空心坯料反挤压省力成形方法及应用研究

采用主应力法与数值模拟相结合的方法,研究分析空心坯料反挤压成形力变化规律。结果表明,空心坯料反挤压在减少接触面积的同时,减小了接触面上的单位变形力,大幅度降低了挤压成形力。经在重型车辆铝合金轮辋成形中验证和应用表明,该方法可行,为底部带中心孔的大型薄壁筒形零件的成形,提供了新思路。     

Numerical modelling of the material flow during extrusion of aluminium alloys and transverse weld formation

A comprehensive numerical model of the hot extrusion process for aluminium alloys has been developed and validated. Reflecting the complex thermomechanical changes effected in the alloys during extrusion, the model incorporated heat flow and plastic deformation during extrusion. This paper presents the overall numerical development of a hot extrusion process for AA3003 and validation of the numerical model, by comparison to industrial data. The plasticity module was developed using a commercial finite element package, DEFORM^®, a 2-D transient Lagrangian model which couples the thermal and deformation phenomena and is able to predict the temperature, strain rate and strain distribution in the billet/extrudate at any position in the container and die. A new algorithm using MATLAB was also developed so that details of the material flow and formation of the transverse weld and how it is affected by the feeder geometry could be quantified. Validation of the DEFORM model and the MATLAB algorithm of the material flow against industrial data indicated that it gave excellent predictions of the pressure and temperature history during extrusion as well as material flow effects such as surface cladding as one billet is fed in after another through the die. The results indicated that the die feeder design has a significant effect on the transverse weld formation with tapered dies showing lower transverse weld lengths compared to regular feeder plates.     

Effect of Extrusion Conditions on Metal Flow and Microstructures of Aluminum Alloys

Study of metal flow in extrusion billet is fundamental and useful to understand extrusion technology. Investigation of behavior of extrusion billet skin and microstructure of products is indispensable to maintain qualities of extrusions. In order to research the behavior, experiments and FE analysis of clad billet extrusion were performed. The analytical results of billet skin deformation were similar to that in experiments. Friction between back end of billet and ram affects the deformation of skin and its penetration into billet. Secondly, microstructure of an extruded product is predicted and the condition of recrystallization and grain refnement is revealed.     

Comparison of extrusion strains produced by cosine and conical dies

Visioplastic analysis is used to compare strain fields produced in cylindrical aluminum billets extruded at elevated temperature through axially symmetric dies that have either a cosine or a conical profile. The visioplastic method consists of computing strain rates from changes experienced in a flow function as a billet passes through the extrusion die. The flow function is constructed using a grid that is stamped on an axial plane of the billet before extrusion. After the partially extruded billet is removed from the die numerical methods are used to determine the strain rates from the deformed grid. The state of strain over the extrusion region is computed using transformation and then integration of the strain rates. Results show that, unlike the conical die, the cosine die does not produce strains of reversed sign in the die entry region. The consequent benefits of using cosine dies for extrusion of powder metals are discussed.     

凸缘远离大端的半轴套管成形工艺实验研究

按凸缘能否一次成形,将半轴套管分为凸缘靠近大端（A）和凸缘远离大端（B）两类,简介了B类半轴套管成形工艺现状;经分析、数值模拟和物理模拟实验研究,开发了一种以圆棒材为坯料,以“闭塞模锻＋复合挤压”为主要过程的B类半轴套管成形新工艺,重点介绍了设计中间制件所考虑的因素和解决的问题,实现了工步少、凸模刚性好、所需设备滑块行程较短等目的。     

Investigation on Effects of Die Orifice Layout on Three-Hole Porthole Extrusion of Aluminum Alloy 6063 Tubes

Currently, with the increasing demand of high production output, much attention is paid to the research and development of multi-hole extrusion die. However, owing to the complexity of multi-hole porthole extrusion technology, it has not been applied widely in practice for the production of aluminum profiles, especially for porthole die with an odd number of die orifices. The purpose of this study is to design a three-hole porthole die for producing an aluminum tube and to optimize the location of die orifices based on computer-aided design and engineering. First, three-hole extrusion dies for different locations of die orifices are designed. Then, extrusion processes with different multi-hole porthole dies are simulated by means of HyperXtrude. Through numerical simulation, metal flow, temperature distribution, welding pressure, extrusion load, and die stress, etc. could be obtained, and the effects of the location of die orifices on extrusion process are investigated. With the increasing distance between die orifice and extrusion center (described as eccentricity ratio), metal flow becomes nonhomogeneous, and twisting or bending deformation of profile occurs, but the welding pressure rises, which improves the welding quality of profiles. However, the required extrusion force, billet and die temperature, die displacement, and stress induce no significant changes. In comparison with the extrusion force during single-hole porthole extrusion, there is 18.5% decrease of extrusion force during three-hole porthole extrusion. Finally, design rules for this kind of multi-hole extrusion dies are summarized.     

