
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Influence of different microstructural features on impact toughness and crack initiation behavior of coarse grain heat-affected zone in X80 pipeline steel 被引量:2
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作者 QIAN Weifang 《Baosteel Technical Research》 CAS 2021年第4期2-11,共10页
Coarse grain heat-affected zone samples of X80 pipeline steel under different heat inputs were obtained through thermal welding simulation experiments with Gleeble 3500.Charpy impact tests and a combination of multisc... Coarse grain heat-affected zone samples of X80 pipeline steel under different heat inputs were obtained through thermal welding simulation experiments with Gleeble 3500.Charpy impact tests and a combination of multiscale characterizations were conducted to investigate the influence of various microstructural features on impact toughness and crack initiation behavior.The results prove that, as the heat input increases, the number of M/A components increases, thereby degrading toughness and increasing hardness.Meanwhile, more M/A constituents tend to aggregate on prior austenite grain boundaries(PAGBs),and the overall dimensions of M/A and the width and volume fraction of the lath martensite substructure inside M/A islands would increase as well.These changes make intersections between boundary M/As and PAGBs become one of the preferred sites for crack initiation.In addition, only large-sized grotesque inclusions can act as a direct inducement of crack initiation. 展开更多
关键词 X80 pipeline steel coarse grain heat-affected zone microstructural features impact toughness crack initiation
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Microstructure and toughness of coarse grain heat-affected zone for Nb-microalloyed X80 pipeline steel 被引量:1
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作者 李亚娟 李午申 陈仁华 《China Welding》 EI CAS 2011年第4期57-61,共5页
Based on welding thermal simulation on Nb-microaUoyed XSO pipeline stee! using Gleeble-3500 thermal simulation equipment, microstlttcture and impact toughness in coarse grain heat-affected zone (CGHAZ) under differe... Based on welding thermal simulation on Nb-microaUoyed XSO pipeline stee! using Gleeble-3500 thermal simulation equipment, microstlttcture and impact toughness in coarse grain heat-affected zone (CGHAZ) under different welding parameters were investigated in this paper. The results show that high heat inputs with low preheats or low heat inputs with high preheats should be applied to achieve high impact toughness. Coarse original austenite grains may lower impact toughness. CGHAZ microstructure is mostly composed of upper bainite, granular bainite and lath bainite. The phase composition of microstructure and the quantity, size, shape of M/A constituents both have effects on impact toughness. 展开更多
关键词 Nb-microalloyed XSO pipeline steel heat-affected zone MICROSTRUCTURE TOUGHNESS
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The softening prediction of HSLA steel heat-affected zone based on the grey system 被引量:1
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作者 赵璇 代克杰 杜泽国 《China Welding》 EI CAS 2012年第2期69-72,共4页
The high-strength low-alloy( HSLA ) steel heat-affected zone (HAZ)softening was predicted using a grey model. HSLA steel DILLIMAX690E, NK-HITEN61OU2 and BHW35 were taken as examples in the research on ultra-narrow... The high-strength low-alloy( HSLA ) steel heat-affected zone (HAZ)softening was predicted using a grey model. HSLA steel DILLIMAX690E, NK-HITEN61OU2 and BHW35 were taken as examples in the research on ultra-narrow gap automatic welding technology. Test results turned out to be that the errors between the values calculated by the Grey Model (GM) ( 1,1 ) model and their actual value were less than 2%, indicating that the grey prediction method could accurately reflect the actual situation of the high-strength low-alloy steel heat-affected zone softening. This method will play a crucial role in guiding the applications of HSLA steel welded structures in the future. 展开更多
关键词 grey prediction GM 1 1 model heat-affected zone SOFTENING
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Heat-affected zone in pulsed laser cutting of titanium alloy
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作者 王扬 吕善进 裴剑英 《中国有色金属学会会刊:英文版》 CSCD 2005年第S3期264-267,共4页
