JP7033847B2 - Release member - Google Patents

Description

The present invention relates to a stainless steel material for a diffusion joining jig, which is excellent in deformation suppression and releasability. The present invention also relates to a mold release member suitable for a manufacturing method by diffusion bonding.

There are various types of heat exchangers. Of these, plate heat exchangers (flat plate heat exchangers) are widely used in electric water heaters, industrial equipment, automobile air conditioners, etc. because they have high heat exchange performance and are easy to install and maintain. There is. The plate heat exchanger has a structure in which a plurality of thin metal plates (plates) are laminated, and the passages of a high temperature medium and the passages of a low temperature medium are alternately formed between the laminated plates so as to be individually adjacent to each other. It is configured to exchange heat between the high temperature medium and the low temperature medium via the plate.

As a method of laminating and assembling a plurality of plates, for example, Patent Document 1 describes a joining method such as fastening, welding, and brazing with a gasket and a screw. Small and medium-sized heat exchangers are often brazed in consideration of pressure resistance. However, when plates with a wavy shape are laminated and joined by brazing, joining defects peculiar to brazing materials such as melting damage, cracking of the brazing part, and burial of the flow path by the molten brazing may occur. ..

Therefore, the application of the diffusion bonding method instead of the brazing method is being considered. Diffusion bonding is a method of bonding using the mutual diffusion of base metal atoms generated at the bonding interface under high temperature pressure in a vacuum or an inert atmosphere. The diffusion-bonded joint has the same strength and corrosion resistance as the base material.

When performing diffusion bonding, the laminated members to be joined are pressed by a pressurizing means, and the pressurized state is maintained for a predetermined time. A mold release member such as a backing plate or a spacer may be sandwiched between the member to be joined and the pressurizing means for diffusion bonding. As the mold release member, a carbon material is used because it is required to have heat resistance to the temperature at the time of diffusion bonding and not to be damaged. For example, Patent Document 2 describes a diffusion bonding means using an elastic carbon sheet.

Japanese Unexamined Patent Publication No. 2010-85094 Japanese Unexamined Patent Publication No. 2014-128815

By the way, from the viewpoint of improving the durability of the heat exchanger, a stainless steel plate having excellent corrosion resistance is used as the metal plate. When a plate material made of stainless steel plate is laminated and diffusion-bonded, if a carbon material is used as a mold release member adjacent to the plate material, a reaction between the stainless steel and carbon occurs. It becomes difficult to remove the mold release member from the material, and the mold releasability of both members is reduced. Further, there are problems that the corrosion resistance of the plate material is lowered and the surface roughness of the plate material is increased due to the carburization in which carbon permeates into the stainless steel, and the surface texture is deteriorated.

Further, in diffusion bonding, it is necessary to pressurize and heat the material to be bonded by using a hot press device or the like, so that the plate of the material to be bonded is held under high pressure and high temperature. Further, since the plate material forming the flow path in the main body of the heat exchanger has a non-bonded surface portion on the flow path side, the degree of restraint from the surroundings is smaller than that of other plate materials ((FIG. 3). See A)). Therefore, for example, as shown in FIG. 3B, heating of the diffusion bonding treatment may cause thermal deformation that expands the plate material toward the flow path side in the non-bonded surface portion, and depending on the degree of the thermal expansion. Has a problem that the deformed portion is not restored even if it is cooled after the diffusion bonding process is completed.

The present invention has been devised to solve the above problems. Stainless steel for diffusion bonding jigs that suppresses deformation of the material to be bonded while maintaining the diffusion bonding property of the material to be bonded, and has excellent mold releasability (peeling property between the material to be bonded and the release member) after the diffusion bonding process. The purpose is to provide steel materials.

The present inventors have focused on the material and characteristics of the mold release member that comes into direct contact with the material to be joined (plate material). We have found that the above object can be achieved by selecting a material that does not react with the material to be joined and is suitable for suppressing deformation after diffusion bonding as a constituent material of the release member, and to complete the present invention. I arrived. Specifically, the present invention provides the following.

