JPS6159361B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a honeycomb-shaped molded body made of metal. In recent years, the development of applications for porous inorganic materials has progressed rapidly, and the shapes of porous inorganic materials have become diverse, including pellets, beads, rings, and even honeycombs. These shapes are selected to be optimal depending on the application, but honeycomb shapes in particular have (1) low pressure loss;
It has advantages such as (2) large specific surface area, (3) ease of handling, and (4) low wear, so it seems to play a particularly important role in applications such as catalyst carriers and core materials for such carriers. I'm getting used to it. The most commonly used honeycomb-shaped bodies are (1) extruded ceramics, and (2) laminated metal flat plates and corrugated metal plates. However, it cannot be said that these molded bodies fully satisfy the characteristics required in the field of catalysts as described above. In other words, the catalyst carrier and the core material for the carrier must be (A) porous and have good adhesion to the coating agent and catalyst.
(B) It must have sufficient strength and be difficult to break. (C) It must be chemically stable and not affect the catalytic activity. However, in the case of the ceramic carrier mentioned in (1) above, , the heat treatment conditions to satisfy strength and the heat treatment conditions to satisfy porosity are contradictory,
Furthermore, in the case of (2), a metal carrier, a complicated pretreatment is required to enhance the adhesion of a coating agent, etc., and there is a lot of room for improvement in each case. The present invention has been made in view of these circumstances, and after repeated studies to provide a honeycomb-shaped molded body that has both the porosity of ceramics and the high strength of metal, the present invention has been developed. configuration has been reached.
That is, metal powder is used as the main material, at least an oxide of either colloidal silica or colloidal alumina is added thereto, kneaded, extruded through an extrusion die to obtain a honeycomb-shaped molded body, and dried and sintered. By going through the process of
It has now become possible to provide a porous, high-strength metal honeycomb. The metal powder used in the present invention is Fe powder, Al
powder, Cu powder, Ti powder, Zr powder, Ni powder, Cr powder, and various alloy powders, etc., and select the necessary one according to the application. In some cases, these may be used in combination. Colloidal silica and colloidal alumina that are blended into such metal powders function as binders, but more specifically, they can be used for network structures based on Si-O-Si or Al-O-Al. Therefore, the metal powder particles are held to form a metal skeleton, and a composite sintered body made of metal-O-Si-O or metal-O-A-O is formed by sintering. Therefore, the network structure provides high strength and a large number of voids are formed between the networks, successfully achieving the object of the present invention to simultaneously satisfy porosity and high strength. It was decided that it would be done. By the way, when carrying out extrusion molding of a honeycomb-shaped molded body, a kneaded product consisting only of the above two or three components may be used, but other components may also be blended as desired. Examples of such components include lubricants. The lubricant is used to reduce the extrusion resistance in the extrusion nozzle and make the molding process easier, such as CMC, stearic acid, talc,
Examples include polyethylene glycol. Further, other components include substances that disappear by combustion, ie, low-molecular to high-molecular organic substances. Since such organic substances disappear through combustion and improve porosity by leaving small voids behind, there is practically no limit to the types of organic substances that can be used. However, the blending amount should be suppressed to 20% by weight or less (hereinafter simply referred to as %) based on the metal powder. The reason is 20%
This is because if it exceeds the porosity due to burnout, the porosity becomes excessive, which not only causes deformation during sintering or a decrease in strength after sintering, but also reduces shape retention during the extrusion process. Next, it is preferable that the metal powder has a particle diameter that is about 2/3 or less of the slit thickness of the extrusion die. That is, in extrusion molding of a honeycomb shaped body, metal powder particles pass through an extrusion die in such a way that they are pressed against each other, but when particles larger than about 2/3 of the slit thickness are used,
Two or more particles could become stuck in the slit in parallel or in clusters, leading to clogging of the screw. On the other hand, it has been found that the fluidity of the kneaded product containing the above-mentioned components is greatly influenced by the particle size distribution of the metal powder, especially the content of small particle size powder. In other words, metal powder particles with a particle size of about 1/2 or more of the slit thickness account for 20% or less of the total metal powder, and metal powder particles with a size of about 1/5 or less of the slit thickness account for 20% or less of the total metal powder. It has been found that when the amount is 10% or more based on the powder, good fluidity is exhibited in the extrusion cylinder and extrusion die. The present invention is not limited to the extrusion molding machine model, extrusion conditions, etc., but the extrusion speed is 5 mm/
If the extrusion speed is less than 5 mm/sec, there is a strong tendency for surface defects such as hangnails and scratches to occur frequently, so it is recommended to obtain an extrusion speed of 5 mm/sec or more. However, in order to ensure such speed, it is desirable to increase the content of curable binder to make the kneaded material soft.
Under such conditions, as the extrusion speed increases, the extrusion pressure decreases, and the decrease in extrusion pressure deteriorates the shape retention of the extruded product, and the walls of the honeycomb deform and adhere tightly until the end of drying. Such inconveniences may occur. Therefore, it is desirable to always maintain the pressure applied to the inner surface of the extrusion die at 90 kg/cm ² or more, and in order to effectively control such conditions,
A plunger type extrusion molding machine is preferable to a screw type extrusion molding machine. The molded product that has been extruded is dried by heating, and then sintered. Although there are no particular restrictions on the sintering conditions, especially the sintering temperature and time, the sintering atmosphere is preferably selected in accordance with the following criteria. In other words, when using a honeycomb-shaped molded body in which metal powder is simply incorporated as an aggregate, such as iron powder or iron alloy powder, sintering in a non-oxidizing atmosphere is necessary to prevent deterioration of physical properties due to oxidation, etc. It is desirable to do so. On the other hand, when using Al powder or Mg powder, the atmosphere during or after sintering is made into an activating atmosphere, and the activation of the honeycomb surface is promoted through oxidation, carbonization, nitridation, sulfidation, etc. It is desired that the catalyst itself be catalyzed or used as a carrier to improve the adhesion of the catalyst. For example, when a honeycomb-shaped molded body using Al powder is sintered in a non-oxidizing atmosphere and then heated in humid air, Al on the surface of the molded body precipitates as Al(OH) ₃ . When heated in dry argon, Al(OH) ₃ is oxidized to γ-alumina,
The molded body itself exhibits excellent catalytic activity. Since the honeycomb-shaped molded body of the present invention is manufactured as described above, an extremely strong skeleton is formed by the metal powder, and a large number of micro voids are left inside, resulting in a highly porous structure. Demonstrated. Furthermore, the manufacturing method was extremely simple, and all of the intended objectives could be achieved. The blending ratio of colloidal silica and/or colloidal alumina is not limited in any way, but it is usually 5 to 50% of the metal powder.
The amount may be approximately % by weight, and may be appropriately determined in consideration of the size of the honeycomb-shaped molded body, the number of honeycomb cells, the slit width, the specific gravity of the metal powder, etc. Next, examples of the present invention will be shown. Raw materials having the composition shown in Table 1 were blended and kneaded, and extrusion molding and sintering were performed under the following conditions. (1) Extrusion molding machine: 100mmφ plunger type extruder (2) Extrusion pressure: 108Kg/cm ² (3) Extrusion speed: 25mm/sec (4) Size of molded product: 50mmφ, 100 cells/m ² (5) Drying conditions: 107°C x 24hrs (6) Sintering conditions: Temperature: 1128°C Time: 5hrs Atmosphere: Argon The formability and physical properties of the sintered product were as shown in Table 1. In addition, when a heat-softening binder was used instead of colloidal silica or colloidal alumina, the honeycomb structure was deformed during the sintering stage and the honeycomb structure collapsed, and no porosity was exhibited. In addition, the solid content of colloidal silica and colloidal alumina used is
They were 25% and 20%, respectively.

