JP2004205059A - Method of manufacturing high erosion resistance heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a heat exchanger having high temperature oxidation resistance and erosion resistance by using a relatively inexpensive ferrite and austenitic stainless steel plates. <P>SOLUTION: The parts of the heat exchanger are formed by bending the ferrite or austenitic stainless steel plates. Next, the surfaces of the parts are coated with a phosphorus-containing nickel alloy film 3 by electroless deposition. Next, these parts are assembled and put in a vacuum furnace, and the phosphorus-containing nickel alloy is diffused from the surface to the inside of the parts to form a nickel-enriched layer 4 on the surfaces thereof. Also, the coated phosphorus-containing nickel alloy film 3 is fused, and the heat exchanger assembly is cooled to fixedly braze the parts to each other with the phosphorus-containing nickel alloy as a brazing material. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a heat exchanger that requires high-temperature oxidation resistance and high corrosion resistance.
[0002]
[Prior art]
Austenitic stainless steel is used for evaporators, reformers, high-temperature regenerators, fuel superheaters used as heat exchangers for fuel cells, heat exchangers for MGTs (recuperators, etc.), and heat exchangers requiring corrosion resistance. A plate of steel (18Cr-8Ni stainless steel as an example) was used, and an amorphous nickel brazing foil was interposed between the components, and the components were brazed and fixed.
Further, instead of the amorphous nickel-based brazing material, nickel-based brazing powder may be applied to the surface of a stainless steel plate via a binding material, thereby brazing and fixing the components.
[0003]
[Problems to be solved by the invention]
For a heat exchanger having high-temperature oxidation resistance and corrosion resistance, it was necessary to use a higher-grade austenitic stainless steel plate and to use an expensive amorphous sheet brazing material. This has led to increased product costs. Therefore, the present invention uses a relatively inexpensive ferritic or austenitic stainless steel sheet and has high-temperature oxidation resistance and corrosion resistance equal to or higher than that of a higher-grade austenitic stainless steel sheet. It is an object to make a heat exchanger (called a heat exchanger) at low cost.
[0004]
[Means for Solving the Problems]
According to the first aspect of the present invention, the surface of each component for a heat exchanger made of stainless steel is coated by electroless plating with a phosphorus-containing nickel alloy, and the surface of each component is coated with a phosphorus-containing nickel alloy film (3). Forming, and
Then combining the components to form a heat exchanger assembly;
Next, the heat exchanger assembly is placed in a high-temperature vacuum furnace, and the phosphorous-containing nickel alloy is diffused from the surface of each part to the inside to form a nickel-enriched layer (4) on the part surface, and the coated phosphorous is added. Melting the containing nickel alloy film (3);
Then, by cooling the heat exchanger assembly, a step of brazing and fixing the phosphorus-containing nickel alloy remaining on the surface between the contact portions of the components as a brazing material,
This is a method for producing a high corrosion resistant heat exchanger comprising:
[0005]
The present invention described in claim 2 is based on claim 1,
The phosphorus-containing nickel alloy is a method for manufacturing a highly corrosion-resistant heat exchanger containing 4 to 15% by weight of phosphorus.
[0006]
According to a third aspect of the present invention, in the first or second aspect,
The stainless steel plate (5) is bent to form the heat exchanger parts of the fin (1) and the plate (2a), and then the phosphorus-containing nickel alloy film (3) is formed on the surface of the high corrosion resistant heat exchanger. It is a manufacturing method.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of a method for manufacturing a high corrosion resistant heat exchanger of the present invention will be described with reference to the drawings.
1 to 3 are explanatory diagrams sequentially showing each step of the method for manufacturing a high corrosion resistant heat exchanger of the present invention.
The heat exchanger of this example has, as an example, a pair of dish plates having inlets and outlets at both ends overlapped in the opposite direction, and inner fins are arranged inside, or a pair of inner fins as shown in FIG. The grooved plates were overlapped so that the groove bottoms faced each other, and inner fins were arranged inside. In this example, first, as shown in FIG. 1A, a fin is used as an example to form a corrugated or offset fin, and a tube is formed by raising the outer periphery, using relatively inexpensive ferritic and austenitic stainless steel plates. Plate 2a is bent.
[0008]
Next, the surface of the stainless steel 5 is coated with a phosphorus-containing nickel alloy by electroless plating alone for each heat exchanger component, and the surface of the component is coated with a phosphorus-containing nickel alloy film as shown in FIG. Form 3 As the phosphorus-containing nickel alloy at this time, for example, a phosphorus-containing nickel alloy having a phosphorus content of about 4 to 15% by weight and a balance of nickel can be used. That is, it is a so-called medium phosphorus type nickel alloy or high phosphorus type nickel alloy.
Note that SUS430, SUS436J1L, or the like can be used as the ferritic stainless steel sheet, and SUS304, SUS316, or the like can be used as the austenitic stainless steel sheet. The melting points of the former are about 1510 ° C. to 1532 ° C., and those of the latter are about 1400 ° C. to 1420 ° C.
[0009]
