ZA200506916B

ZA200506916B - Iron-chromium-aluminium alloy

Info

Publication number: ZA200506916B
Application number: ZA200506916A
Authority: ZA
Inventors: Heike Hattendorf; Ralf Hojda; Angelika Kolb-Telieps
Original assignee: Thyssenkrupp Vdm Gmbh
Priority date: 2003-03-11
Filing date: 2005-08-29
Publication date: 2006-06-28
Also published as: US20070110609A1; JP2006519929A; RU2005131433A; ES2445584T3; EP1601804A2; DE10310865B3; WO2004081247A2; UA81021C2; AU2004219941A1; DE112004000857D2; BRPI0409579B1; KR20050109545A; RU2341581C2; WO2004081247A3; EP1601804B1; MXPA05009519A; AU2004219941B2; BRPI0409579A; CA2529720A1

Description

1 PCT/DE2004/000454 @ Iron-chromium-aluminium alloy

The invention relates to the use of an iron-chromium-aluminium alloy having a good oxidation resistance.

In four-stroke engines the catalyst is nowadays the rule, but the development of catalysts for diesel and two-stroke engines is still in its infancy. In four-stroke engines, alloys are used that are similar to those described in EP-A 0387 670: comprising (in % by mass). 20-25% Cr, 5-8% Al, max. 0.01% P, max. 0.01% Mg, max. 0.5% Mn, max. 0.005% S, the remainder iron and unavoidable impurities as well as possible 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 the manufacture by traditional methods, i.e. the casting of the alloy followed by hot and cold forming, is very difficult with aluminium contents beneath 6% by mass and can no more be managed on an industrial scale with higher aluminium contents, alternative manufacturing methods have been developed.

Thus, US 5,366,1349, for example, describes a process, in which foils made of chromium-aluminium alloys are manufactured by coating a suitable iron-chromium steel on both sides with aluminium or aluminium alloys by roll-bonding. This composite is exclusively cold-rolled and finally homogenized in such a way that a homogenous structure is obtained.

Another method, in which the coating is applied by fire-aluminising, is described in DE-A 198 34 552. This foil has the following chemical composition (all data in % by mass); 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, remainder iron and process related impurities. Hitherto, foils made of this alloy have been used in four-stroke combustion engines.

From US-A 4,414,023 a hot formable, ferritic, stainless steel alloy is known which is resistant at higher temperatures to thermal cyclic oxidation and scale. The alloy comprises (in % by mass) 8.0-25.0% Cr, 3.0-8.0% Al, an addition of at least 0.002 to 0.05% cerium, lanthanum, neodymium and/or presodymium, 0.06 to 1.0% Mn. For increasing the time yield, small quantities of Zr and/or Nb are added. The alloy can be used for catalysts that can be used at higher operating temperatures.

AMENDED SHEET

: 2 PCT/DE2004/000454 ¢ WO 01/54899 describes the use of a dimensionally stable Fe-Cr-Al foil as carrier material for catalysts or resistance material or heat conductors. The carrier element has the following composition (in % by mass): 16-25% Cr, 2-4% Al, 0.1-3% Si, max. 0.5%

Mn, 0.01-0.3% Zr and/or 0.01-0.1% Se and/or Y, Hf, Ti, max. 0.01% Mg, max. 0.1% Ca, remainder iron and usual process-related impurities.

The aim of the invention is to provide an alloy for applications in the temperature range comprised between 250°C and 1000°C, having a sufficient oxidation resistance, which can also be easily manufactured on an industrial scale.

This aim is achieved by the characteristics of the first claim.

A preferred iron-chromium-aluminium alloy having a high oxidation resistance has the following composition (in % by mass) 2.5-5% Al and 13 to 21% Cr as well as alternative additions of: - >0.01t00.1% Y and > 0.01 to 0.1% Hf; - >0.01t00.1% Y and > 0.01 to 0.1% Hf and > 0.01 to 0.2% Zr; - > 0.01 to 0.2% cerium composition metal (Ce, La, Nd); - > 0.01 to 0.2% Zr and > 0.01 to 0.2% cerium composition metal (Ce, La, Nd) as well as production related impurities.

Surprisingly it has been found that aluminium contents of more than 5% are not required for diesel and two-stroke engines. 2.5 — 5.0% by mass are quite sufficient for ensuring a sufficient oxidation resistance in the temperature range comprised between 250°C and 1000°C, which is relevant here, as the examples given below show. Additions of reactive elements are indispensable here to ensure the oxidation resistance. Especially 0.01 t0 0.1% Y and/or > 0.01 to 0.1% Hf have proved suitable, wherein if both elements are present, their total may not exceed 0.15% by mass, as otherwise the positive effect of the oxidation resistance will be reversed. However, also additions of other reactive elements, which have an oxygen affinity, such as e.g. Zr, Ce composition metals and La can lead to positive effects with respect to the oxidation resistance of the alloy.

