IN-SITU DIFFUSION ALLOYING AND PRE-OXIDATION ANNEALING IN AIR OF FE-CR-AL ALLOY CATALYTIC CONVERTER MATERIAL
A manufacturing method of metal substrate catalytic converter and the resulting product. In this method, a multiple layer aluminum and ferritic stainless steel composite material is first made by roll-bonding and then further processed to a final foil thickness. The composite foils are then fabricated to a honeycomb-like converter with air flow channels. The converter is then thermally treated at a high temperature during a necessary converter fabrication process. The monolithic FeCrAl alloy is then obtained in the converter by in-situ diffusion alloying with pre-oxide film on the surfaces. The resulted material has improved oxidation resistance and thermal dimension stability at a high temperature.
1 . A method for preparing a honeycomb-like structure having oxidation resistance and dimensional stability, comprising the steps of:
a) sandwiching a first layer of the first material between two layers of a second material to produce a multilayer composite;
b) compaction rolling the composite to a finished foil;
c) processing the finished foil with a flat foil into the honeycomb-like structure having channels for air flow;
d) heating the honeycomb-like structure in an air atmosphere at an annealing temperature so to produce a monolithic honeycomb-like annealed alloy foil structure with a pre-oxidized surface; and
e) cooling the structure to room temperature.
2 . The method as claimed in claim 1 , wherein the first metal material or the second metal material contains iron.
3 . The method as claimed in claim 1 , the first layer is an iron chromium material.
4 . The method as claimed in claim 1 , wherein the first layer is a Fe—Cr Alloy.
5 . The method as claimed in claim 1 , wherein the second material is aluminum.
6 . The method as claimed in claim 1 , wherein the second material is an aluminum alloy.
7 . The method as claimed in claim 1 , wherein the first material is selected from the group consisting of stainless steel 430, 434 and 446.
8 . The material as claimed in claim 5 , wherein the pre-oxidized surface is aluminum oxide.
9 . The honeycomb-like structure prepared according to claim 1 .
10 . A method for preparing a honeycomb-like structure having oxidation resistance and dimensional stability, comprising the steps of:
a) providing a first layer of a Fe—Cr alloy material;
b) sandwiching the first layer between at least two layers of aluminum or an aluminum alloy to produce a multilayer composite;
c) compacting the composite to a finished thickness metal composite foil;
d) processing the finished thickness metal composite foil the honeycomb-like structure having channels for air flow;
e) heating the honeycomb-like structure in an air atmosphere at an annealing temperature so to produce a monolithic honeycomb-like annealed alloy foil structure with a pre-oxidized surface; and
f) cooling the monolithic honeycomb-like annealed alloy foil structure to room temperature.
11 . The method of claim 10 , wherein the Cr content in the first layer is about 16 wt % to about 24 wt %.
12 . The method of claim 10 , wherein the Cr content is about 16 wt % to about 24 wt %.
13 . The method of claim 10 , wherein the first metal material is selected from stainless steel 430, 434 and 446.
14 . The method of claim 10 , wherein the annealing temperature is from about 900° C. to about 1,200° C.
15 . The method of claim 10 , wherein the period of time for heating is between about 10 minutes and about 120 minutes.
16 . The method of claim 10 , wherein the pre-oxidized surface is aluminum oxide.
17 . A product produced in accordance with the process of claim.
18 . A catalytic converter comprising a product produced according to the process of claim 11 .
19 . A process of making a ferrous metal catalytic substrate for a catalytic converter, comprising the steps of:
a) providing a first layer of a Fe—Cr alloy material;
b) sandwiching the first layer between at least two layers of aluminum or an aluminum alloy to produce a multilayer composite;
c) compacting the composite to a finished thickness metal composite foil;
d) processing the finished thickness metal composite foil the honeycomb-like structure having channels for air flow;
e) heating the honeycomb-like structure in an air atmosphere at an annealing temperature so to produce a monolithic honeycomb-like annealed alloy foil structure with a pre-oxidized surface; and
f) cooling the monolithic honeycomb-like annealed alloy foil structure to room temperature.
20 . The process of claim 19 , wherein the first material is FeCr and the second material is pure aluminum oxide.