Method for manufacturing a carrier foil for a catalytic converter

Abstract

1. A method for producing a carrier foil for catalytic converters having an application temperature up to 900°C, which consists of an iron-chromium-aluminium alloy having the following contents in mass %: Cr 8-14%; Al 1-4%; Fe balance, as well as impurities resulting from melting, comprising casting the alloy into a block, hot rolling or forging the block into a slab with a thickness of 150-400 mm, and cooling the slab in the hot state to room temperature in air / oil / water or first charging the slab into a furnace installation in the temperature range 475°C-700°C and cooling to room temperature outside the furnace installation after a hot holding stage at a defined holding temperature of 475°C-700°C with a holding time of 0.5-100 hours.

Description

[Technical field]

[0001] The present invention relates to a method for producing a carrier foil for a catalytic converter. [Background technology]

[0002] Iron-chromium-aluminum alloys with a chromium content of more than 10% by weight and an aluminum content of more than >2% by weight are used as metal carrier foils for catalytic converters at application temperatures above 1000° C. Typically, the chromium content of these alloys is more than 18% by weight and the aluminum content is more than 4.5% by weight. Due to their alloy composition, these alloys have very good oxidation resistance at high temperatures (>1000° C.), but on the other hand, the high chromium and aluminum contents cause that brittle phases (so-called 475° C. embrittlement) can form during the production of cast blocks in hot forming processes into slabs, hot strips, cold strips and foils, if temperatures below about 500° C. occur in the process control. The brittle phases can lead to significant material destruction in conjunction with material stresses.

[0003] For catalytic converters to be used at maximum temperatures up to 900° C., the oxidation resistance of the metal support foil (foil thickness of about 50 μm) must be sufficiently good, which must exist up to this relatively low application temperature.

[0004] DE 10 2012 004 488 A1 discloses an iron-chromium-aluminium alloy having, in mass percent, 2.0-4.5% Al, 12-25% Cr, 1.0-4.0% W, 0.25-2.0% Nb, 0.05-1.2% Si, 0.001-0.70% Mn, 0.001-0.030% C, 0.0001-0.05% Mg, 0.0001-0.03% Ca, 0.001-0.030% P, max. 0.03% N, max. 0.01% S, balance iron and impurities resulting from normal melting, with improved heat resistance, lower chromium evaporation rate, and good processability. If necessary, the elements Y, Hf, Zr can be added to the alloy. Fields of use of the alloy are interconnector plates and / or structural components in further assemblies of solid oxide fuel cells, for example in particular in heat exchangers, as well as carrier foils and / or wire meshes in metallic exhaust gas catalytic converters.

[0005] DE 103 10 865 B3 describes the use of an iron-chromium-aluminium alloy with good oxidation resistance, having by weight 2.5-5.0% Al, 10-25% Cr and 0.05-0.8% Si, as well as the additives >0.01-0.1% Y and / or >0.01-0.1% Hf and / or >0.01-0.2% Zr and / or >0.01-0.2% cerium mischmetal (Ce, La, Nd), as well as impurities resulting from production, for components in diesel vehicles and two-stroke equipment, in particular in diesel and two-stroke engines. Structural components produced from said alloy have a length change of less than 4% at a metal thickness of 50 μm after annealing at 1100 ° C for 400 hours. In this case, carrier foils in metallic exhaust gas catalytic converters as well as components in exhaust gas purification systems can be regarded as structural members.

[0006] DE 101 57 749 A1 relates to an iron-chromium-aluminium alloy having a long service life, which contains, by weight, >2-2.6% aluminium and >10-20% chromium, as well as the additions 0.1-1% Si, max 0.5% Mn, 0.01-0.2% Y and / or 0.01-0.2% Hf and / or 0.01-0.3% Zr, max 0.01% Mg, max 0.01% Ca, max 0.08% C, max 0.04% N, max 0.04% P, max 0.01% S, max 0.05% Cu and max 0.1% Mo and / or W, the balance being iron and impurities resulting from production. The alloys can be used, for example, as heating elements for use in household appliances or as building materials for use in furnace construction. Additionally, the alloys can be used in the form of foils for use as carrier foils for catalytic converters.

[0007] The materials mentioned in the prior art are industrially produced as follows: The alloy is melted in a melting device, for example an arc melting furnace or an induction melting furnace, and then cast into blocks. The blocks are hot rolled into slabs, which are hot rolled into hot strips. The further forming process comprises several cold rolling stages with intermediate annealing from the hot strip into strips or foils. Between the individual hot and cold rolling stages, surface grinding steps and the separation and removal of the ends of the slabs are also carried out. The respective transport stages from the location of the rolling device are carried out in so-called hot transport, in which the material temperature must be kept above 500°C to above 700°C in order to suppress brittle phases. After hot transport, the material pieces are charged into a furnace installation at a temperature above 500°C and heated to the rolling temperature when they arrive at the device where the next rolling process is carried out. Even if there is a long waiting stage before the hot-formed pieces are further transported to the next process stage, they are kept at a higher temperature in the furnace installation for logistical reasons and transported to the next process location at a later time using hot transport. The individual process steps and the hot transport and recharging of the furnace system at temperatures above 500°C include the following stations and transports: Hot transport of cast blocks; charging said blocks into a furnace at above 500°C and heating them to rolling temperature; hot rolling said blocks into slabs; Charging the slab into a furnace at greater than 500°C and heating and holding at the higher hold temperature; hot transporting said slabs; charging the slab into a furnace at above 500°C and heating it to rolling temperature; hot rolling the slab into a hot strip; hot transporting the hot strip; charging the hot strip into a furnace at above 500°C; hot rolling the hot strip into a strip of specified initial dimensions; Cold rolling the strip, with a further intermediate annealing, and cold rolling into foil.

