Negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method

Abstract

The present invention provides a negative pressure arc cold metal transition thermal coordinated welding and additive manufacturing method, including: preparation before welding, setting CMT process parameters and adjusting the relative position of the welding gun, setting the CMT power supply and turning on the shielding gas, controlling and applying an adaptive negative pressure arc adsorption force according to the CMT current waveform and the droplet transition state, and completing the negative pressure arc cold metal transition thermal coordinated welding or additive manufacturing process; through the above steps, the appropriate anti-impact force and anti-gravity negative pressure arc adsorption force is accurately applied during the droplet transition process, reducing the splashing of droplets of conventional positive pressure arcs and reducing the impact of droplets on the molten pool, so that the droplets enter the molten pool more smoothly and with lower heat input, achieving the thermal coordinated behavior of negative pressure arc cold metal transition welding and additive manufacturing, and obtaining better welding or additive manufacturing formative quality.

Description

Technical Field

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

[0002] Arc welding technology and arc additive manufacturing technology are welding technology and additive manufacturing technology that use arc as a heat source. Due to the characteristics of strong conductivity, concentrated energy and high temperature of the arc, arc welding technology and arc additive manufacturing technology have the advantages of high efficiency and low cost. However, due to the large heat input, it is often easy to cause 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 to cause deformation or burn-through of the thin-walled structure due to excessive heat input, which in turn leads to scrapping of the workpiece.

[0003] Cold Metal Transfer (CMT) technology has been widely studied and applied in the fields of welding and additive manufacturing due to its characteristics of no spatter, extremely low heat input and stable arc. In response to the above problems, arc welding and additive manufacturing technologies based on cold metal transfer have been formed. Compared with traditional technologies, CMT arc welding or additive manufacturing technology can achieve low heat input, stable arc and precise fuse amount control, which completely breaks the current research status of traditional arc welding or additive manufacturing technology that is difficult to break through for 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 impact of the droplet 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 a 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 the internal residual stress to continue to increase, and there are thermal-mechanical defects. It is difficult to obtain a good balance between heat and force, which has an adverse effect on the formative quality of additive manufacturing.

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

[0006] To solve the above problems, the purpose of the present invention is to propose a negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method, which reduces the splashing of droplets in conventional positive pressure arcs and the impact of droplets on the molten pool by accurately applying appropriate anti-impact force and anti-gravity negative pressure arc adsorption force during the droplet transition process, 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, and obtaining better welding or additive manufacturing formative quality.

[0007] The above purpose is achieved through the following technical solutions:

[0008] A negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method, 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 workpiece to be welded or the additive manufacturing substrate after grinding or cleaning;

[0010] Step 2: Set 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, and determine the parameters of the appropriate process;

[0011] Step 3: Set the CMT power supply and turn on the protective gas: open the gas protection valve, and then turn on the CMT power supply;

[0012] Step 4: According to the CMT current waveform and the droplet transition state, control and apply the adaptive negative pressure arc adsorption force: adjust the CMT parameters through the control system, and according to the current waveform and the droplet transition state, form and adjust the action time, duration, frequency and size of the negative pressure arc adsorption force by applying an external longitudinal magnetic field. The specific process is as follows:

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

[0014] (2) The wire is retracted to promote the separation of the molten drop 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, overcoming the critical gravity Fg1 and impact force of the downward molten drop transition, reducing the splash of the molten drop in the conventional positive pressure arc, reducing the impact of the molten drop on the molten pool, allowing the molten drop to enter the molten pool smoothly with low heat input, realizing the thermal synergy process of negative pressure arc cold metal transition welding or additive manufacturing, achieving the good effect of thermal synergy of smooth and controllable molten drop transition without impact, splashing, and low heat, and 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 a 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 thermal coordination 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 minimum value time 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 0.8-6 mm, the height of the welding wire tip from the workpiece or substrate is 2-6 mm, the wire feeding speed is 0.1-40 m / min, the welding speed is 10-600 mm / s, the dry extension of the welding wire is 2-10 mm, and the wire retraction amount and feed amount are 1-10 mm;

