KR20070000503A - Iron chrome aluminum alloy - Google Patents

Abstract

The invention relates to an iron-chrome-aluminum alloy with a high service life, comprising (in mass %) 4 to 8 % Al and 16 to 24 % Cr and other added materials, 0.05 to 1 % Si, 0.001 to 0.5 % Mn, 0.02 to 0.2 % Y, 0.1 to 0.3 % Zr and/or 0.02 to 0.2 % Hf, 0.003 to 0.05 % C, 0.0002 to 0. 05 % Mg, 0.0002 to 0.05 % Ca, max. 0.04 % N, max. 0.04 % P, max. 0.01 % S, max. 0.5 % Cu and the usual melting-related impurities, the remainder being iron. ® KIPO & WIPO 2007

Description

Iron chrome aluminum alloy

The present invention relates to an iron chromium aluminum alloy produced by metallurgic melting and having a long service life.

Such alloys are used to make electrical heating elements and catalyst carriers. These materials form a dense, high-adhesion aluminum oxide film to prevent breakage at high temperatures (eg 1400 ° C. or higher). This breakdown prevention is particularly enhanced by the addition of so-called reactive elements such as Ca, Ce, La, Y, Zr, Hf, Ti, Nb, W, which increase the adhesion of the oxide film and / or reduce the film growth, for example For example, as described below in page 274 of "Ralf Burgel, Handbuch der Hochtemperatur-Werkstofftechnik, Vieweg-Verlag, Braunschweig 1998".

The aluminum oxide film prevents the material from oxidizing prematurely. Here, the aluminum oxide film grows on its own but grows very slowly. This growth consumes the aluminum content of the material. If no more aluminum is present, other oxides (chromium oxide and iron oxide) will grow, the metal content of the material will be consumed very quickly and the material will fail due to destructive corrosion. The period until breakdown is defined as the service life. Increasing the aluminum content increases the useful life.

WO 02/20197 is known in particular ferritic anticorrosion steel alloys used as thermal conductor elements. The alloy is formed from a FeCrAl alloy made by powder metallurgy, less than 0.02% (hereinafter% refers to mass%), less than 0.5% Si, less than 0.2% Mn, less than 10.0 to 40.0 % Cr, up to 0.6% Ni, up to 0.01% Cu, 2.0 to 10.0% Al, 0.1 to 1.0% Sc, Y, La, Ce, Ti, Zr, Hf, V, Nb, Ta It contains one or more elements selected from the group of reactive elements, the balance being unavoidable impurities and iron.

DE-A 199 28 842 has 16 to 22% (hereinafter% by mass) of Cr, 6 to 10% Al, and 0.02 to 1.0% Si, up to 0.5% Mn, 0.02 to 0.1% Hf, 0.02 to 0.1% Y, 0.001 to 0.01% Mg, up to 0.02% Ti, up to 0.03% Zr up to 0.02% rare earth metal, up to 0.1% Sr, up to 0.1% Ca, up to 0.5% Cu, up to 0.1% of V, up to 0.1% of Ta, up to 0.1% of Nb, up to 0.03% of C, up to 0.01% of N, up to 0.01% of B, with the remainder being impurities and iron produced during melting Alloys are described for use as carrier foils of exhaust gas catalysts, thermal conductors, in the manufacture of industrial furnaces and as components in gas ports.

EP-B 387 670 contains 20 to 25% (hereinafter% by mass) Cr, 5 to 8% aluminum, and 0.03 to 0.08% yttrium, 0.004 to 0.008% nitrogen, 0.020 to 0.040% carbon, At about the same rate, it contains 0.035 to 0.07% titanium, 0.035 to 0.07% zirconium, and up to 0.01% phosphorus, up to 0.01% magnesium, up to 0.5% manganese, up to 0.005% sulfur, the balance being An alloy of iron is described, wherein the total content of titanium and zirconium is 1.75 to 3.5% greater than the total content of carbon and nitrogen and the percentage of impurities produced during melting. Titanium and zirconium may be completely or partially replaced by hafnium and / or tantalum or vanadium.

