AU2004219941A1

AU2004219941A1 - Iron-chromium-aluminum alloy

Info

Publication number: AU2004219941A1
Application number: AU2004219941A
Authority: AU
Inventors: Heike Hattendorf; Ralf Hojda; Angelika Kolb-Telieps
Original assignee: ThyssenKrupp VDM GmbH
Current assignee: VDM Metals GmbH
Priority date: 2003-03-11
Filing date: 2004-03-08
Publication date: 2004-09-23
Anticipated expiration: 2024-03-08
Also published as: EP1601804A2; WO2004081247A2; AU2004219941B2; RU2005131433A; WO2004081247A3; BRPI0409579B1; RU2341581C2; DE112004000857D2; JP2006519929A; BRPI0409579A; ZA200506916B; KR20050109545A; DE10310865B3; ES2445584T3; US20070110609A1; CA2529720A1; MXPA05009519A; EP1601804B1; UA81021C2

Description

IN THE MATTER OF an Australian Application corresponding to PCT Application PCT/DE2004/000454 I, Gunhild Henley, of German-French Language Services, of 7/40 Batman Street, West Melbourne, Victoria 3003, Australia, do solemnly and sincerely declare that I am conversant with the English and German languages and am a competent translator thereof, and that the following is, to the best of my knowledge and belief, a true and correct English translation of the PCT Application filed under No. PCT/DE2004/000454. Date: 4 October 2005 SIGNATURE OF TRANSLATOR: WO2004/081247 PCT/DE2004/000454 1 TRANSLATION 5 Iron-Chromium-Aluminium Alloy The invention relates to an iron-chromium-aluminium alloy having good oxidation resistance. Although the catalytic converter is the rule in four-stroke-engines today, the development of 10 catalytic converters for Diesel and two-stroke engines is still in its beginnings. In four-stroke engines, alloys are used which are similar to those described in EP-A 0387 670: with (in % by weight) 20-25% Cr, 5-8 % Al, max. 0.01 % P, max. 0.01 % Mg, max. 0.5 % Mn, max. 0.005 % S, residual iron and unavoidable impurities and, if required, alloying elements, such as 0.03 - 0 08 % Y, 0.004 - 0.008% N, 0.02 - 0.04 %C, 0.035 - 0.07 % Ti, 0,035 - 0.07 % Zr. Since 15 production by traditional methods, namely conventional pouring of the alloy and subsequent hot and cold deformation, is very difficult where aluminium contents of below 6% by weight are concerned and in cases of higher aluminium contents is no longer workable in large-scale productions, alternative production methods have been developed. 20 US-PS 5.366.139, for instance, discloses a method whereby foils of iron-chromium aluminium alloys are produced by way of suitable iron-chromium steel being coated on both sides with aluminium oraluminium alloys by way of roll cladding. This composite metal is processed exclusively by cold deformation and is subjected to diffusion annealing to produce a homogeneous structure. 25 A further method whereby the coating is achieved by way of hot dip aluminizing is disclosed in DE-A 198 34 552. The latter foil has the following chemical composition (all details in % by weight): 18 - 25 % Cr, 4 - 10 % Al, 0.03 - 0.08 % Y, max. 0.01 % Ti, 0.01 - 0.05 % Zr, 0.01 - 0.05 % Hf, 0.5 - 1.5 % Si, residual iron and method-associated impurities. Foils 30 fabricated with this alloy were to date used in four-stroke-combustion engines.

