Diffusion welding method based on interface normal solid pressurization

Abstract

The invention discloses a diffusion welding method based on interface normal solid pressurization, which comprises the following steps of: assembling a second metal workpiece to be welded into an inner cavity of a first metal workpiece, and fixing the first metal workpiece; and the external pressure clamp is arranged at the top of the second metal workpiece, the cavity of the second metal workpiece is filled with the discrete solid filler, the internal pressure clamp is arranged in a middle through hole of the external pressure clamp, and under the high-temperature condition, downward pressurization is conducted through the external pressure clamp and the internal pressure clamp, and diffusion welding is conducted. The cavity of the second metal workpiece assembled in the first metal workpiece is filled with the discrete solid filler, the second metal workpiece is axially pressurized through the external pressure clamp, and meanwhile, the discrete solid filler is pressurized through the internal pressure clamp, so that the discrete solid filler pressurizes the second metal workpiece in all directions, and the pressure of the second metal workpiece in all directions is achieved. The second metal workpiece can obtain large and uniform pressure in all directions, and then uniform and stable welding is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of diffusion welding, and in particular to a method for diffusion welding based on an interface method of pressurizing a solid. Background Art

[0002] Solid phase diffusion welding is a welding method in which two workpieces to be welded are pressed together and heated in a vacuum or protective atmosphere to cause microscopic plastic deformation on the tiny unevenness of the welding surface of the two workpieces to be welded, thereby achieving close contact. In the subsequent heating and heat preservation, atoms diffuse with each other to form a metallurgical connection. During the welding process, the two workpieces to be welded are first brought into close contact, and pressure is applied to cause plastic deformation and high-temperature creep on the microscopic protrusions on their surfaces, thereby achieving close contact. On the basis of close contact, the temperature is heated to a certain temperature below the melting point of the parent material and maintained for a period of time. At this time, the atoms between the contact interfaces begin to diffuse with each other. This diffusion process is carried out on a microscopic scale, and a metallurgical connection is formed through the migration and rearrangement of atoms. As the atomic diffusion proceeds, the connection interface gradually expands until the entire interface is metal-bonded. At this point, the two workpieces to be welded have been connected together by solid phase diffusion welding to form a whole.

[0003] There are extensive studies and applications on solid-phase diffusion welding. For example, plunger hydraulic pumps are usually made of two metal composites. The base is generally made of steel, and the part that connects to the plunger is usually made of copper to ensure lubrication and sealing. At present, copper-steel plunger hydraulic pumps are usually connected by diffusion welding technology to ensure the strength of the connection. Patent CN118832276A proposes a kovar alloy and copper composite rod and its hot extrusion processing technology. The workpiece is hot-pressed by a pressure head. Under the action of the hot extrusion pressure head, the copper rod is squeezed into the inner wall of the kovar alloy to form diffusion welding. Patent CN106808078B proposes a diffusion welding method for dissimilar metals. A specially designed outer limit fixture and inner support fixture are used to constrain the thermal expansion of the assembled dissimilar metal parts to be welded during the welding process, so that the welding surface obtains sufficient and uniform welding pressure.

[0004] However, the above two patents realize diffusion welding by combining axial pressure and thermal expansion, which has the following disadvantages: 1. The radial (normal) force generated by axial pressure of solid and thermal expansion is limited, and it is difficult for the interface normal to reach the required interface pressure; 2. It is difficult to achieve effective connection at the right angle position of the root of the blind hole; 3. The processing accuracy of the parts before diffusion welding is required to be very high, and the preparation process is difficult. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a method for diffusion welding based on interface normal solid pressurization, wherein a discrete solid filler is loaded in the cavity of a second metal workpiece assembled in a first metal workpiece, and the second metal workpiece is axially pressurized by an external pressure fixture. At the same time, the discrete solid filler is pressurized by an internal pressure fixture to achieve pressurization of the second metal workpiece in all directions by the discrete solid filler. The second metal workpiece can obtain a large and uniform pressure in all directions, thereby achieving uniform and stable welding.

