KR20060111662A - Method for the manufacture of an austenitic product as well as the use thereof - Google Patents

Abstract

The present invention relates to a method to produce an austenitic alloy by 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.

Description

Manufacturing method of austenite-based product and its use {METHOD FOR THE MANUFACTURE OF AN AUSTENITIC PRODUCT AS WELL AS THE USE THEREOF}

The present invention relates to a process for the manufacture of austenitic products having increased aluminum content and to their use in applications where high temperature resistance and improved mechanical properties of oxidation resistant forms are required.

As the application temperature for steel materials rises in various high temperature applications, recent ferritic materials have more precise ferritic FeCrAl materials, and in the form of rapid gas changes, changes in gas flow with temperature, direction and / or composition It is often found to be mechanically vulnerable to resist mechanical stresses such as vibrations and vibrations that occur at high temperatures.

EP 1235682 B1 discloses the use of austenitic nickel-based or cobalt-based alloys coated with aluminum or an aluminum alloy and rolled to final dimensions. Thereby, by heat-treating at the temperature over 600 degreeC, the minimum thickness thin film of about 50 micrometers is manufactured and tested at about 1100 degreeC. At 1100 ° C., the mass of the sample is increased to 7.6% after 400 hours. Compared to conventional FeCrAl materials, the problem is that the oxidation rate, which is considered as a decisive factor for the service life of the catalyst support material, is relatively high.

Austenitic alloys generally have higher mechanical strength than ferritic alloys at the same high temperatures. The high aluminum content of austenitic materials has significantly improved oxidation resistance compared to the low aluminum content of austenitic materials because they are very low ductility at normal hot working temperatures, ie 750 ° C. to 1200 ° C.

Catalytic metal materials with elevated processing temperatures and increased mechanical loads must meet the following conditions:

Improved mechanical strength with respect to materials used recently as disclosed in US 5,578,265 B and higher oxidation resistance than the austenitic high strength materials disclosed in EP 1235682 B1. For use as a support material in the catalyst, the 50 μm thick thin film material should not be increased by more than 6% by weight, preferably by 4% by weight or less, after 400h oxidation to 1100 ° C. in air. Al-alloy austenitic steels or nickel or cobalt-based alloys of 4.5% Al or more can expect sufficiently satisfactory mechanical properties, but also due to the maximum limited hot workability at Al contents in excess of 4.5% by weight. Then, for a thin film having a thickness of 50 μm in a constant atmosphere, it may be increased by 6% by weight or more after 400 h oxidation at 1100 ° C., which makes it impossible to produce a thin strip by a conventional method. In addition, the oxidation resistance of such materials is still poor compared to the recently used ferritic materials.

Therefore, more heat resistance and oxidation resistance are required, and a material having higher mechanical strength than that used recently is required. In addition, such materials have satisfactory or better manufacturing properties than materials known to date. This is the case for all other product types used in the conditions described above, such as strips, thin films, wire rods, sheet metal plates and tubes.

Therefore, it is an object of the present invention, as the low Al austenitic base alloy is coated with a high Al content aluminum composition at a temperature between 100 ° C. and 600 ° C., the final product has an Al content of 4.5-12% by weight, Preferably to provide a method having an Al content of 5.5 to 12% by weight.

It is also an object of the present invention to provide an austenitic alloy material for use in high temperature applications which can be produced by the process.

1 shows the results of a hot ductility test (Gleeble testing test), in which the reduction in area for cracking is measured as a function of test temperature.

2 shows the oxidation rate in air at temperatures of 1000 ° C. in Examples C, D and Comparative Example 1. FIG.

3 shows the rate of oxidation in air at a temperature of 1100 ° C. in Example C and Comparative Example 1. FIG.

FIG. 4 shows the oxidation rates in air at Examples C, E, and F and at temperatures 1100 ° C. in Comparative Examples 1 and 3 with thicknesses of 50 μm and 3 mm.

5 shows the aluminum content in the Al coated material after different lengths of annealing time at 1050 ° C., shown as a function of distance from the surface.

FIG. 6 shows the microstructure in the Al coated material which was annealed after 50 minutes at 1150 ° C. in Ar gas.

