Recent research dealt with the basic forgeability of aluminium-matrix composites produced under laboratory conditions. These research projects concentrated on metallurgy and, by deriving flow curves, on formability. In contrast to laboratory conditions, the industrial use requires large batches of raw materials and takes place under real conditions. Those conditions have not yet been analysed. This paper describes the combination of mechanical advantages of aluminium-matrix composites and a flashless forging process. The advantages can be outlined as higher part strength, compared to conventional forging parts with the same weight. Newly derived flow curves demonstrate formability and were used to evaluate basic forging parameters. The first forging trials in a conventional forging process using a high forging rate resulted in broken parts and therefore required a reduced deformation rate. The matrix slug material provides a higher deformation rate but has to be reduced, due to the use of MMCs. Using a conventional forging press (e.g. screw press) causes material failures likes cracks, because forging Al-MMCs requires a reduced forming speed of 20 mm/s. Reducing the forming speed, hydraulic presses are recommended. FE-analysis of the newly developed flashless forging process is described and depicts the basic forming operations (spreading, elongating and climbing) of the material in the forging die. Altogether a new strategy for a flashless forging process layout with Al-MMC is shown.
forging, flashless, aluminium, matrix, composite, characterization, upsetting, FEA, simulation, tool
In automotive industry, parts made of aluminum alloys are used with increasing frequency. During forging operations for the production of aluminum long flat pieces, defects like folds can appear. Especially internal folds are of interest, which are only evident in the fiber orientation and have a negative effect on the dynamic mechanical properties of the forged part. In forging, the forming operation can be realized either from one direction (uni-directional) or from several directions (multi-directional). The boundary conditions for multi-directional forging are described in this article. For a given tool geometry, multi-directional forging permits the realization of fold-free forgings, which has been shown to be not possible with uni-directional operations. A newly developed method based on Finite-Elements-Analysis (FEA) simulation helps with the design of the forming process and the determination of the appropriate tool geometry. A new algorithm integrates the computer-aided identification of internal folds. For a given process and tool geometry, the area with internal folds is adjusted, until the simulation shows no fold formation. It is shown, that by using this model, a dependable assessment and correction of forging tools and forming process and thus the realization of a fold-free forming are possible.
multi-directional forging, aluminum forging, internal folds, finite-elements-analysis, algorithm, to
This paper describes the development of a warm cross wedge rolling process with one area reduction. The paper also includes results of finite element analysis (FEA), experimental trials with a downsized work piece and the adaption to the industrial work piece in original size. In the FEA simulations tools with serrations on the side have been used. The downsizing method is explained and the difference between FEA, downsized and originally sized work piece with the focus on forming forces, temperature distribution and defects are presented.
warm forging, cross wedge rolliing
To produce preforms for complex long flat parts with an unsteady mass distribution along the longitudinal axis rolling processes, like cross wedge rolling, can be used. Tools for cross wedge rolling processes can be constructed as roller or flat, both with wedges. In the collaborative research project "SFB 489 - Process chain for the production of precision forged high performance parts" the subproject "Innovative machine and tool technology for precision forging" deals with the development of a flashless forging process for a two cylinder crankshaft with pin and flange. This process is developed by IPH - Institut für Integrierte Produktion Hannover. The first preform of the developed forging sequence is produced by a cross wedge rolling process on the basis of flat with wedges. To consider the mass distribution of the two cylinder crankshaft in the preform for a rolling process four mass concentrations for the crank arms and mass concentrations for pin and flange are needed.
crankshaft, cross wedge rolling (CWR), forging sequence, preform, rolling process
Lightweight design of cars is one way to reduce fuel consumption and increase the range of cars. This is an important factor to attain the EU limit values for CO2 emissions for vehicles and thus to avoid penalties for exceeding these limits as of the year 2012. The growing number of uses for high-strength steels or lightweight structures are adequate means to reduce weight. At IPH - Institut für Integrierte Produktion Hannover gGmbH a method to produce hollow profiles made of aluminum was developed. This method, called hydroforging, combines flashless forging and tube hydroforming. It allows the production of thick-walled hollow aluminum profiles with undercuts without the need for complex tool kinematics. The forging is supported by an active medium. A tool concept has been developed using the drives of a hydraulic press with die cushion. With this tool, various part geometries shall be produced and analyzed. To produce the tools' interior pressure and the forming pressure, liquid tin as an incompressible active medium is used. The forming is initiated by upsetting the aluminum profiles and supported by the active medium, so that the profile is pushed against the cavity of the dies. The process was designed based on simulations and will be verified by practical experiments. This paper describes the development of the forging process with an active medium.
