喷射成型锭坯形状的数值模拟研究

建立了描述喷射成型过程中沉积坯外轮廓动态生长的三维数学模型,该模型考虑了喷射成型过程中各种工艺参数的影响,这些工艺参数包括喷嘴的雾化特性值、偏心距离、沉积盘的旋转速度和下拉速度,在计算后进行数据处理得出了锭坯生长的三维外形轮廓,通过与实际喷射成型设备成形的锭坯对比,两种结果符合较好,并可用此模型来预测不同工艺条件下锭坯的外形生长轮廓。     

锭坯双喷嘴扫描喷射成形雾化锥沉积轨迹及其耦合研究

双喷嘴扫描喷射成形是提高生产效率和制备大直径锭坯的主要工艺方式.研究了双喷嘴扫描喷射成形工艺雾化锥扫描沉积轨迹及其耦合产生条件.建立了雾化锥沉积轨迹坐标及扫描沉积区域数学模型,分析了工艺参数对沉积轨迹的影响规律,从理论上推导了沉积轨迹耦合条件.对沉积轨迹模型和耦合特性进行了图形仿真.研究表明:沉积轨迹呈"花瓣"形状,由喷嘴偏心距、初始倾斜角、扫描范围角、喷射高度、扫描频率、沉积盘旋转速度确定.通过喷射成形试验对建立的理论模型和研究结论进行了验证,表明了其正确性.     

喷射成形工艺的理论研究进展

喷射成形是人为地控制凝固条件,经过金属熔体的分散、飞行快速冷却、半固态凝固及锭坯进一步冷却等阶段,得到特殊的锭坯组织的成形过程。沉积锭坯组织是上述四个阶段金属熔体凝固的综合结果。近终形成形是喷射成形技术的另一特点,喷嘴形式、喷嘴数量、沉积器的形状与运动方式影响和决定沉积锭坯的外形。材料的凝固与成形受众多因素影响,很多工艺参数的作用规律尚不明确,因此喷射成形过程的模拟研究十分必要。笔者介绍了目前喷射成形工艺中所涉及的理论问题与相关模型。     

基于凸轮驱动喷嘴分阶段变速扫描的锭坯喷射均匀沉积研究

喷射成形技术可以制备出高性能、高质量的工业锭坯,对工业的发展具有重要影响。雾化喷嘴系统是喷射成形装置的核心,喷嘴扫描运动方式对锭坯的均匀沉积有着重要的作用。本文以锭坯均匀沉积为目标,提出了基于凸轮驱动的参数可调的喷嘴扫描方式,建立了喷嘴分阶段变速扫描过程,确定了凸轮形状,对锭坯沉积轨迹进行了仿真并做了分析。最后用喷射成形实验对喷嘴分阶段变速扫描进行了验证,表明了其正确性。     

喷射成形过共晶AlSi合金锭坯的渐变组织研究

喷射成形是通过控制凝固条件,使金属熔体经过雾化分散、飞行快速冷却、半固态凝固及形成锭坯后进一步冷却等阶段,得到特殊的喷射成形锭坯组织的成形过程.沉积锭坯组织是上述四个阶段金属熔体凝固的综合结果.由于散热条件的不同,沉积锭坯组织形态随沉积位置而变化.本文分析了喷射成形锭坯组织的变化情况和形成原因.     

非规则管坯喷射沉积成形工艺优化及试验验证

提出了基于往复式喷射成形工艺制备大璧厚非规则管坯的近终形成形工艺及其工艺参数优化方法,以实现坯件从CAD设计到喷射成形的快速制备过程。该工艺方法包括三个阶段:非规则管坯的三维CAD设计、分层处理和单层沉积厚度计算;基于沉积厚度与往复速度和质量流率的对应关系,计算满足各层沉积厚度所对应的控制参数;利用控制系统和执行机构对控制参数进行实时控制和调节,采用往复式多层喷射成形工艺制备满足设计轮廓的管坯。通过试验进行了验证,喷射成形制备的管坯形状和轮廓与CAD设计模型较好地一致,表明了该工艺方法的可行和正确性。     

喷射成形7055铝合金搅拌摩擦焊的焊缝组织与力学性能

采用全自动控制的往复喷射成形工艺批量生产大规格的7055铝合金锭坯,对喷射成形7055铝合金板材进行搅拌摩擦焊.通过对搅拌摩擦焊塑性连接时的焊缝成形、焊缝组织及力学性能进行研究,实验结果证实:用搅拌摩擦焊焊接4mm厚的7055铝合金板材,选用合适的工艺参数,可获得外形美观、组织无缺陷、无变形的焊缝.焊缝各区域的组织有明...     

喷射成形棒坯中沉积距离和回缩速度的选择

利用计算机数值模拟技术采用平均质量流率法建立了喷射成形空间质量流率分布和棒坯生长模型，通过讨论喷射成形空间质量流率分布得出沉积器的最佳位置hm和最佳回缩速度vo并计算了不同喷射参数对沉积坯端面形貌的影响。     

喷射成形GCr15钢组织及致密化分析

通过使用金相显微镜,扫描电镜对GCr15喷射成形试样和过喷粉末的微观组织和致密度进行分析。喷射成形过喷粉末为枝晶组织,而喷射成形沉积坯由于雾化气体的雾化破碎作用,组织为细小等轴晶,在喷射过程中一些颗粒发生了旋转现象,为结晶过程提供了更多晶核。同时,通过对喷射成形过喷粉末的形貌的研究,得出疏松的形成原因。在此基础上提出了一些改进微观组织和性能的措施。     

