Title of Invention

METHOD FOR MANUFACTURING AN AUSTENITIC PRODUCT AND ITS USE THEREOF

Abstract The present invention relates to a method to produce an austenitic stainless substrate alloy of low Al content being coated with an alloy of higher Al content at a temperature between 100°C and 600°C, so that the resulting product has an Al content of 4,5-12% by weight.
Full Text

The present invention relates to a method for the manufacture of an austerfitic
product having elevated content of aluminium, and)the use thereof in
applications where high temperature resistance in the form of oxidation resis-
tance and improved mechanical properties are required.
Background of the Invention
With increasing application temperatures for steel materials in various high-
temperature applications, today's ferritic materials have, more precisely ferritic
FeCrAI materials, occasionally turned out to be mechanically weak in order to
resist the stresses that arise upon use at high temperatures in the form of fast
changes of temperature, gas flows varying in temperature, direction and/or
composition, and mechanical stresses, such as, e.g., vibrations.
EP-B1-1235682 discloses the use of an austenitic nickel base or cobalt base
alloy that is coated with aluminium or aluminium alloy and rolled to finished
dimension. In such a way, by means of a heat treatment at temperatures above
600 °C, foil of a min. thickness of approx. 50 urn can be manufactured, which
has been tested to approximately 1100 °C. At 1100 °C, the mass of the sample
increased by up to 7,6 % after 400 h. The disadvantage is, in comparison with
conventional FeCrAI material, the relatively high oxidation rate, which is
regarded to be the decisive factor for the service life of the catalyst supporting
material.
Austenitic alloys generally have higher mechanical strength at the same high
temperatures than ferritic alloys. Austenitic materials of high aluminium content
have a considerable improved oxidation resistance in comparison with austeni-
tic materials of lower aluminium contents by virtue of the material having a very
low ductility at typical hot-working temperatures, i.e., at 750 to 1200 °C.


A metallic material for catalysts with elevated working temperatures and in
increased mechanical load has to meet the following requirements: an improved
mechanical strength in relation to materials used today, as is disclosed in US-B-
5,578,265 and furthermore considerably better oxidation resistance than the
austenitic, high-strength materials disclosed in EP-B1-1235682. In order to
allow the use thereof as supporting material in a catalyst, a foil material of a
thickness of 50 µm should not increase in weight more than 6 % after 400 h of
oxidation in air at 1100 °C, preferably the increase in weight should be below
4 %. An Al alloyed austenitic steel or nickel or cobalt base alloy of more than
4,5 % of Al can be expected to have sufficiently satisfactory mechanical proper-
ties and may, for a foil having a thickness of 50 urn, during certain circum-
stances attain an increase in weight corresponding to 6 % after 400 h at
1100 °C, but by virtue of utmost limited hot workability at Al contents above 4,5
% by weight, such products are not possible to produce as thin strips by means
of conventional methods. Furthermore, the oxidation resistance of such materi-
als are still inferior compared to ferritic materials used today.
Therefore, there is a need for a material that is more heat-resistant and oxida-
tion-resistant and has a higher mechanical strength than those of today., Fur-
ther, though, this material has to have satisfactory or better manufacturing
properties than the materials known hitherto. This is the case for all different
product forms that are used at the above-described conditions, such as strip,
foil, wire, sheet-metal plate and tube.
Summary of the Invention
It is therefore an object of the present invention to provide a method where, by
an austenitic substrate alloy of low Al content being coated with an aluminium
composition of higher Al content at a temperature between 100 °C and 600 °C,
the resulting product has an Al content of 4,5-12 % by weight, preferably 5,5-
12% by weight.