hydroforming, forging, tubes, aluminium, FEA
Sheet metal parts often have to be connected by fasteners. Fasteners like bolts are mostly welded individually after the forming process and outside the working tool. This spatial separation of production steps requires complex handling operations and has negative impact upon the positioning accuracy of the fasteners. Every executable manufacturing step inside the sheet metal working tool shortens the process chain significantly. Furthermore, using a combined process the precision of position and orientation of fasteners improves. The challenges of integrating the welding process into the sheet metal working tool are handling the emissions and associated pollutions of the tool as well as creating a reliable monitoring-system for the welding-process. Within the scope of a research project, a reliable technology for the integration of condenser discharge stud welding with tip ignition was developed and tested. It complements existing solutions for integrated resistance welding processes.
sheet metal, capacitor discharge arc stud welding, cd arc stud welding, tip ignition, follow-on tool
Many forged parts include piercings e.g. as bearings. The web of the forged pieces has to be pierced in an additional manufacturing step. By integrating this so far separately performed operation into the final forging step the process chain can be shortened. However, up to date there is no information available on how the process parameters influence quality relevant factors. Therefore, a combined forging-/piercing process is designed and performed. The results of previous research projects showed that the variation of the inserted mass and the forging temperature have a distinct effect on the dimensional and form accuracy of the work pieces. In this project different punch and work piece geometries and the influence of a different forming sequence on tool stress and the material flow was investigated. The punch and work piece geometry show no effect on form accuracy of the piercing while an inappropriate forming sequence leads to failure of the tool.
forging, flashless, precision, piercing
Many forged parts include piercings e.g. as bearings. The web of the forged pieces has to be pierced in an additional manufacturing step. By integrating this so far separately performed operation into the final forging step the process chain can be shortened. However, up to date there is no information available on how the process parameters influence quality relevant factors. Therefore, a combined forging-/piercing process is designed and performed. The results of previous research projects showed that the variation of the inserted mass and the forging temperature have a distinct effect on the dimensional and form accuracy of the work pieces. In this project different punch and work piece geometries and the influence of a different forming sequence on tool stress and the material flow was investigated. The punch and work piece geometry show no effect on form accuracy of the piercing while an inappropriate forming sequence leads to failure of the tool.
forging, flashless, precision, piercing
Saving resources becomes more and more important. Therefore the forging industry tries to develop processes with less flash than the conventional techniques or to avoid flash completely. Currently only simple parts like gears can be forged without flash. In a research project flashless forging processes for crankshafts were developed. In this paper the evolution of the flashless forging process and the process steps will be described. The collaboration research project "process chain for the production of precision forged high performance parts" has been conducted in the last few years at IPH and was funded by the German Research Foundation (DFG).
precision forging, flashless, crankshaft
Large-scale products (XXL-products), such as bearing rings for wind turbines, pose special challenges to the production technology. For example, the continuous growth of product dimensions puts challenges on forming technologies as they reach their technical limits. Scaling effects, that occur when scaling up, can include physical limits for a further upscaling. These effects have only been studied for small scale production processes so far. The consideration of such effects in the large scale production offers the opportunity to exploit the potential of metal forming processes and improve the calculation forecasts.
xxl-products, forging, flowproperties, scaling factor, scaling effect, ring compression test
To realise integration, a new modular tool concept was developed in a research project. However, negative process effects like weld splatters occur. As a counteraction the control of process parameters, an extraction system and mechanical solutions were developed. Focus of this research project was to demonstrate process stability and reachable numbers of strokes. Welding tests with a developed joining step within a progressive die showed good joining results and high process stability. Welded studs were examined by reverse bending experiments and achieved maximum values pointing to the sheet material were used. Disturbances were introduced reliably detected by process monitoring of the voltage and current curve progression as well as the bolt movement. The analysis of the measurements showed the robustness of the automated welding process. Welding emissions were efficiently removed by suction from the shielded welding area in the tool without compromising on joining qualities.
sheet metal, capacitor discharge arc stud welding, cd arc stud welding, tip ignition, follow-on tool
Warm forged parts have advantages in comparison to conventional hot forged parts: Closer tolerances, reduced surface roughness, no scale and reduced decarburization. However, the geometrical spectrum of warm forged parts is restricted by high flow stress. To overcome this geometrical limitation new rolling and forging processes are developed in the European research project "DeVaPro - Development of a Variable Warm Forging Process Chain". The focus is on the layout of a warm preforming operation by cross wedge rolling followed by an intermediate heating and warm final forming in conventional dies. To get an idea of the effect of lower temperatures on process parameters, e.g. force, die wear and microstructure as opposed to hot forging processes, FE-simulations and experimental tests with a model are performed. In this paper a new warm cross wedge rolling process is introduced and results of experimental tests e. g. mechanical characteristics and microstructure are shown.
warm forging, process chain, cross wedge rolling
