Method for thermo-mechanical synergistic negative-pressure arc cold metal transfer welding or additive manufacturing

Abstract

A method for thermo-mechanical synergistic negative-pressure arc cold metal transfer welding or additive manufacturing. The method comprises: performing pre-welding preparation; setting CMT process parameters and adjusting the relative position of a welding gun; configuring a CMT power supply and turning on a shielding gas; on the basis of a CMT current waveform and a transfer state of molten droplets (4), controlling and applying an adaptive negative-pressure arc suction force; and completing a thermo-mechanical synergistic negative-pressure arc cold metal transfer welding or additive manufacturing process. By means of the above-described steps, a suitable negative-pressure arc suction force resistant to an impact force and gravity is accurately applied during a molten-droplet transfer process, so as to reduce droplet spatter from a conventional positive-pressure arc (3) and reduce the impact of molten droplets on a molten pool (5), thereby making the molten droplets enter the molten pool more smoothly with lower heat input, achieving a thermo-mechanical synergistic behavior of negative-pressure arc cold metal transfer welding or additive manufacturing, and resulting in better forming and property quality of welding or additive manufacturing.

Description

A method for negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing Technical Field

[0001] The present invention relates to the field of arc cold metal transfer welding or additive manufacturing, and in particular to a method for negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing. Background Art

[0002] Arc welding technology and arc additive manufacturing technology are welding technologies and additive manufacturing technologies that use arc as a heat source. Due to the characteristics of arc's strong conductivity, concentrated energy and high temperature, arc welding technology and arc additive manufacturing technology have the advantages of high efficiency and low cost. However, due to the large heat input, they are often prone to a series of defects such as spatter and poor forming accuracy during operation. Especially when welding and additive manufacturing thin-walled structures, it is very easy for the thin-walled structures to deform or burn through due to excessive heat input, which can lead to the scrapping of the workpiece.

[0003] Cold Metal Transfer (CMT) technology has been widely researched and applied in welding and additive manufacturing due to its spatter-free, extremely low heat input, and stable arc. To address these issues, arc welding and additive manufacturing technologies based on cold metal transfer have emerged. Compared to traditional technologies, CMT arc welding or additive manufacturing can achieve low heat input, stable arc, and precise fuse control. This completely breaks the research status quo of traditional arc welding or additive manufacturing technologies, which have been difficult to achieve with thin-walled structures.

[0004] However, arc welding and additive manufacturing technologies based on cold metal transfer also have technical bottlenecks: in the process of droplet growth and dripping of conventional positive pressure arc, due to the effect of gravitational acceleration of the droplet, it is easy to cause arc droplet splashing and droplet impact on the molten pool, which has a certain thermal incoordination for welding or additive manufacturing of ultra-thin wall structures, and has an adverse effect on the formative quality of welding; at the same time, CMT arc additive manufacturing (WAAM) technology uses arc as the heat source to melt the wire and clad it layer by layer. Since CMT arc additive manufacturing is a process of continuous repeated heating, due to this repeated heating production method, it is very easy to cause internal residual stress to continue to increase, there are thermal-mechanical defects, and it is difficult to obtain a good balance between heat and force, which has an adverse effect on the formative quality of additive manufacturing. Technical issues

[0005] In view of this, the present invention proposes a method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing to solve the above problems. Technical Solutions

[0006] In order to solve the above problems, the purpose of the present invention is to propose a method for negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing, by accurately applying appropriate anti-impact force and anti-gravity negative pressure arc adsorption force during the droplet transfer process to reduce the splashing of molten droplets in conventional positive pressure arcs and reduce the impact of molten droplets on the molten pool, so that the droplets can enter the molten pool more smoothly and with lower heat input, thereby achieving thermal synergistic behavior of negative pressure arc cold metal transfer welding or additive manufacturing, thereby obtaining better welding or additive manufacturing formative quality.

[0007] The above objectives are achieved through the following technical solutions:

[0008] A method for negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing, comprising the following steps:

[0009] Step 1, preparation before welding: Before welding, grind or clean the workpiece to be welded or the additive manufacturing substrate, and fix the grinded or cleaned workpiece to be welded or the additive manufacturing substrate;

[0010] Step 2: Set the CMT process parameters and adjust the relative position of the welding gun: set the welding gun to the appropriate height, select the appropriate welding wire, and determine the appropriate process parameters;

[0011] Step 3: Set up the CMT power supply and start the shielding gas: Open the shielding gas valve and then turn on the CMT power supply.