It is an additional object of the present invention to provide an austenitic alloy
material for use in high-temperature applications, manufacturable by said
method.
Brief Description of the Accompanying Drawing

Figure 1 shows results of hot ductility testing, so-called Gleeble testing, the
reduction of area to fracture being measured as a function of the
test temperature.
Figure 2 shows the oxidation rate in air at 1000 °C of examples C and D in
comparison with comparison example 1.
Figure 3 shows the oxidation rate in air at 1100 °C of example C and
comparison example 1.
Figure 4 shows the oxidation rate in air at 1100 °C of examples C, E and F
as well as of comparison example 1 having the thicknesses of 50
µm and 3 mm, and comparison example 3.
Figure 5 shows the content of aluminium in an Al-coated material after
annealing times of different length at 1050 °C, plotted as a function
of the distance from the surface.
Figure 6 shows the micro structure in an Al-coated and annealed material
after 50 min annealing at 1150 °C in Ar gas, wherein 0 = Fe-Cr rich
layer, 1 = Ni and Al rich layer, 2 = diffusion zone, 3 = compSsition of
the substrate material.
Description of the Invention
These objects are attained by means of an austenitic product that is
manufactured by coating an austenitic substrate alloy with the following
composition (in % by weight): 20-70 % of Ni, 15-27 % of Cr, 0-5 % of Al, 0-
4 % of Mo and/or W, 0-2 % of Si, 0-3 % of Mn, 0-2 % of Nb, 0-0,5 % of Y, Zr
and/or Hf, 0-0,5 % of Ti, 0-0,1 % of one or more rare earth metals (REM) such


as, e.g., Ce, La, Sm, 0-0,2 % of C, 0-0,1 % of N, balance Fe and normally
occurring impurities, with an aluminium composition such as aluminium or an
aluminium-based alloy such as is described below.
A preferred composition of the substrate material is (in % by weight) 25-70 % of
Ni, 18-25 % of Cr, 1-4 % of Al, 0-4 % of Mo and/or W, 0-2 % of Si, 0-3 % of
Mn, 0-2 % of Nb, 0-0,5 % of Y, Zr and/or Hf, 0-0,5 % of Ti, 0-0,1 % of one or
more rare earth metals (REM) such as, e.g., Ce, La, Sm, 0-0,1 % of C, 0-
0,05 % of N, balance Fe and normally occurring impurities.
By a two-stage process, the content of aluminium of the final product as well as
its mechanical properties and oxidation resistance can be optimized independ-
ently of each other.
After coating the substrate material with aluminium or an aluminium-based
alloy, the final alloy has a composition consisting of (in % by weight) 25-70 % of
Ni, 15-25 % of Cr, 4,5-12 % of Al, 0-4 % of Mo and/or W, 0-4 % of Si, 0-3 %
of Mn, 0-2 % of Nb, 0-0,5 % of Ti, 0-0,5 % of Y, Sc, Zr and/or Hf, 0-0,2 % of
one or more rare earth metals (REM) such as, e.g., Ce, La, Sm, 0-0,2 % of C,
0-0,1 % of N, balance Fe and normally occurring impurities.
The austenitic substrate material has in itself a good high-temperature strength,
which is increased by the presence of precipitations of Ni (Nb, Al) and, if
required, also by Mo and/or W in solid solution. Additionally increased mechani-
cal stability and resistance to grain growth may be given by the presence of
precipitations of carbides and/or nitrides of any one or some of the elements Ti,
Nb, Zr, Hf.
Carbon in solid solution or as carbides contributes to an increased mechanical
strength at high temperatures. Simultaneously, higher contents of carbon in the
substrate material imply deteriorated properties upon cold working. Therefore,


the maximal content of carbon in the substrate should be limited to 0,2 % by
weight.
Nitrogen in solid solution or as nitrides contributes to an increased mechanical
strength at high temperatures. Simultaneously, higher contents of nitrogen in
the substrate material imply that embrittling aluminium nitride may be formed in
the production of the substrate or after coating with aluminium or an aluminium-
based alloy. Therefore, the maximal content of nitrogen in the substrate should
be limited to 0,1 % by weight.
The austenitic alloy manufactured according to the invention is used in a coated
and not heat-treated state or after a diffusion annealing. The most favourable
compositions for the substrate alloy are obtained if it contains 1-4 % by weight
of Al. This content of aluminium gives the finished alloy an improved oxidation
resistance and an improved production economy without entailing an increased
risk of production disturbances in comparison with the manufacture of a material
of low content of aluminium. After coating with aluminium or an aluminium-
based alloy, the material should in total contain more than 4,5 % by weight of
Al.
According to the invention, the coating with aluminium or an aluminium-based
alloy should take place within a temperature range of the substrate that is lower
than the melting point of the aluminium, i.e., at a temperature between 100 °C
and 600 °C, preferably 150 °C-450 °C.
Addition of Zr and/or Hf and REM and/or Y and/or Sc gives an increased resis-
tance to peeling and flaking of the formed oxide. The finished product's contents
of said elements may be supplied by addition in the substrate alloy and/or in the
aluminium-based alloy that are used in the coating.
Certain compositions of the alloy according to the invention could be manufac-
tured by conventional metallurgy. However, unlike this, in production by means


