Investigation on Zener-Hollomon Parameter in the Warm-Hot Deformation Behavior of CF53

The warm-hot deformation behavior of CF53 steel was studied with hot compression tests at temperature of 1 123 ~1 273 K and strain rate of 0.1~20 s -1 . The activation energy for warm-hot deformation is 274.816 kJ/mol. The influences of Zener-Hollomon parameter, strain and grain size imposing on the flow stress were analyzed in the temperature range of warm-hot forging. Based on the creep theory and mathematic theory of statistics, mathematical models of flow stress were obtained. The results provide a scientific basis for controlling microstructure of forging process through Zener-Hollomon parameter.     

Research on voids deformation welding condition for manufacturing of heavy forgings

Crushing and diffusion welding are two critical healing stages of interior void defects in heavy forgings. The healing result depends on many factors during the forging process, such as stress, temperature, deformation and type of material, while the void diffusion welding condition is still not well known at the present. This paper is concerned with the deformation welding condition of the closed void interface in heavy ingot during the hot forging process. A void crushing experiment is carried out to recognize the microstructure of the closed void interface. According to the healing mechanism at high temperature, a new physical simulation model is setup to study the deformation welding process of the closed void interface based on the theory of atom diffusion and the interface contact mechanics prototype. Compared with the experimental results, the influence of deformation degree, forming temperature and holding time on the welding quality is discussed, and then the deformation welding condition of closed void interface is presented. The proposed condition helps to improve forging technology and product quality.     

轴对称模锻过程的CAS／CAD系统

本文运用上限元法分析了轴对称水平非对称锻件的模锻过程,建立了相应的计算机模拟系统(GAS);为了获得预成形毛胚的理想形状,作者运用计算机进行工序正向模拟之后,又进行了工序反向模拟,经实验验证,计算数据是正确的。     

Numerical analysis of unconventional forging process of hollowed shaft from Ti-6Al-4V alloy

This paper presents theoretical analysis of unconventional forging process of hollowed shaft from Ti-6Al-4V alloy in a three-slide forging press. This method in comparison with other metal forming methods allows for obtaining of hollowed products. The designed process is verified theoretically by means of numerical simulations based on finite element method with assumption of 3D state of strain. The following factors are considered in the analysis: material flow kinematics, strain distribution, temperature distribution and force of process. On the basis of results, it is stated that the application of designed technology allows for obtaining of a product of assumed quality. A comparison is made between material consumption in analyzed process and material consumption in typical metal forming methods, also in used at present technology of shaft manufacturing by machining only. It is stated that the application of forging in the three-slide forging press allows for a considerable decrease of manufacturing costs due to material savings and decrease of labor consumption of operations at finishing.     

Computer Aided Simulation on Precision Cold Forging of Universal Joint Cross

IntroductionThefiwtee1emenmethod(FEM)playsanextrmelyimPortantroleintheanalysesofengineeringproblems.ForalongtimethismethodhasmainlybeenaPPliedinthelinearfieldandshownitsgreatpower.HoweveealOtofnonlinearengineeringPrOblemsWhichcanneitherbesimPlyreducedtolinearonesnorrCPresentedbylinearlyanalogywhichshallchnsethePfacticalconditionsrelativelymuch,havechallengedfiniteelementmethod(FEM).RecentymuchProgresshasbeenmadebothinthemathematicalandmechanicaltheoryandthecomPulertechnologysothatevent…     

Computer Simulation of Thermal-Mechanical Processing

AlterationIntroductionThereisastrongini6ractionamongtemPetalrefield,strCssfield,andmicrosttuctutulaltOrationinm8terialsduringtheirhotworking[l'2].Especiallyduringthecoolingprocess,inwhichtemPeratorechangnsgreatly,intendionsbecomemorecomplexbecauseoftransformationoccurmnce.Duringthehotdeformation,thingswillaPpearsuchas:a.hotdeformation,relatedtostressfieId,changesessentiallytheshaPeofmaterialsandcausesthevariationofthecontactstatebetWeenthedieandsample,resultinginchangeofthethermalboundnyco…     

Forging penetration efficiency of steel H13 stepped shaft radial forging with GFM forging machine

The numerical thermal mechanical simulation of radial forging process of steel H13 stepped shaft with GFM (Gesellschaft fur Fertigungstechnik und Maschinenbau) forging machine was carried out by three-dimensional finite element code DEFORM 3D. According to the effective plastic strain, the mean stress and the mean plastic strain distribution of the radial forging, the forging penetration efficiency (FPE) was studied throughout each operation. The results show that the effective plastic strain in the center of the forging is always greater than zero for the desirable larger axial drawing velocity. The mean stress in the center of the workpiece is proposed to describe hydrostatic pressure in this paper. There is compressive strain layer beneath the surface of the workpiece to be found, while there is tensile strain core in the center of the workpiece. These results could be a valuable reference for designing the similar forging operations.     

