TW201941854A - Method for manufacturing heat exchanger with excellent release property after the diffusion bonding process - Google Patents

Abstract

The present invention is to provide a method for manufacturing a heat exchanger, which is carried out by diffusion bonding in which deformation of a bonded material formed by a stainless steel plate is suppressed, with excellent releasability (detachability of a bonded material from a release member) after the diffusion bonding process. The manufacturing method of the heat exchanger is characterized in that release members 3 are arranged on the both surface sides of the bonding material 1, and bonding jigs 4 are arranged in a manner that the bonding material 1 is clamped through the release members 3 and bonding jigs 4 are arranged so as to sandwich the bonding material 1 through the release members 3, and a ratio (Fr/Fp) of the high-temperature strength (Fr) of the release members 3 at 1000 DEG C. to the high-temperature strength (Fp) of the bonding members 1 at 1000 DEG C. being 0.9 or more , and the bonding material 1 and the release members 3 are combined to carry out the diffusion bonding.

Description

Manufacturing method of heat exchanger

The present invention relates to a method for manufacturing a heat exchanger using diffusion bonding.

There are various types of heat exchangers. Among them, plate heat exchangers (plate-type heat exchangers) are widely used in electric water heaters, industrial equipment, and automobile air-conditioning devices due to their high heat exchange performance and easy installation and maintenance. The plate heat exchanger has a structure in which a plurality of thin metal plates (plates) are overlapped, and the passages of the high-temperature medium and the passages of the low-temperature medium are alternately adjacent to each other and formed between the laminated plates so as to be implemented through the plates It is constituted by a heat exchange effect between a high temperature medium and a low temperature medium.

As a method of laminating and assembling a plurality of plates, for example, Patent Literature 1 describes a joining method such as fastening, welding, brazing (brazing), and the like performed by a washer and a screw. For small and medium-sized heat exchangers, brazing is often used in consideration of pressure resistance. However, if the wavy-shaped plates are laminated and joined by brazing, the following welding defects peculiar to copper solder occur: melting loss during joining, cracking of the brazed portion, and melting due to melting. Burial of the flow path caused by the solder.

Therefore, the application of the diffusion bonding method was reviewed instead of the brazing method. Diffusion bonding is a method of performing bonding using mutual diffusion of base metal atoms generated at a bonding interface under a high temperature pressure in a vacuum or an inert atmosphere. The joint after diffusion bonding can obtain the same strength and corrosion resistance as the base material.

When diffusion bonding is performed, the laminated members to be bonded are pressed by pressing means, and the pressed state is maintained for a predetermined time. There is also a case where a release member such as a baffle or a spacer is sandwiched between a member to be joined and a pressing means, and diffusion bonding is performed. A carbon material is used as this mold release member because the required heat resistance does not break even at the temperature during diffusion bonding. For example, Patent Document 2 describes a diffusion bonding method using a carbon sheet having elasticity.

[Prior Art Literature] (Patent Literature) Patent Literature 1: Japanese Patent Laid-Open No. 2010-85094 Patent Literature 2: Japanese Patent Laid-Open No. 2014-128815

[Problems to be Solved by the Invention] However, from the viewpoint of improving the durability of a heat exchanger, it is desirable to use a stainless steel plate having excellent corrosion resistance as the metal plate. When a plate material composed of a stainless steel plate is laminated and diffusion-bonded, if a carbon material is used as a release member of an adjacent plate material, stainless steel and carbon will react, so it is not easy to disperse the material after the diffusion-bonding process is completed. The demolding member is removed from the plate material, resulting in a decrease in the demoldability of the two members. In addition, it may cause carburizing in which carbon penetrates into the stainless steel, resulting in a decrease in the corrosion resistance of the plate material and a problem that the surface roughness of the plate material becomes large and the surface characteristics are lowered.

In addition, in diffusion bonding, it is necessary to pressurize and heat the material to be joined using a hot pressing device or the like, so the plate of the material to be joined is kept under high pressure and high temperature. In addition, since the plate material forming the flow path in the body of the heat exchanger has a non-joint surface portion on the flow path side, the plate material forming the flow path is less constrained by the surroundings than other plate materials (see section Figure 3 (A)). Therefore, as shown in FIG. 3 (B), due to the heating of the diffusion bonding process, the plate material expands toward the flow path side in the above-mentioned non-joint surface portion and causes thermal deformation. Depending on the degree of thermal expansion, After the joining process is completed, cooling may be performed, and the deformed part may not be recovered, causing problems.