喷射成形M42高速钢初生碳化物的细化

喷射成形是一种新型的材料制备技术,可以制备常规工艺无法生产的高合金钢。通过研究喷射成形设备喷制的M42高速钢的组织特点以及采用后续的热处理及热加工等对锭坯组织及碳化物的影响,对比不同热处理温度和不同的热加工工艺对喷射成形M42钢碳化物形态及分布的影响,建立了适当的热处理和热加工制度,从而证明了利用喷射成形生产高合金高速钢的可行性,并且为后续的热加工过程工艺参数的制定提供依据。     

Modeling of spray-formed materials: Geometrical considerations

In this article, a mathematical model is formulated to predict the evolution and final geometry of an axisymmetric billet (i.e., round) obtained using an off-axis spray arrangement. The model is formulated by calculating the shape change of a profile curve of a billet surface, based on an axisymmetric surface. On the basis of this model, a methodology to determine the “shadowing effect” coefficient is presented. The modeling results suggest that there are three distinct regions in a spray-formed billet: a base transition region, a uniform diameter region, and an upper transition region. The effects of several important processing parameters, such as the withdrawal velocity of substrate, maximum deposition rate, spray distribution coefficient, initial eccentric distance, and rotational velocity of substrate, on the shape factors (e.g., the diameter size of the uniform region and the geometry of the transition regions) are investigated. The mechanisms responsible for the formation of the three distinct regions are discussed. Finally, the model is then implemented and a methodology is formulated to establish optimal processing parameters during spray forming, paying particular attention to deposition efficiency.     

A three-dimensional model of the spray forming method

A three-dimensional model has been formulated to calculate the shape of the general preform, using vector calculus. The shape of a rod, tube, plate, or irregular preform can be calculated at given spray forming conditions. The shape of a spray-formed rod was analyzed at various spray forming conditions using the three-dimensional model. The effects of spray forming parameters, such as spray distribution parameters, angular velocity of rotation, withdrawal velocity, spray angle, and eccentric distance on rod shape, were analyzed. The most important parameters affecting the shape of rods are the spray distribution parameters and the withdrawal velocity. The dynamic evolution of rod shape with a stepwise variation of the withdrawal velocity during spray forming was investigated. The effect of a stepwise change of the withdrawal velocity was the same as that of the scanning atomizer. The calculated surface profiles were compared with those of spray-formed 7075 aluminum alloy rods prepared on a pilot scale. The calculated results for the surface profiles were in agreement with those of the spray-formed rods.     

Numerical simulation of tube profile growth during spray forming process

Spray forming is a new type of metal material forming process,which can produce metal blanks such as billet,tube,plate etc.A mathematical model has been developed to forecast the shape evolution of tube billets during the spray forming process.The atomizer mass flux as,radial distribution coefficient bs,draw velocity and diameter of mandrel were considered in this model and the influence of different parameters such as metal flowrate,draw velocity of mandrel,diameter of mandrel on the tube’s shape change were simulated and analyzed in this paper.The simulation results obtained from this model can be provided to engineers as reference.     

Formulation of rod-forming models and their application in spray forming

In rod spray forming, the preform changes its shape continually from that of a disc to a rod (transient-state rod growth) and then maintains its top surface profile once it has settled down (steady-state rod growth). The rod growth mechanism during spray forming was analyzed using rod-forming models. At a sufficiently high substrate rotation velocity, the calculated results based on the three-dimensional time-dependent model (3-D TDM) and the two-dimensional time-dependent model (2-D TDM) were observed to be identical. The calculated results of the rod’s top shape, obtained by the TDMs, were almost identical to those obtained by the two-dimensional time-independent model (2-D TIM), which means that there exists steady-state rod growth. The effects of spray-forming parameters, such as initial eccentric distance, substrate withdrawal velocity, and spray angle, on the shape-evolution behavior were analyzed in terms of the vertex growth velocity ( ). The optimum spray-forming condition to minimize transient-state rod growth was also presented. Experimental verification was made to confirm the proposed forming models.     

Metal Spray Forming Process Examined Using Mathematical Model

The metal spray forming process was examined using the mathematical model simulation by Baosteel＇s test and developed facilities.The mathematical model comprised of the probability and statistical analysis of the droplet mass behavior and predicted the shape and temperature distribution of the billet during the spray forming process.     

铸坯表面热交换系数的测定

建立了铸坯表面热交换系数计算的方程，并将实验测定的数据经过回归，得到了铸坯表面的热交换系数与铸坯表面温度及水流密度的函数关系式，即喷嘴的热态性能。     

Experimental and mathematical modeling of metal spray forming process

The metal spray forming process was examined using mathematical simulation and verified through the prototyping evaluation at Baosteel’s test and development facilities.The mathematical model comprised of four sections,including jet gas flow in the deposition chamber;single droplet behavior along its trajectory path;probability and statistical analysis of droplet mass behavior,and forecast of the shape and temperature distribution of the billet during the spray forming process.     

喷射成形高钒高速钢环坯制备技术研究

采用喷射成形技术制备高钒高速钢环坯,阐述了喷射成形制备过程方法及工艺参数,制备得到的沉积坯收得率为83.5%。对比观察沉积坯不同位置组织及碳化物形貌,发现:组织均匀细小,碳化物颗粒细小、形状较为规则、分布均匀,合金元素无宏观偏析;孔隙及缺陷主要位于沉积坯与基体的结合界面附近,产生于喷射沉积未完全稳定的试验初期。对热处理后的沉积坯试样进行硬度测试,喷射成形高钒钢淬火硬度为63HRC,高于粉末冶金高钒钢;经过3次回火,硬度逐渐下降,未出现二次硬化现象。