[0006] In order to solve the above technical problems, the present invention provides a method for diffusion welding by pressurizing a solid based on an interface method, comprising the following steps: S1. Provide a first metal workpiece and a second metal workpiece to be welded, wherein a cavity is provided in the middle of the first metal workpiece and the second metal workpiece; S2, assembling the second metal workpiece into the inner cavity of the first metal workpiece, and fixing the first metal workpiece; Wherein, the outer wall of the to-be-welded area of ​​the second metal workpiece is in contact and connected with the inner wall of the second metal workpiece; S3, placing an external pressure fixture with a through hole in the middle on top of the second metal workpiece, filling the cavity of the second metal workpiece with discrete solid fillers, and placing an internal pressure fixture in the middle through hole of the external pressure fixture; Wherein, the bottom surface of the internal pressure fixture is in contact with the discrete solid filler, and the side surface is in contact with the inner wall of the external pressure fixture; S4. Under high temperature conditions, the first metal workpiece and the second metal workpiece are diffusion welded by applying downward pressure through an external pressure fixture and an internal pressure fixture.

[0007] The present invention fills a discrete solid filler with fluid properties into the cavity of a second metal workpiece assembled in the first metal workpiece, and axially pressurizes the second metal workpiece through an external pressure fixture. At the same time, the discrete solid filler is pressurized by an internal pressure fixture to achieve pressurization of the second metal workpiece in all directions by the discrete solid filler. The second metal workpiece can obtain a large and uniform pressure in all directions, thereby promoting diffusion welding at the interface between the second metal workpiece and the first metal workpiece, and achieving uniform and stable welding; avoiding the problems of low interface pressure only through axial pressurization and weak connection at the right-angle part of the root of the blind hole in the prior art.

[0008] Furthermore, the solidus temperature of the lower solidus of the first metal workpiece and the second metal workpiece is set to T0, then in S4, the temperature T of the high temperature condition is: 0.5 T0< T ≤0.95 T0.

[0009] Furthermore, the yield strength of the first metal workpiece and the second metal workpiece with a lower yield strength is set to F0, then in S4, the downward pressing pressure F is: 0.2 F0< F ≤0.95 F0.

[0010] Furthermore, the particle size of the discrete solid filler is smaller than 1 / 4 of the shortest side length or diameter of the internal cavity of the second metal workpiece. A discrete solid filler of appropriate size can be selected according to the size of the internal cavity of the second metal workpiece, and a discrete solid filler with a small particle size is preferred to improve the uniformity of pressure in all directions and better achieve welding of various parts near the blind hole.

[0011] Furthermore, the filler in the cavity of the second metal workpiece may also be liquid metal.

[0012] Furthermore, the discrete solid filler is selected from one or more of steel balls, ceramic balls, fine sand, and powder.

[0013] Furthermore, the melting point of the discrete solid filler is greater than the temperature during diffusion welding in S4, ensuring that the discrete solid filler does not melt under high temperature and high pressure conditions during diffusion welding and has a certain strength to maintain its own shape.

[0014] Furthermore, the internal cavity of the first metal workpiece is a through hole structure or a blind hole structure. When it is a through hole structure, a rigid support is fixed at the bottom of the first metal workpiece before S2 to form a blind hole structure.

[0015] Furthermore, the connection interface between the first metal workpiece and the second metal workpiece can be a regular shape such as a circle, square, pentagon, hexagon, etc. with consistent cross-sections at the top and bottom, or an irregular shape such as a vase with inconsistent cross-sections at the top and bottom; when the interface is an irregular shape, the first metal workpiece can be split and then wrapped and assembled on the outside of the second metal workpiece.

[0016] Furthermore, before S2, a step of processing the first metal workpiece and the second metal workpiece is also included, and after processing, the surface roughness of the first metal workpiece and the second metal workpiece Ra≤0.8.

[0017] Furthermore, the processing step also includes a cleaning step for removing surface impurities.

[0018] Furthermore, after S4, it also includes removing the internal pressure fixture, the external pressure fixture and the discrete solid filler, as well as a finishing step.

