Development of a variable warm forging process chain

In comparison to hot forging, warm forged parts contain advantages e. g. improved surface qualities, lower surface decarburization and smaller geometrical tolerances. The geometrical spectrum of warm forged parts is limited. Cross wedge rolling allows an increase of this geometrical spectrum by cylindrical parts. Additionally, further potential e. g. material saving and short cycle times can be adapted. A method for process lay-out of cross wedge rolling processes is developed and a parameter field for warm cross wedge rolling is identified. This method contains FEAsimulations and experimental analysis with a geometrically downsized cross wedge rolling process. For the experimental trials a new apparatus is developed, which can be integrated in a hydraulic press and allows mounting of several tools in flat wedge configuration. The results of the FEA-simulations and downsized trials are adapted to a cross wedge rolling process for preforming of a steering link integrated into an industrial warm forging process chain.

forming, cross wedge rolling, warm forging, downsizing, process lay-out

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

Warm forged parts have advantages in comparison to conventional hot forged parts: Closer tolerance, 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 have been developed in the Seventh framework programme EU in research project “DeVaPro – Development of a Variable Warm Forging Process Chain”. In the focus is layout of warm preforming operation by cross wedge rolling followed by an intermediate heating and warm final forming in conventional dies. In this paper results of initial experimental tests and results of application of warm cross wedge rolling are shown.

shrinkage compensation, fem

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

Closer tolerances, reduced surface roughness, no scale and reduced decarburization can be realized by warm forging. However, the geometrical spectrum of warm forged parts is limited by flow stress. To overcome this geometrical limitation, innovative warm cross wedge rolling and forging processes are developed in the project presented in this paper. To investigate the effect of lower temperatures on process parameters, e. g. force, die wear and material properties in comparison to hot forming processes, Finite Element Analysis (FEA) and experimental tests using downsized model geometry were performed. In this paper the new warm cross wedge rolling process is explained and results of warm cross wedge rolling trials (e. g. work piece characteristics), FEA simulations of forming forces and material analysis are shown. The results of these analyses allow industrial application of warm cross wedge rolling for the first time.

warm forging, process chain, cross wedge rolling

In the forging industry, cross wedge rolling is a well-established process for production of cylindrical pre-forms with a highly efficient material utilization. To prevent the appearance of material defects during forming, the wedge geometry of the tools is adjusted to the designated pre-form. Today, cross wedge rolling is executed within the hot temperature range. To analyze warm cross wedge rolling, the scientists at IPH - Institut für Integrierte Produktion gemeinnützige GmbH developed a test site for cross wedge rolling experiments.

warm forging, process chain, cross wedge rolling

Cross wedge rolling is used today in the hot temperature range. A test stand for cross wedge rolling tests was developed by the IPH - Institute of Integrated Production to examine this process even with warm component temperatures. The developed test rig for CWR allows practical examination of the influence of different workpiece and tool temperatures, tool geometries and rolling speeds on the forming result. The results of the practical experiments will give insight on customized design of wedge tool geometries, forming velocities as well as tool temperatures for warm and hot cross wedge rolling. Within the project DeVaPro the test rig makes an important contribution to the implementation of a complete custom made technical process chain in warm temperature range.

warm forging, process chain, cross wedge rolling

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

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