[0019] Further, the type of protective gas in step 3 is 100% argon, or 100% helium, or a mixed gas of argon + carbon dioxide, or carbon dioxide, 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, the negative pressure arc adsorption force in step 4 can be generated, adjusted, changed and controlled by adjusting the strength, frequency, duty cycle and mode of the external longitudinal magnetic field and matching it with the arc current, wherein the strength 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 the atmospheric pressure, and the external longitudinal magnetic field mode is a continuous alternating magnetic field mode, an intermittent alternating magnetic field mode, or a pulsed alternating magnetic field mode; the external longitudinal magnetic field mode is a fixed longitudinal magnetic field mode, a rotating longitudinal magnetic field mode, an inverted longitudinal dual magnetic field mode, or an inverted longitudinal dual magnetic field mode;

[0021] Furthermore, the CMT current in step 4 shows a one-to-one negative correlation with the negative pressure arc adsorption force, and the change pattern repeats over time until the 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.

[0023] The beneficial effects of the present invention are as follows: by accurately applying appropriate anti-impact force and anti-gravity negative pressure arc adsorption force 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, thereby achieving thermal synergy of negative pressure arc cold metal transition welding or additive manufacturing, reducing residual stress caused by repeated alternation of hot and cold during arc additive manufacturing printing, and reducing deformation and even burn-through defects caused by thermal incoordination for thin-walled structures and even ultra-thin-walled structures, thereby achieving better welding or additive manufacturing formative quality.

[0024] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a graph showing the relationship between welding current and negative pressure arc adsorption force over time of the present invention;

[0026] Figure 2 This is a force analysis diagram of the droplet growth process of the present invention;

[0027] Figure 3 It is a force analysis diagram of the droplet transfer process of the present invention;

[0028] Figure numerals: 1 workpiece or additive manufacturing 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 adsorption force; Fem is the electromagnetic force. DETAILED DESCRIPTION

[0029] The following embodiments of the present invention are described in further detail in conjunction with 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.

[0030] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Combine the following Figures 1 to 3 The invention provides a negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method, comprising the following steps:

[0033] 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.

[0034] Step 2: Set 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;

[0035] Step 3: Set the CMT power supply and turn on the protective gas: open the gas protection valve, and then turn on the CMT power supply;

[0036] Step 4: According to the CMT current waveform and the droplet transition state, control and apply the adaptive negative pressure arc adsorption force: adjust the CMT parameters through the control system, and according to the current waveform and the droplet transition state, form and adjust the action time, duration, frequency and size of the negative pressure arc adsorption force by applying an external longitudinal magnetic field. The specific process is as follows:

[0037] (1) The welding wire 2 is fed downward, the current is increased, the arc 3 is ignited, the tip of the welding wire 2 is melted, and the molten drop 4 gradually grows under the upward surface tension Fs and the electromagnetic force Fem that promotes the drop 4 to fall off, and the initial gravity Fg0 of the molten drop 4 gradually increases;

[0038] (2) The welding wire 2 is retracted to promote the separation of the molten drop 4 from the welding wire 2 and start to fall, and the current decreases and reaches the minimum value. At this moment, an external longitudinal magnetic field is applied to form an adsorption force Fi in the opposite direction to gravity, which overcomes the critical gravity Fg1 and impact force of the molten drop transition in the downward direction, reduces the splashing of the molten drop 4 of the conventional positive pressure arc, reduces the impact of the molten drop 4 on the molten pool 5, and makes the molten drop 4 enter the molten pool 5 smoothly with low heat input, realizing the thermal synergy process of negative pressure arc cold metal transition welding or additive manufacturing, achieving the good effect of thermal synergy of smooth and controllable transition of the molten drop without impact, splashing and low heat, and obtaining better welding or additive manufacturing formative quality;

[0039] (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;

[0040] Step 5: Complete the negative pressure arc cold metal transfer thermal coordination 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.

[0041] More specific embodiments are as follows:

[0042] 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. Figure 1 The negative-pressure arc adsorption force here only refers to its size. 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, and 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, and is inversely proportional to the transition speed of the molten droplet 4 and the distance from the surface of the molten pool 5.

[0043] In step 2, the welding wire diameter is 0.8-6 mm, the height of the welding wire tip from the workpiece or substrate is 2-6 mm, the wire feeding 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 amount and feed amount are 1-10 mm.

[0044] The type of protective gas in step 3 is 100% argon, or 100% helium, or a mixed gas of argon + carbon dioxide, or carbon dioxide gas, or a quaternary mixed gas mainly composed of argon + helium + a small amount of hydrogen + a small amount of oxygen, or a ternary mixed gas mainly composed of argon + helium + a small amount of oxygen, and the gas flow rate is 8 to 38 L / min.