EP-B 0 290 719 contains 12 to 30% chromium, 3.5 to 8% aluminum, 0.008 to 0.10% carbon, up to 0.8% silicon, 0.10 to 0.4% manganese, up to 0.035% phosphorus, up to 0.020% Sulfur, 0.1 to 1.0% molybdenum, at most 1% nickel, and 0.010 to 1.0% zirconium, 0.003 to 0.3% titanium and 0.003 to 0.3% nitrogen, 0.005 to 0.05% calcium and magnesium, and 0.003 to It contains 0.80% rare earth metals, 0.5% niobium additives, the remainder being described as alloys with common mixed elements and iron, which are, for example, the building materials of the heating device in the furnace and in the heat stressed part of the building material. And foils for the production of catalyst carriers.

US 4,277,374 contains up to 26% chromium, 1-8% aluminum, 0.02-2% hafnium, 0.3% or less yttrium, 0.1% or less carbon, 2% or less silicon, balance iron An alloy comprising is described, which preferably comprises 12 to 22% of chromium and 3 to 6% of aluminum and is used as a foil for producing a catalyst carrier.

US Pat. No. 4,414,023 contains 8.0 to 25.0% (hereinafter by mass) chromium, 3.0 to 8.0% aluminum, 0.002 to 0.06% rare earth metals, up to 4.0% silicon, 0.06 to 1.0% manganese, 0.035 to 0.07% Alloys containing titanium, 0.035 to 0.07% zirconium and unavoidable impurities are known.

Detailed models of the useful life of iron chromium aluminum alloys are described in I. Gurrappa, S. Weinbruch, D. Naumenko, W.J. See papers of pages 224-235 of Quadakkers, Materials and Corrosions 51 (2000). Here, a model has been presented indicating that the useful life of the iron chromium aluminum alloy depends on the aluminum content and the sample form, and possible sparging is not yet considered in the following formula.

Where

f = 2 x volume / surface area

t _B = useful life (defined as time until oxides other than aluminum oxide are formed)

C ₀ = aluminum concentration at the onset of oxidation

C _B = aluminum concentration when oxides other than aluminum oxide are formed

p = specific gravity of the metal alloy

k = oxidation rate constant

n = oxidation rate exponent

Considering cracks, the thickness d (f The following formula is generated for a flat sample of infinite width and length with d):

In the above formula, Δm ^* is the critical change in weight at which the crack starts.

This form indicates that the useful life decreases with decreasing aluminum content and a high ratio of surface area to volume (or small thickness of the sample). The impact of heat cycles is not considered in this paper, for example see J.P. Willber, MJ Bennett and JR Nicholls "The effect of thermal cycling on the mechanical failure of alumina scales formed on commercial FeCrAl-RE alloys, in Proc. Of Int. Conf. On Cyclic Oxidation of High Temperature Materials", february 1999, Frankfurt am Main, Germany, Editors M. Schutze and WJ Quadakkers, pp. 133-147 (1999) describe cycle times from 1 hour to 290 hours, where the cycle time will affect if cracks occur in this document.

V.K. Tolpygo, D. R. Clarks "Spalling failure of α-alumina films grown by oxidation: I. Dependence on cooling rate and metal thickness, Materials science and engineering", A278 pp. 142-150 (2000) also describes the effect of cycle time and cooling rate. Both papers show that, in particular, short heating periods, short cooling periods and only short residences at high temperatures greatly reduce the useful life.

In the following the term thermal cycle is defined as the sum of the heating time, the residence time at that temperature, the cooling time and the waiting time until the new heating. Thermal cycles that provide short heating times, short cooling times and only short residence times at high temperatures are referred to hereinafter as short and fast thermal cycles. Among these are, for example, thermal cycles in which the total length of time ranges from a few seconds to a few minutes, where the total length of time is the heating time, residence time at that temperature, cooling time and waiting until the next heating time starts. It means the sum of time.