(1) The present invention is a stainless steel material containing 1.5% by mass or more of Si, and the high temperature strength (Fr) of the stainless steel material at 1000 ° C. and the high temperature of the material to be joined joined by diffusion bonding at 1000 ° C. A stainless steel material for diffusion joining jigs having a ratio (Fr / Fp) to strength (Fp) of 0.9 or more and excellent deformation suppression and releasability.

(2) In the present invention, the stainless steel material has C: 0.1% by mass or less, Si: 1.5 to 5.0% by mass, Mn: 2.5% by mass or less, P: 0.06% by mass or less. , S: 0.02% by mass or less, Ni: 8.0 to 15.0% by mass, Cr: 13.0 to 23.0% by mass, N: 0.2% by mass or less, and the balance is Fe and unavoidable. The stainless steel material for diffusion bonding jigs described in (1) above, which has a composition composed of target impurities and is excellent in deformation suppression and releasability.

(3) In the present invention, the stainless steel material further comprises Mo: 3.0% by mass or less, Cu: 4.0% by mass or less, Nb: 0.8% by mass or less, Ti: 0.5% by mass or less, V: 1.0% by mass or less, B: Stainless steel material for diffusion joining jig, which contains one or more selected from 0.02% by mass or less and has excellent deformation suppression and releasability according to (2) above. Is.

(4) In the present invention, the stainless steel material further contains Al: 0.2% by mass or less, REM: 0.2% by mass or less, Y: 0.2% by mass or less, Ca: 0.1% by mass or less, Mg: The stainless steel material for diffusion joining jigs according to (2) or (3) above, which contains one or more selected from 0.1% by mass or less and has excellent deformation suppression and releasability.

(5) The present invention is a mold release member made of the stainless steel material according to any one of (1) to (4) above.

In the present invention, by using the combination of the material to be joined and the release member having the above configuration, the deformation of the material to be bonded is suppressed while maintaining the diffusion bonding property of the material to be bonded, and the diffusion bonding treatment is performed. It is possible to provide a stainless steel material for a diffusion joining jig which is excellent in releasability after being formed.

It is a schematic diagram for demonstrating embodiment of the material to be joined in a hot press apparatus. It is a figure which shows the heating and cooling patterns of the diffusion bonding treatment in an Example. It is a schematic diagram for demonstrating the method of measuring the deformation amount in an Example. (A) is a diagram showing a state in which the test assembly before diffusion bonding is set, and (B) is a diagram showing a state in which the plate material after diffusion bonding is deformed. It is a schematic diagram for demonstrating the measurement method about the releasability in an Example.

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

The present embodiment relates to a diffusion bonding jig used in a method for manufacturing a heat exchanger in which a plurality of materials to be bonded made of stainless steel are laminated, heated and pressurized, and the materials to be bonded are diffusion bonded. In the above manufacturing method, a mold release member is arranged on both sides of the material to be joined, a presser jig is arranged so as to sandwich the material to be joined via the mold release member, and then the presser jig is used. By pressing with a pressurizing device, the plate material to be joined is diffusion-bonded to manufacture a heat exchanger. In the present embodiment, the mold release member of the diffusion joining jig is arranged between the plate material and the holding jig.

