Device and method for removing air holes in metal molten pool through laser directional scanning

Abstract

The invention discloses a device and method for removing pores in a metal molten pool through laser directional scanning. The device comprises a molten drop generation device, a laser transmitter, a substrate, a motion platform and a control system. The laser head is installed on one side of the base plate, a certain angle is formed between the laser head and the molten drop generating device, and it is guaranteed that the laser irradiation position is located at the position where metal liquid is not completely solidified. According to the method, a laser transmitter is regulated and controlled by a control system, and the control system controls the laser transmitter to irradiate a part where a large number of bubbles possibly exist according to stored data, so that an unsolidified metal solution flows into broken bubble holes, and after air holes in the surface of single-layer metal are filled, the bubbles in the wall body are greatly reduced; therefore, the strength and rigidity of the wall are improved, and the purpose of eliminating bubbles in formed metal is achieved.

Description

Technical Field

[0001] The present invention discloses a device and method for removing pores by directional laser scanning of a metal molten pool, and relates to the field of additive manufacturing, in particular to the field of arc additive forming control. Background Art

[0002] Additive manufacturing is based on the principle of "discrete-accumulation". According to the shape of the part you want to manufacture, the computer pre-programs the path and deposits it layer by layer from bottom to top. Compared with traditional part manufacturing methods, additive manufacturing reduces material waste and does not require casting molds or forging and stamping, which reduces the cost of part manufacturing. When manufacturing small batches of structural parts, it greatly shortens the manufacturing cycle and improves efficiency.

[0003] Arc additive manufacturing technology is one of the additive manufacturing technologies. Arc fuse additive manufacturing technology has the advantages of low manufacturing cost, high production efficiency, high material applicability, good mechanical properties of manufactured parts, and low environmental dependence. However, the wall produced by the traditional arc additive manufacturing process has a rough macroscopic appearance and a large number of bubbles in the wall. The reason is that during the metal falling and fusion process, the air will be enclosed inside the metal, thus forming bubbles. Therefore, in order to solve the problem of bubbles in a single layer of metal in the additive manufacturing process, it is necessary to use a laser to irradiate the bubbles on the surface of the metal before the metal is completely solidified to break them, so that the unsolidified metal solution flows into the broken bubble holes. After the pores on the surface of the single layer of metal are filled, the bubbles inside the wall will be greatly reduced, thereby improving the strength and rigidity of the wall. The present invention is not only applicable to traditional arc fuse additive manufacturing technology, but also to laser-induced arc fuse additive manufacturing technology. Summary of the invention

[0004] The present invention provides a device and method for removing pores by directional laser scanning of a molten metal pool, which are used to solve the problem of internal pores after a molten metal droplet is formed during an arc additive manufacturing process.

[0005] The present invention provides a device and method for removing pores by laser directional scanning of a metal molten pool, which is used to solve the problem of internal pores after metal molten droplets are formed in an arc additive manufacturing process. The device comprises: a molten droplet generating device 1, a laser emitter 2, a substrate 3 and a three-dimensional motion platform 4. The molten droplet generating device 1, the laser emitter 2 and the three-dimensional motion platform 4 are all controlled by a control system.

[0006] The substrate 3 is located at the bottom of the support frame, the three-dimensional motion platform 4 is suspended on the support frame, and the droplet generating device 1 and the laser emitter 2 are suspended on the three-dimensional motion platform 4 in front and behind. The droplet generating device 1 is used to generate metal droplets; the laser emitter 2 located behind the droplet generating device 1 can perform laser directional scanning before the metal droplets falling on the substrate 3 are completely solidified, and the bubbles in the metal droplets are broken by laser irradiation, which can effectively eliminate metal holes and improve the performance of the finished product; the substrate 3 is a forming plate manufactured by arc additive manufacturing.

[0007] After a single layer of metal is formed, according to the statistical information of the control system located in the three-dimensional motion platform 4, a laser is used to irradiate the surface where a large number of metal bubbles may exist. The metal bubbles burst after being irradiated by the laser. Since the metal is not completely solidified at this time, the metal liquid around the metal bubbles will flow into the broken bubbles to fill the pores, thereby achieving the function of eliminating the bubbles inside the metal.

[0008] Furthermore, the droplet generating device 1 adopts the arc fuse additive technology of single-layer metal forming.