AMENDED SHEET

. 3 PCT/DE2004/000454 i Semi-finished products made of the alloy can be produced, after melting of the alloy, by ingot or continuous casting as well as by hot- and cold-forming with, if required, intermediate annealing operation(s).

The manufacture of a foil of 50 um or even 20 um thickness in a conventional manner is possible with this composition without any problems. The slabs can even be produced by the particularly economic continuous casting method, which at higher aluminium contents generally is associated with high losses.

Preferred applications of the alloy are: - components in exhaust gas systems of ship diesel engines, diesel and two- stroke engines of a motor vehicle (passenger car, truck) or motor cycle; - carrier foils in metallic exhaust gas catalysts of diesel and two-stroke engines; - structural elements in diesel engine heater plugs; - wire cloth and fleeces for exhaust gas purification systems of, for example, motor cycles, motorised scythes, lawn mowers and motor saws; - components for exhaust gas purification systems of fuel cells; - extruded wire for the surface coating of components used in exhaust gas systems of diesel and two-stroke systems; - heat conductors or resistance materials for the electric pre-heating of exhaust gas purification systems in diesel and two-stroke systems.

The subject of the invention will be explained in more detail by the following examples: (The examples Aluchrom ISE, Hf3 and Hf4 are comparison alloys and the examples

Aluchrom Hf1 and Hf2 represent the subject of the invention)

Chemical compositions % by mass ISE Hf Hf2 Hf3 Hf4

Ni | 019 |] o014 | 016 | 017 | 016

Mn | 025 | 028 | 015 | 011 | 021

AMENDED SHEET

4 PCT/DE2004/000454 @ Cc [ 003 [ 005 [ 002 [003 [ 007 0.002 0002 | 0002 | 0002 | 0002

Pp [001 0.009 0.013 0009 | 0012

Mg [0.008 0.009 0.009 0.009 0003 | 005 | 001 | 002 | 005 [vV__[_004 | 005 | 008 | 004 | 003 0.006 0.032 0.023 0.051 | 0.023 _N | 0004 | 0005 | 0004 0.002 | 0005 wf | |" 004 | 005 [| 003 [ 005

Y -— 0.03 <0.01 cerium comp. 0.015 -—- -— metal

Ce, La, Nd

The examples according to the invention were molten in the electric arc furnace, cast by continuous or ingot casting, hot rolled to a thickness of approximately 3 m and, with intermediate annealing operations, cold rolled to final thicknesses comprised between 0.02 and 0.05 mm on a stand comprising 20 rollers.

Oxidation test

Change in mass at 1100°C, foil thickness 50 pm : 8 TE Te RT SR ER A AUC a TR AST os an chan ns 3 oo : LL AL s ES Asli Hn eon a EE Ea a TR Rs AREAS ne Sy A SE TE en a TE

Lal A ST] spa a oe] NE

FAI a Ca IRE er a Se EN Rie om c nE 2 ETRY fo fe op Ts SPAR SF BEE SE CR x SESE | ede Aluchrom Hf 2

Tr Ei iN - _

SEW Ss andra Gi SE Ia te ys - yy so Sa A i a eG Ra an Se 0 50 100 150 200 250 300 aso 400 450 ageing time inh

As shown by the indicated examples, not only the Al content is of crucial importance, but also and over all the exact tuning of the reactive elements having an affinity to oxygen. Thus, for example, the inventive alloys Aluchrom Hft and Aluchrom Hf2, in spite of their comparatively low Al contents of approximately 3%, show an extremely

AMENDED SHEET

. 5 PCT/DE2004/000454 @ high oxidation resistance which is similar to that of the comparison alloys Aluchrom ISE and Aluchrom Hf4. In contrast thereto, Aluchrom Hf3, in spite of the high Al content of 5.36%, shows worse results which can be attributed to the too low Y content. Here, additions of Y and Ce composition metal therefore lead to a clearly improved oxidation resistance (cf. Aluchrom ISE and Aluchrom Hf4 as comparison).

Another important aspect of the manufacture of metallic catalyst carriers for diesel and two-stroke engines is the dimensional stability of the foil during the operating time. The change in length, which should not exceed 4%, if possible, is considered as relevant characteristic.

