CN113798632A - Forming method for arc fuse additive manufacturing - Google Patents
Forming method for arc fuse additive manufacturing Download PDFInfo
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- CN113798632A CN113798632A CN202111033686.0A CN202111033686A CN113798632A CN 113798632 A CN113798632 A CN 113798632A CN 202111033686 A CN202111033686 A CN 202111033686A CN 113798632 A CN113798632 A CN 113798632A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/04—Welding for other purposes than joining, e.g. built-up welding
- B23K9/044—Built-up welding on three-dimensional surfaces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/08—Arrangements or circuits for magnetic control of the arc
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/16—Arc welding or cutting making use of shielding gas
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
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Abstract
The invention discloses a forming method for arc fuse additive manufacturing, which comprises the following steps: respectively fixing the clamp electromagnet and the arc welding gun on a robot, so that different inclination angles exist between the clamp electromagnet and the arc welding gun and a workpiece substrate, and performing arc fuse additive manufacturing under a stable transverse magnetic field generated by the clamp electromagnet; according to the magnetic size of a final formed product, adjusting the magnetic field intensity of the transverse magnetic field to improve weld forming, reduce internal pore defects, refine internal grains and inhibit element segregation; the optimum strength of the transverse magnetic field is positively correlated to the magnetic size of the final shaped product. The invention optimizes the residual stress distribution, reduces or eliminates the micro-pore defect, promotes the heat dissipation of a molten pool, refines the weld joint structure, inhibits element segregation, and comprehensively improves the mechanical property and the corrosion resistance of the electric arc additive component. And the invention adjusts the magnetic field intensity of the transverse magnetic field according to the magnetic size of the final formed product, and fills the blank of the research on the aspect.
Description
Technical Field
The invention belongs to the technical field of additive manufacturing, and particularly relates to a forming method for additive manufacturing of an arc fuse.
Background
The electric arc fuse wire additive manufacturing technology is an advanced manufacturing technology which melts alloy wire materials by taking electric arc as a heat source, and is based on a cold metal transition process, and according to a slicing algorithm of a three-dimensional model and a motion track of a robot, additive forming is built up layer by layer from two dimensions to three dimensions. Compared with laser and electron beam additive manufacturing, the efficiency of the arc fuse additive manufacturing is higher, the limitation of closed space protection is broken through, and the advantages of high efficiency and low cost are increasingly highlighted when large-size and complex components are formed.
At present, the electric arc fuse wire additive manufacturing technology is applied to the fields of stainless steel, die steel, high-strength steel, aluminum alloy, nickel-based alloy, titanium alloy and the like. In order to reduce or eliminate internal porosity defects of the additive component and improve microstructure and mechanical properties, several composite processes such as subsequent heat treatment, subsequent forging, real-time high frequency micro-cast forging, electromagnetic assistance, etc. are also occurring in succession. For example, patent document CN105328317A discloses a method for controlling CO by applying a longitudinal magnetic field2A system for welding spatter rate to reduce spatter during droplet short circuit transition. Patent document CN105798425A discloses a system for controlling the residual stress of TIG welding by applying a longitudinal magnetic field to reduce the temperature gradient of the weld joint and optimize the residual stress distribution. Patent document CN108856973A discloses an arc welding system capable of adjusting the application of a longitudinal magnetic field, and it is desired to improve the welding quality by refining crystal grains by the magnetic field stirring action. Patent document CN110802304A discloses an electromagnetic auxiliary arc additive manufacturing forming device and method, which is intended to support a molten pool by electromagnetic force and reduce residual stress of a welding joint. However, in the prior art, for the research on the device and the method for auxiliary welding by the external magnetic field, the longitudinal magnetic field is mainly adopted, the platform is set up more complexly, the operation flow is complicated, the investment cost is higher, and the external magnetic field optimizes the appearance of the molten pool, refines crystal grains and splashesThe reduction of the rate, the improvement of the residual stress distribution and the like are lack of sufficient test verification.
