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Hyo Kyung Sung Sang Yong Shin Byoungchul Hwang Chang Gil Lee Sunghak Lee 《Metallurgical and Materials Transactions A》2013,44(1):294-302
In this study, four low-carbon high-strength bainitic steel specimens were fabricated by varying finish cooling temperatures and cooling rates, and their tensile and Charpy impact properties were investigated. All the bainitic steel specimens consisted of acicular ferrite, granular bainite, bainitic ferrite, and martensite-austenite constituents. The specimens fabricated with higher finish cooling temperature had a lower volume fraction of martensite-austenite constituent than the specimens fabricated with lower finish cooling temperature. The fast-cooled specimens had twice the volume fraction of bainitic ferrite and consequently higher yield and tensile strengths than the slow-cooled specimens. The energy transition temperature tended to increase with increasing effective grain size or with increasing volume fraction of granular bainite. The fast-cooled specimen fabricated with high finish cooling temperature and fast cooling rate showed the lowest energy transition temperature among the four specimens because of the lowest content of coarse granular bainite. These findings indicated that Charpy impact properties as well as strength could be improved by suppressing the formation of granular bainite, despite the presence of some hard microstructural constituents such as bainitic ferrite and martensite-austenite. 相似文献
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中低碳含硅空冷贝氏体钢的冲击韧性 总被引:10,自引:2,他引:8
研究了新设计的含硅中低碳空冷贝氏体钢的热处理工艺与冲击韧性。研究发现,该钢经连续冷却获得的贝-马复相组织具有高的韧性。经300℃回火后,钢的冲击韧性可达到96J/cm^2,其韧性高于同一温度回火的马氏体组织。硅将回火脆性温度推向高温。钢中出现粗大的魏氏组织时使钢的冲击韧性显著降低。 相似文献
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Yongjoon Kang Gitae Park Seonghoon Jeong Changhee Lee 《Metallurgical and Materials Transactions A》2018,49(1):177-186
A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal. 相似文献
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LI Feng-zhao AO Qing QIN Chao JIANG Jiang LIU Yu-xian MENG Xiang-min HE Lian-long 《钢铁研究学报(英文版)》2003,10(2)
Asbainiticsteelspossesshighhardness ,highstrength toughness ,highwearresistanceandhighhardenability ,theacademicandengineeringcircleshavepaidcloseattentiontotheinvestigationoffinemicrostructure[1,2 ] .However ,thefinemicrostruc tureofbainiticsteelsisnotdeterminedyet .Thefinemicrostructuresofmediumandmedium highcarbonbainiticsteelswereobservedandanalyzedbyhighresolutionelectronmicroscope (HREM ) ,andthere sultsshowthatthereareretainedausteniticfilmsatdifferentlevelstructureunitboundaries .The… 相似文献
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Microstructure,Tensile and Impact Toughness Properties of Friction Stir Welded Mild Steel 总被引:3,自引:0,他引:3
Microstructure, tensile and impact toughness properties and fracture location of friction stir welded AISI 1018 mild steel are revealed in this paper. The 5 mm thick AISI 1018 mild steel plates were friction stir welded with tool rotational speed of 1000 rpm and welding speed of 50 mm/min with tungsten base alloy tool. Tensile strength of stir zone is higher (8%) when compared to the base metal. This may be due to the formation of finer grains in the weld nugget region under the stirring action of the rotating tool. The ductility and impact toughness of the joints are decreased compared to the base metal and this is due to the inclusion of tungsten particles in the weld region. 相似文献
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Shajan Nikhil Arora Kanwer Singh Asati Brajesh Sharma Vikram Shome Mahadev 《Metallurgical and Materials Transactions A》2018,49(4):1276-1286
Metallurgical and Materials Transactions A - Effect of post-weld heat treatment on the weld microstructure, texture, and its correlation to the toughness of flash butt welded joints were... 相似文献
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Hyo Kyung Sung Sang Yong Shin Byoungchul Hwang Chang Gil Lee Nack J. Kim Sunghak Lee 《Metallurgical and Materials Transactions A》2011,42(7):1827-1835
Six ultra-low-carbon high-strength bainitic steel plates were fabricated by controlling rolling and cooling conditions, and
effects of bainitic microstructure on tensile and Charpy impact properties were investigated. The microstructural evolution
was more critically affected by start cooling temperature and cooling rate than by finish rolling temperature. Bainitic microstructures
such as granular bainites (GBs) and bainitic ferrites (BFs) were well developed as the start cooling temperature decreased
or the cooling rate increased. When the steels cooled from 973 K or 873 K (700 °C or 600 °C) were compared under the same
cooling rate of 10 K/s (10 °C/s), the steels cooled from 973 K (700 °C) consisted mainly of coarse GBs, while the steels cooled
from 873 K (600 °C) contained a considerable amount of BFs having high strength, thereby resulting in the higher strength
but the lower ductility and upper shelf energy (USE). When the steels cooled from 673 K (400 °C) at a cooling rate of 10 K/s
(10 °C/s) or 0.1 K/s (0.1 °C/s) were compared under the same start cooling temperature of 873 K (600 °C), the fast cooled
specimens were composed mainly of coarse GBs or BFs, while the slowly cooled specimens were composed mainly of acicular ferrites
(AFs). Since AFs had small effective grain size and contained secondary phases finely distributed at grain boundaries, the
