journal homepage: www.elsevier.com/locate/acme Available online at www.sciencedirect.com Press hardening — An innovative and challenging technology R. Neugebauer a , F. Schieck b , S. Polster b , A. Mosel a , A. Rautenstrauch a , J. Scho ¨ nherr b,n , N. Pierschel a a Chemnitz University of Technology, Institute for Machine Tools and Production Processes IWP, Reichenhainer Straße 70, 09126 Chemnitz, Germany b Fraunhofer Institute for Machine Tools and Forming Technology IWU, Reichenhainer Straße 88, 09126 Chemnitz, Germany article info Article history: Received 27 April 2012 Accepted 29 April 2012 Available online 4 May 2012 Keywords: Press hardening Hot sheet metal forming Simulation Tribology Forming tool abstract In view of the growing demand for high-strength, press-hardened sheet metal components and the increasing need for energy and resource efficient process-chains, the optimization of the press hardening process chain is a complex, multi-layered and challenging task. The aim of the present paper is to show the potential for optimization in the press-hardening process chain and to demonstrate initial implementation variants. & 2012 Politechnika Wroclawska. Published by Elsevier Urban & Partner Sp. z.o.o. All rights reserved. 1. Motivation Press-hardened, crash-relevant components such as side-impact and bumper cross members have been used since the mid- 1980s. The trend towards the use of high-strength materials in innovative bodywork concepts that began with this continued ever since (Fig. 1). The number of press-hardened components produced increased from about 3 million units in 1987 to around 124 million in 2010. On this basis the forecast is that the production of high-strength body panels will increase to approxi- mately 350 million components per year by 2015 [2]. In order to meet the requirements of this rapid technological development, reliable and practical production strategies must be developed. A successful example is the forming process of press hardening, which combines the forming and heat treat- ment of the sheet metal component in a single process step. Fig. 2 shows a scheme of the direct process chain for the production of press-hardened structural components. The trimmed sheet metal blank made from heat-treatable manganese–boron steel (22MnB5) is austenitized at 950 1C in a roller hearth furnace. The heating process is followed by the hot forming of the sheet metal on a cooled tool; the so-called press Fig. 1 – Future demand for press-hardened components [2]. 1644-9665/$ - see front matter & 2012 Politechnika Wroclawska. Published by Elsevier Urban & Partner Sp. z.o.o. All rights reserved. http://dx.doi.org/10.1016/j.acme.2012.04.013 n Corresponding author. Tel.: þ49 371 5397 1808; fax: þ49 371 5397 61808. E-mail address: [email protected] (J. Scho ¨ nherr). archives of civil and mechanical engineering12 (2012) 113–118
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Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/acme
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 1 1 3 – 1 1 8
1644-9665/$ - see frohttp://dx.doi.org/10
nCorresponding autE-mail address:
Press hardening — An innovative andchallenging technology
R. Neugebauera, F. Schieckb, S. Polsterb, A. Mosela, A. Rautenstraucha,J. Schonherrb,n, N. Pierschela
aChemnitz University of Technology, Institute for Machine Tools and Production Processes IWP, Reichenhainer Straße 70, 09126 Chemnitz,
GermanybFraunhofer Institute for Machine Tools and Forming Technology IWU, Reichenhainer Straße 88, 09126 Chemnitz, Germany
Fig. 11 – Roughness of drawing edges before and after the
tests with uncoated 22MnB5 and 22MnB5þx-tecs.
coatings. In this case the tool surface is protected using
mechanically resistant coatings and, as other studies have
shown, an improvement in component quality is also achieved.
The coefficients of friction are almost completely unaf-
fected by the tool coating on both sheet variants (uncoated
and x-tecs-coated; Fig. 12). However, a change of the initial
sheet material can have a significant influence on the
process. The use of an x-tecs coated sheet in place of an
uncoated sheet reduces friction by about a half, whereby the
formation of cracks due to excessive thinning during hot
forming can be prevented.
4. Evaluation of the energy and resourceefficiency of process chains
One milestone on the path to an energy and resource efficient
production process chains is the use of holistic balancing
methods, evaluation tools and planning software. In the
future, such tools will enable engineers, for instance in car
body manufacturing, to balance and evaluate process chains
in terms of energy and resource efficiency, to choose energy-
sensitive influencing factors and to detect technological
improvement approaches. Therefore, a method was developed
whereby energy-sensitive, technological factors and the
energy and material flows of a process are incorporated within
a ‘‘process energy balance’’ for accounting and evaluation. This
procedure for energy and material balancing, shortened to
PEMB, consists of four steps: analysis, modeling, balancing and
evaluation. PEMB is based on the SADT model (Structured
Analysis and Design Technique), which is connected with a
techno-economic classification of production process elements
and generates a comprehensive process model. This process
model enables, on the one hand the visualization of energy and
material flows (step 1), and on the other hand the systematic
modeling of all the process elements involved (step 2), such as
raw materials, auxiliary materials, machinery and equipment or
electrical energy (Fig. 13).
Based on the individual process models, process-specific
process energy balances are created, which are then sum-
marized as a process chain energy balance (step 3). These
process and process-chain balances can, for example, be
Fig. 13 – Energy and material flow during press hardening
(example).
a r c h i v e s o f c i v i l a n d m e c h a n i c a l e n g i n e e r i n g 1 2 ( 2 0 1 2 ) 1 1 3 – 1 1 8118
used to calculate energy and material consumption, deter-
mine the process efficiency of the processes or analyze the
influence of process parameters such as process temperature,
sheet thickness, tool geometry and tensile strength on energy
and resource efficiency. The last step of the method (step 4)
analyses and evaluates the process and process chain bal-
ances created, whereby improvement approaches can be
identified and quantified. This basis can provide guidance
for improvement activities as well as setting energy- and
resource-sensitive process parameters. This provides engi-
neers such as planners for bodywork manufacturing with
a method that allows the energy and material flows of
process chains to be identified and evaluated. In addition,
energy-sensitive influencing factors can be selected, and
thus energy and resource efficient process chains can be
designed [1].
5. Summary and outlook
In order to meet the large future demand for hot-formed
components and to cope with the increasing demands in terms
of energy and resource efficiency, a wide variety of technological
challenges must be overcome. The basis for this is formed
primarily through the use of thermo-mechanically coupled,
finite element simulation, the implementation of defined tribo-
logical application conditions and the quantitative determination
of the energy and material consumptions of processes. Funda-
mental studies with regard to material and process parameters
as well as the development of appropriate tooling concepts
have provided the first steps towards overcoming the technical
challenges of manufacturing. This also provides the basis for
addressing current complex issues such as the mechanical
trimming of press-hardened components or of graded press-
hardened components.
Acknowledgements
The Cluster of Excellence ‘‘Energy-Efficient Product and Pro-
cess Innovations in Production Engineering’’ (eniPROD) is
funded by the European Union (European Regional Develop-
ment Fund) and the Free State of Saxony.
r e f e r e n c e s
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