WO2004/081247 PCT/DE2004/000454 2 It is the object of the present invention to produce an alloy for applications in the temperature range of 250 0 C to 1000 0 C having an adequate oxidation resistance which is also achievable in large scale productions. 5 The solution to the task set is provided by an iron-chromium-aluminium alloy having good oxidation resistance, with (in % by weight) 2.5 to 5.0% Al and 10 to 25 % Cr and 0.05-0.8 % Si as well as additions of> 0.01 to 0.1 % Y and/or > 0.01 to 0.1 % Hf and/or > 0.01 to 0.2% Zr and/or > 0.01 to 0.2% Cer misch metal (Ce, La, Nd) as well as production-associated 10 impurities. A preferred iron-chromium-alUminium alloy having good oxidation resistance has the following composition (in % by weight): 2.5 - 5% Al and 13 to 21% Cr as well as alternative additions of: 15 - > 0.01 to0.1 % Y and> 0.01 to0.1 %Hf; - > 0.01 % to 0.1 % Y and > 0.01 to 0.1 % Hf and > 0.01 % to 0.2 % Zr; - > 0.01 to 0.2 % Cer misch metal (Ce, La, Nd); - > 0.01 to 0.2 % Zr and > 0.01 to 0.2% Cer mixed crystal*' (Ce, La, Nd) 20 as well as production-associated impurities. Surprisingly, it has been found that, in Diesel engines and two-stroke engines, aluminium contents above 5 % are not required. 2.5 to 5.0 % by weight are quite sufficient to guarantee 25 an adequate oxidation resistance in the temperature range of 250 0 C to 1000 0 C which is of interest in this regard, as the examples presented below will show. Indispensable in this situation are the additions of reactive elements to guarantee the oxidation resistance. Particularly proven are 0.01 - 0.1 % Y and/or 0.01 - 0.1 % Hf, where, in the presence of both elements, the sum of both these elements must not exceed 0.15 % by weight, because at this ' Translated as per German original WO2004/081247 PCT/DE2004/000454 3 level the positive effect of the oxidation resistance will be reversed to a negative. However, also by adding other oxygen-affine reactive elements, such as for instance Zr, Ce MM and La, positive effects can be achieved in relation to the oxidation resistance of the alloy. 5 One method for the fabrication of semi-finished articles from this alloy is characterised in that the semi-finished article following melting of the alloy by way of ingot casting or continuous casting as well as hot and cold deformation may be required to undergo one (or more) intermediate annealing processes. 10 Advantageous embodiments of the method are described in the dependent claims. The production of a foil of 50p or even 20g thickness is possible in the conventional manner in such compositions. The slabs can even be produced by way of the particularly inexpensive continuous casting process which in the presence of higher aluminium contents is, as a rule, 15 connected with high losses. Preferred applications for this alloy are: - components in exhaust systems of Diesel engines in vessels, Diesel engines and two 20 stroke engines of motor vehicles (cars, trucks) or motorbikes; - substrate foils in metallic catalytic converters of Diesel engines and two-stroke engines; 25 - components in Diesel engine glow plugs; - knitted metal fabrics and mats for exhaust cleaning systems used in for instance motorcycles, brush cutters, lawn mowers and power saws; 30 - components for exhaust cleaning systems for fuel cells; WO2004/081247 PCT/DE2004/000454 4 - spraying wires for surface coatings of components employed in exhaust systems of diesel and two-stroke systems; 5 - heating conductors or resistance materials for electrical preheating of exhaust cleaning systems in Diesel and two-stroke systems. The subject of the invention is described in greater detail in the following examples. 10 (Aluchrom ISE, Hf3 and Hf4 represent comparative alloys and Aluchrom Hfl and Hf2 are the subject of the present invention). Chemical compositions Chemische Zusammensetzungen Element I Aluchrom Aluchromrn Aluchrom Aluchrom Aluchrom Masse% ISE Hf 1 Hf2 Hf3 Hf4 Cr 20,45 17L25 18,20 21,05 20.15 NI 0,19 0j14 0,16 0,17 0,16 Mn 0,25 0,28 0,15 0,11 0,21 SI 0,43 0.54 0r29 0,30 0,22 I, 0,01 < 001 <001 < 0.01 0.01 Cu 0,03 0,05 0,02 0,03 0,07 S 0,002 0,002 0,002 0,002 0,002 P 0,011 0009 0,013 0.009 0,012 A] 5,27 2,78 3,30 5,36 5,70 Mg 0,008 0,004 0,009 0,009 0,009 Zr 0,003 0,05 0,01, 0,02 0,05 V 0,04 0,05 003 0,04 0,03 C 0,006 0,032 0,023 0,051 0.023 N 0,004 0,005 0,004 0,002 0,005 Hf - 0.04 0,05 0,03 0,05 Y - 0,03 0,05 < 0,01 0,06 Cer MM 0,015 - (Ce, La, Nd) 15 The examples in accordance with the invention were produced by melting in the electric arc furnace, continuous casting or ingot casting, hot rolling to a thickness of about 3mm, with WO2004/081247 PCT/DE2004/000454 5 intermediate annealing at end thicknesses of 0.02 to 0.05 and cold rolling on a 20 roller scaffold. Oxidation test 5 Weight change at 1 100°C, foil thickness 50 p Massenlnderung boi I10C, Follendicke 50pm Aludira, 1M D SO 900 150 200 260 300 350 400 40 A nExposure time in hHF 70-?.W 1 11r M 0 0 ISO 200 20 300 350 400 460 AMInlgorungszso fn, h 4' Exposure time in h Weight change in % 10 As the examples show, besides the Al content, the exact tuning of the oxygen affine reactive elements is of predominant importance. For instance, the alloys according to the present invention, Aluchrom Hfl and Aluchrom Hf2, in spite of their comparatively low Al-content of around 3%, show an extremely good oxidation resistance, which is similar to the comparative alloys Aluchrom ISE and Aluchrom Hf4. By comparison, Aluchrom Hf3, in 15 spite of its high Al- content of 5.36%, has lower values which can be attributed to the Y content being too low. In this instance therefore additions of Y or Ce MM result in a markedly improved oxidation resistance. (compare Aluchrom ISE and Aluchrom Hf4). A further important aspect for the construction of metallic catalytic converter substrates for 20 Diesel engines and two-stroke engines is the dimensional stability of the foil during the useful life of the foil. A respective characteristic feature in this regard is the linear deformation which should, if possible, not exceed 4 %.

