Paper Abstracts Contained in the Proceedings of · Theory and Technology of Semisolid Metal Molding...
Transcript of Paper Abstracts Contained in the Proceedings of · Theory and Technology of Semisolid Metal Molding...
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CHINA FOUNDRY Vol.6 No.2
Paper Abstracts Contained in the Proceedings of the 10th International Conference on Semi-Solid Processing of Alloys and Composites, S2P2008
1. Semi-Solid Metal Processing - A Process Looking for a Market
Plato Kapranos
Abstract: The birth of Semi-Solid Metal Forming (SSM) or as it has
now come to be widely known, Thixoforming, is a typical case of
development of a technological innovation. Serendipity, stroke of
luck, call it what you may, the beginning of SSM is based on an
almost accidental discovery by a student carrying out a series of
meticulous experiments. On the one hand, some technological failures
have contributed to the lack of success across the board for SSM
technologies. On the other hand, the 'long childhood' of the resulting
technology or the process of moving from 'Innovative Idea to Market'
has been largely the result of difficult and in hindsight sometimes wrong
managerial decisions, occasional personality clashes, patent rights and
at times unavoidable all out business 'warfare'. Of course, hindsight is
beautiful but unfortunately it always comes after the event. However, if
one looks carefully at some of the notable successes of SSM forming
one can discern that the problems were more on the human scale;
people failures rather than technology failures.
This paper aims to bring out some of these points by outlining the
historical development of Thixoforming.
2. Theory and Technology of Semisolid Metal Molding
Frank Czerwinski
Abstract: Fundamentals of semisolid metal molding, including the
particulate feedstock, methods of its generation and features that
make it useful for processing, are outlined. Melting characteristics of
the feedstock under sole influence of heat are considered, covering a
wide range of microstructural and microchemical factors, believed to be
of importance at high temperatures. The generation of the thixotropic
slurry within the injection molding system and its solidification behaviour
are accompanied by detailed features of the molded structures and their
correlation with properties of net-shape components. In addition to
conventional techniques the novel processing concepts including near-
The S2P International Conferences are dedicated to science
and technology of semi-solid processing of metals. Since the
discovery of the specific flow behaviour of metals in semi-
slid state during the seventies of last century, this fascinating
technology has experienced a dynamic development history
which has led to a whole family of new production processes,
new equipment and industrial applications.
In order to fully exploit the technical and economical
potential of these new ideas, it is important to achieve a
better understanding of the microsturcture development,
flow behaviour, improved material and process modelling as
well as process control. The S2P International Conferences
have contributed to achieve this goal by providing a
forum for scientists from various disciplines as well as for
engineers and production specialists to learn from each
other, to share the common knowledge and to develop
a common sense on fundamental topics and industrial
requirements.
The 10th International Conference on Semi-Solid
Processing of Alloys and Composites, S2P2008, organized
by the RWTH Aachen University, Germany and the
University of Liège (Belgium) took place from September
16 to 18, 2008. The conference concentrates on the
advancement of fundamental knowledge and development
of materials and industrial processes for semi-solid
manufacturing of high performance metal components.
145 scholars from 33 countries attended the event, of
which 14 are Chinese continent's delegates from University
of Science and Technology Beijing, Harbin University
of Science and Technology, General Research Institute
Nonferrous Metals, and Huazhong University of Science and
Technology, etc. and 1 delegate from Hong Kong, China.
The conference collected 131 technical papers in total
including poster display 20, among these, 26 is from Chinese
continent's scholars (poster display 14). with the exception
of 5 plenary presentations, the rest 127 were presented at
three technical sessions, respectively. Their topics cover the
following four subjects: Process Development and Industrial
Application (45); Materials Development and Characterization
(49); Numerical Modeling and Simulation (16); Process and
Parts Assessment (17). Dr. Keung Wing Ching from Hong
Kong Foundry Association made his presentation on “Status
Quo of Semi-Solid Technology in China”.
The 11th International Conference on Semi-Solid
Processing of Alloys and Composites will be held in Beijing
of China in 2010. The biennial S2P Conference has its nine
highly successful predecessors held in:
• Sophia-Antipolis, France (1990)
• Cambridge, MA, USA (1992)
• Tokyo, Japan (1994)
• Sheffield, England (1996)
• Denver, CO, USA (1998)
• Torino, Italy (2000)
• Tsukuba, Japan (2002)
• Limassol, Cyprus (2004)
• Busan, Korea (2006)
The following is the paper abstracts contained in the
proceedings of the S2P2008.
