Electric arc additive manufacturing system and method based on discontinuous pulse cold welding

Abstract

The invention provides an electric arc additive manufacturing system and method based on discontinuous pulse cold welding. The system comprises a discontinuous pulse cold welding gun, a wire feeding guide pipe, a wire feeder and a multi-axis motion platform. The discontinuous pulse cold welding gun is connected with a wire feeder based on a wire feeding guide pipe and installed on the multi-axis motion platform. An electric arc welding wire and a discontinuous pulse cold welding gun are sequentially assembled from front to back; a tungsten electrode of the discontinuous pulse cold welding gun is connected with a negative electrode of the cold welding power source, and the titanium alloy welding wire is connected with a positive electrode of the cold welding power source. According to the method, through the discontinuous pulse cold welding technology, the titanium alloy structural part with the fine-grain weak texture characteristic can be formed in the electric arc additive manufacturing process through simple and convenient equipment and structure; the fine-grain weak texture structure can remarkably improve the strength, toughness and fatigue resistance of the titanium alloy, and has important significance in application of high-performance titanium alloy components in the fields of aerospace, weaponry and other major equipment.

Description

Technical Field

[0001] The present invention relates to the field of metal manufacturing methods, and in particular, to an arc additive manufacturing system and method based on discontinuous pulse cold welding, and in particular to an arc additive manufacturing titanium alloy fine-grained weak texture control system and method based on discontinuous pulse cold welding. Background Art

[0002] Arc additive manufacturing uses the electric arc as the energy source. When the parent material is melted, the welding wire raw material is fed simultaneously. The material is deposited layer by layer according to the slice path of the predetermined geometric morphology. Based on the principle of "discrete-accumulation", the additive manufacturing geometry is formed. It has the advantages of low cost, high efficiency and high quality, and has gradually become an important preparation technology in high-tech fields such as aerospace, national defense weapons and equipment. However, the traditional arc heat source is often formed by the discharge arc between the tungsten electrode and the parent material, or between the melting machine welding wire and the parent material. There is inevitably a strong coupling relationship between the size of the arc heat source and the size of the parent material molten pool. The high heat input brought about by this arc additive process will cause the additive manufacturing components to have millimeter-level coarse columnar crystals that span multiple deposition layers. At the same time, the lack of heterogeneous nucleation points and solute elements with strong supercooling ability in the molten pool, as well as the large temperature gradient at the solid / liquid interface front make it more difficult to eliminate the coarse β columnar crystals inside the additive body by conventional means, and form α strong texture characteristics, resulting in "high strength and low plasticity" and anisotropy problems in mechanical properties, which seriously restricts the application of titanium alloy additive manufacturing components in future aerospace vehicles.

[0003] Therefore, achieving effective control of grain refinement and texture weakening has become a hot topic and focus of current titanium alloy arc fuse additive manufacturing. At present, research on titanium alloy grain refinement is mostly focused on external auxiliary process strategies and alloy element control. For example, patent document CN107649682A discloses a method for refining titanium alloy grains by laser additive manufacturing using ultrasonic impact and induction heating. This method increases the thickness of the plastic deformation layer by using induction heating combined with ultrasonic impact, thereby enhancing the refinement and uniformity of titanium alloy grains, improving the mechanical properties of additively manufactured titanium alloys, and reducing anisotropy; however, although this method can refine grains and improve mechanical properties, it requires complex equipment and operating steps, and the parameters of ultrasonic impact and induction heating must be adjusted according to specific circumstances, otherwise it will affect the degree of grain refinement and uniformity. Patent document CN117483786A discloses a method for adding Ni element to refine the grains of titanium alloy in arc additive manufacturing. This method adds a certain amount of Ni element to the molten pool during the arc additive manufacturing process, thereby obtaining a titanium alloy component composed of fine equiaxed crystals and significantly improving the tensile strength and microhardness of the component. However, the disadvantage is that this method is difficult to control the uniform distribution of Ni elements in the component, and it is impossible to determine the optimal Ni addition amount. Therefore, how to achieve grain refinement and texture weakening in the process of titanium alloy arc additive manufacturing through a simple, efficient and low-cost method has become one of the key directions of researchers' attention.

[0004] The cold welding power source is able to accurately release the electric energy stored in the capacitor between the tungsten electrode and the workpiece to be welded in the form of a pulsed arc in a very short time. The extremely high temperature generated by this pulsed arc in a short time can quickly melt the parent material to form a molten pool. Compared with the traditional method, this method has the advantages of small heat input and dispersed thermal stress. However, if the cold welding power source is directly used to perform additive manufacturing by arcing between the tungsten electrode and the parent material, there is still the problem of epitaxial growth of coarse β columnar crystals along the matrix grains. On this basis, if the linear correlation between the heat input of the arc heat source and the remelting depth unique to the additive manufacturing process is changed, the problem of melting the top fine equiaxed crystals caused by excessive remelting depth can be overcome, and it is expected to achieve micro-grain control in the titanium alloy arc additive manufacturing process, overcome the anisotropy and insufficient strength and plasticity caused by traditional coarse columnar crystals, and realize the design and preparation of titanium alloy arc additive manufacturing with controllable grain refinement.

