Handbookof AluminumVolume 7Physical Metallurgy and
Processesedited byGeorge E. Tot tenG. E. Totten & Associates,
Inc.Seattle, Washington, U.S.AD. Scott MacKenzieHoughton
International IncorporatedValley Forge, Pennsylvania, U.S.A.MARCEL
DEKKER, INC. NEW YORK BASEL
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PrefaceAlthough there are a limited number of reference books
on aluminum metallurgy,there is a signicant and continuing need for
a text that also addresses the physicalmetallurgy of aluminum and
its alloys and the processing of those alloys that will beof
long-term value to metallurgical engineers and designers. In
addition, a number ofvitally important technologies are often
covered in a cursory manner or not at all,such as quenching,
property prediction, residual stresses (sources and
measurement),heat treating, superplastic forming, chemical milling,
and surface engineering.We have enlisted the top researchers in the
world to write in their areas of spe-cialty and discuss critically
important subjects pertaining to aluminum physicalmetallurgy and
thermal processing of aluminum alloys. The result is an
outstandingand unique text that will be an invaluable reference in
the eld of aluminum physicalmetallurgy and processing.This is the
rst of two volumes on aluminum metallurgy and some of the
topicsinclude: Pure aluminum and its properties. An extensive
discussion of the physical metallurgy of aluminum, includingeffect
of alloying elements, recrystallization and grain growth,
hardening,annealing, and aging. Sources and measurement of residual
stress and distortion. An overview of aluminum rolling, including
hot rolling, cold rolling, foilproduction, basic rolling
mechanisms, and control of thickness and shape. A detailed
discussion of extrusion design. A thorough overview of aluminum
welding metallurgy and practice.iii
Casting, including design, modeling, foundry practices, and a
subject oftennot covered in aluminum metallurgy bookscasting in a
microgravityenvironment. Molten metal processing and the use of the
Stepanov continuous castingmethod. Forging design and foundry
practice. Sheet forming. An overview of equipment requirements and
a detailed discussion of heattreating practices. An in-depth
discussion of aluminum quenching. An overview of machining
metallurgy and practices, including materialproperty dependence,
machining performance process parameters, anddesign. An extensive,
detailed, and well-referenced overview of superplasticforming. A
thorough discussion of aluminum chemical milling, including
pre-maskcleaning, maskant applications, and scribing, etching, and
demasking. Powder metallurgy including: applications, powder
production, part pro-duction technologies, and other processes.The
preparation of this book was a tremendous task and we are
deeplyindebted to all our contributors. We would like to express
special thanks to AliceTotten and Patricia MacKenzie for their
assistance and patience throughout the pro-cess of putting this
book together. We would also like to acknowledge The
BoeingCorporation and Houghton International for their continued
support.George E. TottenD. Scott MacKenzieiv Preface
ContentsPreface iiiContributors ixPart One ALUMINUM PHYSICAL
METALLURGYAND ANALYTICAL TECHNIQUES1. Introduction to Aluminum
1Alexey Sverdlin2. Properties of Pure Aluminum 33Alexey Sverdlin3.
Physical Metallurgy and the Effect of Alloying Additionsin Aluminum
Alloys 81Murat Tiryakiogglu and James T. Staley4. Recrystallization
and Grain Growth 211Weimin Mao5. Hardening, Annealing, and Aging
259Laurens Katgerman and D. Eskin6. Residual Stress and Distortion
305Shuvra Das and Umesh Chandrav
Part Two PROCESSING OF ALUMINUM7. Rolling of Aluminum 351Kai F.
Karhausen and Antti S. Korhonen8. Extrusion 385Sigurd Stren and Per
Thomas Moe9. Aluminum Welding 481Carl E. Cross, David L. Olson, and
Stephen Liu10. Casting Design 533Henry W. Stoll11. Modeling of the
Filling, Solidication, and Cooling ofShaped Aluminum Castings
573John T. Berry and Jeffrey R. Shenefelt12. Castings 591Rafael
Colas, Eulogio Velasco, and Salvador Valtierra13. Molten Metal
Processing 643Riyotatsu Otsuka14. Shaping by Pulling from the Melt
695Stanislav Prochorovich Nikanorov and Vsevolod Vladimirovich
Peller15. Low-g Crystallization for High-Tech Castings 737Hans M.