Plenary Presentations
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InformationMay 2009
4. Thixoforming of Steel: A State of the Art from an Industrial Point of View
P. Cezard and T. Sourmail
Abstract: Since the first research works in the end of 1980s on the
semi-solid forming of steel, this process has presented a great interest
and a real industrial potential. Several research teams, all over the world,
have shown the feasibility of such a process. Working on the parameters
which have an influence on the process, they pointed out the "technical
locks" which must be overcome to allow industrialization of the process.
A first and perhaps most important difficulty is the reliability of the
forming tools in an industrial production context. Much work has
therefore been devoted to identify ways to increase tools life. A second
important point is the possibility to obtain sound microstructure and
satisfactory mechanical properties. This paper is a state of the art review
on the subject of the thixoforming of steel, restricted to forming of
semi-solid reheated steel. Semi-solid forming process carried out after
partial solidification are therefore not covered. The reader interested in
such processes may refer to the review recently published by Hirt et al. [1].
The present review considers, in turn, the different steps of an
hypothetical production line and their particular challenges, from the raw
material to the final product.
liquidus molding, semisolid extrusion molding as well as the alloy and
composite generation in a semisolid state are described. An update
on commercialization progress is completed by a characterization of
the modern equipment used for process implementation with broad
references to metal die casting and plastics injection molding.
3. On the Modeling of Semisolid Suspensions
Andreas N. Alexandrou
Abstract: Due to the distinct rheologic characteristic of semisolid slurries
the process has well established advantages over competing near-net-
shape manufacturing technologies. Despite the obvious advantages of
the process its adoption by the casting industry, however, has been
slow. This is primarily due to lack of confidence of how these slurries
flow in die cavities. The added cost associated with the specially
prepared slurry has also affected the process commercial success.
Nevertheless these problems attention to the semi-solid metal process
has indeed increased over the years. The main focus of this review is
the modeling of semisolid slurries. The objective here is to present an
overview of relevant aspects of modeling by focusing on the physics
of the slurry and by stressing consistent mathematical and analysis
methods to determine the material constants.
Process Development and Industrial Application 1. Investigations on Thermal Influences for Thixoforging and Thixojoining of Steel Components
René Baadjiu, Frederik Knauf and Gerhard Hirt
Abstract: At the Institute of Metal Forming (IBF) current investigations
within the framework of the Collaborative Research Centre 289 are
mainly concentrated on forming of semi-solid precursor material of the
steel grades X210CrW12 and 100Cr6. One important task is the precise
temperature for the composition of solid and liquid phase fraction in the
preheated billet. Experimental measurements and numerical simulations
show significant heat losses during transport of the billet and after its
insertion into the die. These developing temperature gradients influence
strongly the resulting temperature field in the formed component.
In case of the forming tools the critical increase of the temperature
depending on the tool material is shown. As fundamental research in
the field of thixojoining the temperature development of the inserts is
analysed and demonstrates the feasibility of joining higher and lower
melting materials into the semi-solid matrix.
2. Influence of Processing Route on the Properties of Magnesium Alloys
Hagen Frank, Norbert Hort, Hajo Dieringa and Karl Ulrich Kainer
Abstract: Magnesium alloys had gained an increasing interest in
recent years due to their promising property profile for light weight
constructions. They offer drastic advantages in weight reductions in
automotive industries compared to steel or even aluminium. Therefore
they can be used to decrease the emission of green house gases
as requested by the EU directive for the reduction of CO2 emissions
and moreover due to their recyclability they also help to fulfill the
requirements from the EU directive regarding the end of life of vehicles.
But still there are some limitations with regard to strength, mostly at
elevated temperatures above 130 oC. To overcome these limitations
alloy development as well as process optimization has to be done for
further enhancement of the range of magnesium applications. This paper
will show and discuss the property profiles of the standard magnesium
alloy AZ91D compared to the recently developed, heat resistant
magnesium alloy MR-1153. The alloys have been processed using
normal high pressure die casting (HPDC), New Rheocasting (NRC) and
Thixomolding (R) (TM). As methods of investigation tensile and creep
tests have been applied. The creep properties have been determined
in the temperature range of 135-150 oC and loads of 50-85 MPa. All
these trials have been accompanied by metallographic observations (light
optical metallograph, SEM) and density measurements to investigate
the influence of the processing routes on microstructure and the
porosity of the materials. It will be shown that the differences in the
property profile of the chosen alloys are dependent on their different
chemical compositions as well as on different microstructures that are
obtained by the different processing routes. While in the case of AZ91D,
TM is showing advantages compared to HPDC for room temperature
applications, the NRC in combination with the heat resistant alloy leads
to an improvement of creep rates by two orders of magnitudes.