In addition, in the field of magnetic control auxiliary welding, the transverse magnetic field applied at present is mostly a fixed magnetic field fixed below a metal workpiece and is used for flat plate butt welding. The fixed magnetic field places constraints on the complex configuration of arc fuse additive manufacturing. Moreover, no relation or research between magnetism and magnetic control auxiliary arc fuse additive manufacturing in products is related at present.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a forming method for arc fuse additive manufacturing, which aims to regulate and control the form of an electric arc in the additive process in real time and reduce the momentum of backward liquid flow in a molten pool by applying an in-situ stable transverse magnetic field so as to improve the forming appearance of a welding seam, optimize the residual stress distribution, reduce or eliminate the defect of micro-pores, promote the heat dissipation of the molten pool, refine the welding seam structure, inhibit element segregation and comprehensively improve the mechanical property and the corrosion resistance of an arc additive component. And the magnetic field intensity of the transverse magnetic field is adjusted according to the magnetic size of the final formed product, so that the blank of the research on the aspect is filled.
To achieve the above object, according to one aspect of the present invention, there is provided a forming method for arc fuse additive manufacturing, the method comprising: respectively fixing the clamp electromagnet and the arc welding gun on a robot, so that different inclination angles exist between the clamp electromagnet and the arc welding gun and a workpiece substrate, and performing arc fuse additive manufacturing under a stable transverse magnetic field generated by the clamp electromagnet; according to the magnetic size of a final formed product, adjusting the magnetic field intensity of the transverse magnetic field to improve weld forming, reduce internal pore defects, refine internal grains and inhibit element segregation; the optimal magnetic field strength of the transverse magnetic field is positively correlated with the magnetic size of the final formed product.
Preferably, the adjusting of the magnetic field strength of the transverse magnetic field according to the magnetic size of the final formed product specifically comprises: when the proportion of the face-centered cubic in the final formed product is more than 85%, the magnetic field intensity of a transverse magnetic field generated by the clamp electromagnet at the tail end of the welding wire is less than or equal to 20.7 mT; when the proportion of the body-centered cubic in the final formed product is more than 95%, the magnetic field intensity of the transverse magnetic field generated by the clamp electromagnet at the tail end of the welding wire is 26.4 mT-59.6 mT.
Preferably, the transverse magnetic field generated by the clamp-on electromagnet is obtained by connecting a direct-current excitation power supply to the clamp-on electromagnet, the excitation current of the direct-current excitation power supply is adjusted according to the magnetism of the final formed product, and when the proportion of the face-centered cubic in the final formed product is greater than 85%, the excitation current of the direct-current excitation power supply is less than or equal to 1.5A, and the voltage is less than or equal to 7.45V; when the proportion of the body-centered cubic in the final formed product is more than 95%, the exciting current of the direct-current exciting power supply is 2A-4A, and the voltage is 9.54V-18.18V.
Preferably, the inclination angle between the arc welding gun and the workpiece substrate is 45-60 degrees, and the inclination angle between the magnetic pole of the clamp electromagnet and the workpiece substrate is 120-135 degrees.
Preferably, the diameter of the welding wire in the arc fuse additive manufacturing process is 1.2mm, the dry elongation of the welding wire is 10mm, and the horizontal distance between the tail end point of the welding wire and the center of the magnetic pole is 15-20 mm.
Preferably, the wire feeding speed of the arc fuse additive manufacturing is 5.2-11.5 m/min, the scanning speed is 42-80 cm/min, and the protective gas is 80% argon and 20% CO2The flow rate of the protective gas is 18-20L/min.
Preferably, the suppressing element is a selective suppressing element that suppresses segregation of the oxygen element and the silicon element, and particularly, for 316L, the degrees of suppressing segregation of the oxygen element and the silicon element are 25% and 19%, respectively.
Preferably, the improved weld is formed with increased weld width, reduced weld height, reduced weld zone depth, and shallower weld line depth.
Preferably, before the clamp-type electromagnet is fixed on the robot, the electromagnetic coil of the clamp-type electromagnet and the surfaces of the two magnetic poles are coated with Teflon adhesive tapes.