For the machining of bladed ring parts of an aeroengine, experiments on Nd∶YAG pulsed laser cutting of TC1 titanium alloy sheet were carried out to investigate the influences of laser cutting parameters on heat-affec... For the machining of bladed ring parts of an aeroengine, experiments on Nd∶YAG pulsed laser cutting of TC1 titanium alloy sheet were carried out to investigate the influences of laser cutting parameters on heat-affected zone (HAZ). The selected laser cut samples were photographed by scanning electron microscopy. The results show that the microstructure in HAZ layers is characterized by metastable acicular martensite grains with a slight increase of hardness by 10%. The thickness of HAZ layers was studied as a function of laser cutting parameters. Medium pulse energy, higher pulse rate, higher cutting speed and argon at higher pressures help to reduce the thickness of HAZ layers. 展开更多
关键词 laser CUTTING TITANIUM alloy SCANNING electron MICROSCOPE heat-affected zone
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High-temperature creep properties of fine grained heat-affected zone in P92 weldment
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作者 王学 史专 +1 位作者 潘乾刚 吴洪亮 《中国有色金属学会会刊:英文版》 CSCD 2009年第S3期772-775,共4页
The simulated fine grained heat-affected zone (FGHAZ) specimens for P92 welded joints were prepared by heat treatment, then the creep tests were carried out at 650 ℃ under the applied stress of 90-120 MPa to investig... The simulated fine grained heat-affected zone (FGHAZ) specimens for P92 welded joints were prepared by heat treatment, then the creep tests were carried out at 650 ℃ under the applied stress of 90-120 MPa to investigate high-temperature creep behavior of FGHAZ. The results show that the creep property of FGHAZ is much inferior to that of the base metal, which exhibits the much higher steady creep rate and shorter time to creep fracture. The power law equation can describe the steady creep rate dependence on applied stress, indicating that the stress exponent n of FGHAZ is distinguished between two regions with n=15.1 at high stresses (more than 100 MPa) and n=8.64 at lower stresses. Based on Monkman-Grant equation, the relationship between the secondary creep rate and time to rupture is obtained to evaluate the creep life of FGHAZ with the applied stress above 100 MPa. 展开更多
关键词 RESISTANT heat steel welding FINE grained heat-affected zone(FGHAZ) CREEP
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Effect of Zr-Ti combined deoxidation on impact toughness of coarse-grained heat-affected zone with high heat input welding
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作者 万响亮 吴开明 +2 位作者 王红鸿 卢伟煜 成林 《China Welding》 EI CAS 2014年第4期56-62,共7页
In this study, the effects of Zr-Ti combined deoxidation and AI deoxidation on the impact toughness of coarse- grained heat-affected zone in high-strength low-alloy steels were investigated. More fine oxides were form... In this study, the effects of Zr-Ti combined deoxidation and AI deoxidation on the impact toughness of coarse- grained heat-affected zone in high-strength low-alloy steels were investigated. More fine oxides were formed in the Zr-Ti-killed steel than in Al-killed steel. It was also found that more acicular ferrite grains were formed in the coarse-grained heat-affected zone in the Zr-Ti-killed steel than in Al-killed steel. The impact toughness of coarse-grained heat-affected zone of Zr-Ti-kiUed steel was higher than that of Al-killed steel. The good impact toughness was attributable to the pinning effect of fine oxides and the formation of acicular ferrite grains on fine oxides. 展开更多
关键词 STEELS heat-affected zone high heat input welding TOUGHNESS DEOXIDATION
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Study on laser welded heat-affected zone in new ultralow carbon bainitic steel
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作者 Lin Zhao Wuzhu Chen +1 位作者 Xudong Zhang Jiguo Shan 《Journal of University of Science and Technology Beijing》 CSCD 2007年第2期136-140,共5页
800 MPa grade ultralow carbon bainitic (NULCB) steel is the recently developed new generation steel, which was produced by thermo mechanical controlled processing & relaxation-precipitation controlling transformati... 