An additive method for achieving ultra-wide and ultra-thin welds using a plasma arc and dual laser composite heat source

Abstract

The present invention is an additive method for achieving ultra-wide and ultra-thin welds using a plasma arc and dual-laser composite heat source. The method is as follows: a suitable substrate is selected and the surface of the substrate is polished. The substrate is preheated to a predetermined temperature; the current of the plasma arc equipment is adjusted, and the wire feeding speed and welding speed parameters are selected; the relative positions of the arc welding gun and the laser output head are adjusted, and the collaborative working mode of the arc current pulse and the laser pulse is set. Two symmetrical time-sharing scanning laser heat sources are added behind the molten pool, and a horizontal transverse scanning laser heat source is added to the tail. The laser emits a laser beam with specific parameters, and at the same time, the arc is struck to start the arc, the metal wire starts to be fed, and the forming and manufacturing process begins until completion. The present invention uses two different heat sources, arc and laser, in the additive process. By controlling the energy of the three heat sources separately, high deposition efficiency can be achieved while also finely controlling the shape of the weld.

Description

Technical Field

[0001] The present invention belongs to the technical field of three-dimensional forming and manufacturing, and in particular relates to an additive manufacturing method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual-laser composite heat source. Background Art

[0002] Modern additive manufacturing (3D printing) technology is based on computer-aided design, material processing, and forming. Using software and numerical control systems, it builds specialized metal and non-metallic materials layer by layer, ultimately creating physical products with superior structural properties. It is hailed as a potential catalyst for the "Third Industrial Revolution." In just a few decades, this technology has achieved rapid development, with promising applications in a wide range of fields, including aerospace, microstructure manufacturing, and biomedical engineering. The technical foundation of additive manufacturing for metal components is welding / joining. Over the past 20 years, additive manufacturing has achieved two major breakthroughs both domestically and internationally: the first is the evolution from early laser rapid prototyping of non-metallic materials such as photosensitive resins to the fabrication of metal structural components; the second is the deep integration of flexible welding and forming technologies using high-energy beam heat sources such as lasers, electron beams, and arcs with computer-aided design / manufacturing information technology, enabling customized, moldless manufacturing of metal structures and establishing a new direction for industrial development.

[0003] The advantages of additive manufacturing lie in its short manufacturing cycles, suitability for individualized individual parts, ability to manufacture large, thin-walled parts, difficult-to-machine, easily thermoformed parts like titanium alloys, and complex structural parts. It offers broad potential for development in fields such as aerospace and mechanical manufacturing, during product development, in the development of computer peripherals, and in innovative education. Currently, additive manufacturing technology complements traditional mass production techniques, but it faces many new challenges and challenges compared to traditional manufacturing technologies. The application of additive manufacturing of metal components in product development still presents challenges such as high costs, low manufacturing efficiency, and unsatisfactory precision. Furthermore, the development of its processes and equipment is insufficient, and it has yet to enter large-scale industrial application.

[0004] Arc additive manufacturing offers advantages such as low cost, high efficiency, a wide range of controllable parameters, excellent mechanical properties, and wide applicability of metal materials. However, there are also challenges that need to be addressed: forming accuracy differs significantly from net-shape parts, residual stresses are high, and the controllability of the molten pool is poor. Among traditional welding technologies, gas metal arc welding offers advantages such as high welding current and high efficiency, but the arc is unstable, and the molten pool is prone to overflow and collapse during the forming process. Gas non-metal arc welding offers stable welding, but the welding current is low and the welding efficiency is low.

[0005] Arc processing in additive manufacturing offers advantages such as high thermal efficiency and droplet deposition rates. However, the high heat input of the arc can easily lead to coarsening of the grain structure within the metal structure. The open, gas-shielded arc environment also makes it easy for porosity defects to form during the forming process. Summary of the Invention

[0006] The purpose of the present invention is to provide an additive method for achieving ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source. The method can widen the weld bead, reduce the weld bead excess height, greatly improve the structural density, increase the heterogeneous nucleation rate at the tail of the molten pool, promote uniform nucleation, and significantly refine the grain growth during the molten pool solidification process.

