CN113059193B - A device for studying the evolution process of laser selective melting melt pool - Google Patents

Abstract

The invention relates to a device for researching the evolution process of a selective laser melting pool, which comprises a first glass sheet with small holes capable of being filled with metal powder, a second glass sheet covered on the first glass sheet, a clamp for clamping the first glass sheet and the second glass sheet, and a laser system for positioning the metal powder in the small holes, wherein the small holes are formed in the joint surface of the first glass sheet and the second glass sheet. The device can realize the capture of a single molten pool in the SLM process, has simple operation, less required time, repeated operation and long service life, and the glass sheet with the small holes can be filled with various different metal materials, which means that the device can be used for researching a plurality of material systems; the quartz glass is adopted, the laser selection is not influenced, the laser wavelength selectivity is strong, and continuous laser and pulse laser can be adopted to research the interaction characteristics of the laser with different characteristics and the metal powder.

Description

A device for studying the evolution process of laser selective melting melt pool

technical field

The invention relates to the technical field of metal additive manufacturing, in particular to a device for studying the evolution process of laser selective melting molten pools.

Background technique

Selective Laser Melting (SLM) technology is an additive manufacturing method that uses continuous laser or pulsed laser as a heat source to selectively melt metal powder according to the CAD three-dimensional model, and superimposes it layer by layer to realize the molding of solid parts. This technology has the advantages of a wide range of forming materials, excellent mechanical properties of formed parts, high density, high precision of forming parts, and the ability to form parts with complex geometry. It has been widely used in aerospace, automotive, military and other fields.

Since the advent of the laser, the research on the interaction between the laser and the continuum has been greatly developed. For example, in the field of laser processing, there are a large number of related literature and monographs on the interaction between the laser and the bulk metal material. The characteristic of laser selective melting is that the laser irradiates the metal powder and melts it to form a molten pool. The size of the metal powder is equivalent to the laser spot. For the laser, the metal powder is a discrete medium. The interaction between laser light and discrete media differs significantly from that of continuous media. For example, there are pores in the metal powder during the accumulation and laying process, and the laser will reflect multiple times between the powders, which means that the mechanism of laser input into powder metal materials is fundamentally different from that of bulk metal materials.

In the laser selective melting process, common defects include spheroidization, pores, cracks, splashes, etc., and the formed part structure is also prone to uneven distribution of elements and structures from nm to μm scale. To analyze and solve these problems, it is necessary to study the interaction mechanism between powder metal materials and laser. Specifically, in the SLM forming process, it is necessary to study the formation and solidification process of its smallest structural unit, that is, the molten pool.

Limited by the technical characteristics of fast heating and fast cooling of SLM, the current mainstream methods of studying molten pools are numerical simulation and microstructure characterization. The former lacks data on the formation process of a single molten pool in situ, and the latter cannot know the formation process of a single molten pool. Because of the remelting of the molten pool in SLM and the resulting changes in structure and composition, it means that the structure and composition of the molten pool cannot be obtained when the molten pool is just formed.

Studying the interaction characteristics of laser and powder metal can understand how laser energy is input into powder metal and the specific process of molten pool formation, and then understand the structure formation process in SLM and the mechanism of various defects from the source, which is of great significance to the development of SLM technology. Crucial role. However, there is currently a lack of effective research methods for the formation process of a single molten pool.

Contents of the invention

The purpose of the present invention is to provide a device for studying the evolution process of the laser selective melting pool, which can be used to study aspects such as splashing, cracks and corrosion in the current technology, and has strong operability for optimizing process parameters and improving product quality .

In order to achieve the above object, the embodiment of the present invention provides the following technical solution: a device for studying the evolution process of laser selective melting molten pool, comprising a first glass sheet with a small hole that can be filled with metal powder, covering the A second glass sheet on a first glass sheet, a clamp for holding said first glass sheet and said second glass sheet, and a laser system for positioning a metal powder that can melt in said small hole, said small Holes are opened on the surface where the first glass sheet and the second glass sheet are bonded.

