辊环离心铸造钢液流动和传热的数值模拟

建立了轧辊辊环卧式离心铸造钢液流动和传热的二维耦合模型,采用大型CFD软件FLUENT求解得到重力和离心力场下的流场、温度场分布和钢液偏心情况,并讨论了钢水流动对凝固过程的影响,分析结果对离心铸造的工艺设计有参考价值.     

基于凝固传热模型的轴承钢GCr15二冷研究与应用

采用Gleeble 3500热应力/应变模拟机对轴承钢GCr15进行了高温力学性能测定,根据实际测量的结果,优化原有二冷制度并提出了适合轴承钢二冷冶金准则的二冷水表。并根据实际情况建立了大方坯连铸凝固传热模型,通过射钉试验表明模型准确可靠,在此基础之上提出了基于凝固传热模型的动态二冷控制方法,通过生产实践表明采用特征拉速控制二冷配水可以有效改善铸坯质量。     

Heat Flux Density and Heat Transfer Coefficient between Steel Melt and Metallic Substrates

The solidification of low carbon (LC) steels on metallic substrates was investigated with a twin roll caster and a model mould. The substrate materials were steel, Ni, and two copper alloys, which are typical for the industrial construction of moulds. Heat flux density, heat transfer coefficient, growth rate, and cooling rate were evaluated.     

Effects of Undercooling and Cooling Rate on Peritectic Phase Crystallization Within Ni-Zr Alloy Melt

The liquid Ni-16.75 at. pct Zr peritectic alloy was substantially undercooled and containerlessly solidified by an electromagnetic levitator and a drop tube. The dependence of the peritectic solidification mode on undercooling was established based on the results of the solidified microstructures, crystal growth velocity, as well as X-ray diffraction patterns. Below a critical undercooling of 124 K, the primary Ni₇Zr₂ phase preferentially nucleates and grows from the undercooled liquid, which is followed by a peritectic reaction of Ni₇Zr₂+L → Ni₅Zr. The corresponding microstructure is composed of the Ni₇Zr₂ dendrites, peritectic Ni₅Zr phase, and inter-dendritic eutectic. Nevertheless, once the liquid undercooling exceeds the critical undercooling, the peritectic Ni₅Zr phase directly precipitates from this undercooled liquid. However, a negligible amount of residual Ni₇Zr₂ phase still appears in the microstructure, indicating that nucleation and growth of the Ni₇Zr₂ phase are not completely suppressed. The micromechanical property of the peritectic Ni₅Zr phase in terms of the Vickers microhardness is enhanced, which is ascribed to the transition of the peritectic solidification mode. To suppress the formation of the primary phase completely, this alloy was also containerlessly solidified in free fall experiments. Typical peritectic solidified microstructure forms in large droplets, while only the peritectic Ni₅Zr phase appears in smaller droplets, which gives an indication that the peritectic Ni₅Zr phase directly precipitates from the undercooled liquid by completely suppressing the growth of the primary Ni₇Zr₂ phase and the peritectic reaction due to the combined effects of the large undercooling and high cooling rate.     

Convective Heat Transfer by Turbulent Melt Flow Excited by Travelling Magnetic Field at the Inductive Heating

We examine a convective dissipation-free heat transfer in melts under the action of a stationary component of electromagnetic body force induced by frequency-modulated travelling magnetic field.The influence of MHD parameters of turbulent flow on the transfer process is studied.     

高炉冷却壁非稳态传热研究

研究了铸钢、球墨铸铁和纯铜3种不同材质高炉冷却壁的非稳态传热过程。考察当高炉煤气温度分别为指数型和周期型变化时,冷却壁壁体温度场的变化情况。并根据不同材质冷却壁在非稳态工作过程中的表现,讨论这3种冷却壁的性能优劣。结果证明,铜质冷却壁是理想的长寿冷却壁,其性能明显优于铸钢和球墨铸铁冷却壁,并且这种优势在非稳态传热过程中表现的更为突出。同时铸钢冷却壁优于球墨铸铁冷却壁。     

