JP7077033B2 - Manufacturing method of the joint - Google Patents

Description

The present invention relates to an austenitic stainless steel sheet suitable for diffusion bonding and the like.

The method of diffusing and joining stainless steel materials is used in various applications such as heat exchangers, mechanical parts, fuel cell parts, home appliance parts, plant parts, decorative components, and building materials. Diffusion joining includes an insert material insertion method and a direct method. The insert material insertion method is a method in which an insert material made of a different metal material that is familiar with the stainless steel material to be joined is inserted into the joining interface, and both stainless steel materials are joined by solid phase diffusion or liquid phase diffusion. In the insert material insertion method, there are likely to be problems such as an increase in cost due to the use of the insert material and a decrease in corrosion resistance due to the presence of dissimilar metals at the joints.

The direct method is a method in which the surfaces of both stainless steel materials are brought into direct contact with each other without using an insert material and joined by solid phase diffusion. For example, Patent Document 1 discloses a method using a ferrite-based stainless steel for direct diffusion bonding having a specific composition.

Japanese Unexamined Patent Publication No. 2000-303150 (published on October 31, 2000)

By the way, among stainless steel materials, there is austenitic stainless steel having excellent corrosion resistance and heat resistance. The technique of Patent Document 1 is a technique for ferritic stainless steel and cannot be applied to austenitic stainless steel.

In addition, since austenitic stainless steel has a slow progress of atomic diffusion, diffusion bonding is unlikely to occur. Therefore, it is necessary to increase the surface pressure applied at the time of diffusion bonding. However, if the surface pressure is increased, there is a problem that the austenitic stainless steel sheet is greatly deformed.

One aspect of the present invention is to realize a set of austenitic stainless steel sheets capable of performing diffusion bonding while suppressing deformation of the steel sheet.

In order to solve the above problems, the set of austenite-based stainless steel sheets according to the first aspect of the present invention is a set of austenite-based stainless steel sheets including a plurality of austenite-based stainless steel sheets used for diffusion bonding, and is described above. As a steel plate, a first steel plate in which a flow path is formed, a second steel plate, and a third steel plate in which a flow path intersecting the flow path when viewed from a direction perpendicular to the joint surface is formed. The third steel sheet is a steel sheet that is diffusion-bonded to the second steel sheet by applying a surface pressure of 2.5 to 9.0 MPa after the first steel sheet and the second steel sheet are diffusion-bonded. The second steel sheet so that the amount of deflection of the second steel sheet when a surface pressure of 0.5 to 3.5 MPa is applied during diffusion bonding between the first steel sheet and the second steel sheet is within the range of 30 μm or less. The plate thickness is set in the range of 0.3 to 0.7 mm.

According to the above configuration, the thickness of the second steel sheet is set to 0.3 to 0.7 mm so that the amount of deflection of the steel sheet after applying a surface pressure of 0.5 to 3.5 MPa is 30 μm or less. be able to. As a result, the second steel sheet and the third steel sheet can be joined by applying a surface pressure of 2.5 to 9.0 MPa in the subsequent diffusion joining. Further, when a surface pressure of 2.5 to 9.0 MPa is applied, the third steel sheet is not significantly deformed (buckling does not occur). That is, diffusion bonding can be performed while suppressing deformation of the third steel sheet.

In the set of austenite-based stainless steel sheets according to the second aspect of the present invention, the steel sheets are Cr: 16.0% by mass to 20.0% by mass, Ni: 8.0% by mass to 15.0% by mass, Si. : 0.001% by mass to 1.0% by mass, C: 0.08% by mass or less may be included.

In the austenite-based stainless steel plate according to the third aspect of the present invention, the steel plate is Cr: 16.0% by mass to 18.0% by mass, Ni: 10.0% by mass to 15.0% by mass, Si: 0. The configuration may include 001% by mass to 1.0% by mass, Mo: 2.0% by mass to 3.0% by mass, and C: 0.08% by mass or less.

In the austenite-based stainless steel plate according to the fourth aspect of the present invention, the steel plate is Cr: 16.0% by mass to 18.0% by mass, Ni: 12.0% by mass to 15.0% by mass, Si: 0. The configuration may include 001% by mass to 1.0% by mass, Mo: 2.0% by mass to 3.0% by mass, and C: 0.030% by mass or less.