(Material to be joined)
FIG. 1 shows an outline of the material to be bonded to be subjected to the diffusion bonding process. As a device for performing diffusion bonding, a hot press device or the like capable of pressurizing and heating in a predetermined atmosphere is used. The material to be bonded (plate material) to be diffusion-bonded is prepared as a laminated body in which a plurality of plate materials are stacked and laminated, and is loaded in a pressure heating device. Then, the mold release member is arranged so as to be in contact with both sides of the laminated body. FIG. 1 is an example using a plate laminate 2 in which four plate materials 1 are stacked. In the pressurizing and heating device, the pressing jig 4 is arranged so as to be in contact with each of the two mold release members 3 arranged on the outside of the plate laminated body 2. The presser jig 4 is connected to a pressurizing shaft 5 of a pressurizing device. When the pressurizing mechanism (not shown) is operated, the presser jig 4 presses the plate laminate 2 through the pressurizing shaft 5 so as to sandwich the plate laminate 2, a predetermined pressure is applied to the plate material 1, and the pressurizing state is maintained for a predetermined time. Be retained. In the 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, and the plate material 1 is diffusion-bonded. The number of plate materials is not limited to four. A plurality of plate laminates may be used to join an assembly in which a mold release member is inserted between the plate laminates. Further, since the plate material 1 shown in FIG. 1 is provided with a flow path (not shown) on the inner two plates, the plate material 1 is thicker than the outer two plates. The combination of flow paths is not limited to the structure shown in FIG.

The pressurizing device may be any device provided with a pressurizing mechanism such as a servo, a spring, and a weight. A mold release agent may be applied to the surface of the mold release member before diffusion bonding so that the material to be joined and the mold release member can be easily removed after diffusion bonding.

In a heat exchanger in which a plurality of plate materials are laminated, a fluid passes through a narrow flow path formed by the plate materials, and heat is exchanged between the high temperature side fluid and the low temperature side fluid through 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, it is desirable to have a thin plate shape in order to improve the heat exchange performance.

(Release member)
In this embodiment, 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 is placed under high temperature and high pressure in contact with the material to be bonded at the time of diffusion bonding, it is required that there is little damage or corrosion at high temperature and that the release member does not react with the material to be bonded. The mold release member 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 material to be joined.

(Si content)
The mold release member according to the present embodiment contains a steel material containing 1.5% by mass or more of Si. Si is an easily oxidizing element and forms a strong oxide film on the surface of the release member. Since the base material of the release member and the material to be joined come into contact with each other through the Si oxide film, the reaction at the interface between the release member and the material to be joined is hindered. Since the formation of this Si oxide film suppresses adhesion and interfacial reaction between both members, the release member can be easily removed from the material to be joined with a small pulling force after the diffusion bonding process is completed. .. In addition, since the components contained in the release member are also inhibited from penetrating into the inside of the material to be bonded by the above-mentioned Si oxide film, the good heat resistance and corrosion resistance of the stainless steel of the material to be bonded are maintained, and at the same time, the good heat resistance and corrosion resistance of the stainless steel to be bonded are maintained. Smooth surface texture is maintained. From such a viewpoint, the mold release member preferably contains a steel material containing 1.5% by mass or more of Si.

Further, even if a Si oxide film is formed on the surface of the release member, if the shape change of the release member due to an external load or thermal expansion / contraction is excessive, the oxide film may be partially destroyed. There is. In that case, since there is a portion where the material to be joined and the release member are in close contact with each other without passing through the oxide film, the release property of both members may be deteriorated. From this point of view, it is desirable to apply a steel material containing a certain amount of Si or more to the mold release member so that a stable and strong oxide film can be formed.

Considering the mechanical strength and corrosion resistance in a high temperature environment, the constituent material of the mold release member according to the present embodiment is preferably an austenitic stainless steel material having excellent heat resistance, durability, moldability, etc., and specifically, austenitic stainless steel material is preferable. Steel materials having the following composition can be used.

(1) C: 0.1% by mass or less, Si: 1.5 to 5.0% by mass, Mn: 2.5% by mass or less, P: 0.06% by mass or less, S: 0.02% by mass or less , Ni: 8.0 to 15.0% by mass, Cr: 13.0 to 23.0% by mass, N: 0.2% by mass or less, and the balance is Fe and unavoidable impurities.

(2) Further, in the composition of the above (1), Mo: 3.0% by mass or less, Cu: 4.0% by mass or less, Nb: 0.8% by mass or less, Ti: 0.5% by mass or less, V. A stainless steel material containing at least one selected from: 1.0% by mass or less and B: 0.02% by mass or less.