[0005] In summary, the present invention aims to achieve the design and preparation of titanium alloy additive manufacturing components with internal grain refinement and texture weakening regulation. It adopts a non-continuous pulse cold welding method, utilizes pulse discharge between the tungsten electrode and the welding wire, decouples the relationship between energy input and remelting depth, and realizes the organizational regulation of the metallurgical process of arc fuse additive manufacturing titanium alloy, so as to eliminate coarse β columnar crystals and weaken the α strong texture characteristics, laying a theoretical foundation for the integrated forming of fine-grained weak-textured titanium alloy shape control in the aerospace field. Summary of the invention

[0006] In view of the defects in the prior art, the object of the present invention is to provide an arc additive manufacturing method and system based on discontinuous pulse cold welding.

[0007] According to the present invention, an arc additive manufacturing system based on discontinuous pulse cold welding is provided, comprising:

[0008] Discontinuous pulse cold welding gun, wire guide tube, wire feeder and multi-axis motion platform;

[0009] The discontinuous pulse cold welding gun is connected to the wire feeder based on the wire feed guide tube and is installed on a multi-axis motion platform;

[0010] From front to back, tool the arc welding wire and the non-continuous pulse cold welding gun;

[0011] The tungsten electrode of the discontinuous pulse cold welding gun is connected to the negative electrode of the cold welding power supply, and the titanium alloy welding wire is connected to the positive electrode of the cold welding power supply.

[0012] Preferably, the discontinuous pulse cold welding gun is used to release the electric energy stored in the capacitor in the tungsten electrode in the form of a pulse arc between the tungsten electrode and the metal workpiece under a protective atmosphere, so that the metal workpiece and the welding wire are melted to produce a metallurgical bond, and a single-pass single-layer deposition layer is formed by discontinuous pulse deposition.

[0013] Preferably, the arc additive manufacturing component is formed by changing the trajectory of the multi-axis motion platform to perform reciprocating additive manufacturing deposition.

[0014] Preferably, the instantaneous pulse current of the discontinuous pulse cold welding gun is 10-800A, the pulse time is 50-500ms, and the pulse frequency is 1-10Hz.

[0015] Preferably, the tungsten electrode material of the discontinuous pulse cold welding gun comprises a cerium tungsten electrode, the electrode diameter is 1.6-2.4 mm, and the tip of the tungsten electrode is ground into a cone shape of 70-90 degrees.

[0016] Preferably, the materials of the titanium alloy welding wire include Ti, Ti6Al4V, Ti-6.5Al-1.5Zr-3.5Mo-0.3Si and Ti-5Al-2Sn-2Zr-4Mo-4Cr.

[0017] Preferably, the titanium alloy welding wire is connected to the positive electrode of the cold welding power supply in the following ways:

[0018] -The power electrode sheet is made into a roller shape so that the welding wire can be rolled in and the circuit maintains a conductive path;

[0019] -Connect the power supply sheet to the wire guide tube, and the wire guide tube is in contact with the welding wire to keep the circuit conductive;

[0020] -Connect the power electrode sheet to the wire feeder roller to cut off part of the current path between the wire feeder roller and the wire feeder, so that a conductive path is formed between the power electrode sheet and the welding wire.

[0021] Preferably, the discontinuous pulse deposition includes single-pass deposition in a periodic solidification manner using a pulse arc, the pulse frequency is 1-10 Hz, and the wire feeding speed matches the pulse frequency and is 200 mm / min-1500 mm / min.

[0022] Preferably, the multi-axis motion platform has a travel of 500 mm in the X-axis and Y-axis directions, a travel of 400 mm in the Z-axis direction, a travel accuracy of 0.01 mm, and a load-bearing capacity of 20 kg.

[0023] According to the present invention, an arc additive manufacturing method based on discontinuous pulse cold welding is provided, comprising:

[0024] Step S1: assemble the discontinuous pulse cold welding gun, wire feeding guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire is in front and the discontinuous pulse cold welding gun is in the back, and adjust the wire feeding angle so that the welding wire can enter the molten pool;

[0025] Step S2: connecting the tungsten electrode of the discontinuous pulse cold welding gun to the negative electrode of the cold welding power supply, and connecting the titanium alloy welding wire to the positive electrode of the cold welding power supply;

[0026] Step S3: Under a protective atmosphere, the electric energy stored in the capacitor in the tungsten electrode is released between the tungsten electrode and the metal workpiece in the form of a pulse arc, so that the metal workpiece and the welding wire are melted to produce a metallurgical bond, and a single-pass single-layer deposition layer is formed by discontinuous pulse deposition;

[0027] Step S4: repeating step S3, performing reciprocating additive manufacturing deposition by changing the trajectory of the multi-axis motion platform until a predetermined arc additive manufacturing component is formed.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention uses discontinuous pulse cold welding technology to form titanium alloy structural parts with fine-grained weak texture characteristics in the arc additive manufacturing process using simple equipment and structure; this fine-grained weak texture structure can significantly improve the strength, toughness and fatigue resistance of titanium alloys, and is of great significance for the application of high-performance titanium alloy components in major equipment fields such as aerospace, weapon equipment, etc.

[0030] 2. The present invention utilizes discontinuous pulse cold welding technology, which is different from the discharge characteristics between the tungsten electrode and the base material in the traditional TIG welding process. Through the discharge between the tungsten electrode and the welding wire, the decoupling of the heat source energy and the molten pool is achieved. This method overcomes the problems of lack of heterogeneous nucleation points and difficulty in retaining fine grains due to large remelting depth in the traditional titanium alloy arc additive manufacturing process, making the manufacturing process more optimized and improving manufacturing efficiency and material utilization.

