CN106987838B - Laser cladding device and method for removing air holes/inclusions of laser cladding layer - Google Patents

Abstract

The invention belongs to the technical field of laser material processing, and in particular relates to a laser cladding device for removing air holes/inclusions of a laser cladding layer, which comprises a workbench, a laser cladding powder feeder arranged in front of the workbench and a laser composite processing head positioned above the workbench, wherein the laser composite processing head comprises an electrode, an induction coil, a laser light guide cylinder, a magnet, a working magnetic pole I and a working magnetic pole II, the magnet provides an alternating magnetic field between the working magnetic pole I and the working magnetic pole II to act on the surface of a workpiece, the laser cladding powder feeder adds laser cladding materials to the surface of the workpiece, and the laser outputs a laser beam to perform laser cladding on the surface of the workpiece. The invention also discloses a laser cladding method for removing the air holes/inclusions of the laser cladding layer. The invention can reduce air holes and nonmetallic inclusions in the aluminum alloy laser cladding layer, obviously improve the quality of the laser cladding layer and has important application value.

Description

Laser cladding device and method for removing pores/inclusions in laser cladding layer

technical field

The invention belongs to the technical field of laser material processing, and more specifically relates to a laser cladding device and method for removing air holes/inclusions in a laser cladding layer.

Background technique

The pores in the laser cladding layer are common defects, which have a great impact on the quality of the cladding layer. There are many reasons for the pores. Laser cladding porosity is easy to occur. Even in the case of automatic powder feeding, for laser cladding of high-carbon alloys, copper alloys, aluminum alloys, etc., pores in the cladding layer are prone to occur.

At present, there are two ways to avoid pores in the laser cladding layer. The first one is the self-fluxing alloy using B, Si, etc. as a deoxidizer. , B, Si have certain side effects. The second is inert gas protection. The advantage of this method is that it does not change the normal alloy composition of the cladding layer; the disadvantage is that the protection effect is limited.

The above two methods of preventing pores in the cladding layer are mainly applicable to commonly used alloy steels. For copper and aluminum alloys with high thermal conductivity, the problem of pores in the laser cladding layer has been difficult to solve because the laser melting of copper and aluminum alloys The pores in the cladding are mainly caused by hydrogen; and this type of alloy has good thermal conductivity, fast solidification speed, and it is difficult for the gas in the molten pool to escape, so it is easier to form pores. Taking aluminum alloy as an example, the pore formation mechanism is as follows: the hydrogen concentration dissolved in the liquid metal is high at high temperature (0.69ml/g), and the hydrogen concentration dissolved in the solid drops sharply at low temperature (0.036ml/g). In this state, the solubility of aluminum alloy is reduced by about 20 times before and after solidification, which is one of the main reasons for the easy generation of pores in aluminum alloy welds.

The non-metallic inclusions in the aluminum melt are mainly Al ₂ O ₃ , and the influence of the inclusions on the properties of the aluminum alloy is reflected in the following aspects: ① Significantly reduce the mechanical properties and stress corrosion resistance of the material; ② form in the material Defects such as slag inclusions and oxide films reduce product quality; ③Adsorb gas and block the diffusion and precipitation of gas, resulting in porosity and pores. Since Al ₂ O ₃ and other non-metallic inclusions in the aluminum melt have strong hydrogen absorption capacity, when the adsorbed hydrogen atoms increase, bubbles will gather on the surface of the inclusions. The density of non-metallic inclusions Al ₂ O ₃ (density 3.96g/cm ³ ), MgO (density 3.58g/cm ³ ), SiO ₂ (density 2.65g/cm ³ ), etc. after attaching hydrogen bubbles is similar to that of aluminum melt (density 2.3 ~ 2.4g/cm ³ ), it can be suspended in different positions of the melt. Therefore, inclusions must be removed while removing hydrogen from aluminum alloys.

At present, in addition to laser cladding and laser rapid prototyping in a vacuum box or an inert gas chamber, the pores in the aluminum alloy automatic powder feeding laser cladding layer in the atmospheric environment are still unavoidable, and the situation is relatively serious.

