U.S. patent application number 10/457517 was filed with the patent office on 2003-10-23 for cooking utensil made from aluminum alloy strips produced by continuous thin gauge twin roll casting.
This patent application is currently assigned to PECHINEY RHENALU. Invention is credited to Cortes, Marcel, Hoffmann, Jean-Luc.
Application Number | 20030196733 10/457517 |
Document ID | / |
Family ID | 29217341 |
Filed Date | 2003-10-23 |
United States Patent
Application |
20030196733 |
Kind Code |
A1 |
Hoffmann, Jean-Luc ; et
al. |
October 23, 2003 |
Cooking utensil made from aluminum alloy strips produced by
continuous thin gauge twin roll casting
Abstract
The invention concerns a method for making aluminium alloy
strips containing (by weight) at least 0.15 to 1.5% Fe and/or 0.35
to 1.9% Mn, with Fe+Mn<2.5% and optionally Si<0.8%,
Mg<0.2%, Cu<0.2%, Cr<0.2%, Zn<0.2%, and other elements
each <0.1% and <0.3 % in all, by continuous casting between
two cylinders cooled and shrinked to a thickness ranging between 1
and 5 mm, the force applied to the cylinders during casting,
expressed in tonnes per meter of strip width, being less than
300+2000/e, e being the cast strip thickness in mm. The invention
also concerns strips in alloy of the same composition, twin-roll
cast between 1 and 5 mm thick and having a product R.sub.0.2
(MPa).times.A (%) greater than 2500, and preferably than 3000.
Inventors: |
Hoffmann, Jean-Luc;
(Matzenheim, FR) ; Cortes, Marcel; (Brignoud,
FR) |
Correspondence
Address: |
DENNISON, SCHULTZ & DOUGHERTY
Suite 612
1745 Jefferson Davis Highway
Arlington
VA
22202
US
|
Assignee: |
PECHINEY RHENALU
|
Family ID: |
29217341 |
Appl. No.: |
10/457517 |
Filed: |
June 10, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10457517 |
Jun 10, 2003 |
|
|
|
09403744 |
Jan 3, 2000 |
|
|
|
09403744 |
Jan 3, 2000 |
|
|
|
PCT/FR98/00965 |
May 14, 1998 |
|
|
|
Current U.S.
Class: |
148/551 ;
148/538 |
Current CPC
Class: |
C22C 21/00 20130101;
B22D 11/0622 20130101; A47J 36/02 20130101 |
Class at
Publication: |
148/551 ;
148/538 |
International
Class: |
C22F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 1997 |
FR |
97 06407 |
Claims
1. Method for producing aluminium alloy strips containing(by
weight) at least one of elements Fe (from 0.15 to 1.5%) or Mn (from
0.35 to 1.9%) with: Fe+Mn<2.5%, and optionally containing Si
(<0.8%), Mg (<0.2%), Cu (<0.2%), Cr (<0.2%), Zn
(<0.2%), other elements <0.1% each and 0.3% in all, by
continuous twin-roll casting between cooled shrinked cylinders to a
thickness of between 1 and 5 mm, optionally followed by cold
rolling, the force applied to the rolls during casting, expressed
in t per metre of strip width, being less than 300+2000/e, e being
the thickness of the cast strip expressed in mm.
2. Method for producing aluminium alloy strips containing (by
weight) at least one of elements Fe (from 0.15 to 1.5%) or Mn (from
0.35 to 1.9%) with Fe+Mn<2.5%, and optionally Si<0.8%, Mg
<0.2%, Cu <0.2%, Cr<0.2%, Zn<0.2%, other elements
<0.1% each and 0.3% in all, by continuous twin-roll casting
between cooled shrinked cylinders, characterised in that the heat
exchange between the metal and the cylinder shells during casting
is slowed down such that the temperature of the cylinder shells is
higher than 80.degree. C., preferably than 130.degree. C.
3. Method in accordance with claim 2, characterised in that the
cylinder shell material has poor thermal conductivity.
4. Method according to any of claims 1 to 3, characterised in that
the arc of contact between the metal and the casting rolls is less
than 60 mm, preferably less than 56 mm.