3. Forming of Biocompatible Materials in the Semi-Solid State
Levente Kertesz and Mathias Liewald
Abstract: Semi-solid processing of materials provides advantages
of both forging and casting. Experiments with high-melting and
biocompatible al loys aiming at a "near-net-shape" production
technology recently have been conducted. Advanced trials showed, that
processing of such materials by means of semi-solid forming deliver
a huge potential for feasible workpiece shapes and drastically reduces
machining time and subsequent surface treatment efforts.
In contrast to semi-solid forming of aluminium alloys at relatively
low temperature levels any processing of high-melting point alloys in
the semi-solid state is much more challenging due to higher forming
temperature. Commonly used tool materials provoke high wear rates
due to wetting, bonding and melting processes which finally result in a
very short tool life time. Thus, more apt materials and composites for
forming tools and dies which can withstand corrosion, wear, tear and
extreme changes in temperatures have to be found. The development
of new design concepts for long-living close-to-production tools based
on such new materials will be a future goal.
4. A Comparison of Deep Drawing and Ironing of Metal Alloy Strip Produced Conventionally and Non- conventionally via Semi Solid Material Processing
Antonio de Pádua Lima Fiho, Márcio Iuji Yamasaki, Leandro Akita Ono,
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Lourenco Nampo and Alcides Pa dilha
Abstract: A semi solid thin strip continuous casting process was used
to obtain 50%wt Pb/50%wtSn strip by single and twin roll processing
at speed of 15 m/min. A 50%wt Pb/50%wtSn plate ingot was also cast
for rolling conventionally into strips of 1.4 mm thickness and 45 mm
width for comparison with those achieved non-conventionally. This
hypoeutectic alloy has a solidification interval and fusion temperature
of approximately 31 oC and 215 oC respectively. The casting alloy
temperature was around 280 oC as measured by a type K immersion
thermocouple prior to pouring into a tundish designed to maintain a
constant melt flow on the cooling slope during semi solid material
production. A nozzle with a weir ensures that the semi solid material
is dragged smoothly by the lower roll, producing strip with minimum
contamination of slag/oxide. The temperatures of the cooling slope and
the lower roll were also monitored using K type thermocouples. The
coiled semi solid strip, which has a thickness of 1.5 mm and 45 mm
width, was rolled conventionally in order to obtain 1.2 mm thick strip.
The coiled thixorolled strip had a thickness of 1.2 mm and achieved
practically the same width as the conventional strips. Blanks of 40 mm
diameter were cut from the strips in a mechanical press, ready for
deep drawing and ironing for mechanical characterization. All the strips
achieved from non-conventional processing had the same mechanical
performance as those achieved conventionally. The limiting drawing
ratio (LDR) achieved was approximately 2.0 for all strips. Microscopy
examination was made in order to observe phase segregation during
processing.
5. Process Window Determination for Thixo- extrusion Processes Using a Steel Alloy
F. Knauf, R. Baadjou and G. Hirt
Abstract: A direct semi-solid bar extrusion process is characterized by
inserting a feed stock in a container and extruding through a forming
die with a punch. Compared to conventional bar extrusion the use of
semi-solid material complicates the process due to the requirement
of solidification of the material. To achieve the solidification of the
semi-solid bar, different basic tool concepts are presented. With a
combination of these concepts experiments were carried out using the
steel alloy X210CrW12 to detect the influence of the most influencing
parameters on press velocity, extrusion channel diameter, length and
geometry. Numerical simulations enable a better understanding of
the process mechanics like temperature development in the billet and
forming die as well as the material flow in the deformation zone.