In addition, scholars at home and abroad have also conducted useful research on the influence of magnetic fields on the properties of metals in the molten pool by laser action. O. Velde et al. studied the effect of the Lorentz force of the static magnetic field on the molten pool during the alloying process of the aluminum alloy surface. Effects of Marangoni on flow and solute distribution. M. Bachmann et al. studied the effects of permanent magnet static magnetic field and electromagnet alternating magnetic field on improving the cross-section and surface morphology of aluminum alloy welds and suppressing spatter during welding. The invention patent "static magnetic field-laser coaxial composite cladding method and device (application number 201310755461.5)" published in 2013 uses a static magnetic field device to achieve a smooth effect on the flow of the molten pool caused by the laser, thereby achieving regulation and control of the solidification structure and improvement of melting. Surface morphology of cladding, optimization of stress distribution, reduction of spatter during cladding, etc.; the invention patent "A method and device for electro-magnetic composite field synergistic laser cladding (application number 201410392196.3)" published in 2014, The applied electric field and external magnetic field are coupled in the workpiece at the same time, so that the conductive fluid in the molten pool area is affected by the synergistic effect of the electric-magnetic compound field, and the heat and mass transfer behavior in the laser cladding process can be regulated to achieve the convection tendency of the molten pool control, to achieve the purpose of regulating the solidification structure, optimizing the mechanical properties of the workpiece, adjusting the distribution of solute elements or external hard phases, and improving the surface morphology of the cladding layer; the invention patent "an alternating magnetic field to refine the laser cladding layer" was published in 2012 Method and device for solidification structure (application number: 201210225593.2)", by placing a coil device on the surface of the workpiece, using an alternating magnetic field to change the solidification structure of the cladding layer and refine the grains. However, the above-mentioned studies are all conducted on the use of magnetic fields to improve the surface morphology and microstructure of the cladding layer itself, and reduce spatter, etc., and do not involve the removal of pores and inclusions in the laser cladding layer.

Due to the above-mentioned defects and deficiencies, further improvement and improvement are urgently needed in this field, and a device and method for removing pores/inclusions in the laser cladding layer is designed to meet the requirements of impurity removal for various types of melts during laser cladding. need.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a laser cladding device and method for removing pores/inclusions in the laser cladding layer, which uses a specially designed alternating magnetic field for laser-induction composite cladding, Through the electromagnetic force induced by the charged particles in the alternating magnetic field, the pores and inclusions in the cladding layer can be assisted to remove, which can significantly reduce the pores and non-metallic inclusions in the aluminum alloy laser cladding layer, and significantly improve the laser cladding layer. Quality, to meet the needs of laser cladding of different types of workpieces.

In order to achieve the above object, according to one aspect of the present invention, a laser cladding device for removing pores and inclusions in the laser cladding layer is provided, which is characterized in that it includes a workbench, a laser cladding device arranged in front of the workbench The powder feeder and the laser composite processing head above the workbench,

Wherein, the workpiece is placed on the workbench, and the laser composite processing head includes an electrode, an induction coil, a laser light guide cylinder, a magnet, a working magnetic pole I and a working magnetic pole II, and the working magnetic pole I and the working magnetic pole II are relatively arranged on the One end of the magnet, and there is a certain gap between each other, the laser light guide tube and the workpiece are respectively located directly above and directly below the gap between the working magnetic pole I and the working magnetic pole II, and the bottom of the working magnetic pole I and the working magnetic pole II There is a certain distance from the surface of the workpiece, and the beam at the other end of the magnet is covered with an induction coil, and the two ends of the induction coil protrude to connect with the electrodes. The alternating magnetic field acts on the surface of the workpiece,

The laser cladding powder feeder adds laser cladding materials to the surface of the workpiece, and the laser cladding device also includes a laser, which outputs a laser beam through an optical path system and a laser light guide tube, and the laser beam passes through the working magnetic pole The gap between I and the working pole II is irradiated on the surface of the workpiece for laser cladding.

Specifically, the laser cladding powder feeder automatically delivers the laser cladding material to the surface of the substrate through the powder feeding nozzle, supplementing it while cladding, which can make the material clad gradually and make it easier for gas and inclusions to flow from the cladding metal discharge. The laser outputs the laser beam to the surface of the substrate through the optical path system for laser cladding, the induction power supply applies an alternating magnetic field to the substrate and the cladding layer through the working magnetic pole, and the control system controls the on, off and on of the laser, laser cladding powder feeder and induction power Relevant process parameters when it works.