Coupled Thermo-Mechanical Modeling of Long Cone-Shaped Forging Based on Rigid Visco-Plastic FEM

Based on synthetically considering the coupled thermo-mechanical relations between temperature and deforming,a numerical simulation of the forging process for the special long cone-shaped workpiece of Al-5.44M-2.15L-0.12Zr alloy at high temperature was conducted by using the rigid visco-plastic finite element method.The relations between the total load and the displacement druing the forging ,and the distributions of stress,strain,temperature and strain rate,which can provide useful information for the process design,are obtained.     

Microstructure Evolution of Different Forging Processes for 12％Cr Steel During Hot Deformation

Five forging experiments were designed and conducted to investigate the effect of process parameters on microstructure evolution during hot deformation for X12CrMoWVNbN10-1-1 steel.The experimental results indicated that average grain size became finer with the increasing number of upsetting and stretching.Especially,the size of stretching three times with upsetting twice had the most remarkable effect on refinement,and the size was only 27.36%of the original one.Moreover,the stress model was integrated into the software and finite element models were established.Simulation results demonstrated that the strain at center point of workpiece was far larger than critical strain value in each process,so that dynamic recrystallization(DRX) occurred in each workpiece,which implied DRX could occur for several times with the increasing number of upsetting and stretching,and uniform finer microstructure would be obtained.However,the results also showed that higher temperature was an unfavorable factor for grain refinement,so the times of heating should be limited for workpiece,and as many forging processes as possible should be finished in once heating.     

模具间隙对液态模锻溢料的影响

通过液态模锻成型压力和温度参数对模具间隙影响的研究,以及模具结构分析,找出了由于模具间隙变化造成溢料的原因,提出了解决方案,对液态模锻模具设计具有一定的参考价值。     

Numerical simulation of multi-pass rolling force and temperature field of plate steel during hot rolling

Rolling force and temperature field are important parameters in the hot rolling process of plate steel. Most researchers use ANSYS/LS-DYNA and MSC.Marc to simulate the hot rolling process, however, software DEFORM-3D is not used widely in this field. Therefore, in this study, the commercially available finite element analysis software DEFORM-3D is used to simulate the distribution of rolling force, stress-effective, strain-effective and temperature field during the hot rolling process of plate steel with the size of 0.220m×2.070m×1.904m. Both the simulated rolling force and temperature of the multi-pass are compared with the measured results. It is shown that the simulated values by the finite element method are approximate to the measured values in the hot rolling of plate steel. So the simulation can provide an important reference and optimization to make rolling process and parameters in steel factory.     

Multi-scale simulation for the forming of a heavy vessel head considering the evolution of defects and microstructure

The head of nuclear pressure vessel is a key component to guarantee the safety of nuclear power plant, so it is necessary to improve its mechanical properties during manufacturing. In the practical production, due to the huge size of the ingots from which the head is manufactured, coarse grains and voids are common defects existing in the material. Furthermore, cracks may appear in the forming process. It is highly demanded that the forming process must be properly designed with suitable parameters to compact the voids, to refine and homogenize the grains and to avoid cracks. Therefore, the research on the evolution of internal voids, grain size and cracks is very important to determine the forming process of huge components. SA508-3 steel is the material to manufacture the head of pressure vessel in the nuclear island. In the previous studies, we have separately built models to evaluate the evolution of internal voids, grain size and cracks during the hot forming process for SA508-3 steel. This study integrates the models for multi-scale simulation of the forging process of the head of nuclear pressure vessel in order to control the quality of the forgings. Through the software development, the models are integrated with a commercial finite element code DEFORM. Then, the extended forging and final forging processes of the head are investigated, and some appropriate deformation parameters are recommended.     