The present invention has been developed to solve the above problems. An object of the present invention is to provide a method for manufacturing a heat exchanger, which is implemented by diffusion bonding, which can maintain diffusion bonding even when the material to be joined is made of a stainless steel plate and deform the material to be joined. It is suppressed, and it is excellent in the mold release property (peelability of a to-be-joined material and a mold release member) after a diffusion bonding process.

[Technical Means for Solving the Problem] The present inventors focused on the material and characteristics of a release member that directly contacts a material to be joined (plate material). As a constituent material of the release member, a material that does not react with the stainless steel of the material to be joined is selected. Further, in the combination of the material to be joined and the release member, this is selected so as to be suitable for suppressing deformation after diffusion bonding. The characteristics of the two components achieve the above-mentioned object and complete the present invention. Specifically, the present invention provides the following technical features.

(1) A method for manufacturing a heat exchanger according to the present invention, which comprises laminating a plurality of materials to be joined made of stainless steel, heating and pressing them so as to diffusely join the materials to be joined, a method for producing the heat exchanger, A release member is disposed on both sides of the material to be joined, and a pressing jig is disposed so as to sandwich the material to be joined through the mold release member, and thereafter, the pressing device is pressed by the pressing device through the pressing The release member includes a steel material containing 1.5% by mass of Si (silicon), the high-temperature strength (Fr) of the release member at 1000 ° C and the temperature of the material to be joined at 1000 ° C. The high-temperature strength (Fp) ratio (Fr / Fp) is 0.9 or more, and the diffusion bonding is performed using a combination of the material to be joined and the release member.

(2) The manufacturing method of the heat exchanger as described in said (1) whose average cooling rate after heating in the said diffusion bonding is less than 1.2 degree-C / min.

(3) The method for manufacturing a heat exchanger according to the above (1) or (2), wherein the pressing jig is a carbon material jig.

(4) The method for manufacturing a heat exchanger according to any one of (1) to (3), wherein a release agent is applied to both sides of the release member.

[Effects of the Invention] The present invention, as described above, can provide a method for manufacturing a heat exchanger by using a combination of a material to be joined and a mold release member having the above-mentioned composition with respect to a component composition, a high-temperature strength, and a thermal expansion coefficient. Diffusion bonding is performed. This diffusion bonding can maintain diffusion bonding even when the material to be joined is made of a stainless steel plate, while suppressing deformation of the material to be joined, and having excellent release properties after the diffusion bonding process. .

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to these descriptions.

This embodiment relates to a method for manufacturing a heat exchanger, in which a plurality of materials to be joined made of stainless steel are laminated and heated and pressurized to diffusely join the materials to be joined. A release member is disposed on both sides of the material to be joined, and a pressing jig is disposed so as to sandwich the material to be joined through (through) the mold release member, and then a pressurizing device is used to pass through the pusher. The pressing fixture is used to press, thereby making the material to be joined, that is, the plate material diffusely joined to manufacture the heat exchanger.

(Material to be joined) FIG. 1 shows an outline of the material to be joined in the process of diffusion bonding. As a device for performing diffusion bonding, a hot pressing device capable of performing pressure and heating in a predetermined atmosphere can be used. As a to-be-joined material (plate material) to be diffusion-bonded, a laminated body obtained by laminating and laminating a plurality of plate materials is prepared and filled in a pressure heating device. In addition, the release member is arrange | positioned so that the both sides of this laminated body may be contacted. FIG. 1 is an example using a plate laminate 2 in which four plate materials 1 are stacked. In the pressure heating device, the pressing jigs 4 are arranged so as to respectively contact the two release members 3 disposed on the outside of the plate laminate 2. The pressing jig 4 is connected to a pressing shaft 5 of a pressing device. When the pressing mechanism (not shown) is operated, the pressing jig 4 is pressed by the pressing shaft 5 so as to sandwich the plate laminated body 2, a predetermined pressure is applied to the plate material 1, and the pressing is performed. The status is maintained for a specified time. In a pressure heating device that maintains a vacuum or an inert atmosphere, the plate laminate 2 of the material to be joined is pressurized and heated under predetermined conditions so that the material to be joined 1 is diffusion-bonded. In addition, the board material is not limited to four pieces. It is also possible to use a plurality of plate laminates 2 and join together to form an assembly in which a mold release member is inserted between the plate laminates. In addition, as the plate material 1 shown in FIG. 1 has a flow path (not shown) in the two inner pieces, the thickness is larger than the two outer pieces. The combination of the flow paths is not limited to the structure shown in FIG. 1.