Tensi16. Designing for Aluminum Forging 775Howard A. Kuhn17.
Forging 809Kichitaro Shinozaki and Kazuho Miyamoto18. Sheet Forming
of Aluminum Alloys 837William J. Thomas, Taylan Altan, and Serhat
Kaya19. Heat Treating Processes and Equipment 881Robert Howard,
Neils Bogh, and D. Scott MacKenzie20. Quenching 971George E.
Totten, Charles E. Bates, and Glenn M. Webster21. Machining 1063I.
S. Jawahir and A. K. Balajivi Contents
22. Superplastic Forming 1105Norman Ridley23. Aluminum Chemical
Milling 1159Bruce M. Grifn24. Powder Metallurgy 1251Joseph W.
NewkirkAppendixes1. Water Quenching Data: 7075T73 Aluminum Bar
Probes 12832. Type I Polymer Quench Data: 2024T851 Aluminum Sheet
Probes 12853. Type I Polymer Quench Data: 7075T73 Aluminum Sheet
Probes 12864. Type I Polymer Quenchant Data: 7075T73 Aluminum Bar
Probes 1287Index 1289Contents vii
ContributorsTaylan Altan, Ph.D. Ohio State University,
Columbus, Ohio, U.S.A.A. K. Balaji, Ph.D. The University of Utah,
Salt Lake City, Utah, U.S.A.Charles E. Bates, Ph.D., F.A.S.M. The
University of Alabama at Birmingham,Birmingham, Alabama, U.S.A.John
T. Berry, Ph.D. Mississippi State University, Mississippi State,
Mississippi,U.S.A.Niels Bogh, B.Sc. International Thermal Systems,
Puyallup, Washington, U.S.A.Umesh Chandra, Ph.D. Modern
Computational Technologies, Inc., Cincinnati,Ohio, U.S.A.Rafael
Colas, Ph.D. Universidad Autonoma de Nuevo Leon, San Nicolas de
losGarza, MexicoCarl E. Cross, Ph.D. The University of Montana,
Butte, Montana, U.S.A.Shuvra Das, Ph.D. University of Detroit
Mercy, Detroit, Michigan, U.S.A.D. Eskin, Ph.D. Netherlands
Institute for Metals Research, Delft, The Netherlandsix
Bruce M. Griffin, B.S.M.E.T., M.S.M.E. The Boeing Company, St.
Louis,Missouri, U.S.A.Robert Howard, B.Sc. Consolidated Engineering
Company, Kennesaw, Georgia,U.S.A.I. S. Jawahir, Ph.D. University of
Kentucky, Lexington, Kentucky, U.S.A.Kai F. Karhausen, Ph.D. VAW
Aluminium AG, Bonn, GermanyLaurens Katgerman, Ph.D. Netherlands
Institute for Metals Research, Delft, TheNetherlandsSerhat Kaya,
M.Sc. Ohio State University, Columbus, Ohio, U.S.A.Antti S.
Korhonen, D.Tech. Helsinki University of Technology, Espoo,
FinlandHoward A. Kuhn, Ph.D. Scienda Building Sciences, Orangeburg,
South Carolina,U.S.A.Stephen Liu, Ph.D. Colorado School of Mines,
Golden, Colorado, U.S.A.D. Scott MacKenzie, Ph.D. Houghton
International Incorporated, Valley Forge,Pennsylvania, U.S.A.Weimin
Mao, Ph.D. University of Science and Technology Beijing, Beijing,
ChinaKazuho Miyamoto, Dr.Eng. Miyamoto Industry Co. Ltd., Tokyo,
JapanPer Thomas Moe, M.Sc.-Eng. Norwegian University of Science and
Technology,Trondheim, NorwayJoseph W. Newkirk, Ph.D. University of
MissouriRolla, Rolla, Missouri, U.S.A.Stanislav Prochorovich
Nikanorov, Dr.Sc. A.F. Ioffe Physical Technical Institute ofRussian
Academy of Sciences, Saint Petersburg, RussiaDavid L. Olson, Ph.D.