Further preferably, the laser cladding device also includes a numerical control system and an induction power supply connected to the electrodes, the numerical control system controls the laser, the laser cladding powder feeder, the induction power supply and the workbench, and the induction power supply controls the working magnetic pole I and Alternating magnetic field between working poles II. The numerical control system and induction power supply are used for control, which can more accurately control the parameters of the laser beam, powder feeding time and powder feeding volume, so that the change of the alternating magnetic field can meet the needs of impurity removal and gas removal.

Preferably, the material of the magnet is silicon steel sheet, ferrite, permalloy or electrical soft iron, and the structure between the working magnetic pole I and the working magnetic pole II and the magnet is an integrated structure formed of the same material, or It is a separate structure formed by different materials. More comparative tests have shown that the above materials all have high saturation magnetization, are easy to magnetize and demagnetize, and are suitable for use under alternating magnetic fields. The integrated design or separate structural design of the magnet and the magnetic pole can meet the needs of different situations.

Preferably, the distance a between the working magnetic pole I and the working magnetic pole II ranges from 5 to 30 mm; the distance h between the bottom surface of the working magnetic pole I and the working magnetic pole II and the workpiece surface ranges from 0.5 to 15 mm. More comparative tests have shown that controlling the above distance a and h within an appropriate range can make the surface of the workpiece in the alternating magnetic field as much as possible on the premise of ensuring the smooth passage of the laser and laser cladding powder feeder nozzles , so that gas and inclusions can be discharged more easily.

Preferably, the induction coil is an enameled wire, a coil wound by a cable or a coil wound by a copper tube, and each turn of the induction coil is electrically insulated.

The present invention also provides a laser cladding method for removing pores/inclusions in the laser cladding layer, which is characterized in that it uses the laser cladding device for removing pores and inclusions in the laser cladding layer as described above, specifically comprising The following steps:

S1. Clean the prepared workpiece mechanically, and fix it on the workbench for use. At the same time, dry and dehydrate the laser cladding material at high temperature, and put it into the laser cladding powder feeder for use after cooling;

S2. Turn on the laser in the laser cladding device, focus the laser beam on the surface of the workpiece, the laser cladding powder feeder sends the laser cladding material to the laser spot on the surface of the workpiece, and turn on the induction power supply at the same time, the laser on the surface of the workpiece Apply an alternating magnetic field to the cladding material;

S3. Set the process parameters of the laser beam and the alternating magnetic field, and start the laser cladding. At the same time as the laser cladding, the laser cladding powder feeder synchronously sends the laser cladding material to the laser spot on the surface of the workpiece for supplementation. The electromagnetic force generated by the alternating magnetic field removes the pores and non-metallic inclusions in the laser cladding layer;

S4. After the laser cladding process is over, immediately turn off the laser and the induction power supply.

Further preferably, in step S1, the laser cladding material is powder material, filamentary material or flake material; its chemical composition is aluminum-based material, copper-based material, iron-based material, nickel-based material, cobalt-based material Or intermetallic compound-based materials with good electrical conductivity. According to the needs of the laser cladding materials of the above shape and composition, the appropriate laser cladding materials can be selected to meet the cladding needs of different types of workpieces.

Preferably, in step S3, when the laser cladding is carried out in the alternating magnetic field, the laser cladding material on the surface of the workpiece forms a molten pool, an induced current is generated in the molten pool, and the charged liquid metal is subjected to a vertical downward electromagnetic force due to the action of the electromagnetic field. Force F _EM or F _E ' _M ,

F _EM =J ₀ ×B ₀ , F _E ' _M =J' ₀ ×B' ₀ ,

Among them, B ₀ or B' ₀ is the magnetic induction intensity during laser cladding in an alternating magnetic field, and J ₀ or J' ₀ is the induced current in the molten pool on the surface of the workpiece.

Preferably, in step S3, during the laser cladding process, the air bubbles generated in the molten pool form pores after the laser cladding is completed, and the air bubbles and non-metallic inclusions in the molten pool generate a force opposite to the direction of the electromagnetic force in the molten pool. The rising force F _P , the maximum escape velocity V _max of bubbles or non-metallic inclusions is proportional to the diameter d _p of bubbles or non-metallic inclusions, the magnetic induction intensity B ₀ and the frequency f of the alternating magnetic field; it is proportional to the viscosity of the metal melt η is inversely proportional to, and decreases exponentially with the depth value of bubbles or non-metallic inclusions.

