Detection tool and detection method for diffusion welding plate heat exchanger core

Abstract

The invention relates to an inspection tool for a diffusion welding plate heat exchanger core, which comprises a heat exchange core simulation piece and two stretching transition plates, the heat exchange core simulation piece has a structure consistent with that of the diffusion welding plate heat exchanger core, and the two stretching transition plates are respectively assembled on two opposite sides of the heat exchange core simulation piece. The threaded holes in the two stretching transition plates are in one-to-one correspondence in position and are coaxial, and the threaded holes are matched with the studs so that the load of the stretching testing machine can be perpendicularly transmitted to the diffusion welding seam of the heat exchange core simulation piece through the studs. The invention further relates to an inspection method of the diffusion welding plate heat exchanger core. According to the inspection tool and the inspection method for the diffusion welding plate type heat exchanger core, the problem that the welding quality of the diffusion welding plate type heat exchanger core cannot be evaluated through a nondestructive inspection method is solved, the tensile test result can truly reflect the performance of a product connector according to the heat exchange core structure of a diffusion welding heat exchanger product, and the inspection accuracy is improved. And the diffusion welding quality of the heat exchange core can be effectively evaluated.

Description

Technical Field

[0001] This invention relates to the manufacture of diffusion welded plate heat exchangers, and more specifically to an inspection fixture and inspection method for the core of a diffusion welded plate heat exchanger. Background Technology

[0002] A diffusion-welded plate heat exchanger is a compact plate heat exchanger whose heat exchange core is composed of multiple plates with flow channels connected by diffusion welding, such as... Figure 1 As shown.

[0003] Diffusion welding is a solid-state metal joining process. Under certain temperature and pressure, the surfaces to be joined come into contact with each other. By causing local microscopic plastic deformation or generating a microscopic liquid phase on the surfaces to be joined, the contact between the surfaces is expanded. After a certain period of time, the atoms in the bonding layer diffuse with each other, achieving a reliable overall connection.

[0004] Since diffusion welding is a surface contact connection, there is currently a lack of reliable non-destructive testing methods for this type of welding. In particular, for plate heat exchanger products completed using diffusion welding, due to structural limitations, it is impossible to effectively test the actual weld bonding condition in a non-destructive manner.

[0005] In existing technologies, the industry generally uses channelless flat plate specimens for diffusion welding quality assessment, and uses this to determine whether the welding process of the actual product is qualified. Metallographic examination is performed by observing the microstructure of the specimen under a microscope to evaluate the quality of the welded joint; tensile tests are conducted to determine the breaking load, and the mechanical properties are verified by comparing it with the theoretical load-bearing capacity of the joint.

[0006] In the production practice of diffusion-welded plate heat exchangers, although the diffusion weld quality test results using flat plate specimens are qualified, weld cracking failures still occur in the core of the actual product during use. This phenomenon indicates that there is a discrepancy between the existing testing method based on flat plate specimens and the actual performance of the product, and it cannot effectively reflect the actual weld quality of the flow channel plates. Summary of the Invention

[0007] To address the issue of discrepancies between existing test results and the actual performance of products, this invention proposes an inspection fixture and method for the core of a diffusion-welded plate heat exchanger.

[0008] This invention provides an inspection fixture for a diffusion-welded plate heat exchanger core, comprising a heat exchanger core simulator and two tensile transition plates. The heat exchanger core simulator has the same structure as the diffusion-welded plate heat exchanger core. The two tensile transition plates are respectively assembled on opposite sides of the heat exchanger core simulator. The threaded holes on the two tensile transition plates are one-to-one corresponding and coaxial. The threaded holes cooperate with studs to allow the load of the tensile testing machine to be vertically transmitted to the diffusion weld of the heat exchanger core simulator through the studs.

[0009] In a preferred embodiment, the heat exchange core body simulation member is formed by stacking a first flat heat exchange plate, an etched plate heat exchange plate, a corrugated plate heat exchange plate, and a second flat heat exchange plate. The first flat heat exchange plate and the etched plate heat exchange plate are connected by a diffusion weld. The etched plate heat exchange plate and the corrugated plate heat exchange plate are connected by a diffusion weld. The corrugated plate heat exchange plate and the second flat heat exchange plate are connected by a diffusion weld. A first heat exchange flow channel is formed between the first flat heat exchange plate and the etched plate heat exchange plate. Second heat exchange flow channels are formed on both sides of the corrugated plate heat exchange plate between the etched plate heat exchange plate and the second flat heat exchange plate. The diffusion welds are divided by the heat exchange flow channels to form discontinuous contact surfaces.

