A positive and negative pressure pulsed arc welding and additive manufacturing method

Abstract

The application provides a positive and negative pressure pulse arc welding and additive manufacturing method, through current-magnetic field-hollow tungsten electrode-gas collaborative design, negative pressure arc of anti-gravity adsorption effect induced by arc plasma is generated, and time sequence coupling process is formed with positive pressure arc. The core lies in the magnetic control positive and negative pressure arc welding external field collaborative molten pool reconfiguration forming mechanism, that is, through dynamically switching the direction of arc pressure, through regulating the action ratio and alternating frequency of negative pressure and positive pressure arc, the dynamic and thermodynamic state of the molten pool is accurately balanced. Based on the adaptive magnetic field threshold model of current intensity and gas mode, combined with the collaborative control of variable polarity power supply parameters and gas flow rate, the problems of thin plate welding melt-through and thin wall additive melt pool instability are effectively solved. The method can integrate the welding wire, powder or laser composite manufacturing mode, significantly improve the forming precision and performance of complex structure, and provide innovative technical support for high-quality and efficient welding and additive manufacturing.

Description

Technical Field

[0001] This invention relates to the field of welding and additive manufacturing technology, specifically to a positive and negative pressure pulsed arc welding and additive manufacturing method based on the synergistic effect of current-magnetic field-hollow tungsten electrode-gas. In particular, it is a process that utilizes a magnetic field to induce a hollow tungsten electrode arc to generate a negative pressure arc with an anti-gravity adsorption effect, and couples it with a positive pressure arc in a pulse sequence. By dynamically adjusting the stress state of the molten pool, its stability can be achieved. This process is applicable to solving the problem of molten pool instability in high-quality welding of thin plate components and additive manufacturing of thin-walled complex structures. Background Technology

[0002] Arc welding and additive manufacturing technologies are widely used in the joining of thin-plate components and the direct manufacturing of complex metal structures due to their advantages such as high heat input, strong material adaptability, and high forming efficiency. However, during the welding of thin plates and the additive manufacturing of thin-walled complex structures, the molten pool is prone to instability phenomena such as flow, collapse, spatter, and even perforation due to the coupled effects of complex dynamic and thermodynamic factors such as gravity, surface tension, and arc pressure. These phenomena severely damage the weld formation quality and the dimensional accuracy and mechanical properties of the additive components.

[0003] Traditional arc welding processes have significant limitations in controlling molten pool stability: Conventional gas tungsten inert gas (GTAW) relies on downward arc pressure to maintain the molten pool shape, but this pressure easily exacerbates molten pool oscillation and molten metal spatter, especially in thin plates or overhanging positions, leading to molten pool instability. Although pulsed current can be used to adjust the heat input, it is essentially still a unidirectional positive pressure, with limited ability to dynamically control the stress state of the molten pool. Existing magnetic field-assisted arc welding technologies (such as applying external transverse or longitudinal magnetic fields) mainly refine grains or constrain arc morphology by stirring the molten pool. While this can improve the forming to some extent, it fails to fundamentally change the direction of the arc's force on the molten pool (still downward positive pressure), and the dynamic matching mechanism between magnetic field parameters and arc / molten pool state is imperfect, resulting in insufficient targeted solutions to the problem of molten pool instability.

[0004] Chinese patents with application publication numbers CN115007974A and CN114713942A disclose a tungsten inert gas (TIG) welding method and an additive manufacturing method with arc negative pressure constraint. Although the negative pressure arc is formed by reversing the direction of the arc force through an external longitudinal magnetic field, and the adsorption effect on the molten pool is realized in the welding and additive manufacturing process, the above technology still has fundamental limitations: (1) It relies on a continuous unidirectional negative pressure arc and lacks a positive and negative pressure pulse timing coupling mechanism, so it is impossible to dynamically balance the stress state of the molten pool; (2) The magnetic field is only used to induce a static negative pressure effect and is not combined with the hollow tungsten electrode structure and gas co-design, so it is difficult to accurately control the range and intensity of the negative pressure; (3) In thin plate welding and thin-walled complex structure additive manufacturing, unidirectional negative pressure may still cause molten pool oscillation or local collapse, especially for high curvature and overhanging structures, the forming stability control is insufficient; (4) It does not solve the problem of molten pool instability caused by thermal cycle accumulation, and it is difficult to meet the dynamic stability requirements of multi-pass multi-layer additive manufacturing.

[0005] Chinese patent application CN118023712A discloses a negative pressure hollow tungsten electrode arc-laser coaxial composite welding method. Although a negative pressure region (0 to -300 Pa) is formed in the center of the arc by a magnetic field or magnetic field + pumping to reduce the shielding of laser energy by metal vapor and improve the utilization rate of laser energy and weld penetration, the technology still has the following limitations: (1) It only uses unidirectional static negative pressure to assist laser welding and does not design a positive and negative pressure pulse timing coupling mechanism, so it cannot dynamically control the stress state of the molten pool to solve the instability problem; (2) The negative pressure effect focuses on reducing the shielding effect of metal vapor and does not involve the dynamic control of the molten pool, especially for the instability phenomena such as molten pool flow and collapse in thin plate / thin wall additive manufacturing, there is no targeted solution; (3) Although a hollow tungsten electrode structure is adopted, the magnetic field-hollow tungsten electrode-gas flow collaborative design is not realized, making it difficult to accurately control the range and intensity of the negative pressure effect; (4) It does not solve the problem of molten pool oscillation caused by thermal cycle accumulation, and its stability is insufficient in multi-pass multi-layer additive manufacturing.

