JPH08271175A - Stainless steel plate laminated heat exchanger, and its production - Google Patents

Abstract

PURPOSE: To miniaturize a heat exchanger and obtain a pressure proof performance higher than that of a plate type heat exchanger by laminating punched stainless steel plates, welding them together and using the punched openings of the stainless steel plates or a space formed by welding them as passages for fluid. CONSTITUTION: Stainless steel plates 1 to 5 are sequentially laminated and they are welded together so that a laminated member is formed. Then, a fluid inlet port 10 and a fluid outlet port 11 are provided so that passages are formed. In the formed laminated member, the respective non-cut out parts of the adjacent stainless steel plates 1 to 5 are desirably entirely and firmly joined together so that pressure capable to be applied to a fluid can be increased as much as possible. The stainless steel plates 1 to 5 are joined together by a diffusion welding method or a liquid phase diffusion welding method. The diffusion welding method used herein is a method in which the stainless steel plates 1 to 5 whose surfaces are cleaned and flattened are laminated, subjected to a thermal treatment in a non-oxidizing atmosphere and welded together while pressing them so as to come into tight contact with one another. Thus, a low cost and small size can be realized and a pressure proof performance is improved.

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 exchanging heat between a plurality of fluids having different temperatures via a metal or alloy that separates the fluids, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Heat exchangers are widely used in various industries as a device for transferring heat from a high temperature fluid to a low temperature fluid. The types of such heat exchangers include multi-tube type, double-tube type, spiral plate type, brazing plate fin type, plate type, scraping type, etc., and they are appropriately used according to the application.

Of these, the brazed plate fin type heat exchanger and the plate type heat exchanger have a wider heat transfer area than the other methods when compared in the same volume, and the heat transfer area can be easily increased or decreased by increasing or decreasing the plates. It is suitable for small-scale applications because it has excellent design flexibility such as changeable, and is also used for small-sized, for example, general household appliances.

By the way, in recent years, in the field of such a small heat exchanger, there is an increasing demand for products having higher efficiency and lower price, but the brazing plate fin type has a limit in downsizing, On the other hand, the plate type has a small withstand pressure, and there is a problem that it is difficult to obtain a heat exchanger having a small size and a high efficiency without increasing the price significantly in any type.

[0005]

In view of the above situation, the present invention can be made smaller than the brazed plate fin type, has higher pressure resistance than the plate type, and has a higher heat exchange efficiency. The present invention provides a device and a method of manufacturing the same, which are as economical as the miniature heat exchangers of other types.

[0006]

According to the present invention, stainless steel plates that have been punched are laminated and joined to each other, and the holes formed in the stainless steel plates or their connected spaces are used as fluid flow paths. Eggplant stainless steel plate laminated body heat exchanger,
Another object of the present invention is to provide a stainless steel plate laminate type heat exchanger characterized in that the stainless steel plates are solid phase diffusion bonded or liquid phase diffusion bonded.

As a material used for the heat exchanger, copper or copper alloy, aluminum or aluminum alloy having excellent heat conductivity, or inexpensive carbon steel or low alloy steel, and a material to be used, except those for special applications, are used. When the corrosion resistance to the fluid and environment to be treated becomes a problem, stainless steel or the like is considered. Of these materials, stainless steel is
Since the strength is higher than that of other general-purpose materials, the same base material strength as that of other materials can be obtained with a material having a smaller cross-sectional area. Therefore, if the laminate is made of stainless steel, it is most advantageous for downsizing the heat exchanger. Further, since stainless steel is superior in corrosion resistance to other general-purpose materials, there are many choices of fluids that can be used, and therefore, there is an advantage that a substance having a larger latent heat can be used, for example.

The reason why the material used for the laminate in the present invention is stainless steel is because these points are taken into consideration, and in order to provide a heat exchanger that is smaller and has a wider range of applications. The stainless steel used in the present invention may be any of ferrite type, austenite type, martensite type, two phase type and precipitation hardening type, and the impurities contained may be at the level of general commercial steel.

Next, the present inventors examined the method of assembling the stainless steel plate laminate. FIG. 1 is a schematic view of a stainless steel plate laminate having a simple two-system flow path. The assembly drawing is shown in FIG. A case will be described in which stainless steel plates denoted by reference numerals 1 to 5 are sequentially laminated and joined together to manufacture a laminated body as shown in FIG. FIG.
Is a cross section including AA 'in FIG. The flow path of the fluid is indicated by diagonal lines. Further, enlarged views of the portions indicated by reference numerals 6, 7, and 8 in FIG. 3 are shown in FIGS. 4, 5, and 6, respectively. In the figure, 10 is an inflow hole, 11 is an outflow hole, 12 is a flow path, 1
3 shows a brazing part.

In this laminate, it is desirable that the non-hole portions of the adjacent steel sheets are wholly and firmly joined together so that the pressure that can be applied to the fluid can be made as high as possible. As such a joining method, a brazing method, a solid phase diffusion joining method (hereinafter referred to as a diffusion joining method), and a liquid phase diffusion joining method (hereinafter referred to as a liquid phase joining method) can be considered.

Of these joining methods, the brazing method is
(1) Deaf itself is expensive. (2) An alloy or intermetallic compound 9 formed of braze and stainless steel as schematically shown in FIG. 4 may impair the bonding strength, the corrosion resistance, or the reliability of those with time.
(3) The contraction portion 14 of the brazing material that is generated toward the inside of the gap between the steel plates, as schematically shown in FIG. 5, is apt to become a crack generation starting point when the steel plate joint is separated due to the pressure of the fluid.
(4) The protruding portion 1 in the flow channel as schematically shown in FIG.
5, the protruding wax may narrow the flow path and hinder or roughen the flow of the fluid. There are problems such as these, and it is not easy to avoid them, and even if they can be done, a large increase in manufacturing cost cannot be avoided.

