钢锭内部孔隙性缺陷锻合过程的数值模拟

通过比较圆柱体试样内部孔洞锻合过程的模拟计算结果和实验结果,确立了钢锭内部孔隙性缺陷锻合过程的模拟法,并对长孔型缺陷和短孔型缺陷的锻合过程进行了计算,得到各类孔洞的闭合规律,且定量给出了不同位置处孔洞闭合时所需的临界压下率。从孔洞闭合的力学本质角度,对钢锭内部的等效应变分布情况进行了研究。结果表明,孔洞的闭合完全是由于应力集中并达到一定程度的变形所引起的。其中,四面体孔最难闭合,为所有孔洞锻合所需临界压下率的上限值。锻合区域的给出,为制订锻造工艺提供了理论依据。     

Efficient forging process to improve the closing effect of the inner void on an ultra-large ingot

The internal state of an ingot structure manufactured by the casting process has many loose structures. Generally, loose ingot structures make it difficult to obtain sound material properties. Unsound factors such as voids, porosity and shrinkage in the ingot can be improved by the forging process. The closing of the internal voids depends on the forging process. In this study, numerical analysis was carried out to find the upsetting and cogging processes increasing the internal forging effect of an ultra-large ingot (520 tons). Various parameters such as the ratio of height to diameter of ingot, shifting method, die staggering, and pressing depth were investigated. In addition, verification tests were performed visually using a 1/25 scale model test with pure lead. Results from the numerical analysis and the scaled-down model experiment were compared. The optimal forging process was applied to manufacture a mock-up product. An efficient forging process was suggested to improve the void closing and to achieve the uniform forging effect in the upsetting and cogging process of an ultra-large ingot.     

有限元模拟在后轴支架锻造设计中的应用

针对汽车后轴支架,进行锻造过程三维有限元模拟和工艺、模具设计。采用刚粘塑性有限元模拟技术,得到锻件内部应力场、应变场等参数,分析了这些参数对锻件塑性变形的影响。在此基础上,对此类锻件传统的锻造工艺进行了改进,将预锻工序由开式模锻改进为封闭飞边闭式模锻。同时,模具设计重点从预成形设计考虑,给出了合理的制坯模具设计。在40MN热模锻压力机上进行了试验,试验表明,模拟结果和实际成形过程吻合良好。     

大模数半轴齿轮温精锻成形数值模拟及试验

针对大模数半轴齿轮成形的特点,提出温精锻成形的工艺方案。采用DEFORM-3D有限元分析软件对半轴齿轮的温精锻成形过程进行数值模拟,对影响齿轮成形效果的坯料形状、模具运行速度、坯料加热温度及模具预热温度进行模拟分析;分析坯料在成形过程中的金属流动规律、应变分布、温度场分布,得到了模具载荷-行程曲线;试验验证了该温精锻成形工艺的可行性,为半轴齿轮实际生产工艺的改进提供了参考。     

某大型锻造液压机组合机架整体性分析

某锻造液压机采用双柱斜置式预应力组合机架,为了合理的预紧机架,全面掌握机架的整体性能,给后续的整机设计及优化提供理论参考,主要选取镦粗、扩孔和拔长3种典型工况进行分析.首先应用I-DEAS软件建立三维模型,然后导入MARC软件中进行接触算法计算,每种工况分为中心载荷和可能的最大偏心载荷等情况进行加载计算.三维模型结果显示了在不同工况下立柱与上下梁的开缝大小及开缝长度,计算结果显示扩孔工况不开缝,镦粗和拔长工况分别有0.21和0.12 mm开缝.因此在压机实际运行时,应控制镦粗工况前后偏载的偏心量.压机通过实际的锻造使用证明了前期的分析计算的可靠性.     

缸头模锻成形过程数值模拟

缸头模锻成形是一个复杂的大变形过程,其成形质量影响因素众多,用解析法难以进行精确分析。采用有限元方法对整个成形过程进行模拟,获得了缸头模锻成形过程金属流动变形规律,对成形过程中出现的充不满、折叠等缺陷进行了分析,指出需修改预成形形状的尺寸参数。试验结果表明,采用改进后的预成形形状的尺寸参数能获得比较合格的终锻件。     

压气机静子叶片锻造过程的三维刚粘塑性有限元模拟

利用三维刚粘塑性有限元法对某重型燃机压气机静子叶片的锻造过程进行了数值模拟分析,揭示了叶片锻造变形规律,并以实际锻造工艺试验对其进行了试验验证。锻造工艺试验与数值模拟结果吻合较好,从而验证了数值模拟结果的可靠性。该研究对压气机静子叶片锻造工艺的优化设计具有重要的指导意义。     

轴盘类锻件的差温无模锻造有限元模拟分析

介绍了差温无模锻造技术在成形轴盘类锻件中的应用,分析了始锻温度、摩擦因数、加热区高度、热应变4个不同参数对坯料最终变形结果的影响。分析结果表明,提高始锻温度和摩擦因数有利于使坯料获得局部较大变形,而加热区高度和热应变对坯料最终变形结果无明显影响。     

Integrating physical and numerical simulation techniques to design the hot forging process of stainless steel turbine blades

The paper presents a joint application of finite-element-based numerical simulation and real-material-based physical simulation techniques for design and optimisation of the hot forging operations to manufacture high strength stainless steel turbine blades.2D simulations of the forging steps carried out using a suitably calibrated finite element model are combined with systematic analysis of microstructure evolution during forging experiments, with particular care to formation of the brittle δ-ferrite phase at high temperatures. A correlation is established between microstructure and thermal and mechanical parameters characterising forging operations.On the bases of numerical and experimental results, the actual forging process is re-designed, reducing the total number of forging steps. Industrial trials, conducted with the optimised process parameters, demonstrate the effectiveness of the developed procedure.     