The pressure device may be provided with a pressure mechanism such as a servo, a spring, and a hammer. In order to easily detach the material to be joined and the release member after the diffusion bonding, a release agent may be applied to the surface of the release member before the diffusion bonding.

A heat exchanger formed by laminating a plurality of plate materials allows a fluid to pass through a fine flow path formed by the plate materials to perform heat exchange between the high-temperature-side fluid and the low-temperature-side fluid through each plate material. Therefore, it is required that the mechanical strength (high-temperature strength) and corrosion resistance of the plate material in a high-temperature region must be good. From this viewpoint, the present embodiment uses stainless steel excellent in heat resistance and durability as the plate material. In order to improve the heat exchange performance, it is desirable to be able to form a thin plate.

(Release member) In the present embodiment, it is preferable to use a release member 3 made of a steel material containing 1.5% by mass or more of Si (silicon). Since the mold release member contacts the material to be joined during diffusion bonding and is placed under high temperature and pressure, it is required to have less damage and corrosion at high temperatures, and no reaction with the material to be joined. From the viewpoint of suppressing the reaction with the material to be joined, the release member of this embodiment is preferably configured using a steel material having a large Si content.

(Si content) The mold release member of this embodiment contains a steel material which contains 1.5 mass% or more of Si. Si is an easily oxidizable element and forms a strong oxide film on the surface of the release member. Since the base material of the release member is in contact with the material to be joined via this Si oxide film, the reaction at the interface between the release member and the material to be joined is hindered. The formation of the Si oxide film suppresses the adhesion and interfacial reaction between the two members. Therefore, after the diffusion bonding process is completed, the demolding member can be easily removed from the material to be joined with a small pulling force. Remove it. In addition, the Si oxide film prevents the components contained in the release member from penetrating into the material to be joined. Therefore, the stainless steel of the material to be joined can maintain good heat resistance and corrosion resistance, and maintain smooth surface characteristics. From such a viewpoint, it is preferable that the release member contains a steel material, and the steel material contains 1.5% by mass or more of Si.

Moreover, even if a Si oxide film is formed on the surface of the release member, if the shape of the release member is changed too much due to external load, thermal expansion and contraction, etc., a part of the oxide film may be damaged. Sex. At this time, since the material to be joined and the release member may be in a space that is not in contact with each other through the oxide film, the release property of the two members may be reduced. From this point of view, in order to form a stable and strong oxide film, it is also desirable to apply a steel material containing a predetermined amount of Si to a release member.

In consideration of mechanical strength and corrosion resistance in a high-temperature environment, a constituent material of the release member of this embodiment is suitable for use of an austenite-based stainless steel material having excellent heat resistance, durability, and formability. Specifically, a steel material having the following composition can be used.

(1) A stainless steel material containing C (carbon) of 0.1% by mass or less, Si (silicon) of 1.5 to 5.0% by mass, Mn (manganese) of 2.5% by mass or less, and P (phosphorus) of 0.06% by mass or less. , S (sulfur) of 0.02 mass% or less, Ni (nickel) of 8.0 to 15.0 mass%, Cr (chromium) of 13.0 to 23.0 mass%, and N (nitrogen) of 0.2 mass% or less.

(2) A stainless steel material comprising, in the composition of (1) above, Mo (molybdenum) of 3.0% by mass or less, Cu (copper) of 4.0% by mass or less, and Nb (niobium) of 0.8% by mass or less. One or more selected from the group consisting of Ti (titanium) of 0.5% by mass or less, V (vanadium) of 1.0% by mass or less, and B (boron) of 0.02% by mass or less.

(3) A stainless steel comprising the composition of (1) or (2) from 0.2% by mass or less of Al (aluminum) and 0.2% by mass or less of REM (rare earth metals) One or more selected from the group consisting of 0.2% by mass of Y (yttrium), 0.1% by mass of Ca (calcium), and 0.1% by mass of Mg (magnesium).

The components contained in the stainless steel will be described.

C (carbon) enhances the strength and hardness of steel by solid solution strengthening. On the other hand, if the C content is too large, the workability and toughness of the steel are reduced, so the C content is preferably 0.1% by mass or less.