(3) Further, in the composition of the above (1) or (2), Al: 0.2% by mass or less, REM: 0.2% by mass or less, Y: 0.2% by mass or less, Ca: 0.1% by mass. Hereinafter, a stainless steel material containing one or more selected from Mg: 0.1% by mass or less.

The components contained in the above stainless steel material will be described.

C improves the strength and hardness of steel by solid solution strengthening. On the other hand, when the C content is high, the workability and toughness of the steel are lowered, so that the C content is preferably 0.1% by mass or less.

As described above, Si is blended to form a strong oxide film on the surface of the release member, and is preferably contained in an amount of 1.5% by mass or more. Since the formed Si oxide film inhibits the reaction at the interface between the release member and the material to be bonded, the release member can be easily removed from the material to be bonded with a small pulling force after diffusion bonding. Further, since the Si oxide film hinders the permeation of the components contained in the release member into the inside of the material to be bonded, the good heat resistance and corrosion resistance of the material to be bonded are maintained, and the surface texture is smooth. Is maintained. If the Si content is less than 1.5% by mass, the above-mentioned effect of forming the oxide film cannot be sufficiently obtained. Even if it is added in an amount of more than 5.0% by mass, the above effect is almost saturated, but an appropriate processability cannot be obtained due to curing. Therefore, it may be contained in an amount of 5.0% by mass or less.

Mn is an element that improves high temperature oxidation characteristics. If it is contained in an excessive amount, it is work-hardened and the workability is lowered. Therefore, the Mn content is preferably 2.5% by mass or less.

Cr is an element that forms a passivation film and imparts corrosion resistance, and brings about an improvement in corrosion resistance. If it is less than 13.0% by mass, the effect is not sufficient. If it exceeds 23.0% by mass, the workability is lowered. Therefore, the Cr content is preferably 13.0 to 23.0% by mass.

Ni is an essential element for stabilizing the austenite phase and maintaining corrosion resistance, and is also effective for processability. If it is less than 8.0% by mass, these effects are not sufficient, and if it exceeds 15.0% by mass, the effects are saturated and the cost is high. Therefore, the Ni content is 8.0 to 15. 0% by mass is preferable.

P and S are mixed as unavoidable impurities. The lower the content, the more desirable, and the P content is preferably 0.06% by mass or less and the S content is preferably 0.02% by mass or less, respectively, as long as the processability and material properties are not adversely affected.

N is effective as an austenite stabilizing element, and together with Cr and Ni, improves the high temperature strength and corrosion resistance of stainless steel. On the other hand, if it is added in an excessive amount, the manufacturability is lowered, so that the N content is preferably 0.2% by mass or less.

Mo and Cu are elements that contribute to the improvement of high temperature strength and corrosion resistance. The Mo content and Cu content are both preferably 0.02% by mass or more. On the other hand, if Mo is contained in an excessive amount, a ferrite phase may be formed and the processability may be deteriorated. Therefore, the Mo content is preferably 3.0% by mass or less. If the Cu content is excessive, it causes a decrease in hot workability. Therefore, the Cu content is preferably 4.0% by mass or less.

Nb, Ti, and V are effective in improving 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 each element is contained in an excessive amount, the processability is deteriorated. Therefore, 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 V content. Is preferably 1.0% by mass or less.

B is an element that improves hot workability. The B content is preferably 0.0002% by mass or more. On the other hand, if it is added in an excessive amount, boride is precipitated and the processability is deteriorated. Therefore, the B content is preferably 0.02% by mass or less.

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

Al, REM (rare earth element), Y, Ca, and Mg are effective in improving high temperature oxidation resistance, and one or more selected from these elements may be added. The Al content is preferably 0.001% by mass or more, the REM content is preferably 0.001% by mass or more, the Y content is preferably 0.0002% by mass or more, and the Ca content is 0.0002. The mass% or more is preferable, and the Mg content is preferably 0.0002 mass% or more. However, if each element is excessively contained, the processability is deteriorated. Therefore, the Al content is preferably 0.2% by mass or less, the REM content is preferably 0.2% by mass or less, and the Y content is , 0.2% by mass or less, Ca content is preferably 0.1% by mass or less, and Mg content is preferably 0.1% by mass or less.

