Welding method and application of high-temperature and high-strength dissimilar alloy

Abstract

The invention discloses a welding method and application of a high-temperature and high-strength dissimilar alloy, and relates to the technical field of metal material welding. An inner core with threads machined on the outer surface and an outer core with threads machined on the inner surface are screwed in to obtain a tightly attached combined to-be-welded part, and a detachable limiting tool is installed on the radial periphery of the combined to-be-welded part to serve as a radial support for welding; a mechanical interlocking structure can be formed between the inner core and the outer disc through the threaded welding seam, when pressure is applied to the threads, the threads of the inner core and the threads of the outer disc extrude each other, two kinds of metal with different properties can be better connected together, a limiting tool is additionally arranged on the periphery of a to-be-welded piece, the overall bearing capacity is improved, and due to the fact that the contact pressure is increased, the mechanical interlocking structure can be formed between the inner core and the outer disc. And the thread teeth can be tightly attached, so that the welding rate can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material welding, and in particular to a welding method and application of high-temperature and high-strength dissimilar alloys. Background Art

[0002] In terms of welding dissimilar metals, diffusion welding has a small overall deformation and good quality of welded joints compared with fusion welding, solid phase pressure welding, brazing and liquid phase transition welding. Dissimilar metal diffusion welding composite components are increasingly widely used in the aerospace field, such as turbine rotors connected by AISI4340 and Inconel718 alloys on advanced aircraft, Cu alloys, Nb alloys and heat-resistant steel connections in thrust chambers of high-performance liquid rocket engines, and Ti alloys and stainless steel connections on space shuttle engine devices. Diffusion welding technology is used.

[0003] The conventional fusion welding method for a centrifugal impeller with heterogeneous dual alloys has problems such as large deformation, low strength at the joint of parts, and failure to meet the application requirements of long life and high strength. The deformation of the two base materials during the high temperature and high pressure welding process directly affects the dimensional accuracy and geometric shape of the structural parts, especially for structural parts that require high precision. Therefore, how to improve the welding quality, achieve overall reliable connection of heterogeneous dual alloys, and reduce unnecessary deformation has become one of the technical problems that need to be solved in this field.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The purpose of the present invention is to provide a high-temperature and high-strength welding method and application of dissimilar alloys to solve the above technical problems.

[0006] The present invention is achieved in that: In the first aspect, an embodiment of the present invention provides a high-temperature and high-strength welding method for dissimilar alloys, which comprises: screwing an inner core with an outer surface thread and an outer disk with an inner surface thread together to obtain a tightly fitting combined welded part, and installing a removable limiting tooling on the radial periphery of the combined welded part as a radial support; the inner core and the outer disk are dissimilar alloys, and the dissimilar alloys are independently selected from any one of titanium alloy, niobium alloy and copper alloy.

[0007] In a second aspect, an embodiment of the present invention provides an application of a high-temperature and high-strength dissimilar alloy produced by the aforementioned welding method in the aerospace field.

[0008] The present invention has the following beneficial effects: The embodiment of the present invention provides a high-temperature and high-strength welding method for dissimilar alloys, wherein the inner core of the outer surface processed thread and the outer disk of the inner surface processed thread are screwed together to obtain a tightly fitting combined welded part, and a detachable limit tool is installed on the radial periphery of the combined welded part as a radial support; the threaded weld can form a mechanical interlocking structure between the inner core and the outer disk, and when pressure is applied to the thread, the threads of the inner core and the outer disk are squeezed against each other, which can better connect two metals of different properties together, and can also withstand a certain shear force, thereby improving the overall load-bearing capacity and effectively improving the welding rate. The dissimilar alloys prepared by the present invention are expected to be used in the aerospace field. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0010] Figure 1 It is a schematic diagram of the structure of the assembly of the parts to be welded and the limiting tooling at the first viewing angle; Figure 2 It is a schematic diagram of the thread engagement and tooling structure of the assembled parts to be welded at a second viewing angle; Figure 3 It is a schematic diagram of thread size; Figure 4 It is a schematic diagram of the structure of the inner core from the first perspective; Figure 5 It is a schematic diagram of the structure of the outer disk in the first perspective; Figure 6 It is a schematic diagram of the deformation of the combined welded parts before and after left and right welding; Figure 7 It is a schematic diagram of the deformation of the combined welded parts before and after upper and lower welding; Figure 8 It is a schematic diagram of the welding structure of the combined threaded surface and flat surface of the welded part.