[0045] In step 4, the negative pressure arc adsorption force can be generated, adjusted, changed and controlled by adjusting the strength, frequency, duty cycle and mode of the external longitudinal magnetic field and matching it with the arc current, wherein the strength 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, 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 external longitudinal magnetic field mode is a fixed longitudinal magnetic field mode, a rotating longitudinal magnetic field mode, an inverted longitudinal dual magnetic field mode, or an inverted up and down longitudinal dual magnetic field mode.

[0046] The CMT current in step 4 shows a one-to-one negative correlation with the negative pressure arc adsorption force, 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.

[0047] 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 hard alloy materials, or rare metal materials, or refractory metal materials, or high entropy alloy materials, or medium entropy alloy materials, or metal-based composite materials.

[0048] Embodiment 1

[0049] The negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method of this embodiment specifically includes the following steps:

[0050] The first step is preparation before additive manufacturing: use 2219 aluminum alloy as a substrate, polish or clean the 2219 aluminum alloy, and fix the polished or cleaned 2219 aluminum alloy. The thickness of the substrate 1 is 1.5 mm and the preheating temperature is 30-80°C.

[0051] The second step is to 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, determine the parameters of the appropriate process, select 2219 aluminum alloy welding wire as the wire material, the diameter of the welding wire 2 is 1.2mm, the height of the tip of the welding wire 2 from the substrate 1 is 2.5mm, the wire feeding speed is 15-21m / min, the welding speed is 26-100mm / s, the dry extension of the welding wire 2 is 2-4mm, and the retraction amount and feed amount of the welding wire 2 are 2-3mm;

[0052] The third step is to set the CMT power supply and start the protective gas: open the gas protection valve, then turn on the CMT power supply, 100% argon protection, and the gas flow rate is 17-20L / min;

[0053] The fourth step is to control and apply an adaptive negative pressure arc adsorption force according to the CMT current waveform and the droplet transition state: the CMT parameters are adjusted through the control system, and the action time, duration, frequency and size 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) Figure 2 As shown, the welding wire 2 is fed downward, and the current is increased to 90-110A, so that the arc 3 is ignited, and the tip of the welding wire 2 melts. Under the upward surface tension Fs and the electromagnetic force Fem that promotes the detachment of the molten droplet 4, the molten droplet 4 gradually grows, and the initial gravity Fg0 of the molten droplet gradually increases; (2) Figure 3 As shown, the welding wire 2 is retracted to promote the molten drop 4 to separate from the welding wire 2 and start to fall, and the current is reduced to 25-50A. At this moment, an external longitudinal magnetic field is applied to form an upward adsorption force Fi opposite to gravity, with a magnitude of -30-80Pa, which overcomes the critical gravity Fg1 and impact force of the downward molten drop transition, reduces the splashing of the molten drop 4 of the conventional positive pressure arc, reduces the impact of the molten drop 4 on the molten pool 5, and makes the molten drop 4 smoothly enter the molten pool 5 with low heat input, realizing the thermal synergy process of negative pressure arc cold metal transition welding or additive manufacturing, achieving the good effect of thermal synergy of smooth and controllable molten drop transition without impact, splashing, and low heat, and obtaining 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 drop 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 external longitudinal magnetic field strength, frequency, duty cycle, mode and matching it with the arc current, so as to generate, adjust, change and control the size, action duration, action time and action frequency of the negative pressure arc adsorption force. The external longitudinal magnetic field strength is 0.12~0.18T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, and the magnetic field mode is a longitudinal intermittent alternating magnetic field mode.

[0054] like Figure 1 As shown in the figure, 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 consistent with the CMT current frequency, the action time of the negative pressure arc adsorption force is consistent with the minimum value time of the CMT current, and 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, which 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 law repeats over time until the additive manufacturing is completed, and the voltage is 18 to 22V.

[0055] The fifth step is to complete the negative pressure arc cold metal transfer thermal coordinated 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.

