JP5003983B2 - Laminated structure strengthening method by two-layer brazing - Google Patents

Description

  The present invention relates to brazing technology for joining materials, and more particularly to brazing of a fine plate fin type compact heat exchanger used in the nuclear industry and general industrial fields.

  Conventionally, in a heat exchanger, when a high heat transfer surface density and a heat flux are required, a plate fin type heat exchanger has been used. In addition, when a particularly high heat exchange capability is required, such as a regenerative heat exchanger used in a helium gas cooled HTGR turbine system, a plate fin type heat exchanger using fine offset fins may be used. Conceivable. This fine plate fin type compact heat exchanger (FIG. 1) generally has a problem that it is difficult to ensure pressure resistance because the strength of the brazed portion is not so high in the conventional brazing technique. When the strength test of the fine plate fin is performed, it has been found that the destruction due to the internal pressure is observed particularly in the fine plate fin side portion (portion not joined to the separator) (FIG. 2).

  If the heat exchanger design specifications require further expansion of the heat transfer area and reduction of the heat exchanger dimensions, it is necessary to make the fins finer according to the requirements. There is a need to improve the strength of the fin side because it must be designed thin.

JP 2003-181685 A Japanese Patent Laid-Open No. 04-143066 Japanese Patent Laid-Open No. 02-172875 JP 2000-107857 A JP 2001-330394 A

  Accordingly, an object of the present invention is to solve the problems of the prior art, such as ensuring the pressure resistance of the brazed portion and improving the strength of the fine plate fins in the fine plate fin type compact heat exchanger.

  In order to solve the above-mentioned problems of the prior art, the present inventors have conducted intensive research and completed the present invention.

  In short, the present invention is an offset fin used in a plate fin type heat exchanger, and is characterized by using a rectangular concave and convex offset fin plate having a three-layer structure of brazing material / base material / brazing material. The rectangular concave and convex offset fin plate used in the present invention uses a 0.15 mm thin plate as an offset fin substrate, and an amorphous tape-shaped Ni brazing thin film is positioned on the upper and lower surfaces of the offset fin substrate to form a three-layer structure plywood. It is processed into a concavo-convex shape using an assembly jig (FIG. 3B). The offset fin of the present invention is a multi-stage fin that uses a plurality of the rectangular concave and convex offset fin plates, positions the separator between the two rectangular concave and convex offset fin plates, and brazes the rectangular concave and convex offset fin plate and the separator ( FIG. 3 (b)). Therefore, the multi-stage fin is characterized in that the entire surface of the rectangular uneven offset fin plate is covered with the brazing layer.

  In addition, the present invention provides an offset fin heat exchanger having a high-temperature pressure-resistant structure using the above-described offset fin as a problem solving means.

  Furthermore, the present invention is a method for strengthening a laminated structure by two-layer brazing of offset fins used in a plate fin type heat exchanger, wherein a three-layer structure of Ni brazing material / base material / Ni brazing material is used as an offset fin plate. Using a rectangular concave / convex offset plate, and strengthening the base material by forming a high-strength brazing reaction layer on the entire surface of the rectangular concave / convex offset plate with a Ni brazing material sheet interposed between the plate and the separator. It is a feature.

  By using a heat exchanger having an offset fin having the three-layered rectangular uneven plate of the present invention, the HTGR gas turbine system can be made more compact and high performance, which is an economic advantage for the plant. Is born. Further, according to the present invention, gas / gas heat exchange can be performed under the conditions shown in Table 2.

FIG. 1 is a conceptual diagram of an offset plate fin heat exchanger. (A) is a top view, (b) is a side view. FIG. 2 shows a state of a strength test of a fine plate fin side portion having a laminated structure, and (a) shows a state before the test and (b) a state after the test. FIG. 3 is a conceptual diagram showing an offset fin having a three-layered rectangular uneven offset plate by a two-layer brazing method according to the present invention, where (a) is a conventional brazing method and (b) is according to the present invention. Shows the soldering method. FIG. 4 is a diagram showing a high-temperature strength / fatigue test of a fin specimen by two-layer brazing. FIG. 5 is a conceptual diagram of a fine fin processing procedure (double action method) from a three-layer thin plate (brazing material / fin material / brazing material).

  The present invention is an offset fin used in a plate fin type heat exchanger, and a rectangular uneven plate having a three-layer structure of brazing material / base material / brazing material is used as the offset fin plate. The rectangular concave and convex offset plate uses a 0.15 mm thin plate as the offset fin substrate, and uses a rectangular assembly jig to form a three-layer plywood by positioning amorphous tape-shaped Ni brazing thin films on the upper and lower surfaces of the offset fin substrate. And processed into a concavo-convex shape. The offset fin of the present invention uses a plurality of the rectangular uneven offset fin plates and brazes the rectangular uneven offset fin plate and the separator so that one separator is positioned between the two rectangular uneven offset fin plates. It is a multistage fin. Therefore, the multi-stage fin is characterized in that the entire surface of the rectangular uneven offset fin plate is covered with the brazing layer.