Preferably, the oxide film on the surface of the workpiece substrate is pretreated before the arc fuse additive manufacturing, wherein the pretreatment is polishing, and the surface of the workpiece substrate is cleaned by acetone to remove oil stains.
In general, at least the following advantages can be obtained by the above technical solution contemplated by the present invention compared to the prior art.
(1) According to the invention, the transverse magnetic field is applied to the electric arc fuse wire additive manufacturing, so that the real-time regulation and control of the electric arc and the flowing molten pool are realized, thereby reducing or eliminating internal pores of the additive component, improving the forming appearance and internal structure of a welding seam, weakening the element segregation degree in the molten pool, and comprehensively improving the mechanical property and the corrosion resistance of the additive component. And the magnetic field intensity of the transverse magnetic field is adjusted according to the magnetic size of the final formed product for the first time, so that the blank of the relation and research on the magnetic property in the product and the additive manufacturing of the magnetic control auxiliary arc fuse wire is made up.
The magnetic field intensity of the optimal transverse magnetic field selected in the invention is positively correlated with the magnetic size of the final formed product. The analysis shows that: when a final product with larger magnetism is formed, under a semisolid state to be solidified in a molten pool, peritectic and eutectic transformation occurs in the middle part of the molten pool, and a liquid phase, a body-centered cubic phase (with magnetism) and a face-centered cubic phase (without magnetism) coexist, wherein the body-centered cubic phase can be acted by a transverse magnetic field to generate an upward electromagnetic attraction force to influence the flow of liquid metal in the molten pool, so that when the magnetism of the final product is larger, a larger magnetic field intensity is required to improve the forming appearance and the internal structure of a welding line and weaken the segregation degree of elements in the molten pool. From the angle analysis of the magnetic field to the deflection of the arc column, it can be known that, under the assistance of a transverse magnetic field with the same strength, when a final product with larger magnetism is formed, the forward deflection angle of the arc column is smaller, which is probably because in the transition of a molten drop at the tail end of a welding wire, the molten drop is influenced by electromagnetic attraction, so that larger 'magnetolorentz force' is needed to deflect the arc column to a proper angle, the energy density of an arc is dispersed, and the impact on a molten pool is reduced. Here, "arc column forward" means that the arc column is directed in the same direction as the travel direction of the welding gun.
(2) In the invention, the backward liquid flow in the molten pool is relieved after the in-situ transverse magnetic field is applied, and the accumulation of liquid metal at the tail part of the molten pool is avoided, thereby improving the forming appearance of the welding seam. Meanwhile, charged particles in the arc deflect the arc column by about 30-40 degrees along the scanning direction due to Lorentz force, and the impact action of the arc on the molten pool and the backward flow force of the molten pool are weakened along with the reduction of energy density. The hump defect caused by early solidification and shrinkage of a welding bead due to too large backward flow of liquid in a molten pool in the original high-speed welding process is avoided, so that the manufacturing efficiency of the large arc fuse additive structural part is improved. Here, the backward flow rate means a flow rate of liquid opposite to the traveling direction of the torch.
(3) In the invention, the arc fuse wire additive manufacturing is carried out under the stable transverse magnetic field generated by the clamp type electromagnet, electromagnetic force for blocking the movement of the arc fuse wire additive manufacturing is generated, and larger backward flow quantity of a molten pool in the high-speed additive manufacturing process is weakened, so that the forming appearance of a weld bead is improved, the surface of the weld bead becomes flat and smooth, the melt width is increased, the residual height is reduced, and the transition of two sides is natural without undercut, thereby obtaining the surface of the weld bead which is more beneficial to the additive of the next layer. In addition, the depth of the welding seam area is reduced, the depth of the fusion line becomes shallow, the profile is changed from a deep groove U shape to a smooth parabola shape, and the floating and overflow of air holes in the material increase process are facilitated.