Dimensional stability

Change in length at 1100°C, 50 um foil thickness

LR LEN SED AAA EAE DS A STR PE CABINS TIE, Ti SLO A PH SP ES PS DL EO RE

Sa nities Ee ec ae

JER sve finan el EEE ee

EE A J A Bn [1 a TE] A A a A eT MRE OR ar 3 2 a ea on aa —+—Aluchrom ISE 8 BEN ha ras RG) TH 5 BE HE ee a 3 nn geht | =#=Aluchrom HF 1 $' ere ns mE NET av PRESSES] | => Aluchrom Hf 3 a FES SAEs GER en A aatedh Lo

Le ee , eee =

Speer ER es Sar Se eae ei sie esas] Aluchrom Hf 3 a Pes Ee ea 0 50 100 150 200 250 300 350 400 450 ageing time inh

Also here it becomes apparent that the inventive alloys Aluchrom Hf1 and Aluchrom Hf2 having an Al content of approximately 3% reach a dimensional stability of < 4%, as also the comparison alloys Aluchrom ISE and Aluchrom Hf4 having an Al content of > 5%.

Also in this case, the comparison alloy Hf3 having a comparatively high Al content of 5.36% but a too low Y content, does not meet the requirements, since the change in length of approximately 5% after 400 h is clearly too high.

AMENDED SHEET

. 6 PCT/DE2004/000454

Thus, it has been surprisingly found that with a suitable tuning of the reactive elements having an oxygen affinity, a dimensional stability as required for the construction of metallic catalysts can be obtained even with Al contents which remain clearly beneath 5%.

A cost efficient production thanks to the comparatively low Al content, by block, continuous or also strip casting while keeping the application specific parameters, is obtained as a result thereof.

AMENDED SHEET

Claims

7 PCT/DE2004/000454 ¢ New Claims

1. A use of an iron-chromium-aluminium alloy having a good oxidation resistance with which semi-finished products are produced, after melting of the alloy, by ingot or continuous casting or strip casting as well as by hot- and cold-forming with, if required, intermediate annealing operation(s), comprising (in % by mass)

2.5-5% Al, 14 to 19% Cr and 0.05 to 0.8% Si 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 as well as production related impurities, for components of diesel vehicles and two-stroke devices, in particular in diesel and two-stroke engines, which components are exclusively adapted for the use in the temperature range comprised between 250°C and 1000°C.

2. A use according to claim 1, characterized in that the alloy can be used as carrier foil in metallic exhaust gas catalysts.

3. A use according to claim 1 or 2 as component of exhaust gas purification systems, in which the substrate is made of wire.

4. A use according to one of the claims 1 through 3 as structural element in diesel engine heater plugs.

5. A use according to one of the claims 1 through 4 as extruded wire for the surface coating of components used in exhaust gas systems of diesel and two-stroke engines.

6. A use according to one of the claims 1 through 5 as heat conductor or resistance material for the electric pre-heating of exhaust gas purification systems of diesel and two-stroke engines.

7. A use of an alloy according to one of the claims 1 through 6 as component in exhaust gas purification systems of fuel cells. ) AMENDED SHEET

8 PCT/DE2004/000454

¢ 8. A use according to one of the claims 1 through 7 comprising (in % by mass) 2.5 to < 5% Al as well as additions of >0.01 to 0.1% Y and >0.01 to 0.1% Hf and

>0.01 t0 0.2% Zr.

9. A use according to one of the claims 1 through 8 comprising (in % by mass) 2.5 to 5% Al as well as additions of >0.01 to 0.2% cerium composition metal (Ce, La,

Nd).

10.A use according to one of the claims 1 through 9 comprising (in % by mass) 2.5 to 5% Al and additions of >0.01 to 0.2% Zr and >0.01 to 0.2% cerium composition metal (Ce, La, Nd).

11.A use according to one of the claims 1 through 10 comprising (in % by mass)

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.

12.A use according to one of the claims 1 through 11, characterized in that one or more of the elements Y, Hf, Zr, cerium composition metal (Ce, La, Nd) is partly or completely replaced 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.

13. A use according to one of the claims 1 through 12, characterized in that (in % by mass) the Al content is comprised between 2.5 and 4.5%, wherein the total content (in % by mass) of at least one of the elements Y, Hf, Zr, cerium composition metal (Ce, La, Nd), Sc, Ti, Nb, Ta, V and rare earths does not exceed 0.6%.

14. A use according to one of the claims 1 through 13, characterized in that (in % by mass) the Cr content is comprised between >17.5 and <19%.

15. A use according to one of the claims 1 through 14, characterized in that (in % by mass) the Y content is comprised between >0.02 and <0.08% as well as the Hf content is comprised between >0.02 and <0.06%. AMENDED SHEET

. 9 PCT/DE2004/000454 @ 16. A use according to one of the claims 1 through 15, in which components produced from the alloy, after an annealing at 1100°C during 400 h with a metal thickness of 50 yum, comprise a change in length of < 4%.

17. Use according to any one of claims 1 to 16, substantially as herein described and illustrated.

18. A new use of an iron-chromium-aluminium alloy as defined in claim 1, substantially as herein described. AMENDED SHEET