JPS61210186A - Method for forming porous metallic layer on surface of metallic body - Google Patents

Abstract

PURPOSE:To form a porous metallic layer on the surface of a metallic body by forming an Al brazing filler metal layer on the surface of the metallic body consisting of an Al alloy, etc. and coating metallic powder thereon in a layer state then heating the body in a non-oxidative atmosphere thereby brazing the metallic powder. CONSTITUTION:A heat exchanger or the like is manufactured of the brazable metal such Al or Al alloy in the stage of producing an apparatus such as heat exchanger having a surface layer which is excellent in heat transmittability. The Al brazing filler metal such as Al-Si, Al-Cu, Al-Zn or others is fixed in the layer state onto the surface thereof. The metallic powder of an Al alloy, stainless steel, etc., having 20-100 mesh grain size is coated alone or in combination with an F flux thereon by a melt plating method, thermal spraying method, etc. The quantitative relation among the powder metal, brazing filler metal and flux is made 100:5-40:10-30. The coating is heated for <=15min at 560-650 deg.C in an inert gaseous atmosphere of N2, etc., by which the metallic powder is brazed and the porous metallic layer having the excellent adhesiveness to the Al metallic body is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a porous metal layer on the surface of a metal body.

(Conventional technology) Conventionally, heat pipes, evaporators, condensers,
In heat exchangers, etc., a porous metal layer is applied to the surface of the metal body serving as the base material in order to improve the heat transfer performance on the boiling heat transfer surface, condensation heat transfer surface, or heat exchange heat transfer surface. It is being formed.

Methods for forming a porous metal layer on the surface of the metal body include, for example, a sintering method in which metal powder is heated and baked to solidify it, a machining method in which the surface of the metal body is mechanically made porous, and a plating method. Apply metal powder to the surface of the metal object! In addition to known powder plating methods, aluminum powder matrix components, specific aluminum metal bonding components, and specific aluminum soldering fluxes are made into a slurry in an inert liquid vehicle. There is a known brazing method (Japanese Patent Publication No. 7763/1983) in which a slurry is placed on an aluminum substrate and dried to form a dry metal powder coating, and then heated to a predetermined temperature and brazed. .

[Problem that the invention seeks to solve]

However, each of the former methods has the problem that process control is complicated and costs are high, and that it is not possible to form a thick porous metal layer.
In the latter brazing method, there is a problem in the adhesion between the porous metal layer formed by this brazing and the base material, and there are also problems in the process such as adjusting the viscosity when preparing the slurry. In addition to the above difficulties, there is a further problem in that the porosity of the porous metal layer formed on the surface of the base material is reduced by the brazing material used during manufacturing.

[Means for solving problems]

The present invention has been devised in view of these points of view, and has excellent adhesion between the surface of the metal body and the porous metal layer, and is also excellent in the perforation of the porous metal layer. The present invention provides a method of forming a porous metal layer on the surface of a metal body, which is advantageous from the viewpoint of the present invention.

However, in the present invention, an aluminum-based brazing material is fixed to the surface of a metal body to form a brazing material layer, and a metal powder or a mixture of this metal powder and flux is applied in a layer on the brazing material layer. , a method of forming a porous metal layer on the surface of the metal body by brazing metal powder onto the surface of the metal body by heating in a non-oxidizing atmosphere or a reducing atmosphere.

In the present invention, the metal body used as the base material is not limited to aluminum or aluminum-based alloys, but may be any metal that can be brazed, such as iron, stainless steel, or copper, and preferably aluminum or aluminum-based alloys. It is.

In addition, examples of the brazing material that is fixed to the surface of the metal body to form the brazing material layer include Al-8i series, AI-Ct
J series, Al-Zn series, Aj-8n series, Al-Pb series, A
There are various aluminum-based brazing materials such as l-8n-Pb type, and depending on the type of metal body and the type of metal powder that forms the porous gold F4 layer on the surface, it is possible to use one type or a mixture of two or more types. be selected and used as appropriate.

The means for forming the a-material layer by fixing the aluminum-based brazing material on the surface of the metal body can be selected as appropriate depending on the type of metal body and the type of brazing material. It is preferable to firmly adhere the brazing material layer to the surface.
For example, the metal body is aluminum and the brazing material is Al-8
In the case of an i-series brazing material, a method similar to a conventionally known cladding material manufacturing method, a thermal spraying method of thermally spraying the brazing material onto the surface of a metal body, a hot-dip plating method, etc. are preferred.

The amount of aluminum-based brazing material to be used is determined according to the required thickness of the brazing material layer, that is, the amount of metal powder to be used that is applied in a layer on the brazing material layer formed on the surface of the metal body. Although it varies depending on the type of brazing material, it is usually 5 to 40 parts by weight, preferably 10 to 20 parts by weight, per 100 parts by weight of metal powder per unit area.

On the brazing material layer thus formed on the surface of the metal body, a layer of metal powder or a mixture of the metal powder and fluorine-based flux is applied.

The metal powder used for this purpose is not particularly limited as long as it can be brazed onto the surface of a metal body, but preferably aluminum containing high purity or a small amount of copper, silicon, iron, etc. In addition to base metals, stainless steel, and the like, examples include ceramic powder that has been treated to enable brazing by methods such as metal plating. Only one type of these metal powders may be used, or two or more types may be used in combination.

In addition, regarding the particle size of this metal powder, the average particle size is usually 2
A range of 0 to 100 meshes, preferably 30 to 70 meshes, is used. If the same metal powder and brazing material and the same amount of brazing material are used, the porous yield will increase depending on the particle size, and if the same particle size is used, the wettability of the metal powder and the surface of the brazing material will increase. Porous purchase changes depending on tension, etc.