(4) According to the invention, after the in-situ transverse magnetic field is applied, the selective inhibition of the segregation of oxygen elements and silicon elements is realized, the distribution of Si and O elements is more dispersed, for example, for 316L, the reduction of the highest content is respectively 19% and 25%, and the reduction of Si element is beneficial to inhibiting the generation of Si oxide, so that the generation of cracks caused by refractory oxide inclusion is avoided. The reduction of the O element is beneficial to inhibiting the stress corrosion cracking of the 316L welding seam and reducing the crack propagation rate. Whereas the inhibition for the other elements decreases by less than 1% at the highest content.
(5) Under the real-time action of an external transverse magnetic field, charged particles in the arc generate Lorentz force along the movement direction of the welding gun to drive the charged particles to deflect, so that the arc form and the energy density distribution of the arc are changed, and the impact effect of the plasma arc on a molten pool is weakened. The weakening of plasma jet impact in the process of adding materials in the electric arc fuse wire is beneficial to reducing the depth of a welding seam, promoting air holes to float upwards and escape in time before a molten pool is solidified, and reducing or eliminating the defect of micro air holes remained in the molten pool after the molten pool is solidified.
Drawings
FIG. 1A is a front view of a forming apparatus used in a forming method of arc fuse additive manufacturing provided by the present invention;
FIG. 1B is a side view of a forming apparatus used in a forming method of arc fuse additive manufacturing provided by the present invention;
FIG. 2 is a map of the weld pool topography in examples and comparative examples of the present invention;
FIG. 3 is a view showing the structure of a molten pool in example 1 of the present invention;
FIG. 4 is a diagram showing the segregation of elements in the structure of the molten pool in example 1 of the present invention.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:
1-base, 2-electromagnetic coil, 3-workpiece base plate, 4a-N pole, 4b-S pole, 5-welding wire dry extension, 6-wire feeding wheel, 7-contact nozzle and 8-elbow.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in figures 1A and 1B, the forming device adopted in the forming method for the arc fuse additive manufacturing comprises a base 1, an electromagnetic coil 2, a workpiece substrate 3, two magnetic poles N pole 4a and S pole 4B, a welding wire stem extension 5, a wire feeding wheel 6, a contact tip 7 and a bent pipe 8. Wherein the surfaces of the electromagnetic coil 2 and the N pole 4a and the S pole 4b of the two magnetic poles need to be coated by Teflon adhesive tapes, so that tiny splashing adhesion in the material increase process is prevented, and the end parts of the two magnetic poles are prevented from heating due to the heat radiation effect of a molten pool.
The clamp type electromagnet and the arc welding gun are respectively fixed on a robot through a tooling fixture, the bearing limit of the robot is at least 20kg, and the walking direction of the robot depends on the relative installation positions of an N pole 4a and an S pole 4b on the clamp type electromagnet. The horizontal distance between the tail end point of the welding wire and the center of the magnetic pole is controlled to be 15-20 mm, the diameter of the welding wire is 1.2mm, the dry elongation of the welding wire is 10mm, the inclination angle between the arc welding gun and the workpiece substrate is 45-60 degrees, and the inclination angle between the magnetic pole of the clamp electromagnet and the workpiece substrate is 120-135 degrees. The process parameters of the arc fuse additive manufacturing are set as follows: the wire feeding speed is 5.2-11.5 m/min, the scanning speed is 42-60 cm/min, and the protective gas is 80% argon and 20% CO2The flow rate of the mixed gas is 18-20L/min.
And adjusting the magnetic field intensity of the transverse magnetic field according to the magnetic size of the final formed product, wherein the magnetic field intensity of the transverse magnetic field is positively correlated with the magnetic size of the final formed product. Specifically, the method comprises the following steps: when the proportion of the face-centered cubic in the final formed product is more than 85%, the magnetic field intensity of a transverse magnetic field generated by the clamp electromagnet at the tail end of the welding wire is less than or equal to 20.7 mT; when the proportion of the body-centered cubic in the final formed product is more than 95%, the magnetic field intensity of the transverse magnetic field generated by the clamp electromagnet at the tail end of the welding wire is 26.4 mT-59.6 mT.
