榨螺液态模锻工艺实验研究

对螺旋型榨油机中的榨螺零件如何采用液态模锻工艺生产进行了实验研究，分析了该种制件采用液态模锻工艺生产的难点和工艺设计的要点。通过实验，研究了榨螺毛坯液态模锻的主要工艺参数，并分析了榨螺零件采用注态模锻工艺的经济效益。     

薄板坯连铸液芯铸轧过程的三维有限元分析

采用三维弹塑性大变形热力耦合有限元法,模拟薄板坯连铸液芯铸轧过程中的坯壳变形,分析影响铸坯纵向伸长的主要因素,提出动态反向堆钢理论,对有凶模拟结果和在线热带生产（ＩＳＰ）工艺中的铸轧技术做了合理解释。     

Numerical modelling and experimental investigation of diffusion brazing SS304/BNi-2/SS304 joint

Abstract

The kinetics of dissolution and isothermal solidification at the bonding temperature during diffusion brazing SS304/BNi-2/SS304 has been studied through a combination of analytical modelling and experimental investigations. The modelling is based on the diffusion theory and the consideration of transient motion of liquid/solid interface. A set of coupled finite differential equations has been programmed to track the motion of liquid/solid interface during the isothermal solidification of liquid filler. Four parameters can be mathematically determined from the analytical modelling including the evolution of solute concentration profile, the maximum diffusion distance, and the maximum liquid thickness as well as the time to complete the isothermal solidification. These analyses are helpful to understanding the joining mechanism during diffusion brazing. The temperature dependent diffusion coefficient used in the modelling is derived together with the experimental data from brazing the wedge shaped joint specimen of SS304/BNi-2/SS304. The effects of bonding temperature and initial joint thickness on the joining process have also been investigated.     

半固态A356铝合金触变锻造成形过程有限元模拟

针对高固相率条件下半固态触变锻造成形,开发了一个热力耦合触变锻造模拟模型.对触变锻造成形过程中温度场分布、最高/最低温度分布规律以及成形过程中模具运动速度对成形力的影响规律等,进行了计算和分析.研究发现,在半固态触变锻造成形过程中常伴有低于半固态温度的热加工现象出现,高成形速度会降低成形力,同时也会导致成形坯料的液固相分离.试验验证中最大成形力与模拟得到的最大成形力相吻合的事实表明,所开发的计算模型能较准确地预测触变锻造成形最大成形力, 但成形过程中两者所得到的成形力仍存在一定差异,这表明计算模型还需要一步优化.     

铝合金间接挤压铸造抽芯力的分析与计算

带孔零件间接挤压铸造时,液态金属在压力下凝固收缩对型芯产生的包紧力。包紧力的大小与铝液浇注温度、 成形压力、孔径尺寸、模型材料的物理性质等有关。通过对铝合金挤压铸造成形时的凝固分析,推导出了芯轴抽芯力的计 算公式,该计算式也适用于其他液态金属成形方法。     

半固态模锻变形机制研究

通过帽形件的半固态模锻成形,阐述了半固态浆料变形的物理模型,研究了半固态浆料变形过程及变形机制。实验表明:半固态浆料模锻成形的变形方式是不同的,不同的固相率下其固液两相的塑性流动机制也是不同的;而且制件不同部位的微观组织形貌也有差异。     

连铸坯液芯压下工艺

液芯端部微压下工艺能够减轻铸坯中心偏析，微压下量由消除偏析和防止裂纹产生两个因素决定。中厚板坯高速连铸机采用液芯压下工艺可实现薄板坯连铸，为了防止内部裂纹产生，在凝固初期进行压下是有效的。     

Liquid forging of thin Al–Si structures

Liquid forging is a pressurized solidification process, wherein finished components can be produced in a single process from molten metal to solid, utilizing re-useable die tools. In conventional die casting (gravity and pressure), components with a minimum wall thickness of about 0.6 mm can be fabricated. However, parts with section thickness as thin as 0.2 mm can be liquid forged using near eutectic Al–Si or Al–Si–Cu alloys. Water based lubricant containing micrographite is effective in releasing the component during ejection. In addition, it aids in shaping the component to required dimensional accuracy. These liquid forged parts are pore free. Thermal analysis of liquid forged 0.8 mm plate revealed rapid freezing at the rate of about 700 °C/s. During the process, die and punch were maintained at 200–250 °C. X-ray residual stress analysis on the surface of the liquid forged plate showed high intensity values for 0.1 mm plate. Distribution of eutectic silicon at inter dendritic region is extremely fine to nanoscale level.     