[0011] Icons: 100-Schematic diagram of the structure of the combined welded parts and the limiting fixture assembled from the first perspective; 101-first welding pressure plate; 102-first limiting fixture; 103-second limiting fixture; 104-outer disk; 1041-inner surface of the outer disk; 105-second welding pressure plate; 106-inner core; 1061-outer surface of the inner core; 1062-inner core diameter; 107-first boss; 1071-vertical height of the first boss; 1072-radial width of the first boss; 108-second boss; 1081-vertical height of the second boss; 1082-radial width of the second boss; 10 9-diameter of annular cylinder; 200-schematic diagram of thread engagement and tooling structure of combined workpiece to be welded at the second viewing angle; 300-schematic diagram of thread size; 301-tooth angle; 302-radius of fillet; 303-tooth pitch; 400-left and right welding; 401-before first deformation; 402-after first deformation; 403-first pressure direction; 404-first deformation direction; 500-upper and lower welding; 501-before second deformation; 502-after second deformation; 503-second pressure direction; 504-second deformation direction; 600-schematic diagram of welding structure of thread surface and plane of combined workpiece to be welded. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0013] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0014] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0015] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0016] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0017] In view of the technical problems existing in the centrifugal impeller heterogeneous dual alloy, the present invention uses diffusion welding technology and designs threaded welding surfaces for the welded parts, which effectively improves the overall reliable connection of the heterogeneous dual alloys and reduces unnecessary deformation. The specific implementation process is as follows: In the first aspect, an embodiment of the present invention provides a high-temperature and high-strength welding method for dissimilar alloys, which comprises: screwing together an inner core 106 with threads processed on the outer surface and an outer disk 104 with threads processed on the inner surface to obtain a tightly fitted combined welded part (including a welded part A and a welded part B), and installing a detachable limiting tooling on the radial periphery of the combined welded part as a radial support; the inner core 106 and the outer disk 104 are dissimilar alloys, and the dissimilar alloys are independently selected from any one of titanium alloy, niobium alloy and copper alloy.

[0018] It should be noted that the present invention designs a threaded welding surface on the surface of the workpiece to be welded, and the weld of the threaded welding surface is in a threaded wave shape. Compared with the flat or inclined surface pressurization, the threaded weld can disperse the stress more effectively. When the workpiece to be welded is subjected to external force, the stress will be distributed along the threaded weld and will not be concentrated in a certain point or a small area, reducing the possibility of cracks or fractures in the weld due to stress concentration. The radial pressure is made more uniform, the axial compression deformation is small, the overall bulge is thickened, and it is easier to weld.

[0019] In addition, the threaded weld can form a mechanical interlocking structure between the inner core 106 and the outer disk 104. This interlocking increases the shear and tensile strength of the weld. When welding dissimilar metal materials, the threaded weld can better connect two metals of different properties. When pressure is applied to the thread, the threads of the inner core 106 and the outer disk 104 squeeze each other and can withstand a certain shear force, thereby improving the overall load-bearing capacity. As the contact pressure increases, the threads will fit tightly together, and this tight fit can effectively improve the welding rate.

[0020] In addition, in an optional embodiment of the present invention, the welding of the dissimilar alloys is performed in the axial direction of the welded parts, not in the radial direction, to achieve left-right welding 400. That is, the first pressure direction 403 is perpendicular to the first deformation direction 404 of the dissimilar alloys. This method makes it easier to compress the threads between the two thread surfaces to a smaller and more rounded state, thereby obtaining a tightly fitting weld. Figure 6 .

[0021] Specifically, in an optional embodiment of the present invention, the outer disk 104 and the inner core 106 are left-right welded 400, and the weld is a vertical weld, that is, the weld between the outer disk 104 and the inner core 106 is a wavy weld perpendicular to the horizontal plane.

[0022] If the combined welded parts (including the welded parts A and B) are welded up and down 500, the deformation of the combined welded parts after the pressure is applied is from top to bottom, that is, the second pressure direction 503 is the same as the second deformation direction 504 of the dissimilar alloy, so that the two thread surfaces are compressed to a state with a larger fillet and a more flat surface. The specific schematic diagram of the upper and lower welding of the combined welded parts 500 is shown in FIG. Figure 7 , the contact surface of the combined welded parts 501 before the second deformation is a threaded surface, and the contact surface of the combined welded parts 502 after the second deformation is a plane. This welding method is more suitable for plane welding and is not suitable for the welding method of the present invention, avoiding increased cost investment and causing raw material loss.

[0023] If the surface of part A in the combined welded parts (including parts A and B) is a plane or an inclined plane, and the surface of part B is a threaded surface, when the left and right welds are 400 degrees, their welding surfaces cannot be completely in contact. Obviously, if effective welding is to be performed, it is necessary to apply huge pressure to make the threaded surface of part B deform greatly and tend to be flat before welding with the plane of part A, which consumes resources and is difficult to weld. If huge pressure is not used to make it deform greatly, the weld will have holes, resulting in a completely unqualified weld, resulting in a waste of resources and increased investment costs. Schematic diagram of the welding structure of the combined welded parts with threaded surfaces and planes at 600 degrees. Figure 8 .