The object of the present invention is the following composition (% by weight), i.e.

Ni: 20-70%, Cr: 15-27%, Al: 0-5%, Mo and / or W: 0-4%, Si: 0-2%, Mn: 0-3%, Nb: 0- 2%, Y, Zr and / or Hf: 0 to 0.5%, Ti: 0 to 0.5%, one or more rare earth metals (REM) such as Ce, La, Sm: 0 to 0.1%, C: 0 to 0.2% , N: 0 to 0.1%, balance Fe and an austenitic base alloy prepared by coating an austenitic base alloy having a composition consisting of conventional impurities with an aluminum composition such as aluminum or an aluminum base alloy described below.

Preferred compositions (% by weight) of the substrate are Ni: 20 to 70%, Cr: 18 to 25%, Al: 1 to 4%, Mo and / or W: 0 to 4%, Si: 0 to 2%, Mn: 0 to 3%, Nb: 0 to 2%, Y, Zr and / or Hf: 0 to 0.5%, Ti: 0 to 0.5%, at least one rare earth metal (REM) such as Ce, La, Sm: 0 to 0.1%, C: 0 to 0.1%, N: 0 to 0.05%, balance Fe and common impurities.

By a two step process, the aluminum content and mechanical properties and oxidation resistance of the final product can be optimized independently of each other.

After coating the substrate with aluminum or an aluminum-based alloy, the final alloy is in weight% Ni: 25 to 70%, Cr: 15 to 25%, Al: 4.5 to 12%, Mo and / or W: 0 to 4% , Si: 0-4%, Mn: 0-3%, Nb: 0-2%, Ti: 0-0.5%, Y, Sc, Zr and / or Hf: 0-0.5%, Ce, La, Sm and One or more of the same rare earth metals (REM): 0 to 0.2%, C: 0 to 0.2%, N: 0 to 0.1%, balance Fe, and a composition consisting of common impurities.

Austenitic substrates have good high temperature strength, which is increased by precipitation of Ni (Nb, Al) and, if necessary, Mo and / or W dissolved in solution. In addition, increased mechanical stability and resistance to particle growth can be obtained by precipitation of one or more carbides and / or nitrides of Ti, Nb, Zr, Hf.

Carbon as solid solution or carbide contributes to an increase in mechanical strength at high temperatures. At the same time, the high carbon content in the substrate deteriorates the characteristics during cold working. Therefore, the maximum content of carbon in the substrate should be limited to 0.2% by weight.

Nitrogen as solid solution nitrogen or nitride contributes to the increase in mechanical strength at high temperatures. At the same time, if the content of nitrogen in the substrate is high, brittle aluminum nitride can be formed after the preparation of the substrate or coating with aluminum or an aluminum-based alloy. Therefore, the maximum content of nitrogen in the substrate should be limited to 0.1% by weight.

The austenitic alloys produced according to the invention are used after coating and non-heat treatment or after diffusion annealing. The most preferable composition of the base alloy can be obtained by containing 1 to 4% by weight of Al. If the content of aluminum is this, the final alloy will have improved oxidation resistance and improved economic productivity without the risk of increased production disturbances compared to the manufacture of materials with low aluminum content. After coating with aluminum or an aluminum based alloy, the material should contain at least 4.5% by weight of Al in total.

According to the present invention, the coating with aluminum or an aluminum-based alloy should be made at a temperature range of the substrate which is below the melting point of aluminum, that is, at a temperature of 100 ° C to 600 ° C, preferably 150 ° C to 450 ° C.

Adding Zr and / or Hf and REM and / or Y and / or Sc results in increased resistance to peeling and flaking of the oxides formed. The elements can be added to the base alloy and / or the aluminum based alloy used for coating and supplied to the final product.

Any composition of the alloy according to the invention can be obtained by conventional metallurgy techniques. Alternatively, however, in the manufacture by the process according to the invention, materials with controlled microstructure and optimum oxidation and mechanical properties can be obtained. Another advantage of the process according to the invention is that the total content of aluminum in the final product is not limited by the embrittlement effect obtained during subsequent cold and / or hot working due to the aluminum content in excess of approximately 4.5% by weight. In addition, according to the method of coating the substrate with aluminum or an aluminum-based alloy according to the present invention, for example, the content of Mo, C, Nb, etc. can be considerably higher than that of a conventionally produced material, and the oxidation properties are remarkably high regardless of the elements present. A final product is obtained that does not deteriorate.