Specifically, the alternating magnetic field traverses the molten pool, and generates a downward electromagnetic thrust (Lorentz force) to the liquid metal in the molten pool; The difference in conductivity of the metal liquid, the bubbles and non-metallic inclusions in the molten pool have an opposite upward force F _P in the molten pool due to their low conductivity, and this upward force F _P can promote their separation from the molten pool out, thereby improving the quality of the laser cladding layer.

Preferably, in step S3, during laser cladding, the process parameters of the laser beam and the alternating magnetic field are: laser power P=300-12000W, scanning speed V=2-3500mm/s, laser spot diameter D =0.3-25mm; the strength of the alternating magnetic field B=5-650mT, the current I=3-330A, the frequency f=2-124kHz; the laser cladding is protected by inert gas. More comparative tests have shown that controlling the process parameters of the laser beam and alternating magnetic field within the above range can effectively carry out laser cladding, and at the same time have a magnetic field with sufficient strength to generate Lorentz force, so that the gas and inclusions can be discharged smoothly . The use of inert gas for atmosphere protection can prevent the cladding layer from being oxidized to produce new inclusions, thereby improving the efficiency of the device’s removal of impurities.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention has the following advantages and beneficial effects:

(1) The laser cladding device of the present invention uses a specially designed alternating magnetic field to carry out laser-induction composite cladding. By applying an alternating magnetic field, it passes through the molten pool transversely and generates downward electromagnetic force on the liquid metal in the molten pool. Thrust (Lorentz force); at the same time, using the difference in conductivity between the bubbles and non-metallic inclusions in the molten pool and the metal liquid, the bubbles and non-metallic inclusions in the molten pool have The opposite upward force F _P is generated in the middle, and this upward force F _P can promote their separation from the molten pool, thereby improving the quality of the laser cladding layer.

(2) The device of the present invention adopts a laser composite processing head with an integrated structure, which integrates electrodes, induction coils, working magnetic poles and laser light guide tubes, etc., and has a compact structure; through a specially designed magnet and two A working pole applies an alternating magnetic field to the laser cladding pool on the surface of the workpiece. The device is easy to operate and has strong practicability, and can be used for laser cladding, laser melting, laser alloying or laser rapid prototyping of metal parts, etc. aspect. The laser cladding powder feeder automatically conveys the laser cladding material to the surface of the substrate through the powder feeding nozzle, and supplements it while cladding, which can make the material cladding gradually and make it easier for gas and inclusions to be discharged from the cladding metal.

(3) The present invention selects suitable magnet materials, and controls the distance a between the working magnetic poles and the distance h between the working magnetic poles and the surface of the workpiece in a suitable range, which can ensure that the laser and the powder feeder nozzle pass through smoothly. , Make the surface of the workpiece in a sufficiently strong alternating magnetic field as much as possible, so that the gas and inclusions can be discharged more easily.

(4) The method of the present invention controls the process parameters of the laser beam and the alternating magnetic field within a certain range, so as to effectively carry out laser cladding, and at the same time generate a strong enough magnetic field and Lorentz force, so that the gas and inclusions can be discharged smoothly . The use of inert gas for atmosphere protection can prevent the cladding layer from being oxidized and produce new inclusions, thereby improving the efficiency of the device’s impurity removal; and selecting appropriate laser cladding materials according to needs can meet the welding needs of different types of workpieces; and The method can complete the cladding and impurity removal of the cladding layer by using only a few steps, the steps are simple and easy to operate, and the cost is low.

(5) The device and method of the present invention are simple and easy to obtain, can significantly reduce pores and non-metallic inclusions in the aluminum alloy laser cladding layer, significantly improve the quality of the laser cladding layer, and have important application value.