slowly cooled specimens had a good combination of strength, ductility, and USE, together with very low energy transition temperature
(ETT). 相似文献
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低碳贝氏体钢的组织类型及其对性能的影响 总被引:12,自引:2,他引:12
低碳贝氏体钢受控冷工艺的影响会得到不同类型的组织,在较慢速冷却时,在奥氏体中先形成针状铁素体,残余奥氏体会被包裹在铁素体之中,形成粒状贝氏体团。工业轧制试验表明.不同控制冷却工艺可得到两类组织,一类出现黑珠组织(富碳马氏体组织).具有该组织的钢轧态冲击韧性低。另外一类为细化的板条贝氏体组织,具有该组织的钢轧态强度高,冲击韧性好,但伸长率不足。通过回火处理,存在黑珠组织钢的冲击韧性能得到提高,超细化板条贝氏体组织钢的伸长率也能得到改善,但后者屈服强度会比前者高100MPa左右。 相似文献
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Vorkachev K. G. Stepanov P. P. Éfron L. I. Kantor M. M. Chastukhin A. V. Zharkov S. V. 《Metallurgist》2021,64(9-10):875-884
Metallurgist - A simulated coarse-grained heat affected zone microstructure formation mechanism is established in high strength low alloy steels using electron backscatter diffraction (EBSD). The... 相似文献
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Metallurgist - A promising martensitic steel with good hardenability is studied. In the cooling rate range 0.1–30°C/sec and the only transformation recorded by a dilatometer starts at an... 相似文献
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A low carbon bainitic steel with microstructure of granular bainite (GB), acicular ferrite (AF), and bainitic ferrite (BF) is obtained under different deformation and cooling rate. The effect of deformation and cooling rate on microstructural characteristics such as the type of the matrix, the size, and area fraction of the martensite–austenite (M–A) constituents is investigated. In addition, the nanohardness of these three kinds of matrix as well as that of the M–A constituents in them is characterized. Further, the effect of matrix and M–A constituents on strength–toughness balance is studied. Results indicate that deformation expands the transformation region. The size as well as the area fraction of the M–A constituent decreases with the increasing of the cooling rate. After deformation, the area fraction of the M–A constituents increases. Nanohardness of GB, AF, and BF increases orderly, but that of the M–A constituents in them decreases accordingly. The nanohardness of the M–A constituent is significantly affected by its carbon concentration. AF is the optimum microstructure having superior strength–toughness balance. 相似文献
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Onur Saray Gencaga Purcek Ibrahim Karaman Hans J. Maier 《Metallurgical and Materials Transactions A》2012,43(11):4320-4330
Impact toughness of an ultrafine-grained (UFG) interstitial-free (IF) steel produced by equal-channel angular extrusion/pressing (ECAE/P) at room temperature was investigated using Charpy impact tests. The UFG IF steel shows an improved combination of strength and impact toughness compared with the corresponding coarse-grained (CG) one. The CG IF steel samples underwent a transition in fracture toughness values with decreasing temperature because of a sudden change in fracture mode from microvoid coalescence (ductile) to cleavage (brittle) fracture. Grain refinement down to the submicron (??320?nm) levels increased the impact energies in the upper shelf and lower shelf regions, and it considerably decreased the ductile-to-brittle transition temperature (DBTT) from 233?K (?40?°C) for the CG steel to approximately 183?K (?90?°C) for the UFG steel. Also, the sudden drop in DBTT with a small transition range for the CG sample changed to a more gradual decrease in energy for the UFG sample. The improvement in toughness after UFG formation was attributed to the combined effects of grain refinement and delamination and/or separation in the heavily deformed microstructure. Although an obvious change from the ductile fracture by dimples to the brittle fracture by cleavage was recognized at 233?K (?40?°C) for the CG steel, no fully brittle fracture occurred even at 103?K (?170?°C) in the UFG steel. 相似文献
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Tao Jia Yanlei Zhou Xiaoxiao Jia Zhaodong Wang 《Metallurgical and Materials Transactions A》2017,48(2):685-696
Investigation on the correlation between microstructure and CVN impact toughness is of practical importance for the microstructure design of high strength microalloyed steels. In this work, three steels with characteristic microstructures were produced by cooling path control, i.e., steel A with granular bainite (GB), steel B with polygonal ferrite (PF) and martensite-austenite (M-A) constituent, and steel C with the mixture of bainitic ferrite (BF), acicular ferrite (AF), and M-A constituent. Under the same alloy composition and controlled rolling, similar ductile-to-brittle transition temperatures were obtained for the three steels. Steel A achieved the highest upper shelf energy (USE), while large variation of impact absorbed energy has been observed in the ductile-to-brittle transition region. With apparently large-sized PF and M-A constituent, steel B shows the lowest USE and delamination phenomenon in the ductile-to-brittle transition region. Steel C exhibits an extended upper shelf region, intermediate USE, and the fastest decrease of impact absorbed energy in the ductile-to-brittle transition region. The detailed CVN impact behavior is studied and then linked to the microstructural features. 相似文献
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试验用空冷低碳贝氏体钢DB590(%:0.06C、0.92Mn、0.49Mo、0.65Cr、0.02Nb、0.08V、0.001 0B)由50 kg真空感应炉熔炼、铸成22 kg锭、锻成(mm)100×100×150钢坯,并控制轧成16 mm板,空冷。通过Gleeble 1500热模拟机得出该钢的CCT曲线。DB590钢轧后空冷(3℃/s)的组织为贝氏体+铁素体基体,钢板的抗拉强度645 MPa,屈服强度471 MPa,伸长率32%,0℃冲击功94 J以及优良的冷弯性能。 相似文献