DE102005016722A1 - Iron-chromium-aluminum alloy - Google Patents

Abstract

High-durability iron-chromium-aluminum alloy with (in mass%) 4 to 8% Al and 16 to 24% Cr and additions of 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 up to 0.05% Ca, max. 0.04% N, max. 0.04% P, max. 0.01% S, max. 0.5% Cu and the usual melting impurities, balance iron.

Description

The The invention relates to a melt-metallurgically produced iron-chromium-aluminum alloy with high durability.

such Alloys are used to make electrical heating elements and catalyst supports used. These materials form a dense, adherent alumina layer, they are from destruction at high temperatures (eg up to 1400 ° C) protects. This protection is improved by additions of so-called reactive elements such as Ca, Ce, La, Y, Zr, Hf, Ti, Nb, W, and the like. the adhesion of the Improve oxide layer and / or reduce layer growth, as in "Ralf Bürgel, manual High Temperature Materials Technology, Vieweg Verlag, Braunschweig 1998 "from page 274 is described.

The Aluminum oxide layer protects the metallic material from rapid oxidation. At the same time she is growing itself, albeit very slowly. This growth takes place under consumption the aluminum content of the material instead. Is not aluminum more present, so grow other oxides (chromium and iron oxides), the Metal content of the material is consumed very quickly and the Material fails due to destructive corrosion. The time to failure is defined as the lifetime. An increase in the Aluminum content extended the life.

By WO 02/20197 is a ferritic stainless steel alloy, in particular for use as heating element, known. The alloy is formed by a powder metallurgy produced FeCrAl alloy, including (in% by mass) less than 0.02% C, ≤ 0.5% Si, ≤ 0.2 Mn, 10: 0 to 40.0% Cr, ≤ 0.6% Ni, ≤ 0.01% Cu . 2.0 to 10.0% Al, one or more elements) from the group of the reactive elements, such as Sc, Y, La, Ce, Ti, Zr, Hf, V, Nb, Ta, in contents between 0,1 and 1,0%, remainder iron as well as unavoidable Impurities.

In DE-A 199 28 842 is an alloy with (in% by mass) 16 to 22% Cr, 6 to 10% Al and additions of 0.02 to 1.0% Si, max. 0.5 % Mn, 0.02 to 0.1% Hf, 0.02 to 0.1% Y, 0.001 to 0.01% Mg, Max. 0.02% Ti, max. 0.03% Zr, max. 0.02% SE, max. 0.1% Sr, max. 0.1% Ca, max. 0.5% Cu, max. 0.1% V, max. 0.1% Ta, max. 0.1% Nb, max. 0.03% C, max. 0.01% N, max. 0.01% B, balance iron as well melting-related contaminants for use as a carrier film for catalytic converters, as a heat conductor, as a component in industrial furnace construction and in gas burners described.

In EP-B 0 387 670 becomes an alloy with (in% by mass) 20 to 25 % Cr, 5 to 8% Al and additions of 0.03 to 0.08% yttrium, 0.004 to 0.008% nitrogen, 0.020 to 0.040% carbon, as well approximately equal parts 0.035 to 0.07% Ti and 0.035 to 0.07% zirconium, and max. 0.01% phosphorus, max. 0.01% magnesium, max. 0.5% manganese, Max. 0.005% sulfur, remainder iron, where the sum of the Content of Ti and Zr is 1.75 to 3.5% times as large as the percentage Sum of the contents of C and N as well as impurities caused by melting. Ti and Zr may be wholly or partially hafnium and / or tantalum or Vanadium be replaced.

In EP-B 0 290 719 becomes an alloy with (in% by mass) 12 to 30 % Cr, 3.5 to 8% Al, 0.008 to 0.10% carbon, max. 0.8% silicon, 0.10 to 0.4% manganese, max. 0.035% phosphorus, max. 0.020% sulfur, 0.1 to 1.0% molybdenum, Max. 1% nickel, and the additives 0.010 to 1.0% zirconium, 0.003 to 0.3% titanium and 0.003 to 0.3 % Nitrogen, calcium plus magnesium 0.005 to 0.05%, as well as rare Earth metals from 0.003 to 0.80%, niobium of 0.5%, balance iron with usual Accompanying elements described, for example, as a wire for heating elements for electric heated stoves and as a construction material for thermally stressed Parts and used as a film for the preparation of catalyst supports becomes.