6. Investigation of Thin Wall Casting Made of Semi-Solid A356 Using Back Extrusion and Die Cast
M. Moradi, M. Nili-Ahmadabadi, B. Herdarian and S. Ashouri
Abstract: Semi-solid forming is a new technology in recent decades
that has a number of advantages over conventional casting routes. As a
result of these advantages, semi-solid processes are less limited in the
part geometry, mainly concerning the wall thickness. According to many
researches on aluminum alloys, the evaluation of flow and die filling
properties of alloys as well as their resulting mechanical properties which
are depended on various process parameters are being investigated
up to now. Semi-solid forming processes contain three main steps:
feedstock manufacturing, reheating and forming. Feedstock quality and
reheating have strong effect on success of forming procedure. In order
to understand and describe forming behavior in the semi-solid state,
two different tests have been studied in the same casting conditions.
In this study, back extrusion and die casting processes were used to
investigate the effect of section size and process on the mold filling. In
the case of back extrusion process a cup shaped specimen and in the
case of die casting process, a step die with different sections size were
used. Microstructures of different sections of specimens were studied
by optical microscopy to depict the effect of different variables on the
quality of products.
7. Basic Study on Thixo-Co-extrusion of Multi-layer Tube with Al/Mg Alloys
Wang Kaikun, Zhang Peng, Du Yanmei, Zeng Pan
Abstract: Thixo-forming is in the forefront of metal processing
technology in the 21st century. The research on thixo-co-extrusion
of multi-layer tube as extension and development of the semi-
solid forming technology is a completely new processing method for
the composite material forming and is of great significance, in which
different semi-solid billets (slurries) are extruded at the same time
to form multi-layer tubes. In this study, different sizes of column-
shaped and ring-shaped billets of Al/Mg alloys were firstly prepared by
using specially designed molds. Then they were reheated by electric-
resistance furnace, microstructures from different heating laws were
investigated. Lastly, FEM simulation on thixo-co-extrusion of double-
layer tube with A356/AZ91 was conducted.
8. Feasibility of Recycling Aluminum Alloy Scrap by Semisolid Extrusion
Sumio Sugiyama and Jun Yanagimoto
Abstract: The feasibility of recycling machining grindings of aluminum
alloys by semisolid process has been investigated. Machining grindings
of A2011 aluminum alloy produced experimentally by lathe machining
were used. The material is put into a metal mold and compressed
up to 90% of the true density at room temperature. The metal mold
with the compressed machining grindings is heated up to a specified
temperature. Afterwards, the metal mold is set into the extrusion
container, and extrusion in hot and semisolid range was carried out.
In this experimental study, extrusion load, internal structure of the
product and mechanical properties (tensile strength, elongation,
hardness) of the product are assessed. It was proven that semisolid
extrusion is about 40% less extrusion load compared with that of hot
extrusion, the shape of the machining grindings remained in the hot
extrusion and the semisolid extrusion products extrusion ratios higher
than 10 have excellent elongation property, which is comparable to the
commercialized product.
9. Thixo-extrusion of 5182 Aluminium Alloy
Plato Kapranos, Toshio Haga, Ermanno Bertoli, Annalisa Pola
Abstract: Extrusion is a well established technology for the production
of complex sections of aluminium alloys. Thixo-extrusion in comparison
to traditional hot-extrusion offers several advantages such as lower
extrusion and friction forces, higher material fluidity, longer tool life etc.
Aluminium alloy 5182 is an important commercial alloy characterized
by high strength and ductility, high corrosion resistance and good
formability; it is commonly used for the production of wrought
automotive components and it is also suitable for semi-solid applications
thanks to its wide solidification range. The aim of this paper is to attempt
the shaping of 5182 Al-Mg alloy through the thixo-extrusion process
using a ceramic tool and evaluating the effect of different routes of
making the feedstock on the semisolid microstructure. Particularly, two
different methods were investigated: Near-solidus casting and Roll-
casting using a cooling slope.
All the samples produced were characterized by metallographic
analysis in order to measure globule size and shape factor, as the main
criteria used for assessing thixo-formability.