of the process according to the present invention, a material can be obtained,
the microstructure of which is controlled and the oxidation properties and
mechanical properties of which are optimal. It is an additional advantage of the
process according to the present invention that the total content of aluminium of
the final product is not limited by the embrittling effect that contents of alumin-
ium above approx. 4,5 % by weight may give upon later cold and/or hot work-
ing. Furthermore, the method to coat a substrate material with aluminium or an
aluminium-based alloy according to the invention gives a final product, the
contents of which of, e.g., Mo, C, Nb can be considerably higher than in a con-
ventionally manufactured material without the presence of said elements
resulting in any noticeable deterioration of the oxidation properties.
The proper coating of the substrate alloy with aluminium or an aluminium-based
alloy may be effected by processes such as, e.g., dipping in melt, electrolytic
coating, rolling together strips of aluminium or an aluminium alloy from a gas
phase by so-called CVD or PVD technique. The coating with aluminium or alu-
minium-based alloy can be carried out after the substrate alloy has been rolled
or in another way been machined to desired product dimension. During this
process, a diffusion annealing may be carried out in order to provide a homo-
genization of the material and then plastic machining in one or more steps may
be carried out in order to provide the final product. Plastic machining, such as,
e.g., rolling or drawing may also be effected directly on a coated product of
larger dimensions than the desired final dimension. In this case, the pfastic
machining may be followed by annealing.
The content of aluminium in the final product can be varied by means of differ-
ent factors: the thickness of the substrate material in relation to the thickness of
the coating, the content of aluminium in the substrate material as well as the
content of aluminium of the coating.
However, as has been described above, the total content of aluminium in the
finished product always has to be at least 4,5 % by weight in order to secure


sufficient properties. The product may be used in the form of an annealed,
homogeneous material or a laminate or a material having a concentration gra-
dient of Al with the Al content being higher at the surface than in the centre of
the material.
Depending on the coating process used, various compositions of the applied Al
alloy are more suitable than others. The aluminium alloy contains 0-25 % of Si
and/or 0-2 % by weight of one or more of the elements Ce, La, Sc, Y, Zr, Hf
and/or 0-5 % by weight of one or more of the elements Mg, Ti, Cr, Mn, Fe, Ni,
Co and/or 0-1 % by weight of one or more of the elements B, Ge, preferably the
aluminium alloy should contain at least 90 % of Al, 0-10 % of Si and/or 0-2 %
by weight of one or more of the elements Ce, La, Sc, Y, Zr, Hf, more preferably
the aluminium alloy should contain at least 95 % of Al, 0-5 % of Si and/or 0-2
% by weight of one or more of the elements Ce, La, Sc, Y, Zr, Hf.
Embodiment examples
In the following, it is shown how the requirements on strength and oxidation
resistance are met by an austenitic Al alloyed material manufactured according
to the method described in the present invention. Furthermore, it is shown that a
material manufactured according to the same method is superior to a rfiaterial
that has the same composition but has been manufactured according to con-
ventional methods, in respect of high-temperature strength, oxidation resistance
and workability.
Example 1
Table 1 indicates examples of compositions of examined alloys. The alloys
according to examples A and B as well as the Comparative examples 1, 2 and 3
were manufactured in the conventional way by pyrometallurgy and hot working.



