JP2002137054A - Heat exchanger and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger and its production method that enables an easy production of, without losing its consistent quality, such a heat exchanger as an exhaust gas recirculating cooler, which a corrosive gas having a high temperature goes through. SOLUTION: A fin 1 is inserted through a nickel-base brazing filler into a flat tube 2, and an assembly of such fin 1 and tube 2 alone is integrally, fixedly brazed. Then an assembly of the flat tube 2 and a header plate 3, an assembly of the header plate and a casing 4, and an assembly of the header plate 3 or the casing 4 and a tank body 5 are fixedly welded by welding accompanied by melting of parent materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for cooling a high-temperature corrosive gas used in an exhaust gas recirculation cooler (hereinafter, referred to as an EGR cooler) or the like for purifying exhaust gas from a diesel vehicle or the like. The present invention relates to a method for manufacturing a liquid-liquid heat exchanger for a chemical plant to be handled, and a heat exchanger manufactured using the method.

[0002]

2. Description of the Related Art In an EGR cooler, a highly corrosive exhaust gas flows at a high temperature, and therefore, a stainless steel material having corrosion resistance is usually used. The air conditioner includes a pair of header plates each having a plurality of tubes and both ends thereof fixed therethrough, a casing for fitting the outer periphery between the pair of header plates, and a tank body connected to one end of each header plate. Either brazing or welding is selected between the connection parts of the parts. It has been known that a flat tube is used as such a heat exchanger and fins are arranged in the flat tube. When a heat exchanger is manufactured by brazing, a nickel-based brazing material such as BNi-5 has been used. In the case of welding, the components are welded by TIG welding, laser welding, or the like.

[0003]

When each component is brazed with a nickel-based brazing material, the gap between the components is 100 μm.
In this case, a precipitate of Ni or Si is formed as an embrittlement layer in the brazed portion, and there is a high risk that a crack is generated there. Therefore, it is necessary to maintain high dimensional accuracy between the parts,
As a result, the cost is high and it is not economical. When all are performed by welding, it is not possible to insert fins into the tube and join them therebetween. If only fins are inserted, there is a disadvantage that the heat transfer is poor and the heat exchange performance cannot be maintained high. SUMMARY OF THE INVENTION It is an object of the present invention to provide a manufacturing method for providing a highly reliable heat exchanger which is easy to assemble and does not have an embrittlement layer at a brazed portion at a low cost.

[0004]

According to the first aspect of the present invention, there are provided a plurality of flat tubes (2) having fins (1) therein.
The end of each flat tube (2) is fitted to the header plate (3) airtightly fixed in the flat hole, and the outer periphery between the header plate (3) outside the flat tube (2). And the casing connected to the header plate (3)
(4) and its casing (4) or header plate (3)
In the method for manufacturing a heat exchanger comprising a tank body (5) connected to one end of a flat tube (2), a nickel-based brazing material (6) is first placed between the fin (1) and the inner surface of the flat tube (2). And fins (1) inside the flat tube (2),
The combination of the fin (1) and the flat tube (2) alone is heated to melt the nickel-based brazing material, and at least the inner surface of the flat tube (2) and the fin (1) The gap between them is kept at 100 μm or less, and brazing between them to produce the fin-containing flat tube alone, and then the end of the flat tube (2) after brazing, Insert the header plate (3) and each flat tube through the flat holes of the header plate (3).
(2), outer periphery of header plate (3) and casing
(4), between the tank body (5) and the header plate (3) or the casing (4), while supplying the filler material while melting the base material, or supplying the filler material. And a step of welding without the use of a stainless steel material.

According to a second aspect of the present invention, in the first aspect, the brazing is performed in a state in which the tip of the fin (1) is retracted at least 1 mm inward from the tip of the flat tube (2). This is a method for manufacturing a heat exchanger. According to a second aspect of the present invention, in the first or the second aspect, the edge of the flat hole of the header plate (3) is burred into a small cylindrical shape on the header side. The distal end of the flat tube (2) is inserted from the casing side, the distal end surface of the flat tube (2) and the distal end surface of the burring are substantially aligned, and the heat exchange is performed by welding between the aligned end surfaces. It is a manufacturing method of the container. The present invention according to claim 4 provides:
A heat exchanger manufactured using the method for manufacturing a heat exchanger according to any one of claims 1 to 3.

