Connecting method for laser melting deposition structural parts

Abstract

The invention provides a connecting method of a laser melting deposition structural member, which is used for connecting two metal members, and comprises the following steps: prefabricating a 45-degree inclined plane at the connecting end of one metal member, and processing a contact plane at the top end connecting part of the inclined plane; a 45-degree inclined plane is prefabricated at the connecting end of the other metal component, and a plane boss corresponding to the contact plane is reserved at the connecting position of the top end of the inclined plane; and the contact plane and the plane boss are connected through laser melting, so that the two metal components are connected. According to the invention, the connecting area of the two connecting pieces is improved from linear contact to plane contact, so that the problem of light leakage is effectively avoided or reduced, and the energy utilization rate is improved; and the two connecting pieces are accurately positioned in the connecting process, the problem of high-low dislocation of the two connecting pieces is avoided, and the flatness of the connecting pieces is better controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing (laser melting deposition), and more specifically, to a method for connecting laser melting deposition structural parts. Background Art

[0002] Additive Manufacturing (AM) technology refers to a technology based on the discrete-accumulation principle, which is driven by the three-dimensional data of the parts and uses the method of gradual accumulation of materials to directly manufacture physical parts. If classified according to the type and method of processing materials, it can be divided into metal forming, non-metal forming, biomaterial forming, etc. Among them, additive manufacturing of metal forming includes melt deposition, vapor deposition, block solder mask, liquid deposition and other methods.

[0003] In recent years, laser melting deposition (LMD) technology has been widely used in the aerospace field because of its ability to quickly form large, complex, and high-performance structural parts. It can significantly reduce the manufacturing cost and processing cycle of metal components in the aerospace field.

[0004] Based on the further large-scale and integrated requirements of the aerospace field for laser melting deposition metal components, and at the same time limited by the size of parts, part structure, forming equipment size, thermal stress during the forming process and the influence of part deformation, for large laser melting deposition components, the process method of "segmented laser rapid forming + overall laser connection forming" is usually adopted. Through the connection method, connection process and connection process deformation control technology, the laser connection forming process is controlled to prevent serious deformation and cracking, and the internal metallurgical quality meets the design requirements. In the existing connection forming process, large laser melting deposition structural parts are usually connected in the positive and negative directions with a 45° sharp groove, such as Figure 1 shown.

[0005] However, the existing large-scale laser melting deposition structural parts connection adopts the method of opening a 45° sharp groove at the interface position to connect and form in the positive and negative directions, which has the following disadvantages: ① If the sharp grooves of the two connecting parts are in direct line contact, the angle between the laser head angle and the forming plane during the connection process is 85 degrees (5 degrees away from the vertical forming plane, Figure 2② In order to reduce the potential risk of the line contact not being melted by the laser, a certain gap may exist at the line contact position, and defects may exist at the bonding area, which will reduce the performance of the bonding area; ② In order to reduce the potential risk of the line contact at the sharp groove not being melted, a certain gap is usually reserved at the two grooves during connection to ensure that the interface position is tightly combined, but this method has the problem of light leakage, which makes the laser energy utilization rate low. At the same time, the two grooves may be melted through, causing the gap to expand. When the reserved gap is too large, it will cause the connection to fail directly. ③ When there is a light leakage problem, it is necessary to place a metal pad with the same material or similar composition as the formed part at the bottom of the light leakage area during the connection and forming process to prevent the existing metal components or substrates from being damaged; but this is also easy to introduce unauthorized adhesion. ④ During the forming connection, whether the two sharp grooves are in direct line contact or a certain gap is reserved, there is a risk of inaccurate positioning, which may cause the flatness of the later connected formed parts to be unqualified. At the same time, the Z direction twists up and down during the connection and forming process, resulting in connection deformation and unsatisfactory flatness. ⑤ During the forming connection, it is difficult to locate the two sharp grooves, whether they are in direct line contact or with a certain gap reserved. It is difficult to achieve accurate positioning in one time. It usually requires multiple fine-tuning and multiple scanning after three-dimensional scanning, which takes a long time.