Thermal conductors made from thin films (eg, from about 30 to 100 μm in thickness and from 1 to several mm in width) stand out as large surface area-to-volume ratios. It is advantageous if a high speed heating and cooling time is achieved, so that the high speed heating and cooling time can be seen to prematurely heat the thermal conductor used in the glass-ceramic cooking area, for example, similar to a gas cooker. This is because it is necessary to achieve a rapid temperature rise. At the same time, however, the large surface area-to-volume ratio is disadvantageous for the useful life of the thermal conductor (see above). In addition, the temperature should be limited to below the glass to prevent deterioration in such applications. This can also be accomplished by powering down the current repeatedly or for a short period of time. Both methods will burden the thermal conductor due to the short heating time and fast cooling and short residence time, which further reduces the useful life as described above.

In none of the documents mentioned above, the influence of thermal cycles is not particularly handled. That is, none of the above mentioned alloys has been developed in connection with this aspect.

It is known that in the above described situation of the art, even a small amount of Y, Zr, Ti, Hf, Ce, La, Nb, W can improve the useful life of the FeCrAl alloy.

J. Klower, Materials and Corrosion 51 (2000), pp. According to 373-385, the addition may not be too much, since otherwise faster oxidation rates will occur, which means an increase in the consumption of aluminum and thus a shortened useful life. The faster oxidation rate is caused, for example, by adding only 0.11% hafnium to the iron chromium aluminum alloy comprising 20% Cr, 7% aluminum and 0.01% yttrium. Other examples of faster oxidation rates with the addition of too many reactive elements as described in the paper include 18.8% Cr, 7% Al, and 0.11% Y added iron chromium aluminum alloy, or 20% It is an iron chromium aluminum alloy containing Cr, 7% Al, and added 0.04% Y, 0.05% Zr and 0.05% Ti. Here, the range of faster oxidation rates caused by the excessive addition of reactive elements depends on the aluminum content. J. Klower, Materials and Corrosion 51 (2000), pp. According to 373-385, 0.04% Zr already causes an increase in the oxidation rate in iron chromium aluminum alloys containing 20% Cr, 7% Al and 0.05% Y. However, iron chromium aluminum alloys containing 20% Cr, 5.5% Al and 0.05% Y, 0.05% Hf (J. Klower, A. Kolb-Telieps, M. Brede: in Bode, H. (Ed In metal-supported automotive catalytic converters, DGM Informationsgesellschaft, Oberursel, 1997, pages 33 and below, the same amount of Zr does not lead to an increase in oxidation rate. J. Klower, Materials and Corrosion 51 (2000), pp. All tests under 373-385 and J. Klower, A. Kolb-Telieps, M. Brede: in Bode, H. (Ed.) Metal-Supported Automotive Catalytic Converters, DGM Informationsgesellschaft, Oberursel, 1997, pages 33 It was carried out in a cycle of 100 hours or 96 hours in the furnace, which is a very long cycle.

It is an object of the present invention to provide an iron chromium aluminum alloy for elements having a longer useful life than ever used iron chromium aluminum alloys, in particular for large surface area-to-volume ratios or small band thicknesses.

The object is produced by metallurgical melting and has a long useful life, 4-8% (hereinafter by mass) aluminum, 16-24% chromium, and 0.05-1% Si, up to 0.5% Mn, 0.02 to 02% yttrium and 0.1 to 0.3% Zr and / or 0.02 to 0.2% Hf, 0.003 to 0.05% C, 0.0002 to 0.05% Mg, 0.0002 to 0.05% Ca, up to 0.04% N, Up to 0.04% P, up to 0.01% S, up to 0.5% Cu and additives of conventional impurities produced during the melting process, the balance being achieved by the iron chromium aluminum alloy being iron.