[0006] US Patent Application Publication No. US2016 / 0067811A1 discloses a central negative pressure arc welding device and method. Although the device forms a relatively low pressure zone in the center region of the electrode, the overall direction of its core arc force is still downward (positive pressure). The so-called "negative pressure" is a relative concept that the pressure in a local area is lower than that in the surrounding environment. It does not form a true negative pressure with an anti-gravity adsorption effect and cannot actively stabilize the molten pool through upward adsorption force.

[0007] Liu, Mingxu. Numerical Simulation of Droplet Transfer in Short-Circuit Arc under Magnetic Field, 2015. This paper studies the influence of magnetic field on droplet transfer, optimizing droplet behavior by generating an upward electromagnetic force component through the magnetic field. However, the arc itself and its force on the molten pool are still mainly downward (positive pressure). The upward component generated by the magnetic field is mainly used for droplet detachment, rather than for controlling the dynamic stability of the molten pool as a whole. Moreover, its research background is droplet transfer rather than molten pool instability.

[0008] In existing technologies, conventional electric arc processes and magnetic field-assisted methods cannot achieve active, dynamic, and bidirectional control of the stress state of the molten pool. Their fundamental deficiency lies in the lack of a mechanism to generate an adsorption-type negative pressure arc opposite to the direction of gravity, and the failure to achieve temporal coupling of negative and positive pressure arcs to dynamically balance the combined force of the molten pool. The "positive and negative pressure pulsed arc welding and additive manufacturing method" proposed in this invention overcomes this technical bottleneck through a collaborative design of current-magnetic field-hollow tungsten electrode-gas. A negative pressure arc refers to an arc force vector pointing upwards, forming an adsorption force on the molten pool in the opposite direction of gravity, rather than being below vacuum. The core of positive and negative pressure pulses lies in the periodic switching of the arc pressure direction over time; its essence is the temporal alternation of the arc force vector direction, which is fundamentally different from traditional current pulses.

[0009] To address the long-standing technical bottlenecks and shortcomings of existing methods, this invention proposes a positive and negative pressure pulsed arc welding and additive manufacturing method based on a synergistic design of current-magnetic field-hollow tungsten electrode-gas. The core of this method lies in: utilizing a specifically configured longitudinal magnetic field to dynamically induce a hollow tungsten electrode arc plasma to generate a truly negative pressure arc with anti-gravity and strong adsorption effects, and precisely timing its pulsed coupling with a positive pressure arc (a conventional positive pressure arc, a magnetic field-induced positive pressure arc, or a positive pressure arc with a synergistic magnetic field-gas supply effect). Through this innovative timing coupling process, dynamic and precise control of the positive and negative pressures on the molten pool is achieved, effectively balancing the kinetic and thermodynamic states of the molten pool. This completely solves the instability problems such as weld penetration and flow in thin-plate welding, and molten pool collapse and poor forming in the additive manufacturing of thin-walled complex structures, ensuring high-quality and high-precision forming properties. Summary of the Invention

[0010] The purpose of this invention is to overcome the defects of the prior art and provide a positive and negative pressure pulsed arc welding and additive manufacturing method. It utilizes the synergistic design of current-magnetic field-hollow tungsten electrode-gas to induce the generation of a negative pressure arc with an anti-gravity adsorption effect. Through the pulse timing coupling process of the positive and negative pressure arc, the dynamics and thermodynamic state of the molten pool are dynamically controlled, which completely solves the problem of molten pool instability in thin plate welding and additive manufacturing of thin-walled complex structures, and ensures high-precision, high-performance, and high-quality formability of components.

[0011] The above objectives are achieved through the following technical solutions:

[0012] This invention relates to a method for positive and negative voltage pulsed arc welding and additive manufacturing, comprising the following steps:

[0013] Step 1: Fix the workpiece or additive manufacturing component on the platform, and fix the workpiece to be welded or the additive manufacturing substrate on the operating platform to ensure that the working surface is flat and stable.

[0014] Step 2: Set the hollow tungsten electrode structure parameters: outer diameter 1.6~8mm, inner diameter 0.4~4mm; select the gas flow mode (gas supply, gas extraction, or natural flow) according to process requirements;

[0015] Step 3: Set up a variable polarity or pulsed arc power supply. Connect one end of the arc power supply to the hollow tungsten electrode and the other end to the workpiece to achieve variable polarity or pulsed hollow tungsten electrode arc welding or additive manufacturing. According to the material, structure and process requirements, adjust the electrode positive connection (EP) or pulse current duty cycle, welding current amplitude and frequency, and the direction and magnitude of gas flow inside the hollow tungsten electrode to coordinate and adapt to form an arc welding and additive manufacturing process with alternating negative and positive arc pressure.