[0006] Based on the problems existing in the above-mentioned existing laser melting deposition structural component connection solutions, a new laser melting deposition structural component connection process is urgently needed. Summary of the invention

[0007] In view of the above problems, an object of the present invention is to provide a method for connecting laser melting deposition structures to solve at least one problem existing in the above existing laser melting deposition structure connection solutions.

[0008] The laser melting deposition structural member connection method provided by the present invention is used to connect two metal components, comprising:

[0009] A 45° bevel is prefabricated at the connection end of one of the metal components, and a contact plane is machined at the top connection of the bevel;

[0010] A 45° inclined surface is prefabricated at the connection end of another metal component, and a plane boss corresponding to the contact plane is reserved at the top connection of the inclined surface;

[0011] The two metal components are connected by laser melting the contact plane and the plane boss.

[0012] In addition, an optional solution is that the two metal components are connected in an "X" shape or a "V" shape at the connection ends.

[0013] In addition, an optional solution is that, in the process of connecting the contact plane and the planar boss by laser melting, a preset gap is reserved at the interface position between the contact plane and the planar boss for laser melting operation.

[0014] In addition, an optional solution is that the height of the contact plane is not greater than 5 mm, and the height of the planar boss in the Z direction is not greater than 5 mm.

[0015] In addition, an optional solution is that the thickness of the planar boss is not greater than 5 mm.

[0016] In addition, an optional solution is that the two metal components connected in an "X" shape are connected in a reverse direction; and the two metal components connected in a "V" shape are connected in a Z direction.

[0017] In addition, an optional solution is to prefabricate a 45° bevel at the connection end, including:

[0018] Prepare a 45° chamfer at the connection end of the metal component by machining;

[0019] This bevel and surrounding area are ground with a rotary file tool;

[0020] Clean the polished bevel surface.

[0021] In addition, an optional solution is that the polished bevel surface is cleaned by first cleaning it with clean water, then cleaning it with anhydrous ethanol, then cleaning it with anhydrous acetone, and finally cleaning it with clean water.

[0022] In addition, an optional solution is to connect the two metal components by laser melting the contact plane and the planar boss, including:

[0023] Single-sided additive manufacturing is used to fix the two metal components by a preset laser additive connection tool so that the contact plane and the plane boss are butted; then laser melting connection is performed at the connection of the two fixed metal components;

[0024] Stress relief annealing treatment is used to perform local stress relief annealing treatment on the laser melting connection position;

[0025] Shape correction annealing treatment is used to perform shape correction annealing treatment on two metal components after stress relief annealing treatment;

[0026] Semi-finishing is used to grind and clean the laser-melted connection position of two metal components after shape correction and annealing.

[0027] In addition, an optional solution is to further include ultrasonic testing to detect the connection status of the laser-melted connection positions of the two metal components after the shaping and de-annealing treatments, after the grinding and cleaning of the laser-melted connection positions of the two metal components.

[0028] By utilizing the above-mentioned method for connecting laser melting deposition structural parts provided by the present invention, the connection area of ​​the two connecting parts can be improved from line contact to plane contact, effectively avoiding or reducing the light leakage problem and improving energy utilization; and the two connecting parts can be accurately positioned during the connection process, avoiding the height misalignment problem of the two connecting parts to a certain extent, and better controlling the flatness of the connecting parts, so that the formed parts can maintain the flatness of the qualified state, and at the same time can reduce deformation in the Z direction.

[0029] In order to achieve the above and related purposes, one or more aspects of the present invention include features that will be described in detail later and are particularly pointed out in the claims. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] By referring to the following description in conjunction with the accompanying drawings and the contents of the claims, and with a more complete understanding of the present invention, other objects and results of the present invention will become more apparent and easily understood.