The flux to be used with the metal powder as necessary can be appropriately selected from conventionally known fluxes depending on the type of metal body, the type of metal powder, and the type of brazing material.
For example, if the metal body is aluminum or an aluminum alloy and an aluminum-based metal is used as the metal powder, potassium hexafluoroaluminate (K AlF2)
and aluminum fluoride (AlF2), mixtures of potassium hexafluoroaluminate, potassium tetrafluoroaluminate, and potassium fluoride (KF), and other products obtained from aluminum fluoride and potassium fluoride. Lithium fluoride (L i F), calcium fluoride (Ca
Additives such as F3), sodium fluoride (NaF), etc.
Fluorine-based fluxes such as those obtained by adding (usually 5% by weight or less) are preferred. When flux is used together with metal powder, the amount used is usually 10 to 30% by weight, and since the surface area changes depending on the particle size of the metal powder, the amount of flux used is varied within the above range.

By the way, the thickness of the porous metal layer formed on the surface of the metal body is determined by the thickness of the brazing material layer and the amount of metal powder used, and the thickness of the brazing material layer is determined by the amount of brazing material used. Furthermore, since the amount of brazing material used is determined by the amount of metal powder used, the thickness of the porous metal layer formed on the surface of the metal body can be adjusted by adjusting the amount of brazing material and metal powder used. I can do it. Therefore, when actually forming a porous metal layer on the surface of a metal body, the amount of metal powder and brazing material to be used should be determined from the desired thickness of the porous metal layer. .

Any method may be used to apply the metal powder or a mixture of the metal powder and flux on the brazing material layer in a layered manner as long as it can be applied in a layered manner.
For example, there is a method of applying the slurry with a solvent such as water or higher alcohol, or adding less than 1% camphor.
250-1.

To 700! There is a method of placing a plate formed under a pressure of J/ci.

After applying a layer of metal powder or a mixture of this metal powder and flux onto the brazing material layer in this way, the metal powder is brazed onto the surface of the metal body by heating in a non-oxidizing atmosphere or reducing atmosphere. .

Here, the non-oxidizing atmosphere or reducing atmosphere includes a nitrogen gas atmosphere, an inert gas atmosphere such as helium gas, a hydrogen gas atmosphere, etc., and a nitrogen gas atmosphere is preferable from the viewpoint of safety and cost. In addition, the heating conditions during brazing can be selected as appropriate depending on the type of metal body, brazing material, and metal powder used. For example, if the metal body is aluminum or an aluminum-based alloy and the metal powder is an aluminum-based metal, In that case, the temperature increase rate is 5 to 100℃
/1n. , preferably 40-b. Brazing at a temperature of 560-650°C, preferably 590-6
The temperature is 10° C. and the holding time is 0 to 15 minutes, preferably 1 to 3 minutes.

[Effect]

In the method of the present invention, a brazing material layer is formed on the surface of a metal body, and metal powder is applied in a layer on this brazing material layer, and brazing is sometimes performed by embedding the metal powder in the molten brazing material. This brazing material is caused to rise between the metal powders applied in layers by a so-called capillary phenomenon, thereby forming a porous metal layer.

〔Example〕

Hereinafter, the method of the present invention will be specifically explained based on Examples.

324 g/rd of AI-3i brazing material (A-4045) was fixed to the surface of the aluminum plate (A-3003) using the same method as the clad material manufacturing method, and a plate thickness of 1.2 m+ and cladding were attached to the surface of the aluminum metal body. A cladding material was formed in which a brazing material layer having a brazing ratio of 10% was formed.

On top of the brazing material layer of this cladding material, 32 to 60 meshes of aluminum powder (A-1100) (90 weights)
% and 75% by weight of 3AIF6 and 25Iffi% of A
A mixture of fluorine-based flux consisting of 1F2 and 10 weight Bk% was made into a slurry with water and applied to a thickness of 1 inch, and then heated at a heating rate of 50°C/1n in a nitrogen gas atmosphere. Brazing was performed at a temperature of 605° C. and a holding time of 3 minutes to form an aluminum porous metal layer with a thickness of 1 ml on the surface of the aluminum plate.

(Effects of the Invention) According to the method of the present invention, a brazing material layer is formed on the surface of a metal body, and metal powder is embedded in this brazing material layer to form a porous metal layer. The adhesion between this metal body and the porous metal layer is extremely good, and the porous metal layer! When forming the layer, the distance between the metal body and the metal powder is 12
The brazing material that adheres to each metal powder rises through the so-called capillary phenomenon and sticks to each other, so the minimum amount of brazing material required is sufficient, which not only saves the amount of brazing material but also reduces the amount of the formed porous metal layer. The porous device is also improved, and the manufacturing process is not as troublesome as the conventional method, which is also advantageous. In addition, compared to using the brazing material in powder form, the surface area of this brazing material is extremely small, causing less oxide film damage during heating and brazing, and reducing the amount of flux used. can be kept to a minimum.

Claims (4)

[Claims] (1) An aluminum-based brazing material is fixed on the surface of a metal body to form a brazing material layer, and a metal powder or a mixture of this metal powder and flux is applied in a layer on the brazing material layer, and a non-oxidizing atmosphere is applied. Alternatively, a method for forming a porous metal layer on the surface of a metal body, which comprises brazing metal powder onto the surface of the metal body by heating in a reducing atmosphere. (2) The method for forming a porous metal layer on the surface of a metal body according to claim 1, wherein the metal body is aluminum or an aluminum-based alloy. (3) The method for forming a porous metal layer on the surface of a metal body according to claim 1 or 2, wherein the metal powder is an aluminum-based metal. (4) The method for forming a porous metal layer on the surface of a metal body according to any one of claims 1 to 3, wherein the flux is a fluorine-based flux.