双辊铸轧不锈钢薄带的三维有限元数值模拟

采用三维有限元法模拟了双辊铸轧不锈钢过程的流热耦合问题,分析了铸轧速度以及浇铸温度对熔池内流场、温度场的影响,给出了凝固过程中熔池与铸轧辊之间的热流密度变化趋势及凝固终子位置随浇铸温度的变化规律,模拟结果与实验数据比较吻合。     

工艺参数对双辊薄带铸轧中心层偏析影响

双辊薄带铸轧过程中工艺参数对中心层偏析有重大影响,针对双辊薄带铸轧机的特点,利用多相流技术建立完全耦合溶质场、流场、温度场的数学模型,对铸轧熔池中液相-液固两相-固相同时存在的复杂凝固过程进行模拟仿真,研究分析铸轧熔池中Mg、Si元素溶质场与流场分布特征,对比研究不同工艺参数(浇铸温度、辊缝宽度)对铸轧薄带中心层偏析的影响规律,并结合铝合金6061的铸轧实验对结论进行验证。     

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。     

考虑材料非线性双辊铸轧辊套流热固耦合温度场研究

基于Procast连铸模块材料数据库,提取低碳钢物性参数随铸轧温度不断变化的散点数据进行非线性曲线拟合,并在此基础上考虑铸轧辊旋转、冷却系统、浸入式铸嘴、侧封板传热等影响,建立了辊套、熔池与冷却系统整体三维流热固耦合有限元模型并进行瞬态仿真,得出了双辊铸轧辊套整体温度分布情况及内、外表面的温度变化规律。结果表明,根据前处理方式得到的温度场更加贴合双辊铸轧实际生产情况,为辊套的设计和优化铸轧工艺参数具有一定的参考价值。     

不同铸轧工艺参数对铸轧辊套温度场影响规律的研究

依据建立的包括铸轧辊套在内的铝双辊铸轧的整体耦合数学模型对铸轧辊套温度场进行了模拟计算,研究了不同的铸轧速度、带坯厚度、内冷强度、铸轧区长度对铸轧辊套温度场的影响规律.结果表明:铸轧辊辊套外表面任意一点的温度随着铸轧辊的转动发生周期性变化;铸轧速度增加,铸轧辊套外表面温度提高;内冷强度增加,铸轧辊套温度场将降低;铸轧区长度增加,铸轧辊套温度场峰值降低.     

镁合金双辊铸轧铸嘴内部熔体流动数值模拟

分析了铸嘴内部分流结构对型腔内镁合金熔体流场、温度场产生的影响.采用有限差分的SOLA-VOF法,建立镁合金双辊铸轧立板过程中流动区域的三维流场与温度场耦合模型,在相同的铸轧立板条件下(前箱液面高度、前箱熔体温度固定),数值模拟了不同形状的铸嘴型腔结构对熔体流动速度及温度分布的影响.模拟结果表明,分流块的大小、形状及位置对温度场及流动场影响显著,采用小尺寸、多数量的分流块将有利于在铸嘴型腔内形成均匀的流动场和温度场.通过工艺试验,验证了模拟结果,根据模拟结果改进了铸嘴内部结构,使金属熔体流场、温度场分布均匀,获得了高质量的镁合金铸轧板材.     

上方侧注式双辊铸轧辊套温度场的数值模拟

通过数值模拟,对上方侧注式双辊铸轧机的轧辊辊套温度场进行了研究。研究表明,通过将模拟结果与实测数据的比较,验证了模型的可靠性;在铸轧过程中,轧辊外表面温度随着轧辊的旋转发生周期性的变化;当上、下辊套厚度均为40mm时,上、下辊套的温度分布差异较大,下辊套温度明显比上辊套温度高;加强冷却对辊套温度场的影响较小;减小辊套厚度,辊套的温度降低,但辊套内、外表面温差增大;增加熔池与上辊套的接触弧长度,上辊套温度增大。     

双辊铸轧AZ31镁合金成形过程组织演变的研究

为了研究镁合金双辊铸轧过程微观组织的演变,对轧制试样进行了微观组织分析。利用有限元软件进行了熔池温度场、流场三维耦合数值模拟。探讨了镁合金铸轧过程熔池的特点及薄带的形成机理,并分析了双棍铸轧过程的动态组织演变。     

双辊薄带铸轧过程钢液过热度控制研究

钢液过捕度是薄带铸轧工艺过程中的一个重要参数,它不仅影响钢液的流动性能,还影响凝壳厚度和Kiss点高度,使铸轧力发生变化,从而影响铸带的整体性能.利用有限元和实验相结合的方法确定了在浇注不锈钢时,过热度对熔池内钢液的温度场、速度场分布的影响,确定出了在指定工况下的最佳过热度范围.     

SCR技术半固态制浆热流偶合场的三维有限元模拟

在ANSYS有限元软件求解平台上对SCR技术半固态制浆过程热流耦合场进行三维模拟,给出了不同工艺参数下的温度场和速度场的分布情况,并将模拟结果与实验结果进行比较.结果表明,在旋转工作辊拽动下,辊靴型腔内合金做层流运动,各流层的速度从工作辊表面到靴表面呈线性递减.合金温度从辊靴入口到出口逐渐下降,在速度场影响下,合金温度场等温线向工作辊面发生偏移,近工作辊面温度偏高.随着合金液浇注温度的升高、辊靴型腔高度的增加或者工作辊转速的提高,出口半固态浆料的温度升高,与实验结果一致.     