[0007] The present invention utilizes a plasma arc and dual laser composite heat source to achieve ultra-wide and ultra-thin welds. The arc heat source provides the primary energy required to melt the metal wire, form droplets, and shape the metal structure. High-frequency pulsed laser energy oscillates the molten pool, widening the molten pool and, consequently, the weld bead. The method includes the following steps:

[0008] Step 1: Use titanium alloy as the substrate and use a grinding wheel to grind the area on the substrate where the material needs to be added for a period of time to remove some stains on the surface and scrub with acetone or alcohol to remove the oxide layer; then preheat the substrate so that the overall temperature of the substrate reaches the predetermined temperature evenly;

[0009] Step 2: Adjust the power and scanning mode of the two lasers, the current and voltage of the plasma arc additive equipment, and select parameters such as laser output power, shielding gas type and flow rate, wire feeding method and speed, and welding speed;

[0010] Step 3: Adjust the relative positions of the arc welding gun and the laser output head, and set the coordinated working mode of the arc current pulse and the laser pulse. Add two symmetrical time-sharing scanning laser heat sources behind the molten pool, and add a transverse scanning laser heat source to the tail of the two time-sharing scanning lasers. The two symmetrical laser scanning heat sources are contained within the arc molten pool, and at the left and right edges of the tail of the molten pool, the width of the two laser heat sources should be smaller than the width of the arc molten pool. The rearmost transverse scanning laser should be below the time-sharing scanning laser and span the entire width of the widened molten pool.

[0011] Step 4: Argon gas is supplied to prevent air contact during the entire additive process. The plasma arc additive manufacturing process is started, the laser is activated, and a laser beam with specific parameters is emitted. At the same time, the arc is struck to start the arc and the metal wire is fed, forming a molten pool of a certain width. The width of the arc molten pool is 4mm≤B1 / 2≤5mm, and the width of the molten pool after the composite laser is 8mm≤B2 / 2≤11mm.

[0012] Step 5: The entire additive equipment continues to advance along the predetermined route until a complete weld is formed.

[0013] Step 6: Repeat step 5 until the entire component is formed;

[0014] Step 7: heat-treating the component after material addition in an argon protective atmosphere.

[0015] Furthermore, the preheating treatment of the substrate in step 1 and step 7 is specifically the following process:

[0016] Before starting the additive process, preheat the substrate to 200-300°C within 30 minutes and keep it warm for 5-10 minutes before adding the additive.

[0017] During the additive manufacturing process, in order to improve the mechanical properties of the component and reduce the problem of heat accumulation caused by continuous heat input, which can lead to the formation of coarse columnar crystals, a coolant circulation system is added under the substrate to assist in heat dissipation.

[0018] After the addition is completed, the substrate temperature is adjusted to 100-200°C and maintained for 30-50 minutes before stopping to eliminate residual stress.

[0019] Furthermore, in step 2, in order to achieve the addition of welding wires of different diameters, the parameters of the plasma arc include the plasma arc output power Q

[0020] Q=U·I

[0021] The voltage is 20V≤U≤22.5V, which is the continuously output AC arc voltage; the current is 60A≤I≤200A, which is the continuously output DC arc current or AC arc current;

[0022] Wire feeding speed 3.0m / min≤WFS≤4.0m / min, wire feeding mode is coaxial wire feeding or side-axis wire feeding; welding speed 6mm / s≤TS≤8mm / s; two laser output powers 1200W<P<4500W; plasma arc diameter 8mm≤D≤11mm.

[0023] The deposition rate R is an effective index reflecting the forming efficiency. The larger the deposition rate, the higher the efficiency.

[0024] R=πd·V W ρ / 4

[0025] Where d is the diameter of the welding wire, V Wis the wire feed speed, and ρ is the density of the wire. The formula shows that for a given wire material, the deposition rate depends on the wire feed speed, which must be matched to the heat source energy to ensure timely melting of the wire. Multiple heat sources can increase the wire feed speed, thereby improving the additive efficiency.

[0026] Furthermore, in step 3, the relative positions of the arc welding gun and the time-sharing scanning laser output head are adjusted so that the arc output direction is distributed along the plumb line, the angle between the time-sharing scanning laser output direction and the arc output direction is 0 to 5°, and the angle between the tail transverse scanning laser output direction and the arc output direction is 10 to 15°. With the forward direction of the workbench as a reference, the arc heat source action point is in front, the time-sharing scanning laser output action point is in the middle, and the tail transverse scanning laser is in the back, so that the laser energy acts on the tail area of ​​the arc molten pool.

