Xiaochun SHA
,
Chunli MO
,
Dianzhong LI
,
Yiyi LI
材料科学技术（英文）
Based on hot rolling production line of strip steel, the off-line in-house software, termed as ROLLAN (Rolling Analysis), is developed. The code is mainly used to predict the evolution of temperature, rolling force, fraction and grain size of recrystallization, fraction and grain size of phase transformation and final mechanical properties. Almost all the processing parameters affecting microstructure and mechanical properties in the schedule from reheating to the coiling process are considered in detail. Self-learning coefficient is adopted to adjust the deviation between predicted and measured temperatures, such as roughing exit temperature (RT2), finishing exit temperature (FT7) and coiling temperature (CT). Due to the application of low-speed-threading, increasing-speed-rolling and decreasing-speed-delivery process during finishing rolling and different cooling condition, after coiling the thermal-mechanical history of different position, along strip longitudinal direction is different resulting in inhomogeneous mechanical properties. So the segments are divided along longitudinal direction to identify the variation of microstructure and mechanical properties. An example of plain carbon strip steel Q235 with various thickness is used to compare the calculated mechanical properties with measured ones. For the specific grade of Q235 , the maximum deviation of tensile strength is less than 10.3 MPa, the yield strength is less than 13.2 MPa, and elongation is less than 1.99%. Further work will focus on the on-line application and consider the effect of macrosegregation and sulfur content of cast slab.
关键词:
Microstructural evolution
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null
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null
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null
Y.H.Zhu
材料科学技术（英文）
Furnace cooling is a slow cooling process. It is of importance to study structural evolution and its effects on the properties of alloys during the furnace cooling. Decomposition of aluminium rich α phase in a furnace cooled eutectoid Zn-Al based alloy was studied by transmission electron microscopy. Two kinds of precipitates in the α phase were detected in the FCZA22 alloy during ageing at 170℃. One was the hcp transitional α′m phase which appears as directional rods and the round precipitates. The other was the fcc α′′m phase. It was found that the transitional phaseα′m grew in three preferential directions of <110>, <011> and <101>. The orientation relationship between the α phase and transitional phase α′m was determined as , . The non-equilibrium phase decomposition of the α phase is discussed in correlation with the equilibrium phase relationships. (02-2) 'm (fcc)// (02-2) (fcc) , [-111] 'm (fcc)// [-233] (fcc).
The non-equilibrium phase decomposition of the phase is discussed in correlation with the equilibrium phase relationships.
关键词:
Phase decomposition
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decomposition
,
microstructural
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evo
Wantang FU
,
Yi XIONG
,
Jun ZHAO
,
Yong LI
,
T.Furuhara
,
T.Maki
材料科学技术（英文）
The microstructural evolution of pearlite during severe cold rolling in Fe-0.8C binary alloy and Fe-1Mn-0.8C ternary alloys was investigated by using SEM, TEM and XRD etc. The results show that the deformed pearlite consists of irregularly bent lamella, coarse lamella with shear-band and fine lamella. As the rolling reduction increases, the proportion of fine lamella increases. The strong plastic deformation, amorphization and dissolution of cementite take place during the severe cold rolling. The maximum carbon content in ferrite reaches 0.15 mass% after 90% cold rolling.
关键词:
Pearlite
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null
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null
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null
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null
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null
Yan ZHAO
金属学报(英文版)
Microstructural evolution and the change in hardness during creep deformation of NF709 austenitic stainless steel were investigated. Creep tests were carried out at 650 ℃ for 2932 h under a load of 210 MPa for comparison with aging specimen at 650 ℃ for 3000~h. The hardness results indicated that applied stress during creep process induced hardness increase. Analysis of longitudinal section microstructure showed that the creep damage caused by pores and the grain boundary hardening caused by elongated grains could be the factors leading to hardness differences. The G phase dispersedly precipitated in intragranular and interacted with dislocations during creep process, indicating strain hardening.
关键词:
NF709
Lihui ZHU
,
Xueming MA
材料科学技术（英文）
2.25Cr-1.6W-V-Nb developed in Japan, is a low alloy heat resistant steel with good comprehensive properties. Influence of long term creep at elevated temperature on the structure of 2.25Cr-1.6W-V-Nb steel was studied in this paper, and the micromechanism of creep strength degradation was elucidated, too. Both TEM observation and thermodynamic calculation reveal that during creep the transformation occurs from M7C3 and M23C6 to M6C, which can be cavity nucleation sites. Besides, creep at 600℃ also leads to the decrease of dislocation density, the coarsening and coalescence of M23C6, the nucleation of cavities and development of cracks. The strength decrease of 2.25Cr-1.6W-V-Nb steel after long term creep is related to the decrease of dislocation hardening, precipitation hardening, solution hardening, the nucleation of cavities and development of cracks.
关键词:
Heat resistant steel
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null
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null
