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Cr-Al-Steel for High-Temperature Application

a technology of cr-al-steel and high-temperature application, which is applied in the field of cr-al-steel for high-temperature application, can solve the problems of considerable deformation, mechanical weakness, and great disadvantage of conventional fe—cr-al-alloys, and achieve the effect of improving mechanical properties

Inactive Publication Date: 2008-09-04
SANDVIK INTELLECTUAL PROPERTY AB
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005]Therefore, it is an object of the present invention to provide an alloy of a ferritic stainless steel having elevated resistance to cyclic and continuous thermal load and oxidation at elevated temperatures.
[0006]It is an additional object of the present invention to provide a ferritic stainless steel that has improved mechanical properties for the use in applications with cyclic and continuous thermal load and oxidation at elevated temperatures such as, e.g., supporting material in converter applications, such as catalysts.

Problems solved by technology

Conventional Fe—Cr—Al-alloys have, however, a great disadvantage: they are mechanically very weak at high temperature, and tend, therefore, to be considerably deformed also at small stresses by virtue of, e.g., acceleration, changes of pressure, mechanical impacts or changes of temperature.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0057]Table 1 shows compositions of examined alloys. Example C and comparative example 1 were prepared in the conventional way by pyrometallurgy and hot working. From comparative example 1, 50 μm thick strips were also prepared via hot rolling and cold rolling. Comparative example 1 is an alloy that today is used as supporting material in catalytic converters. This material has sufficient oxidation resistance for this use. However, the mechanical strength thereof is low and is regarded to be the limiting factor of the service life of the entire device.

[0058]The very low ductility at room temperature (2% elongation at fracture) of the alloy according to example C entails that this alloy hardly can be manufactured in the form of thin strips. However, the same alloy has, as is seen in table 1, a very good high temperature strength, thus at 700° and 900° C. the ultimate strength, for instance, is approx. 100% higher than for comparative example 1. The oxidation resistance of example C a...

example 2

[0059]Table 1 shows compositions of examined alloys. Examples A and B and comparative examples 1 and 2 were prepared in the conventional way by pyrometallurgy and hot working. Then 50 μm thick strips of all alloys were also prepared via hot rolling and cold rolling. The alloys according to examples A and B are all sufficiently ductile at room temperature in order to be able to be cold-rolled to very thin strips of good productivity.

[0060]Examples D and E and comparative example 3 correspond to cold-rolled strips of alloy according to examples B and C and comparative example 2, respectively, which was coated by vaporization or sputtering with Al on both sides in such a quantity that the total content of Al corresponded to 5.5-6% (see table 3).

TABLE 3Thick-nessCoatedDesiredMeasuredSub-beforethickness oftotal con-coatingstratecoatingcoated Altent of AlthicknessExamplealloy[μm]alloy [μm][%][μm]DA5056EB50464.1ComparativeCf.50564.7example 3example2

[0061]The obtained thickness of Al was me...

example 3

[0062]Examples F and G and comparative example 4 have the same composition as the alloys according to examples D and E and comparative example 3 having been annealed at 1050° C. for 10 min with the purpose of providing an equalising of the content of Al in the material. The ductility of the material was determined by a bending test where the smallest bending radius that the material could be bent to without fracture was determined, see table 4.

TABLE 4SmallestResults ofDiffusion an-bendingtensile testingEx-nealing in H2radius withoutat 900° C.ampleComposition[min / 1050° C.]fracture [mm][Rm / MPa]FThe same as100.546example DGThe same as100.3881example ECom-The same as102.5could not beparativecomparativemeasured dueexampleexample 3to brittleness4

[0063]The smallest radius that the material was tested at was 0.38 mm. The alloys according to the invention have a ductility being superior to comparative example 4. The alloy according to comparative example 4 proved to be so brittle that this a...

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Abstract

The present invention relates to a product of ferritic stainless steel manufactured according to the process of this invention, which product has increased resistance to cyclic and continuous thermal load and oxidation at elevated temperatures and which has improved mechanical properties at said temperatures as well as use thereof in the form of wire, strip, foil and / or tube in high-temperature applications such as in catalytic converter applications, in heating and furnace applications and which has the following composition (in % by weight): less than 1% of Ni, 15-25% of Cr, 4.5-12% of Al, 0.5-4% of Mo, 0.01-1.2% of Nb, 0-0.5% of Ti, 0-0.5% of Y, Sc, Zr and / or Hf, 0-0.2% of one or more rare earth metals (REM) such as, for instance, Ce or La, 0-0.2% of C, 0-0.2% of N, with the balance iron and normally occurring impurities.

Description

[0001]The present invention relates to a product of ferritic stainless steel manufactured according to the process of this invention, which product has increased resistance to cyclic and continuous thermal load and oxidation at increased temperatures and which has improved mechanical properties at said temperatures as well as the use thereof in the form of wire, strip, foil and / or tube in high-temperature applications such as in catalytic converter applications, in heating and furnace applications.BACKGROUND [0002]Fe—Cr—Al-alloys have extensive use in the temperature range above 900° C. Thanks to the protective oxide on the surface, they resist cyclic and continuous thermal load and oxidation until the material is depleted of the oxide former, e.g., Al. The limiting factors for the manufacture and the service life of the entire device are the total content of Al and the mechanical strength.DESCRIPTION OF PRIOR ART [0003]Metallic high-temperature materials in, for instance, catalytic...

Claims

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Application Information

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IPC IPC(8): C22C38/18C22C38/06C22CC22C38/48
CPCC22C38/02C22C38/04C22C38/26C22C38/22C22C38/06C22C38/18C22C38/28
Inventor GORANSSON, KENNETHROSBERG, ANDREASWITT, EVA
Owner SANDVIK INTELLECTUAL PROPERTY AB
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