The shape of the release member is appropriately selected according to the shape of the material to be joined. Since the plate material of the plate heat exchanger is generally plate-shaped, the mold release member arranged in contact with the plate material is used as a mold release plate. The plate thickness is preferably 2 to 10 mm, more preferably 3 to 8 mm.

(High temperature intensity ratio)
Further, in the present embodiment, 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. is 0.9 or more. It is preferable to perform diffusion bonding using a combination of the material and the release member.

Since the release member is sandwiched between the material to be joined and the pushing jig at the time of diffusion joining and exposed to high pressure and high temperature, deformation may occur if the high temperature strength of the release member is low. When the release member is deformed, the uniformity of pressure applied to the material to be joined with which the release member is in contact is impaired, which may lead to defective joints. Therefore, in this embodiment, the high temperature characteristics of the release member were examined based on the high temperature strength at 1000 ° C., which is used as the standard treatment temperature at the time of diffusion bonding.

Specifically, the evaluation was made based on the ratio (Fr / Fp) of the high temperature strength (Fr) of the release member at 1000 ° C. and the high temperature strength (Fp) of the material to be joined at 1000 ° C. As the mold release member, it is preferable to use a steel material having a high temperature strength ratio (Fr / Fp) of 0.9 or more at 1000 ° C. If the high temperature strength of the release member is less than 0.9 with respect to the high temperature strength of the material to be joined, the release member may be excessively deformed by the pressure applied by the presser jig. Due to the deformation of the release member, the pressure state on the material to be joined becomes non-uniform, which may lead to the deformation of the material to be joined. Therefore, from the viewpoint of suppressing deformation, it is preferable to use a combination of the mold release member having the high temperature strength ratio of 0.9 or more and the material to be joined, and more preferably 1.0 or more.

(Coefficient of thermal expansion ratio)
The ratio (Tr / Tp) of the coefficient of thermal expansion (Tr) of the release member and the coefficient of thermal expansion (Tp) of the release member at 30 ° C to 1000 ° C is 0.90 to 1 for the material to be joined and the release member. It is preferable to use a combination of .60. Both the material to be joined and the release member undergo elastic deformation when thermally expanded during heating. If there is a difference in thermal expansion between both members, the strains are accumulated by restraining each other's deformation, which may lead to plastic deformation depending on the degree of strain.

In particular, the material to be joined that forms the heat medium flow path (hollow portion) in the heat exchanger has a portion that can be a non-bonded surface on the opposite side even if it is in contact with the release member on one side. .. Where the joint surfaces of the materials to be joined overlap, they are restrained from the surroundings, whereas the hollow portion as described above is not restrained from the surroundings, so that elastic deformation occurs due to thermal expansion (FIG. 3 (FIG. 3). B)). If the degree of this elastic deformation is excessive, it may lead to plastic deformation and it may be difficult to restore the shape.

When a mold release member with a small high-temperature strength ratio is used, the deformation resistance of the mold release member is lower than that of the plate material, so that the thermal expansion coefficients of both the material to be joined and the mold release member should be about the same. preferable. In the present embodiment, this thermal characteristic can be evaluated based on the ratio (Tr / Tp) of the coefficient of thermal expansion (Tr) of the release member and the coefficient of thermal expansion (Tp) of the material to be joined. When a mold release member having a small high temperature strength ratio is used, the coefficient of thermal expansion ratio (Tp / Tr) is in the range of ± 5% centered on 1.0, that is, 0.95 to 1.05. good.