[0006]

Next, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 sequentially show an example of first and second manufacturing steps of the heat exchanger of the present invention, FIG. 3 shows an example of the third manufacturing step, and FIG. 4 shows an example of a fourth manufacturing step. It is explanatory drawing shown respectively. FIG. 5 is a partially exploded perspective view of the heat exchanger manufactured by the manufacturing method of the present invention. The heat exchanger shown in FIG. 5 has a large number of flat tubes 2 in which fins 1 are provided by brazing, and both ends of the flat tubes 2 are hermetically welded and fixed to flat holes of a pair of header plates 3. Both open ends of the casing 4 are fixed by welding between the pair of header plates 3. The opening ends of the tank bodies 5 are welded and fixed to the ends of the respective header plates 3.

The heat exchanger is manufactured in the following order.
First, as shown in FIG.
The fin 1 is inserted into a flat tube 2 made of a stainless steel material such as 6L. At this time, a foil-like nickel-based brazing material is interposed between the fin 1 and the inner surface of the flat tube 2. As an example of the nickel-based brazing material, BNi-5 or the like can be used. Instead of the foil material, a powdery nickel-based brazing material may be applied to the upper and lower surfaces of the fins or the inner surface of the tube via a binding material.

In this example, the fin 1 is a multi-entry corrugated fin having a large number of cut-and-raised portions. Instead, a normal corrugated fin is used and its ridge direction is changed to that of the flat tube 2. It may be inserted into the flat tube 2 while being aligned in the longitudinal direction. In any case, the height of the fin 1 is selected to be slightly smaller than the inner surface height of the cross section of the flat tube 2. And the gap is 100
The thickness can be set to μm or more, but is not limited to this, and it is essential that the fin 1 can be inserted into the flat tube 2. In addition, at the time of insertion, as shown in FIG. 2, the fin 1 is preferably arranged at both ends in the longitudinal direction so that the tip thereof is retracted by 1 mm or more from the tip of the flat tube 2. That is, e> 1 in FIG.
mm. This is because, in a later step described later, cracks may occur in the brazed portion due to the heat depending on welding conditions, so that welding can be easily performed without melting the fins.

The fin 1 and the flat tube 2 assembled as described above are inserted into a furnace alone as a combination thereof. At this time, a weight (weight) that presses the flat tube 2 in the thickness direction is placed on the outer surface thereof. Then, the fin 1, the flat tube 2, and the nickel-based brazing material are heated in a high-temperature furnace. Then, the rigidity of the flat tube 2 is reduced by the heating, and the fin 1 and the inner surface of the flat tube 2 are pressed and contacted by the weight placed on the upper surface. In this state, the brazing material 6 is melted, and then cooled and solidified, so that the fin 1 and the flat tube 2 are brazed and fixed in a close contact state. In place of the weight, the outer surface of the flat tube may be pressed toward the center with an appropriate holding jig or a pair of rollers.

Next, as shown in FIG. 3 (the left end side is omitted), both ends of a large number of flat tubes 2 having the fins 1 therein are arranged as shown in FIG.
Each of the header plates 3 is inserted through a plurality of flat holes formed in advance. At this time, the dimension of the flat hole of the header plate 3 is
It is preferable that it is slightly larger than the outer circumference of the flat tube 2 and is as small as possible within a range that does not hinder insertion. Thereby, the flat tube 2 can be easily inserted into the hole of the header plate 3.

Next, the tip of the flat tube 2 as a base material and the hole edge of the header plate 3 are melted by TIG welding or laser welding, respectively, and a filler material is added thereto, and the two are securely brazed. I do. At this time, the gap between the base material and the filler material is completely filled by the melting of the base material and the filler material, and the confidentiality and liquid tightness are maintained. Similarly, a groove is formed between one end of the header plate 3 and the casing 4 in advance, or welding is performed while adding a filler material to the groove without forming a groove. Similarly, header plate 3
As shown in FIG. 4, the open end of the tank body 5 is arranged on the other surface side, and a groove is formed between them, or a welding material is added thereto without forming a groove, and the two are fixed by welding. In addition,
Each component can be welded by melting the base material itself without using a filler material in the above process.