Suitable coating of the base alloy with aluminum or aluminum-based alloys can be made by a process of melting immersion, electrolytic coating, rolling together with aluminum or aluminum alloy strips from the gas phase by so-called CVD or PVD techniques. The coating of aluminum or aluminum-based alloys can be made after the base alloy has been rolled or otherwise machined to the desired product dimensions. In this process, diffusion annealing may be performed to provide homogenization of the material, and then, in one or more steps, plastic working may then be carried out to supply the final product. Plastic processing, such as rolling or drawing, can be done directly in the coated product of dimensions larger than the desired final dimension. In this case, annealing can be performed after plastic working.

The content of aluminum in the final product can be varied by several factors (eg, the thickness of the substrate relative to the thickness of the coating, the content of aluminum in the substrate and the content of aluminum in the coating).

However, as mentioned above, the total content of aluminum in the final product should be at least 4.5% by weight to ensure sufficient properties. The product may be used in the form of an uneven homogeneous material or a laminate or a material having an Al concentration gradient with a higher Al content at the surface than the center of the material.

Depending on the coating method used, various compositions of the Al alloys applied are more suitable than others. The aluminum alloy is Si: 0 to 25% by weight and / or at least one Ce, La, Sc, Y, Zr, Hf: 0 to 2% by weight and / or at least one of Mg, Ti, Cr, Mn, Fe, Ni , Co: 0 to 5% by weight and / or at least one B, Ge: 0 to 1% by weight, preferably, the aluminum alloy is Al: 90% by weight or more, Si: 0 to 10% by weight and / Or at least one Ce, La, Sc, Y, Zr, Hf: 0-2 wt%, more preferably, the aluminum alloy is at least 95 wt% of Al, 0-5 wt% of Si: and / or It should contain 0 to 2% by weight of at least one of Ce, La, Sc, Y, Zr and Hf.

In the following, it is presented how the demand for strength and oxidation resistance is satisfied by the austenitic Al alloy material produced according to the method described in the present invention. It is also suggested that the materials produced according to the present method have the same composition but are superior in high temperature strength, oxidation resistance and processability compared to materials prepared according to conventional methods.

Example 1

Table 1 shows examples of compositions of experimental alloys. The alloys according to Examples A and B as well as Comparative Examples 1, 2 and 3 were produced in a conventional manner by dry metallurgy and hot working.

Table 1: Composition of Experimental Alloys

A (359) B (357) Comparative Example 1 Comparative Example 2 C 0.052 0.021 0.01 0.019 N 0.016 0.032 0.01 0.020 Ni 32.35 17.61 0.3 33.18 Al 2.95 1.68 5.3 5.43 Cr 21.83 21.81 20 21.50 Nb 0.01 0.61 0.01 <0.01 Mo 0.02 0.02 0.01 <0.01 Zr 0.07 <0.002 0.01 <0.005 REM <0.005 0.026 0.03 0.042 Ti 0.16 <0.005 0.01 <0.005 Si 0.15 0.14 0.3 0.16 Mn 0.12 0.10 0.3 0.11

Comparative Example 1 is an alloy with oxidation resistance suitable for use in today as a support material in catalytic converters. Comparative Example 2 is a high Al content of austenitic alloys prepared by conventional methods. The yield for the hot working of the alloy is only about 10%, ie 90% of the material has internal defects in the form of cracks, for example, and cannot be used for further processing.

The alloys according to Examples A and B have a composition suitable for use as a substrate of a coating process, in which a thin film of aluminum or an aluminum based alloy is deposited on the substrate. From the alloys according to Examples A and B as well as Comparative Example 1, strips of 50 μm thickness were produced via hot rolling and cold rolling. The yields of the alloy products prepared in Examples A and B were the same as in Comparative Example 1.