铜冷却壁冷却恢复技术的传热过程

 铜冷却壁在正常状态时由于良好的导热性,在其热面形成稳定的渣铁壳,起到保护冷却壁的作用。近几年,高炉的铜冷却壁水管损坏时有发生,而当冷却壁水管损坏1或2根时,冷却壁能否继续正常工作值得研究。计算了铜冷却壁在水管完好和部分水管损坏时的温度场分布,发现单根水管损坏使热面温度急剧升高近110℃,加剧冷却壁烧损,需及时恢复冷却壁的冷却能力。通过用金属软管修复破损水管,分析了软管直径、水速、水管填料的导热系数等因素对冷却壁温度场的影响。结果表明,软管在允许条件下应选用较大内径,选取较大导热系数的填料。利用软管修复单个水管后,壁体最高温度下降约90℃,对于损坏少数水管的冷却壁能有效修复。     

非均匀冷却型结晶器铜板的传热特性

针对唐钢新型的FTSC非均匀冷却型结晶器,根据连铸结晶器的铜板实测温度、结晶器水量和进出水温差,建立了结晶器热流一维修正计算模型及其分布曲面,分析在生产SS400钢种时不同条件下的结晶器铜板热流分布特点,结果表明,相同条件下热流分布趋势和热面温度分布趋势相似,横向上波动剧烈,在距离铜板中心线400mm处的热流最高,距离弯月面越近波动越剧烈,在结晶器下部,中心部位的热流较低,并且平直段热流比漏斗区域的热流低;沿着结晶器高度方向,热流和热面温度变化梯度较小,在结晶器中部会有一个热流以及热面温度回升趋势;在整个铜板宽面上,热流较高,热面温度较低,这对提高结晶器使用寿命具有积极意义。     

钢板水冷过程换热系数建模的一种实用方法

为求解换热系数模型,以大量现场数据与热传递机制为基础,建立换热系数回归模型并使用ANSYS有限元软件对钢板冷却过程进行模拟,获取淬火过程中间数据。通过非线性回归算法对模型参数进行回归计算,最终取得整个淬火过程的换热系数公式。解决了现场无法测量淬火过程温度值,难以求解换热系数的难题。     

井式炉炉壁非稳态传热计算

根据有限差分法建立起来的傅立叶导热微分方程 ,推导出井式电阻炉炉壁、界面及内外表面非稳态的温度场计算公式。通过编程计算 ,对三种典型的炉型进行了具体的传热计算 ,非稳态计算结果与稳态计算结果相比热损失减少 40 %～ 5 7%。经测定 ,与实际符合较好     

基于热态实验的冷却壁传热分析

建立了高炉铸钢冷却壁传热数学模型,并通过热态实验验证数学模型,进而根据所建模型对冷却壁的稳态工况进行仿真计算.同时根据计算结果讨论了冷却水管水垢厚度、气隙层厚度对高炉铸钢冷却壁温度场的影响.结果表明:这两个因素对冷却壁的性能都具有很大的影响,在高炉操作和冷却壁的设计制造中必须重视.     

Transient Heat Transfer Analysis of Blast Furnace Cooling Staves

The capability of cooling staves is crucial for a long campaign life of blast furnaces (BF). Transient heat transfer analysis of blast furnace cooling staves made of copper, cast steel, and ductile cast iron are performed. Moreover, the temperature field variations of cooling staves according to different distributions of gas flow temperature are studied. A discussion of cooling staves made of the three different materials is given based on their performance during the transient heat transfer process. The results indicate that copper staves are suited for a long campaign life, as their performance is much better compared to cast steel and ductile cast iron staves especially during unsteady heat transfer. Moreover, the capacity of staves made of cast steel is better than that of ductile cast iron.     

