共查询到20条相似文献,搜索用时 187 毫秒
1.
Ti-1023合金VAR熔炼数值模拟研究 总被引:1,自引:0,他引:1
Ti-1023合金因其优异的性能广泛应用于大型承力结构件,然而因其添加Fe元素含量较高,容易在真空自耗熔炼(VAR)制备铸锭的过程中出现Fe偏析,影响锻件的性能。利用多场耦合重熔工艺仿真优化软件(Melt Flow-VAR)建立的模型研究了Ti-1023合金在VAR不同阶段下的熔池形状和元素浓度分布,并以模拟工艺制备了Ti-1023合金Φ640 mm大规格铸锭进行验证。结果表明:随着熔炼的进行,模拟的熔池形状按初期的扁平状→中期的V形→末期的深V形变化,熔炼后期的熔池深度为0.28 m,与实测结果基本一致。在铸锭中心线顶部和底部Fe和Al元素成分的模拟结果与实测值吻合良好,但在铸锭中间部分的模拟值与实测值存在较大偏差,分析认为是Melt Flow-VAR计算模型中没有考虑等轴晶的沉降所导致的计算偏差所致。 相似文献
2.
3.
4.
5.
《真空科学与技术学报》2016,(7)
通过Pro-CAST有限元软件模拟了高性能轴承钢真空自耗熔炼过程的温度场、熔池形貌和微观组织,研究了真空自耗铸锭组织演变规律,探究了温度场、熔池形貌对组织生长的影响。熔炼结束后,对真空自耗铸锭进行解剖酸洗以验证模拟结果。研究表明:模拟结果与实验结果吻合,铸锭组织形貌为贯穿铸锭中心的细长柱状晶,真空自耗铸锭的底部、边部和凝固末端有小面积等轴晶。柱状晶的生长带有明显的择优取向,底部柱状晶取向为垂直向上,中上部为斜向上。熔池深度越大,斜向上角度越小;熔池形貌对铸锭组织形貌影响显著,通过控制熔炼参数控制好熔池形貌能有效提高铸锭质量。 相似文献
6.
7.
8.
9.
10.
11.
目的 探究激光功率(P)和扫描速度(v)对单熔道熔池几何特征尺寸的影响规律,以及P–v组合工艺参数对熔池从成形到稳定状态经历的扫描距离的影响规律。方法 以316L为材料,通过单熔道数值仿真分析,建立P–v变量与研究目标之间的影响关系。结果 不同P–v参数组合对熔池几何尺寸的影响规律明显,熔池几何参数达到稳定状态需要经历一定的激光扫描距离(小于1 mm)。随着激光功率增大,熔池长度达到稳定状态所经历的激光扫描距离随之增大,而熔池深度尺寸随之减小。扫描速度增大到400 mm/s时,熔池达到稳定经历的扫描长度缩短了6.7%,扫描速度对熔池稳定性的影响效果不显著。结论 在SLM单道成形过程中,激光功率、扫描速度越大,成形熔池平均长度尺寸也越大;激光功率越大、扫描速度越小,成形熔池深度及平均宽度越大。模拟试验获得重熔效果较好的P–v参数组合为P=200 W、v=800 mm/s,重熔率达到94%。在熔池成形过程中,激光功率对熔池稳定性的影响起主导作用。为了减少成形件的边界翘曲,在打印试件初始成形阶段应在合理激光功率范围内选择较高的激光功率。 相似文献
12.
目的 研究等离子弧焊接穿孔过程中熔池内部的金属流动情况和小孔动态变化过程。方法 通过“传热-熔池流动-小孔”之间的相互耦合关系,建立了等离子弧焊接穿孔过程的数值分析模型,通过VOF方法追踪了小孔界面,采用FLOW-3D软件模拟了等离子弧焊接熔池和小孔的形成过程,定量计算了等离子弧焊接温度场、熔池流场及小孔形状;分析了等离子弧焊接熔池和小孔行为;并通过等离子弧焊接实验数据验证了模拟结果。结果 当焊接时间为0~1.0 s时,小孔深度曲线与熔深曲线几乎相同,小孔底部紧贴熔池底部;在2.8 s以后,小孔深度曲线与熔深曲线有一定距离,小孔深度曲线在一定范围内波动,等离子弧焊接电弧挖掘作用到达极限,电弧压力与其他力达到平衡状态。模拟的焊缝熔深为8.04 mm、熔宽为13.20 mm,实验测得的焊缝熔深为8.00 mm、熔宽为13.42 mm。结论 构建的随小孔动态变化的曲面热源模型和电弧压力模型可以描述等离子弧焊接过程中的电弧热-力分布;模拟出了等离子弧焊接熔池和小孔动态演变过程;模拟得到的等离子弧焊接焊缝形貌与实验测得的焊缝形貌基本吻合。 相似文献
13.