[0027] Furthermore, in step 3, adjust the arc spacing (H), which is the distance between the arc melting wire and the time-sharing scanning laser beam. If the distance is too large, two heat sources will form, potentially resulting in a weld bead with defects such as a broken weld bead or internal cracks and voids. A smaller distance can lead to collision between the laser head and the arc welding gun, resulting in excessive energy pool overlap and weakening the weld bead expansion effect. The distance between the two is: molten pool length L ≤ H ≤ 4L / 5 + laser scanning length M / 2, 12mm ≤ L ≤ 15mm, 8mm ≤ M ≤ 10mm, so 12.00mm ≤ H ≤ 17.00mm.

[0028] Furthermore, in step 3, the positions of the time-sharing scanning laser and the tail transverse scanning are adjusted to ensure that the tail transverse scanning area is included in the time-sharing scanning tail area to prevent the weld bead from being disconnected due to the long distance between the two heat sources; at the same time, the distance cannot be too far to ensure the maximum transverse scanning area; the distance between the time-sharing scanning laser and the tail transverse scanning laser is denoted as P, and the width of the tail transverse scanning area is denoted as B3, then 3mm≤B3≤4.00mm; 1mm≤P≤2mm.

[0029] Furthermore, in step 3, two symmetrical laser beams are positioned on either side of the rear of the molten pool, with the molten pool as the axis of symmetry. The distance S between the two laser beams must ensure that the laser heat source can reach the edge of the molten pool while also achieving the maximum molten pool widening effect. The distance between the two laser beams is: molten pool width B1 < S < B1 + laser beam d1 / 2 + laser beam d2 / 2.

[0030] Furthermore, in step 3, the diameters d1 and d2 of the two laser beams and the molten pool width B should satisfy the following relationship:

[0031] 0.95<d1 / d2<1.05, 3(d1+d2) / 2≤B1≤2(d1+d2), B1 / 3≤d1(or d2)≤B / 2.

[0032] Furthermore, the action mode of the intermediate laser beam in step 3 is a synchronous time-sharing scanning mode, the pulsed laser beam acts on the molten pool area in a Z-shaped trajectory, and the synchronous time-sharing scanning frequency is proportional to the movement rate of the arc heat source.

[0033] Furthermore, in step 3, the tail laser beam action mode is a transverse mode, the pulsed laser beam acts on the molten pool area in an N-shaped trajectory, and the micro-scanning area is the widened tail of the molten pool. According to the fact that the amount of wire melting is equal to the amount of solidification, the following equation can be derived:

[0034] πd·V W ·ρ / 4=A·V t

[0035] Where A is the cross-sectional surface area of ​​the widened molten pool, V t For a given wire material, the cross-sectional area A of the widened molten pool is proportional to the ratio of the wire feeding speed to the welding speed. A larger cross-sectional area A means a wider weld bead and better results.

[0036] Therefore, the area of ​​the transverse scanning region is ≥ 1 / 3 of the surface area of ​​the widened molten pool to achieve a better effect of widening the molten pool. The transverse scanning frequency is proportional to the synchronous time-sharing scanning frequency.

[0037] The present invention discloses an additive manufacturing method for achieving ultra-wide, ultra-thin welds using a plasma arc and dual-laser composite heat source. The method employs a combined operation mode in which the arc serves as the primary heat source and the pulsed laser serves as the auxiliary heat source, resulting in wider, thinner welds with improved performance and edge quality. The laser plasma generated by the interaction of the pulsed laser with the material suppresses the instability of the pulsed arc. The laser and arc pulses are used to achieve a full fusion of the two energy sources and improve the material's thermal absorption rate of the heat source energy. Heat provided by the pulsed MIG arc is used to melt the automatically and synchronously fed metal wire and form molten droplets, enabling accumulation and forming. The designed pulsed MIG arc pulse pattern achieves relatively low average heat input, reducing internal stress and thermal deformation in the formed component and widening the weld bead. In this technique, while the pulsed laser is not the primary heat source and its frequency needs to be adjusted according to the diameter of the welding wire, the modulation frequency is generally not too high. However, the additional transverse scanning laser at the tail can oscillate the molten pool, resulting in a dense weld bead with a significant grain refinement effect.

[0038] Compared with the prior art, the present invention has the following significant advantages:

[0039] 1. This invention utilizes a plasma arc heat source to provide the primary energy required to melt metal wire, form droplets, and shape the metal structure. Pulsed laser energy simultaneously scans the areas on both sides of the arc molten pool tail and a certain width of the widened tail molten pool laterally, causing the arc molten pool to oscillate at acoustic or ultrasonic frequencies. The molten pool widens in both directions along the symmetrical time-sharing laser scanning area, thereby widening the weld bead. Lateral laser scanning at the tail further reduces the residual height of the widened molten pool and makes the overall level of the molten pool more uniform. This also accelerates gas escape from the molten pool, reduces macro- and micro-porosity, and slightly improves structural density.