On the other hand, the diffusion bonding method and the liquid phase bonding method are advantageous in that they do not have the above-mentioned problems and can obtain higher bonding strength than the brazing method. It is for this reason that the joining method of the stainless steel sheets is limited to the diffusion joining method or the liquid phase joining method in the present invention, and to provide a highly reliable heat exchanger at low cost.

The diffusion bonding method referred to in the present invention is a method in which stainless steel plates whose surfaces are clean and flat are stacked and bonded by heat treatment in a non-oxidizing atmosphere while pressurizing them so that they adhere to each other. Is. Further, the liquid phase bonding method, a paste mainly composed of carbon is applied as an insert material between stainless steel sheets and laminated, and heat treated in a non-oxidizing atmosphere to lower the melting point of the surface by diffusion of carbon,
It is a method of temporarily melting and joining the surface layer of a stainless steel plate. Note that the non-oxidizing atmosphere here means vacuum, argon gas, hydrogen gas, mixed gas of argon and hydrogen, mixed gas of nitrogen and hydrogen, or the like, and heat treatment is 900 ° C to It refers to what is performed at 1300 ° C. for about 10 minutes to 4 hours.

It is known that, when a stainless steel plate is diffusion bonded, the bonding strength is reduced if an aluminum oxide film is present on the surface of the steel plate. Therefore, it is desirable to use a stainless steel plate having a low aluminum content for the laminate.

Diffusion bonding and liquid phase bonding may be carried out under any condition within the above range, as long as the bonding strength is approximately the same as the base material strength. In addition, the insert material used for liquid-phase joining may be selected in consideration of compatibility with the base material such as wettability and price, but in a relatively short time, the joining part and the parent phase are homogeneous. Those that can be converted are desirable.

[0016]

[Operation] Fine drilling of stainless steel plates and solid-phase or liquid-phase joining of laminated steel plates are much more than the enormous number of precision brazing processes for small fins in the brazing plate fin type. It's easy. Further, the laminated body type heat exchanger in which the non-hole portions of the stainless steel plates are entirely bonded by solid phase or liquid phase has pressure resistance sufficiently higher than that of the plate type. Therefore, the stainless steel plate laminate of the present invention acts as an inexpensive and highly efficient heat exchanger.

[0017]

EXAMPLE A stainless steel plate laminate of the type shown in FIG.
It was made using SUS304 and SUS430.
The rectangular size of each steel plate is 10 cm x 20 cm, the thickness is the top layer,
The bottom layer was 2 mm, and the middle three layers were 0.5 mm. A stainless steel pipe was previously welded to the holes of the uppermost and lowermost steel plates so that they could be connected to a fluid circuit. These were joined by diffusion bonding, liquid phase bonding and brazing for comparison. All bonding was performed in vacuum. Table 1 shows the combinations of stainless steel materials and joining methods used. 1
~ 6. The heat treatment conditions for joining, the insert material used, and the brazing material are also shown.

[0018]

[Table 1]

No. Two laminated bodies of 1 to 6 were produced, one of each was subjected to the test A shown in Table 2 and the other was subjected to the test B, and then the laminated body was cut at approximately the center of the long side of the rectangle. , Fig. 3
The joint portion of the steel plate having a cross section as shown in Fig. 3 was observed finely. Table 3 shows the results.

[0020]

[Table 2]

[0021]

[Table 3]

As described above, in the stainless steel plate laminate according to the present invention, no abnormality is found in the joint portion even after repeated heat exchange or pressure adjustment for a long time, and therefore a highly reliable heat It can be seen that it can be a unit for exchangers.

[0023]

EFFECTS OF THE INVENTION Since the stainless steel plate laminate of the present invention uses the holes formed in the stainless steel plate and the spaces connected to the holes as fluid flow paths, it is relatively easy to form extremely fine and complicated flow paths. Since it is possible to make a heat exchanger and the non-hole portion is joined by diffusion bonding or liquid phase bonding, it has excellent pressure resistance and therefore can meet the industrial demand as a compact and highly reliable heat exchanger unit. It is a thing.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing an example of a stainless steel plate laminate of the present invention.

2 (a), (b), (c), (d), and (e) are views in which the stainless steel plates constituting the Sunteres steel plate laminate of FIG. 1 are arranged in the assembling order.

FIG. 3 is a view showing a cross section taken along the line AA ′ of FIG.

FIG. 4 is a schematic diagram showing a reference numeral 6 portion of FIG. 3 in an enlarged manner.

FIG. 5 is a schematic diagram showing a reference numeral 7 in FIG. 3 in an enlarged manner.

FIG. 6 is an enlarged schematic view showing a portion indicated by reference numeral 8 in FIG.

[Explanation of symbols]

1-5 Stainless steel plate 6-8 Part shown in enlarged view 9 Alloy of braze and stainless steel or intermetallic compound 10 Inflow hole 11 Outflow hole 12 Flow path 13 Brazing part 14 Shrinking part 15 Protrusion part

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mikio Yamanaka 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (2)

[Claims] 1. A stainless steel plate laminate type heat exchanger in which punched stainless steel plates are stacked and joined to each other, and the holes formed in the stainless steel plates or the spaces connected to each other form a fluid flow path. . 2. The heat exchanger according to claim 1, wherein the laminated stainless steel plates are mutually joined by solid phase diffusion bonding or liquid phase diffusion bonding.