(Average cooling rate)
The average cooling rate after heating in the diffusion junction is preferably less than 1.2 ° C./min. While the material to be joined and the release member thermally expand during diffusion bonding, they undergo thermal contraction during the cooling process after diffusion bonding and are restored to their original shape. If there is a difference in thermal expansion between the material to be joined and the release member, both members restrain each other's shrinkage changes during cooling, and strain is accumulated. If this shrinkage change becomes excessively large, it may lead to plastic deformation. Therefore, in this embodiment, attention is paid to the average cooling rate after the diffusion bonding is completed. Treatment at an average cooling rate of less than 1.2 ° C./min can suppress the amount of deformation remaining after cooling. If the cooling rate is higher than that, the change in heat shrinkage becomes large and the amount of deformation remaining after cooling becomes large, which is not preferable. The above average cooling rate may be controlled in the temperature range from the holding temperature at the time of diffusion bonding to about 400 ° C.

(Presser jig)
The presser jig is a member that is connected to the pressurizing mechanism of the pressurizing device and transmits the pressing force to the material to be joined. It is preferable to use a carbon material for the presser jig because it is required to have heat resistance at the temperature at the time of diffusion bonding and not to be damaged.

(Release agent)
In the present invention, it is preferable to apply a mold release agent to both surfaces of the mold release member. For example, a 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.

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.

(Preparation of test material)
Steel material No. consisting of the balance Fe having the component composition shown in Table 1 and unavoidable impurities. 1-Steel material No. 9 was melted by 30 kg of vacuum melting, and the obtained ingot was forged into a plate having 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 finish 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. The steel materials 5 and 6 used for the plate were further cold-rolled and annealed to make the final finished plate thickness 0.4 mm and 1.0 mm, and the surface finishing treatment was performed by 2B or 2D finishing, and then cold-rolled. Obtained 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. These test materials were subjected to a test relating to the material to be joined or the release member.

Steel material No. 1-Steel material No. Reference numeral 5 is an austenitic stainless steel. Steel material No. 6-Steel material No. Reference numeral 9 is a ferrite-based stainless steel.

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

(Measurement of coefficient of thermal expansion)
Using the obtained test material, the temperature rise rate is 1 ° C / sec using a differential expansion analyzer (manufactured by Rigaku Co., Ltd., infrared heating type thermal expansion measuring device (TMA), standard sample: quartz) in accordance with JIS Z 2285. It was heated to 30 ° C. to 1000 ° C. The amount of expansion of the test piece at that time was measured and calculated as a coefficient of thermal expansion (α30-1000 ° C.) at 30 ° C. to 1000 ° C. The measurement results are shown in Table 1 (unit: × ^10-6 / ° C).

(Joining test)
A test assembly was prepared by combining four test materials of the material to be joined (plate material) and one test material of the mold release member (release plate). As shown in Table 2, in this test, the steel material No. 1 was used as the plate material. Four test materials consisting of 5 were used. A test material of two plate materials (thickness 1.0 mm / sheet) having an opening that serves as a flow path was used, and the release member was made of steel No. 1 to No. Two plate materials (thickness 0.4 mm / sheet) as a heat transfer plate having no above-mentioned opening are formed by stacking test materials having a thickness of 3.0 mm and sandwiching the two plate materials. Placed. A carbon jig was used as the presser jig. Hexagonal boron nitride powder (boron spray manufactured by YK Inoas Co., Ltd.) was applied to both sides of the mold release member as a mold release agent. The above test assembly was subjected to diffusion bonding treatment under the following pressure and heating conditions by a hot press device.

・ Atmosphere: Initial vacuum degree is 1 × 10 ^-2 Pa or less ・ Bonding temperature: 1080 ℃
・ Temperature rise time: Approximately 2 hours from room temperature to joining temperature ・ Soaking time (joining) time: 3 hours ・ Average cooling rate: From 1080 ° C to 400 ° C, 3.2 ° C / min (A pattern), or 1. 1 ° C / min (B pattern)
・ Pressurization: Surface pressure 2MPa

FIG. 2 shows the heating and cooling patterns applied to the diffusion bonding treatment. The A pattern and the B pattern in FIG. 2 show the above two patterns in which the average cooling rate is changed. After cooling to room temperature, the test assembly was taken out from the hot press device and the following evaluation tests were conducted for deformation suppression and releasability.