WO2004/081247 PCT/DE2004/000454 6 Dimensional Stability 5 Linear deformation at 1100°C, 50 p foil thickness ingenindorung bel 11006C, 50pm Follendicke 4 ~2 Exposureutime in [h LiaAri defrmtioiF Alchrom Ht and A• .luchrom H , ti 0 50 400) 1SO 200 250 0 300 M 400 4W0 Austagerungszelt tn c t cExposure time in mh e Linear deforation in % 10 This also shows that the alloys in accordance with the present invention, Aluchrov Hfl and Aluchrom Hf2, having an al content of around 3 %, achieve a dimensional stability of < 4% as do the comparative alloys Aluchrom ISE and Aluchron H having an al content of> 5%. 15 Also in this case, in spite of their comparatively high Al content of 5.36 % but too low a Y content, the comparative alloy Aluchromn HO does not meet the requirements, since the linear deformation after 400 h, being about 5 %, is clearly too great. Thus it is surprisingly found that with a suitable tuning of the oxygen-affine reactive 20 elements, even where Al contents clearly below 5 % are present, a dimensional stability necessary for the production of metallic catalytic converters can be achieved.

WO2004/081247 PCT/DE2004/000454 7 A cost-effective production, based on the comparatively low Al contents, by way of ingot casting, continuous casting or even strip casting whilst observing the application-specific parameters is thus achieved.

Claims

2. The alloy in accordance with Claim 1, with (in % by weight) 2.5 to < 5 % Al and 13 to 21% Cr as well as additions of> 0.01 to 0.1% Y and > 0.01 to 0.1 % Hf.
3. The alloy in accordance with Claim 1, with (in % by weight) 2.5 to < 5 % Al and 15 13 to 21% Cr as well as additions of >0.01 to 0.1 % Y and > 0.01 to 0.1% Hf and > 0.01 to 0.2 % Zr.
4. The alloy in accordance with Claim 1 with (in % by weight) 2.5 to 5 % Al and 13 to 21 % Cr as well as additions of> 0.01 to 0.2 % Cer misch metal (Ce, La, Nd). 20
5. The alloy in accordance with Claim 1, with (in % by weight) 2.5 to 5 % Al and 13 to 21 % Cr as well as additions of> 0.01 to 0.2 % Zr and > 0.01 to 0.2 % Cer misch metal (Ce, La, Nd). 25 6. The alloy in accordance with any one of Claims 1 to 5 with (in % by weight) max. 0.06 % C, max. 0.6 % Si, max. 0.6 % Mn, max. 0.04 % P, max. 0.01 % S, max. 0.02 % N, max. 0.1 % Ti and in total max. 0.5 % Nb, Mo, Cu and/or W. WO2004/081247 PCT/DE2004/000454 9
7. The alloy in accordance with any one of Claims 1 to 6, characterised in that one or more of the elements Y, Hf, Zr, Cer mixed crystal *2 (Ce, La, Nd) is substituted in part or in full by one or more of the elements Sc, Ti, Nd, Ta, V and/or one or more of the elements of the rare earth metals. 5
8. The alloy in accordance with any one of Claims 1 to 7, characterised in that (in % by weight) the Cr content is between 14 and 19 % and the Al content between 2.5 and 4.5 %, wherein the total content (in % by weight) of at least one of the elements Y, Hf, Zr, Cer mixed crystal (Ce, La, Nd), Sc, Ti, Nb, Ta, V and rare 10 earth metals does not exceed 0.6%.
9. The alloy in accordance with any one of Claims 1 to 8, characterised in that (in % by weight) the Cr content is between > 17.5 and < 19 % and the Al content between > 3 and < 4%. 15
10. The alloy in accordance with any one of Claims 1 to 9, characterised in that (in % by weight) the Y content is between > 0.02 and < 0.08 % and the Hf content between > 0.02 and < 0.06 %. 20 11 . The alloy in accordance with any one of Claims 1 to 10, characterised in that components fabricated from the alloy after annealing at 1100 0 C during 400 h at a metal thickness of 50i show a linear deformation of < 4 %.
12. A method for the fabrication of semi-finished articles from the alloy in accordance 25 with any one of claims I to 11, characterised in that the semi-finished articles following melting of the alloy are produced by way of ingot casting, continuous casting or strip casting as well as hot and cold deformation and including (an) intermediate annealing process(es) as required. 2 translated as per German original WO2004/081247 PCT/DE2004/000454 10
13. A use of an alloy in accordance with any one of Claims 1 to 11 for a component in Diesel vehicles and two-stroke devices, in particular in Diesel and two-stroke engines. 5 14. The use in accordance with Claim 13, characterised in that the alloy is employable as substrate foil in metallic catalytic exhaust converters.
15. The use in accordance with Claim 13 as a component of exhaust cleaning systems where the substrate is made of wire. 10
16. The use in accordance with Claim 13 as a component in Diesel engine glow cells.
17. The use in accordance with Claim 13 as spraying wire for surface coatings of components employed in exhaust systems of Diesel or two-stroke engines. 15
18. The use in accordance with Claim 13 as heating conductors or resistance materials for electrical preheating of exhaust cleaning systems of Diesel or two-stroke engines. 20 19. The use of an alloy in accordance with any one of Claims 1 to 11 as a component in exhaust cleaning systems of fuel cells.