R. C. Atwood P. D. Lee R. S. Minisandram R. M. Forbes Jones 《Journal of Materials Science》2004,39(24):7193-7197
The vacuum arc remelting of titanium 6-4 alloy is a complex process. Relatively high melt currents (≥30 kA) are used resulting in a very deep melt pool that is continually changing in size (first increasing and then decreasing). The process is further complicated due to the use of external stirring coils to control and steer the arc. A transient model is needed to adequately describe the process. A multiscale modelling approach was developed which combines an axisymmetric CFD model at the macroscale with a cellular automaton model at the mesoscale. The macro model is used to simulate the heat and mass transfer throughout the ingot and melt pool under the influence of the arc, including EMF. A decentred-square cellular automaton model is used to predict the nucleation and growth of grains. This multiscale model is applied to the initial phase of the process, and the predicted microstructures are compared with trial ingots. The effect of the model parameters such as stirring and grain nucleation on the morphology of the columnar zone is investigated. 相似文献
14.
Three-dimensional transient governing equations were developed based on conservation laws of energy, momentum and mass. These equations described physical phenomena of convection in weld pool and heat transfer in workpiece during variable polarity vertical-up plasma arc welding process. Boundary conditions for the developed governing equations were given. Welding energy input for variable polarity vertical-up plasma arc welding process was quantitatively expressed. Free surface deformation of the keyhole molten pool was coupled into calculation. Effect of wire filling on the geometry of molten pool and weld reinforcement was considered in the simulation. Correlations of temperature and thermophysical properties for aluminum alloy 2219 were quantitatively established. A control volume based finite difference method was used to solve the discrete governing equations. Moreover, dynamic evolutions of geometrical profile, dimension and fluid flow for the molten pool and keyhole were simulated through the developed computational routines, which achieved transient solution of fluid flow field coupling with thermophysical properties, temperature field and weld pool free surface deformation. Besides, the effect of the workpiece thickness on the moments of keyhole formation and stable keyhole establishment was analyzed, and thermal cycles for the main welding stage were calculated. In addition, experiments via variable polarity vertical-up plasma arc welding technique were conducted, and the established models were experimentally verified through weld cross-section profiles. 相似文献
15.
16.
The relationships among the parameters that govern the plasma arc MR (melting and refining) process and the quality of the alloy melts are complicated. Only a simulation of the process can enable the process to be properly controlled and the right compositions to be achieved. The main purpose of this paper is to simulate the temperature distribution in the molten pool using the software FEMLAB. Numerical calculations were based on finite element analysis and the coupling of heat transfer, fluid flow and electromagnetic modules. The results of simulations are verified with the meniscus shape of liquid isothermal line in the solid ingot. 相似文献
17.
This study concerns the laser transmission welding (LTW) of polyethylene terephthalate (PET) and polypropylene (PP) which are widely used in the automotive, aerospace and medical industries. The relationships of process parameters, molten pool geometry (both width and depth) and shear strength (SS) in LTW process are systematically investigated through finite element method (FEM), response surface methodology (RSM) and experiments. Thereinto, the relationships between the molten pool depths to width (D/W) ratio and SS are firstly investigated. Firstly, a three-dimensional thermal model is developed to simulate the temperature field and molten pool geometry of the LTW process. The simulation results are confirmed by experiments. Then RSM is utilized to design the experiments and establish the mathematical relationships between the process parameters and molten pool geometry based on the simulation results. The interaction effects of the process parameters on the molten pool geometry are analyzed. Finally, the simulation results are further used for searching the relationships between the molten pool D/W ratio and the SS (from tensile experiments). The maximum value of the SS and the corresponding molten pool D/W ratio is found. The result reveals that the molten pool D/W ratio has a significant influence on the SS. Moreover, this finite element model can also play a commendable guiding role in the LTW experiments with acceptable accuracy. 相似文献
18.
Modelling of arc welding: The importance of including the arc plasma in the computational domain 总被引:1,自引:0,他引:1
We present results of computational simulations of tungsten-inert-gas and metal-inert-gas welding. The arc plasma and the electrodes (including the molten weld pool when necessary) are included self-consistently in the computational domain. It is shown, using three examples, that it would be impossible to accurately estimate the boundary conditions on the weld-pool surface without including the arc plasma in the computational domain. First, we show that the shielding gas composition strongly affects the properties of the arc that influence the weld pool: heat flux density, current density, shear stress and arc pressure at the weld-pool surface. Demixing is found to be important in some cases. Second, the vaporization of the weld-pool metal and the diffusion of the metal vapour into the arc plasma are found to decrease the heat flux density and current density to the weld pool. Finally, we show that the shape of the wire electrode in metal-inert-gas welding has a strong influence on flow velocities in the arc and the pressure and shear stress at the weld-pool surface. In each case, we present evidence that the geometry and depth of the weld pool depend strongly on the properties of the arc. 相似文献
19.
目的 研究激光熔丝增材制造过程的熔池流动特性,探究工艺参数对熔池流动与传热行为的影响.方法 建立了考虑运动丝材持续送进过程的激光熔丝增材熔池传热和流动行为数学模型.针对316L不锈钢的激光熔丝增材制造,开展了成形过程中丝材送进、熔化和凝固行为的实验和数值模拟研究.结果 模拟结果 显示在成形过程中,准稳态阶段激光辐照中心的最高温度约为2500 K.金属液主要由丝材端部向熔池尾部流去,并在熔池尾部凝固形成堆积体.同时,熔池表面最大速度可达0.8 m/s,并具有速度振荡特征.结论 基于激光熔丝增材制造过程数学模型的模拟结果 与实验吻合良好,结果 表明,减小送丝速度会增大熔池表面高温区面积,并导致熔池的速度振荡程度增加. 相似文献