铸坯模锻中的力学特征分析

在基础实验研究，理论分析，应用研究的基础上，重点对铸坯模锻变形过程吕应力状态对消除铸态组织的影响进行了较深入的分析。同时提出了铸坯模锻应力状态下合理选取锻造比的基本原则和依据。分析研究结果表明：铸坯在模锻中，力学特征有利于提高其机械性能，确保锻件质量。     

白铜管热型连铸的温度场

采用在铸型上定点检测温度,再用ANSYS分析软件计算温度场的方法,研究了铸型温度、冷却距离、连铸速度等工艺参数对白铜管热型连铸温度场的影响.根据温度分布曲线,求出了凝固前沿固液两相区的长度和位置,分析了工艺参数对两相区长度和位置的影响,以及由此对连铸过程和铸件质量的影响.在正确选择工艺参数从而确定两相区位置后,顺利连铸出直径10 mm、壁厚2 mm、表面光滑平直的白铜管.     

Experimental research on cutting force variation during regenerative chatter vibration in a plain milling operation

A plain milling operation is characterized by a transient and intermittent cutting process, in which undeformed chip thickness varies continuously. The reverse is the case in variations of undeformed chip thickness in the processes of up- and down-milling. In the present study, the property of regenerative chatter vibration in a plain milling operation is investigated from the viewpoint of cutting force variation. With primary chatter vibration, the vibration energy supply is closely related to the collision of the cutting tool flank against the workpiece surface during vibration, which is induced by the bending vibration or the torsional vibration of the arbor. In addition to this factor, the regenerative effect is considered to be one of the main causes of the chatter excitation in regenerative chatter vibration. The simulation result of the cutting force variation during regenerative chatter vibration agrees well with the experimental result, when considering these factors. It is shown that the regenerative chatter vibration in the-down-milling process occurs more easily than in the up-milling process.     

材料表面润湿性的影响因素及预测模型

目的预测不同材料表面和液体之间的润湿性能。方法选取9种不同板材以及14种实验液体,采用60—1200目砂纸打磨所有平板,得到具有不同粗糙度和表面能的实验材料。利用控制变量法,分别研究了液体表面张力、固体粗糙度和固体表面能对接触角的影响。然后进行了三因素十水平的均匀设计实验,并应用SPSS软件对实验结果进行了线性分析。结果在不同液体的作用下,随着表面张力的增加,接触角不断增大,其中蒸馏水的表面张力最大,为70.13 m N/m,其在三种材料中的接触角也最大。在具有相同粗糙度的材料表面,随着表面能的增加,接触角减小,固体表面能最大(67.72 m J/m2)时,接触角达到最小值,为25.1°。在具有相同表面能的材料表面,随着粗糙度的增加,接触角呈现两种相反的趋势:当θ90°时,随着粗糙度的增加,接触角不断增大;θ90°时,随着粗糙度的增加,接触角不断减小。通过均匀设计得到了接触角的预测模型,发现液体表面张力对接触角影响的权重最大,固体表面能次之,粗糙度最小。结论通过SPSS软件拟合得到了真实材料表面接触角与其影响因素的定量关系式,针对现场管材和液体的选型进行了理论指导,从而有效降低了输送过程中的阻力损失。     

液态模锻的工艺特点与模具材料选用

简述了液态模锻的工艺过程，特点，国内外一些研究状况和上前主要研究方向，介绍了液态模锻模具的基本结构，服役条件，对模具性能的要求，及模具材料的主要选用原则。     

Improvement of the liquid segregation phenomena of semisolid aluminum alloys by the multistage strain rate control in the compression test

The deformation behavior of semisolid aluminum alloys in the range of solid fraction (f _s ) between 55 and 90% was investigated through compression tests for the variation of strain rate. In order to obtain the optimal conditions of the net shape forging process, the rheological behavior of aluminum alloy in the semisolid state has been examined by using parallel plate compression. The strain rate is the value of the strain rate corresponding to the stress to avoid the liquid segregation phenomena during compression tests. The material constants of semisolid material in the stress-strain curve are proposed to perform the numerical analysis for a die design of semisolid forging. The starting materials used in this experiment are A357, 86S (similar to A319), and A390 alloys, which are fabricated by the electromagnetic stirring process. The intelligent compression test with a controlled strain rate was performed. The liquid segregation in the overall cross-sectional areas is controlled as the multistage variation of the pressing velocity and variation of the solid fraction during the compression process. The characteristics of materials flow between solid and liquid phases, considering the liquid segregation, are discussed for various solid fractions and pressing velocities.     

