Metal honeycomb body for exhaust gas purification catalyst and method for producing the same

A metal honeycomb body for an exhaust gas purification catalyst, said honeycomb body comprising:

• a plurality of alternate layers of flat metal foil and corrugated metal foil, with adjacent layers in contact with one another, said flat metal foil and said corrugated metal foil being ferrite heat-resistant high alloy steel;
• said flat metal foil and said corrugated metal foil having a width-wise direction perpendicular to a rolling direction of said foils;
• said flat metal foil and said corrugated metal foil having a surface roughness specified by an arithmetical mean deviation Rac within a range of 0.001 to 0.3 μm measured in the direction perpendicular to the rolling direction of said metal foils;
• contact portions between said flat metal foil and said corrugated metal foil bonded by solid phase diffusion bonding.

A metal honeycomb body for an exhaust gas purification catalyst, said honeycomb body comprising:

• a plurality of alternate layers of flat metal foil and corrugated metal foil, with adjacent layers in contact with one another, said flat metal foil and said corrugated metal foil being ferrite heat-resistant high alloy steel;
• said flat metal foil and said corrugated metal foil having a wide-wise direction perpendicular to a rolling direction of said metal foils;
• said flat metal foil and said corrugated metal foil having a surface texture specified by a number of peaks PPI at least 100 per inch length measured in the direction perpendicular to the rolling direction of said metal foils;
• contact portions between said flat metal foil and said corrugated metal foil bonded by solid phase diffusion bonding.

A metal honeycomb body for an exhaust gas purification catalyst, said-honeycomb body comprising:

• a plurality of alternate layers of flat metal foil and corrugated metal foil, with adjacent layers in contact with one another, said flat metal foil and said corrugated metal foil being ferrite heat-resistant high alloy steel;
• said honeycomb body having a cylindrical shape, a length, a center axis, an outer periphery, a radius defined between the center axis and the outer periphery, a gas entry side at a first end of the cylindrical shape and a gas exit side at a second end of the cylindrical shape;
• said flat metal foil and said corrugated metal foil having a width-wise direction perpendicular to a rolling direction of said metal foils;
• said flat metal foil and said corrugated metal foil having a surface texture comprising a surface roughness specified by an arithmetical mean deviation Rac measured in the direction perpendicular to the rolling direction of said metal foils within a range of 0.001 to 0.3 μm;
• a portion of contact portions between the flat metal foil and the corrugated metal foil not bonded to one another at least at one position in said honeycomb body defining at least one unbonded portion;
• remaining portions of the contact portions between the flat metal foil and the corrugated metal foil bonded by solid phase diffusion bonding;
• said at least one unbonded portion located at a distance of at least ½ the radius from the center axis to the outer periphery of said cylindrical shaped metal honeycomb body and extending from at or near the gas exit side, as a start point, toward the gas entry side in a direction of the center axis for a distance of {fraction (9/20)} to {fraction (9/10)} of the length of the cylindrical shaped metal honeycomb body and covering at least one circumferential turn with respect to the cylindrical shape of the metal honeycomb body.

A method of producing a metal honeycomb body for an exhaust gas purification catalyst, said method comprising the steps of:

• winding a flat metal foil and a corrugated metal foil forming a cylindrical shaped honeycomb body, said flat metal foil and said corrugated metal foil made of a ferrite heat-resistant high alloy steel;
• said cylindrical shaped honeycomb body having a length, a center axis, an outer periphery, a radius defined between the center axis and the outer periphery, a gas entry side at a first end of the cylindrical shaped honeycomb body and a gas exit side at a second end of the cylindrical shaped honeycomb body;
• during said winding, applying a diffusion-preventing agent at one or more positions at contact portions between the flat metal foil and the corrugated metal foil, said diffusion-preventing agent applied at a distance of at least ½ the radius from the center axis to the outer periphery of said cylindrical shaped honeycomb body and extending from at or near the gas exit side, as a start point, toward the gas entry side in the direction of the center axis for a distance of {fraction (9/20)} to {fraction (9/10)} of the length of the cylindrical shaped honeycomb body and covering at least one circumferential turn with respect to the cylindrical shape of the honeycomb body;
• providing said flat metal foil and said corrugated metal foil having a width-wise direction perpendicular a rolling direction of the foils with a surface roughness specified by an arithmetical mean deviation Rac measured in the direction perpendicular to the rolling direction of the foils within a range of 0.001 to 0.3 μm;
• heat-treating the cylindrical shaped honeycomb body at a treatment temperature of 1,100 to 1,250° C. for a treatment time of 30 to 90 minutes in a degree of vacuum of 3×10−4 to 5×10−5 Torr at time of arrival at said heating-treating temperature for solid phase diffusion bonding.