Si (silicon) is formulated to form a strong oxide film on the surface of the release member as described above, and it is preferably contained at 1.5% by mass or more. With the formed Si oxide film, the reaction at the interface between the release member and the material to be joined is hindered. Therefore, after the diffusion bonding, the release member can be easily removed from the material to be joined with a small pulling force. Come down. In addition, the Si oxide film prevents the components contained in the release member from penetrating into the material to be joined, so it is possible to maintain the good heat resistance and corrosion resistance of the material to be joined and maintain smooth surface characteristics. If the Si content is less than 1.5% by mass, the above-mentioned effect by the formation of an oxide film cannot be sufficiently obtained. In addition, even if it is added more than 5.0% by mass, in addition to the above-mentioned effects being almost saturated (which cannot be further improved), and appropriate workability cannot be obtained due to hardening, as long as it contains 5.0% by mass or less.

Mn (manganese) is an element that improves high-temperature oxidation characteristics. If it contains too much, workability may be reduced, so the Mn content is preferably 2.5% by mass or less.

Cr (chromium) is an element that forms a passive film to impart corrosion resistance, and can improve corrosion resistance. If it is less than 13.0% by mass, the effect is insufficient. When it exceeds 23.0 mass%, workability will fall. Therefore, the Cr content is preferably 13.0 to 23.0% by mass.

Ni (nickel) is an element necessary for stabilizing the Vostian iron phase and maintaining corrosion resistance, and is also effective for workability. If the content is less than 8.0% by mass, these effects are insufficient, and if it exceeds 15.0% by mass, the effect is saturated and the cost is increased. Therefore, the Ni content is preferably 8.0 to 15.0% by mass.

P (phosphorus) and S (sulfur) are mixed and become unavoidable impurities. It is desirable that the content is as low as possible, and in a range that does not adversely affect processability and material characteristics, it is preferable that the P content is 0.06 mass% or less and the S content is 0.02 mass% or less, respectively.

N (nitrogen) is an element used to effectively stabilize Vostian iron, and further, it can improve the high temperature strength and corrosion resistance of stainless steel together with Cr and Ni. On the other hand, if it is added too much, the manufacturability is reduced, so the N content is preferably 0.2% by mass or less.

Mo (molybdenum) and Cu (copper) are elements useful for improving high-temperature strength and corrosion resistance. Mo content and Cu content are preferably both 0.02% by mass or more. On the other hand, if too much Mo is contained, a ferrite phase may be formed and workability may be reduced. Therefore, the Mo content is preferably 3.0% by mass or less. If too much Cu is contained, it may cause a decrease in hot workability. Therefore, the Cu content is preferably 4.0% by mass or less.

Nb (niobium), Ti (titanium) and V (vanadium) can effectively improve high temperature strength. The Nb content is preferably 0.01% by mass or more, the Ti content is preferably 0.01% by mass or more, and the V content is preferably 0.01% by mass or more. On the other hand, if too many various elements are contained, the workability is reduced, so the Nb content is preferably 0.8% by mass or less, the Ti content is preferably 0.5% by mass or less, and the V content is preferably 1.0% by mass or less.

B (boron) is an element for improving hot workability. The B content is preferably 0.0002% by mass or more. On the other hand, if too much is added, boride will be precipitated and workability will be reduced, so the B content is preferably 0.02% by mass or less.

One or more selected from the group consisting of Mo, Cu, Nb, Ti, V, and B may be added.

Al (aluminum), REM (rare earth metal element), Y (yttrium), Ca (calcium), and Mg (magnesium) can effectively improve high-temperature oxidation resistance, and one or more of these elements can be selected and added. The Al content is preferably 0.001 mass% or more, the REM content is preferably 0.001 mass% or more, the Y content is preferably 0.0002 mass% or more, the Ca content is preferably 0.0002 mass% or more, and the Mg content is preferably 0.0002 mass% or more. However, if too many elements are contained, the workability is reduced, so the Al content is preferably 0.2% by mass or less, the REM content is preferably 0.2% by mass or less, the Y content is preferably 0.2% by mass or less, and the Ca content is preferably 0.1 mass% or less, and Mg content is preferably 0.1 mass% or less.

The shape of the release member can be appropriately selected in accordance with the shape of the material to be joined. The plate material of a general plate heat exchanger has a plate shape, so a mold release member disposed in contact with the plate material is used as a mold release plate. The thickness of the release plate is preferably 2 to 10 mm, and more preferably 3 to 8 mm.