[0012] Step 4: Control and apply an adaptive negative pressure arc suction force according to the CMT current waveform and droplet transfer state: The CMT parameters are adjusted through the control system. According to the current waveform and droplet transfer state, an external longitudinal magnetic field is applied to form and adjust the action time, duration, frequency and magnitude of the negative pressure arc suction force. The specific process is as follows:

[0013] (1) The welding wire is fed downward, the current is increased, the arc is ignited, and the tip of the welding wire melts. Under the action of the upward surface tension Fs and the electromagnetic force Fem that promotes the droplet to fall off, the molten droplet gradually grows, and the initial gravity Fg0 of the molten droplet gradually increases;

[0014] (2) The wire is retracted to promote the separation of the molten droplet from the wire and start to fall. The current decreases and reaches the minimum value. At this moment, an external longitudinal magnetic field is applied to form an upward adsorption force Fi opposite to gravity to overcome the critical gravity Fg1 and impact force of the downward molten droplet transition, reduce the molten droplet splashing of the conventional positive pressure arc, reduce the impact of the molten droplet on the molten pool, and make the molten droplet enter the molten pool smoothly with low heat input, realizing the thermal synergy process of negative pressure arc cold metal transfer welding or additive manufacturing, achieving the good effect of thermal synergy of smooth and controllable molten droplet transition without impact, spatter, and low heat, thereby obtaining better welding or additive manufacturing formative quality;

[0015] (3) The welding wire returns to the feeding state, the current rises to the normal value, the external longitudinal magnetic field is turned off, the negative pressure arc adsorption force disappears, the arc burns normally again, and the molten droplet gradually forms at the end of the welding wire. The molten droplet transfer repeats this process repeatedly;

[0016] Step 5: Complete the negative pressure arc cold metal transfer thermally coordinated welding or additive manufacturing process: cut off the current, stop the fuse and droplet transfer, turn off the shielding gas, and move the welding gun to a safe position.

[0017] Furthermore, in step 4, the negative pressure arc adsorption force is -12 to -418 Pa, the action waveform of the negative pressure arc adsorption force is opposite to the CMT current waveform, the action frequency of the negative pressure arc adsorption force is coordinated with the CMT current frequency, the action time of the negative pressure arc adsorption force is consistent with the time of the lowest value of the CMT current, the action moment of the negative pressure arc adsorption force is consistent with the moment when the molten droplet falls off at the end of the welding wire and begins to transition, the magnitude of the negative pressure arc adsorption force is adjustable, can change during the molten droplet transition process, and is inversely proportional to the transition speed of the molten droplet and the distance from the molten pool surface.

[0018] Furthermore, in step 2, the diameter of the welding wire is 0.8 to 6 mm, the height of the welding wire tip from the workpiece or substrate is 2 to 6 mm, the wire feeding speed is 0.1 to 40 m / min, the welding speed is 10 to 600 mm / s, the dry extension of the welding wire is 2 to 10 mm, and the wire retraction amount and feed amount are 1 to 10 mm.

[0019] Furthermore, in step 3, the type of the protective gas is 100% argon, or 100% helium, or a mixed gas of argon + carbon dioxide, or carbon dioxide gas, or a quaternary mixed gas with argon + helium as the main body + a small amount of hydrogen + a small amount of oxygen, or a ternary mixed gas with argon + helium as the main body + a small amount of oxygen, and the gas flow rate is 8 to 38 L / min.

[0020] Furthermore, in step 4, the negative pressure arc adsorption force can be generated, adjusted, changed and controlled by adjusting the intensity, frequency, duty cycle and mode of the external longitudinal magnetic field and matching it with the arc current, and the magnitude, action duration, action moment and action frequency of the negative pressure arc adsorption force are generated, adjusted, changed and controlled. The intensity of the external longitudinal magnetic field is 0.02 to 4.8 T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, and the mode of the external longitudinal magnetic field is a continuous alternating magnetic field mode, an intermittent alternating magnetic field mode, or a pulsed alternating magnetic field mode; the mode of the external longitudinal magnetic field is a fixed longitudinal magnetic field mode, a rotating longitudinal magnetic field mode, an inward and outward reversed longitudinal dual magnetic field mode, or an up and down reversed longitudinal dual magnetic field mode.

[0021] Furthermore, in step 4, the relationship between the CMT current and the negative pressure arc adsorption force shows a one-to-one negative correlation, and the change pattern repeats over time until welding or additive manufacturing is completed. The voltage is 10 to 60 V and the current is 30 to 480 A.