Advantageous embodiments of the alloy according to the invention are disclosed in the following claims.

In addition, the Hf element may be completely or partially replaced by at least one of Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium elements, where 0.02 to 0.15 mass Partial substitution of ranges between% is possible.

Advantageously, the alloy according to the invention may be a melt of up to 0.02% (mass%) of N, up to 0.02% of P and up to 0.005% of S.

In the state of the art according to Corrosion 51 (2000) and DGM Informationsgesellschaft, all tests were carried out in a furnace of 100 hours or 96 hours, which is a very long cycle time.

Surprisingly, in tests with very short cycles, it has been found that the range of shortened useful life (which at the same time, means increased oxidation rate) is completely different. Thus, the iron chromium aluminum alloy according to the invention, which is according to J. Klower, Materials and Corrosion 51 (2000), pp. 373-385, 1% Zr, at least 0.02% during the cycle of 100 hours or 96 hours in the furnace. Already exhibited an increased oxidation rate for Y and thus a shortened useful life), a 2 minute “on” and 15 minutes in the life test of the wire with a small surface area-to-volume ratio. In a short cycle of seconds "off", the alloy exhibits a useful life at the upper end of the range of variation of the useful life of the alloy according to the state of the art. This difference is even more evident when a 50 μm thick film with a very large surface area-to-volume ratio and very short cycles of 15 seconds “live” and 5 seconds “shut off” is used in the useful life test.

Preferred FeCrAl alloys stand out with respect to the following composition (mass%).

Al 5-6% 5-6%

Cr 18-22% 18-22%

Si 0.05-0.7% 0.05-0.7%

Mn 0.001-0.4% 0.001-0.4%

Y 0.03-0.1% 0.03-0.1%

Zr 0.15-0.25%

Hf 0.02-0.15% 0.02-0.15%

C 0.003-0.03% 0.003-0.03%

Mg 0.0002-0.03% 0.0002-0.03%

Ca 0.0002-0.03% 0.0002-0.03%

N up to 0.04% up to 0.04%

P up to 0.04% up to 0.04%

S up to 0.01% up to 0.01%

Cu up to 0.5% up to 0.5%

In each application case, the range of the following element ranges can be defined as follows:

Hf 0.03-0.11%

C 0.003-0.025%

Mg 0.0002-0.01%

Ca 0.0002-0.01%

The alloy according to the invention can preferably be used in electric heating elements having a short heating and cooling period, a short residence time at that temperature and a short waiting time until the start of a new heating period.

The alloys according to the invention can also be used in heating elements that require good dimensional stability or small sagging.

The alloy according to the invention can also be used in thermal conductors made of membranes with a thickness of 20 to 100 μm.

It is also possible to use in thermal conductor alloys used in cooking places.

Finally, it is also possible to use the alloy according to the invention for the production of furnaces.

Other preferred alloy elements that can be used are disclosed in the corresponding claims.

The details and advantages of the invention are set forth in detail in the following examples.

Table 1 shows the molten iron chromium aluminum alloys L1 to L8 and E1 to E2, and molten alloys G1 to G3 on a large industrial scale. Wire and 50 μm thick films from molten alloys in the laboratory were made from materials cast into ingots by warm and cold rolling and suitable intermediate annealing. The film was cut into strips having a width of 6 mm. For industrial molten alloys, 50 μm thick strip samples were taken from industrial production and cut to have a suitable width of about 6 mm as needed.

For thermal conductors in the form of wires, accelerated useful life tests are possible, for example, according to the following conditions, which are commonly used to contrast materials with one another.

The useful life test of the thermal conductor was carried out with a wire coil having a diameter of 0.40 mm, 12 turns, a coil diameter of 4 mm and a coil length of 50 mm. The wire coil was fixed between two current supplies and heated to 1200 ° C. with electromotive force applied. Heating up to 1200 ° C. was carried out for 2 minutes each and current supply was interrupted for 15 seconds. At the end of its useful life, the wire broke and the remaining cross section melted completely.