Colorado School of Mines, Golden, Colorado, U.S.A.Ryotatsu Otsuka,
Dr.Eng. Showa Aluminum Corporation, Osaka, JapanVsevolod
Vladimirovich Peller A.F. Ioffe Physical Technical Institute of
RussianAcademy of Sciences, Saint Petersburg, RussiaNorman Ridley,
B.Sc., Ph.D., D.Sc., C.Eng., F.I.M. University of
Manchester,Manchester, Englandx Contributors
Jeffrey R. Shenefelt, Ph.D. Mississippi State University,
Mississippi State,Mississippi, U.S.A.Kichitaro Shinozaki National
Institute of Advanced Industrial Science andTechnology, Tsukuba,
JapanJames T. Staley, Ph.D.* Alcoa Technical Center, Alcoa Center,
Pennsylvania,U.S.A.Henry W. Stoll, Ph.D. Northwestern University,
Evanston, Illinois, U.S.A.Sigurd Stren, Ph.D. Norwegian University
of Science and Technology, Trondheim,NorwayAlexey Sverdlin, Ph.D.
Bradley University, Peoria, Illinois, U.S.A.Hans M. Tensi, Ph.D.
Technical University of Munich, Munich, GermanyWilliam J. Thomas,
Ph.D. General Motors, Troy, Michigan, U.S.A.Murat Tiryakioglu,
Ph.D. Robert Morris University, Moon Township,Pennsylvania,
U.S.A.George E. Totten, Ph.D., F.A.S.M. G.E. Totten &
Associates, Inc., Seattle,Washington, U.S.A.Salvador Valtierra,
Ph.D. Nemak Corporation, Monterrey, MexicoEulogio Velasco, Ph.D.
Nemak Corporation, Monterrey, MexicoGlenn M. Webster, A.A.S. G.E.
Totten & Associates, Inc., Seattle,
Washington,U.S.A.*RetiredContributors xi
E B( D C = , A , C 2 K$ = A$ , 44-+ 4 2 C J D = , 1 & 44
!4
8ExtrusionSIGURD STVREN and PER THOMAS MOENorwegian University
of Science and Technology, Trondheim, Norway1 INTRODUCTIONThis
chapter is devoted to extrusion of aluminum alloys and divided into
three mainsections. Section 2 covers the basic parameters of
extrusion needed for designing analuminum section and a die, for
understanding the processing steps, and foroptimizing productivity,
cost and product quality. A specic section shape is usedto
illustrate the interaction between these parameters. Section 3 is
focused onthe commercial applications aspects of extruded sections,
life cycle aspects, alloyselection and section design guidelines.
Section 4 covers the extrusion process insome detail, focusing on
the basics of quantitative modeling of metal ow in thecontainer and
through the die. In the nal section, some of the outstanding
researchchallenges in the theory of extrusion of thin walled
aluminum sections are discussed:(1) 3D-modeling of thin-walled
extrusion; (2) the bearing channel friction in inter-action with
die deections and section surface formation; (3) stability of
ow;and (4) limits of extrudability.The intention is that the
chapter should give the reader an overview of thepractical aspects
of extrusion as well as an understanding of the present state ofthe
theoretical work and some challenges in this branch of metal
forming scienceand technology. However, the study of extrusion as a
process is both relativelycomplex and multidiciplinary, and this
chapter can hardly give the answer to allproblems that may be
encountered. Thus, before making detailed section designand alloy
decisions, the reader is advised to contact an extrusion plant.