The nitrogen content in the substrate is made low to prevent the production of aluminum nitride. To further limit this tendency, Ti, Nb and / or Zr and / or Hf were further added. The addition of these elements forms nitrides that are more stable than AlN, resulting in reduced AlN formation. In addition, a composition is selected to enable efficient production of the substrate in thin strips. For example, the content of carbon is less than 0.10%, thereby obtaining a satisfactory material yield in the cold working process. With the relatively high Al content in the substrate, the required amount of Al to be deposited on the substrate is reduced to achieve a sufficient Al content in the final product.

In Table 2, base alloys with very good high temperature strengths are presented, for example at 700 ° C. the maximum strength of the alloys according to Examples A and B is up to three times higher than the conventional materials of Comparative Example 1, and the yield point of tensile at this temperature. Is 2.8 to 5 times higher than Comparative Example 1. At 900 ° C., the maximum strength of the alloys according to Examples A and B is at least 3.5 times higher than in Comparative Example 1, and the tensile yield point is about 5 times higher than in Comparative Example 1.

Table 2: Tensile test results at different temperatures

Example Room temperature 700 ℃ 900 ℃ Rp _0.2 Rm A5 Rp _0.2 Rm A5 Rp _0.2 Rm A5 A 275 625 39 254 441 22 98 146 99 B 239 546 39 141 337 44 108 150 78 E 166 Comparative Example 1 480 670 25 50 140 90 20 40 150 Comparative Example 2 437 814 25 340 511 - 91 151 55

Thus, the two base alloys used in Examples A and B meet the requirements of sufficient mechanical strength and workability as thin films.

1 shows the results of the hot ductility test of alloys according to Examples A and B and Comparative Example 2, which is called the Gleeble test, in which the rate of area reduction against fracture is measured as a function of test temperature. . Indeed, in order to be able to hot work the alloy, the area reduction to fracture must exceed 40%. In order to obtain reproducible high yields during hot working operations, the average area reduction against fracture at temperatures of 100 ° C. should be at least 70%.

From FIG. 1, the alloys according to Examples A and B can be produced by hot rolling and / or forging, but the alloys according to Comparative Example 2 cannot be produced in sufficient yield by conventional methods. The result is that in order to be able to obtain the good oxidation resistance that the alloy according to Comparative Example 2 can expect, the necessary Al content must be added after the alloy is produced in the form of a thin strip. The alloys according to Examples A and B both have sufficient ductility to be cold rolled into very thin strips with satisfactory productivity at room temperature and elevated temperatures, so that the alloy can be produced without problems with a thickness of 50 μm or less. This alloy is thus a good candidate material for use as a substrate for coating aluminum or aluminum based alloys.

Example 2

The alloys of Examples C and D were coated on both sides of the strip of the alloy according to Examples A and B, which were cold rolled to a thickness of 50 μm, respectively, so that the total content of Al corresponds to 5.5 to 6% (see Table 3). Amount Al was produced by vaporizing or sputtering. The coating was affected by this heating of the substrate, although not as hot as molten Al would appear on the substrate. The coating with Al or Al alloy according to the present invention may be influenced in the range where the temperature of the substrate is 100 ° C to 660 ° C, preferably 150 ° C to 450 ° C.

Table 3: Cloth Test

Substrate alloy Thickness before coating [㎛] Coating thickness of coated Al alloy [㎛] Desired total Al content [%] Measured coating thickness [μm] Example C Example A 50 2.5 6.0 2.7 Example D Example B 50 3.5 6.0

As mentioned above, the alloy according to Comparative Example 2 of the total composition almost the same as the alloy of Example C can only be forged in a very low yield. Therefore, due to the limited hot ductility, this alloy is seldom easy to manufacture in the form of thin strips. However, as shown in Table 2, the same alloy has very good heat resistance, for example, the maximum strength at both 700 ° C. and 900 ° C. is three to four times higher than the conventional material of Comparative Example 1, and at both experimental temperatures. The tensile yield point of is 4 times higher.