[0031] 3. The present invention can control the discharge intensity of the arc and the temperature of the molten pool by adjusting pulse parameters (such as current, discharge time and pulse frequency) and wire feeding speed, thereby reducing the burn-out rate of the titanium alloy during the manufacturing process, helping to maintain the chemical composition and performance stability of the titanium alloy and improving product quality.

[0032] 4. The present invention adopts titanium alloys including Ti, Ti-6Al-4V, TA15, Ti60, etc., which has a wide range of applications; at the same time, it is not only suitable for titanium alloy materials, but also can be applied to other metal materials, and has broad application prospects in the preparation of complex structural parts, repair of damaged components, etc.

[0033] Other beneficial effects of the present invention will be explained in the specific implementation manner through the introduction of specific technical features and technical solutions. Through the introduction of these technical features and technical solutions, those skilled in the art should be able to understand the beneficial technical effects brought about by the technical features and technical solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0035] Figure 1 Schematic diagram of the method for controlling fine-grained weak texture of titanium alloy by arc additive manufacturing based on discontinuous pulse cold welding.

[0036] Figure 2 The longitudinal cross-section grain morphology of the deposited parts under different additive process methods.

[0037] Figure 3 This is the cross-sectional microstructure SEM image of the additively manufactured deposited part under the process conditions of discontinuous pulse cold welding by discharge between the welding wire and the tungsten electrode.

[0038] Figure 4 This is the cross-sectional microstructure SEM image of the additively manufactured deposited part under normal TIG process conditions.

[0039] Figure 5 This is the EBSD image of the additively manufactured deposited part under the process conditions of discontinuous pulse cold welding through discharge between the welding wire and the tungsten electrode.

[0040] Figure 6This is the EBSD image of the deposited part manufactured by additive manufacturing under normal TIG process conditions. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0042] Reference Figure 1 As shown, an arc additive manufacturing method based on discontinuous pulse cold welding comprises:

[0043] Step A, assemble the discontinuous pulse cold welding gun, wire feeding guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire is in front and the discontinuous pulse cold welding gun is in the back, and adjust the wire feeding angle to ensure that the welding wire can smoothly enter the molten pool; the instantaneous pulse current of the discontinuous pulse cold welding is 10-800A, the pulse time is 50-500ms, the pulse frequency is 1-10Hz, and the adjustment range of the wire feeding angle is 0-60°, so as to ensure that the discharge between the tungsten electrode and the welding wire is normally fed into the molten pool.

[0044] Step B, connect the tungsten electrode of the discontinuous pulse cold welding gun to the negative electrode of the cold welding power supply, connect the titanium alloy welding wire to the positive electrode of the cold welding power supply, and provide a basis for arc discharge between the tungsten electrode and the welding wire; the tungsten electrode material is a cerium tungsten electrode with an electrode diameter of 1.6-2.4mm, and the tip of the tungsten electrode is ground into a 70-90° cone. Titanium alloys include Ti, Ti6Al4V, Ti-6.5Al-1.5Zr-3.5Mo-0.3Si, Ti-5Al-2Sn-2Zr-4Mo-4Cr, etc. At the same time, different from the traditional melting and casting processing method, according to the unique non-equilibrium solidification, multi-layer and multi-pass remelting characteristics and intrinsic online in-situ heat treatment in the arc additive manufacturing process, the alloy composition can be appropriately optimized under the consideration of element burnout.

[0045] There are many ways to connect the welding wire to the positive electrode of the cold welding power supply:

[0046] (1) The power electrode sheet is made into a roller shape, which does not affect the rolling feeding of the welding wire and keeps the circuit conductive;

[0047] (2) The power supply sheet is connected to the wire feed tube, and the wire feed tube is in close contact with the welding wire to maintain a conductive path;

[0048] (3) Connect the power electrode sheet to the wire feeder roller and cut off the possible current path between the wire feeder roller and the wire feeder, so that a conductive path is formed between the power electrode sheet and the welding wire.

[0049] In summary, any method of using the arc between the tungsten electrode and the welding wire in the additive manufacturing process to decouple the positive correlation between the heat source energy and the remelting depth, thereby changing the solidification characteristics, can be regarded as the connection method here.

[0050] Step C, under a protective atmosphere, the electric energy stored in the capacitor in the tungsten electrode is instantly released between the tungsten electrode and the workpiece in the form of a pulse arc. The extremely high temperature arc causes the metal workpiece and the welding wire to fuse rapidly, resulting in a metallurgical bond, and a single-pass single-layer deposition layer is formed by discontinuous pulse deposition; the discontinuous pulse deposition uses a pulse arc to perform single-pass deposition in a periodic solidification manner, the pulse frequency is 1-10Hz, and the wire feeding speed matches the pulse frequency, which is 200mm / min-1500mm / min.

[0051] Step D: Repeat the operation of step C, and form an arc additive manufacturing component by changing the trajectory of the multi-axis motion platform to perform reciprocating additive manufacturing deposition. The multi-axis motion platform has an X and Y stroke of 500 mm, a Z stroke of 400 mm, a stroke accuracy of 0.01 mm, and a load-bearing capacity of 20 kg, which can realize real-time control of the additive manufacturing deposition speed.

