Defects like folds can arise using forging for the production of long flat pieces made of aluminium. A special defect is the formation of inner folds. These can be seen in the grain flow. Inner folds have a negative effect on the dynamic properties of the forged part. As a production process, forging can be divided into single-directional and multi-directional forging. The formation of inner folds was observed at the single-directional forging. By using the multi-directional forging, a forming operation working from different directions, the forming can be set variably. Thus the development of folds can be prevented. A newly developed method can help in the selection of the forming process and in determining an appropriate tool geometry. Here especially the area is adapted, where the development of inner folds occur. Therefore a calculation model was developed. It integrates a computer-aided identification of the inner folds. Using this model, a correction of the parametrically constructed forging tool is possible.
multidirectional-forging, long flat pieces, aluminium, fibre orientation
The higher mechanical loads in warm forming processes lead to increased mechanical wear of the dies. Using hard Diamond-like Carbon (DLC)-coatings can reduce this main disadvantage of warm forging. By an adequate doping of DLC with elements the temperature stability of these coating can be increased. Especially in areas with high relative movement the analysed coatings show advantageous behaviour compared to not coated dies.
diamond-like carbon (DLC), warm forming, bulk forming, wear
Forged parts have geometrical fluctuations for example caused by die wear. The investigation of a controlled, movable flash gap by FEA for compensation purpose showed how far the material flow can be varied during the forming operation. A potential to improve forging results is derived.
forging, die design, material flow, FEA, flash land
Hydroforming is often used to conduct forming of thin-walled hollow parts made of tubes. In order to form thick-walled hollow parts made of Aluminum a process has been developed, to form such parts. These parts are in a heated state. The forming has been made by help of an active fluid medium on a hydraulic deep-drawing press. For investigation purpose an example process has been designed for a trial part. This process has been analyzed by FEA and verified by laboratory tests.
hydroforming, forging, tubes, aluminium, FEA
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
A suitable technology for pre-forming of highly loaded forgings is the cross-wedge rolling. With little effort, investigations are now carried out using a new module for cross-wedge-rolling with flat dies. To expand the existing geometric limitation of warm forged steel components, the cross-wedge-rolling at temperatures between 650 °C and 950 °C was investigated. In addition, first studies with aluminum using the new module are described.
warm forging, cross-wedge-rolling
The early detection of defects in forged parts offers economical advantages due to the possibility of sorting them out of the process chain. The aim of the presented research project is the development of a forging process monitoring without sensors. In the process electric current is flowing through the forged part. The quality of the forged parts is measured by the electrical signal. Typical defects of forgings like underfilling and wrong temperature of the billet show characteristic signals and therefore can be detected. These parts are sorted out of the process chain. The user of the forging machine is able to adjust the forging process immediately.
forging, process monitoring
The implementation of process monitoring technologies in manufacturing processes allows significant cost and time savings. An online process monitoring of die cavity filling in warm forging processes could not be realized until now. Important process parameters for example billet volume, billet temperature or lubrication could only be observed after forging. This paper describes the implementation of an online process monitoring system based on electricity.
forging, process monitoring
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
Cross wedge rolling is a method for reshaping cylindrical billets for getting a better mass distribution. Against the backdrop of rising material costs, this method is increasingly becoming the focus of many forging companies - but the high investment costs for tools and equipment prevents the economical benefit of the process. With flat cross wedge tools and corresponding rolling machines tooling costs can be reduced and the process is therefore interesting for small batches. Moreover, studies show that CWR is also applicable in warm temperature range.
warm forging, process chain, cross wedge rolling
In this paper the development of the new production technology hybrid forging is described. Hybrid forging combines forming of bulk and sheet metal-elements including joining. Therefore the classification of hybrid party by material and by the type of the semi-finished product is discussed. In addition, the benefits of hybrid parts are explained. In experimental forging tests with simple geometries a cylindrical bulk part was joined positively with a sheet metal by form closure. A material bond was only partially achieved.
hybrid, forging, sheet metal forming, joining technology, steel, adhesive bond
Multi-directional forging enables flashless preforming for complex workpiece geometries by a cross-section formation and mass distribution in one forging stroke of the press. The process principle is based on a tool with multi-directional acting forming punches. In addition to the vertical forming by a punch a horizontal deformation is performed by horizontally arranged sliders. The drive of the sliders is performed by a redirection of the ram movement using wedges. The multi-directional forging has been studied and developed further over the past decade in a number of research projects. Starting with simple flashless, flat preforms for connecting rods made of steel, the technical feasibility of this method has been demonstrated. In subsequent steps, the principle has been transferred to crankshafts. As part of the Collaborative Research Centre 489, the crankshaft was broken down to a unit cell in order to investigate the fundamental transformation of the bearings and the crank webs. With this knowledge, forging sequences for simplified single and two-cylinder crankshafts were designed (without secondary form elements). Currently the forging sequence for a full two-cylinder crankshaft is designed with secondary design elements. The interaction of the mass distribution by cross-wedge rolling and multi-directional forging is analyzed. The flashless forging of two-cylinder crankshafts with such complicated geometries and corresponding necessary material flow is only possible using a multidirectional preforming. Finally, the applicability of the method to aluminum was investigated in the context of a DFG project – again based on a flat part long preforms. Here particularly clearly the limits of the process could be shown. Various forming directions were combined. With some of these combinations flash developed during the forming operation. Others have shown to be usable for a flashless preforming of complicated geometries.
multidirectional forging, flashless, preforming, cross-wedge rolling, connecting rod, crankshaft, st
To overcome the geometrical limitation of warm forging, in the European research project "DeVaPro - Development of a Variable warm forging Process chain" new rolling and forging processes are developed. The aim of the project is to develop a warm forging process chain by selecting the best suitable hot preforming technology to obtain the desired mass distribution before warm forging. The technology will be adapted to the specific requirements of warm forming. A warm rolling operation and an induction reheating process will be introduced within this project. A steering link and a connecting rod are used as sample parts.
warm forging, process chain, cross wedge rolling