Even thoughtheoretical and experimental work has managed to explain
a number of relevantphenomena, the quality of an extruded prole and
naturally also of a complete prod-uct based on extrusions is still
mainly dependent on the experience of personnel close385
to or at the extrusion plant. One may also confer with more
general works onextrusion [1,2].2 BASIC PARAMETERS OF EXTRUSION2.1
The ProcessThe most common method for producing aluminum proles is
that of directextrusion (Fig. 1). Here, the ram is moving into the
container at one end, and pushesthe billet through the opening of
the die at the other end. The temperature of thedeforming aluminum
alloy is in the range of 450^600C during the process cycle.In
contrast to the extrusion of steel, aluminum extrusion is taking
place in absenceof any lubrication of the die. Hence, the material
sticks to the container and thedie, giving a highly inhomogeneous
ow with large degree of visco-plastic shear ow(See Sec. 4). The
material far a way from the wall is owing easier than that closer
toit, with the surface of the billet remaining in the container.
The billet and the con-tainer are normally circular cylindrical,
but can in special cases be rectangular withrounded corners.A
special feature in extrusion of aluminum alloys is the production
of hollowsections (Fig. 2). In this case the metal ows into the
opening between the dieand the mandrel. The mandrel is kept in
position by bridges. The billet materialis forced, by the movement
of the ram, into the portholes in the bridge die, calledthe feeder
ports. Under the bridges, adjoining metal streams meet and
areforgewelded together in the weld chamber, before owing through
the bearingchannel, i.e. the opening between the die and the
mandrel.Besides direct extrusion, two other special extrusion
methods are used, indirectextrusion, and continuous extrusion, the
Conform method [3]. In indirect extrusion(Fig. 3) the die is pushed
into the container, where as the extrudate is owing inopposite
direction through the hollow stem. In the continuous extrusion
(Fig. 4)a continuous feedstock is fed into a groove in a rotating
wheel. Pressure is builtFigure 1 Direct extrusion of an open
section.386 Stpren and Moe
up by friction between the groove walls and the feedstock in
the gap between thewheel groove, the feeder plate and the abutment.
The metal is then forced to thedie opening in a continuous ow. Both
open and hollow sections can be produced.Extrusion in rectangular
containers, indirect extrusion and continuousextrusion are used for
special products in limited quantities. Therefore, in the restof
this chapter the direct extrusion of open and hollow sections are
dealt with.The main parameters of the billet, the container and the
extruded section are(Fig. 1):. Diameter of the container: Dc m.
Cross section area of the container: Acontainer Ac p4D2c m2Figure 2
Direct extrusion of a hollow section.Figure 3 Indirect
extrusion.Extrusion 387
. Billet weight: Wb r p4D2bLb kg. Billet diameter Db m. Billet
length Lb m. Density of aluminum: r 2700 kg=m3. The circumscribed
diameter of the section: d m. Section thickness: t m. Cross
sectional area of the section: Asection As m2. Weight of section
per meter length: ws Asr kg=m. Reduction ratio: R AcAsThe most
common values for the diameter of the container are 0.178 m
and0.208 m. The billet diameter is usually 5^10 mm less than the
container diameter,allowing the billet to enter the container
easily. The circumscribed diameter ofthe prole is usually less than
0.9 times the diameter of the container, but speciallydesigned dies
with a so-called expansion chamber may actually allow for d >Dc.
