Simulation of microstructures in solidification of aluminum twin-roll casting based on CA

The microstructures in the solidification process of aluminum twin-roll casting was simulated based on CA (Cellular Automation Method), and the nucleation model based on the normal distribution and KUZR-GIOVANOLS-TRIVEDI(KGT) growth model were used in the calculation. FDM (Finite Difference Method) combined with relative motion was used, and dynamic evolution of microstructures in the process of aluminum twin-roll casting was achieved. Visual Fortran programming language was adopted to calculate and realize the image post-processing. Moreover, the effect of different casting process parameters on the formation of the microstructures was simulated. The results are helpful to explaining the dendritic segregation and size segregation as well as shrinkage-porosity defects. Columnar grains mainly distribute near the casting roller while equiaxed grains distributed far away from the casting roller.     

铝带坯双辊铸轧过程瞬态传热数学模型

采用拉格朗日随体坐标建立了铝双辊铸轧过程瞬态传热数学模型。在数学模型中考虑了金属凝固动力学条件和采用试验测定的辊/铝带坯界面接触换热系数边界条件,用有限差分方法对控制方程进行了数值求解,并由现场测试数据验证了传热数学模型的正确性。     

双辊薄带铸轧低碳钢薄板的组织及力学性能

对双辊薄带连铸(TRC)工艺条件下低碳钢铸带坯、热轧板的显微组织及力学性能进行研究,并与传统生产工艺(TP)的冷轧板产品进行了对比。铸带坯主要由200~300μm的不规则的多边形铁素体组成,并伴随着少量20μm左右的多边形铁素体。经一道次热轧后,厚度方向上组织严重不均:上下表层为细晶区,平均晶粒尺寸为10μm左右;中部为粗晶区,平均晶粒尺寸为40μm左右。粗晶区宽度约占整个板厚的50%。传统生产工艺的冷轧退火板的组织则较为均匀,平均晶粒尺寸约为15μm。薄带连铸热轧板与传统冷轧退火板相比具有较强的α织构和较弱的γ织构。薄带连铸热轧板的屈服强度、抗拉强度与传统工艺的冷轧退火板相当。但是,两者的拉伸曲线显著不同,前者表现为连续屈服,后者出现了屈服平台。     

铝双辊连续铸轧凝固微观组织的数值模拟(英文)

在研究双辊连铸纯铝薄带凝固过程的基础上,基于金属凝固的基本原理,并运用现代计算机仿真技术建立双辊连续铸轧纯铝薄带凝固的异质形核,枝晶尖端的生长动力学(KGT),柱状晶向等轴晶生长的转变(CET)的解析模型;建立基于元胞自动机(CA)的双辊连铸纯铝薄带凝固组织的仿真模型,为双辊连铸薄带凝固组织的仿真模拟奠定基础,从而为双辊薄带连铸工艺提供一定的理论指导。同时,利用双辊薄带连续铸轧纯铝凝固微观组织过程验证数学模拟的可行性。     

双辊薄带不锈钢铸轧过程数值模拟

采用有限元法模拟了双辊铸轧不锈钢过程的流热耦合问题;分析了铸轧速度对熔池内流场、温度场的影响以及流场与温度场之间的相互影响;通过熔池内温度场及温度梯度分析了熔池内凝固的发展及其对热流密度变化的影响。此模拟结果可以为控制铸轧过程的稳定提供有效的数据。     

双辊铸轧薄带钢温度场的有限元数值模拟

建立了双辊铸轧薄带钢过程有限元数学模型 ,开发了二维温度场的模拟软件TRC HEAT。利用该软件对熔池内的温度场进行了模拟 ,得到了不同工艺条件下温度场曲线 ;得到了实现稳定轧制时各工艺参数之间的关系 ,为铸轧过程的分析和控制提供了理论依据     

双辊激冷铸造A8006合金的均匀化(英文)

通过SEM、XRD与硬度测定研究均匀化过程对双辊激冷铸造(TRC)与直接冷却铸造(DC)A8006合金的微观组织和性能的影响。结果表明,随着TRC合金微观组织的细化,均匀化后合金中的共晶相进一步细化。DC合金均匀化后其共晶相形态相似于TRC合金中的共晶相形态。均匀化后,合金共晶相中的Fe、Mn元素均匀地扩散到铝基体中,引起合金硬度的降低。TRC合金的成形性能优于均匀化的DC合金,所以,对于TRCA8006合金的后续加工过程可省去均匀化过程。     