The method for producing a bonded body according to the fifth aspect of the present invention is Cr: 16.0% by mass to 20.0% by mass, Ni: 8.0% by mass to 15.0% by mass, Si: 0.001% by mass. A bonded body produced by diffusion-bonding a set of austenite-based stainless steel sheets containing% to 1.0% by mass, Mo: 0.0% by mass to 3.0% by mass, and C: 0.08% by mass or less. The first steel sheet as the steel sheet in which a flow path is formed by applying a surface pressure of 0.5 to 3.5 MPa, and the steel sheet having a thickness of 0.3 to 0.7 mm. The first diffusion joining step of diffusion joining the second steel sheet as a steel sheet, the second steel sheet after the first diffusion joining step, and the first steel sheet as the steel sheet different from the first steel sheet and the second steel sheet. 3 A second diffusion joining step of diffusion joining a steel sheet having a flow path intersecting the flow path when viewed from a direction perpendicular to the joint surface at 2.5 to 9.0 MPa. include.

In the sixth aspect of the present invention, the bonded body is a bonded body composed of the set of austenitic stainless steel plates according to any one of the first to fourth aspects.

According to one aspect of the present invention, diffusion bonding can be performed while suppressing deformation of the steel sheet.

It is a figure for demonstrating diffusion bonding in manufacturing of the heat exchanger which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the said heat exchanger. (A) is a top view showing the configuration of the lower plate, the partition plate and the upper plate included in the heat exchanger, and (b) is a top view showing the configuration of the flow path plate included in the heat exchanger. , (C) is a top view showing the configuration of a flow path plate different from the flow path plate. It is sectional drawing of the said heat exchanger. It is a figure which shows the experimental condition and the experimental result in the Example of this invention. It is a top view which shows the structure of the upper plate in an Example of this invention.

Hereinafter, one embodiment of the present invention will be described in detail. In addition, "A to B" in this specification means "A or more, B or less", for example, if it is described as "1% to 5%" or "1 to 5%" in the specification. Indicates "1% or more and 5% or less". Further, the various physical properties mentioned in the present specification mean values measured by the method described in Examples described later, unless otherwise specified. Further, in the present specification, unless otherwise specified, "%" used in indicating the composition means "mass%".

In the present embodiment, a method of laminating a plurality of plate materials composed of a set of austenitic stainless steel sheets according to one aspect of the present invention and diffusing and joining the plate materials to manufacture a heat exchanger as a bonded body will be described. However, the set of austenitic stainless steel sheets of the present invention can be used for manufacturing products (bonds) other than heat exchangers.

FIG. 1 is a diagram for explaining diffusion bonding (first diffusion bonding or second diffusion bonding described later) in the manufacture of the heat exchanger 10 (see FIG. 2) in the present embodiment. As shown in FIG. 1, diffusion bonding in the manufacture of the heat exchanger 10 is performed using the hot press device H. The hot press device H can pressurize and overheat in a predetermined atmosphere. As shown in FIG. 1, in the hot press apparatus H, the diffusion bonding in the present embodiment is performed by (1) a plurality of plate materials (in the example of FIG. 1, the lower plate 11, the flow path plates 12 to 14, and the partition, which will be described later). The release member 2 is arranged on both sides (upper and lower surfaces) of the laminate made of the plate 15) (in the example of FIG. 1, the first laminate 20), and (2) the laminate is sandwiched via the release member 2. This is done by arranging the presser jig 3 so as to (3) and pressing the laminated body with the pressurizing device 4 via the presser jig 3. Details will be described later.

(Component composition of austenitic stainless steel sheet)
The austenitic stainless steel sheet of one aspect of the present invention used as the plate material has the following components.

Cr is a main component of a stainless steel sheet, which is important for ensuring corrosion resistance. Increasing the proportion of Cr oxide in the oxide film is also effective in reducing the proportion of Si oxide, Ti oxide, Al oxide and the like that are difficult to reduce. The Cr content of the austenitic stainless steel sheet in this embodiment is 16.0% by mass to 20.0% by mass.

Ni is an effective element for obtaining an austenite single-phase structure. The Ni content of the austenitic stainless steel sheet in this embodiment is 8.0% by mass to 15.0% by mass.

Si is added to austenitic stainless steel sheets for deoxidizing agents and other purposes. The Si content of the austenitic stainless steel sheet in this embodiment is 0.001% by mass to 1.0% by mass.

