Estimation of plastic deformation and abrasive wear in warm forging dies

In warm forging, die life is affected by abrasive wear and plastic deformation and may be shortened considerably due to thermal softening of the die surface caused by forging temperature and pressure. In this study, a methodology is developed for estimating abrasive die wear and plastic deformation in a warm forging operation, using a tempering parameter. This methodology consists of: (a) determination of the steady state die temperatures using multiple FE simulations, (b) using the calculated temperatures to predict the plastic deformation of the dies, (c) measuring the surface profile of the worn dies using a Coordinate Measuring Machine (CMM), (d) identifying the wear profiles caused by abrasive wear and plastic deformation, and (e) determining the abrasive wear parameters that can be used for future estimation of die wear in warm forging. The predictions have been compared with experimental results and it was concluded that this method can be used for estimation of die failure (wear and plastic deformation) in hot/warm forging.     

The Effect of Temperature Condition on Material Deformation and Die Wear

The characteristics of temperature change on die and billet are very complex during the deformation process because of the interaction between them and some unstable external factors. In this paper, the numerical simulation model for the crank shaft die forging was established by means of the rigid-plastic FEM method. The model was validated by optical non-contact 3D measurement—ATOS. Based on available research results, this paper explored the effect of temperature conditions on material deformation and die wear. Three parameters, press velocity and initial temperature of billet and die, were chosen to illustrate the effects. From the experimental results, the effect of process parameters on deformation ability of the material is simple, while the effect on die wear is relatively complicated. The press velocity plays an important role on die wear when the initial temperature of the billet has larger influence on material deformation. A conclusion can be drawn that when the initial temperature of the billet is 1100 °C, the initial temperature of the die is 250 °C, and the velocity is kept in the range of 200-300 mm/s, the optimum solution for deformation ability of the material and die wear can be obtained. It is possible for the conclusion to be extended further for the control of temperature condition to optimize die life and material deformation.     

Ti6242S钛合金盘形锻件锻造及热处理工艺研究

采用260 mm钛合金棒材,以锤锻和压机锻造的方式试制了Ti6242S饼坯和盘形锻件,研究了锻造及热处理工艺对显微组织、力学性能以及超声检测杂波水平的影响。结果表明:压机锻出的饼坯组织和性能更优;随着固溶温度的升高,锻件初生α相减少,杂波降低;经制坯、压机锻造、热处理,锻件可获得较优的组织和性能。     

转向节热挤压方案工艺性对比分析

采用有限元数值模拟方法以某汽车转向节不同热挤压方案为研究对象,从填充性能、飞边铺展均匀性和流线分布等方面分别作了对比分析研究.结果表明:转向节挤压生产时应避免采用大高径比的坯料直接挤压;采用大直径规格的坯料具有最好的杆部填充性能;采用镦挤加拍扁的预制坯方案可获得较好的综合填充性和变形均匀性.变形方式对锻件最终流线分布的影响最大;初始坯料的流线状态和变形程度对最终锻件的流线状态有重要影响;采用镦挤加拍扁的预制坯方案可获得最好的挤压件流线分布状态.镦挤加拍扁的转向节热挤压预制坯方案具有最优的综合工艺性能.     

多台阶轴头短流程冷精锻成形工艺

针对某型号多台阶轴头形状尺寸及冷精锻工艺特点,采取挤压、镦粗、缩径等不同工艺在工序内结合应用的方法,制定了多台阶轴头短流程冷精锻成形工艺。通过数值模拟和实验研究相结合的方法,对所制定的工艺进行分析研究,最终获得了两道工序成形8个台阶尺寸的多台阶轴头短流程冷精锻成形工艺,并在实验过程中采用了高分子润滑剂,进一步缩短了从下料到最终成形的整个工艺流程。结果表明:通过合理分配各工序变形量、工序内多种冷锻工艺结合应用的方法,可有效减少台阶轴冷精锻成形工序总数,实现在普通压力机上的高效率生产;Deform-3D模拟软件对工艺的模拟结果与实验结果相一致,说明有限元模拟对成形效果、压力大小的预测是可行的。     

响应面法在大锻件微观组织质量控制中的应用

以某T型截面大锻件分段多道次成形工艺为研究对象,引入数学统计工具-响应面法(RSM)对该分段、不连续变形下的组织均匀性控制问题进行了研究。将工艺条件-道次进行参数表征,采用有限元方法 (FEM)和响应面法相结合,建立了以改善锻件微观组织质量为评价目标,以坯料温度、压力机速度、上模斜角角度和道次表征量为设计变量的二阶响应模型。研究了设计变量与评价目标之间的作用规律,通过Matlab软件得到了最优锻造工艺和工艺参数组合,即采用3道次成形工艺,坯料温度为440℃,压力机速度为8 mm·s-1,上模斜角角度为160°。采用优化结果进行大锻件的生产试制验证,金像分析显示所成形锻件内部组织均匀,表明了应用RSM和FEM可以有效地对分段多道次成形工艺下的锻件组织均匀性进行控制。     