5. Aluminium alloy strip containing (by weight) at least one of
elements Fe (from 0.15 to 1.5%) or Mn (from 0.35 to 1.9%) with
Fe+Mn<2.5% and optionally containing Si (<0.8%), Mg
(<0.2%), Cu (<0.2%) or Zn (<0.2%), other elements <0.1%
each and 0.3% in all, continuous cast to a thickness of between 1
and 5 mm, having at the as-cast state a product R.sub.0.2 (in
MPa).times.A (%) greater than 2500.
6. Strip according to claim 5 having a product R.sub.0.2.times.A
greater than 3000.
7. Strip according to either of claims 5 or 6 having a yield
strength R.sub.0.2 greater than 80 MPa.
8. Strip according to claim 7 having a yield strength
R.sub.0.2>100 MPa.
9. Strip according to any of claims 5 to 8, having an elongation
A>20%.
10. Strip in Mn-free alloy according to claim 9 having an
elongation A>30%.
11. Strip according to any of claims 5 to 10, having an earing
ratio of less than 7.
12. Strip according to claim 11, having an earing ratio of less
than 5.
13. Strip according to any of claims 5 to 12, characterized in that
the average size of the intermetallic particles containing Fe, Mn
and/or Si is no more than 0.4 .mu.m.
14. Strip according to any of claims 5 to 13, characterized in that
the size of at least 90% of the intermetallic particles containing
Fe, Mn and/or Si is less than 1 .mu.m.
15 Strip in Al-Mn alloy according to any of claims 5 to 14 with
Fe+Mn>1.4% having, after enamelling and/or PTFE anti-adhesive
coating treatment, a yield strength of more than 80 MPa, preferably
more than 100 MPa.
16. Strip cold rolled from a strip according to any of claims 5 to
15, characterized in that the k and n coefficients of the work
hardening curve R.sub.0.2=k.epsilon..sup.n, in which
.epsilon.=(2/{square root}3)l.sub.e (initial thickness/final
thickness) are such that k>150 and n<0.20.
17. Strip according to claim 16, characterized in that
n<0.15.
18. Enamelled and/or PTFE anti-adhesive coated cooking utensil
produced from strips according to any of claims 5 to 17.
19. Lacquered or varnished strip according to any of claims 5 to
17.
Description
TECHNICAL FIELD
[0001] The invention concerns a method for making aluminium alloy
strips with low magnesium and copper content, especially AlFeSi and
AlMn alloys, by continuous thin gauge twin-roll casting (<5 mm).
It also relates to strips of said alloys cast by thin gauge
twin-roll casting, and optionally cold rolled, having high
mechanical resistance, good formability and good anisotropy.
STATE OF THE ART
[0002] To obtain high mechanical resistance with aluminium alloys
not requiring subsequent structural hardening, recourse is
generally made to the addition of magnesium, as for the alloys of
the 5000 series as per the Aluminium Association nomenclature.
Aside from the fact that the casting of these alloys, in particular
their continuous casting, is fairly demanding, there are
applications for which the presence of magnesium in substantial
quantities is unacceptable. This is the case for example with
sheets intended for enamelled cooking utensils, in which magnesium
has an adverse affect on the adherence of the enamel layer, or for
strips intended for manufacturing heat exchanger blades brazed with
a fluoride flux, since the magnesium diffuses on the surface and
reacts with the flux. On this account, for these applications use
is made of the AlFeSi alloys in the 1000 series, AlMn alloys in the
3000 series or AlSiFe alloys in the 4000 series whose mechanical
resistance is distinctly lower. The article by M. DELEUZE and D.
MARCHIVE on the new wrought alloys "Les nouveaux alliages de
corroyage 4006 et 4007" Revue de l'Aluminium, June 1980, pp.
289-292, clearly demonstrates the demands of the cooking utensil
market placed upon aluminium alloy strip manufacturers.
[0003] These alloy strips are usually produced by vertical
semi-continuous casting of plates, hot rolling, cold rolling and
soft annealing. After enamelling, involving annealing at a
temperature in the region of 550.degree. C., or after PFTE coating
submitted to polymerization at around 450.degree. C., the sheets of
4006 and 4007 alloys have a yield strength R.sub.0.2 of between 55
and 80 MPa.
[0004] It is also possible to make strips by continuous casting, in
particular by twin-roll casting between two cooled steel cylinders.