The invention adopts a direct current excitation power supply of 220V +/-10% (50Hz/60Hz), and the direct current excitation power supply is started, so that the center areas of the two magnetic poles of the clamp-on electromagnet generate in-situ stable transverse magnetic fields, and the magnetic field intensity of the transverse magnetic fields is in direct proportion to the excitation current. Therefore, the exciting current of the direct-current exciting power supply is adjusted according to the magnetism of the final formed product, and specifically, when the proportion of the face-centered cubic in the final formed product is more than 85%, the exciting current of the direct-current exciting power supply is less than or equal to 1.5A, and the voltage is less than or equal to 7.45V; when the proportion of the body-centered cubic in the final formed product is more than 95%, the exciting current of the direct-current exciting power supply is 2A-4A, and the voltage is 9.54V-18.18V. So that both the arc and the molten bath are in the proper magnetic field strength and direction.
The method comprises the steps of pretreating an oxide film on the surface of a workpiece substrate before arc fuse additive manufacturing, wherein the pretreatment is polishing, and cleaning oil stains on the surface of the workpiece substrate by using acetone.
And then performing arc fuse additive manufacturing in protective gas according to a preset programming path and a preset scanning direction for the robot. The method realizes the real-time electromagnetic regulation and stirring action on the electric arc and the flowing molten pool so as to improve the weld formation, reduce internal pores, refine internal grains and inhibit element segregation, thereby improving the comprehensive mechanical property and corrosion resistance of the additive component.
The technical scheme of the invention is further explained in detail by the following specific examples:
first, it is to be noted that, hereinafter, for the final formed product, the body-centered cubic ratios of 40CrNi2Si2MoVA (300M), 2.25Cr-1Mo-0.25V (2.25Cr), 30CrMnSiNi2A (30Cr) are all more than 95%; the face centered cubic ratio of 316L is greater than 85%.
Example 1
The embodiment provides a forming method for arc fuse additive manufacturing, which is used for forming arc fuse additive manufacturing on 316L stainless steel, and comprises the following steps:
s1 is that the 316L stainless steel substrate 3 is clamped on a working platform, a clamp type electromagnet device and an arc welding gun device are fixed through a tool clamp, the dry extension 5 of a welding wire is set to be 1.2cm, the horizontal distance between the tail end point of the welding wire and the center of a magnetic pole 4 is controlled to be 20mm, the inclination angle of the arc welding gun is 45 degrees, and the inclination angle of the magnetic pole is 135 degrees.
S2 setting exciting current 1.5A and voltage 7.45V on the DC exciting power panel, corresponding to the magnetic field intensity 20.7mT at the end point of the welding wire, checking the magnetic field intensity and magnetic induction line direction at the end point of the welding wire with Gauss meter.
S3, editing the motion track and the motion direction of the robot on the control panel of the robot, setting the scanning speed to be 60cm/min, and trying to run the condition that the robot moves along with the clamp electromagnet and the arc welding gun. Whether the base plate is clamped on the working platform or not is checked, and whether the movement stability of the clamp-type electromagnet is influenced by the electromagnetic force between the clamp-type electromagnet and the base plate in the movement process of the robot is checked.
S4, setting the process parameters of the arc fuse additive 316L stainless steel part as follows: the wire feeding speed is 11.5m/min, and the protective gas is 80% Ar + 20% CO2The flow rate of the mixed gas and the protective gas is 20L/min.
S5, melting 316L stainless steel welding wires by using high-energy-density electric arcs, regulating and controlling the electric arcs and a flowing molten pool in real time by using an in-situ transverse magnetic field, and observing that in the proper magnetic field intensity and magnetic field direction, the electric arc shape deflects along the movement direction, the backward flow of liquid in the molten pool is reduced, and the forming appearance of the surface of a weld bead is improved.
S6, controlling the temperature of the surfacing layer to 200 ℃ by using a thermal imager, continuously stacking the next layer, naturally cooling to room temperature after additive forming, loosening the clamp, and taking down the 316L additive component.