[0016] Step 4: Set key process parameters, including arc parameters and magnetic field parameters. The arc current is 60-560A, the welding speed is 0.08-50cm / s, the duty cycle of the positive electrode (EP) state is 10%-30%, the outer diameter of the hollow tungsten electrode is 1.6-8mm, the inner diameter of the hollow tungsten electrode is 0.4-4mm, the magnetic field strength is 0.025-0.08T, the gas flow velocity inside the hollow tungsten electrode is 0-10m / s, and the threshold of the negative pressure arc magnetic field is greater than 0.022T.

[0017] Step 5: Turn on the hollow tungsten electrode arc power supply and external magnetic field excitation equipment to form a hollow tungsten electrode negative pressure arc for welding or additive manufacturing.

[0018] Furthermore, the negative pressure formed at the center of the electric arc is -12 to -680 Pa, the diameter of the negative pressure arc-affected area is 1.2 to 38 mm, and the arc length is 1 to 10 mm;

[0019] Furthermore, the proportion of the negative pressure arc, which alternates between negative and positive pressure, is 5% to 80%, and the low frequency of the positive and negative pressure pulses is 1 to 100 Hz, the medium frequency is 0.5 to 2 kHz, and the high frequency is 10 to 30 kHz.

[0020] Furthermore, the positive and negative voltage pulsed arc welding and additive manufacturing method is characterized in that the magnetic field threshold for forming the negative voltage arc is as follows:

[0021] Method 1: Under the natural state of the hollow tungsten electrode, i.e., without gas supply or extraction, the negative pressure arc magnetic field threshold and the arc current satisfy the following functional relationship.

[0022] B(I) = 0.15 - 3.87 × 10 -3 ·I+4.45×10 -5 ·I 2 -2.23×10 -7 ·I 3 +4.17×10 -10 ·I 4

[0023] In Method 2, under the hollow tungsten electrode pumping method, the negative pressure arc magnetic field threshold and the pumping pressure satisfy the following functional relationship:

[0024] B(p) = 0.04 - 0.02 × exp(p / 9.18)

[0025] In Method 3, under the hollow tungsten electrode gas supply method, the negative pressure arc magnetic field threshold and the arc current satisfy the following functional relationship:

[0026] B(I) = 0.0588 - 8.348 × 10 -4 ·I+6.714×10 -6 ·I 2 -1.667×10 -8 ·I 3

[0027] In the formula: B represents the magnetic field threshold, in Tesla (T), I represents the arc current, in Ampere (A), and p is the pumping pressure, in Pascal (Pa).

[0028] Furthermore, in the positive and negative pressure pulsed arc welding and additive manufacturing method, the negative pressure magnitude, range, and duration of the hollow tungsten electrode negative pressure arc can be flexibly adjusted by changing the magnetic field strength and frequency, the gas supply method and flow rate of the hollow tungsten electrode, and the magnitude and duration of the arc current. The hollow tungsten electrode negative pressure arc and the positive pressure arc work together to ensure the shape and properties of complex structures in welding or additive manufacturing in real time.

[0029] Furthermore, the hollow tungsten electrode, arc power supply, and magnetic field parameters are adapted to different material properties:

[0030] (1) Q235 steel welding: hollow tungsten electrode with outer diameter 2mm and inner diameter 0.6mm, arc current 60~80A, arc length 3mm, negative arc ratio 20%~40%, EP state duty cycle 20%~30%, speed 0.6cm / s, applied longitudinal continuous alternating magnetic field with magnetic field strength 0.025~0.034T, arc negative pressure value -12~-120Pa, diameter of negative arc influence area 1.2~4mm, positive and negative arc pulse frequency 12~20kHz; (2) 2195 aluminum alloy additive manufacturing: hollow tungsten electrode with outer diameter 3mm and inner diameter 0.8mm, arc current 110~140A, arc length 5mm, negative arc ratio 15%~20%. The duty cycle of the EP state is 15-25%, the speed is 1cm / s, a longitudinal intermittent alternating magnetic field is applied, the magnetic field strength is 0.035-0.05T, the arc negative pressure value is -150--280Pa, the diameter of the negative pressure arc influence area is 5-10mm, and the positive and negative pressure arc pulse frequency is 1-15Hz; (3) ZK61 magnesium alloy additive: hollow tungsten electrode outer diameter 2.5mm, inner diameter 0.7mm, arc current 560A, arc length 10mm, negative pressure arc ratio is 30%-80%, EP state duty cycle 10%, speed 3cm / s, a longitudinal intermittent alternating magnetic field is applied, the magnetic field strength is 0.08T, the arc negative pressure value is -680Pa, and the pulse frequency is 0.6-1.2kHz;

[0031] Furthermore, the gas supplied to the hollow tungsten electrode is CO2, or nitrogen, or argon, or helium, or a binary mixture of argon and helium, or a ternary mixture.