重型燃机叶片锻造过程的三维热力耦合有限元模拟

利用热力耦合刚粘塑性有限元法,对某重型燃机叶片的多工步锻造过程进行了数值模拟研究。通过有限元数值模拟,分析了锻造过程中的金属流线分布,得到了温度场、应力应变场等热力参数的场量分布,从而揭示了叶片锻造的变形机理。实际锻造工艺试验与数值模拟结果吻合较好,从而验证了热力耦合有限元模型的可靠性。该研究对掌握叶片锻造变形规律具有重要意义,为叶片锻造工艺的优化设计提供了参考。     

汽车半轴锻造毛坯二火补温的局部感应加热

阐述述了汽车半轴经一火锻造变形后的毛坯进行补温的局部感应加热设备的设计思路,介绍了汽车半轴锻造二火毛坯补温的局部感应加热设计中功率、频率、加热时间的选取以及有关感应器参数的计算等.     

GH4169合金涡轮盘热模锻中晶粒尺寸演变的数值模拟与分析

针对GH4169合金涡轮盘热模锻中易出现粗晶、混晶等显微组织缺陷,通过热模拟压缩实验和热变形后热处理实验,研究分析了GH4169合金在热变形和后续热处理中的显微组织演变规律,并建立了晶粒尺寸演变模型。实验结果表明:GH4169合金在热变形中的主要显微组织演变机制为动态再结晶,热变形后热处理中的主要显微组织演变机制为晶粒长大和孪晶生成。将晶粒尺寸演变模型与有限元结合,对某GH4169合金涡轮盘热模锻中的晶粒尺寸演变进行了预测分析,预测结果与实际结果一致。     

A new pore closure concept for the manufacturing of heavy rings

In order to avoid pores in heavy rings, a new forming concept is presented. The proposed manufacturing route is based on an analysis regarding the current manufacturing of a ring associated with serious pore closure problems. It is concluded that the present method results in small strains close to the outer surface of the ring. Thus, the likelihood for remaining pores in this region is considered to be high. This apprehension was confirmed both by ultrasonic testing and metallographic analysis. The forming route starts with heavy upsetting of a cylindrical billet followed by piercing in a closed die. The penetrating punch is furnished with an upper flat part that is used for upsetting at the end of the process, forcing the material to fill the cavity between the die and the upper tool. The remaining bottom disk is then sheared off in a separate tool. The new concept starts with a lighter upsetting, resulting in a higher “pan cake” of smaller diameter. This workpiece is then moved to a closed die of the same diameter as that of the material. The diameter of the piercing punch is not changed. Because of the small die diameter, the workpiece is, after piercing, considerably higher than in today’s production. The so-obtained workpiece is placed into a die equal to the original one with the exception of a bottom hole. A new mandrel, with a flat upper part and a lower part meant for shearing off the thin bottom disk, will be inserted to fit the recently generated cylindrical hole. At the beginning of the operation, the bottom disk is cut away as the punch moves through the bottom hole and after that, during the same stroke, the high ring will be heavily upset to its final geometry. During the upsetting the ring is supported by the mandrel. If the ring is too high during upsetting, there is a risk for the material to loose contact with the punch, which might result in instability and a fold. Applying the new concept, the strains close to the envelope surface became approximately 160% larger. The present analysis is carried out with an FE-code Q-form making it possible to trace different material elements of the initial billet throughout the different manufacturing steps. The results are presented in form of hydrostatic pressure as a function of the effective strain. Theoretically determined workpiece shapes, based on the conditions of today’s production are in good agreement with those obtained from full-scale experiments. The present work also includes comparisons with another analysis of similar character, published by the authors. In that work, the manufacturing of two other types of rings were analysed, one with pore closure problems and one without.     