Similar useful life tests can be performed with film strips. Here, a film strip having a thickness of 50 μm and a width of 6 mm was fixed between two current supplies and energized and heated to 1050 ° C. Heating up to 1050 ° C. was carried out for 15 seconds each and current supply was stopped for 15 seconds. At the end of its useful life the film broke and the remaining cross section melted completely.

The useful life in both tests is the total time without downtime the wire or film is at the temperature. During the useful life test the temperature was measured with an optical pyrometer and corrected to nominal temperature if necessary.

The effective life test results are shown in Table 1. The mean values shown in the table are the mean values of at least three samples each.

In the useful life test of the wire, the coil was initially fixed horizontally. The coil began to sag during the useful life test. The smaller the sag, the greater the dimensional stability of the material. High dimensional stability is an advantageous technical property because it means that the shape deformation is small when parts made from this material are maintained at high temperatures.

The industrially molten alloys G1 and G2, and the laboratory molten alloy L2 are about 20% Cr, about 5% Al, and 0.04 to 0.07% Y, as shown in Table 1 according to the state of the art. 0.04 to 0.07% of Zr and 0.04 to 0.05% of Ti, additives of 0.033 to 0.037% carbon content, 0.15 to 0.34% Si content, about 0.24% Mn content and N, S, Ce, La, It contains a small amount of Pr, Ne, P, Mg and Ca. Made from L2, the useful life in cycles of "energizing" for 120 seconds and "singing off" for 15 seconds at 1200 ° C. of a wire having a thickness of 0.4 mm is provided as a reference, which is expressed as 100%.

The useful life in the cycle of "energizing" for 15 seconds and "singing off" for 5 seconds of a 50 μm thick film ranges from 102 to 124% of the effective life of the laboratory batch L1. The industrially molten alloy G3 also contains about 20% Cr, about 5% Al, 0.06% Y, 0.04% Zr, 0.02% as shown in Table 1 according to the state of the art. Hf is added to represent an iron chromium aluminum alloy containing 0.029% carbon content, 0.28% Si content, 0.20% Mn content and small amounts of P, Mg, Ca. The useful life in a cycle of "energizing" for 15 seconds and "singing off" for 5 seconds of a 50 μm thick film is 148% of the effective life of the laboratory batch L1. Thus, the alloy according to the state of the art has a value of about 100 to about 150% of L1 in an effective life test in a cycle of "energy" for 15 seconds and "disconnected" for 5 seconds at 1050 ° C. of a 50 μm thick film. Indicates.

The contents of Si, C, Zr and Hf were varied in the laboratory batches L1 and L3 to L8. The content of Mn was unchanged and included 0.24 to 0.28% in all laboratory melts, and small amounts of P, Mg, Ca, Ce, La, Pr, Ne were shown in Table 1. Wherein variant L1 comprising 0.03% Y, 0.04% Zr and 0.02% Hf, with a carbon content of 0.007% and a Si content of 0.35%, was used for 120 seconds at 1200 ° C. of a 0.4 mm thick wire. Life expectancy test in a cycle of "power on" and "single power" for 15 seconds, showing a relatively long useful life of 116%. Variants L3 and L7 with only 0.06% or 0.05% of Y added and with a carbon content of 0.002% or 0.031% and a Si content of 0.34% or 0.35% have an effective lifespan of only 41% or 51% in the life test of the wire. Indicates. Variants L4 and L5 having a Y content of 0.04% or 0.05% and a Zr content of 0.05% or 0.014%, a carbon content of 0.002% or 0.003% and a Si content of 0.33% or 0.35% are 79% or 86 It has a% useful life, which is better than the useful life of L3 and L7 but less than the useful life of L2 or L1. Variant L6 with 0.05% Y added and 0.05% Hf added, 0.010% carbon content and 0.36% Si content, has an effective lifespan of 85%, which is also better than the useful life of L3 and L7, but L2. Or does not reach the useful life of L1. The experimental batch L8 contains 0.05% Y, 0.21% Zr and 0.11% Ti, and 0.018% carbon content and only 0.02% Si content. Thus, J. Klower, Materials and Corrosion 51 (2000) pp. According to 373-385, the alloy is already included in the concentration zone with high oxidation rate in the service life test in the furnace, for example at long cycles of 100 hours or 96 hours, due to the high Zr and Ti content. Nevertheless, the alloy exhibits a 105% useful life in the thermal conductor useful life test of the wire, meaning that the alloy is located between L1 and L2.