(High temperature strength ratio) Furthermore, in this embodiment, it is preferable that the ratio (Fr / Fp) of the high temperature strength (Fr) of the release member at 1000 ° C to the high temperature strength (Fp) of the material to be joined at 1000 ° C be In a method of 0.9 or more, diffusion bonding is performed using a combination of a material to be joined and a release member.

The release member is sandwiched between the material to be joined and the pressing jig during diffusion bonding and is exposed to high pressure and high temperature. Therefore, if the high-temperature strength of the release member is low, deformation may occur. If the release member is deformed, the uniformity of the pressurization of the material to be joined in contact with the release member is impaired, and there is a possibility that a defective portion may be caused. Therefore, the present embodiment reviews the high-temperature characteristics of the release member based on the high-temperature strength at 1000 ° C., which is a standard processing temperature used in diffusion bonding.

Specifically, it evaluated based on the ratio (Fr / Fp) of the high temperature strength (Fr) at 1000 degreeC of a mold release member, and the high temperature strength (Fp) at 1000 degreeC of a to-be-joined material. As the release member, it is preferable to use a steel material having a high-temperature strength ratio (Fr / Fp) of 0.9 or higher at 1000 ° C. If the ratio of the high-temperature strength of the demolding member to the high-temperature strength of the material to be joined is less than 0.9, there is a possibility that the demolding member may be excessively deformed due to the pressure caused by the pressing fixture. Due to the deformation of the release member, the pressurized state of the material to be joined becomes uneven, and deformation of the material to be joined may be caused. Therefore, from the viewpoint of suppressing deformation, it is preferable to use a combination of the release member and the material to be joined having the high-temperature strength ratio of 0.9 or more, and the high-temperature strength ratio is more preferably 1.0 or more.

(Coefficient of Thermal Expansion) A preferred combination of the material to be joined and the release member, the ratio of the coefficient of thermal expansion (Tr) of the release member to the coefficient of thermal expansion (Tp) of the material to be joined at 30 ° C to 1000 ° C ( Tr / Tp) is 0.90 to 1.60. Both the material to be joined and the release member undergo elastic deformation due to thermal expansion when heated. If there is a difference in thermal expansion between the two members, the two will be restrained from each other's deformation to accumulate strain, and depending on the degree of their strain, there is a possibility of reaching plastic deformation.

In particular, the material to be joined that forms the heat medium flow path (hollow portion) in the heat exchanger has a portion that becomes a non-joint surface on the opposite surface side even if it is in contact with the mold release member on one surface side. In contrast to the state where the joints of the materials to be joined overlap are constrained by the surroundings, the above-mentioned hollow portion is not constrained by the surroundings, so it is prone to elastic deformation due to thermal expansion (see FIG. 3 (B)). If this degree of elastic deformation is too large, it may reach plastic deformation and it may be difficult to recover the shape.

When a mold release member having a relatively low high temperature strength is used, the mold release member has lower deformation resistance than the plate material. Therefore, it is preferable that the thermal expansion coefficients of both the material to be joined and the mold release member are the same. In this embodiment, this thermal characteristic can be evaluated based on the ratio (Tr / Tp) of the thermal expansion coefficient (Tr) of the release member to the thermal expansion coefficient (Tp) of the material to be joined. When a release member having a relatively high high-temperature strength is used, the ratio of the thermal expansion coefficient (Tr / Tp) may be within a range of ± 5% centered at 1.0, that is, 0.95 to 1.05.

(Average cooling rate) The average cooling rate after heating during diffusion bonding is preferably less than 1.2 ° C / minute. The material to be bonded and the release member undergo thermal expansion during diffusion bonding. On the other hand, they will shrink and return to their original shape during the cooling process after diffusion bonding. If there is a thermal expansion difference between the material to be joined and the release member, the two members will be restrained from each other due to the shrinkage change during cooling, and the deformation will accumulate. If this shrinkage change is too large, there is a possibility of inducing plastic deformation. Therefore, this embodiment focuses on the average cooling rate after the completion of the diffusion bonding. When processed at an average cooling rate of less than 1.2 ° C / min, the amount of deformation remaining after cooling can be suppressed. If the cooling rate is higher than this, the change in thermal expansion and contraction is too large, so that the amount of deformation remaining after cooling is too large and unsatisfactory. The average cooling rate may be controlled within a temperature range from the holding temperature during diffusion bonding to approximately 400 ° C.