[0032] Furthermore, the process supports three composite manufacturing modes: metal powder is introduced into the hollow tungsten electrode to achieve powder cladding additive manufacturing; welding wire is introduced into the hollow tungsten electrode to achieve welding wire cladding welding and additive manufacturing; or laser is introduced into the hollow tungsten electrode to form hollow tungsten electrode coaxial composite welding and additive manufacturing.

[0033] The beneficial effects of this invention include:

[0034] By utilizing a synergistic design of current, magnetic field, hollow tungsten electrode, and gas to induce a negative pressure arc with an anti-gravity adsorption effect, this method overturns the traditional unidirectional arc pressure mode and proposes a synergistic molten pool reconstruction and forming mechanism for magnetically controlled positive and negative pressure arc welding. The negative pressure arc forms a rotating adsorption flow field at the center of the molten pool, which counteracts the influence of gravity through upward rotational suction, fundamentally suppressing instability phenomena such as weld penetration in thin plates, flow or collapse of the molten pool in thin-walled additive manufacturing, and achieving a precise balance between molten pool dynamics and thermodynamic state.

[0035] By employing a positive and negative pressure pulse timing coupling process, the stress state of the molten pool is dynamically controlled. The negative pressure phase adsorbs liquid metal, enhancing the surface tension stability of the molten pool, while the positive pressure phase provides penetration depth, ensuring forming efficiency. The alternating action of positive and negative pressure pulses completely solves the problem of molten pool oscillation and instability caused by the thermal accumulation of a single positive pressure arc, making it particularly suitable for the dynamic, efficient, stable, and high-quality requirements of welding and additive manufacturing of thin-walled complex structures such as cantilevered and curved surfaces.

[0036] A dynamic matching model for magnetic field thresholds was established, and a functional relationship between current or gas mode and critical magnetic field was established to achieve precise generation and range control of negative pressure arc pulses. With the coordination of multiple parameters such as gas flow rate (0~10m / s) and EP duty cycle (10%~30%), welding or additive manufacturing efficiency was improved by more than 30%, and the defect rate was reduced by ≥30%.

[0037] To better demonstrate the process of achieving the objectives, functional characteristics, and advantages of this invention, the following will use embodiments and further explain them in detail with reference to the accompanying drawings. Attached Figure Description

[0038] Figure 1 (a) is a schematic diagram of the negative pressure arc principle of a positive and negative pressure pulsed arc welding and additive manufacturing method of the present invention;

[0039] Figure 1 (b) is a schematic diagram of the positive pressure arc principle of the positive and negative pressure pulsed arc welding and additive manufacturing method of the present invention;

[0040] Figure 2 This invention illustrates the relationship between the arc force of the positive and negative pressure pulses and time.

[0041] Figure 3 This invention illustrates the variation law of positive and negative voltage pulsed arc force distribution under the coordinated conditions of current-magnetic field-hollow tungsten electrode-gas supply.

[0042] Figure 4 This invention relates to the rotational adsorption effect of the electric arc during the negative pressure pulse stage under the synergistic conditions of current-magnetic field-hollow tungsten electrode-air extraction.

[0043] Figure 5 This invention describes the velocity field and flow field of the electric arc during the negative pressure pulse stage under the conditions of current-magnetic field-hollow tungsten electrode-no gas supply and no gas extraction.

[0044] Figure 6 This invention relates to the temperature field of a positive and negative voltage pulsed electric arc under the synergistic conditions of current-magnetic field-hollow tungsten electrode-gas.

[0045] Figure 7 This invention relates to a positive and negative pressure pulsed electric arc pressure field under the synergistic conditions of current-magnetic field-hollow tungsten electrode-gas;

[0046] Figure 8 The present invention relates to the velocity in the Z-direction of the central axis of a positive and negative voltage pulsed arc under the synergistic conditions of current-magnetic field-hollow tungsten electrode-gas;

[0047] Among them, 1-Tungsten electrode center hole, 2-Tungsten electrode, 3-Negative pressure zone, 4-Negative pressure arc, 5-Molten pool, 6-Substrate, 7-Positive pressure arc. Detailed Implementation

[0048] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0049] This addresses the challenge of molten pool instability during thin-plate welding and additive manufacturing of complex thin-walled structures, ensuring high-quality formability of welded or additively manufactured components. Specifically, for example... Figure 1 As shown, this invention proposes a positive and negative voltage pulsed arc welding and additive manufacturing method. This method is based on a synergistic design of current-magnetic field-hollow tungsten electrode-gas, utilizing the magnetic field to induce an anti-gravity adsorption effect in the hollow tungsten electrode arc plasma, achieving a time-coupled welding process of negative voltage arc 4 and positive voltage arc 7. Through the alternating pulsed action of the positive and negative voltage arcs, the stable kinetic and thermodynamic characteristics of the molten pool can be effectively controlled. Figure 2 The pulse relationship between arc pressure and time is shown. Figure 3 The diagram shows the positive and negative pressure conditions under different air delivery speeds, indicating that the air delivery speed can regulate the arc pressure. Under high-speed airflow, the airflow dominates the formation of a positive pressure arc; under low-speed airflow, the magnetic field dominates the formation of a negative pressure arc. Figure 4 The results show that increasing the air supply speed causes the recirculation range to continuously decrease. Figure 5 This also shows that the increase in gas delivery speed has a significant compression effect on the recirculation region, further confirming the above-mentioned regulation law.