Alloy E1 comprising 0.05% Y, 0.18% Zr, 0.04% Hf, 0.006% C and 0.35% Si, and 0.03% Y, 0.20% Zr, Hf instead of 0.11% Alloy E2 comprising Ti, 0.020% C and 0.61% Si is included in the higher oxidation rate range in the service life test, for example in long cycles of 100 hours or 96 hours in a furnace. Both alloys have a long useful life of 96% for E2 and 118% for E1 in the thermal conductor life test of the wire. Thus, the order of shelf life for laboratory melts (each classified according to decreasing shelf life) is as follows:

Top group : E1, L1, L8, L2, E2, characterized in that Y and Zr were added, and also Ti or Hf was added.

Medium useful life : L5, L6, L4 characterized by the addition of Y and Zr or Y and Hf

Short service life : L7 and L3, characterized by the addition of only Y

This corresponds to knowledge and experience of state of the art. Alloy L2, for example, corresponds to alloys G1 and G2 industrially melted according to the state of the art.

The thermal conductor useful life test in a cycle of "energizing" for 15 seconds and "singing off" for 5 seconds of a 50 μm thick film differs in aspect: in the wire test alloys L3 and L7 exhibiting a short useful life are L1. 94 and 110% of the useful life, which fall within the useful life of the alloy according to the state of the art. Alloys L5, L6, L4, which exhibited an intermediate useful life in the wire test, exhibited an effective life of 145% or 113% of the useful life of L1, which is also included in the useful life range of the alloy according to the state of the art. In the wire test, alloys L1 and L2 belonging to the highest group represent 100% or 125% of the useful life of L1 and alloy L8 represents 140% of the useful life of L1, which is merely an alloy's useful life range according to the state of the art. Included in

Surprisingly, the alloys E1 and E2 according to the invention, which fall within the higher oxidation rate range in a long service life test, for example in a long cycle of 100 hours or 96 hours, have a very long effectiveness of 256% for E1. It is a very good figure in relation to all other values, and in the case of E2 it is 171% which is clearly greater than the useful life range of the alloy according to the state of the art. Likewise surprisingly, alloy E3 of the invention comprising 0.05% Y, 0.21% Zr, 0.021% C and 0.19% Si, 201% Y, 0.07% Y, 0.23% Zr, 0.07% Ti, Comprises 0.014% C and 0.19% Si, alloy E4 of the invention having 227%, 0.07% Y, 0.22% Zr, 0.07% Hf, 0.018% C and 0.20% Si , Alloy E5 of the present invention having 249%, 0.05% Y, 0.17% Zr, 0.05% Hf, 0.016% C and 0.19% Si, and alloy E6 of the present invention having 283% Indicates the useful life.

Thus, the ranking result is as follows:

Best group with a useful life longer than 170% of L1 : Y and Zr and / or Hf and / or Ti with higher oxidation rate ranges in the service life test, for example in long cycles of 100 hours or 96 hours in a furnace E1 to E6, characterized in that added, having a carbon content of 0.003 to 0.025% and a Si content of more than 0.05%.