[0040] 2. The present invention ensures that the arc is used as a heat source and the laser beam plays the role of oscillating the molten pool by limiting the laser beam parameters and combining the coordinated working mode and energy matching method of the arc current pulse and the laser pulse. When the arc current pulse and the laser pulse are synchronous pulses, the pulse energy peak-to-peak matching will cause the laser pulse to stimulate the generation of an auxiliary vibration energy field in the molten pool while the arc current pulse generates the molten pool, and induce the generation of a pulsating shock wave in the molten pool, affecting the molten pool convection and the nucleation of grains at the solid-liquid interface, accelerating the escape of the gas phase in the molten pool and increasing the nucleation rate. When the arc current pulse and the laser pulse are asynchronous pulses, in addition to the auxiliary vibration energy field of the molten pool generated by the pulse energy peak-to-peak matching, the energy peak-to-base value matching also stimulates the generation of an auxiliary vibration energy field in the molten pool, thereby enhancing the above-mentioned effect on the molten pool.

[0041] 3. The metal deposition rate of the present invention is high, and 5-10 kg of wire can be consumed per hour. The metal component forming efficiency is high, and the internal structure of the metal obtained is dense, and the grains are uniform and fine.

[0042] 4. The arc heat source of the present invention has good stability, and the widening of the weld bead is conducive to heat dissipation, which can achieve low heat input manufacturing and only requires about 80% of the conventional energy, with low energy consumption and manufacturing costs.

[0043] 5. The present invention utilizes two symmetrical laser heat sources to control heat input, resulting in smoother weld edges and higher weld quality. Furthermore, the tail-end horizontal laser scanning further minimizes the difference in horizontal plane between the center and side areas of the weld, reducing weld height. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the additive system using a plasma arc and dual laser composite heat source. 1 is the power supply; 2 is the substrate; 3 is the arc beam; 4 is the molten pool; 5 is the time-sharing scanning laser beam; 6 is the tail transverse scanning laser beam; 7 is the arc additive equipment; 8 is the time-sharing scanning laser; 9 is the tail transverse scanning laser; and 10 is the weld bead.

[0045] Figure 2Schematic diagram of the molten pool morphology and laser path after adding dual lasers.

[0046] Figure 3 Schematic diagram of the waveforms of the arc current pulse and dual laser pulses. The upper part is the arc current pulse, the middle part is the time-sharing scanning laser pulse, and the lower part is the tail transverse scanning laser pulse. DETAILED DESCRIPTION

[0047] The technical method of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0048] Example 1

[0049] To solve the above technical problems, this embodiment provides an additive method using a plasma arc and dual laser composite heat source, including the following steps:

[0050] Step 1: Select titanium alloy as the substrate, and use a grinding wheel to grind the area of ​​the substrate surface where additive manufacturing is required for 3 minutes to remove some stains and oxide layers on the surface; before applying the arc, preheat the substrate to 300°C within 30 minutes, and keep it warm for 10 minutes before additive manufacturing; during the additive manufacturing process, in order to improve the mechanical properties of the component and reduce the problem of heat accumulation caused by continuous heat input and the generation of coarse columnar crystals, a coolant circulation system is added under the substrate to assist in heat dissipation; after the additive manufacturing is completed, the substrate temperature is adjusted to within 180°C and maintained for 30 minutes before stopping.

[0051] The second step is to adjust the power and scanning mode of the two lasers, the current and voltage of the equipment, and select parameters such as arc power, gas type and flow rate, wire feeding method and speed, and welding speed. The plasma arc parameters include voltage U = 22.5V (the voltage is the continuous output AC arc voltage); current I = 160A (the current is the continuous output AC arc current); 1.6mm thick welding wire is selected, wire feed speed WFS = 4.0m / min, wire feeding method is side-axis, and wire feeding is performed simultaneously on both sides. Welding speed TS = 8mm / s; laser output power P = 3600W; arc diameter D = 11mm.

[0052] The third step is to adjust the relative positions of the arc welding gun and the laser output head so that the arc output direction is symmetrically distributed along the plumb line. The angle between the time-sharing scanning laser output direction and the arc output direction is 5°, and the angle between the tail horizontal scanning laser output direction and the arc output direction is 14°. With the forward direction of the workbench as a reference, the arc heat source action point is in the front, the time-sharing scanning laser output action point is in the middle, and the tail horizontal scanning laser output action point is in the rear, so that the two parts of laser energy act on the tail area of ​​the arc molten pool.