[0050] The specific implementation steps are as follows:

[0051] Step 1: Fix the workpiece or additive manufacturing component on the platform, and fix the workpiece to be welded or the additive manufacturing substrate on the operating platform to ensure that the working surface is level;

[0052] Step 2: Set the parameters of the hollow tungsten electrode according to the material and structural requirements;

[0053] Step 3: Set up a variable polarity or pulsed arc power supply. Connect one end of the arc power supply to the hollow tungsten electrode and the other end to the workpiece to achieve variable polarity or pulsed hollow tungsten electrode arc welding or additive manufacturing. According to the material, structure and process requirements, adjust the electrode positive connection (EP) or pulse current duty cycle, welding current amplitude and frequency, and the direction and magnitude of gas flow inside the hollow tungsten electrode to coordinate and adapt to form an arc welding and additive manufacturing process with alternating negative and positive arc pressure.

[0054] Step 4: Set key process parameters, including arc parameters and magnetic field parameters. The arc current is 60-560A, the welding speed is 0.08-50cm / s, the duty cycle of the positive electrode (EP) state is 10%-30%, the outer diameter of the hollow tungsten electrode is 1.6-8mm, the inner diameter of the hollow tungsten electrode is 0.4-4mm, the magnetic field strength is 0.025-0.08T, the gas flow velocity inside the hollow tungsten electrode is 0-10m / s, and the threshold of the negative pressure arc magnetic field is greater than 0.022T.

[0055] Step 5: Turn on the hollow tungsten electrode arc power supply and external magnetic field excitation equipment to form a hollow tungsten electrode negative pressure arc for welding or additive manufacturing.

[0056] The hollow tungsten electrode negative pressure arc and positive pressure arc with anti-gravity swirling attraction effect are constructed in the following way: an excitation coil is set on the welding torch, and an excitation current is applied to generate a longitudinal magnetic field that coincides with or is parallel to the central axis of the arc; by dynamically adjusting the intensity of the longitudinal magnetic field to exceed the critical threshold for the formation of negative pressure in the hollow tungsten electrode arc, negative pressure and its range of action are formed at the center of the arc; in combination with a conventional positive pressure arc, or a positive pressure arc induced by a magnetic field, or a combination of the magnetic field with the direction and speed of gas flow inside the hollow tungsten electrode, an arc welding and additive manufacturing process in which negative and positive pressures of the arc are alternately applied is formed.

[0057] The negative pressure formed at the center of the electric arc is -12 to -680 Pa, the diameter of the negative pressure arc-affected area is 1.2 to 38 mm, and the arc length is 1 to 10 mm.

[0058] The negative pressure arc, which alternates between negative and positive pressure, accounts for 5% to 80% of the total arc. The low frequency of the positive and negative pressure pulses is 1 to 100 Hz, the medium frequency is 0.5 to 2 kHz, and the high frequency is 10 to 30 kHz.

[0059] The positive and negative voltage pulsed arc welding and additive manufacturing method is characterized in that the magnetic field threshold for forming the negative voltage arc is as follows:

[0060] (1) Under the natural state of the hollow tungsten electrode, i.e., without gas supply or extraction, the negative pressure arc magnetic field threshold and the arc current satisfy the following functional relationship.

[0061] B(I) = 0.15 - 3.87 × 10-3 ·I+4.45×10 -5 ·I 2 -2.23×10 -7 ·I 3 +4.17×10 -10 ·I 4

[0062] (2) Under the hollow tungsten electrode pumping method, the negative pressure arc magnetic field threshold and the pumping pressure satisfy the following functional relationship.

[0063] B(p) = 0.04 - 0.02 × exp(p / 9.18)

[0064] (3) Under the hollow tungsten electrode gas supply method, the negative pressure arc magnetic field threshold and the arc current satisfy the following functional relationship.

[0065] B(I) = 0.059 - 8.35 × 10 -4 ·I+6.71×10 -6 ·I 2 -1.67×10 -8 ·I 3

[0066] In the formula: B represents the magnetic field threshold, in Tesla (T), I represents the arc current, in Ampere (A), and p is the pumping pressure, in Pascal (Pa).

[0067] The aforementioned positive and negative pressure pulsed arc welding and additive manufacturing method creates a negative pressure region at the center of the arc, which has a rotational adsorption effect and forms a local low-pressure region. Under the adsorption force of the negative pressure arc and the electromagnetic stirring action, the liquid metal in the molten pool is stably and well formed, thus improving the efficiency and quality of welding or additive manufacturing.