Comparison example 1 is an alloy that today is used as supporting material in
catalytic converters and that has acceptable oxidation resistance for this use.
Comparison example 2 is an austenitic alloy of high Al content, manufactured
by conventional methods. The yield upon hot working of said alloy was only
approximately 10 %, i.e., 90 % of the material had such internal defects in the
form of, e.g., cracks that it could not be used for further working.
The alloys according to examples A and B have compositions that are suitable
to be used as substrate materials in a coating process where a thin layer of
aluminium or an aluminium-based alloy is deposited on said substrate. From the
alloys according to Examples A and B as well as comparison example 1, 50 urn
thick strips were manufactured via hot rolling and cold rolling. The yield in the
production of the alloys in examples A and B was the same as comparison
example 1.

In order to avoid formation of aluminium nitride, the content of nitrogen in the
substrate materials is low. In order to limit this tendency further, Ti, Nb and/or Zr
and/or Hf were added. Addition of these elements results in the formation of
nitrides that are more stable than AIN, which entails a reduced formation of the
latter. Furthermore, the compositions are chosen in order to enable efficient
production of thin strips of the substrate material. For instance, the content of
carbon is below 0,10 %, which allows satisfactory metarial yields in cold working
processes. By the relatively high Al content in the substrates, the necessary
amount of Al that has to be deposited on the substrate is decreased with the
purpose of achieving sufficient Al content in the finished product.
In table 2, it is shown that the substrate alloys have a very good high-tempera-
ture strength; e.g., at 700 °C the ultimate strength of the alloys according to
examples A and B is up to 3 times larger than of the conventional material in
comparison example 1, and at this temperature the yield point in tension is 2,8
to 5 times larger than of comparison example 1. At 900 °C, the yield point in
tension of the alloy according to examples A and B is approximately 5 times
larger of for comparison example 1, while the ultimate strength is at least 3,5
times higher than of comparison example 1.


Thus, the two substrate alloys used in Examples A and B meet the require-
ments of sufficient mechanical strength and manufacturability as thin foil.
Figure 1 shows results of hot ductility testing, so-called Gleeble testing, where
the reduction of area to fracture is measured as a function of the test tempera-
ture, for the alloys according to Examples A and B and for comparison example
2. In order to be able to hot-work an alloy in practice, the reduction of area to
fracture should exceed 40 %. In order to obtain a reproducibly high yield in hot
working operations, the average reduction of area to fracture should be at least
70 % at a temperature difference of 100 °C.
From figure 1, it is clearly seen that the alloys according to Examples A and B
can be manufactured via hot rolling and/or forging, while the alloy according to
comparison example 2 cannot be manufactured with sufficient yield by means
of conventional methods. One consequence of this is that, in order to be able to
obtain the good oxidation resistance that an alloy according to Comparison
example 2 can be expected to have, the necessary Al content has to be added
after the alloy has been produced in the form of a thin strip. The alloys accord-
ing to Examples A and B are both sufficiently ductile at room temperature and at
elevated temperatures in order to be able to be cold-rolled to very thin strips
with satisfactory productivity, which is seen in that they could be manufactured
without problems down to material thicknesses of 50 urn, and are thereby good
candidate materials to be used as substrate materials for a coating with alu-
minium or an aluminium-based alloy Al.
Example 2
The alloys in examples C and D were manufactured by coating the two surfaces
of cold-rolled, 50 urn thick, strips of the alloy according to examples A and B,
respectively, by vaporization or sputtering with Al in such an amount that the
total Al content corresponded to 5,5-6 % (see table 3). The coating was
effected by a certain heating of the substrate material, however not to such a


high temperature that melted Al was present on the substrate. The coating with
Al or Al alloy according to the invention should accordingly be effected within a
temperature range of the substrate of 100 °C-660 °C, preferably in the tem-
perature range of 150-450 °C.