In the US 4,277,374 is an alloy with (in mass%) up to 26% chromium, 1 to 8% aluminum, 0.02 to 2% hafnium, up to 0.3% yttrium, up to 0.1% carbon, up to 2% silicon , Rest of iron, with a preferred range of 12 to 22% chromium and 3 to 6% of aluminum, which is used as a film for the preparation of catalyst supports.

By US-A 4,414,023 is a steel having (in mass%) 8.0 to 25.0% Cr, 3.0 to 8.0% Al, 0.002 to 0.06% rare earth metals, max. 4.0 % Si, 0.06 to 1.0% Mn, 0.035 to 0.07% Ti, 0.035 to 0.07% Zr including become known unavoidable impurities.

t_B

= Lebensdauer, definiert als Zeit bis zum Auftreten anderer Oxide als Aluminiumoxid

C₀

= Aluminium-Konzentration am Beginn der Oxidation

C_B

= Aluminium-Konzentration bei Auftreten von anderen Oxiden als Aluminiumoxiden

ρ

= spezifische Dichte der metallischen Legierung

k

= Oxidationsgeschwindigkeitskonstante

n

= Oxidationsgeschwindigkeitsexponent

A detailed model of the life of iron-chromium-aluminum alloys is described in the article by I. Gurrappa, S. Weinbruch, D. Naumenko, WJ Quadakkers, Materials and Corrosion 51 (2000), pp. 224-235. There, a model is presented that the lifetime of iron-chromium-aluminum alloys depending on the aluminum content and the sample shape is dependent, in this formula, possible flakes are not taken into account

t _B

= Life, defined as the time until oxides other than alumina appear

C ₀

= Aluminum concentration at the beginning of the oxidation

C _B

= Aluminum concentration in the presence of oxides other than aluminum oxides

ρ

= specific density of the metallic alloy

k

= Oxidation rate constant

n

= Oxidation rate exponent

wobei Δm* die kritische Gewichtsänderung ist, bei der die Abplatzungen beginnen.Taking into account the flaking results for a flat sample of infinite width and length with the thickness d (f ≈ d), the following formula:

where Δm * is the critical weight change at which the flakes begin.

Both Press formulas from that life with reduction of aluminum content and a big one surfaces to volume ratio (or small sample thickness) decreases. Was not considered in this Article the influence of the temperature cycle, as it z. B in: J.P. Wilber, M.J. Bennett and J.R. 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 ", Feb. 1999, Frankfurt, Germany, Editors M. Schütze and W. J. Quadakkers, p. 133-147 (1999) for Cycle times from 1 h to 290 h is described, with this Work the cycle times have an effect only if flaking occurs.

Also in V.K. Tolpygo, D.R. Clarke, "Spalling failure of α-alumina films grown by oxidation: I. Dependence on cooling rate and metal thickness, Materials science and engineering ", A278 p.142-150 (2000) becomes the influence the cycle time and the cooling rate described. In particular, these two articles show that one short heating time, a short cooling time and a short hold time at the high temperature shorten the life considerably.

With Temperature cycle is the combination of heating time, Holding time at temperature, cooling time and waiting time until reheating is defined. temperature cycles with a short warm-up time, a short cool-down time, and a short one Holding time at the high temperature will be brief and called fast temperature cycles. These include z. B. temperature cycles with a total duration in the range of several seconds to several Minutes, with total duration being the sum of heating time, holding time at temperature, cooling time and wait until the beginning of the next heating is meant.

heating conductor, the thin ones Foils (eg about 30 to 100 μm Thickness at a width in the range of one or several millimeters) exist, characterized by a large surface area to volume ratio. This is advantageous if you have fast heating and cooling times want to reach as they are z. As required in the heating elements used in Ceranfeldern be used to quickly make the heating up and visible fast heating similar to one To reach gas cooker. At the same time, however, the large surface area is too volume ratio disadvantageous for the life of the heating conductor (see above). In addition, must in this application the temperature is limited under the glass, to protect it from harm. This can be done by repeated, momentary switching off of the current be achieved. Both have a load of the heat conductor through short heat-up times and fast cooling and only short hold times as a result, which, as described above, further reduces the lifetime.