[0052] The present invention uses discontinuous pulse cold welding technology, which can utilize simple equipment and structure to form titanium alloy structural parts with fine-grained weak texture characteristics during the arc additive manufacturing process; this fine-grained weak texture structure can significantly improve the strength, toughness and fatigue resistance of the titanium alloy, and is of great significance for the application of high-performance titanium alloy components in major equipment fields such as aerospace, weapon equipment, etc.

[0053] Example 1

[0054] This embodiment provides a method for controlling fine grain weak texture of TC4 titanium alloy by arc additive manufacturing based on discontinuous pulse cold welding, comprising the following steps:

[0055] Step 1. Assemble the discontinuous pulse cold welding torch, gas shield, wire guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire and wire guide tube are in front and the discontinuous pulse cold welding torch and gas shield are in the back. Grind the Ti-6Al-4V substrate with 400-grit sandpaper, remove the surface oil with acetone, dry it, and preheat it to 200°C. Set the discontinuous pulse cold welding parameters: the pulse current is 50A, the instantaneous peak current can reach 100A, the pulse time is 70ms, and the wire feeding angle is adjusted to 30° to ensure that the welding wire can smoothly enter the molten pool.

[0056] Step 2. For Ti6Al4V titanium alloy wire with a diameter of 1.2mm, use an aqueous solution of 5% HF+30% HNO3 (volume fraction) to pickle the Ti6Al4V wire; finally, wash it with water to remove the pickling solution and then dry it for use to remove surface oil and oxide film, avoid the introduction of impurities and ensure the conductivity of the welding wire. Connect the negative pole of the cold welding power supply to the tungsten electrode, and connect the positive power supply sheet to the wire feeding tube. Use the wire feeding tube to keep close contact with the welding wire to keep the circuit conductive. The tungsten electrode uses a cerium tungsten electrode, and the tip of the tungsten electrode is ground into a cone angle of 70° to ensure normal pulse discharge. Control the elongation of the welding wire out of the wire guide tube to ensure that the tip of the welding wire is directly below the cerium tungsten electrode and directly above the Ti-6Al-4V substrate. At the same time, adjust the distance between the tip of the welding wire and the tip of the tungsten electrode to 1.5mm to achieve stable pulse discharge between the tungsten electrode and the welding wire to form a molten pool to melt the welding wire deposition. The deposition process is as follows: Figure 1 shown.

[0057] Step 3, move the welding gun to the starting point of the additive path, adjust the cold welding gun shielding gas flow rate and the gas shielding hood gas flow rate to 5L / min and 16L / min respectively, and release the electric energy stored in the capacitor in the tungsten electrode instantly between the tungsten electrode and the welding wire in the form of a pulse arc. The extremely high temperature arc makes the Ti-6Al-4V substrate and the welding wire melt rapidly to produce a metallurgical bond. Adjust the frequency of the discontinuous pulse arc to 2Hz and the welding speed to 2.5mm / s, and form a single-pass single-layer discontinuous pulse deposition layer by discontinuous pulse deposition;

[0058] Step 4: lower the multi-axis walking platform by 0.8 mm to deposit the next layer on the basis of the original deposition layer. Repeat steps 3 and 4 in a cycle until the multi-layer deposited metal reaches the preset shape and size, and obtains a titanium alloy with fine grains and weak texture characteristics. Figure 2 (a) is the grain morphology of the longitudinal section of the deposited part. It can be seen that the grain refinement is obvious and the continuous growth trend of columnar crystals is interrupted. Figure 3 This is the internal organization diagram. It can be seen that the α plate is smaller in size and has a martensite phase formed by rapid cooling. Figure 5 (a) is the EBSD image of the longitudinal section of the deposited part. It can be seen that the grains are obviously refined and the α texture characteristics inside are significantly weakened.

[0059] Example 2

[0060] This embodiment provides a method for controlling fine grain weak texture of Ti-6.5Al-1.5Zr-3.5Mo-0.3Si titanium alloy by arc additive manufacturing based on discontinuous pulse cold welding, comprising the following steps:

[0061] Step 1. Assemble the discontinuous pulse cold welding gun, gas shield, wire guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire and wire guide tube are in front and the discontinuous pulse cold welding gun and gas shield are in the back. Grind the Ti-6.5Al-1.5Zr-3.5Mo-0.3Si substrate with 400-grit sandpaper, remove the surface oil with acetone, dry it, and preheat it to 200°C. Set the discontinuous pulse cold welding parameters: pulse current is 50A, pulse time is 50ms, and adjust the wire feeding angle to 30° to ensure that the welding wire can smoothly enter the molten pool.

[0062] Step 2: For Ti-6.5Al-1.5Zr-3.5Mo-0.3Si titanium alloy wire with a diameter of 1.2mm, use 5% HF + 30% HNO3 aqueous solution (volume fraction) to pickle the Ti-6.5Al-1.5Zr-3.5Mo-0.3Si wire; finally, wash it with water to remove the pickling solution and dry it for use, remove surface oil and oxide film, avoid the introduction of impurities and ensure the conductivity of the welding wire. Connect the negative pole of the cold welding power supply to the tungsten pole, and connect the positive power supply sheet to the wire feeding tube. Use the wire feeding tube to keep close contact with the welding wire to keep the circuit conductive. The tungsten pole uses a cerium tungsten pole, and the tip of the tungsten pole is ground into a 70° cone angle to ensure normal pulse discharge. The extension amount of the welding wire extending out of the wire guide tube is controlled to ensure that the tip of the welding wire is directly below the cerium tungsten electrode and directly above the Ti-6.5Al-1.5Zr-3.5Mo-0.3Si substrate. At the same time, the distance between the tip of the welding wire and the tip of the tungsten electrode is adjusted to 1.5 mm to achieve pulse discharge between the tungsten electrode and the welding wire to form a molten pool to melt the welding wire deposition.