The alloy according to comparison example 2, which has approximately the
same total composition as the alloy in example C, could, as has been men-
tioned previously, be forged, but only with a very low material yield. Thus, the
limited hot ductility entails that this alloy hardly can be manufactured in the form
of thin strips. However, the same alloy has, as is seen in table 2, a very good
heat resistance; e.g., the ultimate strength at both 700 °C and 900 °C is 3 to 4
times larger than of the conventional material in comparison example 1, and the
yield point in tension is more than 4 times as large at both test temperatures.
Example 3
The thickness of the Al layer obtained on 50 µm thick strip according to example
C was measured by GDOES (Glow Discharge Optical Emission Spectroscopy),
a method that enables accurate measuring of compositions and thicknesses of
thin surface layers. The analysis showed that the sample had a total Al content
of 5-6 % by weight. These samples were oxidized in air at 1000 °C for up to
620 h. The results are shown in Figure 2. The alloy according to Example C has
an oxidation resistance that is comparable with the conventionally manufactured
Fe-Cr-AI alloy of the same thickness (comparison example 1) and has a signifi-
cantly better oxidation resistance than the alloy according to example D. After

400 h, the alloy according to example C has increased 2,3 % in weight, while
the alloy according to example D increased 5 % in weight. After the same time,
comparison example 1 has increased approx. 2,2 % in weight.
The alloy according to Example C was oxidation tested at 1100 oC together with
comparison example 1, which is shown in Figure 3. The two materials were
tested in the form of foil of a thickness of 50 µm. After up to 300 h of test time,
the two materials are equally good. After 400 h of testing, both the alloy
according to Example C and comparison example 1 have increased less than
6 % in weight: the alloy according to example C by 5,9 % and comparison
example 1 by 4,3 %. Thus, the alloy according to Example C meets the
requirement of sufficient oxidation resistance for use in catalytic converters,
maximum 6 % increase in weight in 50 µm thickness upon oxidation in 400 h at
1100°C.
Example 4
Examples E and F are the alloys according to examples C and D, respectively,
that have been annealed at 1200 °C for 20 min with the purpose of providing an
equalising of the Al content in the material (see table 4). The ductility of the
material was assessed by means of a bending test where the smallest bending
radius that the material could be bent to without fracturing was determined (see
table 4). The narrowest radius that the material was tested at was 0,38 mm.
None of the materials exhibited any damage after this bending. The radius is
smaller than the one used in the production of catalytic converters. Thereby,
strips manufactured according to the invention have a fully sufficient ductility to
allow the use thereof in catalytic converters. At 900 °C, example E has an ulti-
mate strength of 166 MPa (see table 2), which is more than four times larger
than the material according to comparison example 1 used at present, and fur-
thermore somewhat higher than a conventionally manufactured material
according to comparison example 2, having a similar composition as alloys that
have been manufactured in accordance with the invention.



Example 5
The alloys according to Examples E and F were oxidation tested at 1100 °C
together with the alloy of Example C according to the invention as well as com-
parison examples 1 and 2. The results are shown in Figure 4. Comparison
example 2 was tested in the form of an approx. 3 mm thick plate while Exam-
ples C, E and F were tested in the form of 50 µm thin foil. The alloy in compari-
son example 1 was tested in two different states: in the form of an approx. 3
mm thick plate extracted from a hot-rolled strip, as well as in the form of a foil of
a thickness of 50 urn. The results are summarized in table 5.
It is evident from Figure 4 and table 5 that the oxidation rate of the thin foil of
comparison example 1 is smaller than that of the thick plate. This effect may be
explained by the fact that the thin foil easily can be deformed and thereby
absorb the difference in thermal expansion between the protective oxide and
the metal. Thereby, it is avoided that the oxide fractures upon cooling and
heating, an effect that otherwise means that unprotected metal being exposed
to oxidation. The relatively thick plate cannot be deformed in the same way, and
that sample will thereby be more sensitive to heating and cooling.