3D Numerical Simulation on Thermal Flow Coupling Field of Stainless Steel During Twin-Roll Casting

The surface crack and lateral crack of the AISI 304 stainless steel thin strip produced by twin-roll casting were observed. The temperature at the center of outlet during twin-roll-casting process was determined by infrared thermometer. In order to avoid the surface cracks of the casting strip, the thermal flow coupling field of AISI 304 stainless steel during twin-roll-casting process was simulated by a 3D fluid-structure coupling model. According to the simulation result, the effect of the casting speed on thermal flow field was analyzed and the process parameters were optimized. Moreover, by studying heat flux curves, the heat transfer mechanism between molten pool and roll was analyzed. The results show that, with the increase of the casting speed, the temperature of the molten pool increases and the solidification point moves toward the outlet. Meanwhile, the whirlpool above gets larger. Based on the solidification front position, the optimized process parameters are 1500 °C and 0.37 m/s. The heat transfer mechanism between molten pool and roll contains direct contacting heat transfer and air gap heat transfer.     

Numerical Simulation Of Molten Pool And Control Strategy Of Kiss Point In A Twin-Roll Strip Casting Process

Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.     

Investigation of the solute transportation coupled with heat transfer and fluid flow during twin-roll strip casting process

Mathematical model of solute [C] distribution in twin-roll strip casting process has been setup successfully with Calcosoft for the first time. Simulation result shows that in the center of the molten steel pool between the two rolls there is a vortex flow, which is a solute enriched area. But the highest solute concentration position is at the solidification front of the columnar grain zone near the cooling roll surface. Another solute enriched position is in the back flow above the nip point. Combined wit...     

Effect of casting parameters and deformation on microstructure evolution of twin-roll casting magnesium alloy AZ31

Twin roll casting method is a promising route to directly produce magnesium alloy strip. It is a rapid solidification process with high temperature gradient combined with thermal flow and roiling deformation in the casting region. As-cast strip with proper mierostructure is requested to serve as next rolling feedstock. However the microstructure of as-cast strip is sensitive for casting conditions during the casting process and the as-cast microstructure greatly affects the mechanical properties. In this work, the effect of casting speed, pouring temperature, deformation as well as anneal process on microstructure and mechanical properties were investigated. The results revels that twin-roll casting process can effectively refine the grain size, improve the morphology and distribution states of Mg1TAl12. The homogenization treatment time can be shorted for the fine microstructure and lower the cost dramatically for the next forming process.     

Micromodel of Simulation on Twin-Roll Continuous Casting Thin Strip Solidification Structure

在研究双辊连铸铝合金薄带工艺凝固过程的基础上,基于金属凝固的基本原理,建立双辊连铸铝合金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,同时建立基于元胞自动机(CA)的双辊连铸铝合金薄带凝固组织的仿真模型,为双辊连铸薄带凝固组织形成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。     

Producing thin strips by twin-roll casting—part I: Process aspects and quality issues

This two-part paper discusses recent advances in research and development for the direct production of coilable thin strips by twin-roll casting in both the aluminum and steel industries. While the former is empowering the casters to approach the theoretical productivity limit, the latter is striving to put pilot casters into commercial operation. These intensive R&D efforts are derived from the advantages, both economic and metallurgical, offered by the process. As twin-roll casting combines solidification and hot rolling into a single operation, the process requires low capital investment and low operational cost. Also, because of the high solidification rate attained in the process, the thin strips produced have a refined metallurgical structure, characterized by columnar and equiaxed zones with fine intermetallic particles. The enthusiasm about twin-roll casting is now being spread worldwide. This paper focuses on the process aspects and quality control of twin-roll casting. Part II, which will appear in the August issue, will review process modeling and pilot-plant development activities.     

Continuous fabrication of bulk amorphous alloy sheets by twin-roll strip casting

Twin-roll strip casting was utilized to fabricate the sheet products of Zr- and Cu-base bulk amorphous alloys with quite different glass forming abilities (GFAs). Simulation of the solidification behavior of the these amorphous forming alloys during twin-roll strip casting shows that suitable cooling rate can be achieved by twin-roll strip casting to form amorphous structure through the thickness of sheet. Optimum twin-roll strip casting conditions have been suggested based on the simulation results. Actual twin-roll strip casting shows that both Zr-base alloy with high GFA and Cu-base alloy with much less GFA can be strip cast forming amorphous structure. The results indicate that the twin-roll strip casting is a viable process for continuous fabrication of sheets of bulk amorphous alloys with a wide range of critical cooling rates.     

Twin-roll strip casting of magnesium alloys in China

The development status of twin-roll strip casting for magnesium alloys in China was summarized as well as the new progress when several kinds of twin-roll strip casting technologies were developed and used.Horizontal twin-roll casting (HTRC) of magnesium alloys has attracted much attention and has been industrialized in China.Vertical twin roll casting(VTRC) of the magnesium alloys can reach a speed of higher than 30 m/min and its research and development are just beginning and exhibit exciting potential...     

Development and application of coupling model of aluminum thin-gauge high-speed casting

Based on the analyses of aluminum melt flow, solidification, heat transfer during the process of twin-roll casting, a coupling mathematical model of aluminum thin-gauge high-speed casting was developed, which included the casting roller shell. At the same time, Galerkin method was adopted to solve the coupling model. The fluid field and temperature field of aluminum melt in casting zone, the temperature field and thermal stress field of roller shells were simulated by the coupling model. When the casting velocity is 7 m/min, and the thickness of strip is 2 mm, the circumfluent area comes into being in the casting zone, and the mushy zone dominates the casting zone, while the temperature of melt decreases rapidly as it approaches the rollers. The temperature of the roller shell varies periodically with the rotation of roller, and reaches the highest temperature in the casting zone, while the temperature of roller shell decreases gradually as it leaves the casting zone. The difference of thermal stress between the inner surface and outer surface of the roller shell is very large, and the outer surface suffers tensile-compressive stress.     

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。