Further, the clamp includes a slot, and the slot has a groove for the first glass sheet and the second glass sheet that are bonded together to be snapped in as a whole, and the groove has the first glass sheet The glass sheet and the pressing surface on which the second glass sheet is pressed.

Further, a stepping motor for driving the clamp to move is also included.

Further, the clamp includes a connecting rod connectable to the driving end of the stepping motor, and an end of the connecting rod far away from the stepping motor is connected to the clamp.

Further, the laser system includes a laser and a scanning galvanometer for controlling the movement path of the laser.

Further, a horizontal working platform for positioning is also included, and the clamp is suspended above the horizontal working platform and parallel to the horizontal working platform.

Further, positioning marks are provided on the horizontal working platform.

Further, there are multiple small holes, and the multiple small holes are arranged in a matrix.

Further, the small hole is a hemispherical small hole.

Further, both the first glass sheet and the second glass sheet are quartz glass sheets.

Compared with the prior art, the beneficial effect of the present invention is that the "capture" of a single molten pool in the SLM process can be realized through the device, the operation is simple, the time required is less, the operation can be repeated many times, the device has a long service life, and the The glass sheet with small holes can be filled with various metal materials, which means that this device can be used to study multiple material systems; the use of quartz glass has no effect on laser selection, and the laser wavelength is highly selective, and continuous laser and pulse can be used Laser, to study the interaction characteristics of lasers with different characteristics and metal powders; in addition, by adjusting laser parameters and changing laser characteristics to act on metal powders, the process of melting pools from scratch can be observed, which is useful for studying how to control laser energy input in SLM, Therefore, it is of great significance to control the evolution law of molten pool and regulate the formation of tissue.

Description of drawings

Fig. 1 is a schematic diagram of a device for studying the evolution process of laser selective melting molten pool provided by an embodiment of the present invention;

Fig. 2 is a schematic diagram of the first glass sheet of a device for studying the evolution process of laser selective melting molten pool provided by the embodiment of the present invention (in the case of a single small hole);

Fig. 3 is a schematic diagram of the first glass sheet of a device for studying the evolution process of laser selective melting molten pool provided by an embodiment of the present invention (when there are multiple small holes);

Fig. 4 is a schematic diagram of a fixture of a device for studying the evolution process of laser selective melting molten pool provided by an embodiment of the present invention;

Fig. 5 is a schematic diagram of the cooperation of the fixture, the first glass sheet and the second glass sheet of a device for studying the evolution process of the laser selective melting molten pool provided by the embodiment of the present invention;

Fig. 6 is an actual effect diagram of a device for studying the evolution process of laser selective melting molten pool provided by the embodiment of the present invention;

Among the reference signs: 1-stepping motor; 2-connecting rod; 3-card slot; 40-first glass sheet; 41-second glass sheet; 5-horizontal working platform; 6-scanning vibrating mirror; 7-optical path System; 8-laser; 9-computer control system.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Please refer to Fig. 1 to Fig. 5, the embodiment of the present invention provides a kind of device for studying the evolution process of laser selective melting melt pool, comprising the first glass plate 40 with the small hole that can be filled with metal powder, covering the A second glass sheet 41 on a first glass sheet 40, a clamp for holding said first glass sheet 40 and said second glass sheet 41, and a laser for positioning a metal powder that can melt in said small hole system, the small hole is opened on the surface where the first glass sheet 40 and the second glass sheet 41 are bonded. As shown in Figure 6, in this embodiment, the size of the small hole is 500 microns, which is equivalent to the size of the molten pool, and the filling of metal powder can be completed through this device, as shown in Figure 6 . The laser spot used in this example is 10 microns, and its heat-affected zone is shown in the white frame. The metal powder has been sintered into black by laser, which is significantly different from the metallic luster of the adjacent parts. The sintered neck of the metal powder in the white frame is clear visible. Therefore, by adjusting parameters such as laser power and small hole size, this device can realize the "capture" of a single molten pool in the SLM process. The operation is simple, the time required is small, and the operation can be repeated many times. The glass slides can be filled with a variety of different metallic materials, meaning the device can be used to study multiple material systems. In addition, by adjusting the laser parameters and changing the laser characteristics to act on the metal powder, the process of the molten pool from scratch can be observed, which is of great significance for studying how to control the laser energy input in the SLM, thereby controlling the evolution of the molten pool and regulating the formation of the tissue. Specifically, the metal powder is placed between two layers of glass sheets, and the laser emitted by the laser system can melt the metal powder, and then turn the small hole into a molten pool, and then through external factors such as replacing the metal powder and emitting laser light, the process can be carried out. Research. However, before melting, clamping the first glass piece 40 and the second glass piece 41 by the clamp can ensure that the first glass piece 40 and the second glass piece 41 are closely attached, and can also ensure that the positions of the two remain unchanged. Preferably, the small holes are hemispherical small holes.