[0031] Figure 1 It is a schematic diagram of the existing large-scale laser melting deposition using an "X"-shaped 45° sharp bevel to connect in forward and reverse directions;

[0032] Figure 2 It is a schematic diagram of the angle between the existing "X"-shaped 45° line contact connection laser head and the forming surface;

[0033] Figure 3 A process flow of a method for connecting a laser melting deposition structure according to an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of connecting a laser melting deposition structure using an "X"-shaped 45° groove according to an embodiment of the present invention;

[0035] Figure 5 This is a schematic diagram of laser melting deposition structural parts connection using a “V”-shaped 45° groove according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. However, it will be apparent that these embodiments may be practiced without these specific details.

[0037] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] Figure 3 A flow chart of a method for connecting a laser melting deposition structure according to an embodiment of the present invention is shown. Figure 4 and Figure 5 Schematic diagrams of connecting laser melting deposition structural parts through an "X"-shaped 45° groove and a "V"-shaped 45° groove according to an embodiment of the present invention are respectively shown.

[0039] Combined with Figures 3 to 5 As shown together, the laser melting deposition structural component connection method provided by the present invention mainly includes the following steps:

[0040] S320: Prefabricate a 45° bevel at the connection end of one of the metal components, and machine a contact plane at the top connection of the bevel.

[0041] This step S320 is used to achieve the preliminary forming process of the connection end of the metal component. Specifically, as an example, after the additive connection process is determined, one of the metal components to be connected is subjected to rough processing, a 45° bevel is prefabricated at the connection end of the metal component by mechanical processing, and a contact plane is processed at the top connection of the bevel; then the processed bevel, contact plane and surrounding area are polished with a finishing tool (such as a rotary file tool); finally, the polished bevel and contact plane are cleaned to ensure the cleanliness of the connection area.

[0042] In the above cleaning process, a variety of cleaning liquids can be used for cleaning, such as first cleaning with water, then cleaning with anhydrous ethanol, then cleaning with anhydrous acetone, and finally cleaning with water to ensure that the surface of the connection end of the metal component is free of oil and other impurities.

[0043] S340: prefabricate a 45° inclined surface at the connection end of another metal component, and reserve a planar boss corresponding to the contact plane at the top connection of the inclined surface;

[0044] The step S340 is a preliminary forming process for the connecting end of another metal component. The forming process is the same as that in the step S320 and will not be described in detail here.

[0045] S360: Connecting the two metal components by laser melting the contact plane and the planar boss.

[0046] Specifically, as an example, after completing the additive manufacturing forming process of the connecting ends of two metal components to be connected, the corresponding discrete slice data of the metal CAD solid model is obtained, and then, driven by a computer numerical control system, the metal material is laser melted and rapidly solidified and deposited layer by layer to directly prepare and form high-performance "near-net-shape" metal parts with rapid solidification organizational characteristics.

[0047] exist Figure 4 In the embodiment shown, a new "X"-shaped forming process is used for connection, the opening angle is 45°, a boss of a certain width is reserved on one side of the connection position, and the height of the boss (Z direction) is ≤5mm (to ensure that the boss can be completely melted in the Z direction without penetration), and the other connection position is a platform. The connection area is a planar contact, and the connection is formed in the forward and reverse directions.

[0048] exist Figure 5 In the embodiment shown, a "V"-shaped forming process is used for connection. The opening angle is 45°, a boss of a certain width is reserved on one side of the connection position, and the boss height (Z direction) is ≤5mm (to ensure that the boss can be completely melted in the Z direction without penetration). The other side of the connection is a platform, the connection area is a planar contact, and the connection is formed in the Z direction without the need for reversing.

[0049] Compared with the traditional method, the connection method of laser melting deposition structural parts provided by the present invention is to prefabricate a 45° bevel on one of the metal components and process a ≤5mm contact plane at the connection, and prefabricate a 45° bevel on the other metal component and reserve a ≤5×5mm (length×height) flat small boss at the connection; the new design of "reserved plane and boss" makes the connection area of ​​the two connectors change from "line contact" to "surface contact", increases the stability of positioning, reduces the difficulty of positioning to a certain extent, and controls the deformation caused by rotation in the Z direction. In addition, the smaller boss thickness design can ensure that the boss area is completely melted and connected with another component, so as to achieve good metallurgical bonding, ensure that the bonding area is dense and the performance is qualified, and select "X"-shaped connection or "V"-shaped connection according to the specific structure of the large component, and the "X"-shaped connection needs to be connected and formed in a reverse direction.