Continuous casting, inasmuch as the solidification conditions
differ from the usual process, may lead to microstructures that are
also quite different. U.S. Pat. No. 3,989,548 for example by Alcan,
published in 1976 describes (example 9) aluminium alloys containing
at least one of the elements Fe, Mn, Ni or Si cast in strips by
continuous twin-roll casting to a thickness of 7 mm. The structure
of the cast strip contains rod-like fragile intermetallic compounds
with a diameter of between 0.1 and 1.5 .mu.m, which cold rolling
with a reduction of at least 60% breaks down into fine particles
less than 3 .mu.m in size. The strips obtained offer a good
compromise between mechanical resistance and formability, but these
properties only become of real interest in fairly high content
alloys for example AlFeMn alloys with Fe>1.4% and Mn>0.6%, or
AlFeNi alloys with Fe>1.2% and Ni>1.1%.
[0005] Patent FR 2429844 (=GB 2024870) by Norsk Hydro describes a
continuous casting method for producing alloy strips of AlMn, AlMg,
AlMgSi or AlMgMn offering both good mechanical resistance and good
ductility, to which less than 0.5% of anti-recrystallizing agents
are added (Zr, Nb, Ta, Hf, Ni, Cr, Ti, V or W).
[0006] U.S. Pat. No. 5,380,379 by Alcoa concerns the manufacture by
continuous twin-roll casting of fairly high content alloy foil with
1.35 to 1.6% iron, 0.3 to 0.6% manganese, 0.1 to 0.4% copper, and
less than 0.2% silicon. The silicon content is limited by the onset
of intermetallic phases of AlFeSi or AlMnSi type while the presence
of copper is necessary to impart sufficient mechanical resistance
to the product.
[0007] Conversely, patent application WO 96/27031 by Alcan concerns
alloys with lower alloying content containing 0.40 to 0.70% iron,
0.10 to 0.30% manganese, 0.10 to 0.25% copper and less than 0.10%
silicon, obtained by continuous casting of strips having a
thickness of less than 25 mm, whose properties are close to those
of alloy 3003. After cold rolling and annealing at between 350 and
400.degree. C., the alloy at temper "O" (according to norm NF EN
515) shows a grain size of less than 70 microns and properties very
close to those of alloy 3003 produced using a usual processing
range. This kind of composition may prove to be restrictive for
some applications in which lesser content alloys are used such as
1050 or copper-free alloys.
[0008] Patent EP 0039211 by Alcan describes a continuous casting
manufacturing process to a thickness of between 3 and 25 mm of AlMn
alloy strips containing 1.3 to 2.3% manganese, and possibly less
than 0.5% iron, magnesium or copper, less than 2% zinc and less
than 0.3% silicon. The processing range described is fairly complex
since it comprises homogenisation to precipitate at least one half
of the manganese in intermetallic form, cold rolling with a
reduction of at least 30% and one or more intermediate annealing
operations. The strips obtained show mechanical characteristics
which lead to a product A.times.R.sub.0.2, A being elongation in %
and R.sub.0.2 being the yield strength at 0.2% in MPa, whose value
is no more than 2100.
[0009] Patent EP 0304284 by Alcan describes an alloy with high
thermal stability containing from 1.5 to 2.5% manganese, 0.4 to
1.2% chromium, 0.4 to 0.8% zirconium and up to 2% magnesium, and
its production by continuous casting of strips having a thickness
of less than 4 mm. The very unusual chromium and zirconium
contents, especially when combined with an addition of magnesium,
lead to high mechanical resistance but to the detriment of
elongation which remains less than 10%, making these alloys unfit,
even in the absence of magnesium, for the production of cooking
utensils for example.
[0010] The continuous casting of aluminium alloy strips between
cooled cylinders has been known for many years. For a moderate
investment cost it can be used to produce a fairly wide range of
alloy strips which do not require subsequent hot rolling. In recent
years, considerable progress has been made by manufacturers of
casting machines to reduce the thickness of the cast strip, which
can in some cases be reduced to approximately 1 mm, thereby
reducing the amount of cold rolling needed and can even do away
with the latter for final gauges of >1 mm provided that the
quality of the cast strip is sufficient for intended applications.
This progress has been the subject of several papers at technical
meetings for example
[0011] M. CORTES "Pechiney Jumbo 3 CM.RTM.. The new demands of thin
strip casting" Light Metals TMS 1995, p. 1161.