[0063] Step 3, move the welding gun to the starting point of the additive path, adjust the cold welding gun shielding gas flow rate and the gas shielding hood gas flow rate to 5L / min and 16L / min respectively, and release the electric energy stored in the capacitor in the tungsten electrode instantly between the tungsten electrode and the workpiece in the form of a pulse arc. The extremely high temperature arc makes the Ti-6.5Al-1.5Zr-3.5Mo-0.3Si substrate and the welding wire quickly fuse to produce metallurgical bonding. Adjust the frequency of the discontinuous pulse arc to 2Hz and the welding speed to 3mm / s, and form a single-pass single-layer discontinuous pulse deposition layer by discontinuous pulse deposition;

[0064] Step 4: lower the multi-axis walking platform by 0.8 mm to deposit the next layer on the basis of the original deposition layer. Repeat steps 3 and 4 in a cycle until the multi-layer deposited metal reaches the preset shape and size, and obtains an arc additively manufactured titanium alloy component with fine grains and weak texture characteristics.

[0065] Example 3

[0066] This embodiment provides a method for controlling fine grain weak texture of TC4 titanium alloy by arc additive manufacturing based on discontinuous pulse cold welding, comprising the following steps:

[0067] Step 1. Assemble the discontinuous pulse cold welding gun, gas shield, wire guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire and wire guide tube are in front and the discontinuous pulse cold welding gun and gas shield are in the back. Grind the Ti-6Al-4V substrate with 400-grit sandpaper, remove the surface oil with acetone, dry it, and preheat it to 200°C. Set the discontinuous pulse cold welding parameters: pulse current is 100A, pulse time is 50ms, and adjust the wire feeding angle to 30° to ensure that the welding wire can smoothly enter the molten pool.

[0068] Step 2: For Ti6Al4V titanium alloy wire with a diameter of 1.2mm, the Ti6Al4V wire is pickled with an aqueous solution of 5% HF+30% HNO3 (volume fraction); finally, the wire is washed with water to remove the pickling solution and then dried for standby use to remove surface oil and oxide film, avoid the introduction of impurities and ensure the conductivity of the welding wire. The negative electrode of the cold welding power supply is connected to the tungsten electrode, and the positive power supply sheet is connected to the wire feeding guide tube. The wire feeding guide tube is in close contact with the welding wire to keep the circuit conductive. The tungsten electrode uses a cerium tungsten electrode, and the tip of the tungsten electrode is ground into a cone angle of 70° to ensure normal pulse discharge. The elongation of the welding wire extending out of the wire guide tube is controlled to ensure that the tip of the welding wire is located directly below the cerium tungsten electrode and directly above the Ti-6Al-4V substrate. At the same time, the distance between the tip of the welding wire and the tip of the tungsten electrode is regulated to be 1.5mm, so as to achieve pulse discharge between the tungsten electrode and the welding wire to form a molten pool to melt the welding wire deposition.

[0069] Step 3, move the welding gun to the starting point of the additive path, adjust the cold welding gun shielding gas flow rate and the gas shielding hood gas flow rate to 5L / min and 16L / min respectively, and release the electric energy stored in the capacitor in the tungsten electrode instantly between the tungsten electrode and the workpiece in the form of a pulse arc. The extremely high temperature arc quickly fuses the Ti-6Al-4V substrate and the welding wire to produce a metallurgical bond. Adjust the frequency of the discontinuous pulse arc to 5Hz and the welding speed to 3mm / s, and form a single-pass single-layer discontinuous pulse deposition layer by discontinuous pulse deposition;

[0070] Step 4: lower the multi-axis walking platform by 0.6 mm to deposit the next layer on the basis of the original deposition layer. Repeat steps 3 and 4 in a cycle until the multi-layer deposited metal reaches the preset shape and size, and obtains a titanium alloy arc additive manufacturing component with fine grains and weak texture characteristics.

[0071] Example 4

[0072] This embodiment provides a method for controlling fine grain weak texture of TC4 titanium alloy by arc additive manufacturing based on discontinuous pulse cold welding, comprising the following steps:

[0073] Step 1. Assemble the discontinuous pulse cold welding gun, gas shield, wire guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire and wire guide tube are in front and the discontinuous pulse cold welding gun and gas shield are in the back. Grind the Ti-6Al-4V substrate with 400-grit sandpaper, remove the surface oil with acetone, dry it, and preheat it to 200°C. Set the discontinuous pulse cold welding parameters: pulse current is 100A, pulse time is 70ms, and the wire feeding angle is adjusted to 30° to ensure that the welding wire can smoothly enter the molten pool.