[0056] Embodiment 2

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

[0058] The first step is 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 the substrate 1 is 2.5 mm and the preheating temperature is 30 to 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 a suitable height, select the appropriate welding wire, determine the parameters of the appropriate process, select 6061 welding wire as the wire material, the diameter of welding wire 2 is 2.4mm, the height of the tip of welding wire 2 from the substrate 1 is 5mm, the wire feeding speed is 4-8m / min, the welding speed is 8-15mm / s, the dry extension of welding wire 2 is 4-6mm, and the retraction amount and feed amount of welding wire 2 are 1-3mm;

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

[0061] The fourth step is to control and apply an adaptive negative pressure arc adsorption force according to the CMT current waveform and the droplet transition state: the CMT parameters are adjusted through the control system, and the action time, duration, frequency and size 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) Figure 2 As shown, the welding wire 2 is fed downward, and the current is increased to 100-120A, so that the arc 3 is ignited, and the tip of the welding wire 2 melts. Under the upward surface tension Fs and the electromagnetic force Fem that promotes the detachment of the molten droplet 4, the molten droplet 4 gradually grows, and the initial gravity Fg0 of the molten droplet gradually increases; (2) as Figure 3As shown, the welding wire 2 is retracted to promote the separation of the molten drop 4 from the welding wire 2 and start to fall, and the current is reduced to 30-60A. At this moment, an external longitudinal magnetic field is applied to form an upward adsorption force Fi opposite to gravity, with a magnitude of -60--120Pa, which overcomes the critical gravity Fg1 and impact force of the downward molten drop transition, reduces the splashing of the molten drop 4 of the conventional positive pressure arc, reduces the impact of the molten drop 4 on the molten pool 5, and makes the molten drop 4 enter the molten pool 5 smoothly with low heat input, realizing the thermal synergy process of negative pressure arc cold metal transition additive manufacturing, achieving the good effect of thermal synergy of smooth and controllable molten drop transition without impact, splashing, and low heat, and obtaining 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 drop 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 external longitudinal magnetic field strength, frequency, duty cycle, mode and matching it with the arc current, so as to generate, adjust, change and control the size, action duration, action time and action frequency of the negative pressure arc adsorption force. The external longitudinal magnetic field strength is 0.24~0.32T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, and the magnetic field mode is a longitudinal continuous alternating magnetic field mode.

[0062] like Figure 1 As shown in the figure, 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 consistent with the CMT current frequency, the action time of the negative pressure arc adsorption force is consistent with the minimum value time of the CMT current, and 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, which 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 law repeats over time until the additive manufacturing is completed, and the voltage is 45-80V.

[0063] The fifth step is to complete the negative pressure arc cold metal transfer thermal coordinated 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.

[0064] Embodiment 3

[0065] The negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method of this embodiment specifically includes the following steps:

[0066] The first step is preparation before welding: the galvanized duplex steel plate is used as workpiece 1, the galvanized duplex steel plate is polished or cleaned of stains, and the polished or cleaned galvanized duplex steel plate is fixed. The thickness of the workpiece 1 is 6 mm and the preheating temperature is 30-80°C;

[0067] The second step is to 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, use high-strength steel welding wire as the wire material, the diameter of welding wire 2 is 3mm, the height of welding wire 2 tip from the workpiece is 3mm, the wire feeding speed is 12-18m / min, the welding speed is 20-30mm / s, the dry extension of welding wire 2 is 6-8mm, and the retraction and feed amount of welding wire 2 is 3-6mm;

[0068] The third step is to set the CMT power supply and start the protective gas: open the gas protection valve, then turn on the CMT power supply, 100% helium protection, and the gas flow rate is 14-20L / min;

[0069] The fourth step is to control and apply an adaptive negative pressure arc adsorption force according to the CMT current waveform and the droplet transition state: the CMT parameters are adjusted through the control system, and the action time, duration, frequency and size 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) Figure 2 As shown, the welding wire 2 is fed downward, and the current is increased to 160-240A, so that the arc 3 is ignited, and the tip of the welding wire 2 melts. Under the upward surface tension Fs and the electromagnetic force Fem that promotes the detachment of the molten droplet 4, the molten droplet 4 gradually grows, and the initial gravity Fg0 of the molten droplet gradually increases; (2) Figure 3 As shown, the welding wire 2 is retracted to promote the separation of the molten drop 4 from the welding wire 2 and start to fall, and the current is reduced to 40-100A. At this moment, an external longitudinal magnetic field is applied to form an upward adsorption force Fi opposite to gravity, with a magnitude of -160--240Pa, which overcomes the critical gravity Fg1 and impact force of the downward molten drop transition, reduces the splashing of the molten drop 4 of the conventional positive pressure arc, reduces the impact of the molten drop 4 on the molten pool 5, and makes the molten drop 4 smoothly enter the molten pool 5 with low heat input, realizing the thermal synergy process of negative pressure arc cold metal transition welding, achieving the good effect of thermal synergy of smooth and controllable molten drop transition without impact, splashing, and low heat, and obtaining 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 drop 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 external longitudinal magnetic field strength, frequency, duty cycle, mode and matching it with the arc current, so as to generate, adjust, change and control the size, action duration, action time and action frequency of the negative pressure arc adsorption force. The external longitudinal magnetic field strength is 0.28~0.36T, the negative pressure arc adsorption force is based on the relative pressure of atmospheric pressure, and the magnetic field mode is a longitudinal continuous alternating magnetic field mode.