液态模锻力学成形理论的研究

液态模锻既是一个物理化学（凝固）过程，亦是一个力学成形（塑性变形、强制补缩）过程，两者的复合，便形成了液态模锻自身理论。本文重点放在力学成形过程方面，力图利用金属塑性加工理论，结合液态模锻本身的特点，从理论和试验的结合，计推液态模锻力学成形理论的最新研究成果。     

液态正挤压工艺试验研究

液态挤压是在液态模锻基础上发展起来的管材成形方法。本文给出了液态正挤压过程的实质、管材成形模具和工艺参数、试验结果及其分析,为完善和推广该工艺提供了依据。     

连铸坯锻轧工艺对核电用特厚钢板内部质量和力学性能的影响

研究了采用300 mm厚连铸坯锻轧生产核电特厚钢板的工艺,通过对连铸坯直轧、模铸和连铸坯锻轧3种不同工艺生产的核电特厚钢板内部质量和力学性能进行对比分析,结果表明：连铸坯直轧工艺生产的特厚钢板不能满足NB/T47013-2015《承压设备无损检测》Ⅰ级和GB/T 5313《厚度方向性能钢板》Z向断面收缩率大于35%的要求,钢板内部存在裂纹和偏析。采用锻轧工艺生产的钢板能够100%满足探伤要求,连铸坯芯部裂纹和柱状晶在高温锻造过程中能够有效焊合和破碎,并且高温加热过程对连铸坯的芯部偏析有很大程度的改善,通过锻造和轧制工艺相结合,能够解决连铸坯直轧出现的探伤不合问题,并且能替代高成本的模铸生产,进一步降低生产成本。     

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。     

Internal void closure during the forging of large cast ingots using a simulation approach

Large cast ingots often contain defects or undesirable microstructural features, such as voids and zones related to casting. Some of these features can remain after hot open die forging, which is an important process for converting large cast ingots into wrought components. During the initial cogging and deformation steps prior to the detailed open-die-forging operations, any internal voids should be eliminated. The present work focuses on the closure of internal voids during open die forging so as to produce a sound component. Hot compression tests were conducted to obtain the flow strength of the cast microstructure at different temperatures and strain rates. The measured flow strength data together with other appropriate material properties were used to simulate the forging steps for a large cast ingot. The numerical simulations for the forging deformation and for the internal void behavior were performed using DEFORM-3D™. Actual defects were measured in commercial ingots with an X-ray scanner. The simulation results for the void deformation behavior are compared with voids measured before and after forging. Through the comparison of experimental results and numerical simulation, a criterion for void closure is proposed. The criterion is that a local effective strain value of 0.6 or greater must be achieved for void closure during forging. Such a criterion can be used in conjunction with simulations to insure that a sound component is produced during the hot open die forging of large cast ingots.     

液室压力对异形长法兰盒形件充液成形过程的影响

异形长法兰盒形件由于法兰面积大,拉深成形时法兰区的材料流动困难,易出现开裂缺陷。通过对比分析壁厚分布的试验与仿真结果,证明了仿真分析具有可靠的准确度。利用实验与仿真相结合的分析方法,分析异形长法兰盒形件充液成形过程中初始反胀与成形压力的影响机理,优化液室压力加载路径,建立关于初始反胀压力与初始反胀高度的工艺窗口,用于指导该类零件初始反胀参数选取。分析结果表明:异形长法兰盒形件充液成形过程中,初始反胀压力与初始反胀高度过小,导致异形长法兰盒形件凸模圆角处破裂,初始反胀压力与初始反胀高度过大,导致异形长法兰盒形件凹模圆角处破裂;最大减薄率随着成形压力的增加,先减小后增加。