Description of drawings

Fig. 1 is the structural representation of the laser cladding device of the present invention that removes the pores and inclusions of the laser cladding layer;

Fig. 2 schematic diagram of the laser composite processing head of the laser cladding device of the present invention;

Fig. 3 is the schematic diagram of the direction of electromagnetic force in the molten pool under the forward alternating magnetic field of the present invention;

Fig. 4 is the schematic diagram of the direction of electromagnetic force in the molten pool under the reverse alternating magnetic field of the present invention;

Fig. 5 is the cross-sectional morphology of the laser cladding layer of the present embodiment 1;

Fig. 6 is the cross-sectional morphology of the laser cladding layer of the present embodiment 2;

Fig. 7 is the cross-sectional morphology of the laser cladding layer of the present embodiment 3;

Fig. 8 is the cross-sectional morphology of the laser cladding layer of the present embodiment 4;

Fig. 9 is the cross-sectional morphology of the laser cladding layer in Example 5;

Fig. 10 is a graph showing the variation curve of porosity/inclusion rate of aluminum alloy powder feeding laser cladding layer under alternating magnetic field.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Fig. 1 is a schematic structural view of a laser cladding device for removing pores and inclusions in the laser cladding layer of the present invention, as shown in the figure, it includes a workbench 9 and a laser cladding powder feeder 11 arranged in front of the workbench 9 And the laser compound processing head that is positioned at workbench 9 tops,

Wherein, the workpiece 8 is placed on the workbench 9, the laser composite processing head includes an electrode 3, an induction coil 4, a laser light guide cylinder 5, a magnet 7, a working magnetic pole I 7.1 and a working magnetic pole II 7.2, the The working magnetic pole I7.1 and the working magnetic pole II7.2 are relatively arranged at one end of the magnet 7, and there is a certain gap between them, and the laser light guide tube 5 and the workpiece 8 are respectively located at the working magnetic pole I7.1 and the working magnetic pole II7. 2, the bottom of the working magnetic pole I 7.1 and the working magnetic pole II 7.2 are separated from the surface of the workpiece 8 by a certain distance, and the beam at the other end of the magnet 7 is covered with an induction coil 4, so Both ends of the induction coil 4 protrude and connect with the electrode 3, and the magnet 7 provides an alternating magnetic field between the working magnetic pole I7.1 and the working magnetic pole II7.2 to act on the surface of the workpiece 8,

The laser cladding powder feeder 11 adds laser cladding materials to the surface of the workpiece 8, and the laser cladding device also includes a laser 1, which outputs a laser beam 6 through an optical path system and a laser light guide tube 5. The laser beam 6 passes through the gap between the working magnetic pole I 7.1 and the working magnetic pole II 7.2 and irradiates the surface of the workpiece 8 for laser cladding.

In a preferred embodiment of the present invention, the laser cladding device also includes a numerical control system 10 and an induction power supply 2 connected to the electrode 3. The numerical control system 10 controls the laser 1, the laser cladding powder feeder 11, and the induction power supply 2 and the workbench 9, the induction power supply 2 controls the alternating magnetic field between the working magnetic pole I and the working magnetic pole II.

In another preferred embodiment of the present invention, the material of the magnet 7 is silicon steel sheet, ferrite, permalloy or electrical soft iron, and the connection between the working magnetic pole I7.1 and the working magnetic pole II7.2 and the magnet 7 is The structure in between is an integrated structure formed of the same material, or a separate structure formed of different materials.

In another preferred embodiment of the present invention, the distance a between the working magnetic pole I7.1 and the working magnetic pole II7.2 ranges from 5 to 30 mm; the bottom surfaces of the working magnetic pole I7.1 and the working magnetic pole II7.2 are in contact with The distance h between the surfaces of the workpiece 8 ranges from 0.5 to 15 mm.

In another preferred embodiment of the present invention, the induction coil 4 is a coil made of enameled wire, a cable or a copper tube, and each turn of the induction coil is electrically insulated.

According to another aspect of the present invention, a laser cladding method for removing pores/inclusions in the laser cladding layer is provided, which is characterized in that it adopts the laser cladding method for removing pores and inclusions in the laser cladding layer as described above. The overlay device specifically includes the following steps:

S1. Clean the prepared workpiece mechanically, and fix it on the workbench for use. At the same time, dry and dehydrate the laser cladding material at high temperature, and put it into the laser cladding powder feeder for use after cooling;

S2. Turn on the laser in the laser cladding device, focus the laser beam on the surface of the workpiece, the laser cladding powder feeder sends the laser cladding material to the laser spot on the surface of the workpiece, and turn on the induction power supply at the same time, the laser on the surface of the workpiece Apply an alternating magnetic field to the cladding material;

S3. Adjust the process parameters of the laser beam and alternating magnetic field, and start laser cladding. At the same time as laser cladding, the laser cladding powder feeder synchronously sends the laser cladding material to the laser spot on the surface of the workpiece for supplementation. Electromagnetic force removes pores and non-metallic inclusions in the laser cladding layer;

S4. After the laser cladding process is over, immediately turn off the laser and the induction power supply.