In none of the aforementioned Pamphlets are particularly noted on this effect of the temperature cycle, d. H. none of the above Alloys has been developed in this regard.

It is known from the above-described prior art that minor additions of Y, Zr, Ti, Hf, Ce, La, Nb, W, the life of FeCrAl alloys is strong influence.

To J. Klöwer, Materials and Corrosion 51 (2000), pages 373-385 allowed the addition not too big otherwise there is an increased Oxidation rate occurs, resulting in increased consumption of aluminum and thus a shortened Lifespan means. This increased Oxidation rate causes e.g. an addition of only 0.11% hafnium an iron-chromium-aluminum alloy with 20% Cr, 7% aluminum and 0.01% yttrium. Further examples for one increased Oxidation rate due to excessive addition of a reactive element in the mentioned Articles are an iron-chromium-aluminum alloy with 18.8% Cr, 7% Al and an addition of 0.11% Y or an iron-chromium-aluminum alloy with 20% Cr, 7% Al and additions of 0.04% yttrium, 0.05% Zr and 0.05% Ti. This shifts the area in which an increased oxidation rate by adding too much a reactive element occurs with the aluminum content. So caused by J. Klöwer, Materials and Corrosion 51 (2000), pages 373 to 385 0.04% Zr in an iron-chromium-aluminum alloy containing 20% Cr, 7% Al and 0.05 % Y already increased Oxidation rate. The same amount of Zr in an iron-chromium-aluminum alloy with 20 % Cr, 5.5% Al and 0.05% Y and 0.05% Hf (J. Klöwer, A. Kolb-Telieps, M Brede: in Bode, H. (ed.) Metal-Supported Automotive Catalytic Converters, DGM Information Society, Oberursel, 1997, pp.33ff) but no increased Oxidation rate. All investigations in J. Klöwer, Materials and Corrosion 51 (2000), pages 373 to 385 and (J. Klöwer, A. Kolb-Telieps, M Brede: in Bode, H. (ed.) Metal-Supported Automotive Catalytic Converters, DGM Information Society, Oberursel, 1997, p.33 ff were using cycles carried out in the oven for 100 h or 96 h, which means very long cycles are.

Of the Invention is based on the object, an iron-chromium-aluminum To provide alloy that has a longer life than before used iron-chromium-aluminum alloys, especially for components with big surfaces to volume ratio, or smaller band thickness, has.

These Task is solved by a melt-metallurgically produced iron-chromium-aluminum alloy with high durability, with (in mass%) 4 to 8% Al, 16 to 24 % Cr and additions of 0.05 to 1% Si, 0.001 to 0.5% Mn, 0.02 to 0.2% Y 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, max. 0.04 % N, max. 0.04% P, max. 0.01% S, max. 0.5% Cu and the usual melting impurities, residual iron.

advantageous Further developments of the alloy according to the invention are the subclaims remove.

The Element Hf may be further characterized by at least one of the elements Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or Cer are completely or partially replaced, with partial substitution Areas between 0.02 and 0.15 mass% are conceivable.

advantageously, should the alloy of the invention with (in% mass) max. 0.02% N, max. 0.02% P and max. 0.005% S be melted.

At the State of the art according to corrosion 51 (2000) and DGM Information Society were all investigations with cycles of 100 h or 96 h in the furnace, resulting in very long cycles are.

Surprisingly It has been shown in experiments with very short cycles that the Range of reduced lifetime, which at the same time an increased oxidation rate means there completely different. That's how it turns out for the iron-chromium-aluminum alloy according to the invention, with min. 0.1% Zr at min. 0.02% Y, in the above-mentioned cycles from 100 h or 96 h in the oven according to J. Klöwer, Materials and Corrosion 51 (2000), pages 373 to 385 would show an increased oxidation rate and thus a shortened Lifespan, with a lifetime test on wire, which is a low surfaces to volume ratio has, with the shorter Cycle from 2 min "on" and 15 s "off" one at the top the variation range of the lifetime of the alloy according to the state the technical life. This difference becomes even more serious when looking at the durability test to films of 50 microns thickness, which have a very large surface to volume ratio and very short cycles of 15 seconds "on" and 5 seconds "off".