[0008] The hot rolling of the blocks into slabs may be replaced by a forging process if desired. A hot grinding process may also be used during the process sequence. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] DE 102012004488 A1 [Patent Document 2] German Patent No. 10310865 [Patent Document 3] DE 10157749 A1 Summary of the Invention [Problem to be solved by the invention]

[0010] The object of the present invention is to provide a method for producing carrier foils for catalytic converters having application temperatures below 900° C., which does not require the previously mentioned complex production processes, in particular hot transport.

[0011] Furthermore, the use of said methods for specific application cases should be protected. [Means for solving the problem]

[0012] The object of the present invention is to provide a carrier foil for catalytic converters having an application temperature of up to 900° C., the carrier foil having a content in mass % of Cr 8~14% Al 1-4% Fe balance and impurities resulting from melting 3. A method for producing said carrier foil, comprising the steps of: casting said alloy into a block; hot rolling or forging the blocks into slabs with a thickness of 150 to 400 mm; Cool the hot slab to room temperature in air / oil / water, or This problem is solved by the method, which involves first charging the steel into a furnace facility at a temperature range of 475°C to 700°C, and cooling to room temperature outside the furnace facility after a hot holding stage at a defined holding temperature of 475°C to 700°C with a holding time of 0.5 to 100 hours.

[0013] Advantageous further aspects of the method according to the invention are set out in the associated dependent claims. The elemental contents of Cr, Al, and Fe may be modified within the original range as follows: Cr 10~13% 9~13% 9~12% Al 1-4% 1-3.5% 2~3.5% 1.5~3% Fe balance, and impurities resulting from melting.

[0014] In addition, the following elements may optionally be provided in the alloy: Y up to 0.3% and / or Hf up to 0.3% and / or La up to 0.3% and / or Cerium up to 0.3%, where cerium can be present in the form of misch metal (Ce, La, Nd).

[0015] Furthermore, Zr element may optionally be further added to said alloy, where a content of more than 0 up to 0.5% by weight is conceivable.

[0016] With the method according to the invention, it is now possible to dispense with long holding stages in furnace installations at holding temperatures clearly above 500° C. for several hours or even days in the case of raw materials with an alloy composition of 8-14% by weight chromium and 1-4% by weight aluminum, the remainder iron and impurities. In the case of the manufacturing process according to the subject matter of the invention, in contrast to the prior art, slabs with a thickness dimension of 150-400 mm, preferably 150-250 mm, are placed in the hot state after the block-to-slab hot rolling process or the forging process directly in air / oil / water and cooled to room temperature or are charged into a furnace installation at a temperature of 475° C.-700° C. and cooled from the final rolling / forging temperature to a temperature of 475° C.-700° C. and held at a defined holding temperature of 475° C.-700° C. for a holding time of 0.5-100 hours until temperature equilibrium over the slab cross section. The slabs are subsequently removed from the furnace installation and further cooled in air / oil / water to room temperature.

[0017] Using this process, it is possible to dispense with complicated hot-holding processes (possibly with lengthy holding stages at holding temperatures significantly above 500° C.), thereby significantly simplifying the manufacturing process. Furthermore, the foil has sufficiently good oxidation resistance in oxidation tests at temperatures from 750° C. to about 900° C. for 400 hours, which meets the requirements in particular as a carrier foil for catalytic converters with a maximum application temperature of 750-900° C.

[0018] Furthermore, the use of the method according to any one of claims 1 to 7 for producing a carrier foil for a catalytic converter having an application temperature of 900° C. or less is claimed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Table 1 discloses the chemical composition in weight percent of exemplary batch 155408.

[0020] [Table 1]

[0021] Table 2 lists the preferred chemical composition range limits of alloys that may be selected for the manufacturing process of the present invention and for the uses described above.

[0022] [Table 2]

[0023] The above alloys may optionally contain selected contents of additional elements, such as yttrium and / or hafnium and / or lanthanum and / or cerium.

Claims

1. A carrier foil for catalytic converters having an application temperature of up to 900° C., the content in mass % being Cr 8-14% Al 1 to 4% Fe balance and impurities resulting from melting In the method for producing the carrier foil made of an iron-chromium-aluminum alloy having casting the alloy into a block; hot rolling or forging the blocks into slabs with a thickness of 150-400 mm; Cool the hot slab in air / oil / water to room temperature, or The process comprises first charging into a furnace facility in the temperature range 475° C.-700° C. and cooling to room temperature outside the furnace facility after a hot holding step at a defined holding temperature of 475° C.-700° C. and a holding time of 0.5-100 hours.

2. The content of the element in the alloy is Cr 9-13% Al 1.0-3.5% Fe balance and impurities resulting from melting The method of claim 1 , wherein the

3. The content of the element in the alloy is Cr 10-13% Al 2 to 3.5% Fe balance and impurities resulting from melting The method of claim 1 or 2, wherein the

4. The content of the element in the alloy is Cr 9-12% Al 1.3 to 3% Fe balance and impurities resulting from melting The method of claim 1 or 2, wherein the

5. The alloy may optionally further comprise the following elements: Y up to 0.3%, and / or Hf up to 0.3%; and / or La up to 0.3%, and / or Cerium up to 0.3% 5. The method according to claim 1 , wherein

6. The method according to any one of claims 1 to 5, wherein the element Zr is optionally added to the alloy in a content of more than 0.0% to 0.5%.

7. 7. The method according to claim 1, characterized in that the slab is rolled into a strip and foil by hot and cold rolling processes after cooling to room temperature and, if necessary, carrying out at least one heat treatment process of the strip or foil.

8. 8. Use of the method according to any one of claims 1 to 7 for producing carrier foils for catalytic converters having application temperatures below 900°C.

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