[0019] Beneficial effects of the present invention: The present invention fills a discrete solid filler with fluid properties into the cavity of a second metal workpiece assembled in a first metal workpiece, axially pressurizes the second metal workpiece through an external pressure fixture, and at the same time, pressurizes the discrete solid filler through an internal pressure fixture, thereby achieving uniform pressurization of the second metal workpiece in all directions by the discrete solid filler.

[0020] The second metal workpiece of the present invention can obtain a relatively large and uniform normal pressure, thereby promoting diffusion welding at the interface between the second metal workpiece and the first metal workpiece, and achieving uniform and stable welding.

[0021] The present invention can realize uniform pressurization of the area near the blind hole by using fillers with small particle sizes, thereby avoiding the problems of low interface pressure and weak connection at the right-angle area at the root of the blind hole in the prior art only by axial pressurization. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a flow chart of the method for diffusion welding based on pressurizing solid by interface method of the present invention; Figure 2 It is a schematic structural diagram of diffusion welding based on pressurizing solid by interface method of the present invention; Explanation of the numbers in the figure: 1. first metal workpiece, 2. second metal workpiece, 3. external pressure fixture, 4. discrete solid filler, 5. internal pressure fixture. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be described clearly and completely below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Reference Figure 1 As shown, this embodiment provides a method for diffusion welding based on the interface normal solid pressurization, including the following steps: S1, providing a first metal workpiece 1 and a second metal workpiece 2 to be welded, wherein a cavity is provided in the middle of the first metal workpiece 1 and the second metal workpiece 2; S2. Reference Figure 2As shown, the second metal workpiece 2 is assembled into the inner cavity of the first metal workpiece 1, and the first metal workpiece 1 is fixed; wherein the outer wall of the second metal workpiece 2 in the area to be welded is in contact and connected with the inner wall of the second metal workpiece 2; S3, placing an external pressure fixture 3 with a through hole in the middle on top of the second metal workpiece 2, filling the cavity of the second metal workpiece 2 with a discrete solid filler 4, and placing an internal pressure fixture 5 in the middle through hole of the external pressure fixture 3; wherein the bottom surface of the internal pressure fixture 5 is in contact with and connected to the discrete solid filler 4, and the side surface is in contact with and connected to the inner wall of the external pressure fixture 3; S4. Under high temperature conditions, the first metal workpiece 1 and the second metal workpiece 2 are diffusion welded by applying downward pressure through the external pressure fixture 3 and the internal pressure fixture 5.

[0026] Specifically, the solidus temperature of the lower solidus of the first metal workpiece 1 and the second metal workpiece 2 is set to T0. Then in S4, the temperature T of the high temperature condition is: 0.5 T0< T ≤0.95 T0, for example, T can be 0.6T0, 0.65T0, 0.7T0, 0.75T0, 0.8T0, 0.85T0, 0.9T0, 0.95T0, etc.

[0027] Specifically, the yield strength of the first metal workpiece 1 and the second metal workpiece 2 with a lower yield strength is set to F0. Then in S4, the downward pressure F is: 0.2 F0< F ≤0.95 F0. For example, F can be 0.2 F0, 0.3 F0, 0.4 F0, 0.5 F0, 0.6 F0, 0.7 F0, 0.8 F0, 0.9 F0, 0.95 F0, etc.

[0028] Specifically, the particle size of the discrete solid filler 4 is less than 1 / 4 of the shortest side length or diameter of the internal cavity of the second metal workpiece 2. A discrete solid filler 4 with a small particle size is preferred to improve the uniformity of pressure in all directions and better achieve welding of various parts near the blind hole. Preferably, the discrete solid filler 4 is selected from one or more of steel balls, ceramic balls, fine sand, and powder. Preferably, the melting point of the discrete solid filler 4 is greater than the temperature during diffusion welding in S4, ensuring that the discrete solid filler 4 does not melt under high temperature and high pressure conditions during diffusion welding, and has a certain strength to maintain its own shape.