[0074] Step 2: For Ti6Al4V titanium alloy wire with a diameter of 2mm, the Ti6Al4V wire is pickled with an aqueous solution of 5% HF+30% HNO3 (volume fraction); finally, the wire is washed with water to remove the pickling solution and then dried for standby use to remove surface oil and oxide film, avoid the introduction of impurities and ensure the conductivity of the welding wire. The negative pole of the cold welding power supply is connected to the tungsten pole, and the positive power supply sheet is connected to the wire feeding tube. The wire feeding tube is in close contact with the welding wire to keep the circuit conductive. The tungsten pole adopts a cerium tungsten pole, and the tip of the tungsten pole is ground into a cone angle of 70° to ensure normal pulse discharge. The elongation of the welding wire extending out of the wire guide tube is controlled to ensure that the tip of the welding wire is located directly below the cerium tungsten pole and directly above the Ti-6Al-4V substrate. At the same time, the distance between the tip of the welding wire and the tip of the tungsten pole is regulated to be 2mm, so as to realize the pulse discharge between the tungsten pole and the welding wire to form a molten pool to melt the welding wire deposition.

[0075] Step 3, move the welding gun to the starting point of the additive path, adjust the cold welding gun shielding gas flow rate and the gas shielding hood gas flow rate to 5L / min and 16L / min respectively, and release the electric energy stored in the capacitor in the tungsten electrode instantly between the tungsten electrode and the workpiece in the form of a pulse arc. The extremely high temperature arc quickly fuses the Ti-6Al-4V substrate and the welding wire to produce a metallurgical bond. Adjust the frequency of the discontinuous pulse arc to 2Hz and the welding speed to 2.5mm / s, and form a single-pass single-layer discontinuous pulse deposition layer by discontinuous pulse deposition;

[0076] Step 4: lower the multi-axis walking platform by 1 mm to deposit the next layer on the basis of the original deposition layer. Repeat steps 3 and 4 in a cycle until the multi-layer deposited metal reaches the preset shape and size, and obtains an arc additively manufactured titanium alloy component with fine grains and weak texture characteristics.

[0077] Example 5

[0078] This embodiment provides a method for controlling fine grain weak texture of Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy by arc additive manufacturing based on discontinuous pulse cold welding, comprising the following steps:

[0079] Step 1. Assemble the discontinuous pulse cold welding torch, gas shield, wire guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire and wire guide tube are in front and the discontinuous pulse cold welding torch and gas shield are in the back. Grind the Ti-5Al-2Sn-2Zr-4Mo-4Cr substrate with 400-grit sandpaper, remove the surface oil with acetone, dry it, and preheat it to 200°C. Set the discontinuous pulse cold welding parameters: the instantaneous pulse current is 100A, the pulse time is 50ms, and the wire feeding angle is adjusted to 30° to ensure that the welding wire can smoothly enter the molten pool.

[0080] Step 2: For Ti-5Al-2Sn-2Zr-4Mo-4Cr titanium alloy wire with a diameter of 0.8mm, use 5% HF+30% HNO3 aqueous solution (volume fraction) to pickle the Ti-5Al-2Sn-2Zr-4Mo-4Cr wire; finally, wash it with water to remove the pickling solution and dry it for standby use to remove surface oil and oxide film, avoid the introduction of impurities and ensure the conductivity of the welding wire. Connect the negative pole of the cold welding power supply to the tungsten pole, and connect the positive power supply sheet to the wire feeding tube. Use the wire feeding tube to keep close contact with the welding wire to keep the circuit conductive. The tungsten pole uses a cerium tungsten pole, and the tip of the tungsten pole is ground into a 70° cone angle to ensure normal pulse discharge. The extension amount of the welding wire extending out of the wire guide tube is controlled to ensure that the tip of the welding wire is directly below the cerium tungsten electrode and directly above the Ti-5Al-2Sn-2Zr-4Mo-4Cr substrate. At the same time, the distance between the tip of the welding wire and the tip of the tungsten electrode is adjusted to 1.5 mm to achieve pulse discharge between the tungsten electrode and the welding wire to form a molten pool to melt the welding wire deposition.

[0081] Step 3, move the welding gun to the starting point of the additive path, adjust the cold welding gun shielding gas flow rate and the gas shielding hood gas flow rate to 5L / min and 16L / min respectively, and release the electric energy stored in the capacitor in the tungsten electrode instantly between the tungsten electrode and the workpiece in the form of a pulse arc. The extremely high temperature arc makes the Ti-5Al-2Sn-2Zr-4Mo-4Cr substrate and the welding wire quickly fuse to produce metallurgical bonding. Adjust the frequency of the discontinuous pulse arc to 5Hz and the welding speed to 4mm / s, and form a single-pass single-layer discontinuous pulse deposition layer by discontinuous pulse deposition;