The section thickness often varies over the cross section of the
prole. Thereduction ratio is normally in the range of 20^80. If R
is very high (R> 70) andthe section is of a proper shape, the
die is usually designed with more than onedie opening (Fig. 5). In
this case, the reduction ratio is:R AcAsnn number of die
openingsWhen an extrusion press cycle is carried out (see Sec. 4
for details), a small partof the billet is left in the container,
the discard (Fig. 6). The length of the discard isnormally around
10^20 mm.. Discard length: Ld. Discard weight: Wd r p4D2cLd kg. The
weight of the extruded section: Ws Wb Wd kg. Length of the extruded
section: Ls Wsws mFigure 4 Continuous extrusion.388 Stpren and
Moe
2.2 The DieThe tooling package is to perform the deformation of
the aluminum and must nat-urally withstand very large forces. Tools
are generally made of high strength steelssuch as H11 and H13, and
surface in direct contact with the owing material ishardened
through nitriding prior to any use. Furthermore, the complete
toolingpackage will be comprised of a great number of parts which
all are meant to supportthe die when pressure is applied by the
stem. The complete tooling package will beFigure 6 Billet, discard,
and the extruded section.Figure 5 A multihole die.Extrusion
389
designed differently for the extrusion of hollow or open
proles. In any case,however, a bolster will be situated directly
behind the die and provide the mainsupport. The die and bolster
will then be placed in a horseshoe clamp, which is rmlyattached to
the press structure.In the case of extrusion of open sections one
die design does not differ signi-cantly from another although the
bolster may provide varying degrees of support.Various die designs
have, however, been developed for the extrusion of hollowproles.
The names of the most commonly used die types are porthole,
spiderand bridge, and for the extrusion of 6XXX-alloys porthole
dies have traditionallybeen most popular, partly due to the ease
with which they can be cleaned afterextrusion.The design of a
porthole die is displayed in Fig. 7. The outer contour of
thesection is formed by the die plate (Fig. 7(a)). The tongue will
be less stiff and weakerthan the rest of the plate because it
supports the pressure from the deformingmaterial on the tongue only
along one edge. The inner circumference of the sectionis formed by
the mandrel (Fig. 7(b). The mandrel is an integrated part of the
portholeFigure 7 Billet, die, and extruded section in the process
of extrusion.390 Stpren and Moe
die, connected to the rest of the die by webs, or bridges. In
the mandrel a groove ismachined out. This groove enables the
internal rib in the hollow section to be for-med.The deforming
alloy is owing over the bridges and down into the feeder
ports.Under each bridge, in the weld chamber, the two neighboring
metal streams areforge-welded together. In this process the
temperature of the material will not exceedthat of melting, but
welding will take place due to high pressures and diffusion
rates.The alloy is also owing into the groove in the mandrel from
two sides, and in thecenter of the groove the two streams of metal
are forge-welded, before the materialows into the bearing channel.
All such welds are denoted seam welds. If pressuresare not high
enough in the weld zones, insufcient welding will take
place.Furthermore, if material ows in an uncontrolled manner, one
will not be ableto predict the exact position of the weld. All
these phenomena are highly unwantedand, hence, detailed studies of
such can be found in the literature [4].When designing mandrels one
has to keep the following in mind:. The stiffness and strength of
the bridges should be optimized. The feederports should at the same
time be as large as possible in order to reducethe load on the
mandrel and allow for higher extrusion speed. This will,however,
result in a weak bridge construction with unwanted exibilityand an
increased risk of die deection.. Controlled ow out of the bearing
channel should be sought. The die andthe bearing channel should be
designed so that the section leaves thebearings at a uniform speed
and without generating excessive tensile orcompressive stresses. Of
special importance is the control of metal owand die welding of the
inner rib, because this cannot be inspected fromoutside during the
press cycle.. The surface of the section should be homogeneous and
leave the die withoutstreaks and stripes at the highest acceptable
speed.Clearly, there is a complex, but a very fascinating
design-optimizing challengehere. Today, die design competence
exists mainly as practical knowledge by highlyskilled die
designers, die producers and die correctors in the die shops. As
willbe pointed out in Secs. 4 and 5, however, the development of 3D
computer simu-lation of hot extrusion processes is approaching such
a level of precision that itcan be used as a tool for die design.