[0022] Furthermore, the method is applicable to aluminum alloy materials, or alloy steel materials, or magnesium alloy materials, or titanium alloy materials, or stainless steel materials, or molybdenum alloy materials, or copper alloy materials, or aluminum-copper dissimilar materials, or aluminum-steel dissimilar materials, or cemented carbide materials, or rare metal materials, or refractory metal materials, or high entropy alloy materials, or medium entropy alloy materials, or metal-based composite materials. Beneficial effects

[0023] The beneficial effects of the present invention are:

[0024] By precisely applying appropriate anti-impact and anti-gravity negative pressure arc adsorption forces during the droplet transition process, the splashing of droplets in conventional positive pressure arcs is reduced, and the impact of droplets on the molten pool is reduced, so that droplets enter the molten pool more smoothly and with lower heat input, achieving thermal synergy of negative pressure arc cold metal transfer welding or additive manufacturing, and reducing residual stress caused by repeated alternation of hot and cold during arc additive manufacturing printing. For thin-walled structures and even ultra-thin-walled structures, it can reduce deformation and even burn-through defects caused by thermal incoordination, thereby achieving better welding or additive manufacturing formative quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The purpose, features and advantages of the present invention will be further described with reference to the embodiments and accompanying drawings.

[0026] FIG1 is a graph showing the relationship between welding current and negative pressure arc adsorption force over time according to the present invention;

[0027] FIG2 is a force analysis diagram of the droplet growth process of the present invention;

[0028] FIG3 is a force analysis diagram of the droplet transfer process of the present invention;

[0029] The reference numerals are as follows:

[0030] 1. Workpiece or AM substrate; 2. Welding wire; 3. Arc; 4. Molten droplet; 5. Molten pool; Fg0 is the initial gravity; Fg1 is the critical gravity; Fs is the surface tension; Fi is the negative pressure arc attraction force; Fem is the electromagnetic force. Best Mode for Carrying Out the Invention

[0031] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0032] In the description of the present invention, unless otherwise specified, "plurality" means two or more; terms such as "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," and "tail" indicate positions or relationships based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0034] The following describes a method for negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing provided by the present invention in conjunction with Figures 1 to 3, including the following steps:

[0035] Step 1, preparation before welding: before welding, the workpiece to be welded or the additive manufacturing substrate 1 is polished or cleaned of stains, and the polished or cleaned workpiece to be welded or the additive manufacturing substrate 1 is fixed;

[0036] Step 2: Set the CMT process parameters and adjust the relative position of the welding gun: set the welding gun to a suitable height, select the appropriate welding wire 2, and determine the parameters of the appropriate process;

[0037] Step 3: Set up the CMT power supply and start the shielding gas: Open the shielding gas valve and then turn on the CMT power supply.

[0038] Step 4: Control and apply an adaptive negative pressure arc suction force according to the CMT current waveform and droplet transfer state: The CMT parameters are adjusted through the control system. According to the current waveform and droplet transfer state, an external longitudinal magnetic field is applied to form and adjust the action time, duration, frequency and magnitude of the negative pressure arc suction force. The specific process is as follows:

[0039] (1) The welding wire 2 is fed downward, the current is increased, the arc 3 is ignited, the tip of the welding wire 2 melts, and under the action of the upward surface tension Fs and the electromagnetic force Fem that promotes the droplet 4 to fall off, the droplet 4 gradually grows, and the initial gravity Fg0 of the droplet 4 gradually increases;

[0040] (2) The wire 2 is retracted to promote the separation of the molten drop 4 from the wire 2 and start to fall. The current decreases and reaches the minimum value. At this moment, an external longitudinal magnetic field is applied to form an upward adsorption force Fi opposite to gravity to overcome the critical gravity Fg1 and impact force of the downward molten drop transition, reduce the splash of the molten drop 4 in the conventional positive pressure arc, reduce the impact of the molten drop 4 on the molten pool 5, and make the molten drop 4 enter the molten pool 5 smoothly with low heat input, realize the thermal synergy process of negative pressure arc cold metal transfer welding or additive manufacturing, and achieve the good effect of thermal synergy of smooth and controllable molten drop transition without impact, spatter and low heat, so as to obtain better welding or additive manufacturing formative quality;

[0041] (3) The welding wire 2 returns to the feeding state, the current rises to the normal value, the external longitudinal magnetic field is turned off, the negative pressure arc adsorption force disappears, the arc 3 burns normally again, and the molten droplet 4 gradually forms at the end of the welding wire. The molten droplet transfer repeats this process repeatedly;

[0042] Step 5, complete the negative pressure arc cold metal transfer thermal coordinated welding or additive manufacturing process: cut off the current, stop the fuse 2 and the molten droplet transfer, turn off the shielding gas, and move the welding gun to a safe position.

[0043] More specific embodiments are as follows:

[0044] In step 4, the negative pressure arc adsorption force is -12 to -418 Pa. It should be noted that the negative sign represents the upward direction. The negative pressure arc adsorption force in Figure 1 only refers to the size. The waveform of the negative pressure arc adsorption force is opposite to the CMT current waveform. The action frequency of the negative pressure arc adsorption force is coordinated with the CMT current frequency. The action time of the negative pressure arc adsorption force is consistent with the time of the lowest value of the CMT current. The action moment of the negative pressure arc adsorption force is consistent with the moment when the molten droplet 4 falls off at the end of the welding wire 2 and begins to transition. The size of the negative pressure arc adsorption force is adjustable and can change during the molten droplet transition process. It is inversely proportional to the transition speed of the molten droplet 4 and the distance from the surface of the molten pool 5.