Mo is a component for improving corrosion resistance to seawater and various media. The Mo content of the austenitic stainless steel sheet in the present embodiment is preferably 2.0% by mass to 3.0% by mass. However, it does not necessarily have to contain Mo.

C is an element that combines with Cr to precipitate chromium carbides and causes intergranular corrosion. Therefore, the content of C should be low. The C content of the austenitic stainless steel sheet in this embodiment is 0.08% by mass or less. In order to improve the intergranular corrosion resistance of the stainless steel sheet, the C content is preferably 0.03% by mass or less.

Regarding other component elements, it is not necessary to be particular about it from the viewpoint of diffusion bondability, and various component compositions can be adopted depending on the application.

The following can be exemplified as a specific composition range of the austenitic stainless steel sheet according to one aspect of the present invention. By mass%, Cr: 16.0% to 18.0%, Ni: 10.0% to 15.0%, Si: 0.001% to 1.0%, N: 0.005% to 0.50 %, Mn: 0.05% to 2.0%, P: 0.001% to 0.045%, S: 0.0005% to 0.030%, V: 0% to 0.15%, Cu: 0% to 4.0%, W: 0% to 4.0%, Mo: 0% to 3.0%, Nb: 0% to 1.0%, B: 0% to 0.010%, balance Fe And unavoidable impurities.

(Structure of heat exchanger)
FIG. 2 is a front view showing the structure of the heat exchanger 10. As shown in FIG. 2, the heat exchanger 10 includes a lower plate 11, a flow path plate 12, a flow path plate 13, a flow path plate 14 (first steel plate), and a partition plate 15 (second steel plate) in this order from the bottom. Each plate material of the flow path plate 16 (third steel plate), the flow path plate 17, the flow path plate 18, and the upper plate 19 is laminated. All of these plate materials are formed of the above-mentioned austenitic stainless steel plate.

FIG. 3A is a top view showing the configuration of the lower plate 11, and FIG. 3B is a top view showing the configurations of the flow path plate 12, the flow path plate 13, and the flow path plate 14; ) Is a top view showing the configuration of the partition plate 15, (d) is a top view showing the configurations of the flow path plate 16, the flow path plate 17, and the flow path plate 18, and (e) is a top plate. It is a top view which shows the structure of 19.

As shown in FIG. 3B, the flow path plate 12, the flow path plate 13, and the flow path plate 14 are flat plates, and a plurality of flow paths having a flow path width W1 extending in the longitudinal direction inside the flow path plate 12 and the flow path plate 13 are flat plates. Is formed at intervals W2. As shown in FIG. 3D, the flow path plate 16, the flow path plate 17, and the flow path plate 18 are flat plates, and a plurality of flows having a flow path width W1 extending in the lateral direction are formed inside the flow path plate 16. The road is formed with an interval W2. Further, in the flow path plates 16 to 18, the fluid introduction hole H1 for introducing the fluid introduced from the upper plate 19 into the flow path plates 12 to 14 and the introduced fluid are discharged from the flow path plates 12 to 14. The fluid discharge hole H2 is formed. As shown in FIG. 3A, the lower plate 11 is a flat plate, and no flow path is formed inside. As shown in FIG. 3C, the partition plate 15 is a flat plate, and no flow path is formed inside. Further, the partition plate 15 is formed with a fluid introduction port H3 for introducing the fluid into the flow path plates 12 to 14, and a fluid discharge port H4 for discharging the introduced fluid from the flow path plates 12 to 14. As shown in FIG. 3 (e), the upper plate 19 is a flat plate, and no flow path is formed inside. Further, the upper plate 19 has a fluid introduction port H5 and a fluid introduction port H6 for introducing fluid into the flow path plates 12 to 14 and the flow path plates 16 to 18, respectively, and the flow path plates 12 to 14 and the flow path plate 16. A fluid discharge port H7 and a fluid discharge port H8 for discharging fluid from each of 18 to 18 are formed.

(Manufacturing method of heat exchanger)
The method for manufacturing the heat exchanger 10 in the present embodiment includes a first diffusion joining step and a second diffusion joining step.