The alloys according to Examples C and E have almost the same composition
as the alloy in comparison example 2, and also here, a similar effect of different
sample thickness would be expected, as for comparison example 1. However,
the relative improvement in oxidation resistance with decreasing sample thick-
ness of the alloy according to the invention is considerably larger than it is of
comparison example 1 (see table 5). This may be regarded to be a highly unex-
pected and valuable effect of the method according to the invention.
Furthermore, the diffusion annealing that differs between Examples C and E
has turned out to give an unexpectedly large additional improvement of the oxi-
dation resistance (see table 5).
To start with, the alloy according to Example F has equally good oxidation
resistance as Example C or comparison example 1 in the form of foil. Testing
was interrupted after 220 h for the alloy according to Example F. However,
comparison between the increase in weight up to 220 h at 1100 °C of examples

E and F shows that the alloy according to Example E has the most suitable
combination of composition and way of production as regards oxidation resis-
tance.
Example 6
A 50 µm thick strip of the alloy according to example A was coated with Al by
means of vaporization. Various samples were annealed for different times at
1050 °C in Ar gas. Concentration profiles of Al in the material were determined
by GDOES. The results are shown in figure 5. It is clear that an Al enriched
area is left near the surface of the strip also after 8 h of heat treatment. This
area seems only to be consumed slowly by Al diffusion inwardly in the strip.
Example 7
A 50 urn thick strip of the alloy according to example A was coated with Al by
means of vaporization. A sample was annealed for 50 min at 1150 °C in Ar gas.
The micro structure was analysed by means of SEM (scanning electron micro-
scopy). Figure 6 shows the area closest to the sample surface. Farthest out, a
Fe-Cr rich layer (cf. "0" in figure 6) is formed, inside this, a Ni and Al enriched
area (cf. "1" in figure 6). Layer "2" corresponds to a diffusion zone of slowly
decreasing Al content with increasing distance from the surface. In layer "3" in
figure 6, the composition is the same as in the substrate material.
Examples of application
Supporting material for catalytic conversion
Catalytic conversion is since a number of years a requirement in most industri-
alised countries. The catalytically active material is carried mechanically by a
supporting material. The requirements on the supporting material are, among
other things, that it should have a large surface, withstand temperature varia-


tions and have sufficient mechanical strength and oxidation resistance at the
operating temperature of the catalytic converter.
Two main types of supporting materials are used today: ceramic and metallic.
The ceramic supporting materials, which frequently are manufactured from
cordierit, are not affected by oxidation, however their brittleness means that the
resistance to impacts and other mechanical stresses as well as to temperature
variations such as fast changes of temperature is very limited. Today, metallic
supporting materials generally are based on thin strips of ferritic Fe-Cr-AI alloys
with additions of small amounts of reactive elements such as rare earth metals
(REM) or Zr or Hf. In order to give the monolith a maximum active surface, the
supporting material should be as thin as possible, usually between 10 µm and
200 pm. Today, a common strip thickness is 50 µm, but considerably enhanced
efficiency of the catalytic converter by virtue of an increased surface/volume-
ratio and/or decreased fall of pressure over the catalytic converter can be
expected upon a reduction of the strip thickness to 30 µm or 20 µm. The high
ductility of the metal gives a good resistance to mechanical and thermal fatigue.
Aluminium in contents above approx. 4,5 % by weight gives, together with the
reactive elements, the material the possibility of forming a thin, protective, alu-
minium oxide upon heating. Furthermore, the reactive elements make the oxide
getting a considerably reduced tendency to peel, i.e., come loose from the
metal upon cooling or mechanical deformation. However, conventional Fe-Cr-AI
alloys have a large disadvantage: they are mechanically very weak at high tem-
peratures, and therefore tend to be greatly deformed also upon small stresses
by virtue of, e.g., acceleration, changes of pressure, mechanical impacts or
changes of temperature.
The invention is not limited to products in small dimensions, such as thin strips
or thin wire. Since an austenrtic material having a content of aluminium that is
larger than 4,5 % by weight cannot be produced with sufficient productivity and
material yield by hot working, it is valuable to be able to manufacture such an
alloy in thicker dimensions by the coating method described in the present