[0045] In step 2, the diameter of the welding wire is 0.8 to 6 mm, the height of the welding wire tip from the workpiece or substrate is 2 to 6 mm, the wire feeding speed is 0.1 to 40 m / min, the welding speed is 10 to 600 mm / s, the welding wire dry extension is 2 to 10 mm, and the welding wire retraction amount and feed amount are 1 to 10 mm.

[0046] In step 3, the type of the protective gas is 100% argon, or 100% helium, or a mixed gas of argon and carbon dioxide, or carbon dioxide gas, or a quaternary mixed gas mainly composed of argon and helium, a small amount of hydrogen, and a small amount of oxygen, or a ternary mixed gas mainly composed of argon and helium, and a small amount of oxygen, and the gas flow rate is 8 to 38 L / min.

[0047] In step 4, the negative pressure arc adsorption force can be generated, adjusted, changed and controlled by adjusting the intensity, frequency, duty cycle and mode of the external longitudinal magnetic field and matching it with the arc current, and the magnitude, action duration, action time and action frequency of the negative pressure arc adsorption force are generated, adjusted, changed and controlled, the intensity of the external longitudinal magnetic field is 0.02~4.8 T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, the mode of the external longitudinal magnetic field is a continuous alternating magnetic field mode, an intermittent alternating magnetic field mode, or a pulsed alternating magnetic field mode; the mode of the external longitudinal magnetic field is a fixed longitudinal magnetic field mode, a rotating longitudinal magnetic field mode, an inward and outward reversed longitudinal dual magnetic field mode, or an up and down reversed longitudinal dual magnetic field mode.

[0048] In step 4, the relationship between the CMT current and the negative pressure arc adsorption force shows a one-to-one negative correlation, and the change pattern repeats over time until welding or additive manufacturing is completed. The voltage is 10 to 60 V and the current is 30 to 480 A.

[0049] The method is applicable to aluminum alloy materials, or alloy steel materials, or magnesium alloy materials, or titanium alloy materials, or stainless steel materials, or molybdenum alloy materials, or copper alloy materials, or aluminum-copper dissimilar materials, or aluminum-steel dissimilar materials, or cemented carbide materials, or rare metal materials, or refractory metal materials, or high-entropy alloy materials, or medium-entropy alloy materials, or metal-based composite materials. Modes for Carrying Out the Invention Example 1

[0050] The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing provided in this embodiment specifically includes the following steps:

[0051] The first step is preparation before additive manufacturing: 2219 aluminum alloy is used as the substrate, and the 2219 aluminum alloy is polished or cleaned of stains. The polished or cleaned 2219 aluminum alloy is fixed. The thickness of the substrate 1 is 1.5 mm, and the preheating temperature is 30-80°C.

[0052] The second step is to set the CMT process parameters and adjust the relative position of the welding gun: set the welding gun to an appropriate height, select the appropriate welding wire, and determine the appropriate process parameters. 2219 aluminum alloy welding wire is selected as the wire material, the diameter of the welding wire 2 is 1.2 mm, the height of the welding wire 2 tip from the substrate 1 is 2.5 mm, the wire feed speed is 15-21 m / min, the welding speed is 26-100 mm / s, the dry extension of the welding wire 2 is 2-4 mm, and the retraction and feed amount of the welding wire 2 are 2-3 mm.

[0053] The third step is to set the CMT power supply and start the shielding gas: open the gas shielding valve, then turn on the CMT power supply, 100% argon shielding, and the gas flow rate is 17-20 L / min;