<First diffusion joining process>
In the first diffusion joining step, the hot press device H was used to stack the first laminated body 20 in which the lower plate 11, the flow path plate 12, the flow path plate 13, the flow path plate 14, and the partition plate 15 were laminated. This is a process of joining by diffusion joining. Specifically, first, the first laminated body 20 is loaded inside the hot press device H. At this time, in the hot press device H, the pressing jig 3 is arranged so as to be in contact with each of the two mold release members 2 arranged on the outside of the first laminated body 20. The presser jig 3 is connected to the pressurizing shaft of the pressurizing device 4. Next, by operating the pressurizing mechanism (not shown), the presser jig 3 presses the first laminated body 20 so as to sandwich it through the pressurizing device 4. As a result, a predetermined pressure is applied to the lower plate 11, the flow path plate 12, the flow path plate 13, the flow path plate 14, and the partition plate 15. More specifically, the application of pressure by the pressurizing device 4 is held for a predetermined time (specifically, 0.5 to 3 hours). Further, the inside of the hot press device H is maintained in a vacuum (preferably an initial vacuum degree of 10 ^-1 Pa or less) or an inert atmosphere. The joining temperature is preferably 900 to 1250 ° C, more preferably 980 to 1200 ° C. By applying the pressure by the pressurizing device 4 under the above conditions, the lower plate 11, the flow path plate 12, the flow path plate 13, the flow path plate 14, and the partition plate 15 are diffusion-bonded.

As the mold release member 2, it is preferable to use a mold release member made of a steel material containing 1.5% by mass or more of Si. Since the release member 2 is placed in contact with the laminated body at the time of diffusion bonding under high temperature and high pressure, it is required that the release member 2 is less damaged or corroded at high temperature and does not react with the laminated body. The mold release member 2 according to the present embodiment is preferably made of a steel material having a high Si content from the viewpoint of suppressing the reaction with the laminated body. The shape of the release member 2 is appropriately selected according to the shape of the laminated body. Since the plate material of the plate heat exchanger is generally plate-shaped, the mold release member 2 arranged in contact with the plate material is used as a mold release plate. The plate thickness of the release member 2 is preferably 2 to 10 mm, more preferably 3 to 8 mm.

The presser jig 3 is a member that is connected to the pressurizing mechanism of the pressurizing device 4 and applies a pressing force to the laminated body (in the example of FIG. 1, the first laminated body 20). The presser jig 3 is preferably made of a carbon material because it is required to have heat resistance at the temperature at the time of diffusion bonding and not to be damaged.

The pressurizing device 4 may be equipped with a pressurizing mechanism such as a servo, a spring, or a weight. A mold release agent may be applied to the surface of the mold release member 2 before the diffusion bonding so that the laminate 1 and the mold release member 2 can be easily removed after the diffusion bonding. As the mold release agent, for example, a boron nitride (boron nitride) -based spray such as hexagonal boron nitride powder (h-BN) can be used. The coating thickness of the release agent may be 3 times or more (about 10 μm) of the average particle size (for example, about 3 μm) of the release agent powder.

A plurality of plate materials (that is, a lower plate 11, a flow path plate 12, a flow path plate 13, a flow path plate 14, a partition plate 15, a flow path plate 16, a flow path plate 17, a flow path plate 18, and an upper plate 19). In the heat exchanger 10 in which the above-mentioned plates are laminated, a fluid passes through a narrow flow path formed by the plurality of plate materials, and heat is exchanged between the high-temperature side fluid and the low-temperature side fluid via each plate material. Is done. Therefore, the plate material is required to have good mechanical strength (high temperature strength) and corrosion resistance in a high temperature range. From this point of view, in this embodiment, stainless steel having excellent heat resistance and durability is used as the plate material. Further, in order to improve the heat exchange performance, it is desirable that each plate has a thin plate shape.

FIG. 4 is a diagram showing a cross-sectional shape of a first laminated body 20 manufactured by diffusion-bonding a lower plate 11, a flow path plate 12, a flow path plate 13, a flow path plate 14, and a partition plate 15. As described above, a flow path is formed in the flow path plate 14. Therefore, in the lower plate 11 and the partition plate 15, the portion corresponding to the portion where the flow path of the flow path plate 12 or the flow path plate 14 is formed bends. Here, as shown in FIG. 4, the maximum amount of deflection at the bent portion of the lower plate 11 and the partition plate 15 is defined as the amount of deflection δ ₂ and the amount of deflection δ ₁ , respectively. Further, the plate thickness of the partition plate 15 is defined as the plate thickness t. The amount of deflection δ ₁ and the amount of deflection δ ₂ can be measured, for example, by using a shape measuring device using a laser displacement meter. Specifically, the deflection amount δ ₁ is specified by measuring the height (recess amount) of the bending portion based on the height of the non-defending portion of the partition plate 15.