Simulation on extrusion process of TiAl alloy

The rigid-plastic finite element Deform-3D software was employed to describe the plastic deformation behavior of TiAl billet (Ti-46.5Al-2.5V-1.0Cr-0.3Ni alloy) during its axisymmetric extrusion through a conical die. Under various extrusion conditions, the present numerical analysis investigated the strain distribution, the damage factor distributions and the die load during the extrusion process. The relative influences of the die semi-angle and the extrusion ratio were examined. The results show that the extrusion force was enhanced from 1.54 × 10⁶ N to 2.81 × 10⁶ N with a certain slop coefficient (about 0.04) when die semi-angle increased in the range 40°≤ α ≤ 70°. The uniform effective strain and the lower propensity for fracture could be obtained at the 60° die semi-angle. The 60° die semi-angle will be an appropriate choice for the extrusion of TiAl alloy. With the raising of extrusion ratio, the effective strain, extrusion load and the damage factor in billet would also be increased.     

国外铝挤压技术及其装备的进展

介绍了国外挤压机在工艺、机械、液压和自动控制方面的技术发展,着重叙述等温挤压、高速挤压、挤压工艺参数优化和反向挤压等先进技术以及为实现等温挤压和高速挤压所采取的铸锭梯温加热、挤压减速控制、模具冷却等措施。对先进挤压机的结构、计算机控制系统等作了简要介绍。     

半轴套管多工位挤压自动化生产线中冲连皮缺陷产生机理及参数优化

针对半轴套管多工位热挤压自动化生产线工艺调试过程中,正挤压工序冲连皮时,管端易出现连皮粘连缺陷的问题,探讨了有可能造成连皮粘连的原因。通过对工艺流程和现场情况进行综合分析,提出了圆柱形坯料周向温度加热不均是关键的影响因素。采用Deform有限元分析软件,模拟了不同加热温差条件下,反挤压和冲连皮时材料变形及材料剪断过程。通过对模拟结果的分析,揭示了连皮粘连机理,并可知,当坯料周向加热温差小于30℃时,连皮可顺利冲下。根据模拟得出的合理温差,进行现场试验,实际情况与模拟结果具有较高的一致性,生产出的产品锻件切口平齐、连皮撕裂带分布均匀,有效地解决了连皮粘连的问题。     

轮辋挤压成形数值模拟研究

采用MARC/superform软件对轮辋挤压成形进行了数值模拟,得到了变形过程的金属流动规律。在保证零件成形及能耗最小的前提下,获得了毛坯及模具锥角的最佳值。     

小规格TiNiNb管材的反向挤压成形工艺参数

针对44 mm×10.5 mm小规格Ti Ni Nb管材反挤压成形试验的工艺参数确定和模具设计问题,采用有限元热力耦合数值模拟和单因素轮换法,分析在满足制件成形质量(挤出温度低于共晶熔点)的前提下,挤压力与凹模模角和定径带长度、凹模和挤压筒温度、毛坯初始温度、挤压速度及摩擦因子等工艺参数和模具结构参数之间的关系,确定影响挤压力的主要工艺参数和模具结构参数分别为凹模模角、初始坯料温度、挤压速度和摩擦因子,并给出上述参数的取值范围。通过基于数值模拟的正交试验方法,得到了主要工艺参数和模具结构参数的最佳组合,即在保证润滑效果的前提下,取凹模模角110°、毛坯初始温度为950℃、挤压速度为50 mm/s。利用铅和45号钢毛坯在6.5 MN多向模锻挤压液压机上进行了验证实验。     

316不锈钢异形Ⅰ截面型材挤压成形过程有限元模拟

以异形Ⅰ形截面不锈钢型材为研究对象,采用DEFORM-3D有限元软件系统对其热挤压成形过程进行数值模拟分析.研究了挤压稳态成形过程中挤压速度、摩擦系数、坯料预热温度等因素对不锈钢型材挤压过程的影响.计算结果表明,当挤压比为9、挤压速度为200mm/s、摩擦因子为0.3、模具预热温度为450℃、坯料预热温度为1050℃时,金属流动状况良好,材料的应力应交分布均匀,可有效提高模具的寿命,对指导实际生产具有积极的参考价值.     