[0009] Furthermore, laser irradiation is to eliminate bubbles inside the unformed metal. The laser emitter 2 is controlled by the control system. The control system controls the laser emitter to irradiate at the location where a large number of bubbles may exist according to the stored data. After the laser beam irradiates the metal bubbles, the unformed metal bubbles are burst. The metal liquid around the metal bubbles will flow into the bubbles, fill the bubble holes, and eliminate the bubbles, thereby achieving the purpose of improving the internal quality of the additive metal.

[0010] Furthermore, a database is provided in the control system, which contains historical data of bubbles generated when metal droplets of the molten droplet generating device fall onto the substrate 3 , and the historical data is associated with the molding material, molding technology, and molding process of the molten droplet generating device 1 .

[0011] Furthermore, the laser emitter 2 works in a linear scanning and focus enlargement mode.

[0012] The present invention provides a device and method for removing pores by laser directional scanning of a molten metal pool, which is characterized in that: before a single layer of metal solidifies, a laser is used to irradiate a forming layer, and after the laser irradiates the bubbles, the bubbles will burst due to heat, and the surrounding metal liquid will flow into the pores to fill the pores, thereby eliminating the bubbles.

[0013] The present invention provides a method for removing pores from a metal molten pool by directional laser scanning, comprising the following steps:

[0014] (a) First, the metal raw material is cleaned to remove oxides and impurities on the surface, and acetone is used to remove oil stains on the substrate. The substrate is then kept clean and dry. The cleaned metal raw material is placed in a molten droplet generating device and the molten droplet generating device is heated.

[0015] (b) Turn on the gas protection device to protect the generation process of the molten droplet from being affected by the air; after setting the laser power and laser beam width of the laser emitter, the laser emitted by the laser emitter 2 has a certain preheating effect on the substrate.

[0016] (c) Control the amount of metal droplets applied by the droplet generator to match the width of the laser beam so that the laser can fully irradiate most of the bubbles. Set the temperature of the droplet generator so that after the metal is heated to the point where it can be completely melted, it will produce metal droplets and maintain a stable metal droplet transition mode.

[0017] (d) Then, the three-dimensional motion platform is turned on to drive the substrate to move. The laser emitter is controlled by the control system. The control system controls the laser emitter to irradiate the part where a large number of bubbles may exist according to the stored data, ensuring that the laser irradiation position is always within one centimeter of the metal droplet, and ensuring that the metal is not solidified during laser irradiation. The droplet generating device is turned off, the three-dimensional motion mechanism is controlled to return to the initial position, the droplet generating device is turned on, and the second additive manufacturing is performed, and so on, and finally a precisely formed wall is obtained.

[0018] (e) By changing the amount of metal droplets, the current of the droplet generator, the distance from the droplet generator to the substrate, the laser power, the laser beam width, and the laser action mode, additively manufactured walls with different shapes and qualities can be obtained.

[0019] The beneficial effect of the present invention is that it provides an additive manufacturing method for eliminating bubbles inside metal. One advantage is that it solves the problem of bubbles inside metal in arc additive manufacturing. The wall produced by the traditional arc additive manufacturing process has a rough macroscopic appearance and a large number of bubbles inside the wall. The reason is that during the metal falling process and the fusion process, the air will be sealed inside the metal, thereby forming bubbles. Therefore, in order to solve the problem of bubbles in a single layer of metal in the additive manufacturing process, it is necessary to use a laser to irradiate the bubbles on the metal surface before the metal is completely solidified to break them. The laser emitter is controlled by the control system. The control system controls the laser emitter to irradiate the parts where a large number of bubbles may exist according to the stored data, so that the unsolidified metal solution flows into the broken bubble holes. After the pores on the surface of the single layer of metal are filled, the bubbles inside the wall will be greatly reduced, thereby improving the strength and rigidity of the wall. The present invention successfully eliminates the bubbles on the surface of the unformed single layer of metal, thereby eliminating the bubbles inside the formed metal, and the forming quality is improved. The present invention solves the problem of bubbles inside the formed part in the additive manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the laser-induced metal droplet forming device of the present invention.

[0021] In the figure, 1-molten droplet generating device, 2-laser emitter, 3-substrate, 4-three-dimensional motion platform. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific implementation modes.