In the first diffusion joining step, a surface pressure of 0.5 to 3.5 MPa is applied to the lower plate 11, the flow path plate 12, the flow path plate 13, the flow path plate 14, and the partition plate 15 by the pressurizing device 4. Apply. If the surface pressure is smaller than 0.5 MPa, diffusion bonding between the lower plate 11, the flow path plate 12, the flow path plate 13, the flow path plate 14, and the partition plate 15 is not sufficiently performed, which is unsuitable. Further, when the surface pressure is larger than 3.5 MPa, the amount of deflection δ ₁ of the partition plate 15 becomes too large, which is unsuitable. The details of the deflection amount δ ₁ will be described later.

<Second diffusion joining process>
In the second diffusion joining step, the first laminated body 20, the flow path plate 16, the flow path plate 17, the flow path plate 18, and the upper plate 19 joined by the first diffusion joining step are laminated and laminated. This is a step of joining the body 21 (see FIG. 2) by diffusion joining using the hot press device H. Since the conditions of the second diffusion joining step are substantially the same as the conditions of the first diffusion joining step, only the differences from the first diffusion joining step will be described here.

As described above, after the first diffusion joining step, the partition plate 15 is bent at the portion corresponding to the portion where the flow path of the flow path plate 14 is formed. Therefore, the flow path plate 16 is a portion where the bent portion of the partition plate 15 and the portion where the flow path of the flow path plate 16 is formed intersect with the partition plate 15 in the second diffusion joining. It is difficult to apply pressure at (hereinafter referred to as an intersection). Therefore, in order to diffusely join the partition plate 15 and the flow path plate 16, it is necessary to apply a large pressure. However, if too much pressure is applied, buckling will occur and there is a problem that it cannot be used as a product.

Therefore, the partition plate 15 in the present embodiment has a plate thickness t of ₀ . It is set in a range of 3 mm or more. As a result, in the second diffusion bonding step, the partition plate 15 and the flow path plate 16 can be diffusion-bonded by applying a pressure at which buckling does not occur (specifically, 2.5 to 9.0 MPa). It has become like.

Further, the lower plate 11, the flow path plate 12, the flow path plate 13, the flow path plate 14, the partition plate 15, the flow path plate 16, the flow path plate 17, the flow path plate 18, and the upper plate 19 enhance the heat transfer efficiency. Therefore, the plate thickness is 0.7 mm or less.

It should be noted that the above-mentioned intersection can be said to be a place where the flow path of the flow path plate 14 and the flow path of the flow path plate 16 intersect when viewed from the direction perpendicular to the joint surface (vertical direction).

(Modification example)
Next, a modified example of the manufacturing method of the heat exchanger 10 will be described. The method for manufacturing the heat exchanger 10 in this modification includes a first diffusion joining step, a second diffusion joining step, and a third diffusion joining step. Since the first diffusion joining step in this modification is the same as the first diffusion joining step described above, the description thereof is omitted here.

In the second diffusion joining step in this modification, a laminated body in which the flow path plate 16, the flow path plate 17, the flow path plate 18, and the upper plate 19 are laminated (hereinafter referred to as a third laminated body) is used. This is a step of joining by diffusion joining using the hot press device H. Other conditions in the second diffusion joining step in this modification are the same as in the first diffusion joining step.

The third diffusion joining step is a step of diffusion joining the first laminated body joined in the first diffusion joining step and the third laminated body joined in the second diffusion joining step. Specifically, in the third diffusion joining step, a pressure at a pressure at which buckling does not occur (specifically, 2.5 to 9.0 MPa) is applied to the partition plate 15 of the first laminated body and the first layer. 3 Diffusion bonding is performed with the flow path plate 16 of the laminated body.