  In the present invention, the material of the offset fin plate and the plate may be any material as long as it is allowed in consideration of operating temperature, pressure, etc., for example, a SUS product can be used, and its dimensions are in accordance with the specifications. Just design. Ni brazing filler metal can be used as the brazing filler metal.

  In FIG. 3, the conceptual diagram which shows the offset fin three-layer structure part by the two-layer brazing method of this invention is shown. In the conventional brazing method shown in (a), the strength of the portion where the fin plate and the separator are not joined (fin side portion) is weak as shown in FIG. However, a three-layer structure having improved high-temperature strength and fatigue strength could be realized by the two-layer brazing method in which both surfaces of the fin plate of the present invention shown in FIG.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to an Example.

  In this example, a three-layer reinforced offset fin element strength test piece was manufactured, and a high temperature strength / fatigue test was performed on the test piece. First, a manufacturing procedure is shown below.

(A) Manufacture of three-layer structure fin and parts processing In order to make an offset plate fin type heat exchanger having a structure as shown in FIG. 1, each part having the dimensions shown in Table 1 was manufactured using SUS304.

  What is particularly important here is the three-layer structure of the offset fin (core). In order to manufacture a three-layer structure offset fin, a Ni brazing thin film (amorphous tape brazing MBF20 (manufactured by Hoshiden), thickness 38 μm) is laid on the upper and lower surfaces of a 0.15 mm thin plate used as an offset fin substrate. The fins are folded into an uneven shape by the double punch method shown in FIG. Specifically, in FIG. 5, first, the plywood is fixed by the upper fixed die and the lower fixed die (a → b), and then the plywood is pushed up by the lower movable die and deformed along the notch portion of the upper fixed die. (B → c) Next, the plywood is pushed down by the upper movable die and deformed along the cutout portion of the lower movable die (c → d), and thereafter, the same procedure is repeated to form the uneven shape. . This method is effective for processing a three-layer plywood because the fin processing accuracy is higher and the brazing thin film is less damaged than the method of folding a fin in a single operation using an uneven mold.

(B) Assembling multi-stage fins Using a rectangular assembly jig, a brazing material is attached to the plate and welded and fixed in the order of a closing plate (separator), and a three-layer structure fin with an uneven shape is placed on it. It was. Subsequently, the multi-stage fins were assembled in the same manner, and the multi-stage fins were assembled while being restrained by a jig.

(C) Vacuum brazing The multistage fins are placed in a vacuum furnace in a constrained temporary assembly, and are vacuumed according to processing conditions of a vacuum degree of 1 × 10 ⁵ torr, a maximum temperature of 1,323 to 1,373 K, and a maximum holding time of 10 to 15 minutes. Brazed.

  The results of the high temperature strength / fatigue test are shown in FIG. In the figure, the closed (black) symbol is the two-layer brazing material according to the present invention, the open (white) symbol is the conventional material, the □ mark indicates the strength and 0.2% guarantee, and the broken line is for comparison. SUS304 base material. As shown in the figure, the high temperature strength was about 1.8 times that of the SUS304 base material.

  In accordance with the present invention, by brazing both sides of the fin side wall portion made of SUS304 base material with Ni brazing material, a Ni-based high strength brazing reaction layer was formed on both sides, and the base material was strengthened.

Claims (3)

A three-layer structure of brazing material / substrate / brazing material comprising an offset substrate and a high-strength brazing reaction layer formed by vacuum brazing an amorphous tape-shaped Ni brazing thin film over the entire upper and lower surfaces of the offset substrate and offset fins the rectangular unevenness offset fin plates comprising a separator that is soldered, using a fine plate-fin heat exchanger; rectangular unevenness offset fin plate is.   The offset fin according to claim 1, wherein the offset substrate is a SUS substrate having a thickness of 0.15 mm. A morphous tape-shaped Ni brazing thin film is positioned on the entire upper and lower surfaces of the offset substrate to form a three-layer structure of brazing material / substrate / brazing material,
The three-layer structure is fixed to the upper fixed die and the lower fixed die, and the three-layer structure is pushed up by the lower movable die and deformed along the cutout portion of the upper fixed die, and then the three movable layers are By repeatedly pressing down the layer structure and deforming along the notch portion of the lower fixed die , processing into a rectangular uneven shape, forming a rectangular uneven offset fin plate,
Positioning a separator on both sides of the rectangular unevenness offset fin plate, assembled multistage fins made of separator / rectangular unevenness offset fin plate / separator,
Two-layer brazing of offset fins for use in a fine plate heat exchanger, comprising vacuum brazing the multi-stage fins to form a high strength brazing reaction layer over the surface of the rectangular rugged offset fin plate. The laminated structure strengthening method by.