[0054] The fourth step is to control and apply the appropriate negative pressure arc adsorption force according to the CMT current waveform and the droplet transition state: the CMT parameters are adjusted by the control system, and the action time, duration, frequency and magnitude of the negative pressure arc adsorption force are formed and adjusted by applying an external longitudinal magnetic field according to the current waveform and the droplet transition state. The specific process is as follows: (1) As shown in Figure 2, the welding wire 2 is fed downward, and the current is increased to 90~110 A to ignite the arc 3 and melt the tip of the welding wire 2. Under the action of the upward surface tension Fs and the electromagnetic force Fem that promotes the detachment of the droplet 4, the droplet 4 gradually grows, and the initial gravity Fg0 of the droplet gradually increases; (2) As shown in Figure 3, the welding wire 2 is retracted to promote the separation of the droplet 4 from the welding wire 2 and start to fall. The current is reduced to 25~50 A. At this moment, an external longitudinal magnetic field is applied to form an adsorption force Fi in the opposite direction to the gravity, and its magnitude is -30~-80 Pa, in order to overcome the critical gravity Fg1 and impact force of the downward molten droplet transition, reduce the splash of the molten droplet 4 of the conventional positive pressure arc, reduce the impact of the molten droplet 4 on the molten pool 5, make the molten droplet 4 enter the molten pool 5 smoothly with low heat input, realize the thermal synergy process of negative pressure arc cold metal transfer welding or additive manufacturing, and achieve the good effect of thermal synergy of smooth and controllable molten droplet transition without impact, spatter, and low heat, so as to obtain better welding or additive manufacturing formative quality; (3) The welding wire 2 returns to the feeding state, the current rises to the normal value, the external longitudinal magnetic field is turned off, the negative pressure arc adsorption force disappears, the arc 3 burns normally again, and the molten droplet 4 gradually forms at the end of the welding wire 2; the negative pressure arc adsorption force can be generated, adjusted, changed and controlled by adjusting the intensity, frequency, duty cycle, mode of the external longitudinal magnetic field and matching it with the arc current, and the magnitude, action duration, action time and action frequency of the negative pressure arc adsorption force. The intensity of the external longitudinal magnetic field is 0.12~0.18 T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, and the method of applying the longitudinal magnetic field is the longitudinal intermittent alternating magnetic field method;

[0055] As shown in Figure 1, the negative pressure arc attraction waveform is opposite to the CMT current waveform. The frequency of the negative pressure arc attraction is consistent with the CMT current frequency. The duration of the negative pressure arc attraction coincides with the time of the CMT current minimum. The moment of the negative pressure arc attraction coincides with the moment when the molten droplet falls off the end of the welding wire and begins to transfer. The magnitude of the negative pressure arc attraction is adjustable and varies during the droplet transfer process, inversely proportional to the droplet transfer speed and distance from the molten pool surface. The relationship between the CMT current and the negative pressure arc attraction shows a one-to-one negative correlation, and the change pattern repeats over time until the additive manufacturing is completed. The voltage is 18 to 22 V.

[0056] The fifth step is to complete the negative pressure arc cold metal transfer thermal coordination additive manufacturing process: cut off the current, stop the fuse 2 and the molten droplet transfer, turn off the shielding gas, and move the welding gun to a safe position. Example 2

[0057] The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing provided in this embodiment specifically includes the following steps:

[0058] Step 1: Preparation before additive manufacturing: Use 6061 aluminum alloy as substrate 1, polish or clean the 6061 aluminum alloy, and fix the polished or cleaned 6061 aluminum alloy. The thickness of substrate 1 is 2.5 mm and the preheating temperature is 30-80°C.

[0059] The second step is to set the CMT process parameters and adjust the relative position of the welding gun: set the welding gun to an appropriate height, select the appropriate welding wire, and determine the appropriate process parameters. 6061 welding wire is selected as the wire material, the diameter of welding wire 2 is 2.4 mm, the height between the tip of welding wire 2 and substrate 1 is 5 mm, the wire feed speed is 4-8 m / min, the welding speed is 8-15 mm / s, the dry extension of welding wire 2 is 4-6 mm, and the retraction and feed amount of welding wire 2 are 1-3 mm.

[0060] The third step is to set the CMT power supply and start the shielding gas: open the gas shielding valve, then turn on the CMT power supply, 100% argon shielding, and the gas flow rate is 16-24 L / min;

[0061] The fourth step is to control and apply the adaptive negative pressure arc adsorption force according to the CMT current waveform and the droplet transition state: the CMT parameters are adjusted by the control system, and the action time, duration, frequency and magnitude of the negative pressure arc adsorption force are formed and adjusted by applying an external longitudinal magnetic field according to the current waveform and the droplet transition state. The specific process is as follows: (1) As shown in Figure 2, the welding wire 2 is fed downward, and the current is increased to 100~120A to ignite the arc 3 and melt the tip of the welding wire 2. Under the action of the upward surface tension Fs and the electromagnetic force Fem that promotes the detachment of the droplet 4, the droplet 4 gradually grows, and the initial gravity Fg0 of the droplet gradually increases; (2) As shown in Figure 3, the welding wire 2 is retracted to promote the separation of the droplet 4 from the welding wire 2 and start to fall. The current is reduced to 30~60A. At this moment, an external longitudinal magnetic field is applied to form an adsorption force Fi in the opposite direction to the gravity and in the upward direction, and its magnitude is -60~-120 Pa, in order to overcome the critical gravity Fg1 and impact force of the downward molten droplet transition, reduce the splash of the molten droplet 4 of the conventional positive pressure arc, reduce the impact of the molten droplet 4 on the molten pool 5, make the molten droplet 4 enter the molten pool 5 smoothly with low heat input, realize the thermal synergy process of negative pressure arc cold metal transition additive manufacturing, and achieve the good effect of thermal synergy of smooth and controllable molten droplet transition without impact, splashing and low heat, so as to obtain better additive manufacturing quality; (3) The welding wire 2 returns to the feeding state, the current rises to the normal value, the external longitudinal magnetic field is turned off, the negative pressure arc adsorption force disappears, the arc 3 burns normally again, and the molten droplet 4 gradually forms at the end of the welding wire 2; the negative pressure arc adsorption force can be generated, adjusted, changed and controlled by adjusting the intensity, frequency, duty cycle and mode of the external longitudinal magnetic field and matching it with the arc current, and the magnitude, action duration, action time and action frequency of the negative pressure arc adsorption force. The intensity of the external longitudinal magnetic field is 0.24~0.32 T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, and the external longitudinal magnetic field is a longitudinal continuous alternating magnetic field;