Also in this modification, the plate thickness t of the partition plate 15 is 0.3 mm so that the amount of deflection δ ₁ due to the application of a surface pressure of 0.5 to 3.5 MPa in the first diffusion joining step is within the range of 30 μm or less. It is set in the above range. As a result, in the third diffusion bonding step, the partition plate 15 and the flow path plate 16 can be diffusion-bonded by applying a pressure at which buckling does not occur (specifically, 2.5 to 9.0 MPa). It has become like.

Further, also in this modification, the lower plate 11, the flow path plate 12, the flow path plate 13, the flow path plate 14, the partition plate 15, the flow path plate 16, the flow path plate 17, the flow path plate 18, and the upper plate 19 Since it is preferable to increase the heat transfer efficiency, the plate thickness is 0.7 mm or less.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

Hereinafter, examples of the present invention will be described. The present invention is not limited to the following examples, and can be modified as appropriate.

A steel plate as a test material used in this example was produced as follows. Cr: 16.70%, Ni: 10.10%, Si: 0.60%, N: 0.018%, Mn: 1.00%, Mo: 2.04%, P: 0.020%, S A steel material consisting of: 0.001%, Cu: 0.30%, Al: 0.022%, C: 0.020%, balance Fe and unavoidable impurities was melted by 30 kg of vacuum melting to obtain it. The ingot was forged into a plate with a thickness of 30 mm. Next, hot rolling at 1200 ° C. was performed to obtain a hot-rolled plate having a thickness of 6 mm, and then soaking-annealing was performed at 1100 ° C. for 60 seconds to obtain a hot-rolled annealed plate. After cold rolling the hot-rolled annealed plate to a thickness of 3.0 mm, final annealing at 1100 ° C. for 30 seconds is performed to make the final finished plate thickness 3 mm, and the surface finish treatment is 2B finish or 2D finish. This was done to obtain a cold-rolled annealed plate. Further, the cold-rolled annealed plate was cold-rolled and annealed, the final finished plate thickness was 0.3 to 0.6 mm, and the surface finishing treatment was performed by 2B or 2D finishing to obtain a cold-rolled annealed material. From the cold-rolled annealed plate, a plate having a size of 210 mm × 160 mm was cut out to prepare a test material.

Using the above test material, the first steel plate in which the flow path (flow path width 5 mm) is formed, the second steel plate in which the flow path is not formed, and the direction in which the flow path of the first steel plate is formed are orthogonal to each other. A third steel plate having a flow path (flow path width of 5 mm) formed in the direction of the flow was produced. The first steel plate is a steel plate corresponding to the flow path plates 12 to 14 in the first embodiment, and the second steel plate is a steel plate corresponding to the lower plate 11, the partition plate 15 and the upper plate 19 in the first embodiment, and is the third steel plate. Is a steel plate corresponding to the flow path plates 16 to 18 in the embodiment. The partition plate 15 is a hole used for determining the quality of joining of the joined bodies joined in the first diffusion step described below, and one hole for introducing a fluid is formed in the flow path plates 12 to 14. did. Further, as shown in FIG. 6, the upper plate (shown as the upper plate 19 in the embodiment and the upper plate 19A in FIG. 6) is used to determine the quality of the bondability in the second diffusion joining step described later. A hole for introducing a fluid is formed in the flow path plates 16 to 18, and a diameter of 0.1 mm is formed in the area between the flow paths formed in the third steel plate when viewed from the direction perpendicular to the joint surface. Hole H was formed.

In this embodiment, first, one second steel plate, three first steel plates, and one second steel plate are laminated in this order, and then diffusion-bonded. Hereinafter, this step will be referred to as a first diffusion joining step. The first diffusion joining step was performed under the following conditions.
Initial degree of vacuum: 10 ^-2 Pa
Bonding temperature: 1100 ° C
Temperature rise time from room temperature to joining temperature: Approximately 2 hours
Soaking time: 2h
Average cooling rate from joining temperature to 400 ° C: 3.2 ° C / min Applied surface pressure: 0.5 to 5 MPa.

Next, the quality of the joining of the joined bodies joined in the first diffusion joining step was confirmed. The quality of the bonding was determined by putting a bonding body filled with 0.5 MPa of nitrogen gas into water in the flow path and determining whether bubbles were generated from the holes formed in the partition plate 15.

Next, the joined body joined in the first diffusion joining step, three third steel plates and one second steel plate were laminated in this order, and then diffusion-bonded. Hereinafter, this step will be referred to as a second diffusion joining step.