[0024] In an optional embodiment of the present invention, the alloys of the inner core 106 and the outer disk 104 are independently selected from any one of titanium alloy, niobium alloy and copper alloy. Specifically, in one embodiment of the present invention, the inner core 106 and the outer disk 104 are heterogeneous titanium alloys, which are a combination of TC4 and TA15; in other embodiments of the present invention, other heterogeneous alloys that meet the high temperature and high strength combination can be selected according to actual needs, such as copper alloys of different grades, niobium alloys of different grades, or titanium alloys of different grades, titanium alloys and copper alloys, niobium alloys and copper alloys; it should be noted that when the type of alloy, production batch or manufacturer changes, the corresponding heating temperature and holding time during welding also need to be reasonably adjusted according to actual conditions.

[0025] It should be noted that the composition, structure and performance of the welded joint are close to or the same as those of the parent material, and there are no fusion welding defects, overheated structures and heat-affected zones in the weld. This makes the joint strength, toughness, corrosion resistance and other properties of the dissimilar metals after welding good.

[0026] Specifically in the implementation of the present invention, before welding, it is also necessary to perform diffusion welding simulation analysis on the workpiece to be welded, and build a diffusion welding hole closure model for the workpiece to be welded. In an optional implementation of the present invention, a standard TA15 titanium alloy is selected as the material of the impeller outer disk 104, and its heat treatment state is a solid solution state; a standard TC4 titanium alloy is selected as the material of the impeller inner core 106, and its heat treatment state is a forging state. Among them, the heat treatment state of the workpiece to be welded is related to its material, and can be reasonably adjusted according to actual needs.

[0027] In an optional embodiment of the present invention, the external thread of the inner core 106 matches the internal thread size of the outer disk 104, wherein the thread angle 301 is 30°-60°. Figure 3 .

[0028] It should be noted that the thread angle 301, pitch 303 and fillet radius 302 of the thread satisfy the following relationship: For ordinary threads, there is no fixed formula association between them. The tooth angle 301 is the angle between two adjacent tooth sides on the thread tooth profile. For example, the tooth profile angle of ordinary metric threads is 60°. The pitch 303 (pitch) refers to the axial distance between two corresponding points on the mid-diameter line of two adjacent teeth, which is mainly determined according to the specifications and standards of the thread. The fillet radius 302 is mainly to reduce stress concentration, and its size is usually determined according to the specific thread design standards and usage requirements.

[0029] In general, there is the following relationship between the fillet radius 302 and the pitch 303 of the thread: r=H / 6=0.1443P (1), where H is the original triangle height of the thread profile (mm), r is the fillet radius 302 (mm), and P is the pitch 303 (mm).

[0030] There is no direct mathematical relationship between the tooth angle 301 and the pitch 303 and the fillet radius 302 , but the tooth angle 301 will affect the shape and force distribution of the thread, and thus indirectly affect the design values ​​of the pitch 303 and the fillet radius 302 .

[0031] When the tooth angle 301 and the tooth pitch 303 are determined, the fillet radius 302 can be calculated according to formula (1). By setting the parameters within the range, the possibility of cracks or fractures in the weld between dissimilar alloys can be avoided, and the firmness of the weld joint can be ensured.

[0032] The processing of the thread belongs to the type of mechanical processing, wherein the structural schematic diagram of the inner core 106 processed with the thread in the first perspective is shown in FIG. Figure 4 The schematic diagram of the structure of the outer disk 104 with threads in the first viewing angle is shown in FIG. Figure 5 .

[0033] It should be noted that, when the inner core 106 and the outer disk 104 are screwed and in close contact, threads with a tooth angle 301 within this range are easy to weld; in addition, the size of the tooth angle 301 is directly related to the size of the workpiece to be welded, and the smaller the workpiece to be welded, the smaller the impact of the tooth angle 301.

[0034] In an optional embodiment of the present invention, before the workpiece to be welded is threaded, it also includes: selecting a dissimilar alloy that meets the standards as the workpiece to be welded; checking the chemical composition and mechanical properties of the workpiece to be welded to ensure that the workpiece to be welded has no cracks or inclusions, and the surface is clean and free of oil stains and rust; and formulating diffusion welding process parameters and welding procedures based on the material properties of the workpiece to be welded.

[0035] It should be noted that before processing the threads, design drawings, CNC programming and other operations are required to ensure the precision of the threads so that the welded parts can fit tightly when screwed together and tightened.