[0010] In a preferred embodiment, the heat exchange core body simulation member and the stretching transition plate are connected by a diffusion weld.

[0011] The present invention also relates to a method for inspecting a diffusion-welded plate heat exchanger core body, which includes the following steps: S1, providing a heat exchange core body simulation member having the same structure as the diffusion-welded plate heat exchanger core body; S2, providing two stretching transition plates, each of which is provided with three threaded holes; S3, respectively fixedly assembling the stretching transition plates on opposite sides of the heat exchange core body simulation member, and the positions of the threaded holes on the two stretching transition plates correspond to each other and are coaxial; S4, cutting three tensile specimens in the central area and the area near the edge of the heat exchange core body simulation member, and the center of each tensile specimen corresponds to the threaded hole; S5, screwing studs into the threaded holes of the cut tensile specimens to connect the tensile specimens with a tensile testing machine, and performing tensile tests to measure the breaking load.

[0012] In a preferred embodiment, the two stretching transition plates have the same thickness and size, and the specifications and positions of the threaded holes are the same.

[0013] In a preferred embodiment, the central axis of the threaded hole coincides with the stress axis of the diffusion weld of the heat exchange core body simulation member.

[0014] In a preferred embodiment, in step S3, the heat exchange core body simulation member and the stretching transition plate are connected by a diffusion weld.

[0015] In a preferred embodiment, in step S4, three tensile specimens are cut.

[0016] In a preferred embodiment, the three tensile specimens are evenly spaced along the diagonal.

[0017] In a preferred embodiment, it is qualified if the actual breaking force of each tensile specimen is greater than the theoretical bearing capacity.

[0018] The inspection fixture and method for the diffusion-welded plate heat exchanger core of the present invention solves the problem that the welding quality of the diffusion-welded plate heat exchanger core cannot be evaluated by non-destructive testing methods. The inspection method adopted is for the heat exchanger core structure of the diffusion-welded heat exchanger product and can perform tensile tests on the heat exchanger core simulation part after diffusion welding. This heat exchanger core simulation part has the same structure as the product, and the tensile test results can truly reflect the performance of the product joint and can effectively evaluate the quality of diffusion welding of the heat exchanger core. Attached Figure Description

[0019] Figure 1 This is a physical structural diagram of the heat exchange core of the diffusion welded plate heat exchanger according to the present invention.

[0020] Figure 2 for Figure 1 A partially enlarged schematic diagram of the heat exchange channel cross-section of the diffusion welded plate heat exchanger core.

[0021] Figure 3 The schematic diagram of the inspection fixture according to the present invention shows the assembly relationship between the heat exchange core simulation component and the tension transition plate.

[0022] Figure 4 for Figure 3 The top view of the inspection fixture shows the cutting positions of the three tensile specimens (corresponding to the threaded hole positions).

[0023] Figure 5 This is a schematic diagram showing the state of one of the tensile specimens after it has been cut out and assembled with a stud. Detailed Implementation

[0024] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0025] To investigate the root cause of the ineffectiveness of existing inspection methods in reflecting actual weld quality, the inventors focused on the specific structure of the core of a diffusion-welded plate heat exchanger. For example... Figure 2As shown, the core of the diffusion-welded plate heat exchanger is composed of multiple layers of plates with flow channels stacked together. From top to bottom, it includes a first flat heat exchange plate 1, an etched heat exchange plate 2, a corrugated heat exchange plate 3, and a second flat heat exchange plate 4. The first flat heat exchange plate 1 and the etched heat exchange plate 2 are connected by a diffusion weld 5. Similarly, the etched heat exchange plate 2 and the corrugated heat exchange plate 3 are connected by a diffusion weld 5, and the corrugated heat exchange plate 3 and the second flat heat exchange plate 4 are connected by a diffusion weld 5. A first heat exchange channel 6 is formed between the first flat heat exchange plate 1 and the etched heat exchange plate 2. A second heat exchange channel 7 is formed between the etched heat exchange plate 2 and the second flat heat exchange plate 4 on both sides of the corrugated heat exchange plate 3. Due to the alternating distribution of the first heat exchange channel 6 and the second heat exchange channel 7, the diffusion weld 5 is divided into multiple independent small faces by the heat exchange channels 6 and 7, forming a typical discontinuous contact surface.