Preferred Fe-Cr-Al alloys are characterized by the following composition (in% by mass):

Depending on the application, the following elements can be set in their spreading ranges 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 is preferably used for electric heating elements, in particular with short heating and cooling times, short holding times on temperature and short waiting times up to the beginning of a new heating.

The alloy according to the invention is also used in heating elements that have a high dimensional stability or a require low sagging.

Also The alloy according to the invention can be used in heating conductors made of foils with a thickness of 20 to 100 μm.

Prefers is also the use as Heizleiterlegierung for use in hobs.

Finally exists also the possibility the alloy according to the invention for the Use in furnace construction to use.

Further preferably usable alloy ranges are in the corresponding dependent claims specified.

The Details and advantages of the invention will become apparent in the following examples explained in more detail.

Table 1 summarizes laboratory-molten iron-chromium aluminum alloys L1 to L8 and E1 to E6 and the large-scale molten alloys G1 to G3. In the case of the alloys smelted in the laboratory, both wire and 50 μm thick film were produced from the material cast in blocks by means of hot and cold forming and suitable intermediate annealing. The film was cut into strips of 6 mm width. For large-scale molten alloys, a sample was taken from the large-scale production at a strip thickness of 50 μm and, if necessary, the right one Width of about 6mm cut.

For heating conductors in the form of wire accelerated life tests for comparing materials with each other, for example, with the following conditions are possible and common:
The heat conductor life test is carried out on wires with a diameter of 0.40 mm from which wire coils with 12 turns, a coil diameter of 4 mm and a coil length of 50 mm. The wire helices are clamped between 2 power supply lines and heated up to 1200 ° C by applying a voltage. The heating at 1200 ° C takes place for 2 minutes, then the power supply is interrupted for 15 seconds. At the end of the life of the wire fails by the fact that the remaining cross-section melts through.

One analog life test leaves to perform on foil strips. Here foil strips of 50 μm thickness and 6 mm width are interposed 2 power feedthroughs clamped and heated by applying a voltage up to 1050 ° C. Heating to 1050 ° C took place for each 15 s, then the power supply is interrupted for 5 s. At the end the life of the film fails because of the remaining cross-section melts.

When Lifetime is in both tests the total time that the wire, or the film at the stated temperature, without interruption times specified. The temperature is during of the life test with an optical pyrometer and measured if necessary, corrected to the setpoint temperature.

The Results of the endurance tests are listed in Table 1. The the mean values given in the table are the mean values of at least 3 samples.

At the Durability test on wire, the coils are clamped horizontally at the beginning. In the course of the life test they sag. The lower the Sagging, the bigger the dimensional stability of the Material. A big dimensional stability is a beneficial technological property, as this means that the parts made of the material a slight change in shape while of use at higher temperatures demonstrate.

The industrially molten alloys G1 and G2 and the laboratory smelted Alloy L2 show an iron-chromium-aluminum alloy with (in Mass%) about 20% Cr, about 5% Al and additions of 0.04 to 0.07% Y, 0.04 to 0.07% Zr and 0.04 to 0.05% Ti, a carbon content from 0.033 to 0.037%, an Si content of 0.15 to 0.34%, one Mn content of about 0.24% and minor contents of N, S, Ce, La, Pr, Ne, P, Mg, Ca, as indicated in Table 1, according to the prior art of the technique. The lifetime of L2 at 0.4 mm thick wire at 1200 ° C at one Cycle of 120 s "on" and 15 s "off" serves as reference and is set to 100%.