[0029] Specifically, the internal cavity of the first metal workpiece 1 is a through hole structure or a blind hole structure. When it is a through hole structure, a rigid support is fixed at the bottom of the first metal workpiece 1 to form a blind hole structure. The connection interface between the first metal workpiece 1 and the second metal workpiece 2 can be a regular shape such as a circle, square, pentagon, hexagon with consistent cross-sections, or an irregular shape such as a vase with inconsistent cross-sections; when the interface is an irregular shape, the first metal workpiece 1 can be first split and then wrapped and assembled on the outside of the second metal workpiece 2.

[0030] Preferably, before S2, a processing step of the first metal workpiece 1 and the second metal workpiece 2 is also included, and after processing, the surface roughness Ra of the first metal workpiece 1 and the second metal workpiece 2 is less than 0.8. More preferably, a cleaning step is also included after the processing step to remove surface impurities.

[0031] Preferably, after S4, the method further includes removing the internal pressure fixture 5, the external pressure fixture 3 and the discrete solid filler 4, and a finishing step.

[0032] In summary, the present invention fills a discrete solid filler with fluid properties into the cavity of a second metal workpiece assembled in the first metal workpiece, axially pressurizes the second metal workpiece by an external pressure fixture, and at the same time, pressurizes the discrete solid filler by an internal pressure fixture to achieve uniform pressurization of the second metal workpiece in all directions by the discrete solid filler; the second metal workpiece can obtain a large and uniform normal pressure, thereby promoting diffusion welding at the interface between the second metal workpiece and the first metal workpiece, and achieving uniform and stable welding; through small-particle fillers, uniform pressurization of the area near the blind hole can be achieved, avoiding the problems of low interface pressure only through axial pressurization and weak connection at the right-angle part of the root of the blind hole in the prior art.

[0033] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A method for diffusion welding based on the interface method of pressurizing a solid, characterized in that: The steps include: S1. Provide a first metal workpiece and a second metal workpiece to be welded, wherein a cavity is provided in the middle of the first metal workpiece and the second metal workpiece; S2, assembling the second metal workpiece into the inner cavity of the first metal workpiece, and fixing the first metal workpiece; Wherein, the outer wall of the to-be-welded area of ​​the second metal workpiece is in contact and connected with the inner wall of the second metal workpiece; S3, placing an external pressure fixture with a through hole in the middle on top of the second metal workpiece, filling the cavity of the second metal workpiece with discrete solid fillers, and placing an internal pressure fixture in the middle through hole of the external pressure fixture; Wherein, the bottom surface of the internal pressure fixture is in contact with the discrete solid filler, and the side surface is in contact with the inner wall of the external pressure fixture; S4. Under high temperature conditions, the first metal workpiece and the second metal workpiece are diffusion welded by applying downward pressure through an external pressure fixture and an internal pressure fixture.

2. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: Assuming that the solidus temperature of the lower solidus of the first metal workpiece and the second metal workpiece is T0, then in S4, the temperature T of the high temperature condition is: 0.5 T0< T ≤0.95 T0.

3. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: The yield strength of the first metal workpiece and the second metal workpiece, whichever has a lower yield strength, is set to F0. Then, in S4, the downward pressing pressure F is: 0.2 F0< F ≤0.95 F0.

4. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: The particle size of the discrete solid filler is smaller than 1 / 4 of the shortest side length or diameter of the cavity inside the second metal workpiece.

5. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: The discrete solid filler is selected from one or more of steel balls, ceramic balls, fine sand and powder.

6. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: The melting point of the discrete solid filler is greater than the temperature during diffusion welding in S4.

7. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: The internal cavity of the first metal workpiece is a through hole structure or a blind hole structure. When it is a through hole structure, a rigid support is fixed at the bottom of the first metal workpiece before S2 to form a blind hole structure.

8. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: S2 also includes a step of processing the first metal workpiece and the second metal workpiece, and after processing, the surface roughness of the first metal workpiece and the second metal workpiece Ra≤0.

8.

9. The method for diffusion welding based on interface normal solid pressurization according to claim 8, characterized in that: The processing step also includes a cleaning step.

10. The method for diffusion welding based on interface normal solid pressurization according to claim 1, characterized in that: After S4, it also includes the removal of internal pressure fixtures, external pressure fixtures and discrete solid fillers, as well as finishing steps.

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