[0012] B. TARAGLIO, C. ROMANOWSKI "Thin gauge/High Speed roll
casting technology for Foil Production" Light Metals TMS 1995, pp.
1165-1182. This article mentions a certain number of alloys which
may be cast on the described machine, for example alloys 1050,
1060, 1100, 1145, 1188, 1190, 1193, 1199, 1200, 1230, 1235, 1345,
3003, 8010, 8011, 8111 and 8014. The article also indicates that
the force of the roll-mill used for continuous twin-roll casting is
3000 t, which stresses the need to use high forces for thin gauge
casting.
PURPOSE OF THE INVENTION
[0013] The purpose of the invention is to obtain aluminium alloy
strips with low Mg and Cu content which, at the as-cast state or at
the cold rolled state, offer mechanical resistance which is
distinctly greater than that of similar strips having the same
composition obtained by conventional casting or thick-gauge
continuous casting, and which also have at least equivalent
formability and anisotropy. A further purpose is to obtain
aluminium alloy strips which recrystallize at a much higher
temperature than the recrystalization temperature of the same
alloys obtained by conventional casting, in particular to obtain
alloys which do not recrystallize at the usual enamelling or PTFE
polymerisation temperature for cooking utensils.
SUBJECT OF THE INVENTION
[0014] The subject of the invention is a method for producing
aluminium alloy strips containing (by weight) at least one of
elements Fe (from 0.15 to 1.5%) or Mn (from 0.35 to 1.9%) with
Fe+Mn<2.5%, and optionally containing Si (<0.8%), Mg
(<0.2% preferably <0.05%), Cu (<0.2% preferably <0.1%),
Cr (<0.2% preferably <0.02%) or Zn (<0.2% preferably
<0.1%), the other elements being <0.1% each and 0.3% in all,
by continuous casting between cooled shrinked cylinders, to a
thickness of between 1 and 5 mm, optionally followed by cold
rolling, the force applied to the casting rolls expressed in t per
metre of strip width being less than 300+2000/e, e being the
thickness of the strip expressed in mm. Casting is preferably made
with an arc of contact of less than 60 mm with slowed down heat
exchange such that the temperature of the cylinder bands remains at
a temperature above 80.degree. C., preferably above 130.degree.
C.
[0015] A further subject of the invention is aluminium alloy strips
having the above composition and a gauge of between 1 and 5 mm,
obtained by continuous twin-roll casting which, at as-cast state,
have a product R.sub.0.2.times.A of >2500 (preferably >3000),
R.sub.0.2 being the yield strength at 0.2% of the strip expressed
in MPa and A the elongation expressed as %. The strips have a yield
strength R.sub.0.2 of more than 80 MPa, their elongation A is
greater than 20% and their earing ratio is less than 7, preferably
less than 5.
[0016] Finally another subject of the invention is an AlMn alloy
strip that comes under the preceding composition (Mn>0.35%) such
that the sum of the Fe+Mn contents lies between 1.4 and 2.5%
(preferably between 1.5 and 2%) twin-roll cast to a thickness of
<5 mm and optionally cold rolled, which after enamelling or PTFE
coating has a yield strength of >80 MPa preferably >100
MPa.
DESCRIPTION OF THE INVENTION
[0017] The invention is based on the finding that a particular
adjustment of the parameters for continuous thin gauge twin-roll
casting can, for alloys without heat treatment and without the
addition of magnesium or copper, achieve a set of fully surprising
mechanical characteristics at the cast or cold rolled state, in
particular a much higher yield strength than that of strips having
the same composition cast in conventional manner or by continuous
thick gauge casting or by continuous thin gauge casting under
different conditions.
[0018] The invention applies to aluminium alloys without heat
treatment and virtually free of magnesium and copper. They are
mainly alloys with very low additional element content, such as
1050 but still containing at least 0.15% iron, AlFeSi alloys
possibly containing up to 1.5% iron and 0.8% silicon, such as
alloys 1050, 1100, 1200, 1235, 8006 (this latter also containing
manganese), 8011 or 8079, and finally manganese alloys containing
between 0.35 and 1.9% Mn, such as alloy 3003.