[0068] The aforementioned positive and negative pressure pulsed arc welding and additive manufacturing method allows for flexible adjustment of the negative pressure magnitude, range, and duration of the hollow tungsten electrode negative pressure arc by changing the magnetic field strength and frequency, the gas supply method and flow rate of the hollow tungsten electrode, and the magnitude and duration of the arc current. The hollow tungsten electrode negative pressure arc and positive pressure arc work together to ensure the shape and properties of complex structures in welding or additive manufacturing in real time.

[0069] The positive and negative pressure pulsed arc welding and additive manufacturing method is characterized in that: the gas supplied to the hollow tungsten electrode is CO2, or nitrogen, or argon, or helium, or a binary mixture of argon and helium, or a ternary mixture.

[0070] The positive and negative voltage pulsed arc welding and additive manufacturing method is characterized in that: metal powder is introduced into the hollow tungsten electrode to achieve powder cladding additive manufacturing, or welding wire is introduced into the hollow tungsten electrode to achieve welding wire cladding welding and additive manufacturing, or laser is introduced into the hollow tungsten electrode to form hollow tungsten electrode coaxial composite welding and additive manufacturing.

[0071] The positive and negative pressure pulses and their frequencies refer to the pulses and frequencies of alternating positive and negative pressure, which are not the current pulses and frequencies of conventional arc welding processes. The two are fundamentally different.

[0072] Example 1

[0073] This embodiment of a positive and negative voltage pulsed arc welding and additive manufacturing method uses Q235 as the welding sample material and specifically includes the following steps:

[0074] Step 1: Fix the 1mm thick Q235 steel plate to the welding platform, ensuring horizontal positioning;

[0075] Step 2: Set the parameters of the hollow tungsten electrode 2: outer diameter of tungsten electrode 2mm, inner diameter of tungsten electrode center hole 1 0.6mm;

[0076] Step 3: Set up a variable polarity or pulsed arc power supply, connect one end of the arc power supply to the hollow tungsten electrode and the other end to the workpiece to realize variable polarity or pulsed hollow tungsten electrode arc welding or additive manufacturing; depending on the material, structure and process requirements, the positive and negative voltage arc pulse frequency is 12 to 20 kHz.

[0077] Step 4: Set key process parameters, including arc parameters and magnetic field parameters. The arc current is 60-80A, the arc length is 3mm, the negative pressure arc ratio is 20%-40%, the welding speed is 1cm / s, the duty cycle of the electrode positive connection (EP) state is 20%-30%, a longitudinal intermittent alternating magnetic field is applied with a magnetic field strength of 0.025-0.034T, forming a negative pressure region 3 of -12 to -120Pa, generating a negative pressure arc adsorption force 4, the diameter of the negative pressure arc influence region is 1.2-4mm, and the inlet flow velocity of the hollow tungsten electrode is 0-6m / s.

[0078] Step 5: Turn on the hollow tungsten electrode arc power supply and external magnetic field excitation equipment to form a hollow tungsten electrode negative voltage arc, according to... Figure 2 The pulse relationship graph showing the change of arc pressure over time is used for positive and negative pressure pulse welding.

[0079] Example 2

[0080] This embodiment describes a positive and negative voltage pulsed arc welding and additive manufacturing method. The additive manufacturing structural material is 2195 aluminum alloy plate, and the method specifically includes the following steps:

[0081] Step 1: Fix the 1.5mm thick 2195 aluminum alloy plate onto the platform, ensuring it is horizontally positioned;

[0082] Step 2: Set the parameters of the hollow tungsten electrode 2: outer diameter of tungsten electrode 3mm, inner diameter of tungsten electrode center hole 1 0.8mm;

[0083] Step 3: Set up a variable polarity or pulsed arc power supply, connect one end of the arc power supply to the hollow tungsten electrode, and the other end to the workpiece to realize variable polarity or pulsed hollow tungsten electrode arc welding or additive manufacturing; depending on the material, structure and process requirements, the positive and negative voltage arc pulse frequency is 1 to 15 Hz.

[0084] Step 4: Set key process parameters, including arc parameters and magnetic field parameters. The arc current is 110-140A, the arc length is 5mm, the negative pressure arc ratio is 15%-20%, the velocity is 1cm / s, the duty cycle of the variable polarity current EP state is 15-25%, a longitudinal intermittent alternating magnetic field is applied with a magnetic field strength of 0.035-0.05T, forming a negative pressure region 3 with a negative pressure value of -150 to -280Pa, generating a negative pressure arc adsorption force 4. The diameter of the negative pressure arc influence region is 5-10mm, and the inlet flow velocity of the hollow tungsten electrode is 0-8m / s.

[0085] Step 5: Turn on the hollow tungsten electrode arc power supply and external magnetic field excitation equipment to form a hollow tungsten electrode negative voltage arc, according to... Figure 2 The pulse relationship graph showing the change of arc pressure over time is used for positive and negative pressure pulse welding.