[0070] like Figure 1As shown in the figure, 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 minimum value time of the CMT current, and 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, which 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 law repeats over time until the welding is completed. The voltage is 6 to 18V.

[0071] 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.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method, 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 workpiece to be welded or the additive manufacturing substrate after grinding or cleaning; Step 2: Set 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, and determine the parameters of the appropriate process; In step 2, the welding wire diameter is 0.8-6 mm, the height of the welding wire tip from the workpiece or substrate is 2-6 mm, the wire feeding 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 amount and feed amount are 1-10 mm; Step 3: Set the CMT power supply and turn on the protective gas: open the gas protection valve, and then turn on the CMT power supply; Step 4: According to the CMT current waveform and the droplet transition state, control and apply the adaptive negative pressure arc adsorption force: adjust the CMT parameters through the control system, and according to the current waveform and the droplet transition state, form and adjust the action time, duration, frequency and size of the negative pressure arc adsorption force by applying an external longitudinal magnetic field. The specific process is as follows: (1) The welding wire is fed downward, the current is increased, the arc is ignited, the tip of the welding wire melts, and 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 and in an upward direction, realizing the thermal synergy process of negative pressure arc cold metal transfer 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 arc adsorption force is in an upward direction, 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 minimum value time 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 law 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 applied longitudinal magnetic field strength is 0.02 to 0.36 T, and the negative pressure arc adsorption force is a relative pressure based on atmospheric pressure; Step 5: Complete the negative pressure arc cold metal transfer thermal coordination 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. A negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method according to claim 1, characterized in that: The process parameters of the negative pressure arc cold metal transition thermal synergistic welding or additive manufacturing method are as follows: additive manufacturing, 2219 aluminum alloy is used as the substrate, the substrate thickness is 1.5 mm, the preheating temperature is 30-80°C, 2219 aluminum alloy welding wire is used as the wire material, the welding wire diameter is 1.2 mm, the height of the welding wire tip from 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 elongation is 2-4 mm, the welding wire retraction amount and feed amount are 2-3 mm, 100% argon protection, 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 the welding current decreases when the welding wire is retracted, the negative pressure arc adsorption force is -30--80 Pa, the external longitudinal magnetic field strength is 0.12-0.18 T, and the voltage is 18-22 V.

3. A negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method according to claim 1, characterized in that: The process parameters of the negative pressure arc cold metal transition thermal synergistic welding or additive manufacturing method are as follows: additive manufacturing, 6061 aluminum alloy is used as a substrate, the substrate thickness is 2.5 mm, the preheating temperature is 30-80°C, 6061 aluminum alloy welding wire is used as wire material, the welding wire diameter is 2.4 mm, the height of the welding wire tip from the substrate is 5 mm, the wire feeding speed is 4-8 m / min, the welding wire dry elongation 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 the welding current decreases to 30-60 A when the welding wire is retracted, the negative pressure arc adsorption force is -60--120 Pa, and the applied longitudinal magnetic field strength is 0.24-0.32 T.

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

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

6. A negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method according to claim 1, characterized in that: The external longitudinal magnetic field mode is a pulse alternating magnetic field mode.

7. A negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method according to claim 1, characterized in that: The external longitudinal magnetic field mode is a continuous alternating magnetic field mode.

8. The negative pressure arc cold metal transfer thermal synergistic welding or additive manufacturing method according to claim 1, characterized in that: The external longitudinal magnetic field mode is an intermittent alternating magnetic field mode.

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