[0019] For alloys containing silicon, the possibility of reaching a
silicon content as high as 0.8% is an advantage compared with
conventional casting and enables the recycling of some alloys, such
as those used for brazed exchangers coated with an AlSi alloy.
However, beyond 0.8%, the formation is observed of AlMnSI or AlFeSi
primary phases which may hinder casting, in particular due to the
risk of solidification in the injector. There is even a risk of the
onset of primary phases for manganese alloys when Mn exceeds 1.9%
or when the sum Mn+Fe exceeds 2.5%.
[0020] The strips of the invention have an original microstructure.
The average particle size of intermetallic iron, silicon or
manganese phases is in the region of 0.4 .mu.m, and at least 90% of
these particles are less than 1 .mu.m in size. This microstructure
can be seen under electron scanning microscopy on a polished metal
section. To determine particle size, digital analysis of
micrographs is used to determine their surface area A, from which
the size parameter d can be calculated using the formula
d=24{square root}A/.pi..
[0021] The method for producing aluminium alloy strips according to
the invention will be described with reference to FIG. 1 which
gives a longitudinal cross-section diagram of a continuous
twin-roll casting machine. This machine comprises a liquid metal
feed (1), an injector (2) which injects the liquid metal into the
space between twin cooled rolls (3 and 4). Each roll (3) and (4)
comprises a cylinder body (3a) and (4a) with a cooling water
circuit leading to its surface. The cylinder body is shrinked with
a tubular shell (3b) and (4b) which ensures mechanical and heat
contact with the metal and may be replaced when worn. Metal
solidification is made between the rolls and a solid metal strip
(5) emerges. By arc of contact is meant the distance d separating
the injector outlet (2) and the plane of the roll axes (3) and
(4).
[0022] The alloy is cast in a strip having a thickness of between 1
and 5 mm. The main condition to be heeded is to cast with
relatively low separating force unlike the teaching of the prior
art. This force expressed in tonnes per metre of cast strip width
must remain below 300+2000/e, e being the cast thickness measured
in mm. Therefore for a cast thickness of 2.5 mm, the force must
remain lower than 1100 t per metre of width.
[0023] Other arrangements have a favourable influence on the
mechanical characteristics of the cast strip. For example, contrary
to expectation, it is preferable that the heat exchange between the
metal undergoing solidification and the cylinder shells should not
be too good. This leads to a high cylinder shell temperature,
typically more than 80.degree. C., preferably more than 130.degree.
C., and can be achieved with shells in metal having poor thermal
conductivity (for example a molybdenum steel) and relatively thick
(for example between 50 and 100 mm). Another favourable
arrangement, which partly relates to the preceding arrangement, is
to operate with a rather low arc of contact, less than 60 mm,
preferably less than 56 mm. This reduces the heat exchange between
the metal and the cylinder shells and can be achieved by moving the
injector close to the rolls and/or using relatively small
rolls.
[0024] These casting conditions impart upon the strip the
above-described microstructure and achieve non-recrystallization of
the alloy until it reaches a temperature in the region of 380 to
400.degree. C., which enables high mechanical resistance for
example to be maintained after enamelling or PTFE coating treatment
for cooking Utensils produced from this strip.
[0025] The mechanical resistance of the alloy strips of the
invention, at the as-cast state, is distinctly greater than that of
strips in the same alloy and of the same thickness obtained by
conventional plate casting with hot and cold rolling, and even of
strips made by continuous casting under different casting
conditions. The yield strength, for all the alloys of the
invention, is always higher than 80 MPa and most often more than
100 MPa, in particular for the manganese alloys. Good formability
is also achieved with elongation that is always greater than 20%
(and 30% for Mn-free alloys such as 1050 or 1200) and above all
there is particularly favourable compromise between yield strength
and elongation measured by the product R.sub.0.2.times.A (R.sub.0.2
expressed in MPa and A in %), this product being at all times more
than 2500, and most frequently more than 3000. Good anisotropic
properties are also obtained with an earing ratio that is always
less than 7, and most often less than 5.
[0026] The mechanical characteristics are measured in the length
direction in accordance with standard EN 10002. The earing ratio is
measured in accordance with standard NF-EN 1669 with a stamping
ratio of between 1.8 and 1.95, preferably 1.92, and is expressed
(as %) by the ratio 2.times.(mean height of 4 ears-mean height of 4
troughs)/(mean height of 4 ears+mean height of 4 troughs), the
anisotropy of the this type of alloy generally being of 4 ear type
at 45.degree..