Example 2
The embodiment provides a forming method for arc fuse additive manufacturing, which is used for forming 30CrMnSiNi2A high-strength steel (30Cr) by arc fuse additive manufacturing and comprises the following steps:
s1 preheating a 30CrMnSiNi2A substrate to 3-300 ℃, clamping the substrate on a working platform, fixing a clamp type electromagnet device and an arc welding gun device through a tool clamp, setting the dry extension 5 of a welding wire to be 1.2cm, controlling the horizontal distance between the tail end point of the welding wire and the center of a magnetic pole 4 to be 15mm, controlling the inclination angle of the arc welding gun to be 30 degrees and controlling the inclination angle of the magnetic pole to be 120 degrees.
S2 setting exciting current 4A, voltage 18.18V on DC exciting power panel, corresponding to the magnetic field intensity 59.6mT at the end point of welding wire, checking the magnetic field intensity and magnetic induction line direction at the end point of welding wire with Gauss meter.
S3, editing the motion track and the motion direction of the robot on the control panel of the robot, setting the scanning speed to be 60cm/min, and trying to run the condition that the robot moves along with the clamp electromagnet and the arc welding gun. Whether the base plate is clamped on the working platform or not is checked, and whether the movement stability of the clamp-type electromagnet is influenced by the electromagnetic force between the clamp-type electromagnet and the base plate in the movement process of the robot is checked.
S4 Process parameter for setting arc fuse additive 30CrMnSiNi2A high-strength steel componentThe number is as follows: the wire feeding speed is 8.5m/min, and the protective gas is 80% Ar + 20% CO2The flow rate of the mixed gas and the protective gas is 20L/min.
S5, melting a 30CrMnSiNi2A high-strength steel welding wire by using an electric arc with high energy density, regulating and controlling the electric arc and a flowing molten pool in real time by using an in-situ transverse magnetic field, and observing that the electric arc shape deflects along the movement direction, the backward flowing amount of liquid in the molten pool is reduced and the forming appearance of the surface of a welding bead is improved in the proper magnetic field intensity and magnetic field direction in the high-speed material increase process.
S6, controlling the temperature of the surfacing layer to be 300 ℃ by using a thermal imager, continuously stacking the next layer, loosening the clamp after additive forming, taking down the additive component of 30CrMnSiNi2A, preserving the heat of the exothermic treatment furnace for 4 hours at 600 ℃, and taking out after the furnace is cooled.
Example 3, comparative example 1, comparative example 2
The comparative examples and examples used the same procedure as in example 1, except that the transverse magnetic field applied at the end of the wire had a different magnetic field strength, see in particular table 1 below:
TABLE 1-316L MAGNETIC FIELD STRENGTH METER FOR MAKING ARC FUSE ADDITIVE MATERIAL
It should be noted that the weld bead morphology of comparative example 2, in which the exciting current was 2A, was not good, and the surface roughness was high, mainly due to the increase of arc instability observed during the additive process. As the field current continues to increase, the angle at which the arc column deflects forward increases, causing an increase in the amount of spatter.
Examples 4 to 8 and comparative examples 3 to 4
The comparative examples and examples used the same procedure as in example 2, except that the feedstock and applied transverse magnetic field at the end of the wire had different magnetic field strengths, see table 2 below:
TABLE 2 magnetic field Strength Table in additive manufacturing of arc fuses of different raw materials
Results and analysis:
(1) referring to fig. 2, the weld pool morphologies of the above examples and comparative examples are shown, wherein the optimal magnetic field parameters for additive 300M, 2.25Cr, 30Cr are: 2A (26.4mT), 2A (36.2mT), 4A (59.6 mT). The optimal magnetic field parameter for additive 316L is 1.5A (20.7 mT). And the intensity of the magnetic field is continuously increased under the optimal magnetic field, so that the arc is easy to be unstable, and the forming appearance is uneven. The reason for the analysis is that the flow of the molten pool of the more magnetic material is influenced by the upward electromagnetic attraction force generated after the electromagnet is electrified. Therefore, when the magnetism of the final formed product is larger, a larger magnetic field strength is needed to improve the forming appearance and the internal structure of the weld joint and reduce the element segregation degree in the molten pool.