基于数值模拟的渐开线花键件冷挤压工艺参数优化

基于弹塑性有限元数值模拟技术,使用MSC/SuperForm软件对传动轴渐开线花键冷挤压成形过程进行了数值模拟,通过改变工艺参数,分析了坯料直径、凹模入口半角和定径带宽度对挤压工艺的影响,并优化出最佳参数。根据优化结果进行冷挤压试验,得到质量合格的制件,为花键类汽车件冷挤压成形工艺的制定提供了依据。     

微成形热挤压试验及模具设计

介绍了采用半固态ZL101铝合金进行挤压成形微型齿轮的试验研究,设计了挤压模具和加热及温控系统.试验结果表明,挤压过程中的坯料温度对零件质量产生重要影响,它决定了半固态合金的触变特性,合适的半固态加工技术可以成形微型零件.     

UBET analysis of process of extruding aluminum alloy ribbed thin-wall pipes through a porthole die

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Uniformity and continuity of effective strain in AZ91D processed by multi-pass equal channel angular extrusion

AZ91D magnesium alloy was processed by equal channel angular extrusion（ECAE）. The influence of extrusion temperature, extrusion pass and extrusion route on the ultimate strength of the extruded billet was analyzed. The process of multi-pass extrusion was simulated with the method of finite element analysis, and the continuity and uniformity of effective strain in multi-pass extrusion were investigated. The results show that extrusion pass plays the most important role in improving the ultimate strength of AZ91D magnesium alloy, the extrusion route is the second, and the extrusion temperature is the last, From the numerical simulation, there exists the continuity of the accumulated deformation in multi-pass extrusion and the effective strain increases linearly. The tendency of the strain uniformity is different in multi-pass extrusion with extrusion routes. The results of experiment agree with those of numerical simulation.     

非贯通内齿轮冷挤压成形工艺研究

针对目前内齿轮主要靠机械加工成形,齿件强度不足、材料利用率低和加工成本高等问题,提出采用冷挤压技术成形非贯通内齿轮的工艺方案.根据初始坯料形状将工艺方案分为两种,即实心坯料冷挤压和带中心孔坯料冷挤压,指出各自的加工工序,并提出齿形凸模设计的具体要求;通过数值模拟方法,从成形载荷、有效齿高、齿件精度及模具强度等方面对两种挤压工艺方案进行系统研究,得到这两种工艺方案各自的适用条件.研究结果对实际生产有一定的指导作用.     

铝锅冷挤压工艺及模具设计

叙述了铝锅塑性成形的工艺分析,设计冷挤压件、计算毛坯形状及尺寸,验算许可变形程度、计算冷挤压变形力。介绍了铝锅冷挤压工艺及模具结构。最后指出了冷挤压工艺的优点。     

A three-dimensional steady-state finite element analysis of square die extrusion by using automatic mesh generation

Steady-state finite element analysis is made for three-dimensional hot extrusion of sections through square dies by using an automatic mesh generator which can generate three-dimensional meshes by shifting two-dimensional meshes. In industrial practice, the design of extrusion dies is still an art rather than science, especially for complicated profiles, because the die design for a new extrusion is developed from previous experience and in-plant trials. The objective of this study is to develop a steady-state finite element method for hot extrusion through square dies, and to provide a theoretical basis for an optimal die design and process control for the extrusion technology. In the present investigation, steady-state assumption is used for both the analyses of deformation and temperature. The analysis of temperature distribution includes heat transfer, and is carried out by decoupling from the analysis of deformation. Convection link element is adopted for the heat transfer analysis between the billet and the container, and also between the billet and the die. Computations are carried out for solid and hollow extrusion of several sections. The present method of analysis has been shown to provide good results comparable with the non-steady-state method with reduced computation time. Distributions of temperature, effective strain rate, velocity and mean stress are discussed for effective design of an extrusion die.     

汽车空调平行流多孔管的连续挤压技术

为了解决汽车平行流多孔管连续挤压过程中模具孔针断裂和产品焊合质量不好的问题,采用LLJ300铝连续挤压机,研制成功了具有凸模侧面加强筋、预成型模和具有分流通道的汽车空调平行流多孔管连续模具和腔体,有效解决了平行流多孔管连续挤压过程中存在的技术难题,并已应用于工业化生产.