[0023] Method Example 1: The heating method in the droplet generating device is to heat by high-frequency heating, i.e., electromagnetic induction heating. The present invention designs a device and method for removing pores by laser directional scanning of a metal molten pool, including a droplet generating device, a laser emitter, a substrate, and a three-dimensional motion platform. The laser emitter is controlled by a control system located inside the three-dimensional motion platform. The control system controls the laser emitter to irradiate a portion where a large number of bubbles may exist according to stored data. The metal bubbles will burst with the laser irradiation, and the metal liquid around the bubbles will flow into the metal bubbles, thereby achieving the purpose of eliminating the metal bubbles.

[0024] The specific operation is that before the metal is put in, most of the oxide scale on its surface is removed by chemical method, and then the metal is put into the crucible, the electromagnetic induction heating device and the laser device are connected, the gas protection device is turned on, the protective gas is introduced, and the molten droplet generating device is heated to the preheating temperature, and then the laser pulse width, laser frequency, and laser current are adjusted. The laser power ratio is selected as 20%, the input laser power is 2000*20%=400W, the laser focal length is selected as 10mm, the laser pulse width is 2ms, the laser frequency is selected as 20Hz, and the laser current is selected as 20A. Then, the laser head is turned on, and then the air pressure of the gas protection device is adjusted to make the molten droplet generating device generate metal droplets, and then the substrate is driven to move through the three-dimensional motion platform. The laser emitter is regulated by the control system. The control system controls the laser emitter to irradiate at the position where a large number of bubbles may exist according to the stored data, so that the unsolidified metal solution flows into the broken bubble hole, and finally achieves the purpose of eliminating the bubbles inside the formed metal.

[0025] Method Example 2: The heating method of the droplet generating device is to use an arc to melt the wire to generate metal droplets. The laser controls the forming of the metal droplets generated by the induced arc. The laser emitter is regulated by the control system. The control system controls the laser emitter to irradiate the parts where a large number of bubbles may exist according to the stored data, so that the unsolidified metal solution flows into the broken bubble holes. After the pores on the surface of the single-layer metal are filled, the bubbles inside the wall will be greatly reduced, thereby improving the strength and rigidity of the wall. According to the above, the laser-induced metal droplet forming device includes a droplet generating device, a laser emitter, a three-dimensional motion platform, and a substrate. The droplet generating device is composed of a TIG welder, a gas protection device, and a wire feeding mechanism. The experimental material is 5 series aluminum alloy welding wire, and the experimental device is as follows. Figure 1As shown, a substrate is placed on a three-dimensional motion platform, and a TIG welding gun and a laser head are fixed by a fixture. During the movement of the three-dimensional platform, the laser head is always kept in front and the arc is kept in the back, so that the laser can induce the formation of the molten droplets generated by the arc in front. The laser emitter is controlled by the control system. The control system controls the laser emitter to irradiate the parts where a large number of bubbles may exist according to the stored data, so that the unsolidified metal solution flows into the broken bubble holes. After the pores on the surface of the single-layer metal are filled, the bubbles inside the wall will be greatly reduced, thereby improving the strength and rigidity of the wall. The angle between the laser head and the welding gun can be adjusted arbitrarily according to the above device. In this experiment, 45 degrees is taken. The TIG welding gun is perpendicular to the substrate platform, and the angle between the welding wire and the substrate is maintained at 20 degrees.

[0026] The specific operation is: turn on the laser transmitter, welding power supply and water cooling box, set the welding current to 100A, wire feeding speed to 200mm / min, laser pulse width to 2.5ms, welding speed to 300mm / min, and laser focal length to 10mm. Turn on the gas protection device so that the inert gas shielding welding wire is not affected by the air during the melting process, so that the metal droplet is only affected by the gas pressure during the falling process. The TIG arc melts the welding wire to produce molten metal droplets, which are solidified and formed on the substrate by the laser-induced movement of the three-dimensional motion platform. In order to ensure the forming accuracy, the welding current and wire feeding speed of TIG welding are controlled so that the amount of molten metal droplets produced by the arc matches the width of the laser heating area. The molten metal droplets are induced to solidify and form within the heating area given by the laser. The laser emitter is regulated by the control system in the three-dimensional motion platform. The control system controls the laser emitter to irradiate the parts where a large number of bubbles may exist according to the stored data, so that the unsolidified metal solution flows into the broken bubble holes. After the pores on the surface of the single-layer metal are filled, the bubbles inside the wall will be greatly reduced, thereby improving the strength and rigidity of the wall, and ultimately achieving the purpose of eliminating bubbles inside the metal.