[0053] Adjust the filament spacing (H) between the welding wire and the laser beam so that the laser heat source can contact the arc pool without colliding with the laser head. The distance between the two is: pool length L = 15mm, time-sharing laser length M = 10mm, and H = 16.00mm. Two symmetrical laser beams are positioned on either side of the rear of the pool, with the distance between them being S = 16.00mm. The diameters of the two laser beams are d1 = 4.00mm and d2 = 4.00mm.

[0054] The distance between the time-sharing scanning laser and the tail transverse scanning laser is recorded as P, and the width of the tail transverse scanning area is recorded as B3, then B3 = 4.00 mm; P = 1 mm.

[0055] The fourth step is to start the additive manufacturing program. The two lasers work and emit laser beams with specific parameters. At the same time, the arc is struck to start the arc and the metal wire starts to be fed, and the collaborative working mode of the arc current pulse and the laser pulse is set: when the arc current is in non-pulse mode, the laser pulse energy and the arc energy are arbitrarily matched; when the arc current is in pulse mode, the energy matching of the laser pulse and the arc current pulse includes: when the arc current pulse and the laser pulse are synchronous pulses, within one energy matching cycle, the pulse energy matching is peak-peak matching; when the arc current pulse and the laser pulse are asynchronous pulses, the laser pulse frequency is at least 2 times the arc current pulse frequency, within one energy matching cycle, at least one pulse energy matching is peak-peak matching, and the remaining pulse energy matching is peak-base matching to form a molten pool of a certain width; the width of the arc molten pool B1 = 10 mm, and the width of the molten pool after laser recombination is B2 = 22 mm.

[0056] The fifth step is to allow the entire additive equipment to continue adding material along the predetermined route until a complete weld bead is formed;

[0057] Step 6: Repeat the steps in step 5 until the entire component is formed.

[0058] In the seventh step, the material-added components are heat treated in an argon protective atmosphere.

[0059] The components prepared in this example were removed, their surfaces cleaned, and then subjected to mechanical property tests, including tensile testing and hardness testing. The tensile strength and elongation after fracture of the additively manufactured components are shown in Table 1 below.

[0060] Example 2

[0061] To solve the above technical problems, this embodiment provides an additive method using a plasma arc and dual laser composite heat source, including the following steps:

[0062] Step 1: Select titanium alloy as the substrate, and use a grinding wheel to grind the area on the substrate surface where additive manufacturing is required for 3 minutes to remove some stains and oxide layers on the surface; before applying the arc, preheat the substrate to 280°C within 40 minutes, and keep it warm for 8 minutes before additive manufacturing; during the additive manufacturing process, in order to improve the mechanical properties of the component and reduce the problem of heat accumulation caused by continuous heat input and thus the generation of coarse columnar crystals, a coolant circulation system is added under the substrate to assist in heat dissipation; after the additive manufacturing is completed, the substrate temperature is adjusted to within 150°C and maintained for 40 minutes before stopping.

[0063] The second step involves adjusting the power and scanning mode of the two lasers, the current and voltage of the equipment, and selecting parameters such as arc power, gas type and flow rate, wire feeding method and speed, and welding speed. The plasma arc parameters include voltage U = 21V (constant output AC arc voltage); current I = 120A (constant output DC arc current or AC arc current); 1.4mm thick welding wire, wire feed speed WFS = 3.5m / min, side-axis wire feeding, and simultaneous double-sided wire feeding. Welding speed TS = 7mm / s; laser output power P = 2520W; arc diameter D = 10mm.

[0064] The third step is to adjust the relative positions of the arc welding gun and the laser output head so that the arc output direction is symmetrically distributed along the plumb line. The angle between the time-sharing scanning laser output direction and the arc output direction is 4°, and the angle between the tail transverse scanning laser output direction and the arc output direction is 12°. With the forward direction of the workbench as a reference, the arc heat source action point is in the front, the time-sharing scanning laser output action point is in the middle, and the tail transverse scanning laser output action point is in the rear, so that the two parts of laser energy act on the tail area of ​​the arc molten pool.