[0062] As shown in Figure 1, the negative pressure arc attraction force waveform is opposite to the CMT current waveform. The frequency of the negative pressure arc attraction force is consistent with the CMT current frequency. The duration of the negative pressure arc attraction force is consistent with the time of the CMT current minimum. The moment of the negative pressure arc attraction force's action coincides with the moment when the molten droplet falls off the end of the welding wire and begins to transfer. The magnitude of the negative pressure arc attraction force is adjustable and can change during the droplet transfer process, inversely proportional to the droplet's transfer speed and distance from the molten pool surface. The relationship between the CMT current and the negative pressure arc attraction force shows a one-to-one negative correlation, and the change pattern repeats over time until the additive manufacturing is completed. The voltage range is 45 to 80 V.

[0063] The fifth step is to complete the negative pressure arc cold metal transfer thermal coordination additive manufacturing process: cut off the current, stop the fuse 2 and the molten droplet transfer, turn off the shielding gas, and move the welding gun to a safe position. Example 3

[0064] The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing provided in this embodiment specifically includes the following steps:

[0065] Step 1: Preparation before welding: Use a galvanized duplex steel plate as workpiece 1, polish or clean the galvanized duplex steel plate, and fix the polished or cleaned galvanized duplex steel plate. The thickness of workpiece 1 is 6 mm, and the preheating temperature is 30-80°C.

[0066] The second step is to set the CMT process parameters and adjust the relative position of the welding gun: set the welding gun to an appropriate height, select the appropriate welding wire, and use high-strength steel wire as the wire material. The diameter of the welding wire 2 is 3 mm, the height between the welding wire 2 tip and the workpiece is 3 mm, the wire feed speed is 12-18 m / min, the welding speed is 20-30 mm / s, the dry extension of the welding wire 2 is 6-8 mm, and the retraction and feed amount of the welding wire 2 are 3-6 mm.

[0067] Step 3: Set up the CMT power supply and start the shielding gas: open the gas shielding valve, then turn on the CMT power supply, 100% helium shielding, and a gas flow rate of 14-20 L / min;

[0068] The fourth step is to control and apply the adaptive negative pressure arc adsorption force according to the CMT current waveform and the droplet transition state: the CMT parameters are adjusted by the control system, and the action time, duration, frequency and magnitude of the negative pressure arc adsorption force are formed and adjusted by applying an external longitudinal magnetic field according to the current waveform and the droplet transition state. The specific process is as follows: (1) As shown in Figure 2, the welding wire 2 is fed downward, and the current is increased to 160~240 A to ignite the arc 3 and melt the tip of the welding wire 2. Under the action of the upward surface tension Fs and the electromagnetic force Fem that promotes the detachment of the droplet 4, the droplet 4 gradually grows, and the initial gravity Fg0 of the droplet gradually increases; (2) As shown in Figure 3, the welding wire 2 is retracted to promote the separation of the droplet 4 from the welding wire 2 and start to fall. The current is reduced to 40~100 A. At this moment, an external longitudinal magnetic field is applied to form an adsorption force Fi in the opposite direction to the gravity, with a magnitude of -160~-240 Pa, in order to overcome the critical gravity Fg1 and impact force of the downward molten droplet transition, reduce the splash of the molten droplet 4 of the conventional positive pressure arc, reduce the impact of the molten droplet 4 on the molten pool 5, make the molten droplet 4 enter the molten pool 5 smoothly with low heat input, realize the thermal synergy process of negative pressure arc cold metal transfer welding, and achieve the good effect of smooth and controllable molten droplet transition without impact, spatter and low heat, so as to obtain better welding quality; (3) The welding wire 2 returns to the feeding state, the current rises to the normal value, the external longitudinal magnetic field is turned off, the negative pressure arc adsorption force disappears, the arc 3 burns normally again, and the molten droplet 4 gradually forms at the end of the welding wire 2; the negative pressure arc adsorption force can be generated, adjusted, changed and controlled by adjusting the intensity, frequency, duty cycle and mode of the external longitudinal magnetic field and matching it with the arc current, and the magnitude, action duration, action time and action frequency of the negative pressure arc adsorption force. The intensity of the external longitudinal magnetic field is 0.28~0.36 T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, and the external longitudinal magnetic field is a longitudinal continuous alternating magnetic field;