[0036] Specifically, the processing method, processing speed, cutting depth and other parameters need to be considered during the CNC programming process to ensure the processing quality and efficiency. Prepare CNC milling machines, CNC lathes, grinding wheel grinders and other processing equipment, and check their accuracy and stability. Prepare clamping tools, cutting tools (such as carbide, ceramic or cubic boron nitride cutting tools) and measuring tools. According to the design drawings and size requirements of the outer disk 104 and the inner disk, the outer surface 1061 of the inner core and the inner surface 1041 of the outer disk are forged and threaded so that the size of the mating surface of the outer disk 104 and the inner core 106 reaches the designed size. Ensure the surface finish and roughness, and require the surfaces of the two to be welded to be smooth and closely matched.

[0037] In an optional embodiment of the present invention, after the workpiece to be welded is threaded, the process further includes: cleaning the processed workpiece to be welded with a cleaning solvent to ensure that the threaded surface of the workpiece to be welded is clean and free of grease, dust, fingerprints, and water marks, and checking that the surface of the tooling is free of dents, pits, protrusions, and debris; then, assembling the workpiece to be welded, the limit tooling, and the welding pressure plate to obtain a blank. Figure 1 Schematic diagram of the structure of the combined welded parts and the limit fixture in the first perspective and Figure 2 The combined welded parts are assembled according to the structural diagram of the thread engagement and the tooling structure at the second viewing angle.

[0038] It should be noted that the cleaning solvent used in the present invention belongs to chemical cleaning. This method can effectively remove pollutants such as welding slag, oxides and grease, but attention should be paid to the selection and use of reagents to avoid damage to the material.

[0039] Furthermore, the cleaning solvent includes at least one of acetone, Keeler reagent and alcohol. In other embodiments of the present invention, the cleaning solvent can be reasonably selected as needed, or other cleaning methods can be used, such as mechanical cleaning using tools such as brushes, grinding wheels and sandpaper; electrochemical cleaning using electrolytes, etc.

[0040] In an optional embodiment of the present invention, the cleaned threaded parts to be welded are screwed together and tightened to obtain a combined part to be welded. Then, a detachable stopper is installed on the radial periphery of the combined part to be welded to obtain a blank and perform welding. Figure 3 .

[0041] In an optional embodiment of the present invention, the limiting tooling includes a first limiting tooling 102 and / or a second limiting tooling 103 that can be detachably installed; wherein the first limiting tooling 102 contacts the radial outer surface of the outer disk 104, and the second limiting tooling 103 is away from the outer disk 104 and is located on the periphery of the first limiting tooling 102.

[0042] It should be noted that the limiting tooling can be designed according to the shape of the workpiece and the welding requirements. By fixing and positioning the workpiece, the movement and deformation of the workpiece to be welded during the welding process can be reduced, and the occurrence of irregular welds and welding deformation can be reduced, thereby improving the welding rate and production efficiency.

[0043] In an optional embodiment of the present invention, two layers of inner and outer limiting fixtures are set to constrain and limit the radial periphery of the combined parts to be welded in order to ensure that the pressure applied during the welding process is uniform and controllable. As a radial support for the compression process, the parts to be welded will be easier to weld. Affected by the material of the parts to be welded, if only one layer of limiting fixture is made, it is easy to weld the fixture to the parts to be welded, and it is difficult to disassemble the fixture after welding. The fixture of the layered inner and outer ring structure in the present invention is made, and the inner layer is divided and welded for easy removal. If the material of the parts to be welded is adjusted, the inner layer limiting fixture can also be selected not to be divided, and the limiting welding can be performed directly. In other embodiments of the present invention, if the alloy material of the parts to be welded is changed, the limiting fixture can select one or two layers according to actual needs.

[0044] In an optional embodiment of the present invention, the inner core 106 and the outer disk 104 are both cylinders, wherein the outer disk 104 is an annular cylinder with a hollow axial center, and the diameter 109 of the annular cylinder is the same as the inner core diameter 1062. A first boss 107 for placing a position limiting tool is provided on the axial periphery of the outer disk 104, the vertical height 1071 of the first boss is greater than the vertical height of the position limiting tool, and the radial width 1072 of the first boss is greater than or equal to the radial width of the position limiting tool, so as to facilitate supporting and stabilizing the position limiting tool; at the other axial end of the outer disk 104, a second boss 108 having a radial width greater than the radial width 1072 of the first boss and a vertical height lower than the vertical height 1071 of the first boss is provided at a position corresponding to the first boss 107. In other embodiments of the present invention, the vertical height 1081 of the second boss and the radial width 1082 of the second boss can be reasonably adjusted according to actual needs.

[0045] It should be noted that the position limiting tool is set on the first boss 107, which is related to the shape of the outer disk 104. The shape of the outer disk 104 in this embodiment has been verified, and the requirement can be met by only setting the tool on the first boss 107; if the shape of the outer disk 104 changes, the tool position limiting can also be performed on the first boss 107 and the second boss 108 at the same time. In other embodiments of the present invention, if there is no boss, a corresponding tool trap that conforms to the shape of the outer disk 104 can also be set according to the specific shape.