[0027] For manganese alloys with Mn+Fe>1.4%, after annealing up
to 550.degree. C. (for example enamelling and PTFE annealing) a
yield strength of >80 MPA is obtained most often >100
MPa.
[0028] After one or more cold rolling passes, the strips of the
invention have a yield strength R.sub.0.2 that is significantly
much higher than that of strips produced by conventional casting
and subjected to the same work hardening. The yield strength after
work hardening is usually expressed by a work hardening law
according to the formula
R.sub.0.2=k.epsilon..sup.n where .epsilon.=(2/{square root}3)ln
(initial thickness/final thickness)
[0029] the initial thickness being the as-cast thickness for
continuous strip casting, and the strip thickness at the last
recrystallization annealing for strips produced by conventional
casting from plates and hot rolled. For cold rolled strips of the
invention with a reduction coefficient of no more than 60%, that is
to say for .epsilon. values lying between 0 and 1, the k
coefficient is always greater than 150, whereas it is less for
strips produced by conventional casting, and n is lower than 0.20
(and most often than 0.15) whereas it is greater than 0.20 for
strips produced by conventional casting.
[0030] This set of properties is particularly advantageous for the
production of drawn cooking utensils for which it is necessary to
use magnesium-free alloys. With this thin-gauge casting it is
possible to use as-cast strips, which offer an advantageous cost
price, and the heat treatments involved for enamelling and coating
with anti-adhesive products such as polytetrafluorethylene (PTFE)
do not lead to a loss in mechanical characteristics. These
properties are also of interest for the production of fins for heat
exchangers, in particular for radiators or motor vehicle air
conditioning systems intended to be assembled with tubing by
brazing with a non-corrosive flux. Here again the presence of
magnesium is unacceptable and furnace brazing does not lead to any
reduction in mechanical characteristics. Finally, they are also of
interest for the production of varnished or lacquered products
which need to undergo heat treatment for the coating.
EXAMPLES
Example 1
Influence of the Separating Force
[0031] On a continuous twin-roll 3CM casting machine made by
Pechiney Aluminium Engineering, 5 alloys were cast whose chemical
composition (by weight %) is given in table I:
1TABLE I Alloy Mn Fe Si Mg 8006 0.44 1.29 0.15 0.028 3003 1.1 0.40
0.10 -- 1050 -- 0.20 0.14 0.002 8011 -- 0.75 0.70 -- 1200 -- 0.55
0.20 --
[0032] In each case, measurements were taken of cast thickness,
separating force per metre of strip width, compared with the limit
value of 300-2000/e, and the mechanical characteristics of the
as-cast strip tensile strength R.sub.m (in MPa), yield strength at
0.2% R.sub.0.2 (in MPa), elongation A (%) and earing ration (%)
according to standard NF-EN 1669 with a drawing ratio of 1.92. The
results are grouped together in table II:
2TABLE II e Force 300 + R.sub.m R.sub.0.2 A R.sub.0.2 .times.
Earing Alloy mm t/m 2000/e MPa MPa % A ratio 8006 3.1 867 945 166
118 25 2950 2.8 3003 3.0 900 967 158 114 23 2622 4.4 1050 3.5 720
871 106 81 39 3159 4.0 8011 3.9 1018 813 156 112 23 2576 9.0 1200
3.0 1100 967 121 93 32 2976 8.9 3003 3.5 1400 871 181 141 17 2297
8.0
[0033] It is found that, in the first 3 cases, both an elongation
of more than 20% and a product R.sub.0.2.times.A of more than 2500
is obtained, together with an earing ratio of less than 7. On the
other hand, for the 3 last cases in which the force is too high,
the earing ratio is quite substantial which renders the strip unfit
for stamping.
Example 2
Influence of Cylinder Band Temperature
[0034] For alloys 1050 and 3003 a comparison was made of the
mechanical characteristics of the cast strips at respective
cylinder shell temperatures of 130.degree. according to the
invention) and 700 (outside the invention). The results are given
in table 3:
3TABLE III e R.sub.m R.sub.0.2 A R.sub.0.2 .times. Alloy (mm) temp
(.degree.) (MPa) (MPa) (%) A 1050 3 130 106 81 39 3159 1050 3 70
105 80 29 2320 3003 3.5 130 158 114 23 2622 3003 3 70 149 114 18
2052
[0035] It is found that a high cylinder shell temperature
contributes to increasing elongation without detriment to
mechanical resistance.