[0069] As shown in Figure 1, the negative pressure arc attraction force waveform is opposite to the CMT current waveform. The frequency of the negative pressure arc attraction force is consistent with the CMT current frequency. The duration of the negative pressure arc attraction force is consistent with the time of the lowest CMT current. The moment of the negative pressure arc attraction force's action coincides with the moment when the molten droplet falls off the end of the welding wire and begins to transfer. The magnitude of the negative pressure arc attraction force is adjustable and can change during the droplet transfer process, inversely proportional to the droplet's transfer speed and distance from the molten pool surface. The relationship between the CMT current and the negative pressure arc attraction force shows a one-to-one negative correlation, and the change pattern repeats over time until the welding is completed. The voltage range is 6 to 18 V.

[0070] The fifth step is to complete the negative pressure arc cold metal transfer thermal coordination welding process: cut off the current, stop the fuse 2 and the molten droplet transfer, turn off the shielding gas, and move the welding gun to a safe position.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing, characterized in that: The following steps are involved: Step 1, preparation before welding: Before welding, grind or clean the workpiece to be welded or the additive manufacturing substrate, and fix the grinded or cleaned workpiece to be welded or the additive manufacturing substrate; Step 2: Set the CMT process parameters and adjust the relative position of the welding gun: Set the welding gun to an appropriate height, select the appropriate welding wire, and determine the appropriate process parameters. Specifically, the welding wire diameter is 0.8-6 mm, the height between the welding wire tip and the workpiece or substrate is 2-6 mm, the wire feed speed is 0.1-40 m / min, the welding speed is 10-600 mm / s, the welding wire dry extension is 2-10 mm, and the welding wire retraction and feed amount are 1-10 mm. Step 3: Set up the CMT power supply and start the shielding gas: Open the shielding gas valve and then turn on the CMT power supply. Step 4: Control and apply an adaptive negative pressure arc suction force according to the CMT current waveform and droplet transfer state: The CMT parameters are adjusted through the control system. According to the current waveform and droplet transfer state, an external longitudinal magnetic field is applied to form and adjust the action time, duration, frequency and magnitude of the negative pressure arc suction force. The specific process is as follows: (1) The welding wire is fed downward, the current is increased, the arc is ignited, and the tip of the welding wire melts. Under the action of the upward surface tension Fs and the electromagnetic force Fem that promotes the droplet to fall off, the molten droplet gradually grows, and the initial gravity Fg0 of the molten droplet gradually increases; (2) The wire is retracted to promote the separation of the molten droplet from the wire and start to fall. The current decreases and reaches the minimum value. At this moment, an external longitudinal magnetic field is applied to form a negative pressure arc adsorption force Fi in the opposite direction to gravity, so as to overcome the critical gravity Fg1 and impact force of the molten droplet transition in the downward direction, reduce the molten droplet splashing of the conventional positive pressure arc, reduce the impact of the molten droplet on the molten pool, and make the molten droplet enter the molten pool smoothly with low heat input, realize the thermal synergy process of negative pressure arc cold metal transfer welding or additive manufacturing, and achieve the good effect of thermal synergy of smooth and controllable molten droplet transition without impact, spatter and low heat, so as to obtain better forming quality of welding or additive manufacturing; (3) The welding wire returns to the feeding state, the current rises to the normal value, the external longitudinal magnetic field is turned off, the negative pressure arc adsorption force disappears, the arc burns normally again, and the molten droplet gradually forms at the end of the welding wire. The molten droplet transfer repeats this process repeatedly; In step 4, the negative pressure arc adsorption force is -12 to -418 Pa, the negative sign represents that the direction of the arc adsorption force is upward, the action waveform of the negative pressure arc adsorption force is opposite to the CMT current waveform, the action frequency of the negative pressure arc adsorption force is coordinated with the CMT current frequency, the action time of the negative pressure arc adsorption force is consistent with the time of the lowest value of the CMT current, the action moment of the negative pressure arc adsorption force is consistent with the moment when the molten droplet falls off at the end of the welding wire and begins to transition, the magnitude of the negative pressure arc adsorption force is adjustable and can change during the molten droplet transition process, and is inversely proportional to the transition speed of the molten droplet and the distance from the molten pool surface; the relationship between the CMT current and the negative pressure arc adsorption force shows a one-to-one negative correlation, and the change pattern repeats over time until the welding or additive manufacturing process is completed. The voltage is 10 to 60 V, and the current is 30 to 480 A; The negative pressure arc attraction force is generated, adjusted, changed and controlled by adjusting the intensity, frequency, duty cycle and mode of the external longitudinal magnetic field and matching it with the arc current, thereby generating, adjusting, changing and controlling the magnitude, duration, moment and frequency of the negative pressure arc attraction force. The intensity of the external longitudinal magnetic field is 0.02 to 4.8 T. The negative pressure arc attraction force is based on the relative pressure of atmospheric pressure. The mode of the external longitudinal magnetic field is continuous alternating magnetic field mode or intermittent alternating magnetic field mode. The mode of the external longitudinal magnetic field is fixed longitudinal magnetic field mode or rotating longitudinal magnetic field mode. Step 5: Complete the negative pressure arc cold metal transfer thermally coordinated welding or additive manufacturing process: cut off the current, stop the fuse and droplet transfer, turn off the shielding gas, and move the welding gun to a safe position.