10. Forging Process of Wrought Aluminum Alloy with Controlled Solid Fraction by Electromagnetic Stirring
J. W. Bae, S. M. Lee and C. G. Kang
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InformationMay 2009
Abstract: This study demonstrates the indirect rheoforging of wrought
aluminum alloys fabricated by electromagnetic stirring (EMS). EMS
was carried out by varying pouring temperature of theological material
and subsequently the rheo-material was forged into the sample which
consisted of the direct and indirect forging part, by varying the applied
forging pressure. The rheo-material completely filled the die cavity at
the applied forging pressure of 150 MPa. To transfer the densification
pressure to the end of the part, the applied forging pressure of over
170 MPa was necessary. To control liquid segregation, solid and liquid
phases distribute uniformly by deriving the laminar flow. When liquid
segregation occurred significantly during rheoforging, the strength
revealed as low as 268 MPa. Investigating relationship between
microstructural features and mechanical properties of the product,
the rheoforged material through EMS revealed the fine and globular
microstructure. Microstructure with uniform distribution of solid and
liquid phase (no segregation) showed good mechanical property of the
rheoforged material whose tensile strength was 341 for Al6061.
11. Development of the Gas Induced Semi-Solid Metal Process for Aluminum Die Casting Applications
J. Wannasin, S. Junudom, T. Rattanochaikul and M.C Flemings
Abstract: A simple and efficient rheocasting process that has recently
been invented is being developed for aluminum die casting applications.
The process called Gas Induced Semi-Solid (GISS) uti l izes the
combination of local rapid heat extraction and agitation achieved by
the injection of fine gas bubbles through a graphite diffuser to create
semi-solid slurry. In the GISS process, the die casting machine and
the process cycle remain little changed from those of conventional die
casting. The GISS unit creates a low solid fraction of semi-solid slurry
in the ladle during the ladle transfer to the shot sleeve. The semi-solid
slurry is then poured directly into the shot sleeve. This paper presents
the detailed description of the process. The results of the semi-solid die
casting experiments with ADC10 alloy using the GISS process are also
reported and discussed.
12. Strategies for Re-heating Steel Billets for Thixoforming
Bernd-Arno Behrens, Dirk Fischer and Ahmed Rassili
Abstract: Inductive re-heating of billets is the state-of-the-art method
to enable the desired liquid fraction for thixoforming. In laboratory
experiments the temperature might be directly controlled since it is
usually possible to apply thermocouples for temperature measurements.
Due to technical restrictions temperature measurements especially in
the interior of a billet are difficult in industrial heating processes. For this
reason, thixoforming billets are heated without temperature monitoring
by using proven heating functions. Such functions are usually obtained
by trial-and-error or on the basis of FEA simulations. In both cases
exhaustive experimental work is usually necessary. Moreover, FEA
simulations require thermo-physical material data that is difficult to
obtain for industrial relevant heating processes.
In this paper an alternative method of experimentally obtaining
optimized heating functions by using a fuzzy logic controller is
introduced. Under steady-state environmental conditions this method
allows a quick and reproducible re-heating. The main advantages of the
fuzzy logic based approach are that no specific material data is required,
system specific properties such as the efficiency have not be explicitly
determined and that the practical implementation could be realized with
a minimum of experimental work.
13. Recent Developments within Semi-Solid Forming at the Institute for Metal Forming Technology, Stuttgart University
Mathias Liewald and Peter Unseld
Abstract: This paper illustrates several research activities being carried
out within the Center of Competence for Casting and Thixoforging
Stuttgart (CCT 'NOVUS').
A new method for manufacturing Metal Matrix Composites out of
the semi-solid state has been developed at the Institute for Metal
Forming Technology, Universitaet Stuttgart, and applied for patent
pending. Within this new manufacturing method for the production of
fibre and particle reinforced composites now disadvantages of liquid-
phase-techniques can be reduced in combination with decreased
manufacturing costs compared to conventional MMC-production
technologies due to short cycle times and the ability of near-net-shape
forming.
It is obvious that manufacturing process in the fabrication of
metal matrix composite materials will influence in some extent the
performance of these materials. A current research project at the
Institute for Metal Forming Technology (IFU), contributes implementing
specific boundary condition of the manufacturing process to numerical
analysis. Such boundary conditions exert direct influence on product
quality. For manufacturing of metal matrix composites limiting factors
are e.g. temperature, pressure, deformation, etc. Detecting input-
parameter for numerical analysis basic theological parameters, such as
static and dynamic yield points, hysteresis and shear rate jump tests,
detection of the differential structural parameter, evolution of apparent
viscosity of different cast-alloys are topics of current research project at
the Institue for Metal Forming Technology.
For reheating-process of semi-solid alloys new technologies have
been developed and applied for patent pending by the Institute for
Control Engineering of Machine Tools and Manufacturing Units (ISW).