Theoretical Analysis of the Solidification of Aluminum Alloy Billet in Air-Slip DC Mold

Based on the heat transfer analysis of Air-Slip DC mold, a numerical model was presented to study the quantitative relationships between critical solidification layer and casting rate, pouring temperature and mold cooling ability etc. The analytical results show that the Air-Slip mold heat transfer condition plays important roles on choices of a casting rate and the pouring temperature, and that the product of billet diameter and casting rate is a certain constant under a certain condition of the mold.     

Finite element simulation of rod and wire continuous rolling

This paper discusses the application of several techniques involved in the development of the 3D finite element (FE) models of rod and wire continuous rolling process. The FE models are implemented into the FE-program MSC.Marc and used to investigate the thermal and mechanical behavior of billet during the rolling process. All nonlinear equations included in the models are solved by the static and dynamic procedures, respectively. Data transfer technique is proposed to keep the continuity of simulation results. And the computational time of static procedure is significantly reduced by using a rigid pushing body. In all models, the constant time step method and the auto time step method are respectively used to define time step for the solution of equations. Simulation results of the models with different time step methods are compared. And comparison between calculated values and measured ones of the temperature at the surface of billet shows the validity of the FE models.     

Two step forging process of spur gear based on rigid parallel motion

To improve the forging process of spur gear,the metal flow rule is investigated in detail,and a hypothesis of radial rigid-parallel-motive (RPM) flow mode is given. Based on the RPM mode a novel specific gear forging technology is put forward by introduced upend forging process and constrained divided-flow technique. Firstly,finite element method is used to simulate the upend forging pre-forming and RPM finish forging,and equivalent stress field and load-stroke curve are investigated. Secondly,a correspondi...     

批量生产多循环闭式冷锻铝材成形误差机械热偶合有限元分析

在冷成形加工中因为工件和模具中的温度随时间变化而使工件的成形误差也随之变化，以前的成形误差分析仅涉及单个工件加工循环。同时考虑机械效应和热力效应对成形误差的影响，对批量生产多循环闭式冷锻铝材成形过程中工件的成形误差进行了有限元分析，给出了一个包含成形各个阶段所产生的成形误差的误差分析公式。该公式可用于诸如挤压成形等其他成形工艺。这一分析工作为高精密成形误差补偿方法的研究提供了指导。     

增力式多向镦锻装置的研制

在通用压机上生产类似全纤维曲轴一类锻件的先进工艺为多向镦锻法。本文设计的新型增力式多向钮锻装置，在锻造接近结束时，可以增大水平锹粗力，其增力效果超过传统的ＲＲ锻造法及ＴＲ锻造法。     

Simulation of temperature distribution in hot filament chemical vapor deposition diamond films growth on SiC seals

In this study, the temperature and gas velocity distributions in hot filament chemical vapor deposition(HFCVD) diamond film growth on the end surfaces of seals are simulated by the finite volume method. The influence of filament diameter, filament separation and rotational speed of the substrates is considered. Firstly,the simulation model is established by simplifying operating conditions to simulate the temperature and gas velocity distributions. Thereafter, the deposition parameters are optimized as 0.6 mm filament diameter, 18 mm filament separation and 5 r/min rotational speed to get the uniform temperature distribution. Under the influence of the rotational speed, the difference between temperature gradients along the directions perpendicular to the filament and parallel to the filament becomes narrow, it is consistent with the actual condition, and the maximum temperature difference on the substrates decreases to 7.4?C. Furthermore, the effect of the rotational speed on the gas velocity distribution is studied. Finally, diamond films are deposited on the end surfaces of Si C seals with the optimized deposition parameters. The characterizations by scanning electron microscopy(SEM) and Raman spectroscopy exhibit a layer of homogeneous diamond films with fine-faceted crystals and uniform thickness. The results validate the simulation model.     

突缘叉模锻件折叠缺陷分析

通过对缺陷的内部结构进行分析,发现突缘叉锻件法兰底面产生缺陷的主要原因是模锻前制坯工艺不合理,造成模锻时金属回流,产生折叠.提出改进制坯工艺消除锻件的缺陷的方案,经工艺和生产验证,消除了锻件缺陷,提高了锻件质量,取得满意效果,该工艺的成功应用,可为同类型产品的生产提供借鉴.     

电液锤改造的难点与解决办法

换头节能改造是对模锻锤和空气锤进行改造的有效方法，可以取得显著的经济效益和社会效益。主要介绍了电液锤换头改造模锻锤和空气锤过程中遇到的突出问题及解决的办法。