[0046] In an optional embodiment of the present invention, a solder resist is coated at the contact point between the first limiting tool 102 and the outer disk 104 , and the solder resist is selected from any one of boron nitride, silicon nitride, boron carbide and silicon carbide.

[0047] It should be noted that solder resist is a material with high hardness, high strength, high wear resistance and high temperature stability, and has excellent mechanical properties and high thermal conductivity. In the embodiment of the present invention, solder resist is applied between the limiting fixture and the combined parts to be welded, which has the following functions: to prevent the limiting fixture and the parts to be welded from fusing and welding together during the welding process; to ensure the stability of the welding process and the easy disassembly of the limiting fixture after the welding is completed.

[0048] In an optional embodiment of the present invention, the axial dimensions of the inner core 106 and the outer disk 104 are equal; when welding, welding pressure plates are respectively installed at the axial ends of the combined welded parts, and the welding pressure plates are not in contact with the surface of the limiting fixture. The structural schematic diagram 100 of the combined welded parts and the limiting fixture assembled at the first viewing angle is shown in FIG. Figure 1 .

[0049] Specifically, the welding platen includes a first welding platen 101 and a second welding platen 105, wherein the first welding platen 101 is assembled on a side close to the limiting tooling, and the second welding platen 105 is assembled on a side away from the limiting tooling.

[0050] It should be noted that the welding pressure plates are arranged at both axial ends of the combined parts to be welded. By providing stable support and pressure, the applied pressure is directly applied to the welding pressure plates during the welding process, which can reduce stress concentration during the welding process and ensure the stability of the parts to be welded.

[0051] The welding pressure plate is not in contact with the surface of the limiting tooling to avoid the pressure applied in the axial direction and the radial direction of the combined welded parts during the pressure application process. Under the action of the double pressure, the limiting tooling may be damaged and the radial support may be missing, causing the combined welded parts to shift or deform, resulting in the interruption of the welding process and ultimately affecting the mechanical properties of dissimilar alloys.

[0052] It should be noted that the material of the position limiting fixture has good mechanical properties at high temperatures. In an optional embodiment of the present invention, the material of the position limiting fixture is selected from any one of an iron-based high-temperature alloy, a nickel-based high-temperature alloy, and a cobalt-based high-temperature alloy. The specific use category can be reasonably selected according to the material composition of the actual welded part. Specifically in one embodiment of the present invention, the material of the position limiting fixture is a nickel-based high-temperature alloy GH4169.

[0053] In an optional embodiment of the present invention, the blank is pre-positioned into the furnace, and a clamping tool is used to firmly and accurately clamp the blank on the processing equipment; wherein the clamping tool includes a three-jaw self-centering chuck.

[0054] Furthermore, the welding method also includes: after checking that the water cooling system, vacuum system, hydraulic system and heating system of the welding equipment are normal and there are no alarms, cleaning the furnace with a vacuum cleaner, and turning on the diffusion pump 30 minutes to 50 minutes in advance to preheat the diffusion welding equipment; then, welding is performed according to the established diffusion welding process parameters.

[0055] In an optional embodiment of the present invention, diffusion welding is performed on the assembled parts to be welded after the limit fixture is installed. The heating method of diffusion welding is thermal radiation, the heating temperature is 845°C-905°C, and the vacuum degree is 3.7×10 -2 Pa-4.2×10 - 2 Pa, the heating rate is 4℃ / min-8℃ / min.

[0056] It should be noted that, in terms of welding dissimilar metals, diffusion welding has less overall deformation and better quality of welded joints than fusion welding, solid phase pressure welding, brazing and liquid phase transition welding. Diffusion welding forms a metallurgical bond through mutual diffusion between atoms. This bonding method has higher bonding strength than ordinary mechanical connection or adhesive bonding, and the joint is firm and reliable, and is not prone to loosening or breaking. During the welding process, due to the overall heating and pressurization, the temperature distribution of the weldment is relatively uniform, and the stress at the welded joint is also relatively uniform, which helps to improve the fatigue life and reliability of the welded structure and reduce joint failure caused by stress concentration.

[0057] In addition, the composition of the weld joint is the intermediate transition composition of the two metals to be welded, and its density is between the metals to be welded, so there will be no sudden drop in the density value at the joint. The microstructure and performance of the joint are close to or the same as those of the base metal, there are no melting defects in the weld, and there is no heat-affected zone with overheated structure. Whether it is the same material with poor plasticity or high melting point, or dissimilar metal materials that do not dissolve in each other or produce intermetallic compounds during fusion welding, a relatively strong weld joint can be obtained.