Microstructures of electromagnetic casting and direct chill casting LY12 aluminum alloys

1　INTRODUCTIONElectromagneticcasting (EMC)isatechnologydevelopedbythecombinationofmagnetohy drodynamics (MHD )andcastingengineering[13] .TheEMCtechnologydependsontheelectromagneticforcetopreventthemetalfromtouchingthemold .Dependingontheinteractionofeddycurrentsinducedinthemetalandthemagneticfieldoftheinductor ,theliquidmetalcolumniskeptstable[4 6 ] .Thecon tactlesscastingofEMCmayeliminatetheliquidationbuild upsandfeathercrystals ,relievethescalpingop erationbeforethehotrollprocess …     

Thin strip quality obtained in twin-roll casting

Ferrous alloy strips of width 150 mm and thickness 150–300 μm were obtained by rapidly cooling from the molten state at ～ 105 Ks^?1 with the pressing force of the rolls during casting 1.5 kN mm^?1 and a rotational speed of 8 ms^?1. Typical composition of the strip was Fe—4.5%Si, Fe—23%Cr—5%Al or Fe—12%Al. The roller wear mechanism and strip quality were investigated using two sets of cylindrical, water-cooled, bronze roll moulds. It was found that the width of the strip obtained by rapid quenching in rolls is determined by the consumption of metal and depends on fluctuations in the molten bath. Strip thickness increases with bath depth. The lenticular form of the strip is obtained by bending of the rolls, and the biconcave form, using a thick water-cooled roll sleeve, is a result of the thermal expansion of the roll.

Roller wear and changes to the strip microrelief were investigated using different alloys. The roughness of the surfaces of both strip and roller increased throughout the casting process. The amount of increase depended more on the alloy than on the melt temperature. The average values of the angles of the slopes of micro-peaks were measured and compared and decreased along the strip. Comparison of the coefficient of anisotropy across the width of the strip showed a decrease from the edge to the middle of the strip. The apparent reason for the appearance, on local areas of the strip surface, of oxide pellicles is revealed.     

双辊铸轧薄带钢侧封板热应力的数值分析

采用有限元法模拟了双辊铸轧薄带钢工艺中侧封板的三维温度场和热应力场。通过对侧封板的温度和应力的耦合数值模拟 ,得出了在铸轧过程中侧封板的温度和热应力的分布规律。根据热应力分析了侧封板裂纹产生机理 ,得出侧封板产生裂纹的位置与实验结果相吻合 ;同时分析了不同预热温度对侧封板温度和热应力分布的影响 ,得出了侧封板的最佳预热温度范围     

双辊铸轧薄带工艺中的相关技术

介绍了双辊铸轧技术的发展 ,及其在日本崎玉工业大学实验轧机上铸轧铝合金带的实验结果 ,并对目前该工艺的 1 0项关键技术进行了分析和论述     

双辊铸轧法制备Al-Fe-Si合金铝箔过程中第二相对表面亮条影响的3D模拟(英文)

利用扫描电子显微镜、能谱分析以及3D有限元模拟等手段研究族聚第二相与表面亮条形成之间的关系。研究表明:铸轧铝箔毛料中的AlFeSi粒子呈族状分布在毛料表面或近表面。硬质团族粒子与冷轧时的纳米油膜相互作用,会使粒子附近的润滑油膜破裂,导致粒子与破裂区域的铝膜基体发生严重变形,与周边产生色差,形成表面亮条。     

AZ31镁合金异步铸轧板的显微组织

研究AZ31镁合金异步铸轧板坯沿厚度方向的显微组织分布。结果表明,板坯组织沿厚度方向具有较明显的不均匀性。在板坯的上表面附近存在较多的流线型变形带组织;在中心处观察不到变形带组织,枝晶臂较粗大;在板坯下表面附近枝晶组织较细密。板坯上表面附近的流线型变形带是由上、下铸轧辊表面线速度差产生的剪切应变而引起的。Al、Zn和Mn在枝晶晶界处发生偏聚,Si均匀分布在α-Mg固溶体内。     

