Wuxiao WANG
,
Bailing JIANG
,
Sen YUAN
,
Wanqi JIE
材料科学技术（英文）
The liquid quenching method was adopted to study the solidification morphology and microstructure of AZ91D Mg alloy in semisolid. The results indicate that cooling rate has important effects upon the solidification structures. Under the cooling rate of liquid quenching, primary α-phase grows first by attaching on the original α grains, or independent nucleation and growth. The high cooling rate makes primary α-phase grow in "rags" or dendrite shape. Eutectic solidification is carried out in terms of both dissociated growth and symbiotic growth. The dissociated growth forms rough and large β-phase at grain boundaries, while symbiotic growth forms eutectic of laminar structure. The small liquid pool inside the original α-phase solidifies basically in the same way as that of intergranular liquid, but owing to less amount of liquid phase, the eutectic solidification is mainly carried out in the dissociated pattern.
关键词:
Magnesium alloy
,
液淬
,
凝固方式
,
凝固组织
Jinfeng XU
,
Qiuya ZHAI
,
Sen YUAN
材料科学技术（英文）
Energy-storage welding connection characteristics of rapidly solidified AZ91D Mg alloy ribbons with 40~70 μm thickness are investigated using a microtype energy-storage welding machine. The microstructure and performance of the connection joints are analyzed and studied. The research results indicate that energy-storage welding is able to realize the spot welding connection of AZ9ID Mg alloy ribbons. The welding nugget consists of developed α-Mg equiaxed grains with the sizes of 1.2~2.7 μm and intergranular distributed β-Mg17Al12 compounds. The thickness of bond zone is about 4 μm and the solidification microstructure is characterized by the fine equiaxed grains with the sizes of 0.8~1.2 μm, and grain boundary has become coarsening. The columnar crystal in HAZ also becomes slightly coarsening and the grain boundary has broadened, however, there is no obvious change in its primitive morphology and crystallographic direction. When welding energy is about 2.0 J, the welding joints with higher shear strength and smaller electrical resistivity are obtained.
关键词:
AZ91D
,
null
,
null
,
null
,
null
WU Su-zhou
,
ZHANG Jiong-ming
,
LI ZHi-zheng
钢铁研究学报(英文版)
The SEN clogging is a long term issue for all the steelmakers. In the current study, the kinetics of SEN clogging during steel continuous casting was established. The dynamic build-up of alumina inclusions to the lining refractory of SEN was analyzed. The fluid flow and inclusions motion are calculated by means of mathematic model. Effect of diameters of inclusions, roughness of nozzle, diameter of nozzle and casting speed on the entrapment probability are estimated.
关键词:
nozzle clogging;mathematic model;inclusion motion
B.W. Li
,
X.Y. Tian
,
E.G. Wang
,
J.C. He
,
null
,
null
,
null
,
null
金属学报(英文版)
In recent years, thin slab continuous casting technology has been widely used to improve the quality of the product and to reduce
the cost. One of the challenges faced by this technology is to design reasonable flow patterns, which strongly affect the surface
and inner properties of the final slab in the mold. With the fixed scales and complex geometrical structures of nozzle and funnel
type mold, a series of numerical simulations are made to analyze the flow patterns in melt steel using finite volume method based
on structured body fitted coordinate grids. The CFD (computational fluid dynamics) package is validated first using one typical case described in previously published studies, and then it is developed to study the effect of operational parameters on fluid
flow in thin slab caster. Two operational parameters, casting speed and SEN depth (submerged entry nozzle), are mainly
considered for numerical analysis. On the basis of present simulations, the reasonable SEN submergence depths corresponding to different casting speeds are suggested according to fluid flow characteristics like, flow jet impingement on the narrow side of
the mold, flow speed of the melt steel beneath the meniscus and the recirculation region. This is the first stage of study on the numerical analysis of the whole thin slab casting process with electromagnetic brake.
关键词:
continuous casting
,
null
,
null
王翠娜 温良英 陈登福 张大江 彭政 靳星
钢铁
针对某钢厂板坯连铸结晶器及浸入式水口(SEN)的结构参数，建立了描述结晶器内钢液流动的三维数学模型，用FLUENT软件对结晶器内钢液的流场和温度场进行耦合计算，分析SEN底部形状对结晶器内流场和温度场的影响。结果表明：凸底水口出口附近钢液的速度较大，对结晶器窄面的冲击深度较大，使结晶器内高温区下移，不利于凝固坯壳的生长；平底水口自由面速度较大、温度较高，有利于保护渣的熔化，但易产生液面裸露现象；凹底自由面速度较小、温度较低，有利于液面稳定。
关键词:
浸入式水口（SEN）;底部形状;结晶器;流场;温度场
王翠娜
,
温良英
,
陈登福
,
张大江
,
彭政
,
靳星
钢铁
针对某钢厂板坯连铸结晶器及浸入式水口(SEN)的结构参数,建立了描述结晶器内钢液流动的三维数学模型,应用FLUENT软件对结晶器内钢液的流场和温度场进行耦合计算,分析SEN底部形状对结晶器内流场和温度场的影响,并利用水模试验对钢液的流动行为进行了验证.结果表明:凸底水口出口附近钢液的速度较大,流股的冲击深度较大,使结晶器内高温区下移,不利于凝固坯壳的生长;平底水口自由面速度较大、温度较高,有利于保护渣的熔化,但易产生液面裸露现象;凹底自由面速度较小、温度较低,有利于液面稳定.
关键词:
浸入式水口
,
底部形状
,
结晶器
,
流场
,
温度场
Y.P.Du
金属学报(英文版)
According to turbulent theory and characteristics of beam blank continuous casting, 3-D model to represent the flow of beam blank mould is established. The predicted results indicate that the exit obliquity of up 15°(+15°) should be adopted, which will benefit the floatation of non-metallic inclusion and purification of the molten steel. When the nozzle angle is 120°, the flow pattern is reasonable. Proper nozzle depth can be 200ram. Turbulent kinetic of meniscus can be reduced by adopting the square nozzle and suitable area of side outlet when casting speed increases. The results are consistent with those of water model experiment, so the model is exact and reasonable. The model can provide important information for design of SEN and defining of immersion depth.
关键词:
SEN parameter
,
null
,
null
D.F. Wu
,
S.S. Cheng
金属学报(英文版)
Turbulent flow and heat transfer coupled with solidification in slab continuous casting mold was studied by numerical simulation method. Volume of fluid (VOF) model is used to solve steel-air two-phase flow problem and enthalpy-porosity scheme is introduced to solve the fluid flow problem involving solidification. Contributions of various nozzle port angles and port widths and heights on the free surface fluctuation and the thickness of solidifying shell in slab mold were particularly investigated, based on which the structure of submerged entry nozzle was optimized. Flow inside the common nozzle port cannot fill the entire outlet area, having a recirculation in the upper portion of the port, which is enlarged for the nozzle port with both larger height and width. Results show that the flow in mold cavity is mainly controlled by the nozzle port angle. The increase of the angle of upper face of the port to shape a roughly streamlined inner-wall improves the effective area fraction of the nozzle, resulting in less jet impingement, weaker free surface turbulence and thicker solidifying steel shell.
关键词:
continuous casting
,
null
,
null
,
null