Claims

1. A laser directional scanning metal molten pool pore removal device, characterized in that: include: A molten droplet generating device, a laser emitter, a substrate and a three-dimensional motion platform; the molten droplet generating device, the laser emitter and the three-dimensional motion platform are all controlled by a control system; The substrate is located at the bottom of the support frame, the three-dimensional motion platform is suspended on the support frame, and the molten droplet generating device and the laser emitter are suspended on the three-dimensional motion platform in front and behind; the molten droplet generating device is used to generate metal droplets; the laser emitter located behind the molten droplet generating device can perform laser directional scanning before the metal droplets falling on the substrate are completely solidified, and the bubbles in the metal droplets are broken by laser irradiation, thereby eliminating metal holes and improving the performance of the finished product; the substrate is a molding plate manufactured by electric arc additive manufacturing; After a single layer of metal is formed, a laser is used to irradiate the surface where a large number of metal bubbles may exist according to the statistical information of the control system located in the three-dimensional motion platform. The metal bubbles burst after being irradiated by the laser. Since the metal is not completely solidified at this time, the metal liquid around the metal bubbles will flow into the broken bubbles and fill the pores, thereby achieving the function of eliminating the bubbles inside the metal.

2. The laser directional scanning metal molten pool pore removal device according to claim 1 is characterized in that: The molten droplet generating device adopts the arc fuse additive technology of single-layer metal forming.

3. The device for removing pores by directional laser scanning of a molten metal pool according to claim 1, characterized in that: Laser irradiation is used to eliminate bubbles inside unformed metal. The laser emitter is regulated by the control system. The control system controls the laser emitter to irradiate the parts where a large number of bubbles may exist according to the stored data. After the laser beam irradiates the metal bubbles, the unformed metal bubbles will burst. The metal liquid around the metal bubbles will flow into the bubbles, filling the bubble holes and eliminating the bubbles, thereby achieving the purpose of improving the internal quality of the additive metal.

4. The device for removing pores by directional laser scanning of a molten metal pool according to claim 1, characterized in that: The control system is provided with a database, which contains historical data of bubbles generated when metal droplets of the molten droplet generating device fall onto the substrate. The historical data is associated with the molding material, molding technology and molding process of the molten droplet generating device.

5. The device for removing pores by directional laser scanning of a molten metal pool according to claim 1, characterized in that: The laser transmitter works in a linear scanning and focus increasing mode.

6. A method for removing pores by directional laser scanning of a molten metal pool using the device according to any one of claims 1 to 5, characterized in that: Before a single layer of metal solidifies, a laser is used to irradiate the forming layer. After the laser irradiates the bubbles, the bubbles will burst due to heat, and the surrounding metal liquid will flow into the pores to fill the pores, thereby eliminating the bubbles.

7. The method for removing pores by directional laser scanning of a molten metal pool according to claim 6, characterized in that: The following steps are involved: (a) First, the metal raw material is cleaned to remove oxides and impurities on the surface, and acetone is used to remove oil stains on the substrate. Then, the substrate is kept clean and dry, and the cleaned metal raw material is placed in a molten droplet generating device to heat the molten droplet generating device; (b) Turn on the gas protection device to protect the generation process of the molten droplet from being affected by the air; after setting the laser power and laser beam width of the laser transmitter, the laser emitted by the laser transmitter has a certain preheating effect on the substrate; (c) controlling the amount of metal droplets applied by the droplet generating device to match the width of the laser beam so that the laser can fully irradiate most of the bubbles; setting the temperature of the droplet generating device so that after the metal is heated to the point where it can be completely melted, it generates metal droplets and maintains a stable metal droplet transition mode; (d) Then, the three-dimensional motion platform is turned on to drive the substrate to move. The laser emitter is controlled by the control system. The control system controls the laser emitter to irradiate the position where a large number of bubbles may exist according to the stored data, ensuring that the laser irradiation position is always within one centimeter of the metal droplet, and ensuring that the metal is not solidified during laser irradiation; the droplet generating device is turned off, the three-dimensional motion mechanism is controlled to return to the initial position, the droplet generating device is turned on, and the second additive manufacturing is performed, and so on, and finally a precisely formed wall is obtained; (e) By changing the amount of metal droplets, the current of the droplet generator, the distance from the droplet generator to the substrate, the laser power, the laser beam width, and the laser action mode, additively manufactured walls with different shapes and qualities can be obtained.

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