A pair of cooling water pipes 7 are arranged at both ends of the casing 4 directly or via bosses for flanges (not shown), and gas pipes 8 are fixed to the pair of tank bodies 5 by welding. To complete the heat exchanger. And cooling water flows in from one cooling water pipe 7,
It flows out of the other cooling water pipe 7. High-temperature exhaust gas is supplied from the gas pipe 8 of the tank body 5 on one side, flows through the flat tubes 2, and flows out of the gas pipe 8 of the other tank body 5. While the exhaust gas flows through the flat tube 2, heat exchange is performed between the flat tube 2 and the cooling water on the outer periphery of the flat tube 2. Since the inner surface of the flat tube 2 of this heat exchanger is brazed with the fins 1 contained therein, heat transfer between the two is high and heat is efficiently exchanged.

[0013]

According to the method for manufacturing a heat exchanger of the present invention, first, a nickel-based brazing material is arranged between the fin 1 and the inner surface of the flat tube 2 and is combined. Since these are heated and the gap between the inner surface of the flat tube 2 and the fin 1 is kept at 100 μm or less at the time of heating and brazing between them, a step of manufacturing a fin-containing flat tube is performed. And the inner surface of the flat tube 2 can be reliably brazed, and the heat exchange performance can be improved. Then, after the brazing, the end of the flat tube 2 is inserted into the flat hole of the header plate 3, and the space between the header plate 3 and the flat tube 2, the space between the header plate 3 and the casing 4, the tank body 5 and the header A step of welding a filler material or a filler material without supplying a filler material between the plate 3 and the casing 4 while melting the respective base materials is performed. The gaps between the parts are filled, and the airtightness and liquid tightness of each part can be secured.

Therefore, a highly reliable heat exchanger can be manufactured even if the production accuracy of each part is relatively low. Since the fin 1 and the flat tube 2 are brazed alone in a combined state at the time of brazing, the gap can be easily maintained at 100 μm or less, and an embrittlement layer at the brazed portion is generated. Nothing.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of a first step of a method for manufacturing a heat exchanger according to the present invention.

FIG. 2 is an explanatory view showing an example of a second step of the method for manufacturing the heat exchanger.

FIG. 3 is an explanatory view showing an example of a third step of the method for manufacturing the heat exchanger.

FIG. 4 is an explanatory view showing an example of a fourth step of the method for manufacturing the heat exchanger.

FIG. 5 is a partially exploded perspective view of a heat exchanger manufactured by the method for manufacturing a heat exchanger of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fin 2 Flat tube 3 Header plate 4 Casing 5 Tank body 6 Brazing material 7 Cooling water pipe 8 Gas pipe 9 Welded part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F28F 9/18 F28F 9/18 21/08 21/08 F // B23K 101: 14 B23K 101: 14

Claims (4)

[Claims] 1. A plurality of flat tubes (2) in which fins (1) are housed, and a header plate (3) in which the ends of the respective flat tubes (2) are air-tightly fixed through flat holes. A casing (4) connected to the header plate (3) by fitting the outer periphery between the header plates (3) outside the flat tube (2), and the casing (4) or the header plate (3) A tank body (5) connected to one end of a heat exchanger comprising: a nickel-based brazing material (6) between a fin (1) and an inner surface of a flat tube (2); Place the flat tube (2)
Fins (1) inside the fins (1) and flat tubes
In the combined state with (2) alone, they are heated to melt the nickel-based brazing material (6), and at least the gap between the inner surface of the flat tube (2) and the fin (1) is heated at the time of heating. Is maintained at 100 μm or less, and brazing is performed between them to produce a fin-containing flat tube alone. Then, the end of the flat tube (2) after brazing is
It is inserted through the flat hole of the header plate (3), between the header plate (3) and each flat tube (2), between the outer periphery of the header plate (3) and the casing (4), and the tank body (5). )
And between the header plate (3) or the casing (4)
A method of supplying a filler material or welding without supplying a filler material while melting the base materials, wherein each component is made of a stainless steel material. 2. The method according to claim 1, wherein the brazing is performed with the tip of the fin (1) retracted at least 1 mm inward from the tip of the flat tube (2). 3. The burring portion according to claim 1 or 2, wherein the edge of the flat hole of the header plate (3) is burred into a small cylinder on the header side.
A heat exchanger in which the distal end portion of the flat tube (2) is inserted from the casing side, the distal end surface of the flat tube (2) and the distal end surface of the burring are substantially aligned, and the aligned end surfaces are welded and fixed. Manufacturing method. 4. A heat exchanger manufactured by using the method for manufacturing a heat exchanger according to claim 1.