Group having an effective lifetime of about 100% to 150% of L1, corresponding to the state of the art : Y outside the higher oxidation rate range in the useful life test in a long cycle, for example 100 hours or 96 hours in a furnace. And a smaller amount of Zr and / or Hf and / or Ti, and in the case of L8, Y, Zr and Hf were added in a higher oxidation rate range and G3 characterized by a very low Si content. , L5, L8, L2, G2, L4, L6, G1, L1, L7, L3.

Regarding the dimensional stability, which is important in use and measured the slack of the coil after the heating time of 50 hours in mm, the alloys E1, E2 and L8 of the present invention exhibit values of 5 to 7 mm, and therefore values of 17 to 19 mm. It belongs to the highest group in comparison with other alloys L1 to L7 according to the state of the art. Thus, the alloy according to the invention also offers the advantage of high dimensional stability.

Accordingly, the claimed limits of the invention may be justified in detail as follows.

In order to maintain the effect of Y on improving oxidative stability, a minimum content of Y of 0.02% is required. The upper limit is set at 0.2 mass% for cost reasons.

Zr with a minimum content of 0.1% is required to reach the high useful life range in short and fast temperature cycles. The upper limit is set at 0.3 mass% for cost reasons.

In order to maintain the effect of Hf on improving oxidation stability, Hf with a minimum content of 0.02% is required. The upper limit is set at 0.2 mass% for cost reasons.

In order to maintain the effect of Ti to improve oxidation stability, Ti with a minimum content of 0.02% is required. The upper limit is set at 0.2 mass% for cost reasons.

The carbon content should be 0.003% to 0.05% to ensure workability.

The nitrogen content should be at most 0.04% to prevent the formation of nitrogen compounds which degrade workability.

The content of phosphorus and sulfur should be kept as low as possible because these surface reactive elements negatively affect oxidative stability. Therefore, it is set as P of 0.04% at maximum and S of 0.01% at maximum.

The chromium content comprised between 16 and 24 mass% does not have a decisive effect on the useful life, as J. Klower, Materials and Corrosion 51 (2000), pp. As described in 373-385. However, a constant chromium content is necessary because chromium promotes the formation of particularly stable and protective α-Al ₂ O ₃ membranes. This is secured at about 16% or higher. Therefore, the lower limit is 16%. If the chromium content exceeds 24%, the workability of the alloy is reduced.

The aluminum content of the alloy according to the invention should be comprised between 4 and 8%. According to Figure 5.13, page 272 of “Handbuch der Hochtemperatur-Werkstofftechnik, Ralf Burgel, Vieweg Verlag, Braunschweig 1998”, about 4% of aluminum is required to form a closed α-Al ₂ O ₃ film. Aluminum content higher than 8% degrades workability.

J. Klower, Materials and Corrosion 51 (2000), pp. According to 373-385, the addition of silicon improves the useful life by improving the adhesion of the cover layer. Therefore, silicon with a minimum content of 0.05% by mass is required. Too much silicon adversely affects the workability of the alloy. Therefore, the upper limit is 1%.

Manganese is limited to 0.5% by mass because manganese elements reduce oxidative stability. The same applies to copper.

The contents of magnesium and calcium are set in the range of 0.0002 to 0.05 mass%.

Claims (19)