The improvement on the appearance of the molten pool is specifically as follows: after a transverse magnetic field is applied, the surface of the welding bead becomes flat and smooth, the melt width is increased, the residual height is reduced, and the transition of two sides is natural without undercut, so that the surface of the welding bead which is more favorable for material increase of the next layer is obtained. In addition, the depth of the welding seam area is reduced, the depth of the fusion line becomes shallow, the profile is changed from a deep groove U shape to a smooth parabola shape, and the floating and overflow of air holes in the material increase process are facilitated.
For a 300M metal additive welding seam, as the magnetic field parameter is increased from 0A (0mT) to 2A (26.4mT), the fusion width of the corresponding welding bead is increased from 6.12mm to 7.12mm, the residual height is decreased from 1.99mm to 1.84mm, the fusion depth is decreased from 1.09mm to 0.62mm, when the magnetic field parameter is continuously increased from 2A (26.4mT) to 4A (59.6mT), the fusion width is decreased from 7.12mm to 5.89mm, the residual height is increased from 1.84mm to 1.99mm, and the fusion depth is still maintained at 0.62 mm. Taken together, 2A (26.4mT) is the optimal magnetic field assist parameter for additive 300M.
For 2.25Cr metal additive weld, as the magnetic field parameter is increased from 0A (0mT) to 1.3A (20.7mT), the fusion width of the corresponding weld bead is increased from 5.88mm to 6.46mm, the height is decreased from 1.99mm to 1.71mm, the fusion depth is increased from 0.79mm to 0.86mm, when the magnetic field parameter is increased from 1.3A (20.7mT) to 2A (26.4mT), the fusion width is decreased from 6.46mm to 6.14mm, the height is increased from 1.71mm to 1.90mm, and the fusion depth is increased from 0.86mm to 0.98 mm. Taken together, 2A (26.4mT) is the optimal magnetic field auxiliary parameter for additive 2.25 Cr.
For a 30Cr metal additive weld, as the magnetic field parameter is increased from 0A (0mT) to 2A (26.4mT), the weld width of the corresponding weld bead is increased from 4.81mm to 6.36mm, the weld height is decreased from 1.99mm to 1.50mm, the weld penetration is increased from 0.98mm to 1.07mm, and when the magnetic field parameter is increased from 2A (26.4mT) to 4A (59.6mT), the weld width and weld height are basically kept unchanged, but the weld line of the weld is shallower, and the weld penetration is decreased from 1.70mm to 0.86 mm. Taken together, 4A (59.6mT) is the optimal magnetic field auxiliary parameter for additive 30 Cr.
For a 316L metal additive weld, as the magnetic field parameter is increased from 0A (0mT) to 1A (14.6mT), the fusion width of the corresponding weld bead is increased from 6.36mm to 7.04mm, the residual height is decreased from 3.5mm to 3.1mm, the fusion depth is decreased from 2.29mm to 2.19mm, when the magnetic field parameter is increased from 1A (14.6mT) to 1.5A (20.7mT), the fusion width is basically unchanged, the residual height is decreased from 3.1mm to 2.56mm, and the fusion depth is decreased from 2.18mm to 1.07 mm. Taken together, 1.5A (20.7mT) is the optimal magnetic field assist parameter for additive 316L.
The analysis reason is that the backward liquid flow in the molten pool is relieved after the in-situ transverse magnetic field is applied, and the accumulation of liquid metal at the tail part of the molten pool is avoided, so that the forming appearance of the welding seam is improved. Meanwhile, charged particles in the arc deflect the arc column by about 30-40 degrees along the scanning direction due to Lorentz force, and the impact action of the arc on the molten pool and the backward flow force of the molten pool are weakened along with the reduction of energy density.