800 MPa grade ultralow carbon bainitic (NULCB) steel is the recently developed new generation steel, which was produced by thermo mechanical controlled processing & relaxation-precipitation controlling transformation (TMCP&RPC) tech- nique. The microstructure and the mechanical properties of the heat-affected zone (HAZ) in NULCB steel under laser welding conditions were investigated by using a Gleeble-1500 thermal simulator. The experimental results indicate that the simplex microstructure in the HAZ is granular bainite that consists of bainite-ferrite (BF) lath and M-A constituent when the cooling time from 800 to 500℃ (t8/5) is 0.3-30 s, and the M-A constituent consists of twinned martensite and residual austenite. As t8/5 increases, the hardness and tensile strength of HAZ decreases, but they are higher than that of the base metal, indicating the absence of softened zone after laser welding. The impact toughness of HAZ increases at first and then decreases when t8/5 increases. The impact energy of HAZ is much higher than that of the base metal when t8/5 is between 3 and 15 s. It indicates that excellent low temperature toughness can be obtained under appropriate laser welding conditions. 展开更多
关键词 ultralow carbon bainitic steel laser welding heat-affected zone MICROSTRUCTURE mechanical properties
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Study on local embrittlement of welding heat-affected zone in XSO pipeline steels
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作者 郝世英 高惠临 +1 位作者 张骁勇 周勇 《China Welding》 EI CAS 2011年第2期36-40,共5页
The relationship between the microstructure and toughness of welding heat-affected zone in XSO grade pipeline steels is studied. It is found that the intercritical reheated coarse-grained heat-affected zone (ICCGHAZ... The relationship between the microstructure and toughness of welding heat-affected zone in XSO grade pipeline steels is studied. It is found that the intercritical reheated coarse-grained heat-affected zone (ICCGHAZ) of experimental steels has the lowest toughness values when the secondary peak temperature is at intercritical ( α + γ ) region during multi-pass welding. The local embrittlement is mainly attributed to the morphology, amount and size of M-A constituent. It is also found that the microstructural inhabitanee at ICCGHAZ has a deleterious effect on the toughness. On the basis of above experimental results, it is suggested that the local embrittlement should be prevented by using pre-heating thermal cycle which could eliminate the microstructural inhabitance and using post-heating thermal cycle which could improve the morphology, amount and size of MA constituent. 展开更多
关键词 X80 pipeline steel MICROSTRUCTURE coarse-grain heat-affected zone local embrittlement
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Simulation research on heat-affected zone of the NiTi alloy plasma arc welded joints
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作者 徐越兰 张俊 王飞 《China Welding》 EI CAS 2009年第1期43-46,共4页
In order to study the compositions and properties of NiTi alloy plasma arc welded joints, different temperatures of the heat-affected zone(HAZ) are simulated. Temperatures are set at 20 ℃, 400 ℃, 500 ℃, 600 ℃, 7... In order to study the compositions and properties of NiTi alloy plasma arc welded joints, different temperatures of the heat-affected zone(HAZ) are simulated. Temperatures are set at 20 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃ and 1 000 ℃. X-ray diffraction results of the thermal simulated specimens show that NiTi2 phase emerges in the alloy when the temperature is between 500 ℃ and 800 ℃, while NiTi2 and Ni3 Ti phases emerge when the temperature is between 800 ℃ and 1 000 ℃. Tensile strengths of specimens at 600 ℃ and 900 ℃ are only 68. 0% and 61.3% of the strength at the room temperature respectively due to the emergence of NiTi2 and Ni3 Ti phases. 展开更多
关键词 NiTi alloy plasma arc heat-affected zone
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Influence of the secondary welding thermal cycle on the microstructure and property of coarse grain heat-affected zone in an X100 pipeline steel
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作者 张骁勇 高惠临 +1 位作者 吉玲康 庄传晶 《China Welding》 EI CAS 2010年第3期25-30,共6页
The influence of the secondary thermal cycle on the microstructure of coarse grain heat-affected zone in an XIO0 pipeline steel was investigated by means of a thermal simulation technique and microscopic analysis meth... The influence of the secondary thermal cycle on the microstructure of coarse grain heat-affected zone in an XIO0 pipeline steel was investigated by means of a thermal simulation technique and microscopic analysis method. The property of coarse grain heat-affected zone was characterized by Charpy V-Notch impact properties testing. The results indicated that the experimental steel exhibited local brittleness of intercritically reheated coarse-grained heat-affected zone when the peak tempera- ture of secondary thermal cycle was in the range of two phases region ( ~ and 3/). There were two main reasons for the local brittleness. The first was that the microstructures of intercritically reheated coarse-grained heat-affected zone were not fined although partial grain recrystallization occurred. The second was that M-A islands, which had the higher content, larger size and higher hardness, existed in intercritically reheated coarse-grained heat-affected zone. 展开更多