[0050] Specifically, as an example, in the process of connecting the contact plane and the planar boss by laser melting, a preset gap (for example, 1 mm to 2 mm) can be reserved at the interface position of the contact plane and the planar boss for laser melting operation.

[0051] In a specific embodiment of the present invention, connecting the two metal components by laser melting the contact plane and the planar boss may include:

[0052] S361: Single-sided additive manufacturing forming, used to fix the two metal components through a preset laser additive connection tooling, so that the contact plane and the plane boss are butted; and then laser melting connection is performed at the connection of the two fixed metal components;

[0053] S362: stress relief annealing treatment, used to perform local stress relief annealing treatment on the laser melting connection position;

[0054] S363: shape correction annealing treatment, used to perform shape correction annealing treatment on the two metal components after the stress relief annealing treatment;

[0055] S364: Semi-finishing, used to grind and clean the laser melting connection position of two metal components after shape correction and annealing.

[0056] Furthermore, after grinding and cleaning the laser melting connection positions of the two metal components after the shaping and annealing treatments, the laser melting connection positions of the two metal components can be further ultrasonically inspected to detect the connection conditions of the laser melting connection positions of the two metal components.

[0057] Among them, the local stress relief annealing treatment can be carried out at a temperature range of 550-850°C, a holding time of 2.5-5.5h, and cooling with the furnace.

[0058] Among them, the local heat treatment furnace can be in the form of a tubular furnace with two sides open. During the heat treatment, the additive manufacturing connection area of ​​the ultra-large metal structure completed by laser additive connection is placed inside the tubular furnace, and other areas outside the connection area are placed outside the furnace, and other areas are cooled by water to minimize the impact of the heat treatment temperature of the connection area on the overall frame.

[0059] In order to improve the compactness of laser melting deposition, during the laser additive process, the laser beam and powder swing forward synchronously in the X-shaped gap. At the additive contact surface of the two metal components, a bidirectional scanning mode (i.e., a zigzag scanning connected end to end) can be adopted. The bidirectional scanning mode has smaller thermal deformation to ensure a lower degree of thermal stress in the sample. At the same time, the next layer is scanned along the scanning path of the previous layer, thereby ensuring that every position of the additive contact surface of the two metal components can be fully scanned.

[0060] It can be seen from the above embodiments that the laser melting deposition structural component connection method provided by the present invention has the following advantages:

[0061] 1. The present invention adopts a boss design with a certain width reserved on one side, and the connection area of ​​the two connectors is in plane contact, which effectively avoids or reduces the light leakage problem and improves energy utilization; the boss height (Z direction) is ≤5mm, which ensures that the laser energy effectively melts the connection area, forms a good metallurgical bond, reduces defects in the connection area, and ensures the performance of the bonding area;

[0062] 2. The present invention adopts a connection process with a boss of a certain width, and the connection area adopts a plane contact, so that the two connecting parts are accurately positioned during the connection process, and the problem of height misalignment of the two connecting parts is avoided to a certain extent, and the flatness of the connecting parts is better controlled, so that the formed parts can maintain the flatness of the qualified state, and at the same time, the deformation in the Z direction can be reduced;

[0063] 3. The present invention adopts a connection process with a boss of a certain width, and the two connecting parts adopt a plane contact, which effectively avoids the problem of connection failure;

[0064] 4. The present invention adopts a process of contact between bosses of a certain width, which effectively shortens the assembly time and improves the assembly efficiency compared to line contact with sharp bevels. Due to the flatness requirement, line contact assembly is more difficult to position than surface contact assembly and is relatively time-consuming. Taking a certain integral frame part as an example, after practice and measurement, the assembly time using line contact is 4 hours (scanning and comparison are required after assembly, and the scanning time is 0.5 hours. The tooling and parts are adjusted according to the comparison results to ensure the flatness, and the scan, comparison and adjustment are performed again until the flatness meets the connection forming requirements). The assembly time using surface contact is shortened to 2.5 hours, and assembling an integral frame part can save 1.5 hours, and the assembly efficiency is improved by 66.7%;