The two main advantages of this technique as compared with other
induction heating techniques are the direct online determination of
liquid-, solid fraction and heating-homogeneity as well as robustness
against variations of prematerial (chemical composition, billet-diameter,
etc.).
14. Flatness Based Control of Inductive Heating of X210CrW12 into the Semi-Solid State
Rainer Gasper, Alexander Schoenbohm, Manfred Enning and Dirk Abel
Abstract: The inductive heating of the feedstock material is a very
important step in the processing of semi-solid metals. On the one hand,
the billet has to be heated as fast as possible to the target temperature.
On the other hand, it must be guaranteed that the outer area does not
begin to melt prematurely. Also, at the end of the heating the billet
should have a uniform temperature distribution in order to obtain good
forming results. A flatness based control will be presented to calculate
the induced power over time trajectory from a desired trajectory for the
temperature in the middle of the billet. The temperature trajectory has
to be chosen so that the billet has the desired temperature behavior.
Experimental results will be shown for the flatness based inductive
heating of X210CrW12 just below the semi-solid state.
15. Numerical Simulation of Induction Heating of Aluminum Alloy Billets
N. Barman, J. Mukherjee and P. Dutta
Abstract: In this work, a numerical model for induction heating
is proposed. The heating process considers only interaction of
electromagnetic effects and heat transfer, and is represented by an
unsteady heat diffusion equation. The numerical simulation of the
process is performed using a finite volume method in which the
induction heating is represented by a volumetric heat source term. The
heat source term is evaluated analytically using principles based on
Faraday's and Biot-Savart laws. The technique is applied to the case of
induction heating of a cylindrical A356 aluminum alloy billet. The model
predicts magnetic flux density and temperature distribution during the
heating process. The effects of process parameters, such as frequency
and current density, on the temperature distribution are also studied.
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CHINA FOUNDRY Vol.6 No.2
The results show that nearly uniform distribution of temperature can be
achieved when the billet is heated slowly with low frequency and low
supply current density.
16. The Influence of Heat Treatments for Laser Welded Semi-Solid Metal Cast A356 Alloy on the Fracture Mode of Tensile Specimens
G. Kunene,G. Govender, L. Ivanchev, R. Knutsen and H. Burger
Abstract: The CSTR rheo-process was used to prepare the aluminium
A356 SSM slurries and thereafter plates (4mm x 80mm x 100 mm) were
cast using a 50-ton Edgewick HPDC machine. Plates were in the as
cast. T4 and T6 heat treatment conditions which had passed radiography
were then butt laser welded. It was found that the pre-weld as cast, T4
and post-weld T4 heat treated specimens fractured in the base metal.
However, the pre-weld T6 heat treated specimens were found to have
fractured in the heat affected zone (HAZ).
17. Semi-solid Casting of High-reactive Wrought Alloys by Means of the Alloy AlLi2.1Mg5.5ScZr (AA1420*)
Matthias Buenck, Fabian Kuethe,Andreas Buehrig-Polaczek, Alexander
Arnold,Bernd Friedrich and Roger Sauermann
Abstract: Semi-solid forming offers new potentials for processing of
high reactive and hot crack susceptible aluminium-lithium wrought
al loys. With the tai lored al loy AA1420* (AlLi2.1Mg5.5 +Sc+Zr) a
promising material for thixoforming with achievable high strength
of up to 500 MPa tensile strength and over 400 MPa yield strength
concomitant with its low density of 2.46 g/cm3 is achievable. Due to high
solid fractions the effect of solidification shrinkage could be sufficiently
decreased with the result of hot-tear-free casting.
Simulation supported a critical to cast automotive tie rod was
exemplarily manufactured via semi-solid-technology with promising
results.
Furthermore with an improved and advanced heat treatment
enhanced mechanical properties, comparable to those of rolled AA
1420, were achieved.