Example 3

The thickness of the Al layer obtained on the 50 μm-thick strip according to Example C was measured by GDOES (Glow Discharge Optical Emission Spectroscopy), which allows precise measurement of the composition and thickness of the thin film layer. The analysis shows that the total Al content of the sample is 5 to 6% by weight. These samples were oxidized up to 620 hours at 1000 ° C. in air. The results are shown in FIG. The alloy according to Example C exhibits oxidation resistance comparable to that of the Fe-Cr-Al alloy (Comparative Example 1) of the same thickness prepared by the conventional method, and shows much improved oxidation resistance than the alloy according to Example D. . After 400 hours, the weight of the alloy according to Example C was increased by 2.3%, while the weight of the alloy according to Example D was increased by 5%. After the same time, the weight of Comparative Example 1 increased by about 2.2%.

An oxidation test of the alloy according to Example C was carried out with Comparative Example 1 at 1100 ° C., which is shown in FIG. 3. Both materials were tested in the form of a 50 μm thick thin film. After the test time was over 300 hours, both materials were equally good. After 400 hours of testing, the weights of the alloys according to Example C and Comparative Example 1 both increased to less than 6%, while the alloys according to Example C increased by 5.9% and the alloys according to Comparative Example 1 by 4.3%. Thus, the alloy according to example C meets sufficient oxidation resistance for catalytic converters, with a weight increase of up to 6% when oxidized at 1100 ° C. for 400 hours at a thickness of 50 μm.

Example 4

Examples E and F are alloys according to Examples C and D, respectively, and were loosened for 20 minutes at 1200 ° C. to equalize the Al content of the material (see Table 4). The ductility of the material was evaluated by a bending test in which the minimum bending radius at which the material can bend without breaking is measured (see Table 4). The narrowest radius of the test material was 0.38 mm. After this bending, no material was damaged. The radius was smaller than that used for the production of catalytic converters. Thus, the strips produced according to the invention have very ductility enough to be used for catalytic converters. At 900 ° C., Example E has a maximum strength of 166 MPa (see Table 2), which is at least four times higher than the material according to Comparative Example 1 currently used, and furthermore prepared according to the invention prepared by conventional methods. It is considerably higher than the material according to Comparative Example 2 having a similar composition as the alloy.

Table 4: Test results for coated and diffusion-annealed samples

Example Furtherance Diffusion loosening Bending radius without breaking [mm] E Same as Example C In H ₂ bun 20/1200 ℃ 0.38 F Same as Example D In H ₂ bun 20/1200 ℃ 0.38

Example 5

The alloys according to Examples E and F were subjected to oxidation tests at 1100 ° C. together with the alloys of Example C according to the invention as well as Comparative Examples 1 and 2. The results are shown in FIG. Comparative Example 2 was tested in the form of a plate having a thickness of about 3 mm, but Examples C, E and F were tested in the form of a thin film of 50 μm. The alloy of Comparative Example 1 was tested in two different states, in the form of a sheet of about 3 mm thickness extracted from a hot rolled strip and in the form of a thin film of 50 μm. Table 5 summarizes the results.

It can be seen from FIG. 4 and Table 5 that the oxidation amount of the thin thin film of Comparative Example 1 is smaller than the oxidation amount of the thick plate. This effect can be explained by the fact that the thin film is easily deformed and absorbs the difference in thermal expansion between the protective oxide and the metal. Thus, the oxide is ruptured (ie, unprotected metal is exposed to oxidation) with cooling and heating is avoided. Relatively thick plates cannot be deformed in the same way, so the sample will be more sensitive to heating and cooling.

Table 5: Mass increase comparison of 50 μm thick strips, 3 mm thick plates and coated and coated + undiffused samples at 1100 ° C.

State 1 State 2 Exam time [hours] (Mass increase in state 1 (g / m 2)) / (mass increase in state 2 (g / m 2)) Comparative Example 1, 50 μm thick Comparative Example 1 3 mm thick 400 0.62 Example C (50 μm thick) Comparative Example 3 3mm Thickness 400 0.40 Example E (50 μm thick) Comparative Example 3 3mm Thickness 400 0.13 Example F (50 μm thick) Comparative Example 3 3mm Thickness 220 0.31 Example E Example C 400 0.32

The alloys according to Examples C and E have a composition substantially similar to that of Comparative Example 2, and in addition, in Comparative Example 1 also have similar effects in which different thicknesses of the sample are expected. However, the relative improvement in oxidation resistance accompanied by a reduction in the sample thickness of the alloy according to the invention is significantly greater than in Comparative Example 1 (see Table 5). This can be thought of as the value of this method, which was not expected.