[0058] In an optional embodiment of the present invention, during the heating process of the combined parts to be welded, the heating temperatures are kept at 285°C-315°C, 685°C-715°C and 805°C-835°C for 30min-90min respectively, wherein the combined parts to be welded are pressurized when the heating temperature is 805°C-835°C; then, the heating is stopped after being kept at 845°C-905°C for 60min-150min.

[0059] Specifically, the heating temperature and its corresponding holding time can be reasonably set according to actual needs. The magnitude of the applied pressure can be reasonably set according to the size of the actual welded parts.

[0060] It should be noted that the temperature of diffusion welding has a crucial influence on the quality of the joint. In theory, the higher the temperature, the faster the atomic diffusion rate, which helps to form a more uniform diffusion transition layer. However, too high a temperature may cause the material to melt, oxidize or evaporate, thereby reducing the quality of the weld. After the applied pressure reaches the set value, it continues until the end of welding and then the pressure is relieved.

[0061] Specifically in the embodiments of the present invention, if the insulation temperature or the heating rate of the diffusion welding is not within the set range, or the insulation diffusion time is less than the set range, the obtained welding effect is not good.

[0062] In the present invention, the diffusion welding method for heating the combined welded parts is staged heating, which includes a heating stage, a pushing stage, and a balancing stage. The characteristics of each stage are as follows: Heating stage: In this stage, the temperature of the joint is raised to a temperature at which diffusion can occur. Usually, the surface temperature of the joint rises first, and then the heat energy is conducted inward, causing the temperature of the deeper part to rise as well.

[0063] Advancement phase: In this phase, the atoms in the joint begin to diffuse, forming a solid solution state with uniform point distribution. The atoms spontaneously diffuse from the high concentration area to the low concentration area, making the chemical composition of the joint gradually diffuse uniformly. Over time, the diffusion welding area will expand and the depth will increase accordingly.

[0064] Equilibrium stage: In this stage, the temperature of the joint has risen and the atoms have diffused to the required positions. At this point, the concentration of atoms on the interface has reached a thermodynamic equilibrium state, that is, the chemical components dissolved in the solid state have diffused to a certain degree of uniformity. The heat source gradually weakens until it disappears, and the joint cools to form a high-strength continuous and uniform joint.

[0065] The diffusion welding time is also a key factor affecting the welding quality. Sufficient time allows the atoms to fully diffuse and form a complete diffusion transition layer. However, too long a time may lead to excessive diffusion and affect the performance of the welded joint.

[0066] When determining the welding time, it is necessary to consider the material type, thickness and required joint performance. Generally speaking, the holding time is determined according to the specific material and thickness.

[0067] The temperature and time of diffusion welding do not exist in isolation, but need to be considered and optimized comprehensively. The appropriate combination of temperature and time can ensure the integrity and uniformity of the diffusion transition layer, thereby improving the mechanical properties and corrosion resistance of the joint.

[0068] In an optional embodiment of the present invention, pressure is applied in the axial direction of the combined workpiece to be welded, and when the size of the combined workpiece to be welded is doubled, the applied pressure increases by 3 to 5 times; further, when the size of the combined workpiece to be welded is doubled, the applied pressure increases by 4 times.

[0069] Specifically, in an optional embodiment of the present invention, Figure 1 and Figure 2 The figure shows the full-size welded parts. When the welded parts are 1 / 4 size, the pressure is 8t-10t; when the welded parts are 1 / 2 size, the pressure is 36t-40t; when the welded parts are full size, the pressure is 140t-160t.

[0070] Only when the pressure applied to the combined welded parts is within the set range can a dissimilar alloy with small axial compressive deformation, roughening, less residual stress on the welding surface, good fatigue strength and good wear resistance be produced.

[0071] In an optional embodiment of the present invention, after stopping heating, when the furnace cools to a temperature <200°C, the automatic program of the equipment is turned off, the vent valve is opened, and the furnace door is opened for cooling. Figure 6 , the left side is 401 before the first deformation, and the right side is 402 after the first deformation.

[0072] In an optional embodiment of the present invention, the welded dissimilar alloys are heat treated.

[0073] It should be noted that the heat treatment of the welded dissimilar alloys can be selected from tempering heat treatment and aging heat treatment according to actual needs.

[0074] In a second aspect, an embodiment of the present invention provides an application of a dissimilar alloy produced by the aforementioned welding method in the aerospace field.

[0075] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0076] Example 1 This embodiment provides a high-temperature and high-strength welding method for dissimilar alloys, which includes the following preparation steps: (1) A TA15 titanium alloy that meets the standards is selected as the material of the impeller outer disk 104, and its heat treatment state is a solid solution state; a TC4 titanium alloy that meets the standards is selected as the material of the impeller inner core 106, and its heat treatment state is a forging state.