[0082] Step 4: lower the multi-axis walking platform by 0.6 mm to deposit the next layer on the basis of the original deposition layer. Repeat steps 3 and 4 in a cycle until the multi-layer deposited metal reaches the preset shape and size, and obtains an arc additively manufactured titanium alloy component with fine grains and weak texture characteristics.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 1 is that ordinary TIG arc is used to carry out Ti-6Al-4V additive manufacturing test, and the remaining steps are basically the same as Example 1. The Ti-6Al-4V substrate is polished with 400-mesh sandpaper, and the surface oil is removed with acetone and dried, and then fixed and preheated to 200°C. Set the TIG additive manufacturing parameters: the deposition current is 100A, the welding speed is 3mm / s, and the wire feeding angle is adjusted to 30° to ensure that the welding wire can smoothly enter the molten pool. For Ti6Al4V titanium alloy wire with a diameter of 1.2mm, the Ti6Al4V wire is pickled with an aqueous solution of 5% HF+30% HNO3 (volume fraction); finally, it is uniformly washed with water to remove the pickling solution and then dried for standby use to remove surface oil and oxide film, avoid the introduction of impurities, and ensure the conductivity of the welding wire. The tungsten electrode uses a cerium tungsten electrode, and the tip of the tungsten electrode is ground into a cone angle of 70° to ensure normal discharge and arcing. Move the welding gun to the starting point of the additive path, adjust the TIG welding gun shielding gas flow rate and the gas shielding hood gas flow rate to 12L / min and 16L / min respectively, start the arc by discharging between the tungsten electrode and the workpiece, use the extremely high temperature arc to quickly fuse the Ti-6Al-4V substrate and the welding wire to produce metallurgical bonding, set the wire feeding speed to 15mm / s, and form a single-pass single-layer discontinuous pulse deposition layer by discontinuous pulse deposition; lower the multi-axis walking platform by 0.8mm to deposit the next layer on the basis of the original deposition layer. Repeat steps 3 and 4 until the multi-layer deposited metal reaches the preset shape and size, and the additive manufacturing titanium alloy deposit is obtained. Figure 2 (c) is the grain morphology of the longitudinal section of the deposited part produced by ordinary TIG arc additive manufacturing. It can be seen that the interior is composed of coarse columnar crystals that grow through the deposited layer, and the width of the columnar crystals is 1-2 mm. Figure 3 As the internal organization diagram, it can be found that the α plates are larger in size and form α bundles with similar orientation. Figure 6(a) is the EBSD image of the longitudinal section of the deposited part. The α texture features are obvious and have strong preferential orientation characteristics. At the same time, the original β grains are reconstructed according to the Burgers relationship. It can be seen that the shooting area is inside a β grain. Therefore, when using ordinary TIG arc for Ti-6Al-4V additive manufacturing, due to the lack of heterogeneous nucleation points and large components of supercooled alloy elements in the molten pool, it is easy to form coarse β columnar crystals that grow through the deposited layer in the additive manufacturing deposit body. At the same time, it has strong α texture characteristics, which leads to high strength and low plasticity and anisotropy problems, affecting the further development and application of additive manufacturing integrated titanium alloy structural parts.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 1 is that the Ti-6Al-4V pulse cold welding additive manufacturing test is carried out by connecting the tungsten electrode to the negative electrode and the base material to the positive electrode, and the remaining steps are basically the same as Example 1; in this comparative example, the non-continuous pulse cold welding gun, gas shield, wire feeding duct, wire feeder and multi-axis motion platform are assembled in such a way that the arc welding wire and wire feeding duct are in front and the non-continuous pulse cold welding gun and gas shield are in the back. The Ti-6Al-4V substrate is polished with 400-mesh sandpaper, the surface oil is removed with acetone, and it is dried and fixedly preheated to 200°C. The non-continuous pulse cold welding parameters are set: the pulse current is 50A, the instantaneous peak current can reach 100A, the pulse time is 70ms, and the wire feeding angle is adjusted to 30° to ensure that the welding wire can smoothly enter the molten pool. For Ti6Al4V titanium alloy wire with a diameter of 1.2mm, a 5% HF+30% HNO3 aqueous solution (volume fraction) is used to pickle the Ti6Al4V wire; finally, the wire is washed with water to remove the pickling solution and then dried for standby use to remove surface oil and oxide film, avoid the introduction of impurities and ensure the conductivity of the welding wire. The negative pole of the cold welding power supply is connected to the tungsten pole, and the positive pole is connected to the base material to keep the circuit conductive. The tungsten pole uses a cerium tungsten pole, and the tip of the tungsten pole is ground into a 70° cone angle to ensure normal pulse discharge, so as to achieve stable pulse discharge between the tungsten pole and the substrate to form a molten pool to melt the welding wire deposition. Move the welding gun to the starting point of the additive path, adjust the cold welding gun shielding gas flow rate and the gas shielding hood gas flow rate to 5L / min and 16L / min respectively, and release the electric energy stored in the capacitor in the tungsten electrode instantly between the tungsten electrode and the workpiece in the form of a pulse arc. The extremely high temperature arc causes the Ti-6Al-4V substrate and the welding wire to fuse rapidly, resulting in metallurgical bonding. Adjust the frequency of the discontinuous pulse arc to 2Hz and the welding speed to 3mm / s, and form a single-pass single-layer pulse deposition layer by discontinuous pulse deposition; lower the multi-axis walking platform by 0.8mm to deposit the next layer on the basis of the original deposition layer. Repeat steps 3 and 4 in a loop until the multi-layer deposited metal reaches the preset shape and size, and obtains a titanium alloy additive body with fine grains and weak texture characteristics. Figure 2 (b) is the longitudinal cross-sectional grain morphology of the deposit obtained by additive manufacturing with the tungsten electrode connected to the negative electrode and the base material connected to the positive electrode. The β grains have a partial refinement effect, and the grain size is 0.5mm-1.5mm. Therefore, when the Ti-6Al-4V pulse cold welding additive manufacturing experiment is carried out by connecting the tungsten electrode to the negative electrode and the base material to the positive electrode, although the grains are refined to a certain extent, it is not obvious and cannot block the continuous growth of coarse columnar crystals. There are certain limitations on the weakening and elimination of anisotropy, and it is difficult to achieve the integrated preparation of fine-grained weak texture characteristics of additively manufactured titanium alloy components.