[0026] In contrast, the flat plate specimens used for testing in the prior art are welded together from two flat plates without flow channels, and their contact surface is a continuous and uninterrupted plane, i.e., a parallel continuous contact surface.

[0027] Through in-depth analysis of the structure, the inventors discovered that due to the influence of processing and assembly errors, the discontinuous contact surfaces of the actual product cannot actually be completely guaranteed to be on the same plane. There is a significant structural difference between the discontinuous contact surfaces and the continuous contact surfaces of the flat plate specimens. This affects the diffusion welding effect and directly affects the welding rate. Consequently, the test results of the flat plate specimens cannot reflect the weld quality of the actual product. This problem has become a long-standing technical bottleneck in the field.

[0028] The core of this invention lies in constructing a discontinuous contact surface weld that is completely identical to the actual product, and using this as the tensile load section during inspection. For example... Figure 3 As shown, the inspection fixture for the diffusion-welded plate heat exchanger core according to the present invention includes a heat exchanger core simulation component 10 and a stretching transition plate 20. The heat exchanger core simulation component 10 has the same structural features as the actual product of the diffusion-welded plate heat exchanger core, specifically including flat heat exchange plates 1 and 4, etched heat exchange plates 2, and corrugated heat exchange plates 3, which are identical to those in the actual product. Each plate 1-4 is connected by a diffusion weld 5 to form heat exchange channels 6 and 7, accurately replicating the channel structure and weld morphology of the actual product. Two stretching transition plates 20 are respectively assembled on the upper and lower sides of the heat exchanger core simulation component 10. Each stretching transition plate 20 is machined with vertically aligned threaded holes 21. The two stretching transition plates 20 have the same thickness and dimensions, and the specifications and positions of the threaded holes 21 are identical.

[0029] The inspection method for the core of a diffusion-welded plate heat exchanger according to the present invention first includes fabricating a heat exchange core simulation part 10. Using the same plates and processing technology as the actual product, a heat exchange core simulation part 10 with a structure completely identical to the actual product is fabricated.

[0030] The inspection method for the diffusion welded plate heat exchanger core according to the present invention further includes providing a tensile transition plate 20. Threaded holes 21 are provided on the tensile transition plate 20 to ensure that the tensile load acts perpendicularly on the discontinuous interface. In a preferred embodiment, the number of threaded holes 21 is three. The central axis of the threaded holes 21 coincides with the force axis of the diffusion weld 5 in the heat exchanger core simulation 10.

[0031] The inspection method for the core of the diffusion-welded plate heat exchanger according to the present invention further includes diffusion welding the tensile transition plate 20 to the heat exchange core simulation part 10 as a whole, so that the weld parameters (temperature, pressure, time) of the tensile transition plate 20 and the heat exchange core simulation part 10 are completely consistent with the product, ensuring the authenticity of the test environment.

[0032] The inspection method for the core of a diffusion-welded plate heat exchanger according to the present invention further includes targeted sampling. For example... Figure 4 As shown, three tensile specimens 22 are taken from the central area and near the edge area of ​​the heat exchange core simulation component 10, with the center of each tensile specimen 22 corresponding to a threaded hole 21. In a preferred embodiment, the threaded holes 21 are machined at three positions: the center and the edge of each tensile transition plate 20, and the corresponding tensile specimens 22 are evenly spaced along the diagonal, thus ensuring good representativeness of the sampling. The specifications of the threaded holes 21 are determined by calculating the load based on the size of the cut tensile specimens 22, and the thickness of the tensile transition plate 20 is also selected based on the calculated load to avoid deformation affecting the detection accuracy.

[0033] The inspection method for the diffusion-welded plate heat exchanger core according to the present invention finally includes a precise tensile test. This is achieved by screwing studs 30 into the threaded holes 21 on both the upper and lower sides of the cut tensile specimen 22, such as... Figure 5 As shown, stud 30 connects the tensile specimen 22 to the tensile testing machine for tensile testing to determine the breaking load. The result is compared with the theoretical value of the joint to determine whether the quality is qualified. The theoretical bearing capacity of the joint is determined by the total area of ​​the diffused weld on the cut tensile specimen and the theoretical tensile strength of the material. If the actual breaking force measured in the test is greater than the theoretical bearing capacity, the joint is considered qualified.