[0077] Conduct TC4 / TA15 diffusion welding simulation analysis and build TC4 and TA15 diffusion welding hole closure models.

[0078] (2) Before machining, check the chemical composition and mechanical properties of the inner core 106 and the outer disc 104 to ensure that they meet the standards and that the materials are free of defects such as cracks and inclusions. The surface is clean and free of oil stains, rust, etc.

[0079] (3) Design drawings and perform CNC programming. During the programming process, parameters such as processing method, processing speed, and cutting depth need to be considered to ensure processing quality and efficiency. Prepare CNC milling machines, CNC lathes, grinding wheel grinders and other processing equipment, and check their accuracy and stability. Prepare clamping tools, cutting tools (such as carbide, ceramic or cubic boron nitride cutting tools) and measuring tools. According to the design drawings and size requirements of the impeller outer disk 104 and the inner core 106, thread processing is performed on the TC4 inner core outer surface 1061 and the TA15 outer disk inner surface 1041 titanium alloy material. The results are as follows: Figure 4 A schematic diagram of the structure of the inner core 106 at a first viewing angle and Figure 5 The outer disc 104 is a schematic diagram of the structure in the first perspective. The mating surfaces of the impeller outer disc 104 and the inner core 106 are finely processed to make the size of the parts reach the designed size. The surface finish and roughness are guaranteed, and the surfaces to be welded are required to be smooth and closely matched.

[0080] In order to ensure that the pressure is applied evenly and controllably during welding, it is necessary to use appropriate tooling to constrain and limit the welding process. Figure 2 The first stopper 102 and the second stopper 103 shown in the schematic diagram 200 of the threaded engagement and tooling structure of the assembled welded parts at the second viewing angle serve as radial supports during the compression process. The tooling material is nickel-based high-temperature alloy GH4169 with good mechanical properties at high temperatures.

[0081] (4) After machining, use acetone to remove oil, and then use Keeler reagent and alcohol to clean to ensure that the surface of the TC4 / TA15 thread to be welded is clean and free of grease, dust, fingerprints, water marks, etc. Also check that there are no bumps, pits, protrusions, or debris on the surface of the limit fixture.

[0082] (5) Check that the water cooling system, vacuum system, hydraulic system, and heating system of the welding equipment are normal and have no alarms. Use a vacuum cleaner to clean the furnace, etc., and turn on the diffusion pump 40 minutes in advance to preheat the diffusion welding equipment.

[0083] (6) Apply boron nitride solder resist on the contact surface between the first limiting fixture 102 and the outer disk 104 to prevent the outer disk 104 from sticking to the limiting fixture. After applying the solder resist, blow it dry with compressed air and check the surface quality. There should be no obvious particles and the surface should be evenly coated.

[0084] (7) Press the inner core 106, the outer plate 104, the first position limiting fixture 102, the second position limiting fixture 103, the first welding plate 101 and the second welding plate 105 together. Figure 1Assemble and press the blank according to the schematic diagram. Pre-tighten the closed loop by 20KN and close the furnace door.

[0085] (8) Diffusion welding is performed according to the established process plan. The diffusion welding temperature of TC4 / TA15 dual alloy is 870℃±5℃. In this embodiment, the heating process adopts thermal radiation heating. First, close the furnace door and evacuate the vacuum. When the vacuum degree reaches 4×10 -2 Pa, start heating, heating rate is 5℃ / min. Control the temperature at 300℃, 700℃, 820℃, keep warm for 90min respectively; apply pressure of 160t at 820℃, and keep pressure until welding is finished; keep warm at 850℃ for 30min; and turn off heating after 120min of heat preservation and diffusion at 870℃.

[0086] (9) The cooling process adopts furnace cooling. When the temperature inside the furnace is lower than 200℃, turn off the automatic program of the equipment, open the air valve, and open the furnace door for cooling.

[0087] (10) Disassemble the first stopper 102 and the second stopper 103, and clean the surface of the dissimilar alloys. Schematic diagram 400 of deformation of the combined welded parts before and after left and right welding 400 Figure 6 .

[0088] (11) The welded dissimilar alloys are aged according to the heat treatment process to obtain the optimal comprehensive mechanical properties.

[0089] In summary, the high-temperature and high-strength dissimilar alloy welding method provided in the embodiment of the present invention can form a mechanical interlocking structure between the inner core 106 and the outer disk 104 by using a threaded weld. This interlocking increases the shear and tensile strength of the weld. When welding dissimilar metal materials, the threaded weld can better connect two metals of different properties together. When pressure is applied to the thread, the threads of the inner core 106 and the outer disk 104 squeeze each other and can withstand a certain shear force, thereby improving the overall load-bearing capacity. As the contact pressure increases, the threads will fit tightly together, and this tight fit can effectively improve the welding rate.