[0086] Example 3

[0087] This embodiment describes a positive and negative voltage pulsed arc welding and additive manufacturing method, where the additive manufacturing structural material is ZK61 magnesium alloy. The method specifically includes the following steps:

[0088] Step 1: Fix the 2mm thick ZK61 magnesium alloy plate onto the platform, ensuring it is horizontally positioned;

[0089] Step 2: Set the parameters of the hollow tungsten electrode 2: outer diameter of tungsten electrode 2.5mm, inner diameter of tungsten electrode center hole 1 0.7mm;

[0090] Step 3: Set up a variable polarity or pulsed arc power supply, connect one end of the arc power supply to the hollow tungsten electrode, and the other end to the workpiece to realize variable polarity or pulsed hollow tungsten electrode arc welding or additive manufacturing; depending on the material, structure and process requirements, the positive and negative voltage arc pulse frequency is 0.6 to 1.2 kHz.

[0091] Step 4: Set key process parameters, including arc parameters and magnetic field parameters. The arc current is 560A, the arc length is 10mm, the negative pressure arc ratio is 30% to 80%, the velocity is 3cm / s, the duty cycle of the variable polarity current EP state is 10%, a longitudinal intermittent alternating magnetic field is applied with a magnetic field strength of 0.08T, forming a negative pressure region 3 with a negative pressure value of -680Pa, generating a negative pressure arc adsorption force 4, the diameter of the negative pressure arc influence region is 38mm, and the inlet flow velocity of the hollow tungsten electrode is 0 to 10m / s.

[0092] Step 5: Turn on the hollow tungsten electrode arc power supply and external magnetic field excitation equipment to form a hollow tungsten electrode negative voltage arc, according to... Figure 2 The pulse relationship graph showing the change of arc pressure over time is used for positive and negative pressure pulse welding.

[0093] It should be noted that the above embodiments are only used to illustrate the technical principles of the present invention and are not intended to limit the scope of protection. Those skilled in the art can make adaptive modifications or equivalent substitutions to the technical solutions without departing from the core concept of the present invention, and all related modifications and improvements fall within the scope of protection defined by the claims.

Claims

1. A positive and negative pressure pulsed arc welding and additive manufacturing method, characterized by: The current-magnetic field-hollow tungsten electrode-gas collaborative design is used, the time sequence coupling welding process of the magnetic field induced hollow tungsten electrode arc plasma generating anti-gravity, adsorption effect of negative pressure arc and positive pressure arc is used, the pulse alternating action of the positive pressure arc and the negative pressure arc is used to control the dynamic and thermodynamic characteristics of the molten pool stability, the problem of molten pool instability in the thin plate welding and thin-walled complex structure additive manufacturing process is solved, and the high-quality formability of the welded or additive manufacturing component is ensured; The hollow tungsten electrode negative pressure arc and the positive pressure arc with anti-gravity rotation and suction effect are constructed in the following manner: an excitation coil is arranged on the welding gun, an excitation current is applied to generate a longitudinal magnetic field coinciding with or parallel to the center axis of the arc; the critical threshold value of the negative pressure formed by the hollow tungsten electrode arc is exceeded by dynamically adjusting the longitudinal magnetic field strength, so that a negative pressure is formed at the center of the arc and its action range; in cooperation with the conventional positive pressure arc, or the magnetic field induced positive pressure arc, or the magnetic field and the gas flow direction and speed in the hollow tungsten electrode, the arc welding and additive manufacturing process of the alternating action of the arc negative pressure and the positive pressure is formed; The negative pressure at the center of the arc is-12 to-680 Pa, the diameter of the negative pressure arc influence area is 1.2 to 38 mm, and the arc length is 1 to 10 mm; The negative pressure arc of the alternating action of the arc negative pressure and the positive pressure accounts for 5% to 80%, the positive and negative pressure arc pulse low frequency is 1 to 100 Hz, the medium frequency is 0.5 to 2 kHz, and the high frequency is 10 to 30 kHz.

2. A positive and negative pressure pulsed arc welding and additive manufacturing method according to claim 1, characterized in that, The magnetic field threshold value for forming the negative pressure arc is as follows: Mode 1, in the natural state of the hollow tungsten electrode, i.e. without gas supply or gas extraction, the negative pressure arc magnetic field threshold value and the arc current satisfy the following functional relationship, B(I) = 0.15 - 3.87 x 10 -3 • I + 4.45 x 10 -5 • I 2 - 2.23 x 10 -7 • I 3 + 4.17 x 10 -10 • I 4 Mode 2, in the hollow tungsten electrode gas extraction mode, the negative pressure arc magnetic field threshold value and the gas extraction pressure satisfy the following functional relationship, B(p) = 0.04-0.02*exp(p / 9.18) Mode 3, in the hollow tungsten electrode gas supply mode, the negative pressure arc magnetic field threshold value and the arc current satisfy the following functional relationship, B(I) = 0.059 - 8.35 x 10 -4 • I + 6.71 x 10 -6 • I 2 - 1.67 x 10 -8 • I 3 Wherein: B represents the magnetic field threshold value, unit: Tesla (T), I represents the arc current, unit: Ampere (A), p is the gas extraction pressure, unit: Pascal (Pa).