(Pushing jig) The pressing jig is connected to a pressurizing mechanism of a pressurizing device and is a member that transmits a pressing force to a material to be joined. Since it is required to have heat resistance that does not break at the temperature during diffusion bonding, it is preferable to use a carbon material for the pressing jig.

(Release Agent) In the present invention, it is preferable to apply a release agent to both sides of the release member. For example, boron nitride-based spraying such as hexagonal boron nitride powder (h-BN) can be used. The coating thickness of the release agent may be three times or more (approximately approximately 10 μm) the average particle size (for example, approximately 3 μm) of the release agent powder.

[Examples] Hereinafter, examples of the present invention will be described. The present invention is not limited to the following examples, and can be appropriately changed.

(Production of test materials) 30 kg of steel material No. 1 to steel material No. 9 having the chemical composition shown in Table 1 were melted by vacuum melting, and the obtained ingot was forged into a steel plate having a thickness of 30 mm. Next, a hot-rolled sheet having a thickness of 6 mm was prepared by hot rolling at 1200 ° C, and then a soaking annealing was performed at 1100 ° C for 60 seconds to obtain a hot-rolled annealed sheet. This hot-rolled annealed sheet was cold-rolled to a thickness of 3.0 mm, and then subjected to final annealing at 1100 ° C. for 30 seconds. The final refined thickness was set to 3 mm, and the surface was refined to obtain 2B stainless steel or 2D stainless steel (No. 2B finish or No. 2D finish) to obtain a cold rolled annealed sheet. In addition, for the steel materials No. 5 and steel No. 6 which are used as plates, cold rolling and annealing are performed, the thickness of the finally refined plate is set to 0.4 mm and 1.0 mm, and the surface is refined to obtain 2B stainless steel or 2D. Stainless steel to obtain a cold rolled annealed sheet. A 210 mm × 160 mm size plate was cut out of the cold-rolled annealed plate to prepare a test material. These test materials are used to test materials to be joined or demoulded members. As shown in Table 1, the remainder is Fe (iron) and inevitable impurities.

Steel numbers 1 to 5 are Vostian iron-based stainless steels, and steel numbers 6 to 9 are fat-iron stainless steels.

[Table 1]

(Measurement of high-temperature strength) Using the obtained test material, a high-temperature tensile test was performed at a temperature of 1000 ° C and a strain rate of 0.3% / minute based on JIS G 0567, and a 0.2% safety limit stress was measured ( proof stress). In this specification, this measured value is set to a high-temperature strength at 1000 ° C. Table 1 shows the measurement results (unit: MPa). The ratio (Fr / Fp) of the high-temperature strength (Fr) of the release member to the high-temperature strength (Fp) of the material to be joined was calculated based on the measured values. The results are shown in Table 2.

(Setting of thermal expansion coefficient) Using the obtained test material, based on JIS Z 2285, a differential expansion analysis device (infrared heating type thermal expansion measurement device (TMA) manufactured by Rigaku Corporation, standard test material is quartz) was used at 30 The heating is performed at a temperature rising rate of 1 ° C / second from ℃ to 1000 ° C. The expansion amount of the test piece at this time was measured to calculate a thermal expansion coefficient (α30-1000 ° C) at 30 ° C to 1000 ° C. The measurement results are shown in Table 1 (unit: × 10 ^-6 / ° C).

(Join test) Four test materials of the material to be joined (plate material) and two test materials of the release member (release template) were combined to produce a test assembly. As shown in Table 2, in this test, four pieces of a test material composed of a steel plate number 5 were used as the plate material. A test material having two plate materials (thickness: 1.0 mm / piece) having openings that serve as a flow path was used, and two plates that did not have the above openings were placed as heat transfer plates so as to sandwich the two plate materials. A plate material (thickness: 0.4 mm / piece) was stacked with a test material consisting of steel number 1 to steel number 3.0 and having a thickness of 3.0 mm as a release member. A carbon material jig is used as the pressing jig. Hexagonal boron nitride powder (boron spray manufactured by YK Inoas Co. Ltd) was used as a release agent on both sides of the release member. A diffusion bonding process was performed on the test assembly using a hot pressing device using the following pressure conditions and heating conditions.