[0090] Compared with ordinary flat welds, threaded welds can disperse stress more effectively. When a component is subjected to external force, the stress will be distributed along the threaded weld and will not be concentrated at a certain point or small area, reducing the possibility of cracks or breaks in the weld due to stress concentration.

[0091] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high temperature and high strength welding method for dissimilar alloys, characterized in that: The welding method comprises: screwing together an inner core of an outer surface thread and an outer coil of an inner surface thread to obtain a tightly fitted combined welded part, and installing a detachable limiting tool as a radial support on the radial periphery of the combined welded part; The inner core and the outer disk are made of heterogeneous alloys, and the heterogeneous alloys are independently selected from any one of titanium alloy, niobium alloy and copper alloy.

2. The welding method according to claim 1, characterized in that: The external thread of the inner core matches the internal thread of the outer disk in size, wherein the thread angle is 30°-60°.

3. The welding method according to claim 1, characterized in that: The position limiting tooling includes a first position limiting tooling and / or a second position limiting tooling that can be detachably installed; Wherein, the first limiting fixture is in contact with the radial outer surface of the outer disk, and the second limiting fixture is away from the outer disk and is located at the periphery of the first limiting fixture; The axial dimensions of the inner core and the outer disk are equal; during welding, welding pressure plates are respectively installed at the axial ends of the combined welded parts, and the welding pressure plates do not contact the surface of the limiting tooling; The material of the limiting fixture is selected from any one of an iron-based high-temperature alloy, a nickel-based high-temperature alloy and a cobalt-based high-temperature alloy.

4. The welding method according to claim 3, characterized in that: A solder resist is coated at the contact point between the first limiting tool and the outer disk, and the solder resist is selected from any one of boron nitride, silicon nitride, boron carbide and silicon carbide.

5. The welding method according to claim 1, characterized in that: The combined welded parts with the limit fixture installed are subjected to diffusion welding. The heating method of the diffusion welding is thermal radiation. The heating temperature is 845°C-905°C and the vacuum degree is 3.7×10 -2 Pa-4.2×10 -2 Pa, the heating rate is 4℃ / min-8℃ / min.

6. The welding method according to claim 5, characterized in that: During the heating process of the combined welded parts, the heating temperatures are 285°C-315°C, 685°C-715°C and 805°C-835°C respectively for 30min-90min, wherein the combined welded parts are subjected to pressure treatment when the heating temperature is 805°C-835°C; and then the combined welded parts are kept at 845°C-905°C for 60min-150min before stopping the heating; After stopping heating and cooling with the furnace to a temperature <200℃, turn off the equipment automatic program, open the vent valve, and open the furnace door to cool.

7. The welding method according to claim 6, characterized in that: Apply pressure in the axial direction of the combined workpiece to be welded; when the size of the combined workpiece to be welded doubles, the applied pressure increases by 3 to 5 times.

8. The welding method according to claim 1, characterized in that: Before the thread processing of the workpiece to be welded is performed, the method further includes: selecting a heterogeneous alloy that meets the standards as the workpiece to be welded; checking the chemical composition and mechanical properties of the workpiece to be welded to ensure that the workpiece to be welded has no cracks or inclusions, and the surface is clean and free of oil stains and rust; formulating diffusion welding process parameters and welding procedures according to the material properties of the workpiece to be welded; After the workpiece to be welded is threaded, the process also includes: cleaning the processed workpiece to be welded with a cleaning solvent to ensure that the thread surface of the workpiece to be welded is clean and free of grease, dust, fingerprints, and water marks, and checking that the surface of the tooling is free of dents, pits, protrusions, and debris; then, assembling the workpiece to be welded, the limiting tooling, and the welding pressing plate to obtain a blank; The cleaning solvent includes at least one of acetone, Keeler reagent and alcohol.

9. The welding method according to claim 8, characterized in that: Pre-positioning the blank into the furnace, and firmly and accurately clamping the blank on the processing equipment using a clamping tool; wherein the clamping tool includes a three-jaw self-centering chuck; The welding method further comprises: after checking that the water cooling system, vacuum system, hydraulic system and heating system of the welding equipment are normal and have no alarm conditions, cleaning the furnace with a vacuum cleaner, and turning on the diffusion pump 30 minutes to 50 minutes in advance to preheat the diffusion welding equipment; then, welding is performed according to the formulated diffusion welding process parameters; and / or, heat treating the welded dissimilar alloys.

10. Application of a high-temperature and high-strength dissimilar alloy obtained by the welding method according to any one of claims 1 to 9 in the field of aerospace.

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