[Table] 〓〓〓

[Table] As shown in Table 1, the honeycomb-shaped molded body obtained by the present invention was not deformed during sintering and exhibited excellent porosity. 〓〓〓

Claims (1)

[Scope of Claims] 1. A metal honeycomb-shaped body, characterized in that a honeycomb-shaped body is obtained by extruding a kneaded mixture of metal powder and colloidal silica and/or colloidal alumina through an extrusion die, which is dried and then sintered. Method for manufacturing a molded object. 2. In claim 1, the maximum particle diameter of the metal powder is about 2/3 or less of the slit thickness of an extrusion die, and about 2/3 or less of the slit thickness of the extrusion die.
Particles with a particle size of 1/2 or more account for 20% or less of the total,
A method for producing a metal honeycomb-shaped molded body using a material containing 10% or more of the total metal particles having a size of about 1/5 or less of the slit thickness. 3. In claim 1 or 2, the metal honeycomb-shaped formed product is extruded so that the pressure applied to the inner surface of the extrusion die is 90 kg/cm ² or more and the linear velocity when passing through the die is 5 mm/sec or more. manufacturing method. 4. A method for manufacturing a metal honeycomb-shaped molded body according to any one of claims 1 to 3, wherein sintering is performed in a non-oxidizing atmosphere. 5. A method for manufacturing a metal honeycomb-shaped formed body according to any one of claims 1 to 3, wherein sintering is performed in an atmosphere that promotes activation of the honeycomb surface. 6. A method for producing a metal honeycomb-shaped formed body according to any one of claims 1 to 5, using a kneaded product containing colloidal silica and/or colloidal alumina containing an organic substance in metal powder. .