触变模锻成形工艺对镁合金成形件力学性能的影响

采用半固态等温热处理法、近液相线模锻法和等通道角挤压法制备AZ91D—Y镁合金半固态坯料。分别将3种状态的坯料加热到半固态温度区间进行二次重熔后,进行了触变模锻成形。结果表明,在半固态温度为560℃,模锻压力为200MPa的条件下,半固态等温热处理法、近液相线模锻法和等通道角挤压法制备坯料分别保温30,20,15min后触变模锻获得最佳力学性能;随着坯料加热温度的升高,触变模锻成形件力学性能呈现先上升后下降的趋势;增加成形压力有利于触变模锻成形件力学性能的提高;在相同成形条件下,等通道角挤压法制备坯料触变模锻后的力学性能最好,近液相线模锻法次之,半固态等温热处理法较差。     

工业纯铝等通道球形转角膨胀挤压变形的力学与摩擦学性能

对传统等通道转角挤压工艺(equal channel angular extrusion,ECAE)进行改进,提出一种新型剧烈塑性变形法(severe plastic deformation,SPD)——等通道球形转角膨胀挤压(equal channel angular expansion extrusion with...     

有限元模拟TC11叶片等温锻坯料温度对成形的影响

本文选用了两种不同温度的坯料进行模拟分析,温度分别是915℃、935℃。TC11钛合金叶片压制采用等温锻工艺,可有效消除叶片内的冷模组织,显著提高叶片内温度分布均匀性。模拟结果显示,两种温度坯料均满足等温锻工艺要求。但是坯料温度较低时,成形完整时需要较大成形载荷,模具磨损也更明显。坯料最高温度不能超过935℃,最佳区间为925℃~935℃。其中坯料温度为935℃对于降低成形载荷更加有利。     

Inheritance of the initial structure in steel 4Kh5MF1S after a finish heat treatment

The life of dies and press molds that fail due to abrasion is determined predominantly by the structure and properties of the surface layers, which change most when operating under a cyclic effect of the temperature and pressure. For this reason, the use of methods of surface strengthening is an effective way for increasing the service life of dies and press molds. An analysis of premature failure of some batches of molds for pressure casting has shown that they were fabricated with distortions of the technological process, namely, deviations from the forging temperature regime and an insufficient degree of deformation (forging without fiber entangling, often practiced in forge shops). The structure formed in forging is preserved in the quenched and tempered state. After the finish operation of nitriding the deformation in such press molds increases (the sizes of the tool change), cleavage develops in the operation, and the strengthened layer scales off. The aim of the present study consists in establishing an interrelation between the structure attained in the first stage of fabricating the press mold (after forging) and the structure attained after the subsequent operations of annealing, quenching, tempering, and nitriding. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 11–13, May, 1997.     

Optimisation of flow balance and isothermal extrusion of aluminium using finite-element simulations

There is significant demand to reduce variations in the shape and mechanical properties of the aluminium extrusion process to meet tighter tolerance requirements. To reduce variations, the flow and temperature evolution in the container and die must be controlled. To study how the process parameters influence the temperature evolution and the material flow, the effects of ram speed, initial temperature distribution in the billet and container cooling rate have been studied. This work is divided into three parts which examine the different aspects of the extrusion process. (1) To minimize the radial variations of temperature and velocity fields over multiple press cycles. (2) To obtain isothermal extrusion of aluminium. (3) To understand and formulate the effect of an undesired lateral temperature gradient in the billet on the exit velocity of the aluminium sections. In each part, the effect of different process parameters on the flow balance and temperature evolution of the extruded sections is shown and discussed.     

轮毂轴管终锻成形模拟研究

根据某规格汽车轮毂轴管零件的形状尺寸特点,设计了预锻毛坯和2种终锻成形方案,并对所制定的2种终锻方案进行了工艺和模拟分析。2种方案的模拟结果显示,顺序成形过程稳定,变形只局限于端部;一次镦粗变形不局限于变形的端部,在变形结束时有少量金属流入杆部,这将会使端部缺料和杆部出现折叠和缩径缺陷。顺序成形可改善模具的受力状况,成形力有所降低,提高了模具寿命。根据力一行程曲线,应严格控制变形部位金属的体积,实现小飞边精密锻造,避免成形力在成形最后阶段急剧增大,以致损坏模具和设备。     