2. The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing according to claim 1, characterized in that: The process parameters of the negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method are as follows: additive manufacturing, 2219 aluminum alloy is used as a substrate with a thickness of 1.5 mm, a preheating temperature of 30-80°C, 2219 aluminum alloy welding wire is used as a wire material, the diameter of the welding wire is 1.2 mm, the height between the welding wire tip and the substrate is 2.5 mm, the wire feeding speed is 15-21 m / min, the welding speed is 26-100 mm / s, the welding wire dry extension is 2-4 mm, the welding wire retraction amount and feed amount are 2-3 mm, 100% argon shielding, the gas flow rate is 17-20 L / min, the welding current increases to 90-110 A when the welding wire is fed downward, and decreases to 25-50 A when the welding wire is retracted, the negative pressure arc adsorption force is -30--80 Pa, the strength of the applied longitudinal magnetic field is 0.12-0.18 T, and the voltage is 18-22 V.

3. The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing according to claim 1, characterized in that: The process parameters of the negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method are as follows: additive manufacturing, 6061 aluminum alloy is used as the substrate, the substrate thickness is 2.5 mm, the preheating temperature is 30-80°C, 6061 aluminum alloy welding wire is used as the wire material, the welding wire diameter is 2.4 mm, the height between the welding wire tip and the substrate is 5 mm, the wire feeding speed is 4-8 m / min, the welding speed is 8-15 mm / s, the welding wire dry extension is 4-6 mm, the welding wire retraction amount and feed amount are 1-3 mm, 100% argon protection, the gas flow rate is 16-24 L / min, the welding current increases to 100-120 A when the welding wire is fed downward, and decreases to 30-60 A when the welding wire is retracted, the negative pressure arc adsorption force is -60--120 Pa, the strength of the applied longitudinal magnetic field is 0.24-0.32 T, and the voltage is 45-80 V.

4. The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing according to claim 1, characterized in that: The process parameters of the negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method are as follows: welding, galvanized duplex steel plate as the workpiece, the workpiece thickness is 6 mm, the preheating temperature is 30-80 ° C, the high-strength steel wire is the wire, the wire diameter is 3 mm, the height between the wire tip and the workpiece is 3 mm, the wire feeding speed is 12-18 m / min, the welding speed is 20-30 mm / s, the wire dry extension is 6-8 mm, and the wire retraction and feed amounts are 3-6 mm; 100% helium protection, the gas flow rate is 14-20 L / min, the welding current increases to 160-240 A when the welding wire is fed downward, and decreases to 40-100 A when the welding wire is retracted, the negative pressure arc adsorption force is -160--240 Pa, the strength of the applied longitudinal magnetic field is 0.28-0.36 T, and the voltage is 6-18 V.

5. The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing according to claim 1, characterized in that: The type of the shielding gas in step 3 is 100% argon, or 100% helium, or a mixture of argon and carbon dioxide, and the gas flow rate is 8 to 38 L / min.

6. The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing according to claim 1, characterized in that: The method is applicable to aluminum alloy materials, or alloy steel materials, or magnesium alloy materials, or titanium alloy materials, or molybdenum alloy materials, or copper alloy materials, or aluminum-copper dissimilar materials, or aluminum-steel dissimilar materials, or hard alloy materials, or metal-based composite materials.

7. The method of negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing according to claim 1, characterized in that: The method of applying the external longitudinal magnetic field is a pulsed alternating magnetic field method; the mode of the external longitudinal magnetic field is a longitudinal dual magnetic field mode with reversed inside and outside, or a longitudinal dual magnetic field mode with reversed top and bottom; the method is applicable to high entropy alloy materials or medium entropy alloy materials.

Images