[0065] Adjust the filament spacing (H) between the welding wire and the laser beam so that the laser heat source can contact the arc pool without colliding with the laser head. The distance between the two is: pool length L = 14mm, M = 9mm, H = 15.00mm. Two symmetrical laser beams are positioned on either side of the rear of the pool, with the distance between them being S = 16.00mm. The diameters of the two laser beams are d1 = 4.00mm and d2 = 4.00mm.

[0066] The distance between the time-sharing scanning laser and the tail transverse scanning laser is recorded as P, and the width of the tail transverse scanning area is recorded as B3, then B3 = 3.50 mm; P = 1.5 mm.

[0067] The fourth step is to start the additive manufacturing program. The two lasers work and emit laser beams with specific parameters. At the same time, the arc is struck to start the arc and the metal wire starts to be fed, and the collaborative working mode of the arc current pulse and the laser pulse is set: when the arc current is in non-pulse mode, the laser pulse energy and the arc energy are arbitrarily matched; when the arc current is in pulse mode, the energy matching of the laser pulse and the arc current pulse includes: when the arc current pulse and the laser pulse are synchronous pulses, within one energy matching cycle, the pulse energy matching is peak-peak matching; when the arc current pulse and the laser pulse are asynchronous pulses, the laser pulse frequency is at least 2 times the arc current pulse frequency, within one energy matching cycle, at least one pulse energy matching is peak-peak matching, and the remaining pulse energy matching is peak-base matching to form a molten pool of a certain width; the width of the arc molten pool is B1 = 9 mm, and the width of the molten pool after laser recombination is B2 = 20 mm.

[0068] The fifth step is to allow the entire additive equipment to continue adding material along the predetermined route until a complete weld bead is formed;

[0069] Step 6: Repeat the steps in step 5 until the entire component is formed.

[0070] In the seventh step, the material-added components are heat treated in an argon protective atmosphere.

[0071] The components prepared in this example were removed, their surfaces cleaned, and then subjected to mechanical property tests, including tensile testing and hardness testing. The tensile strength and elongation after fracture of the additively manufactured components are shown in Table 1 below.

[0072] Example 3

[0073] To solve the above technical problems, this embodiment provides an additive method using a plasma arc and dual laser composite heat source, including the following steps:

[0074] Step 1: Select titanium alloy as the substrate, and use a grinding wheel to grind the area on the substrate surface where additive manufacturing is required for 3 minutes to remove some stains and oxide layers on the surface; before applying the arc, preheat the substrate to 230°C within 30 minutes, and keep it warm for 6 minutes before additive manufacturing; during the additive manufacturing process, in order to improve the mechanical properties of the component and reduce the problem of heat accumulation caused by continuous heat input and the generation of coarse columnar crystals, a coolant circulation system is added under the substrate to assist in heat dissipation; after the additive manufacturing is completed, the substrate temperature is adjusted to within 140°C and maintained for 50 minutes before stopping.

[0075] The second step involves adjusting the power and scanning mode of the two lasers, the current and voltage of the equipment, and selecting parameters such as arc power, gas type and flow rate, wire feeding method and speed, and welding speed. The plasma arc parameters include voltage U = 20V (constant output AC arc voltage); current I = 70A (constant output DC or AC arc current); 1.2mm thick welding wire, wire feed speed WFS = 3.0m / min, side-axis wire feeding, and simultaneous double-sided wire feeding. Welding speed TS = 6mm / s; power P = 1400W; arc diameter D = 9mm.

[0076] The third step is to adjust the relative positions of the arc welding gun and the laser output head so that the arc output direction is symmetrically distributed along the plumb line. The angle between the time-sharing scanning laser output direction and the arc output direction is 3°, and the angle between the tail horizontal scanning laser output direction and the arc output direction is 10°. With the forward direction of the workbench as a reference, the arc heat source action point is in the front, the time-sharing scanning laser output action point is in the middle, and the tail horizontal scanning laser output action point is in the rear, so that the two parts of laser energy act on the tail area of ​​the arc molten pool.

[0077] Adjust the filament spacing (H) between the welding wire and the laser beam so that the laser heat source can contact the arc pool without colliding with the laser head. The distance between the two is: pool length L = 12mm, M = 8mm, H = 14.00mm. Two symmetrical laser beams are positioned on either side of the rear of the pool, with the distance between them being S = 16.00mm. The diameters of the two laser beams are d1 = 4.00mm and d2 = 4.00mm.

[0078] The distance between the time-sharing scanning laser and the tail transverse scanning laser is recorded as P, and the width of the tail transverse scanning area is recorded as B3, then B3 = 3.00 mm; P = 2 mm.