Example 3
Influence the Arc of Contact and Separating on Earing Ratio
[0036] The earing ratio was measured on strips cast to different
thicknesses with different separating forces and arcs of contact of
different lengths. The results are grouped together in table
IV.
4TABLE IV e Force 300 + 2000/e Arc of Earing Alloy mm t/m t/m
contact mm ratio 8006 3.1 867 943 45 2.8 3003 3.0 937 967 45 3.2
8006 3.2 867 925 45 3.2 8006 3.1 833 945 45 2.4 3005 3.0 567 967 45
1.5 3005 2.35 833 1151 45 1.7 1050 1.95 727 1326 45.5 6.3 1050 1.7
767 1476 45.5 6.7 1050 4.0 930 800 52 4.7 1050 3.0 920 967 52 6.0
1050 3.1 1253 945 70 8.5 1050 3.5 720 871 53 4 8011 3.9 1019 813 57
9.0 1200 4.15 780 782 58 6.5 1200 4.15 769 782 58 5.4 1200 3.6 1055
856 62 8.8 8011 3.8 1440 826 55 7.5 8011 3.7 1440 841 56 8.2 1200
3.0 1230 967 55 12 8011 3.8 1104 826 57 7.6 8011 3.35 850 901 56
5.2 8011 3.55 979 862 56 9.5 8011 3.65 925 849 57 9.6
[0037] It is found that there is no correlation between the cast
thickness and the earing ratio, but that high earing ratios (>7)
correspond to high forces (>300+2000/e) and/or high arcs of
contact (>56 mm).
Example 4
Mechanical Characteristics after Enamelling and PTFE Coating
[0038] For the different alloys of the invention measurements were
made of the mechanical characteristics at as-cast state, after
anti-adhesive PTFE coating comprising resin polymerisation
annealing at 420.degree. C. and after enamelling comprising an
enamelling annealing at 560.degree. C. The results after heat
treatment were compared with those obtained with alloys 4006 and
4007 which underwent conventional processing, and which are the
alloys with the highest performance used for the production of
enamelled or PTFE coated cooking utensils. The results are given in
table V:
5TABLE V After PTFE After Crude cast coating enamelling e R.sub.m
R.sub.0.2 A R.sub.m R.sub.0.2 A R.sub.m R.sub.0.2 A All mm MPa MPa
% MPa MPa % MPa MPa % 3003 3.0 158 114 22 154 110 23 148 105 26
3003 3.5 181 141 17 173 136 20 156 111 25 8006 3.1 166 118 25 151
108 27 132 85 32 8011 3.9 156 112 23 139 75 28 125 36 36 1200 3.0
121 93 32 100 64 34 80 20 50 4006 120 55 48 142 59 42 4007 161 68
30 173 76 26
[0039] It is found that after PTFE coating, the alloys with lesser
alloying content 1200, 8006 and 8011 made with continuous casting
according to the invention still show a yield strength that is
comparable with that of alloys 4006 and 4007 specially designed for
their resistance to high temperatures. After enamelling, alloy 3003
according to the invention shows a much higher yield strength than
that of alloys 4006 and 4007 made by conventional casting whereas
these alloys are specially designed for enamelling.
Example 5
Work Hardening Laws
[0040] The work hardening curves were compared of alloys 1200 and
3003 produced by conventional casting and by continuous casting
according to the invention, from an initial thickness of 3 mm up to
final thicknesses reaching 1.25 mm, that is to say for values e
lying between 0 and 1. The respective values of the k and n
coefficients for the curve R.sub.0.2=k.epsilon..sup.n are given in
table VI:
6 TABLE VI Alloy cast k n 1200 invention 169 0.13 1200 conventional
105 0.21 3003 invention 229 0.12 3003 conventional 150 0.22
[0041] It is found that for the strips of the invention in the
domain under consideration, k is higher and n is lower, which leads
to greater work hardening since .epsilon.<1 and n<1.
* * * * *