(Evaluation of deformation suppression)
Deformation suppression was evaluated based on the amount of deformation of the diffusion-bonded plate material. A method for measuring the amount of deformation will be described. FIG. 3 is a schematic view showing a cross section of the test assembly. FIG. 3A shows a state before diffusion bonding, in which a test assembly 14 in which four plate materials 11a to 11d and two release plates 13 are combined is mounted on a carbon presser jig 15. It shows a form in which pressure is applied while sandwiched. FIG. 3B shows the state of the test assembly 14 after diffusion bonding. The plate materials 11a and 11d facing the cavity 16 side in the test assembly 14 after diffusion bonding are restrained by the release plate 3 and the other plate materials 11b and 11c except for the cavity side, so that they expand during heating. Then, it deforms so as to bend toward the cavity side. If the shape is not restored by the shrinkage change during cooling, it remains as a bent shape. The height 17 of the highest deformed portion was measured with reference to the surfaces of the plate materials 11a and 11d in contact with the release plate 3, and the maximum value was obtained. In the present specification, this numerical value is referred to as a deformation amount of the plate material. Based on this amount of deformation, the deformation state after diffusion bonding was evaluated. The height 17 was measured using a high-speed three-dimensional shape system manufactured by Combs. From the viewpoint of deformation suppression, when the amount of deformation was less than 30 μm, it was evaluated as good (⊚), when it was 30 μm to 50 μm, it was evaluated as appropriate (◯), and when it was more than 50 μm, it was evaluated as unsuitable (×).

(Evaluation of releasability)
Using the test assembly, a peeling test was conducted between the plate material and the mold release plate in order to evaluate the mold release property after joining. The outline is shown in FIG. A tensioning device (not shown) and two jigs with suction cups 25 attached to the ends of the wires 26 were prepared. The suction cups 25 of the jig were attached to the surfaces of the two mold release plates 23 in the test assembly 24 after diffusion bonding. After connecting the weight 27 of a predetermined weight to the wire 26 of one jig, the wire 26 of the other jig was pulled up by a pulling device. By pulling both sides of the test assembly 24 with the weight of the weight 27, it was visually observed whether or not the plate material 21 and the release plate 23 were peeled off, and the presence or absence of the peeling was confirmed. The test was repeated in the same procedure with the weight of the weight 27 changed. Regarding the evaluation criteria, it is desirable that the plate material and the mold release plate after diffusion bonding can be removed with a small force, so if the plate material and the mold release plate are peeled off with a weight weight of 5 kg or less, the mold release property Good (○), when the plate material and the mold release plate are peeled off with a weight weight of 20 kg or less, the releasability is slightly insufficient (△), and the plate material and the mold release plate with a weight weight of 20 kg or more. When and did not peel off, it was determined that the releasability was poor (x).

(Test results)
In this test, the steel material No. Plate material made of austenitic stainless steel of No. 5 and steel material No. For the plate material made of ferritic stainless steel of No. 6, the steel material No. 1 to No. Using 18 kinds of test assemblies in which mold release plates made of each of 9 stainless steels were combined, tests on high temperature strength, coefficient of thermal expansion, deformation suppression, and mold release property were conducted. The test results are shown in Table 2. Deformation suppression and releasability were tested using three test assemblies for each of the two heating and cooling patterns. Deformation suppression was evaluated by the average value of the three deformation amounts. The releasability was evaluated by averaging the three results.