Microstructure and interface reaction of investment casting TiAl alloys

In order to research the microstructure of TiAI alloy and TiAl-mould reaction between TiAI and ceramic mould shells prepared with the low cost binder in investment casting, the ceramic mould shells were prepared with low cost binder and refractory materials. Using two kinds of casting methods （gravity casting and centrifugal casting）, the titanium aluminum alloys with rare earth element （Ti-47.5Al-2Cr-2Nb-0.3Y and Ti-45Al-5Nb-0.3Y） were cast into the mould shells. The microstructures of investment casting titanium aluminum alloys were observed by optical microscope （OM）. The distributions of elements of topping investment on the surfaces of titanium aluminum alloys castings were analyzed by the means of electron probe micro-analysis （EPMA）, and the mechanical properties were studied. The results show that the microstructures of two kinds of titanium aluminum alloys are both lamella shape, and lamella is thin. The thickness of reaction and diffusing layer of Ti-47.5Al-2Cr-2Nb-0.3Y alloy is about 80 μm, and that of Ti-45Al-5Nb-0.3Y is less than 30 μm.     

Effect of Oscillating Field on Microstructure of Twin-roll Cast 7075 Aluminum Alloy

研究了在670℃下,振荡磁场双棍铸轧对7075铝合金成型板材微观形貌和硬度影响。结果表明,同传统方式铸轧相比,采用振荡电磁场铸轧板材的枝晶被严重碎断、细化和等轴化。在此条件下7075板材的表面及中心的偏析程度大幅减轻,并且在交变振荡场的作用下偏析完全消失。普通铸轧条件下板坯横向和轧向的HV硬度值分别为1104和1356 MPa;采用电磁场后,在交变振荡场下获得最大硬度为1615 MPa;除此之外,当磁场强度增加,板材性能会进一步提高。另外发现,无论在何种磁场条件下,升高浇注温度后,外加电磁场的细化作用效果增强。     

双辊薄带连铸凝固组织模拟微观模型的验证

以双辊薄带连续铸轧工艺凝固过程为基础,基于金属凝固的基本原理,并运用现代计算机仿真技术建立了双辊薄带连铸凝固过程的异质形核、修正的枝晶尖端生长动力学、柱状晶向等轴晶生长转变(CET)的解析模型以及基于元胞自动机(CA)的双辊薄带连续铸轧凝固组织的仿真模型,为双辊薄带连续铸轧凝固组织形成的仿真模拟奠定了基础,同时利用铝合金双辊薄带连续铸轧组织凝固过程验证了数学模拟的可行性。结果表明:可用建立的数学模型模拟预测铸轧工艺参数对双辊连续铸轧薄带凝固组织的影响。     

Microstructure and properties of vacuum counter-pressure cast aluminum alloy

As a special casting process, counter-gravity casting has many advantages especially in producing thin-wall complicated castings and has widely been used in industry [1]. In recent ten years, various different counter-gravity casting processes have been continuously developed such as vacuum suction casting, low-pressure casting and counter-pressure casting [2-4] et al. Vacuum counter- pressure casting is a new kind of counter-gravity casting technology that was developed in recent years. It ha…     

Cu/Al复合板双辊铸轧复合界面压力分布与结合特性（英文）

双辊铸轧工艺制备双金属层复合板的力学性能和产品厚度规格与结合界面相互作用力学行为密切相关。以铸轧速度为变量,建立热流耦合模拟与界面压力分布计算模型。结果表明,随着铸轧速度的降低,界面温度降低,界面压力与出口铝侧厚度占比增大。铜带减薄主要发生在后滑移区。较高的界面压力和较长的固体/半固体接触时间使结合面充分浸润,为原子扩散提供有利条件。当铸轧速度为2.4 m/min时,扩散层宽度为4.9μm,剥离后铜侧表面被铝覆盖,铝侧发生韧性断裂,有效防止界面分层及裂纹扩展。同时,高界面压力及塑性应变下的剪切作用更显著,铝侧显微组织为细长柱状晶体。因此,结合界面实现冶金结合并细化铝侧晶粒可以使复合板获得较高的结合强度和拉伸性能。     

双辊薄带连铸对无取向硅钢织构和磁性能的影响

研究了1.3%Si无取向硅钢双辊连铸薄带和热轧板坯在冷轧退火过程中组织、织构和磁性能演化的特点。结果表明:铸带组织和热轧板坯初始组织的明显差异影响了冷轧退火再结晶组织和织构的演化。在相同冷轧和退火条件下,铸带试样再结晶晶粒比例较后者热轧板坯低试样,但是晶粒尺寸较大,而且Cube和Goss等有利织构组分比例高于热轧板坯试样,有害的γ组分较弱,这使得铸带试样具有较高的磁感和较低的铁损。