坯料形状对多排链轮半精锻成形过程影响的数值模拟

提出了多排链轮半精锻成形的新工艺,设计了实心和空心坯料半精锻成形模具,运用三维有限元模拟技术,对多排链轮半精锻成形过程进行数值模拟,分别得到了空心和实心两种坯料填充凹模型腔的损坏程度场和等效应力场,并分析了两种坯料成形过程的基本特点。结果表明:相同模拟条件下,空心坯料齿顶处的损坏程度最大,实心坯料芯轴孔处损坏程度最大,最大损坏因子分别为1.52和0.98;空心坯料齿顶处的应力集中最大,实心坯料芯轴孔和齿顶处的应力集中最大,最大等效应力值分别为167和110 MPa,因此采用实心坯料成形多排链轮优于空心坯料。     

Microstructure prediction of two-phase titanium alloy during hot forging using artificial neural networks and FE simulation

The microstructural evolution of titanium alloy under isothermal and non-isothermal hot forging conditions was predicted using artificial neural networks (ANN) and finite element (FE) simulation. In the present work, the change in phase volume fraction, grain size, and the volume fraction of dynamic globularization were modelled considering hot working conditions. Initially, an ANN model was developed for steady-state phase volume fraction. The input parameters were the alloy chemical composition (Al, V, Fe, O, and N) and the holding temperature, and the output parameter was the alpha/beta phase volume fraction at steady state. The non-steady state phase volume fraction under non-isothermal conditions was subsequently modelled on the basis of 4 input parameters such as initial specimen temperature, die (or environment) temperature, steady-state phase volume fraction at die (or environment) temperature, and elapsed time during forging. Resulting ANN models were coupled with the FE simulation (DEFORM-3D) in order to predict the variation of phase volume fraction during isothermal and non-isothermal forging. In addition, a grain size variation and a globularization model were developed for hot forging. To validate the predicted results from the models, Ti-6Al-4V alloy was hot-worked at various conditions and then the resulting microstructures were compared with simulated data. Comparisons between model predictions and experimental data indicated that the ANN model holds promise for microstructure evolution in two phase Ti-6Al-4V alloy.     

Warm forging of aluminium alloys: a new approach for time compression of the forging sequence

A new forging sequence, including a warm forging process, is proposed in order to obtain time compression in the production of forgings in heat treatable aluminium alloys. It offers the advantage of eliminating time consuming and expensive heat treatments. The proposed sequence consists of a solution treatment, followed by water quenching and then by warm forging that produces a fine precipitate structure characterised by high mechanical properties. The optimal warm forging condition was investigated by evaluating the strength and ductility values of the forgings by means of compression testing. The warm forging operation of the AA 6082 aluminium alloy, in the as-solutioned condition, at a temperature of about 240°C, after the natural ageing, provides mechanical properties that are almost coincident with those obtained after conventional forging sequences including an artificial ageing treatment. It was also observed that at such temperature the mechanical properties of the warm-forged parts are not significantly affected by the die speed.     

新型锻造轮毂复合模具设计

设计了实用新型锻造轮毂复合模具,通过改变轮毂毛坯成形面放置方向,将其正面向上放置,防止向下的正向下压力压合成形面变形,同时将冲中心孔、冲窗口、切飞边和扩孔多个工序的任务一次完成,形成复合工作,大大提高了工作效率,也减少了成本。     

Deformation characteristic of the precision forging of a blade with a damper platform using 3D FEM analysis

A blade with a damper platform is one of the most important types of blades being developed in aeronautical engines. However, this type of blade is complicated in shape, consisting of four feature parts with different geometrical shapes. Besides obvious flow of material along the transverse direction, there is material flow along the longitudinal body during its forging process. In addition, the material used is difficult to deform. All these have a significant influence on the precision forging process of the blade. Thus, it is necessary to choose some feature sections along the transverse and longitudinal direction of blade and systematically understand the deformation characteristics of blade forging process. In this paper, by means of 3D rigid–viscoplastic FEM simulation of the precision forging process of the blade, the deformed meshes, distributions of some field variables, including velocity, effective strain, effective strain rate and effective stress are presented for the four chosen feature cross-sections and the velocity fields are obtained for a selected typical longitudinal feature section, and further the deformation characteristics of forging this blade have been revealed. This research may serve as a guide to the optimization design of the relevant processes and dies.     

压力机热锻模用5Cr2NiMoV钢的性能

本文测试了5Cr2NiMoV钢的室温和高温力学性能,探讨了热处理工艺对性能的影响,并与5CrNiMo钢的性能做了对比。结果表明,5Cr2NiMoV钢由于存在二次硬化效应,其回火抗力和高温强度高于5CrNiMo钢。还指出5Cr2NiMo钢存在中温脆性,提高回火温度可以降低中温脆性的危害。     

Finite element simulation of real cavity closure in cast Ti6Al4V alloy during hot isostatic pressing

The healing behavior of shrinkage cavity inside the cast Ti6Al4V alloy during hot isostatic pressing(HIP)was investigated experimentally by interrupted hot isostatic pressing tests.The X-ray micro computed tomography was used to record the morphology changes before and after hot isostatic pressing.The two-dimensional geometry obtained by the microCT scan was used in simulation to study the evolution of the real shrinkage cavity during hot isostatic pressing.Shrinkage cavities,shrinkage porosity and small gas pores can be effectively eliminated under proper HIP conditions.The two-dimensional morphology in the simulation results agrees well with the experimental results.This study reveals that plastic deformation,creep and diffusion are the main mechanisms of cavity closure during hot isostatic pressing.In addition,the simplified elliptical pores with aspect ratios at different positions were used to replace the real pores to further study the factors affecting the position of dimples after HIP by simulation.It is found that the position of the dimples mainly depends on the aspect ratio of the elliptical pore and the distance between the pore surface and the external surface of the geometric model.