18. Effects of T5 and T6 Heat Treatments Applied to Rheocast A356 Parts for Automotive Applications
M. Rosso, I. Peter and R.Villa
Abstract: The correlation between the evaluation of the mechanical
and of the fatigue behaviour of the rheocast, T5 and T6 heat treated
SSM A356 aluminum alloy with respect to the microstructures of the
component has been investigated. The study has been carried out on
a suspension arm injected in a rheocasting 800-ton plant in Stampal
S.P.A. The new rheocasting is a process that allows obtaining the
alloys in a semisolid state directly from the liquid state, by controlled
cooling of the molten alloys. The resulting microstructures are very fine,
free from defects and homogeneous: these characteristics improve
the mechanical properties of the alloys and specially the response to
cyclic stress, an important issue for a suspension component. After
a preliminary tensile test analysis, axial high frequency fatigue tests
have been carried out at room temperature on specimen cut out from
the suspension arm to determine the Wohler curve and the number
of cycles to failure. The results of this work allow a comparison of the
effects of heat treatment process, T5 or T6, on semi-solid components
for industrial applications in the automotive field. On the basis of these
analyses the correlation between microstructure and mechanical
performances can be established.
19. Semi-solid Extrusion of Complex-shaped Steel Rods Using Ceramic Dies
S. Muenstermann, R. Telle, F. Knauf and G. Hirt
Abstract: Isothermal semi-solid extrusion experiments using steel grade
X210CrW12 as work material were performed on an industrial forging
machine. An improved and tip-scaled tool design was applied, based on
the concept of self-heating ceramic dies tested in previous laboratory-scale
studies and allowing for die preheating temperatures of up to 1,400 ℃.
Steel rods of complex cross sectional geometry were formed at low
extrusion forces. Shape accuracy of as-formed rods is accurate and
metallurgical examination yields no evidence of liquid phase separation.
With a view on the intended industrial implementation construction of
ceramic tools has to be improved in order to avoid rupture of ceramic
parts due to thermo-mechanically induced stresses and to benefit from
the advantages inherent to ceramics in metal forming.
20. Laser Surface Modification of Tool Steel for Semi-Solid Steel Forming
Dermot Brabazon, Sumsun Naher and Patrick Biggs
Abstract: This paper presents an analysis of the effect of CO2 laser
processing parameters on the surface modification and heat treatment
of steels. The CO2 laser and sample movement process parameters
are presented. The controlled operation of these in conjunction with
each other is required to obtain better surface hardness and structure.
H13 tool steel samples were rotated at high speeds to keep exposure
times below 0.3 s. Laser processed samples were analyzed using
EDX spectroscopy, optical microscopy, Vickers and Martens micro-
hardness testing, and X-ray diffraction (XRD). Results show how the
hardness profile through the surface is related to the laser treatment
and resultant microstructures. Increased surface hardness was noted
due to a complete microstructural transformation to an amorphous state
in the glazed samples. The usefulness of such coatings on tool steels,
in conjunction with other thermal barriers, for the forming of semi-solid
steel alloys is presented.
21. Deposition of Oxides as Tool Protection for Large Thixoforming Dies by Using the Pulsed MSIP-PVD Process
Kirsten Bobzin, Nazlim Bagcivan and Philipp Immich
Abstract: Oxide coatings offer great potential for their use in forming
operations in the semi-solid state. Advantages of these types of
coatings are high resistance against abrasive wear, high hot hardness
and low thermal conductivity. Nevertheless deposition by pulsed
Magnetron Sputter Ion Plating-PVD for oxide coatings is quite
challenging: deposition rates are low and insulating layers on the target
surface can cause arcing. On laboratory scale it was possible to deposit
gamma-alumina using PVD in a temperature range, where hot working
steel can be utilized. The next important step in the development
towards an industrial application for larger forming tools is the upscaling
process to larger coating units. In this work the process development of
oxide coatings on an industrial coating unit for large tools was described.
To increase adhesion of oxide top-layer additional bond coats were
applied. Different process parameters like oxygen content, total pressure
and substrate bias were varied, to improve the performance. The
relationship between coating properties and process parameters of the
deposited films were characterized by X-ray-diffraction, Nanoindentation
and Scanning Electron Microscopy (SEM). By using reactive pulsed
PVD-process it was possible to deposit gamma-Al2O3 on large steel
tools for semi-solid melt protection. The developed coatings showed
for thixoforging processes of X210CrW12 an extraordinary stability in
field tests. The lifetime of the permanent moulds was increased by
using PVD thin film coatings as a tool protection.
22. Servomechanical Press: A New Press Concept for Semisolid Forging
Z. Azpilgain, R. Ortubay, A. Blanco and I. Hurtado
Abstract: Semisolid forging process requires special movement of
the ram, until now only achievable with hydraulic presses. The upper
die, placed on the press ram, must move fast during forming of the
component in order to reduce segregation phenomena, and, once the