In a preferred embodiment of the present invention, in step S1, the laser cladding material is powder material, filamentary material or flake material; its chemical composition is aluminum-based material, copper-based material, iron-based material, nickel base material, cobalt based material or intermetallic compound based material with good electrical conductivity.

In another preferred embodiment of the present invention, in step S3, the alternating magnetic field is specially set according to the manner shown in Fig. 3 and Fig. 4. When laser cladding is performed in the alternating magnetic field, the laser cladding material on the surface of the workpiece forms a molten The pool, the induced current is generated in the molten pool, and the charged metal liquid is subjected to the vertical downward electromagnetic force F _EM or F _E ' _M due to the action of the electromagnetic field,

F _EM =J ₀ ×B ₀ , F _E ' _M =J' ₀ ×B' ₀ ,

Among them, B ₀ or B' ₀ is the magnetic induction intensity during laser cladding in an alternating magnetic field, and J ₀ or J' ₀ is the induced current in the molten pool on the surface of the workpiece.

In another preferred embodiment of the present invention, in step S3, during the laser cladding process, the bubbles generated in the molten pool form pores after the laser cladding is completed, and the bubbles and non-metallic inclusions in the molten pool are formed in the molten pool The upward force F _P that is opposite to the direction of the electromagnetic force is generated in the center, the maximum escape velocity V _max of the bubble or non-metallic inclusion is related to the diameter d _p of the bubble or non-metallic inclusion, the magnetic induction intensity B ₀ and the frequency f of the alternating magnetic field It is directly proportional; it is inversely proportional to the viscosity η of the metal melt, and it decreases exponentially with the depth value of bubbles or non-metallic inclusions.

In another preferred embodiment of the present invention, in step S3, during laser cladding, the process parameters of the laser beam and the alternating magnetic field are: laser power P=300-12000W, scanning speed V=2-3500mm /s, the laser spot diameter is D=0.3-25mm; the alternating magnetic field strength B=5-650mT, the current I=3-330A, the frequency f=2-124kHz; the laser cladding is protected by inert gas.

For explaining the present invention better, give a specific embodiment below:

Example 1

Mechanically grind the surface of the 100mm×10mm×10mm aluminum alloy substrate, and clean the surface of the aluminum part with absolute ethanol, and then fix it on the workbench; heat the aluminum alloy powder with the configured components at 350°C in a vacuum furnace After 2 hours of drying and dehydration treatment, it is ready to use after cooling; after the laser beam is focused, the laser cladding process is carried out by synchronous powder feeding, and at the same time, it is protected by argon gas. A fiber laser is used, the laser power density is 1.5×10 ³ W/cm ² , the spot diameter is 5mm, the scanning speed is 1m/mIn, the distance a between the two working magnetic poles is 20mm, and the distance h between the bottom surface of the working magnetic pole and the surface of the workpiece is 3mm. Magnetic induction B = 0mT, current I = 20A, frequency f = 50kHz, and the magnetic induction in the alternating magnetic field is measured with a Teslameter.

The cross-sectional morphology of the cladding layer obtained after laser cladding is shown in Figure 5, and the porosity/inclusion ratio of the cladding layer is 7.5%.

Example 2

Except for the magnetic induction intensity B, other process parameters in Example 2 are the same as in Example 1, and the magnetic induction intensity B=11mT. The cross-sectional morphology of the cladding layer obtained after laser cladding is shown in Figure 6. The rate is 5.84%.

Example 3

Except for the magnetic induction intensity B, the other process parameters of Example 3 are the same as those of Example 1, and the magnetic induction intensity B=24mT. The cross-sectional morphology of the cladding layer obtained after laser cladding is shown in Figure 7. The rate is 4.00%.

Example 4

Except for the magnetic induction intensity B, the other process parameters of Example 4 are the same as those of Example 1, and the magnetic induction intensity B=35mT. The cross-sectional morphology of the cladding layer obtained after laser cladding is shown in Figure 8. The rate is 0.66%.