[0034] Three tensile specimens 22 (one center tensile specimen and two edge tensile specimens) were cut and subjected to tensile tests to determine the breaking load of each tensile specimen 22. The actual breaking load of all tensile specimens 22 must be greater than 90% of the theoretical bearing capacity of their corresponding joints to be considered as qualified for diffusion welding of the heat exchange core; if one or more tensile specimens do not meet this requirement, the specimens are considered as unqualified.

[0035] In summary, this invention is the first to propose the non-equivalence of the performance of diffusion welds formed by discontinuous contact surfaces in actual products and diffusion welds formed by continuous contact surfaces in flat plate specimens. Furthermore, by using a heat exchange core simulation component 10 with the same structure as the product, and through special tooling, the complex welds can be directly inspected, providing a quantifiable evaluation standard for the quality control of diffusion welded plate heat exchangers.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent changes and modifications made in accordance with the claims and description of the present invention fall within the scope of protection of the present invention. Contents not described in detail in this invention are conventional techniques.

Claims

1. A tooling for inspecting the core of a diffusion-welded plate heat exchanger, characterized in that, The inspection fixture includes a heat exchange core simulation part (10) and two tensile transition plates (20). The heat exchange core simulation part (10) has the same structure as the core of the diffusion welded plate heat exchanger. The two tensile transition plates (20) are respectively assembled on opposite sides of the heat exchange core simulation part (10). The threaded holes (21) on the two tensile transition plates (20) are in one-to-one correspondence and coaxial. The threaded holes (21) are engaged with the studs (30) so that the load of the tensile testing machine is vertically transmitted to the diffusion weld (5) of the heat exchange core simulation part (10) through the studs (30).

2. The inspection fixture according to claim 1, characterized in that, The heat exchange core simulation component (10) is composed of a first flat heat exchange plate (1), an etched heat exchange plate (2), a corrugated heat exchange plate (3) and a second flat heat exchange plate stacked together. The first flat heat exchange plate (1) and the etched heat exchange plate (2) are connected by a diffusion weld (5). The etched heat exchange plate (2) and the corrugated heat exchange plate (3) are connected by a diffusion weld (5). The corrugated heat exchange plate (3) and the second flat heat exchange plate are connected by a diffusion weld (5). A first heat exchange channel (6) is formed between the first flat heat exchange plate (1) and the etched heat exchange plate (2). A second heat exchange channel (7) is formed between the etched heat exchange plate (2) and the second flat heat exchange plate on both sides of the corrugated heat exchange plate (3). The diffusion weld (5) is divided by the heat exchange channels (6, 7) to form a discontinuous contact surface.

3. The inspection fixture according to claim 2, characterized in that, The heat exchange core simulation component (10) and the tensile transition plate (20) are connected by a diffusion weld (5).

4. A method for inspecting the core of a diffusion-welded plate heat exchanger, characterized in that, The testing method includes the following steps: S1, provides a heat exchange core simulation component (10) having a structure consistent with that of a diffusion welded plate heat exchanger core; S2 provides two stretching transition plates (20), each having three threaded holes (21). S3, the stretching transition plates (20) are fixedly assembled on the opposite sides of the heat exchange core simulation part (10), and the threaded holes (21) on the two stretching transition plates (20) are in one-to-one correspondence and coaxial. S4, three tensile specimens (22) are cut from the central area and near the edge area of ​​the heat exchange core simulation part (10), and the center of each tensile specimen (22) corresponds to the threaded hole (21). S5, screw a stud (30) into the threaded hole (21) of the cut tensile specimen (22) to connect the tensile specimen (22) to the tensile testing machine and perform tensile testing to determine the breaking load.

5. The testing method according to claim 4, characterized in that, The two stretch transition plates (20) have the same thickness and size, and the threaded holes (21) have the same specifications and positions.

6. The testing method according to claim 4, characterized in that, The central axis of the threaded hole (21) coincides with the stress axis of the diffusion weld (5) of the heat exchange core simulation part (10).

7. The testing method according to claim 6, characterized in that, In step S3, the heat exchange core simulation component (10) and the stretch transition plate (20) are connected by a diffusion weld (5).

8. The testing method according to claim 4, characterized in that, In step S4, three tensile specimens (22) are cut.

9. The testing method according to claim 8, characterized in that, Three tensile specimens (22) are set evenly spaced along the diagonal.

10. The testing method according to claim 4, characterized in that, The specimen is considered qualified if the actual breaking force of each tensile specimen (22) is greater than the theoretical bearing capacity.

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