• Atmosphere: Set the initial vacuum to 1 × 10 ^-2 Pa or less. • Joining temperature: 1080 ° C. • Heating time: about 2 hours from normal temperature to joining temperature. • Soaking time (joining) time: 3 hours. • Average cooling rate: From 1080 ° C to 400 ° C, it is 3.2 ° C / min (Type A) or 1.1 ° C / min (Type B) • Pressure: Surface pressure 2MPa

Fig. 2 shows a type of heating and cooling applied to the above-mentioned diffusion bonding process. The A-type and B-type in FIG. 2 show the above-mentioned two types after the average cooling rate is changed. After cooling to normal temperature, the test assembly was taken out of the hot pressing device, and the following evaluation tests were performed with respect to deformation suppression and mold release properties.

(Evaluation about deformation suppression) The deformation suppression was evaluated based on the amount of deformation of the plate material after diffusion bonding. A method for measuring the amount of deformation will be described. Fig. 3 is a schematic diagram showing a cross section of a test assembly. FIG. 3 (A) shows a state before diffusion bonding, and shows a test assembly 14 composed of four sheets of plate materials 11a to 11dc and two strippers 13 and a pressing fixture 15 made of carbon material. Pressurized with the clamped. FIG. 3 (B) shows the state of the test assembly 14 after diffusion bonding. In the test assembly 14 after diffusion bonding, the plate materials 11 a and 11 d facing the cavity portion 16 side are restricted by the release plate 13 and other plate materials 11 b and 11 c except for the cavity portion side. Therefore, when the plate materials 11 a and 11 c are expanded by heating, It bends to the side of the cavity and deforms. If the shape is not restored by the shrinkage change during cooling, a curved shape will remain. The height 17 of the highest point after deformation is measured using the surfaces of the plate materials 11 a and 11 d in contact with the release plate 13 as a reference, and the largest value among them is obtained. In this specification, this value is referred to as the amount of deformation of the plate material. Based on this amount of deformation, the deformation state after diffusion bonding is evaluated. The height 17 is measured using a high-speed 3-dimensional shape system manufactured by CMOS Corporation. From the viewpoint of suppressing deformation, the evaluation is good when the deformation amount is less than 30 μm (◎), the evaluation is appropriate when the deformation amount is 30 μm to 50 μm (○), and the evaluation is not appropriate when the deformation amount exceeds 50 μm (×) .

(Evaluation of mold release property) In order to evaluate the mold release property after joining using a test assembly, a peeling test of a plate material and a mold release was performed. The outline is shown in Figure 4. A stretching device (not shown) and a jig with a suction cup 25 attached to the tip of two wires 26 are prepared. The suction cups 25 of the jig were mounted on the surfaces of two release plates 23 in the test assembly 24 after diffusion bonding. After a hammer 27 having a predetermined weight is connected to one of the pressing wires 26, the wire 26 of the other jig is pulled up by a stretching device. Both sides of the test assembly 24 were stretched by the weight of the hammer 27, thereby visually observing whether or not the plate material 21 and the release plate 23 were peeled to confirm the presence or absence of peeling. Change the weight of the hammer 27 and repeat the test in the same procedure. Regarding the evaluation criteria, it is expected that the plate material and the release plate after the diffusion bonding can be disassembled (separated) with a small force. Therefore, when the plate material and the release plate are peeled with a hammer weight of 5 kg or less, the release property is judged to be good. (○) When the plate material and the release plate are peeled off with a hammer weight of 20 kg or less, the mold release property is judged to be slightly insufficient (△). When the weight of the hammer exceeds 20 kg, the plate material and the release plate cannot be peeled off. , The mold releasability was judged to be bad (×).

(Test results) In this test, a plate material made of Vostian iron-based stainless steel with steel number 5 and a plate material made of ferrous iron-based stainless steel with steel number 6 were used. Eighteen kinds of test assemblies composed of a release template composed of various stainless steels of ～ 9 are used to perform tests on high temperature strength, thermal expansion coefficient, deformation suppression, and mold release. Table 2 shows the test results. For the deformation suppression and mold release properties, two types of heating and cooling types were used, and three test assemblies were used for testing. For the suppression of deformation, the average value of the three deformation amounts was evaluated. The mold release was evaluated by an average of the three results.

[Table 2] The bottom line is outside the scope of the present invention.

Examples 1 to 6 of the present invention are examples in which diffusion bonding is performed by using a test assembly constituted by strippers of steel numbers 1 to 3, respectively. Either the amount of deformation after diffusion bonding is good (◎) or appropriate (适当) and is within a range of 50 μm or less, and a diffusion bonded product with suppressed deformation can be obtained. It is presumed that if a combination of a material to be joined and a release sheet corresponding to the present invention is used, thermal expansion and contraction due to heating and cooling during the diffusion bonding process are appropriately performed and deformation can be suppressed.