It must, however, be done in close cooperationwith skilled and
experienced die specialists.2.3 The Manufacturing
SystemSatisfactory control of the material ow may be viewed as the
key element in a suc-cessful production of aluminum proles. In this
context the last assertion hastwo alternative interpretations, and
both are in fact equally correct. In order to pro-duce extrusions
with the desired quality at an optimum pace, one has to
establishsome sort of an understanding of the mechanisms of plastic
ow of material inthe container and die. However, if an enterprise
is to succeed economically inthe extrusion business, it is as
important that it masters the logistics, that is thecontrol of the
material ow in and around the production facilities. The
extrusionprocess is carried out in an extrusion plant, which often
has a lay out similar toExtrusion 391
that presented in Fig. 8. Although heat treatment in general is
the most time con-suming part of the production system, other
process steps may in fact constitutethe actual bottlenecks. The
pressing of proles is one such as it is non-continuous,and as
considerable time is spent on changing dies, reloading new material
intothe container and performing maintenance tasks. Procedures are
made even morecomplicated as new production orders for proles often
may necessitate several trialruns on the press. If the material is
not transported effectively, down times may easilybe long, and the
most important parameter of all, productivity, will, consequently,
below.As is seen on Fig. 8 the extrusion process is comprised of a
great number ofsteps. One of the most important, however, is the
production of raw materialfor the process, and this usually does
not take place in the plant. Feed stock forthe process is logs,
normally in lengths of 6^7 m. They are supplied from the casthouse
of primary aluminum smelter or a secondary (recycled) aluminum cast
house.The logs are produced as visualized in Fig. 9.The liquid
metal at temperature above 700C is cleaned, added alloyingelements
and grain rener before entering the casting table. By passing the
castingmolds with direct water cooling, the liquid aluminum alloy
solidies into a log. Aftercasting, the log is homogenized in a
temperature cycle that secures the best possibleextrudability by
establishing a homogeneous distribution of alloying elementsand by
dissolving phases with low melting points, typically Mg2Si [5,6].
The logsare then transported to the extrusion plant.In the plant a
number of distinct processing steps takes place (Fig. 8). The
logsare rst taken one by one from the log stacker and transported
to the inductionheater. Here, a certain temperature prole is
imposed on the log, and it is thencut into billets of a prescribed
weight. In some plants the logs are cut prior toany heating.Figure
8 Layout of an extrusion plant.392 Stpren and Moe
The billet is then loaded into the extrusion press, where the
ram pushes it intothe container. The end of the billet surface in
contact with the ram, has been givena coating so that it does not
stick to the dummy block between the ram and thebillet. Because the
billet has smaller diameter than the container bore, it is givenan
upsetting in order to ll the container. In this phase there is a
risk of entrappingair in the container, and, thus, the ram stops
after upsetting, unloads, and movesa small distance backwards to
let the possible entrapment leave. This is calledthe burb
cycle.Thereafter, the extrusion process commences. The ram pushes
the billetthrough the die opening. The load capacity of the press
with a container diameterof 0.178 m is normally 16 MN, which
corresponds to a specic pressure of 643 MPa.If the container
diameter is 0.208 m, the load capacity is normally 22 MN and
thespecic pressure 647 MPa. The temperature of the billet prior to
extrusion is inthe range 450^470C. In the induction heater, the
billet may have been given varyingtemperature along its length in
order to compensate for the heat generation causedby the shearing
along the container walls when it is pushed through the
container(see also Sec. 4). This is called tapering, and the
highest temperature is usuallyin the front end of the billet. The
temperature of the section leaving the die is inthe range of
550^600C. The taper should be given in such a way that the runout
temperature is constant as this will result in minimum variation of
dimensionsand properties during the press cycle.As the section
front leaves the die, it is gripped by a puller, which guides
thesection out on the run out table. The prole is then quenched and
further cooleddown when moving sideways along the table. The
lengths of the proles upon leavingFigure 9 Direct chilling casting
(DC-casting) of logs.Extrusion 393
the die may be from 20 to 50 m, depending on the length of the