In the electroless nickel plating, nickel metal is precipitated from nickel ions by a reducing agent such as sodium diphosphate. As one example of the composition of the plating solution, 20 g of nickel sulfate, 25 g of sodium diphosphate, 25 g of lactic acid, The temperature of the plating solution can be set to 90 ° C. by using 25 g, 3 g of propion, and a small amount of a lead-based stabilizer. Then, as shown in FIG. 1, a phosphorus-containing nickel alloy film 3 of 25 to 40 μm can be formed.
[0010]
The components for such a heat exchanger are assembled as shown in FIG. 2A, and the heat exchanger assembly (2) is placed in a high-temperature vacuum furnace. FIG. 2B is an enlarged view of the main part. Then, the phosphorus-containing nickel alloy is diffused from the surface of each component to the inside to form a nickel-enriched layer 4 on the surface as shown in FIG. The temperature in the furnace is further increased to melt the phosphorus-containing nickel alloy coating 3 coated on the surface of each component, to hold the phosphorus-containing nickel alloy between the contact portions of each component, and then to assemble the heat exchanger (2) Is cooled to form a braze fillet 4a of the phosphorus-containing nickel alloy between the components, and brazed and fixed.
The melting temperature of this phosphorus-containing nickel alloy is 880 ° C. to 1100 ° C.
[0011]
In this way, by using the relatively inexpensive stainless steel plate 5 and forming the nickel-enriched layer 4 on the surface thereof and brazing the components with a phosphorus-containing nickel alloy, high-temperature oxidation resistance and corrosion resistance are obtained. Can be completed.
[0012]
[Action and Effect of the Invention]
The method for manufacturing a high corrosion resistant heat exchanger of the present invention comprises coating the surface of each heat exchanger component made of stainless steel with a phosphorus-containing nickel alloy film 3 by electroless plating, and then heating the heat exchanger assembly to a high temperature. In a vacuum furnace, the nickel alloy containing phosphorus is diffused from the surface of each component to the inside to form a nickel-enriched layer 4 on the surface. At the same time, the coated phosphorus-containing nickel alloy film 3 is melted in a vacuum furnace. Then, the heat exchanger assembly is cooled to braze and fix a nickel alloy containing phosphorus as a brazing material between the contact portions of the components.
Therefore, the nickel-enriched layer 4 can be formed and brazed by the phosphorus-containing nickel alloy film 3 coated by the electroless plating, so that it is relatively easy to manufacture and a high-quality, high-corrosion-resistant heat exchanger is inexpensive. Can be manufactured.
That is, expensive amorphous nickel brazing, which has been conventionally used as a brazing material for stainless steel plates, is not required.
[0013]
In addition, a uniform phosphorus-containing nickel alloy film 3 can be coated on the surface of each component without causing uneven coating unlike the case of using a nickel-based solder powder. This results in high quality.
Moreover, by diffusing the phosphorus-containing nickel alloy on the surface of the component in the vacuum furnace and easily forming the nickel-enriched layer 4 thereon, a heat exchanger having high corrosion resistance and high-temperature oxidizing property not existing in the original stainless steel. It becomes.
[0014]
In the above configuration, a nickel alloy containing 4 to 15% by weight of phosphorus can be used as the phosphorus-containing nickel alloy.
In this case, a heat exchanger having higher corrosion resistance and higher temperature oxidation properties is obtained.
In the above configuration, a stainless steel plate is bent to form a heat exchanger component such as a fin and a plate in advance, and then a phosphorus-containing nickel alloy film 3 can be formed on the surface thereof.
In this manner, the surface of each component is uniformly coated with the phosphorous-containing nickel alloy film 3, and the nickel-enriched layer 4 is easily formed on the surface of the component by melting and solidifying it. As a result, it is easy to integrally fix the components.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a first step of a method for manufacturing a high corrosion resistant heat exchanger of the present invention.
FIG. 2 is an explanatory view showing a second step of the manufacturing method.
FIG. 3 is an explanatory view showing a third step of the manufacturing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fin 2 Heat exchanger assembly 2a Plate 3 Phosphorus-containing nickel alloy film 4 Nickel enrichment layer 4a Braze fillet 5 Stainless steel plate

Claims (3)

A step of coating the surface of each component for a heat exchanger made of stainless steel by electroless plating with a phosphorus-containing nickel alloy, and forming a phosphorus-containing nickel alloy film (3) on the surface of each component;
Then combining the components to form a heat exchanger assembly;
Next, the heat exchanger assembly is placed in a high-temperature vacuum furnace, and the phosphorous-containing nickel alloy is diffused from the surface of each part to the inside to form a nickel-enriched layer (4) on the part surface, and the coated phosphorous is added. Melting the containing nickel alloy film (3);
Then, by cooling the heat exchanger assembly, a step of brazing and fixing the phosphorus-containing nickel alloy remaining on the surface between the contact portions of the components as a brazing material,
A method for producing a high corrosion resistant heat exchanger comprising: In claim 1,
The method for manufacturing a high corrosion resistant heat exchanger, wherein the phosphorus-containing nickel alloy contains 4 to 15% by weight of phosphorus. In claim 1 or claim 2,
The stainless steel plate (5) is bent to form the heat exchanger parts of the fin (1) and the plate (2a), and then the phosphorus-containing nickel alloy film (3) is formed on the surface of the high corrosion resistant heat exchanger. Production method.

Images