Research Group Bulk Metal Forming

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Name

Martin Wolfgarten

Group Manager

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work
+49 241 80 97624

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The bulk metal forming group studies, by means of processes as e.g. forging and ring rolling, numerous different research topics such as increasing the geometry limits and process optimization. Furthermore, models representing bulk metal forming processes are developed, which can be used for process design, prediction and improvement of workpiece properties as well as training courses.

 
 

Increasing the Range of Geometries in Open-Die Forging

Production of curved workpiece by superimposed manipulator displacements Copyright: IBF Production of curved workpiece by superimposed manipulator displacements

Open-die forging is an incremental bulk metal forming process, which is mainly used for the production of long and straight workpieces with a simple geometry as round or square. The production of complex geometries by open-die forging usually requires additional manufacturing steps or can only be realized by a high amount of machining. A new manufacturing approach is based on the idea to realize the production of complex workpieces through superimposed manipulator displacements during a forging stroke. Due to the plastic state of stress, already small superimposed stresses are sufficient to control the material flow towards the intended final geometry. This new forging method was successfully realized for the production of curved and twisted workpieces from steel and aluminium using the open-die forging center at IBF. The general approach significantly increases the range of producible geometries in open-die forging.

For further information, please contact Martin Wolfgarten.

  Forging and bending
 
 

STOFF - Fast Calculation Models for Open-Die Forging

Extended informations about the forging process using fast models Copyright: IBF Extended informations about the forging process using fast models

Open-die forging is an incremental forming process, where the initial ingot is forged in up to many hundred forming steps towards the final geometry. The design of new forging process is mainly realized based upon experience or simple geometric correlations. However, by this only a simple geometrical-based process design is possible which does not give any statement about the temperature, the equivalent strain and the grain size. Since FE-simulation of open-die forging is very time consuming and requires a large numerical effort, the IBF developed fast calculation models for open-die forging, which allow the fast calculation of these decisive target values within seconds. Combined with a GUI, a property based design and optimization of open-die forging process can be successfully realized. Furthermore, these models offer a significant potential for teaching purposes as the correlations between forging parameters and resulting workpiece properties can be analyzed in a descriptive way.

For further information, please contact Martin Wolfgarten.

 
STOFF - Fast Forging Models for Process Design
STOFF - Fast forging models for process design
 
 

Online Assisting System for Open-Die Forging

Online-assisting system at IBF forging press Copyright: IBF Online-assisting system at IBF forging press

To ensure excellent and homogeneous mechanical properties, industrial open-die forging requires a smooth and controlled forging sequence. However, during the actual forging process it is not possible to measure decisive workpiece properties as the grain size, equivalent strain and the temperature distribution within the workpiece. Therefore, it is not possible for the press operator to evaluate the impact of small deviations from the planned process sequence on the resulting workpiece properties. Thus, the following process sequence cannot be optimized with respect e.g. to the microstructure. Due to this issue, one main research topic in the field of forging at IBF is the development of an assisting system for open-die forging. By applying fast process models for temperature, strain and grain size, the system allows the operator to evaluate the workpiece properties based upon measured and calculated values. This approach follows the vision to develop an autonomous process control for open-die forging. In this context, the IBF open-die forging center will be used as demonstrator.

For further information, please contact Martin Wolfgarten.

 
 

Void Closure in Open-Die Forging

Comparison of void closure in experiment and FEM Copyright: IBF Comparison of void closure in experiment and FEM

Large ingots for open-die forging are commonly produced in ingot-casting processes. Despite improvements in the casting qualities, casting defects such as voids, gas porosities and pores cannot be completely avoided. One of the goals of open-die forging is therefore, besides realization of the final geometry as well as a homogeneous deformed microstructure, the closure and healing of the voids, whereby the success depends on the process control. Delivery specifications for forging companies are still based on experienced-based safety factors, which guarantee a safe closure and healing of the voids. The goal of this project is therefore, with the help of finite element methods together with a reliable criteria for void closure and healing, to make the process control shorter and more effective.

For further information, please contact Paul Hibbe.