神经网络在模具型腔温升预测中的应用

挤压成形过程中由于坯料和模具之间的滑动接触摩擦和坯料的塑性变形产生热而使模具型腔表面温度升高,加剧模具的磨损。采用热力耦合有限元法计算挤压成形过程中模具型腔表面的温升,将模拟结果与人工神经网络相结合,以有限元模拟结果作为学习样本,训练BP神经网络模型,以此模型预测模具型腔表面的温升。根据预测结果分析了挤压锥角、挤压速度和摩擦系数对型腔温升的影响,为进一步建立挤压成形过程中模具型腔表面的温升模型和磨损预测模型奠定了基础。     

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。     

Computer modelling of tool loads and press/tool deflections in multistage forging

A mathematical model of the deflections arising during forging in a multistage press provides the basis for the development of a computer package which can be used to predict the dimensional changes in workpieces occurring at each stage, due to a change at any one stage and individual tool loads and total press load for any given set of conditions. The program can be used to speed up tool setting times by enabling the correct shut-heights for each forming stage to be determined without trial and error. It can be used also to investigate the effects of changes (either deliberate or unintentional) in process conditions such as: lubrication, billet volume or hardness, on the dimensions of the finish forged component. The program has been validated by comparing its output with the results of experiments comprising: single-stage, two-stage and three-stage forging undertaken on a vertical crank press.     

Process optimization diagram based on FEM simulation for extrusion of AZ31 profile

The ram speed and the billet temperature are the primary process variables that determine the quality of the extruded magnesium profile and the productivity of the extrusion operation.The optimization of the extrusion process concerns the interplay between these two variables in relation to the extrudate temperature and the peak extrusion pressure.The 3D computer simulations were performed to determine the effects of the ram speed and the billet temperature on the extrudate temperature and the peak extru...     

差温无模预成形锻造的有限元模拟研究

利用热力耦合有限元方法 ,对AISI10 4 5钢圆柱体坯料在环形加热源局部加热下的差温无模预成形锻造过程进行了模拟研究。模拟结果表明 ,在坯料中获得和控制大梯度分布的不均匀温度场是实现无模预成形锻造的关键。复杂零件成形必须合理地组合加热源和冷却源 ,以便产生所需的温度梯度场。在快速变形条件下 ,变形过程中的持续加热对金属的流动影响甚微 ,变形前的温度分布基本上决定了金属的流动 ,但在慢速变形条件下 ,变形过程中的持续加热对金属的流动产生一定的影响 ,其影响程度视零件复杂程度而异。从该文研究结果可以预见 ,差温无模锻造可以发展成为一种无模锻造制坯新工艺     

Forming limit of magnesium alloy at elevated temperatures for precision forging

Workability of magnesium alloy (ZK60) is investigated by the upsettability test and the results are applied to precision backward extrusion at elevated temperatures. In the upsettability test, cylindrical billets are compressed with concentrically grooved tools at a temperature range of 100–400 °C to obtain the critical reductions in height due to cracking and the flow curves. In backward extrusion, the container is heated to the same temperature as the billet, and the cups are formed with a mechanical press without using lubricant at temperatures from 100 to 300 °C. The finite element simulation is conducted to determine the limit of forging with two fracture criteria.It is found that the billet is brittle at temperatures lower than 200 °C. A transient phenomenon is observed at 200 °C: the specimen is fractured at a small strain in the upsettability test, while the cups are extruded without cracks at extrusion ratios greater than 3.7. The Mg alloy shows an excellent workability at temperatures from 250 to 400 °C. Temperatures higher than 400 °C are not suitable for forming of the Mg alloy because of heavy oxidation. The fracture criterion expressed by the maximum tensile stress is effectively used for predicting the forming limit of the Mg alloy at temperatures between 100 and 200 °C.     

基于BP-GA的大锻件过渡区宏观成形性能优化

针对铝合金大型锻件局部加载成形工艺下过渡区筋部充填不满的问题,借助于BP神经网络和GA遗传算法与数值模拟技术相结合的策略对锻件的局部加载成形工艺参数进行了研究。以锻件过渡区填充性作为质量评价目标,建立了坯料温度、压力机加载速度、第1道次压下量、进给量与质量指标之间的关系模型,利用遗传算法求解得到了合理的工艺参数:坯料温度为435℃,压力机加载速度为5 mm·s-1,第1道次压下量为18 mm,进给量为1165 mm,并将得到的工艺参数进行再模拟,并应用于生产试制,生产后的锻件筋部过渡区充填完整,对比模拟结果,表明所提出的策略能有效对大型锻件局部加载成形过渡区充填问题进行控制。     

汽车发电机爪极闭式一火两锻成形工艺研究

在对汽车发电机爪极零件结构分析的基础上,提出了基于结构拆分的爪极闭式一火两锻成形工艺和对应的模具,该工艺先径向墩挤成形出爪极基座部分,然后再反挤出爪齿和中间凸台.利用Deform- 3D建立了工艺过程的热力耦合有限元分析模型,并得到了成形过程中坯料形状变化、材料流动和成形载荷等情况.结果表明:该工艺能够获得齿形充填完好...