With regard to the releasability of Examples 1 to 6 of the present invention, the material to be joined and the release plate can be pulled apart and peeled off with a small tensile force. By using a combination of the material to be joined and the release sheet equivalent to the present invention, the release sheet can be easily removed from the material to be joined after diffusion bonding. It is presumed that the Si oxide film formed on the surface of the demolding plate hinders the interface reaction between the material to be joined and the demolding plate, so that the adhesion between the two members is suppressed and the demoldability is improved.

Furthermore, in Examples 1 to 6 of the present invention, it was observed that the average cooling rate after diffusion bonding was implemented at 3.2 ° C / min (Type A) and 1.1 ° C / min (Type B), compared with the A type. In the cooled test assembly, the effect of suppressing the deformation of the test assembly cooled by the B-type with a smaller average cooling rate is further improved. It is presumed that if the cooling rate is small, the degree of change in thermal expansion and contraction is reduced, so that the accumulation of strain is reduced and deformation is suppressed.

On the other hand, in Comparative Examples 1 to 12, a release template composed of steel material number 4 to steel material number 9 was used. In Comparative Examples 1 to 12, the Si content of the mold release steel was less than 1.5% by mass and was outside the range of the present invention. In either case, the releasability was slightly insufficient (Δ) or unsuitable (×), and it was not easy to disassemble after diffusion bonding.

Furthermore, Comparative Examples 3 to 6, 10, and 12 had a high-temperature strength ratio of less than 0.9, so the deformation after diffusion bonding was large, and the deformation suppression after diffusion bonding was not suitable (×).

Based on the above test results, it is possible to provide a method for manufacturing a heat exchanger, which uses a mold release member containing steel, the steel contains 1.5% by mass or more of Si, and the high temperature strength (Fr) and temperature of the mold release member at 1000 ° C. The high-temperature strength (Fp) ratio (Fr / Fp) of the bonding material at 1000 ° C is 0.9 or more, and the diffusion bonding is performed by using a combination of the material to be bonded and the mold release member. The material can also maintain the diffusion bonding property while suppressing the deformation of the material to be bonded, and it is excellent in the release property after the diffusion bonding process.

1, 11a, 11b, 11c, 11d, 21‧‧‧ plate material (material to be joined)

2‧‧‧ plate laminate

3, 13, 23, ‧‧‧ demoulding members

4, 15‧‧‧ Pushing fixture

5‧‧‧Pressure shaft

14, 24‧‧‧ test assembly

16‧‧‧ Hollow

17‧‧‧ height (deformation)

25‧‧‧ Suction cup

26‧‧‧Wire

27‧‧‧hammer

FIG. 1 is a schematic diagram for explaining an embodiment of a material to be joined in a hot press device. Fig. 2 is a diagram showing a heating and cooling pattern of a diffusion bonding process in the embodiment. FIG. 3 is a schematic diagram for explaining a method for measuring the amount of deformation in the examples. FIG. 3 (A) is a diagram showing a state where a test assembly before diffusion bonding is provided; FIG. 3 (B ) Is a diagram showing a state where the plate material has been deformed after the diffusion bonding. FIG. 4 is a schematic diagram for explaining a method for measuring the releasability in Examples.

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Claims (4)

A method for manufacturing a heat exchanger, comprising laminating a plurality of materials to be joined made of stainless steel, heating and pressurizing them to diffusely join the materials to be joined, and a method for manufacturing the heat exchanger, On both sides of the mold release member, a pressing jig is arranged so that the material to be joined is sandwiched by the mold releasing member, and thereafter, the pressing jig is pressed by the pressing device and the pressing jig. The demolding member includes steel, the steel contains 1.5% by mass or more of silicon, and the ratio of the high-temperature strength Fr of the demolding member at 1000 ° C. to the high-temperature strength Fp of the joined material at 1000 ° C. is Fr / Fp At least 0.9, the diffusion bonding is performed using a combination of the material to be joined and the release member. The method for manufacturing a heat exchanger according to claim 1, wherein the average cooling rate after heating in the diffusion bonding is less than 1.2 ° C / min. The method for manufacturing a heat exchanger according to claim 1 or 2, wherein the pressing jig is a carbon material jig. The method for manufacturing a heat exchanger according to any one of claims 1 to 3, wherein a release agent is applied to both sides of the release member.