Example 5

Except for the magnetic induction intensity B, the other process parameters of Example 5 are the same as those of Example 1, and the magnetic induction intensity B=50mT. The cross-sectional morphology of the cladding layer obtained after laser cladding is shown in Figure 9. The rate is 0.33%.

Example 6

Mechanically grind the surface of the 100mm×10mm×10mm aluminum alloy substrate, and clean the surface of the aluminum part with absolute ethanol, and then fix it on the workbench; heat the aluminum alloy powder with the configured components at 350°C in a vacuum furnace After 2 hours of drying and dehydration treatment, it is ready to use after cooling; after the laser beam is focused, the laser cladding process is carried out by synchronous powder feeding, and at the same time, it is protected by argon gas. A fiber laser is used, the laser power density is 1.2×10 ⁴ W/cm ² , the spot diameter is 25mm, the scanning speed is 3500mm/s, the distance a between the two working magnetic poles is 30mm, and the distance h between the bottom surface of the working magnetic pole and the surface of the workpiece is 15mm. The magnetic induction intensity B=5mT, the current I=3A, the frequency 2kHz, the magnetic induction intensity in the alternating magnetic field is measured by a Teslameter. The porosity/inclusion rate of the cladding layer obtained after laser cladding is 6.5%.

Example 7

Mechanically grind the surface of the 100mm×10mm×10mm aluminum alloy substrate, and clean the surface of the aluminum part with absolute ethanol, and then fix it on the workbench; heat the aluminum alloy powder with the configured components at 350°C in a vacuum furnace After 2 hours of drying and dehydration treatment, it is ready to use after cooling; after the laser beam is focused, the laser cladding process is carried out by synchronous powder feeding, and at the same time, it is protected by argon gas. A fiber laser is used, the laser power density is 300W/cm ² , the spot diameter is 0.3mm, the scanning speed is 2mm/s, the distance a between the two working magnetic poles is 5mm, the distance h between the bottom surface of the working magnetic pole and the surface of the workpiece is 0.5mm, and the magnetic induction intensity B=650mT, current I=330A, frequency 124kHz, and the magnetic induction in the alternating magnetic field is measured with a Teslameter. The porosity/inclusion ratio of the cladding layer obtained after laser cladding is 0.35%.

Fig. 10 is a graph showing the change of porosity/inclusion rate of the aluminum alloy powder-feeding laser cladding layer under different magnetic induction intensities.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (9)

1. A laser cladding device for removing pores/inclusions in the laser cladding layer, characterized in that it includes a workbench (9) and a laser cladding powder feeder (11) arranged in front of the workbench (9) and a laser composite processing head located above the workbench (9), Among them, the workpiece (8) is placed on the workbench (9), and the laser composite processing head includes an electrode (3), an induction coil (4), a laser light guide tube (5), a magnet (7), and a working magnetic pole I ( 7.1) and the working magnetic pole II (7.2), the working magnetic pole I (7.1) and the working magnetic pole II (7.2) are arranged at one end of the magnet (7) opposite to each other, and there is a certain gap between them, the laser light guide tube (5) and the workpiece (8) are respectively located directly above and directly below the gap between the working magnetic pole I (7.1) and the working magnetic pole II (7.2), and the bottoms of the working magnetic pole I (7.1) and the working magnetic pole II (7.2) are in contact with The surface of the workpiece (8) is separated by a certain distance, and the beam at the other end of the magnet (7) is covered with an induction coil (4), and the two ends of the induction coil (4) protrude and connect with the electrode (3). The magnet (7) provides an alternating magnetic field between the working pole I (7.1) and the working pole II (7.2) to act on the surface of the workpiece (8), The laser cladding powder feeder (11) adds laser cladding materials to the surface of the workpiece (8), and a laser (1) is arranged in front of the electrode (3), and the laser (1) passes through the optical path system and the laser The light guide cylinder (5) outputs the laser beam (6), and the laser beam (6) passes through the gap between the working magnetic pole I (7.1) and the working magnetic pole II (7.2) and irradiates the surface of the workpiece (8) for laser cladding ; The distance a between the working magnetic pole I (7.1) and the working magnetic pole II (7.2) ranges from 5 to 30 mm; the distance between the bottom surface of the working magnetic pole I (7.1) and the working magnetic pole II (7.2) and the surface of the workpiece (8) is h The range is 0.5 ~ 15mm; When laser cladding is carried out in an alternating magnetic field, the laser cladding material on the surface of the workpiece forms a molten pool, and an induced current is generated in the molten pool, and the charged metal liquid is subjected to a vertical downward electromagnetic force due to the action of the electromagnetic field