invention. This may be effected, e.g., by manufacturing a product in the form of,
e.g., sheet-metal plate, strip, foil or a seamless tube, in a substrate alloy, and
then said product is coated, on one or both surfaces with an aluminium alloy in
such an amount that the total content of aluminium of the material exceeds 4,5
% by weight. For instance, a seamless tube having the composition according
to example A may be manufactured by means of conventional methods to the
following dimensions: outer diameter 60,33 mm, wall thickness 3,91 mm. In
order to be able to achieve a total content of aluminium of at least 4,5 % by
weight in such a tube, it needs to be coated with aluminium on the inner and
outer surface with a thickness of at least 0,1 mm. Such an amount may be
applied to the surfaces of the tube by conventional methods, e.g., by dipping in
a melt of an aluminium alloy. If a homogeneous material is desired, a longer
heat treatment at high temperature is required, suitably at least 1000 °C.
Therefore, the finished product should suitably be manufactured in a partly
homogenized form, where the material has an aluminium gradient that
increases towards the surfaces, e.g., by a heat treatment where the material
slowly is heated to 1100 °C and is heat-treated at this temperature for between
5 min and 10 h, depending on the desired aluminium distribution. It is evident to
a person skilled in the art that, if this product should be possible to be manu-
factured with satisfactory productivity, the content of aluminium in the substrate
material should be as high as possible, without causing production disturbances
in the manufacture of the substrate. In this case, a suitable content of aluminium
in the substrate material is 2-4 % by weight. This method can be used to
manufacture a finished product or to manufacture a starting material for contin-
ued plastic machining at low temperature, e.g., a tubular blank for pilgrim step
rolling.
Resistive heating
In industrial furnaces and in consumer goods including resistive heating, such
as hotplates, radiant heaters, flat irons, ovens, toasters, hairdryers, tumble-dry-
ers, drying cupboards, electric kettles, car seat heaters, underfloor heating


equipment, radiators and other similar products, there is also a need for using
strip, wire or foil having the above-described properties. Availability of a material
having this product specification results in the development of more efficient
heat sources having longer service life and/or higher operation temperature and
efficiency.
Further applications
The alloy produced according to the invention may also be used in other high
temperature applications, such as applications requiring a high oxidation
resistance and good mechanical properties. For example, it could be used in
heat exchangers or as protective plates. Also, it could be used in other
environments such as in reducing atmosphere. In this latter case it could be
advantageous in some cases to pre-oxidise the product before use in order to
assure a stable and dense Al-containing oxide on the surface.


We Claim :
1. Method to produce an austenitic alloy with an Al content of 4.5-12 wt% preferably 5.5 -
12 wt% wherein an austenitic substrate alloy of low Al content is coated, at a substrate
temperature of between 100 and 600 °C, with at least one layer of aluminum or aluminum
alloy with an Al content higher than the Al content of the substrate.
2. Method to produce an austenitic alloy according to claim 1, wherein the substrate has the
following composition (in % by weight):
20 - 70 % of Ni
15-27% of Cr
0-5% of AI
0-4%of Mo and/orW
0 - 2 % of Si
0 - 3 % of Mn
0 - 2 % of Nb
0 - 0.5 % of Y,Zr and/or Hf
0-0.5% of Ti
0-0.1 % of one or more rare earth metals (REM)
balance Fe and normally occurring impurities.
3. Method for the manufacture of an austenitic alloy according to any one of claims
1-2 in which the aluminum-based alloy is Al having 0,5 to 25 % by weight of Si.
4. Method for the manufacture of an austenitic alloy according to any one of claims
1-3, wherein the austenitic final product has the following composition (in % by weight)
0 - 0.2 % of C
0-0.1 % of N
25 - 70 % of Ni
15-25% of Cr
4.5-12% of Al
0-4% of Mo and/or W
0-4% of Si
0 - 3 % of Mn
0 - 2 % of Nb
0 - 0.5 % of Ti
0 - 0.5 % of Y, Sc, Zr and/or Hf

0 - 0.2 % of one or more rare earth metals (REM) such as, e.g., Ce, La,
Sm
balance Fe and normally occurring impurities.
5. Austenitic alloy with an Al content of 4.5 - 12 wt%, wherein the alloy is mufacturable
by the method according to any one of claims 1 -4.
6. The method according to any of claims 1-4 for producing material to be used in high
temperature applications such as supporting material in catalytic converters and
resistive heating.