The Life at 50 microns thick film at 1050 ° C and a cycle of 15 seconds "on" and 5 seconds "off" is between 102 and 124% of the life of the laboratory batch L1. Also the large-scale molten alloy G3 shows an iron-chromium-aluminum alloy with about 20% Cr, about 5% Al and additions of 0.06% Y, 0.04% Zr, 0.02% Hf, a carbon content of 0.029%, an Si content of 0.28%, a Mn content of 0.20% and minor contents of P, Mg, Ca, as indicated in Table 1 according to the prior art. The life span at 50 μm thick film at 1050 ° C and a cycle of 15 seconds "on" and 5 seconds "off" is 148% the lifetime of the laboratory batch L1. So have the alloys according to the state of the art in the life test at 50 microns thicker Foil at 1050 ° C and a cycle of 15 seconds "on" and 5 seconds "off" values of about 100% up to approx. 150% of L1.

For the laboratory lots L1 and L3 to L8, the contents of Si, C, Zr, Ti and Hf have been varied. Not varied was the content of Mn, which is between 0.24 and 0.28% for all laboratory melts, and the minor additions of P, Mg, Ca, Ce, La, Pr, Ne, as shown in Table 1. At a life test of 0.4 mm thick wire at 1200 ° C at a cycle of 120 s "on" and 15 s "off" the variant L1 shows 0.03% Y, 0.04% Zr and 0.02% Hf and a carbon content of 0.007% and a Si content of 0.35% a fairly long life of 116%. The variants L3 and L7 with only one Y addition of 0.06% or 0.05% and a carbon content of 0.002 or 0.031% and a Si content of 0.34 and 0.35% has in the test Wire a life of only 41% or 51%. The variants L4 and L5 with an addition of 0.04 and 0.05% Y and 0.05 and 0.014% Zr and carbon contents of 0.002 and 0.003% and the Si contents of 0.33 and 0.35, respectively % have a lifetime of 79% and 86%, respectively, better than those of L3 and L7, but have not yet reached the lifetimes of L2 or L1. The variant L6 with an addition of 0.05% Y and 0.05% Hf and carbon contents of 0.010% and a Si content of 0.36% has a Le lifetime of 85%, which is also better than that of L3 and L7 but has not reached the lifetime of L2 or L1. The laboratory batch L8 has additions of 0.05% Y, 0.21% Zr and 0.11% Ti and a carbon content of 0.018% and an Si content of only 0.02%. This is due to the high content of Zr and Ti according to J. Klöwer, Materials and Corrosion 51 (2000), pages 373 to 385 already in the concentration range of the increased oxidation rate in the life test with long cycles of z. B. 100 h or 96 h in the oven. Nevertheless, it shows a lifetime of 105% wire life test on wire, which is between L1 and L2.

Also in the field of increased oxidation rate in the life test with long cycles of z. B. 100h or 96 h in the furnace alloys of the invention E1 with 0.05% Y, 0.18% Zr, 0.04% Hf, 0.006% C and 0.35% Si and E2 with 0.03% Y, 0.20% Zr, 0.11% Ti instead of hafnium, 0.020% C and 0.61% Si. Both alloys have good lifetimes of 96% for E2 and as much as 118% for E1 in the wire ladder life test. This results in the following ranking for the lifetime of the laboratory melts (sorted in each case with falling lifetime):
Top group: E1, L1, L8, L2, E2, characterized by additions of Y and Zr and, in addition, addition of Ti or Hf.
Average life: L5, L6, L4, characterized by additions of Y and Zr or Y and Hf.
Bad lifespan: L7, L3, characterized by an addition of only Y.

This corresponds to the knowledge and experience of the prior art. The alloy L2 corresponds to z. B. the industrially molten alloys in the prior art G1 and G2.

The Picture looks slightly different when the heating conductor life test at 50 μm thick film at 1050 ° C and a cycle of 15 seconds "on" and 5 seconds "off" is considered: The alloys showing poor service life on wire during testing L3 and L7 show a lifetime of 94% and 110% of L1, respectively in the range of the life of the alloys according to the state of Technology is. The test on wire has an average life Alloys L5, L6, L4 show a lifetime of 145 % or 113% of L1, which is also in the range of lifetime the alloys of the prior art. The test on wire in the leading group alloys L1 and L2 show a lifetime of 100% and 125% of L1, the alloy L8 shows a good life of 140% of L1, which is in the range the lifetime of the alloys according to the prior art.