It was also found that the diffusive annealing, which differs in Examples C and E, leads to unexpectedly large additional oxidation resistance improvements (see Table 5).

First, the alloy according to Example F has good oxidation resistance as in Example C or Comparative Example 1 in the form of a thin film. The test of the alloy according to Example F was stopped after 220 hours. However, comparing the weight gain from Examples E and F up to 220 hours at 1100 ° C., it can be seen that Example E has the most suitable combination of composition and production method in oxidation resistance.

Example 6

A strip of alloy according to Example A, 50 μm thick, was coated with Al by vaporization. Various samples were unrolled for different times in an Ar gas atmosphere at 1050 ° C. The Al concentration distribution of the material was measured by GDOES. The result is shown in FIG. It is clear that the Al rich region remains near the surface even after 8 hours of heat treatment. This region appears to be slowly consumed by Al diffusion into the interior of the strip.

Example 7

A strip of alloy according to Example A, 50 μm thick, was coated with Al by vaporization. The sample was unwound for 50 minutes in an Ar gas atmosphere at 1150 ° C. The microstructure was analyzed by SEM (scanning electron brown rice). 6 shows the area closest to the surface of the sample. In the outermost Fe-Cr rich layer ("0" in FIG. 6) is formed, and Ni and Al rich zones ("1" in FIG. 6) are formed therein. Layer "2" corresponds to a diffusion region in which the Al content slowly decreases with increasing distance from the surface. In layer “3” in FIG. 6, the composition is the same as in the substrate.

Application example

Supporting material for catalytic conversion

Catalytic conversion has long been a necessity in most industrialized countries. The catalytically active material is mechanically carried by the support material. Above all, the need for a support material is that it must have a large surface area, resistance to temperature changes and sufficient mechanical strength and oxidation resistance at the operating temperature of the catalytic converter.

The two main types of support materials used today are ceramics and metals. Ceramic support materials, usually made from cordierit, are not affected by oxidation, but the brittleness of the ceramic material means that the resistance to temperature changes, such as impact and mechanical stress, and rapid changes in temperature, is limited. Today, metal support materials are generally based on rare earth metals (REMs) or ferritic Fe—Cr—Al alloys with small amounts of reactive elements such as Zr or Hf. In order to give the monolith the maximum active surface, the support material should be as thin as possible, usually between 10 μm and 200 μm in thickness. Today, the thickness of a typical strip is 50 μm, but a converter with significantly improved efficiency due to increased surface / volume ratio and / or reduced pressure drop of the catalytic converter is expected due to reducing the thickness of the strip to 30 μm or 20 μm. Can be. The high ductility of the metals provides good resistance to mechanical and thermal fatigue. Aluminum, containing at least about 4.5% by weight in addition to reactive elements, offers the possibility of forming thin, protective aluminum oxides by heating. In addition, the reactive element significantly reduces the tendency for this oxide to peel off, i.e. loosening from the metal by cooling or mechanical deformation. However, the conventional Fe-Cr-Al alloy has a big disadvantage, which is that since the alloy is very weak at high temperatures mechanically, there is a tendency to be significantly deformed by small stresses such as acceleration, pressure change, mechanical shock or temperature change. will be.