(2) Referring to fig. 3 and 4, it can be seen that the impact of the arc on the bath is reduced with a concomitant reduction in energy density; with the increase of the magnetic field intensity, the element segregation degree at the bottom of the molten pool is weakened, specifically, after the magnetic field is applied, the Si and O elements are distributed more dispersedly, the reduction amplitude at the highest content position is respectively 19% and 25%, the reduction of the Si element is beneficial to inhibiting the generation of the oxide of Si, thereby avoiding the generation of cracks caused by refractory oxide inclusion. The reduction of the O element is beneficial to inhibiting the stress corrosion cracking of the 316L welding seam and reducing the crack propagation rate.
That is to say, in the invention, after the in-situ transverse magnetic field is applied, the selective inhibition of the segregation of the oxygen element and the silicon element is realized, the distribution of the Si and O elements is more dispersed, and the inhibition of other elements is reduced by less than 1% at the highest content position.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method of shaping for arc fuse additive manufacturing, the method comprising:
respectively fixing the clamp electromagnet and the arc welding gun on a robot, so that different inclination angles exist between the clamp electromagnet and the arc welding gun and a workpiece substrate, and performing arc fuse additive manufacturing under a stable transverse magnetic field generated by the clamp electromagnet;
according to the magnetic size of a final formed product, adjusting the magnetic field intensity of the transverse magnetic field to improve weld forming, reduce internal pore defects, refine internal grains and inhibit element segregation; the optimal magnetic field strength of the transverse magnetic field is positively correlated with the magnetic size of the final formed product.
2. The forming method according to claim 1, wherein the adjusting of the magnetic field strength of the transverse magnetic field according to the magnetic size of the final formed product is carried out by:
when the proportion of the face-centered cubic in the final formed product is more than 85%, the magnetic field intensity of a transverse magnetic field generated by the clamp electromagnet at the tail end of the welding wire is less than or equal to 20.7 mT;
when the proportion of the body-centered cubic in the final formed product is more than 95%, the magnetic field intensity of the transverse magnetic field generated by the clamp electromagnet at the tail end of the welding wire is 26.4 mT-59.6 mT.
3. The forming method according to claim 2, wherein the transverse magnetic field generated by the clamp-type electromagnet is obtained by connecting a DC excitation power supply to the clamp-type electromagnet, the excitation current of the DC excitation power supply is adjusted according to the magnetic strength of the final formed product,
when the proportion of the face-centered cubic in the final formed product is more than 85%, the exciting current of the direct-current exciting power supply is less than or equal to 1.5A, and the voltage is less than or equal to 7.45V;
when the proportion of the body-centered cubic in the final formed product is more than 95%, the exciting current of the direct-current exciting power supply is 2A-4A, and the voltage is 9.54V-18.18V.
4. The forming method according to any one of claims 1 to 3, wherein an inclination angle between the arc welding gun and the workpiece substrate is 45 ° to 60 °, and an inclination angle between the magnetic pole of the clamp electromagnet and the workpiece substrate is 120 ° to 135 °.
5. The forming method of claim 1, wherein the wire diameter in the arc fuse additive manufacturing is 1.2mm, the dry elongation of the wire is 10mm, and the horizontal distance between the end point of the wire and the center of the magnetic pole is 15-20 mm.
6. The forming method of claim 1, wherein the wire feed speed of the arc fuse additive manufacturing is 5.2-11.5 m/min, the scanning speed is 42-80 cm/min, and the protective gas is 80% argon and 20% CO2The flow rate of the protective gas is 18-20L/min.
7. The forming method of claim 1, wherein the inhibiting the segregation of the element is selectively inhibiting segregation of an oxygen element and a silicon element.
8. The method of claim 1, wherein the improved weld formation is an increased weld width, a decreased weld head height, and a reduced weld zone depth, with a shallower weld line depth.
9. The method of claim 1, wherein the surfaces of the electromagnetic coil and the two magnetic poles of the jaw electromagnet are covered with teflon tape before the jaw electromagnet is fixed to the robot.
10. The forming method according to claim 1, wherein the pretreatment of the oxide film on the surface of the workpiece substrate before the arc fuse additive manufacturing is performed is polishing and cleaning the surface of the workpiece substrate with acetone to remove oil stains.
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