billet and thereduction ratio. Normally, a number of charges
(billets) are performed with the samedie in a production set up. In
this case, one may weld the prole from the new chargedirectly to
the one produced in the foregoing charge, creating a so-called
charge weld.This procedure simplies production, but necessitates
cutting of the prole duringextrusion. On the cooling table the
section is given a plastic deformation of 0.5^2%elongation in order
to eliminate internal stresses due to uneven cooling over thecross
section of the prole and straighten up possible bends and twists
before goinginto the cutting saw. The extruded section is nally cut
into prescribed lengths,normally 6 m. The process of cutting may
vary somewhat from one plant to another.The cut sections are
stacked in bins and transported through the aging ovenwhere they
spend 3^6 hr at temperature in the range of 170^190C. After
agingthe sections are inspected and packed before they are
delivered to the customerfor further fabrication and surface
treatment, followed by joining and assemblinginto the nished
component or product.With a generic aluminum section (Fig. 10) some
important features andcharacteristics of die design and
productivity for aluminum extrusions will bedemonstrated.An order
of 200 sections a' 6 m of alloy AA6060 (Al-MgSi0.5) shall be
produced in a 16MN press with container diameter of 0.178 m and run
out table length 42 m. Thefollowing typical process parameters can
be calculated and controlled:. The cross sectional area of the
container is:Ac p4 0:1782 24:9 103 m2. The cross sectional area of
the extruded section isAs 0:084 0:02 2 0:028 0:016 0:0032 p
0:00152104 0:437 103 m2. The reduction ratio can, thus, be
calculated to:R AcAs 24:8850:437 57Figure 10 A generic extruded
aluminum section.394 Stpren and Moe
This is a reduction ratio within the acceptable range for a one
hole die.. The circumscribed diameter of the section is:d 0:022
0:0842p 0:086 mThis is well bellow the maximum recommended diameter
of 0:9 0:178 0:16m. Special features of the section shape that
should be noticed, are a hollowrectangular section with constant
wall thickness, an outer tongue andan inner rib. Furthermore, the
prole is symmetric about the horizontalaxis.2.4 Productivity and
CostA number of aspects are important to consider for a customer
who is to choosebetween the many different suppliers of aluminum
proles. As a great numberof sections ought to and have to be
designed and manufactured for only one producttype, customer
service stands out as particularly important. Furthermore, the
sup-plier must of course be able to deliver the section requested
within an agreed timelimit and to the specied quality. If the prole
geometry is fairly complicated ora very high strength alloy is
chosen, some suppliers may fall out of the race, butfor most proles
one may not be able to differ on these grounds alone. And inthe
end, thus, all usually comes down to money. The basic parameters in
theextrusion business are the prices per meter or per kg extruded
section. Thesemeasures are dependent on the choice of alloy and the
geometry of the section,and one has to contact different suppliers
in order to determine exact prices. Theseshould not differ too much
since there is an active market mechanism working. Thismechanism
will, however, also pressure the suppliers to continuously seek to
increaseproductivity and cut costs. It is in the creative
negotiations between the customer andthe supplier that the right
price is agreed upon as a consequence of a section designwith the
right balance between requirements for functionality and the cost
efciencyin the extrusion plant. Important parameters that determine
the productivity andcost of the extruded section are:. Length
produced per press cycle. Length of end cuts that have to be
scrapped. Number of cut lengths per billet. The discard weight per
billet. Number of billets produced, i.e. gross weight delivered to
the press. Net weight ordered. The dead cycle, i.e. the time
between each press cycle. The ram speed. The acceleration time,
i.e. the time to reach the full ram speed. Time for die change. The
price of billet delivered at the press. Die cost. Production cost.
Unpredicted press stopExtrusion 395
. Unpredicted quality scrap, i.e. the number of sections
produced, which arenot conforming with the required quality.The
production cost may be measured as cost per minute extrusion time
spent.This measure contains all direct costs and man-hour costs in
the plant, divided by theestimated availability of the press in
minutes.The following example is meant to illustrate a typical
calculation of the cost per meterand cost per kg extruded prole.
The calculations are meant to refer to the sectionin Fig. 10, and
data from the example of th