The present invention relates to a method to produce an
austenitic stainless substrate alloy of low Al content being
coated with an alloy of higher Al content at a temperature
between 100°C and 600°C, so that the resulting product has an Al
content of 4,5-12% by weight.

Documents:

02120-kolnp-2006 abstract.pdf

02120-kolnp-2006 assignment.pdf

02120-kolnp-2006 claims.pdf

02120-kolnp-2006 correspondence others.pdf

02120-kolnp-2006 description(complete).pdf

02120-kolnp-2006 drawings.pdf

02120-kolnp-2006 form-1.pdf

02120-kolnp-2006 form-2.pdf

02120-kolnp-2006 form-3.pdf

02120-kolnp-2006 form-5.pdf

02120-kolnp-2006 international publication.pdf

02120-kolnp-2006 international search authority report.pdf

02120-kolnp-2006 pct form.pdf

02120-kolnp-2006-correspondence 1.3.pdf

02120-kolnp-2006-correspondence others-1.1.pdf

02120-kolnp-2006-correspondence-1.2.pdf

02120-kolnp-2006-form-1-1.1.pdf

2120-KOLNP-2006-ABSTRACT.pdf

2120-KOLNP-2006-CANCELLED PAGES.pdf

2120-KOLNP-2006-CLAIMS.pdf

2120-KOLNP-2006-CORRESPONDENCE 1.1.pdf

2120-KOLNP-2006-CORRESPONDENCE OTHERS 1.4.pdf

2120-KOLNP-2006-CORRESPONDENCE OTHERS 1.5.pdf

2120-KOLNP-2006-CORRESPONDENCE-1.4.pdf

2120-KOLNP-2006-CORRESPONDENCE-1.5.pdf

2120-KOLNP-2006-CORRESPONDENCE.pdf

2120-KOLNP-2006-DESCRIPTION (COMPLETE).pdf

2120-KOLNP-2006-DRAWINGS.pdf

2120-KOLNP-2006-EXAMINATION REPORT.pdf

2120-KOLNP-2006-FORM 1.pdf

2120-KOLNP-2006-FORM 18.pdf

2120-KOLNP-2006-FORM 2.pdf

2120-KOLNP-2006-FORM 3.1.pdf

2120-KOLNP-2006-FORM 3.pdf

2120-KOLNP-2006-FORM 5.pdf

2120-KOLNP-2006-GRANTED-ABSTRACT.pdf

2120-KOLNP-2006-GRANTED-CLAIMS.pdf

2120-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

2120-KOLNP-2006-GRANTED-DRAWINGS.pdf

2120-KOLNP-2006-GRANTED-FORM 1.pdf

2120-KOLNP-2006-GRANTED-FORM 2.pdf

2120-KOLNP-2006-GRANTED-SPECIFICATION.pdf

2120-KOLNP-2006-OTHERS.pdf

2120-KOLNP-2006-PA.pdf

2120-KOLNP-2006-REPLY TO EXAMINATION REPORT.pdf

2120-KOLNP-2006-REPLY TO EXAMINATION REPORT1.1.pdf

2120-KOLNP-2006-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

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Patent Number 250106
Indian Patent Application Number 2120/KOLNP/2006
PG Journal Number 49/2011
Publication Date 09-Dec-2011
Grant Date 07-Dec-2011
Date of Filing 27-Jul-2006
Name of Patentee SANDVIK INTELLECTUAL PROPERTY AB
Applicant Address S-811 81 SANDVIKEN, SWEDEN
Inventors:
# Inventor's Name Inventor's Address
1 WITT EVA SALGGATAN 7, S-811 62 SANDVIKEN
2 ROSBERG ANDREAS VIKINGAVAGEN 32, S-811 60 SANDVIKEN
3 GORANSSON, KENNETH S KANSLIGATAN 28, 6TR, S-802 52 GAVLE
PCT International Classification Number C22C 38/40
PCT International Application Number PCT/SE2004/002017
PCT International Filing date 2004-12-15
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 0303608-4 2003-12-30 Sweden