关键词 X100 pipeline steel secondary thermal cycle MICROSTRUCTURE coarse grain heat-affected zone
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Effects of Electrode Types on the Microstructure, Tensile and Hardness Properties of 304 L Austenitic Stainless Steel Heat-Affected Zone (HAZ)
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作者 Bolarinwa Johnson Kutelu Emmanuel Gbolade Adubi Saliu Ojo Seidu 《Journal of Minerals and Materials Characterization and Engineering》 2018年第5期531-540,共10页
Submerged arc welding (SAW) has been well utilised for the production of weld joints in 304 L ASS for various industrial application. However, effective performance of the material in service has been hampered by impr... Submerged arc welding (SAW) has been well utilised for the production of weld joints in 304 L ASS for various industrial application. However, effective performance of the material in service has been hampered by improper choice of electrode. Therefore, in this study, effects of different types of electrode on the microstructure and tensile property of type 304 L austenitic stainless steel heat-affected zone (HAZ) were studied. Chemical composition of the as-received sample was determined. A number of samples were cut from the as-received sample. Afterwards, two half were joined together with 308 L, 312 L and 316 electrodes at a controlled welding speed, current and voltage of 4.6 mm/s, 160 A and 30 V to produce a constant heat input of 626.09 J/mm. An automatic SAW machine with Model Type: DX3-301, and Frequency: 50 Hz was used. And based on ASTM standard, tensile and hardness samples were prepared from the as-received and HAZs. Tensile and hardness measurements were made. Also, specimens for microscopy studies were prepared from the HAZ and as-received samples. From the results, microstructures of the HAZs revealed varied volume fraction of austenite and ferrite phases and grain sizes, and at austenite and ferrite grain boundaries, chromium carbide formation and precipitation were observed. The weld joint produced with 308 L electrode revealed optimum UTS value and YS value of 475 and 325 respectively. While weld joint produced with 316 L electrode has superior ductility of value 41%. Irrespective of the types of electrode used, the as-received sample revealed superior tensile properties over the weld joints. Also, optimum hardness value of 45.7 HRA was obtained with 308 L. Hardness value of the as-received sample was higher than that of HAZ samples. 展开更多
关键词 heat-affected zone STAINLESS Steel Volume FRACTION Microstructures HARDNESS TENSILE
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Changes in microstructure and properties of weld heat-affected zone of high-strength low-alloy steel
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作者 Shu-jun Jia Qi-lin Ma +3 位作者 Yu Hou Ba Li He-song Zhang Qing-you Liu 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2024年第8期2041-2052,共12页
The evolution of the microstructure and toughness of APL5L X80 pipeline steel after thermal welding simulation was investigated by X-ray diffraction,electron backscatter diffraction,and transmission electron microscop... The evolution of the microstructure and toughness of APL5L X80 pipeline steel after thermal welding simulation was investigated by X-ray diffraction,electron backscatter diffraction,and transmission electron microscopy.The results indicated that primary heat-affected zones can be divided into weld,coarse-grained,fine-grained,intercritical,and sub-critical zones.The microstructure of the weld zone is mainly composed of bainitic ferrite and a small amount of granular bainite;however,the original austenite grains are distributed in the columnar grains.The structure of the coarse-grained zone is similar to that of the weld zone,but the original austenite grains are equiaxed.In contrast,the microstructure in the fine-grained zone is dominated by fine granular bainite,and the effective grain size is only 8.15μm,thus providing the highest toughness in the entire heat-affected zone.The intercritical and subcritical zones were brittle valley regions,and the microstructure was dominated by granular bainite.However,the martensite-austenite(M/A)constituents are present in island chains along the grain boundaries,and the coarse size of the M/A constituents seriously reduces the toughness.The results of the crack propagation analyzes revealed that high-angle grain boundaries can significantly slow down crack growth and change the crack direction,thereby increasing the material toughness.The impact toughness of the low-temperature tempering zone was equivalent to that of the columnar grain zone,and the impact toughness was between those of the critical and fine-grained zones. 展开更多