[0079] The fourth step is to start the additive manufacturing program. The two lasers work and emit laser beams with specific parameters. At the same time, the arc is struck to start the arc and the metal wire starts to be fed, and the collaborative working mode of the arc current pulse and the laser pulse is set: when the arc current is in non-pulse mode, the laser pulse energy and the arc energy are arbitrarily matched; when the arc current is in pulse mode, the energy matching of the laser pulse and the arc current pulse includes: when the arc current pulse and the laser pulse are synchronous pulses, within one energy matching cycle, the pulse energy matching is peak-peak matching; when the arc current pulse and the laser pulse are asynchronous pulses, the laser pulse frequency is at least 2 times the arc current pulse frequency, within one energy matching cycle, at least one pulse energy matching is peak-peak matching, and the remaining pulse energy matching is peak-base matching to form a molten pool of a certain width; the width of the arc molten pool is B1 = 8 mm, and the width of the molten pool after laser recombination is B2 = 18 mm.

[0080] The fifth step is to allow the entire additive equipment to continue adding material along the predetermined route until a complete weld bead is formed;

[0081] Step 6: Repeat the steps in step 5 until the entire component is formed.

[0082] In the seventh step, the material-added components are heat treated in an argon protective atmosphere.

[0083] The components prepared in this example were removed, their surfaces cleaned, and then subjected to mechanical property tests, including tensile testing and hardness testing. The tensile strength and elongation after fracture of the additively manufactured components are shown in Table 1 below.

[0084] Table 1

[0085] Tensile strength / MPa Elongation after break / % Hardness / HV Example 1 1595 18.2 312 Example 2 1571 15.6 298 Example 3 1549 13.9 286

Claims

1. A method for achieving ultra-wide and ultra-thin welds using a plasma arc and dual laser composite heat source, characterized in that: The specific steps include: Step 1: Use titanium alloy as the substrate and use a grinding wheel to grind the area on the substrate where the material needs to be added for a period of time to remove some stains on the surface and scrub with acetone or alcohol to remove the oxide layer; then preheat the substrate so that the overall temperature of the substrate reaches the predetermined temperature evenly; Step 2: Adjust the power and scanning mode of the two lasers, the current and voltage of the plasma arc additive equipment, and select the laser output power, shielding gas type and flow rate, wire feeding method and speed, and welding speed parameters; Step 3: Adjust the relative positions of the arc welding gun and the laser output head, and set the coordinated working mode of the arc current pulse and the laser pulse. Add two symmetrical time-sharing scanning laser heat sources behind the molten pool, and add a transverse scanning laser heat source to the tail of the two time-sharing scanning lasers. The two symmetrical laser scanning heat sources are contained within the arc molten pool, and at the left and right edges of the tail of the molten pool, the width of the two laser heat sources should be smaller than the width of the arc molten pool. The rearmost transverse scanning laser should be below the time-sharing scanning laser and span the entire width of the widened molten pool. Step 4: Argon gas is supplied to prevent air contact during the entire additive process. The plasma arc additive manufacturing process is started to operate the laser, emitting a laser beam with specific parameters. The arc is simultaneously struck to start the arc and the metal wire is fed, forming a molten pool of a certain width. The width of the arc molten pool is 4mm≤B1 / 2≤5mm, and the width of the molten pool after the composite laser is 8mm≤B2 / 2≤11mm. Step 5: The entire additive equipment continues to advance along the predetermined route until a complete weld is formed. Step 6: Repeat step 5 until the entire component is formed; Step 7: heat-treating the component after material addition in an argon protective atmosphere.

2. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and laser composite heat source according to claim 1, characterized in that: In step 1 and step 7, the preheating process of the substrate is specifically as follows: Before starting the additive process, preheat the substrate to 200-300°C within 30 minutes and keep it warm for 5-10 minutes before adding the additive. During the additive manufacturing process, in order to improve the mechanical properties of the component and reduce the problem of heat accumulation caused by continuous heat input, which can lead to the formation of coarse columnar crystals, a coolant circulation system is added under the substrate to assist in heat dissipation. After the addition is completed, the substrate temperature is adjusted to the range of 100-200°C and maintained for 30-50 minutes before stopping to eliminate residual stress and further improve the performance of the obtained component.

3. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 2, in order to achieve the addition of welding wires of different diameters, the parameters of the plasma arc include the plasma arc output power Q Q=U·I The voltage is 20V≤U≤22.5V, which is the continuously output AC arc voltage; the current is 60A≤I≤200A, which is the continuously output DC arc current or AC arc current; Wire feeding speed 3.0m / min≤WFS≤4.0m / min, wire feeding mode is coaxial wire feeding or side-axis wire feeding; welding speed 6mm / s≤TS≤8mm / s; two laser output powers 1200W<P<4500W; plasma arc diameter 8mm≤D≤11mm; The deposition rate R is an effective index reflecting the forming efficiency. The larger the deposition rate, the higher the efficiency. R=πd·V W ·r / 4 Where d is the diameter of the welding wire, V W is the wire feeding speed, and ρ is the density of the welding wire. The formula shows that for a given wire material, the deposition rate depends on the wire feeding speed, and the wire feeding speed must match the heat source energy to ensure that the wire material can be melted in time. Multiple heat sources can make the wire feeding speed faster, thereby improving the additive efficiency.

4. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 3, the relative positions of the arc welding gun and the time-sharing scanning laser output head are adjusted so that the arc output direction is distributed along the plumb line, the angle between the time-sharing scanning laser output direction and the arc output direction is 0 to 5°, and the angle between the tail transverse scanning laser output direction and the arc output direction is 10 to 15°. With the forward direction of the workbench as a reference, the arc heat source action point is in front, the time-sharing scanning laser output action point is in the middle, and the tail transverse scanning laser is in the back, so that the laser energy acts on the tail area of ​​the arc molten pool.

5. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 3, adjust the arc spacing, that is, the distance H between the arc melting wire position and the time-sharing scanning laser beam. If the distance between the two is too large, two heat sources will be formed, and the weld formed may have defects such as broken weld beads or cracks and cavities in the middle. If the distance is too small, the laser output head may collide with the arc welding gun and the energy pool may overlap too much, weakening the effect of expanding the weld bead; the distance between the two: the molten pool length L≤H≤4L / 5+laser scanning length M / 2, 12mm≤L≤15mm, 8mm≤M≤10mm, so 12.00mm≤H≤17.00mm.

6. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 3, adjust the positions of the time-sharing scanning laser and the tail transverse scanning to ensure that the tail transverse scanning area is included in the time-sharing scanning tail area to prevent the weld bead from being disconnected due to the long distance between the two heat sources; at the same time, the distance cannot be too far to ensure the maximum transverse scanning area; the distance between the time-sharing scanning laser and the tail transverse scanning laser is recorded as P, and the width of the tail transverse scanning area is recorded as B3, then 3mm≤B3≤4.00mm; 1mm≤P≤2mm.

7. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 3, two symmetrical laser beams are distributed on both sides of the rear of the molten pool with the molten pool as the axis of symmetry. The distance S between the two laser beams must satisfy the requirement that the laser heat source contacts the edge of the molten pool while also achieving the maximum effect of widening the molten pool; the distance between the two laser beams is: the molten pool width B1<S<B1+laser beam d1 / 2+laser beam d2 / 2.

8. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 3, the diameters d1 and d2 of the two laser beams and the molten pool width B should satisfy the following relationship: 0.95<d1 / d2<1.05, 3(d1+d2) / 2≤B1≤2(d1+d2), B1 / 3≤d1, d2≤B / 2.

9. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 3, the action mode of the intermediate laser beam is a synchronous time-sharing scanning mode, the pulsed laser beam acts on the molten pool area in a Z-shaped trajectory, and the synchronous time-sharing scanning frequency is proportional to the movement rate of the arc heat source.

10. The additive method for realizing ultra-wide and ultra-thin welds by using a plasma arc and dual laser composite heat source according to claim 1, characterized in that: In step 3, the tail laser beam action mode is the transverse mode, the pulsed laser beam acts on the molten pool area in an N-shaped trajectory, and the micro-scanning area is the widened tail of the molten pool; based on the fact that the amount of wire melting is equal to the amount of solidification, the following equation is obtained: πd·V W ·ρ / 4=A·V t Where A is the cross-sectional surface area of ​​the widened molten pool, V t is the welding speed. For a given wire material, the cross-sectional surface area A of the widened molten pool is proportional to the ratio of the wire feeding speed to the welding speed. The larger the cross-sectional surface area A, the wider the weld bead and the better the effect. Therefore, the area of ​​the transverse scanning region is ≥ 1 / 3 of the surface area of ​​the widened molten pool to achieve a better effect of widening the molten pool. The transverse scanning frequency is proportional to the synchronous time-sharing scanning frequency.

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