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Generate an induced current in the molten pool on the surface of the workpiece. 2. The laser cladding device according to claim 1, characterized in that, the laser cladding device further comprises a numerical control system (10) and an induction power supply (2) connected to the electrode (3), the numerical control system (10 ) to control the laser (1), laser cladding powder feeder (11), induction power supply (2) and workbench (9), the induction power supply (2) controls the alternating magnetic field between the working magnetic pole I and the working magnetic pole II . 3. The laser cladding device according to claim 1 or 2, characterized in that the material of the magnet (7) is silicon steel sheet, ferrite, permalloy or electrical soft iron; the working magnetic pole I ( 7.1) and the structure between the working pole II (7.2) and the magnet (7) is an integrated structure formed of the same material, or a separate structure formed of different materials. 4. The laser cladding device according to claim 3, characterized in that, the induction coil (4) is an enameled wire, a coil wound by a cable or a coil wound by a copper tube, and each turn of the induction coil (4) electrical insulation between them. 5. A laser cladding method for removing pores/inclusions in the laser cladding layer, characterized in that it adopts the laser cladding method for removing pores and inclusions in the laser cladding layer as described in any one of claims 1-4. The overlay device specifically includes the following steps: S1. Clean the prepared workpiece mechanically and fix it on the workbench for use. At the same time, dry and dehydrate the laser cladding material at high temperature. After cooling, put it into the laser cladding powder feeder for use; S2. Turn on the laser in the laser cladding device, focus the laser beam on the surface of the workpiece, the laser cladding powder feeder sends the laser cladding material to the laser spot on the surface of the workpiece, and turn on the induction power supply at the same time, the laser on the surface of the workpiece Apply an alternating magnetic field to the cladding material; S3. Set the process parameters of the laser beam and the alternating magnetic field, and start the laser cladding. At the same time as the laser cladding, the laser cladding powder feeder synchronously sends the laser cladding material to the laser spot on the surface of the workpiece for supplementation. The electromagnetic force generated by the alternating magnetic field removes the pores and non-metallic inclusions in the laser cladding layer; S4. After the laser cladding process is over, immediately turn off the laser and the induction power supply. 6. The laser cladding method according to claim 5, wherein in step S1, the laser cladding material is a powder material, a filamentous material or a sheet material; its chemical composition is an aluminum-based material, a copper base materials, iron-based materials, nickel-based materials, cobalt-based materials or intermetallic compound-based materials with good electrical conductivity. 7. The laser cladding method according to claim 5 or 6, wherein in step S3, when laser cladding is carried out in an alternating magnetic field, the laser cladding material on the surface of the workpiece forms a molten pool, and in the molten pool An induced current is generated, and the charged metal liquid is subjected to a vertical downward electromagnetic force due to the action of the electromagnetic field

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,

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, in,

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is the magnetic induction intensity during laser cladding in an alternating magnetic field, />

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Generate an induced current in the molten pool on the surface of the workpiece. 8. The laser cladding method according to claim 7, wherein in step S3, during the laser cladding process, the bubbles generated in the molten pool form pores after the laser cladding is completed, and the bubbles in the molten pool and The non-metallic inclusions generate a rising force F _P opposite to the direction of the electromagnetic force in the molten pool. The maximum escape velocity V _max of the bubbles or non-metallic inclusions is related to the diameter d _p of the bubbles or inclusions, the magnetic induction intensity B ₀ and the alternating It is proportional to the frequency f of the magnetic field; it is inversely proportional to the viscosity η of the metal melt, and it decreases exponentially with the depth of the bubbles or non-metallic inclusions. 9. The laser cladding method according to claim 8, characterized in that, in step S3, during laser cladding, the process parameters of the laser beam and the alternating magnetic field are: laser power P=300-12000W, Scanning speed V=2～3500mm/s, laser spot diameter D=0.3～25mm; the alternating magnetic field strength B=5～650mT, current I=3～330A, frequency f=2～124kHz; during laser cladding Use inert gas for protection.

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