 
 

Open-Die Forging of Hollow Shafts

Open-die forging of an inner-contoured hollow shaft at IBF Copyright: IBF Open-die forging of an inner-contoured hollow shaft at IBF

During the last years, the importance of alternative energy sources as wind energy has risen constantly. A higher energy production by wind power plants cannot only be achieved by setting up additional wind parks, but also by an increase in the performance and by this the size of newly built plants. The electric capacity of up to 6 MW requires larger generators which transform the mechanical to electrical energy. This leads to an increased weight of the whole tower construction. One possible approach to realize lightweight construction is to replace the commonly casted hollow generator shaft by a forged shaft with significantly better mechanical properties. Compared to casted hollow shaft, a weight reduction of 50-60% can be realized. For this purpose, the IBF has successfully developed a forging method performed on the open-die forging center, which allows the open-die forging of hollow shafts with an outer and inner contour with respect to an optimized microstructure to ensure good mechanical properties.

For further information, please contact Martin Wolfgarten.

 
Forging of a Hollow Shaft
Forging of a hollow shaft
 
 

Profile Ring Rolling

Axial roll gap during the axial profiling process Copyright: IBF Axial roll gap during the axial profiling process

Profiling of ring rolled components is an important step for the near net shape production, which leads to material savings as well as time saving regarding the machining. Based on the area of application, all four sides of the cross section can be profiled. Dependent on the type of the profile and the geometry of the ring different challenges during the process occur. Examples for these challenges are the reaching of the desired profile filling and conicity in the cross section.
At the Institute of Metal forming strategies for a stable process, which leads to the desired final geometry are developed and investigated numerically as well as experimentally using the IBF ring rolling mill. Therefore, tool and preform design as well as modifications of the actual process strategy are subject of the research.

For further information, please contact Gideon Schwich.

  Ring rolling of a profiled cross section
 
 

Flexible Radial Ring Rolling for Producing Non-Axially Symmetric Seamless Rings

Flexible radial ring rolling Copyright: IBF Flexible radial ring rolling

Minimizing material and milling costs by near-net shape ring rolling today plays an important economical and environmental role. Industrially feasible ring geometries are exclusively rotationally symmetric, even though applications with varying volume distribution around the circumference exist, e.g. eccentric rings with a nearly linear wall thickness distribution. Depending on size, these parts are produced by milling, closed-die forging or casting processes, while disadvantages in terms of material waste, process flexibility or mechanical properties have to be accepted.
This project aims to further develop the ring rolling process to enable production of near-net shape eccentric ring geometries. Especially for large parts this allows for large material savings without restricting process flexibility or product properties.

For further information, please contact Stefan Günther.

 
Flexible Ring Rolling - Excentrical Rings
Flexible ring rolling - excentrical rings
 
 

Investigation of Influencing Factors on Ring Rolling Processes

Crack on the edge of a ring rolled workpiece Copyright: IBF Crack on the edge of a ring rolled workpiece

Based on the high number of possible shapes and geometries, the process chain of the ring rolling process is often only partly automatized. Therefore, the causes for failures in the final product e.g. pores or cracks are difficult to identify, because neither the extent of the process deviations nor the weight of the respective parameters is known.
For the investigation of the influencing factors of ring rolling processes varying parameters in industrial environment are identified and quantified. Based on the data measured in industry, influences on final product properties are determined. Therefore, by means of damage and microstructure models in numerical simulation, particularly critical and particularly favorable parameter combinations are identified.
Thus, a process layout which considers the different varying parameters is possible and therefore offers the possibility to produce more efficient products while lowering the waste.

For further information, please contact Gideon Schwich.

 
 

Composite Ring Rolling

Joined ring after cutting. Outside: X5CrNiMo17-12-2, inside: 13CrMo4-5 Copyright: IBF Joined ring after cutting. Outside: X5CrNiMo17-12-2, inside: 13CrMo4-5

Composites offer the opportunity to satisfy locally different requirements of parts by combining materials depending on local loads. Contradicting mechanical, thermal or chemical demands can be fulfilled or by combining high-grade and cheap materials, part costs can be reduced.
Likewise for large, seamless rings it is possible to realize tailor-made product properties by producing composite rings, e.g. by using a hard and abrasion-resistant working surface together with a ductile core. The project composite ring rolling aims to identify and describe the main relationships between process parameters and material properties by simulation and experiment to derive suitable rolling strategies and process windows for successful production of composite rings.

For further information, please contact Stefan Günther.