[0065] 5. The present invention adopts a process of boss surface contact with a certain width, and its flatness during assembly and forming is better than that of line contact, and its deformation control is better than that of line contact process. Taking a certain integral frame part as an example, after practice and measurement, when line contact is used for assembly, the flatness after one assembly is usually ≥3mm, and the flatness pass rate of one assembly is 10%; after surface contact is used, the flatness pass rate of one assembly is 100%. After forming and connecting, the warping deformation of the part using the line contact process is ≥8mm, while the warping deformation of the part using the surface contact process can be controlled within 5mm. The use of surface contact can effectively control the deformation of parts during assembly and after forming;

[0066] 6. The present invention designs two connection forming processes of "X" shape and "V" shape, which can meet the connection forming of most laser rapid forming parts;

[0067] 7. The "V"-shaped connection process design of the present invention effectively solves the problem that closed cavity-type structural parts cannot be reversely formed.

[0068] As described above, the method for connecting laser melting deposition structures according to the present invention is described by way of example with reference to the accompanying drawings. However, those skilled in the art should understand that various improvements can be made to the method for connecting laser melting deposition structures proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. A method for connecting two metal components by laser melting deposition, characterized in that: The connection method includes: A 45° bevel is prefabricated at the connection end of one of the metal components, and a contact plane is machined at the top connection of the bevel; A 45° inclined surface is prefabricated at the connection end of another metal component, and a plane boss corresponding to the contact plane is reserved at the top connection of the inclined surface; The two metal components are connected by laser melting the contact plane and the plane boss.

2. The method for connecting laser melting deposition structures according to claim 1, characterized in that: The two metal components are connected in an "X" shape or a "V" shape at the connecting ends.

3. The method for connecting laser melting deposition structures according to claim 2, characterized in that: In the process of connecting the contact plane and the planar boss by laser melting, a preset gap is reserved at the interface position of the contact plane and the planar boss for laser melting operation.

4. The method for connecting laser melting deposition structures according to claim 3, characterized in that: The height of the contact plane is not greater than 5 mm, and the height of the planar boss in the Z direction is not greater than 5 mm.

5. The method for connecting laser melting deposition structures according to claim 3, characterized in that: The thickness of the planar boss is not greater than 5 mm.

6. The method for connecting laser melting deposition structures according to claim 2, wherein: Two metal components connected in an "X" shape are connected in reverse direction to form a connection; The two metal components connected in a "V" shape are connected in the Z direction.

7. The method for connecting laser melting deposition structures according to any one of claims 1 to 5, characterized in that: Prefabricate the 45° bevel at the connection end, including: Prepare a 45° chamfer at the connection end of the metal component by machining; This bevel and surrounding area are ground with a rotary file tool; Clean the polished bevel surface.

8. The method for connecting laser melting deposition structures according to claim 7, characterized in that: The cleaning of the polished bevel surface comprises: First wash with clean water, then with anhydrous ethanol, then with anhydrous acetone, and finally with clean water.

9. The method for connecting laser melting deposition structures according to claim 8, characterized in that: The two metal components are connected by laser melting the contact plane and the planar boss, comprising: Single-sided additive manufacturing is used to fix the two metal components by a preset laser additive connection tool so that the contact plane and the plane boss are butted; then laser melting connection is performed at the connection of the two fixed metal components; Stress relief annealing treatment is used to perform local stress relief annealing treatment on the laser melting connection position; Shape correction annealing treatment is used to perform shape correction annealing treatment on two metal components after stress relief annealing treatment; Semi-finishing is used to grind and clean the laser-melted connection position of two metal components after shape correction and annealing.

10. The method for connecting laser melting deposition structures according to claim 9, characterized in that: After the laser melting connection positions of the two metal components after the shape correction and annealing treatment are polished and cleaned, ultrasonic testing is also included to detect the connection status of the laser melting connection positions of the two metal components.

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