The invention is not limited to small volume products such as, for example, thin strips or thin wires. Since austenitic materials having an Al content of 4.5% by weight or more with sufficient productivity and material yield cannot be produced by hot working, it is possible to produce such alloys of thinner thickness by the coating method described in the present invention. It is worth it. This may be influenced by the manufacture of products in the form of substrates, for example in the form of metal plates, strips, thin films or seamless tubes, such that the product has a total content of aluminum of 4.5 weight on one or both sides. Coated with aluminum alloy in excess of%. For example, the non-center tube according to Example 1 can be manufactured by a conventional method, which has an outer diameter of 60.33 mm and a wall thickness of 3.91 mm. In order to be able to achieve a total aluminum content of at least 4.5% by weight in these tubes, an aluminum sheath having a thickness of at least 0.1 mm is required on the inner and outer surfaces. Such amount may be provided to the surface by conventional methods such as, for example, dipping into a melt of an aluminum alloy. If a homogeneous material is desired, a longer heat treatment at higher temperatures is necessary, at least 1000 ° C. being appropriate. Thus, the final product must be produced in a partially homogenized form, in which case, depending on the desired aluminum distribution, for example, by heat treatment such that the material is slowly heated to 1100 ° C. and heat treated at this temperature for 5 minutes to 10 hours. The material has an aluminum gradient that increases towards the surface. It is apparent to those skilled in the art that if the product should be able to have satisfactory productivity without causing production disruptions in the manufacture of the substrate, the aluminum content of the substrate should be as high as possible. In this case, the appropriate aluminum content of the substrate is 2 to 4% by weight. This method can be used to prepare starting materials for the production of final products, for example tubular blanks for pilgrim step rolling or for continuous plastic machining at low temperatures.

Resistive heating

For example, in industrial furnaces and consumer products, including resistive heating such as heaters, radiant heaters, flat irons, ovens, toasters, hair dryers, tumble dryers, dish dryers, electric kettles, car seat heaters, floor heaters, radiators and other similar products. There is also a need for the use of strips, wire rods or thin films having the aforementioned properties. The availability of materials with these product details results in the development of more efficient heat sources with longer lifetimes and / or higher operating temperatures and efficiencies.

Additional Applications

The alloys produced according to the invention can also be used in other high temperature application areas which require high oxidation resistance and good mechanical properties. For example, this alloy can be used in a heat exchanger or as a shroud. This alloy can also be used in other environments, such as in a reducing atmosphere. In this case, it may be desirable in some cases where the product must be pre-oxidized to ensure that the Al-containing oxide is stable and dense on the surface.

Claims (8)

The low Al austenitic base alloy was coated with one or more layers of high Al content alloys at temperatures between 100 ° C. and 600 ° C., so that the Al content of the final product was 4.5-12% by weight, preferably 5.5 A method for producing an austenitic alloy, characterized in that ~ 12% by weight. The method of claim 1, In weight percent, Ni: 20-70%, Cr: 15-27%, Al: 0-5%, Mo and / or W: 0-4%, Si: 0-2%, Mn: 0-3%, Nb: 0-2%, Y, Zr and / or Hf: 0 to 0.5%, Ti: 0-0.5%, At least one rare earth metal (REM): 0 to 0.1%, A method for producing an austenitic alloy, characterized in that a base alloy having a composition consisting of balance Fe and ordinary impurities is coated with one or more layers of a composition having a high Al content. The method according to claim 1 or 2, The at least one layer is a method for producing an austenitic alloy, characterized in that the aluminum. The method according to claim 1 or 2, The at least one layer is a method for producing an austenitic alloy, characterized in that the aluminum alloy. The method of claim 4, wherein The aluminum alloy is an austenitic alloy manufacturing method, characterized in that Al having 0.5 to 25% by weight of Si. The method according to any one of claims 1 to 5, Austenitic final products are in weight percent, C: 0-0.2%, N: 0 to 0.1%, Ni: 25-70%, Cr: 15-25%, Al: 4.5-12%, Mo and / or W: 0-4%, Si: 0-4%, Mn: 0-3%, Nb: 0-2%, Ti: 0-0.5%, Y, Sc, Zr and / or Hf: 0 to 0.5%, At least one rare earth metal (REM) such as Ce, La, Sm: 0-0.2%, A method for producing an austenitic alloy, characterized in that it has a composition consisting of balance Fe and ordinary impurities. An austenitic alloy having an Al content of 4.5 to 12% by weight, which is prepared by the method according to any one of claims 1 to 6. Use of the method according to any one of claims 1 to 6, which is used to prepare materials for use in high temperature applications such as support materials and catalytic heating of catalytic converters.

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