4-8% (mass%) Al and 16-24% Cr, 0.05-1% Si, 0.001-0.5% Mn, 0.02-0.2% Y, 0.1-0.3% Zr and / or 0.02 To 0.2% Hf, 0.003 to 0.05% C, 0.0002 to 0.05% Mg, 0.0002 to 0.05% Ca, up to 0.04% N, up to 0.04% P, up to 0.01% S, up to 0.5% Cu Long lifespan chromium aluminum alloy containing additives and common impurities produced during the melting process, the balance being iron. 5 to 6% (mass%) of Al, 18 to 22% of Cr, 0.05 to 0.7% of Si, 0.001 to 0.4% of Mn, 0.03 to 0.1% of Y, 0.15 to 0.25% Zr and / or 0.02 to 0.15% Hf, 0.003 to 0.03% C, 0.0002 to 0.031% Mg, 0.0002 to 0.03% Ca, up to 0.04% N, up to 0.04% P, up to 0.01% S Iron chromium aluminum alloy containing up to 0.5% of Cu additives and conventional impurities produced in the melting process, the balance being iron. The method of claim 1, wherein 5 to 6% (mass%) of Al, 18 to 22% of Cr, 0.05 to 0.7% of Si, 0.001 to 0.4% of Mn, 0.03 to 0.08% of Y, 0.15 to 0.25% Zr and / or 0.03 to 0.11% Hf, 0.003 to 0.025% C, 0.0002 to 0.01% Mg, 0.0002 to 0.01% Ca, up to 0.04% N, up to 0.04% P, up to An iron chromium aluminum alloy comprising 0.01% of S, up to 0.5% of Cu and conventional impurities produced in the melting process, the balance being iron. The method according to any one of claims 1 to 3, wherein 5 to 6% (mass%) of Al, 18 to 22% of Cr, and 0.05 to 0.7% of Si, 0.001 to 0.4% of Mn, 0.03 to 0.08. % Y, 0.15 to 0.25% Zr and / or 0.03 to 0.08% Hf, 0.003 to 0.025% C, 0.002 to 0.01% Mg, 0.0002 to 0.01% Ca, up to 0.04% N, up to 0.04% Iron chromium aluminum alloy containing P, up to 0.01% of S, up to 0.5% of Cu, and common impurities produced during melting, the balance being iron. The method according to any one of claims 1 to 4, wherein Hf is completely replaced by at least one of Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium elements. Iron chromium aluminum alloy, characterized in that. 5. The method according to claim 1, wherein Hf is 0.01 to 0.18% of at least one of Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium elements. Iron chromium aluminum alloy, characterized in that partly replaced by mass%). The method according to any one of claims 1 to 6, wherein Hf is 0.02 to 0.15% of Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium elements ( Iron chromium aluminum alloy, characterized in that partly replaced by mass%). The method according to claim 6 or 7, wherein Hf is at least 0.02 to 0.11% (mass%) of Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium elements. Iron chromium aluminum alloy, characterized in that partly or completely replaced. The method according to claim 6 or 7, wherein Hf is at least 0.03 to 0.07% (mass%) of Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium elements. Iron chromium aluminum alloy, characterized in that partly or completely replaced. The iron chromium aluminum alloy according to claim 1 comprising at most 0.02% (% by mass) of N, at most 0.02% of P and at most 0.005% of S. 11. The iron chromium aluminum alloy according to claim 1 comprising at most 0.01% (mass%) of N, at most 0.02% of P and at most 0.003% of S. 12. The iron chromium aluminum alloy according to claim 1, comprising at most 0.1% (mass%) of Mo and / or 0.1% of W. 13. Use of the iron chromium aluminum alloy according to any one of claims 1 to 12 as an alloy for use in an electric heating element. Iron chromium according to any one of claims 1 to 12 as an alloy for use in an electric heating element having a short heating and cooling period, a short residence time at that temperature and a short waiting time until the start of a new heating period. Use of aluminum alloys. Use of the iron chromium aluminum alloy according to any one of claims 1 to 12 as an alloy for use in electric heating elements where high dimensional stability and low sagging are required. Use of the iron chromium aluminum alloy according to any one of claims 1 to 12 as an alloy for use in thermal conductors made from films having a thickness of 20 to 100 μm. Use of the iron chromium aluminum alloy according to any one of claims 1 to 12 as an alloy for use in thermal conductors made of wire having a diameter of less than 6 mm. Use of the iron chromium aluminum alloy according to any one of claims 1 to 12 as a thermal conductor alloy used in cooking zones, in particular glass-ceramic cooking zones. Use of the iron chromium aluminum alloy according to any one of claims 1 to 12 as a thermal conductor alloy used in the manufacture of a furnace.