Surprisingly showed the cited alloys according to the invention E1 and E2 in the area of elevated Oxidation rate in the life test with long cycles of z. B. 100 h or 96 h in the oven lying alloys E1 and E2 very high Lifetimes of with 256% one all others far superior Value at E1 and 171% at E2, well above the range of life the alloys of the prior art goes out. Similarly surprising high lifetimes show the inventive alloys E3 with 201 % and contents of 0.05% Y, 0.21% Zr, 0.021% C and 0.19% Si and E4 at 227% and contents at 0.07% Y, 023% Zr, 0.07% Ti, 0.014 % C and 0.19% Si and E5 at 249% and 0.07% Y, 0.22 % Zr, 0.07% Hf, 0.018% C, and 0.20% Si and E6 at 283% and contents 0.05% Y, 0.17% Zr, 0.05% Hf, 0.016% C and 0.19% Si.

In order to This results in the following ranking.

top group with lifetimes greater than 170 % of L1: E1 to E6, characterized by addition of Y and Zr and / or Hf and / or Ti in the range of increased oxidation rate in the life test with long cycles of z. B. 100 h or 96 h in the oven and a carbon content in the range of 0.003 to 0.025% and Si contents of more than 0.05%.

group with lifetimes ranging from about 100% to 150% of L1, which in the prior art: G3, L5, L8, L2, G2, L4, L6, G1, L1, L7, L3, characterized by lower addition of Y and Zr and / or Hf and / or Ti outside of the area of the raised Oxidation rate in the life test with long cycles of z. B. 100 h or 96 h in the oven or in the case of L8 by one too small Si content with addition of Y, Zr and Hf in the region of increased oxidation rate.

at the for the applications important dimensional stability, measured as sagging of the Spiraling at 50 h burning time in mm, are the alloys of the invention E1, E2 and L8 with values between 5 and 7 mm in the top group compared to the rest Alloys L1 to L7 according to the prior art with values between 17 and 19 mm. The alloys of the invention thus still have the advantage of high dimensional stability.

The claimed limits for the invention can therefore be explained in detail as follows:
A minimum content of 0.02% Y is necessary to obtain the oxidation resistance-enhancing effect of Y. The upper limit is set at 0.2% by weight for cost reasons.

It is a minimum content of 0.1% Zr necessary to short and fast temperature cycles in the range of long life to come. The upper limit is for cost reasons placed at 0.3 mass% Zr.

It a minimum content of 0.02% Hf is necessary to maintain the oxidation resistance to get increasing effect of Hf. The upper limit is added for cost reasons 0.2% by mass Hf.

It is a minimum content of 0.02% Ti necessary to improve the oxidation resistance to get increasing effect of Ti. The upper limit is added for cost reasons 0.2 mass% Ti laid.

Of the Carbon content should be 0.003% to 0.05% to improve processability to ensure.

Of the Nitrogen content should be a maximum of 0.04% to the formation to avoid deterioration of the processability of nitrides.

The Levels of phosphorus and sulfur should be kept as low as possible since these are surface-active Elements the oxidation resistance affect. It will therefore max. 0.04% P and max. 0.01% S set.

Chromium contents between 16 and 24% by weight have no decisive influence on the service life, as can be read in J. Klöwer, Materials and Corrosion 51 (2000), pages 373 to 385. However, a certain chromium content is necessary because chromium promotes the formation of the particularly stable and protective α - Al ₂ O ₃ layer. From approx. 16% this is guaranteed. Therefore, the lower limit is 16%. Chromium contents> 24% complicate the processability of the alloy.

The aluminum content of the alloy according to the invention should be 4 to 8%. Approximately According to the "Handbuch der Hochtemperatur-Werkstofftechnik, Ralf Bürgel, Vieweg Verlag, Braunschweig 1998" on page 272 in Figure 5.13, 4% aluminum is required to form a closed α - Al ₂ O ₃ layer Higher Al contents than 8 % affect the processability.

To J. Klöwer, Materials and Corrosion 51 (2000), pages 373 to 385 increase additions of silicon's life by improving adhesion the topcoat. It is therefore a content of at least 0.05 mass % Silicon required. Too high Si contents make the processability difficult the alloy. Therefore, the upper limit is 1%.

manganese is limited to 0.5 mass% because this element is the oxidation resistance reduced. The same applies Copper.