As an optimization scheme of the embodiment of the present invention, please refer to Fig. 1 to Fig. 5, the clamp includes a card slot 3, and the card slot 3 has the first glass sheet 40 and the second glass sheet for bonding together The groove that the piece 41 is integrally snapped into, the groove has a pressing surface that presses the first glass piece 40 and the second glass piece 41 tightly. In this embodiment, the above-mentioned clamp is refined, the clamp includes a slot 3, and the slot 3 has a groove for sliding in the first glass piece 40 and the second glass piece 41, and the pressing surface can ensure that the first glass piece 40 and the second glass piece 41 A glass sheet 40 and a second glass sheet 41 are compressed. Two parallel grooves can be set in the draw-in groove 3 to slide in the two glass sheets respectively. The distance between the two grooves and the size of each groove can be set to ensure that the two glass sheets Slip in to fit snugly against each other.

As an optimized solution of the embodiment of the present invention, please refer to FIG. 1 to FIG. 5 , the device further includes a stepping motor 1 for driving the clamp to move. In this embodiment, before the melting operation is performed, the position of the fixture is adjusted by the stepping motor 1 to facilitate laser shooting. Specifically, the rotational power of the stepping motor 1 can be converted into linear power through gears, racks and the like.

To further optimize the above solution, please refer to FIGS. 1 to 5, the clamp includes a connecting rod 2 that can be connected to the driving end of the stepping motor 1, and the end of the connecting rod 2 away from the stepping motor 1 is connected to on the fixture. In this embodiment, the drive of the stepper motor 1 can transmit power through the connecting rod 2 .

As an optimized solution of the embodiment of the present invention, please refer to FIG. 1 , the laser system includes a laser 8 and a scanning galvanometer 6 for controlling the movement path of the laser. In this embodiment, the laser moves to the small hole under the action of the scanning galvanometer 6 and melts the metal powder. The direction and moving speed of the laser can be controlled by controlling the moving direction and speed of the scanning galvanometer 6 . Preferably, the laser system is a conventional technical means in the field, and it may also include an optical system 7, a computer control system 9, and the like.

As an optimized solution of the embodiment of the present invention, please refer to Fig. 1 to Fig. 5, the device also includes a horizontal working platform 5 for positioning, and the clamp is suspended above the horizontal working platform 5 and is connected with the horizontal working platform. Platform 5 is parallel. Preferably, positioning marks are provided on the horizontal working platform 5 . In this embodiment, the clamp is not in contact with the horizontal working platform 5 to prevent shaking due to friction during the movement of the clamp.

As an optimization scheme of the embodiment of the present invention, please refer to FIG. 1 to FIG. 5 , there are multiple small holes, and the multiple small holes are arranged in a matrix. In this embodiment, a plurality of small holes can be set, metal powder can be put in at the same time, and then the path of the laser beam can be set through the above-mentioned scanning galvanometer 6 to perform coherent evolution.

As an optimized solution of the embodiment of the present invention, please refer to FIG. 1 to FIG. 5 , the first glass piece 40 and the second glass piece 41 are both quartz glass pieces. In this embodiment, the use of quartz glass has no effect on laser selection, and the laser wavelength is highly selective. Continuous lasers and pulsed lasers can be used to study the interaction characteristics of lasers with different characteristics and metal powders.