[0087] In summary, the additive manufacturing method provided by the present invention changes the traditional way of arc starting between the tungsten electrode and the base material. The arc is started between the tungsten electrode and the welding wire, and a pulse arc is formed in the form of pulse capacitor energy storage discharge. The target component is additively formed according to the planned path. It can inhibit the coarse columnar crystals that grow epitaxially along the substrate, promote the refinement of β grains and α lamellar structures, and weaken the α texture characteristics. The component undergoes uniform plastic deformation and effectively eliminates the metallurgical defects and anisotropic characteristics of the component, providing a reference method for the integrated preparation of arc-added titanium alloy components with fine grains and weak texture characteristics.

[0088] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0089] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. An arc additive manufacturing system based on discontinuous pulse cold welding, characterized in that: include: Discontinuous pulse cold welding gun, wire guide tube, wire feeder and multi-axis motion platform; The discontinuous pulse cold welding gun is connected to the wire feeder based on the wire feed guide tube and is installed on a multi-axis motion platform; From front to back, install the arc welding wire and the non-continuous pulse cold welding gun; The tungsten electrode of the discontinuous pulse cold welding gun is connected to the negative electrode of the cold welding power supply, and the titanium alloy welding wire is connected to the positive electrode of the cold welding power supply.

2. The arc additive manufacturing system based on discontinuous pulse cold welding according to claim 1 is characterized in that: The discontinuous pulse cold welding gun is used to release the electric energy stored in the capacitor in the tungsten electrode between the tungsten electrode and the metal workpiece in the form of a pulse arc under a protective atmosphere, so that the metal workpiece and the welding wire are melted to produce a metallurgical bond, and a single-pass single-layer deposition layer is formed by discontinuous pulse deposition.

3. The arc additive manufacturing system based on discontinuous pulse cold welding according to claim 2 is characterized in that: The arc additive manufacturing component is formed by changing the trajectory of the multi-axis motion platform to perform reciprocating additive manufacturing deposition.

4. The arc additive manufacturing system based on discontinuous pulse cold welding according to claim 1, characterized in that: The instantaneous pulse current of the discontinuous pulse cold welding gun is 10-800A, the pulse time is 50-500ms, and the pulse frequency is 1-10Hz.

5. The arc additive manufacturing system based on discontinuous pulse cold welding according to claim 4, characterized in that: The tungsten electrode material of the discontinuous pulse cold welding gun includes a cerium tungsten electrode with an electrode diameter of 1.6-2.4 mm, and the tip of the tungsten electrode is ground into a cone shape of 70-90 degrees.

6. The arc additive manufacturing system based on discontinuous pulse cold welding according to claim 1, characterized in that: The materials of the titanium alloy welding wire include Ti, Ti6Al4V, Ti-6.5Al-1.5Zr-3.5Mo-0.3Si and Ti-5Al-2Sn-2Zr-4Mo-4Cr.

7. The arc additive manufacturing system based on discontinuous pulse cold welding according to claim 1, characterized in that: The titanium alloy welding wire is connected to the positive electrode of the cold welding power supply in the following ways: -The power electrode sheet is made into a roller shape so that the welding wire can be rolled in and the circuit maintains a conductive path; -Connect the power supply sheet to the wire guide tube, and the wire guide tube is in contact with the welding wire to keep the circuit conductive; -Connect the power electrode sheet to the wire feeder roller to cut off part of the current path between the wire feeder roller and the wire feeder, so that a conductive path is formed between the power electrode sheet and the welding wire.

8. The arc additive manufacturing system based on discontinuous pulse cold welding according to claim 2, characterized in that: The discontinuous pulse deposition includes single-pass deposition in a periodic solidification manner using a pulse arc, the pulse frequency is 1-10 Hz, and the wire feeding speed matches the pulse frequency and is 200 mm / min-1500 mm / min.

9. The method for controlling fine grain weak texture of titanium alloy by arc additive manufacturing based on discontinuous pulse cold welding according to claim 1, characterized in that: The multi-axis motion platform has a travel of 500 mm in the X-axis and Y-axis directions, a travel of 400 mm in the Z-axis direction, a travel accuracy of 0.01 mm, and a load-bearing capacity of 20 kg.

10. An arc additive manufacturing method based on discontinuous pulse cold welding, based on the arc additive manufacturing system based on discontinuous pulse cold welding according to any one of claims 1 to 9, characterized in that: include: Step S1: assemble the discontinuous pulse cold welding gun, wire feeding guide tube, wire feeder and multi-axis motion platform in such a way that the arc welding wire is in front and the discontinuous pulse cold welding gun is in the back, and adjust the wire feeding angle so that the welding wire can enter the molten pool; Step S2: connecting the tungsten electrode of the discontinuous pulse cold welding gun to the negative electrode of the cold welding power supply, and connecting the titanium alloy welding wire to the positive electrode of the cold welding power supply; Step S3: Under a protective atmosphere, the electric energy stored in the capacitor in the tungsten electrode is released between the tungsten electrode and the metal workpiece in the form of a pulse arc, so that the metal workpiece and the welding wire are melted to produce a metallurgical bond, and a single-pass single-layer deposition layer is formed by discontinuous pulse deposition; Step S4: repeating step S3, performing reciprocating additive manufacturing deposition by changing the trajectory of the multi-axis motion platform until a predetermined arc additive manufacturing component is formed.

Images