The conditions of the second diffusion joining step are almost the same as the conditions of the first diffusion joining. However, the applied surface pressure was 0.5 to 10 MPa. The experimental conditions and experimental results are shown in FIG. The amount of deflection shown in FIG. 5 was measured using a high-speed three-dimensional shape measuring system manufactured by Komusu Co., Ltd., which is a laser displacement meter. Regarding the quality of the joining in the second diffusion joining step, whether the joining body filled with 0.5 MPa of nitrogen gas is put into water and bubbles are generated from the holes formed in the upper plate 19. Judgment by whether.

As shown in FIG. 5, in Examples 1 to 7, a surface pressure of 0.5 to 3.5 MPa was applied to the second steel sheet having a plate thickness of 0.3 to 0.6 mm. As a result, the amount of deflection due to the first diffusion joining step was 30 μm or less. As a result, when a surface pressure of 3 to 9 MPa was applied in the second diffusion joining step, the second steel plate and the third steel plate were well joined and buckling did not occur. The length of the joined body obtained by joining the first steel plate, the second steel plate, and the third steel plate in the plate thickness direction is (thickness of the first steel plate, the second steel plate, and the third steel plate) × 3 × 0.95. It was determined that buckling did not occur when the amount was large, and it was determined that buckling occurred when (thickness of the first steel plate, the second steel plate, and the third steel plate) × 3 × 0.95 or less.

On the other hand, in Comparative Example 1, the amount of deflection of the second steel sheet was 20 μm, but the surface pressure in the second diffusion joining step was as small as 0.5 MPa, so that the second steel sheet and the third steel sheet were joined. There wasn't. Further, in Comparative Example 2, since the plate thickness of the second steel plate was 0.2 mm, the amount of deflection of the second steel plate in the first diffusion joining step was as large as 35 μm. Therefore, in the second diffusion joining step, the second steel plate and the third steel plate were not diffusion-bonded. Further, in Comparative Example 3, the third steel plate was deformed because a large surface pressure of 10 MPa was applied in the second diffusion joining step. Further, in Comparative Example 4 and Comparative Example 5, since the surface pressure in the first diffusion bonding was large, the amount of deflection of the second steel sheet was as large as 75 μm and 50 μm, respectively. Therefore, the second steel sheet and the third steel sheet did not join when a surface pressure of 5 MPa was applied in the second diffusion joining step.

14 Channel plate (austenitic stainless steel plate, first steel plate)
15 Partition plate (austenitic stainless steel plate, second steel plate)
16 Channel plate (austenitic stainless steel plate, third steel plate)
10 Heat exchanger (joint)

Claims (3)

Cr: 16.0% by mass to 20.0% by mass, Ni: 8.0% by mass to 15.0% by mass, Si: 0.001% by mass to 1.0% by mass, Mo: 0.0% by mass to A method for producing a bonded body, which is produced by diffusion-bonding a set of austenite-based stainless steel plates containing 3.0% by mass and C: 0.08% by mass or less.
A first steel sheet as the steel sheet in which a flow path is formed by applying a surface pressure of 0.5 to 3.5 MPa, and a second steel sheet as the steel sheet having a thickness of 0.3 to 0.7 mm. The first diffusion bonding step of diffusion bonding and
The second steel plate after the first diffusion joining step, and the third steel plate as the steel plate different from the first steel plate and the second steel plate, and the flow when viewed from a direction perpendicular to the joining surface. It includes a second diffusion joining step of diffusion joining a steel sheet having a flow path intersecting the road at 2.5 to 9.0 MPa.
A method for manufacturing a bonded body , wherein the second steel plate is a partition plate that partitions the flow path formed in the first steel plate and the flow path formed in the third steel plate . The steel plate has Cr: 16.0% by mass to 18.0% by mass, Ni: 10.0% by mass to 15.0% by mass, Si: 0.001% by mass to 1.0% by mass, Mo: 2. The method for producing a bonded body according to claim 1, further comprising 0% by mass to 3.0% by mass and C: 0.08% by mass or less. The steel plate has Cr: 16.0% by mass to 18.0% by mass, Ni: 12.0% by mass to 15.0% by mass, Si: 0.001% by mass to 1.0% by mass, Mo: 2. The method for producing a bonded body according to claim 1, further comprising 0% by mass to 3.0% by mass and C: 0.030% by mass or less.

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