高炉冷却壁与炉气之间的换热特性

 基于边界条件替换方法建立了高炉冷却壁本体和捣打料与炉气之间的换热系数计算模型。用试验测量冷却壁近热面温度来推算冷却壁热面温度，与冷却壁温度场计算模型结合，确定了炉气温度在500~1 248 ℃范围内，高炉冷却壁与炉气之间的换热系数。结果表明，本模型的计算值与前苏联学者的试验结果吻合。     

直流电弧炉钢棒式底电极传热与流动数学模型

 为了深入了解直流电弧炉水冷钢棒式底电极的传热过程，根据底电极的炉底结构结合相应的边界条件，建立了基于流动的二维轴对称固液相变传热数学模型。推导了考虑水冷铜套和电极之间空气隙影响的等效对流换热系数以及通电时的径向和轴向电磁力方程。模型中考虑了底电极从固态300 K到液态2 000 K过程中钢的物性的连续变化。利用所建模型，可以数值模拟直流电弧炉单炉冶炼、双炉冶炼的非稳态传热过程以及考察计算参数和结构改变影响的稳态传热过程，为改善电弧炉的安全性、提高工作效率提供理论依据。     

包钢高炉风口小套冷却水流速的换热模拟

高炉风口是向炼铁高炉输送热风和煤粉必需的通道,是保证高炉炼铁正常生产的关键工艺部件,风口小套作为高炉风口的重要组成部分,其冷却效果直接关系到寿命的长短,文章以5#高炉在线贯流式风口小套为基体,用solidwoks工具创建三维模型,用ANSYS进行建模划分网格,用Fluent流体分析工具对风口小套进行冷却水换热模拟,求解合理水流流速,以达到其最合理的使用寿命。     

Construction and Application of Quenching Critical Cooling Rate Model

 Based on exploring quenching mechanism, three types of medium-low carbon steel and low-alloy construction steel’s quenching critical cooling rate models were established, respectively speaking, modified Maynier model, Eldis model and isothermal curve model. During construction process, regression analysis and Newton interpolation method were used for higher calculated precision. Through comparing and analyzing, the superior one was singled out to evaluate the full hardening thickness after quenching. According to hardness analyzing, the deviation between predicted hardness distribution and the experimental value is within 6%.     

同质冷却水口的试验研究和传热分析

 为实现低过热度浇注,开发了一种冷却水口。在不同长度和出口直径的条件下分别进行了多组浇钢试验和数值模拟计算。比较了2种长度、3种不同出口直径水口的浇注结果和计算结果。得到实现低过热度浇注的最佳工艺条件为水口长190 mm,出口直径为20 mm,在浇注平衡时热流为1224 MW/m2。     

钢管冷却喷淋水量对换热系数的影响

 采用一种钢管外喷淋装置,通过在钢管中预埋热电偶测量钢管冷却期间的温降曲线,研究了喷淋水量对钢管冷却强度的影响。利用有限元模拟软件对测量结果进行分析,建立了钢管表面对流换热系数和水流密度的数学关系模型,将模型嵌入了钢管温度场计算软件当中,软件的计算精度进行了工程验证。结果表明,融合了该换热数学模型的钢管温度场模拟软件计算精度达到90％以上。     

基于ANSYS的高炉铸钢冷却壁传热分析

运用大型有限元通用软件ANSYS,对高炉铸钢冷却壁稳态工况进行传热学分析。同时根据计算结果,分析了冷却壁在稳定工作状态下的温度、热流以及温度梯度的分布情况。通过分析可以找出冷却壁工作中需要注意的地方,为今后冷却壁的维护和设计提供参考。还讨论了冷却水管水垢对高炉铸钢冷却壁温度场的影响。结果表明,水垢每增加1mm厚,会使冷却壁热面温度升高约60℃。     

带钢超快速冷却条件下的换热过程

 分析了轧后加速冷却过程中带钢表面的局部换热机理，认为冷却系统实现超快速冷却的关键在于扩大带钢表面射流冲击换热区的面积。确定了薄带钢实现超快速冷却所需的对流换热系数，并采用有限元分析工具ANSYS模拟得到了超快速冷却条件下不同厚度带钢的温度场。温度场的分布表明薄带钢在超快速冷却过程中具有较好的温度一致性。同时还表明随着带钢厚度增加，超快速冷却条件下厚度方向的温度梯度显著增大，对于带钢内部组织的均匀性将产生不利的影响。带钢厚度范围应是超快速冷却技术实际应用过程中的重要考虑因素。