3. The method of claim 1, wherein, The time sequence collaborative process of the positive and negative pressure pulse arc welding and additive manufacturing method is performed according to the following steps: Step 1, fix the workpiece or additive manufacturing component on the platform; Step 2, set the hollow tungsten electrode parameters; Step 3, set the variable polarity or pulse arc power supply, connect the arc power supply to the hollow tungsten electrode at one end and to the workpiece at the other end, realize variable polarity or pulse hollow tungsten electrode arc welding or additive manufacturing; according to the material, structure and process requirements, adjust the electrode positive connection (EP) or pulse current duty cycle, welding current amplitude and frequency, gas flow direction and size in the hollow tungsten electrode, and cooperatively adapt to form the arc welding and additive manufacturing process of the alternating action of the arc negative pressure and the positive pressure. Step 4, set key process parameters, including arc parameters and magnetic field parameters, wherein the arc current is 60-560 A, the welding speed is 0.08-50 cm / s, the EP state duty cycle is 10%-30%, the hollow tungsten electrode outer diameter size is 1.6-8 mm, the hollow tungsten electrode inner diameter size is 0.4-4 mm, the magnetic field strength is 0.025-0.08 T, the hollow tungsten electrode inner gas flow rate is 0-10 m / s, and the negative pressure arc magnetic field threshold value is greater than 0.022 T; Step 5, turn on the hollow tungsten electrode arc power supply and the external magnetic field excitation device, form a hollow tungsten electrode negative pressure arc, and perform welding or additive manufacturing; The positive and negative pressure pulse arc welding and additive manufacturing method forms a negative pressure region at the center of the arc, has a rotating adsorption effect, forms a local low-pressure region, and the liquid metal in the molten pool is stably and high-quality formed under the action of the negative pressure arc adsorption force and electromagnetic stirring, thereby improving the welding or additive efficiency and quality. The negative pressure force size, range and action time of the hollow tungsten electrode negative pressure arc can be flexibly adjusted by changing the magnetic field strength and frequency, the gas feeding mode and flow rate of the hollow tungsten electrode, the arc current size and action time, and the hollow tungsten electrode negative pressure arc and the positive pressure arc cooperatively complete the welding or additive manufacturing of complex structures and guarantee the shape and performance in real time.

4. The method of claim 1, wherein: The welding sample material is Q235, the hollow tungsten electrode outer diameter is 2 mm, the inner diameter is 0.6 mm, the arc current is 60-80 A, the arc length is 3 mm, the negative pressure arc duty cycle is 20%-40%, the EP state duty cycle is 20%-30%, the speed is 0.6 cm / s, a longitudinal continuous alternating magnetic field is applied, the magnetic field strength is 0.025-0.034 T, a negative pressure region of -12 to -120 Pa is formed, the negative pressure arc influence region diameter is 1.2-4 mm, and the positive and negative pressure arc pulse frequency is 12-20 kHz.

5. The method of claim 1, wherein: The additive manufacturing structure material is 2195 aluminum alloy plate, the hollow tungsten electrode outer diameter is 3 mm, the inner diameter is 0.8 mm, the arc current is 110-140 A, the arc length is 5 mm, the negative pressure arc duty cycle is 15%-20%, the EP state duty cycle is 15-25%, the speed is 1 cm / s, a longitudinal intermittent alternating magnetic field is applied, the magnetic field strength is 0.035-0.05 T, the arc negative pressure value is -150 to -280 Pa, the negative pressure arc influence region diameter is 5-10 mm, and the positive and negative pressure arc pulse frequency is 1-15 Hz.

6. The method of claim 1, wherein: The additive manufacturing structure material is ZK61 magnesium alloy, the hollow tungsten electrode outer diameter is 2.5 mm, the inner diameter is 0.7 mm, the arc current is 560 A, the arc length is 10 mm, the negative pressure arc duty cycle is 30%-80%, the EP state duty cycle is 10%, the speed is 3 cm / s, a longitudinal intermittent alternating magnetic field is applied, the magnetic field strength is 0.08 T, the arc negative pressure value is -680 Pa, the negative pressure arc influence region diameter is 38 mm, and the positive and negative pressure arc pulse frequency is 0.6-1.2 kHz.

7. The method of claim 1, wherein: The gas fed by the hollow tungsten electrode is CO2, or nitrogen, or argon, or helium, or binary mixed gas of argon and helium, or ternary mixed gas.

8. The method of claim 1, wherein: The hollow tungsten electrode is connected with metal powder, and the metal powder is used for powder cladding additive manufacturing in cooperation with the powder; the hollow tungsten electrode is connected with welding wire, and the welding wire is used for welding and additive manufacturing in cooperation with the welding wire; or the hollow tungsten electrode is connected with laser, and the laser is used for forming hollow tungsten electrode coaxial composite welding and additive manufacturing in cooperation with the laser.

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