The Levels of magnesium and calcium are in the spread range 0.0002 set to 0.05% by weight.

Claims (19)

Iron-chromium-aluminum alloy with high durability with (in% by mass) 4 to 8% Al and 16 to 24% Cr and additions of 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, rest iron. Iron-chromium-aluminum alloy according to claim 1 with (in mass%) 5 to 6% Al, 18 to 22% Cr and additions of 0.05 to 0.7% Si, 0.001 to 0.4% Mn, 0.03 to 0.1% Y, 0.15 to 0.25% Zr and / or 0.02 to 0.15% Hf, 0.003 to 0.03% C, 0.0002 to 0.03 % Mg, 0.0002 to 0.03% Ca, max. 0.04% N, max. 0.04% P, max. 0.01 % S, max. 0.5% Cu and the usual melting impurities, residual iron. Iron-chromium-aluminum alloy according to claim 1 or 2, with (in mass%) 5 to 6% Al, 18 to 22% Cr and additions of 0.05 to 0.7% Si, 0.001 to 0.4% Mn, 0.03 to 0.08% 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, max. 0.04% N, max. 0.04% P, max. 0.01% S, max. 0.5% Cu and the usual melting-related Impurities, rest iron. Iron-chromium-aluminum alloy according to one of claims 1 to 3 with (in% by mass) 5 to 6% Al, 18 to 22% Cr and additions of 0.05 to 0, 7% Si, 0.001 to 0.4% 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, max. 0.04% N, max. 0.04% P, max. 0.01% S, max. 0.5% Cu and the usual melting-related Impurities, rest iron. Iron-chromium-aluminum alloy according to one of claims 1 to 4, in the Hf entirely by at least one of the elements Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium is replaced. Iron-chromium-aluminum alloy according to one of claims 1 to 4, in which Hf is partially replaced by (in% by mass) 0.01 to 0.18% at least one of the elements Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium is replaced. Iron-chromium-aluminum alloy according to one of claims 1 to 6, at the Hf partly by (in mass%) 0.02 to 0.15% at least one of the elements Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium is replaced. Iron-chromium-aluminum alloy according to one of claims 6 or 7, in the case of Hf wholly or partly by (in% by mass) 0.02 to 0.11 % of at least one of the elements Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium is replaced. Iron-chromium-aluminum alloy according to one of claims 6 to 8, in Hf wholly or partly by (in% by mass) 0.03 to 0.07 % of at least one of the elements Sc and / or Ti and / or V and / or Nb and / or Ta and / or La and / or cerium is replaced. Iron-chromium-aluminum alloy according to one of claims 1 to 9 with (in% mass) max. 0.02% N, max. 0.02% P and max. 0.005% S. Iron-chromium-aluminum alloy according to one of claims 1 to 10 with (in mass%) max. 0.01% N, max. 0.02% P and max. 0.003 % S. Iron-chromium-aluminum alloy according to one of claims 1 to 11, further comprising (in% mass) max. 0.1% Mo and / or 0.1% W. Use of iron-chromium-aluminum alloy after one of the claims 1 to 12 as an alloy for use in electrical heating elements. Use of iron-chromium-aluminum alloy after one of the claims 1 to 12 as an alloy for Use in electrical heating elements with short heating as well cooling times, short holding times on temperature and short waiting times up to the beginning of a new heating. Use of iron-chromium-aluminum alloy after one of the claims 1 to 12 as an alloy for the use in electrical heating elements, which have a high dimensional stability or a require low sagging. Use of iron-chromium-aluminum alloy after one of the claims 1 to 12 as an alloy for Use in heating conductors made of foils with a thickness of 20 to 100 μm. Use of iron-chromium-aluminum alloy after one of the claims 1 to 12 as an alloy for the use in heating conductors made of wires with a diameter <6 mm. Use of iron-chromium-aluminum alloy after one of the claims 1 to 12 as heating conductor alloy for use in hobs, especially ceramic hobs. Use of iron-chromium-aluminum alloy after one of the claims 1 to 12 as heat conductor alloy for use in furnace construction.