关键词 Welding thermal simulation Impact toughness Crack propagation Martensite-austenite constituent High-strength low-alloy steel weld heat-affected zone
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Impact Toughness of Heat-Affected Zones of 11Cr Heat-Resistant Steels 被引量:2
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作者 Yongkui Li Jianxin Lou +1 位作者 Hongtao Ju Li Lin 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2020年第6期821-827,共7页
Aiming at the requirements of structural steel in Gen-IV nuclear reactor, the high-chromium martensitic heat-resistant steels containing 10–12% chromium were developed. The toughness of heat-affected zones(HAZs) is o... Aiming at the requirements of structural steel in Gen-IV nuclear reactor, the high-chromium martensitic heat-resistant steels containing 10–12% chromium were developed. The toughness of heat-affected zones(HAZs) is one of the important factors for evaluating the weldability of steels. In this paper, the simulated HAZs were fabricated using tempered SIMP steels. The effects of microstructures on the impact toughness of materials were analyzed using Vickers hardness tester, optical microscope, transmission electron microscope. Experimental results demonstrated that the HAZs of weldment were poor in toughness, much lower than that of the base metal. However, after experiencing post-weld heat treatment, the toughness of the HAZs increased greatly. The toughness became better in terms of CG-HAZ, FG-HAZ and IC-HAZ for the two steels, regardless of as-welded or after PWHT. Compared with SIMP7 steel, chemical compositions, such as C, Si, Mn and Cr, were adjusted to a lower content;the toughness of base metal and simulated HAZs was better in the case of SIMP11. The conjunct roles of dislocation density and carbon contents retained in the martensite led to poor impact toughness of the aswelded HAZs, because dislocations and carbon atoms affected the inner stresses within lattices. 展开更多
关键词 High-CrF/M heat-resistant steel heat-affected zones Impact toughness Carbide precipitations
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Microstructure and Mechanical Properties of Simulated Heat-affected Zones of EP-823 Steel for ADS/LFR 被引量:1
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作者 Shanping Lu Tian Liang +3 位作者 Yongkui Li Dianzhong Li Lijian Rong Yiyi Li 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2015年第8期864-871,共8页
EP-823 steel is one of the candidate materials for accelerator-driven systems/lead-cooled fast reactors (ADS/LFR). Its weldability was investigated by mechanical property tests and microstructure analysis on the enl... EP-823 steel is one of the candidate materials for accelerator-driven systems/lead-cooled fast reactors (ADS/LFR). Its weldability was investigated by mechanical property tests and microstructure analysis on the enlarged heat-affected zones (HAZs) made by numerical and physical simulation. The finite element numerical simulation could simulate the welding thermal cycle of the characteristic regions in HAZs with extremely high accuracy, The physical simulation performed on a Gleeble simulator could enlarge the characteristic regions to easily investigate the relationship between the microstructure evolution and the mechanical properties of the HAZs. The results showed that the simulated partially normalized zone comprising tempered martensite, newly formed martensite and more tiny carbides has the highest impact energy. The fully normalized zone exhibits the highest hardness because of the quenched martensite and large carbides. The ductile property of the overheated zone is poor for the residual delta- ferrite phases and the quenched martensite. 展开更多
关键词 Accelerator-driven systems/lead-cooled fast reactors (ADS/LFR) EP-823 steel heat-affected zones (HAZs) Microstructure evolution Mechanical property
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