Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Patent
1991-03-26
1994-05-31
Epstein, Henry F.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
428116, 428188, 428593, 502527, B32B 312
Patent
active
053169972
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to a heat resisting structure to be used at a high environmental temperature. More particularly, the present invention relates to a heat resisting structure wherein stainless steel corrugated sheets, flat sheets, etc. are joined together with brazing filler metal to form a honeycomb-form structure and it is used, for example, for a catalytic converter to treat exhaust gas of an automobile engine or the like as a catalyst holding body to which catalyst is made adhered.
BACKGROUND OF THE INVENTION
A heat resisting structure wherein stainless steel corrugated sheets having alternating ridges and grooves formed by folding the sheet continuously and flat stainless steel sheets, etc. are joined together with nickel(Ni)-base brazing filler metal to form honeycomb-form structure is conventionally used. In such a conventional heat resisting structure, stainless steel corrugated sheets, flat sheets, etc. which are highly resistant to corrosion and heat are used as base metal and nickel(Ni)-base brazing filler metal which is also highly resistant to corrosion and heat is used to withstand a high environmental temperature. The heat resisting structure is formed into a roll-form by rolling up the corrugated sheet, flat sheet, etc. and joining together with nickel(Ni)-base brazing filler metal or formed into a laminated block by stacking the materials into many layers and joining together, and thus formed honeycomb-form structure is utilized as a catalyst holding body and for other various uses.
Now, in relation to the corrugated sheet, flat sheet, brazing filler metal, etc. of the heat resisting structure, the prior art will be examined in detail. First, as to the corrugated sheet, flat sheet, etc. constituting the base metal, those of austenitic stainless steel are used. Recently, those of ferritic stainless steel also are in use. As to the brazing filler metal, nickel(Ni)-base brazing filler metal is used generally by applying it to the entire surface. The brazing filler metal is provided over the entire surface between the corrugated sheet, flat sheet, etc. constituting the base metal by, for example, coating the entire surface, placing foil-like brazing filler metal between the sheets over the entire surface, or using a brazing sheet coated with brazing filler metal over the entire surfaces. Composition of brazing filler metal currently in use is, by weight, 0.1% C maximum, 7.0 to 8.0% silicon Si, 18.0% to 9.0% chromium Cr, 1.0 to 1.5% boron B, and the remainder is nickel Ni.
However, the following problems have been pointed out concerning the above-mentioned conventional heat resisting structure.
First, the heat resisting structure employing austenitic stainless steel corrugated sheets, flat sheets, etc. is excellent in oxidation resistance as well as high-temperature strength to withstand a high environmental temperature during the use. However, this heat resisting structure, when stress is applied during use at a high environmental temperature, sometimes form stress corrosion cracks in the corrugated sheets, flat sheets, etc. constituting the base metal, in some cases carbide is precipitated on grain boundaries of the austenitic portion of the base metal, where intergranular corrosion cracking occurs, and thus durability of the structure at a high environmental temperature is affected. In addition, there is a problem in cost due to the expensiveness of the material. To solve the problems in the heat resisting structure of austenitic stainless steel mentioned above, heat resisting structure wherein ferritic stainless steel corrugated sheets, flat sheets, etc. are used as the base metal has been developed.
Secondly, in the heat resisting structure employing stainless steel, particularly ferritic stainless steel corrugated sheets, flat sheets, etc., the state of elements of the alloy, so-called phase, of the corrugated sheets, flat sheets, etc. which are the base metal is different from that of nickel(Ni)-base brazing filler metal. Therefore, when nickel(Ni)-base
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patent: 5002923 (1991-03-01), Koshiba et al.
patent: 5026611 (1991-06-01), Usui et al.
patent: 5084361 (1992-01-01), Toyoda et al.
Matsuoka Katsunori
Toyoda Tetsuro
Epstein Henry F.
Showa Aircraft Industry Co., Ltd.
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