In Examples 1 to 6 of the present invention, the release plates are each made of steel material No. 1 to No. This is an example of diffusion bonding in a test assembly composed of 3. The amount of deformation after diffusion bonding was good (⊚) or appropriate (◯) and was in the range of 50 μm or less, and a diffusion bonding product in which deformation was suppressed was obtained. When the combination of the material to be joined and the release plate corresponding to the present invention is used, it is presumed that the deformation is suppressed because the thermal expansion and contraction due to heating and cooling during the diffusion bonding treatment proceeds appropriately.

Regarding the releasability of Examples 1 to 6 of the present invention, the plate material and the releasable plate were peeled off with a small tensile force. By using the combination of the material to be bonded and the release plate corresponding to the present invention, the release plate could be easily removed from the material to be bonded after diffusion bonding. It is presumed that the Si oxide film formed on the surface of the mold release plate inhibits the interfacial reaction between the material to be bonded and the mold release plate, suppresses the adhesion between the two members, and improves the mold release property.

Further, looking at the results of the average cooling rate after diffusion bonding at 3.2 ° C./min (A pattern) and 1.1 ° C./min (B pattern) in Examples 1 to 6 of the present invention, the average cooling rate. The test assembly cooled by the small B pattern had improved deformation suppression as compared with the test assembly by the A pattern. It is presumed that when the cooling rate is low, the degree of change in heat shrinkage is relaxed, so that strain accumulation is reduced and deformation is suppressed.

On the other hand, in Comparative Examples 1 to 12, the steel material No. 4-No. A mold release plate composed of 9 is used. In Comparative Examples 1 to 12, the Si content of the steel material of the release plate is less than 1.5% by mass, which is outside the scope of the present invention. In both cases, the releasability was slightly insufficient (Δ) or unsuitable (×), and it was difficult to remove the mold after diffusion bonding.

Further, in Comparative Examples 3 to 6, 10 and 12, since the high temperature intensity ratio was less than 0.9, the deformation after diffusion bonding was large, and it was unsuitable (x) for suppressing the deformation after diffusion bonding.

According to the above test results, the stainless steel material having the specified composition of the present invention suppresses the deformation of the material to be bonded while maintaining the diffusion bonding property of the material to be bonded, resulting in releasability after the diffusion bonding treatment. It was confirmed that it is possible to provide an excellent diffusion joining jig, and that it is particularly suitable for a mold release member.

1 Plate material (material to be joined)
2 Plate laminated body 3 Release member 4 Presser jig 5 Pressurized shaft 11a, 11b, 11c, 11d Plate material 13 Release plate 14 Test assembly 15 Presser jig 16 Cavity 17 Height (deformation amount)
21 Plate material 23 Release plate 24 Test assembly 25 Sucker 26 Wire 27 Weight

Claims (3)

A stainless steel material containing 1.5% by mass or more of Si, and the ratio of the high temperature strength (Fr) of the stainless steel material at 1000 ° C. to the high temperature strength (Fp) of the material to be joined by diffusion bonding at 1000 ° C. (Fr / Fp) is 0.9 or more,
The stainless steel material has C: 0.1% by mass or less, Si: 1.5 to 5.0% by mass (excluding 1.5 to 2.0% by mass) , Mn: 2.5% by mass or less, P: 0.06% by mass or less, S: 0.02% by mass or less, Ni: 8.0 to 15.0% by mass, Cr: 13.0 to 23.0% by mass, N: 0.2% by mass or less A mold release member made of a stainless steel material for a diffusion joining jig, which comprises, and has a composition in which the balance is composed of Fe and unavoidable impurities. Further, the stainless steel material has Mo: 3.0% by mass or less, Cu: 4.0% by mass or less, Nb: 0.8% by mass or less, Ti: 0.5% by mass or less, V: 1.0% by mass. The mold release member according to claim 1, further comprising one or more selected from B: 0.02% by mass or less. Further, the stainless steel material has Al: 0.2% by mass or less, REM: 0.2% by mass or less, Y: 0.2% by mass or less, Ca: 0.1% by mass or less, Mg: 0.1% by mass. The release member according to claim 1 or 2, which comprises one or more selected from the following.

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