Next, the specific operation steps are described in detail:

When there is a small hole:

Step 1: As shown in Figure 1, determine an initial laser point O ₁ on the computer, and O ₁ point is the point where the laser starts to move, so that the position of this point corresponds to the midpoint on the right side of the horizontal processing platform, and the horizontal The size of the workbench is 20cm*20cm, the apex of the lower left corner of the platform is the origin O, the horizontal direction to the right is the X direction, and the vertical upward direction is the Y direction. The moving direction of the laser is set to -X, and there is no Y-axis velocity component.

The laser used is a continuous laser with a laser spot radius of 50 μm, a moving speed of 10 mm/s, a power of 150 W, and a power density of 1.9*10 ⁶ W/cm ² .

Step 2: Evenly spread the metal nickel-based superalloy powder on the quartz glass with a small hole, the size of which is 10mm*10mm*2mm, so that the hemispherical small hole with a radius of 50um is filled with metal powder, and use a scraper Remove all the powder on the glass sheet except the small holes, and then place another piece of quartz glass of the same specification without small holes on the quartz glass sheet filled with powder, and keep the two completely overlapped.

Place the two quartz glass sheets that keep overlapping in the inner cavity of the slot 3, as shown in FIG. 4 . The size of the outer cavity of card slot 3 is 14mm*14mm*6mm. Connecting rod 2 long 15cm, wide 6mm.

Step 3: Connect the connecting rod 2 assembled with the quartz glass sheet to the origin of the stepping motor 1, keep the slot 3 parallel to the horizontal processing platform, and keep a distance of 5cm from the platform. Set the feed value of the motor to 10cm, move the fixture to the corresponding position, and ensure that the path of the light spot coincides with the small hole of the hemisphere.

Step 4: Operate the computer to control the laser to move along the planned path, adjust the power of the laser and the radius of the spot until the metal powder is melted to form a molten pool.

Using the above steps, the molten metal powder can be observed in the quartz glass hole, and the specific value of the molten pool size is related to the set laser power, scanning speed and other parameters.

When there are multiple small holes:

Step 1: Determine an origin O ₂ on the computer. The O ₂ point is the point where the laser starts to move, so that the position of this point corresponds to the midpoint on the right side of the horizontal processing platform. The size of the horizontal working table is 20cm*20cm. Set the moving direction of the laser to -x, without the y-axis velocity component.

The laser used is a pulsed laser with a pulse width of 400ns, a peak power of 55W, a repetition rate of 20kHz, a spot radius of 50um, and a moving speed of 10mm/s. The energy density is calculated to be 0.11J/cm ² .

Step 2: Evenly spread the metal nickel-based superalloy powder on the quartz glass with a plurality of small holes, the distance between the two small holes is 3mm, and the size specification is 20mm*20mm*2mm. Make the hemispherical hole with a radius of 50um filled with metal powder, use a scraper to remove all the powder on the glass sheet except the small hole, and then make the other sheet the same. Specifications Quartz glass without pinholes is placed on a quartz glass sheet filled with powder, and the two keep completely coincident. Place the two quartz glass sheets that keep overlapping in the inner cavity of the slot 3 . The size of the outer cavity of the card slot 3 in the fixture device is 24mm*24mm*6mm. Connecting rod 2 long 15cm, wide 6mm.

Step 3: Connect the connecting rod 2 assembled with the quartz glass sheet to the origin of the stepping motor 1, keep the slot 3 parallel to the horizontal processing platform, and keep a distance of 5cm from the platform. Set the feed value of the motor to 10cm to move the fixture to the corresponding position to ensure that the path of the light spot passes through the small hole in the center.

Step 4: Operate the computer to control the laser to move along the planned path, adjust the power of the laser and the radius of the spot until the metal powder is melted to form a molten pool. Further, by re-planning the laser path through the distance between the small holes, the metal powder in multiple small holes can be melted to form multiple separate molten pools.

Using the above steps, multiple independent molten pools can be obtained, and different laser parameters can be used for the formation of each molten pool, which greatly improves the efficiency and application space of this device for studying the interaction characteristics of laser and powder.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. A device for studying the evolution process of laser selective melting molten pool, characterized in that: comprising a first glass sheet with a small hole that can be filled with metal powder, a second glass covered on the first glass sheet sheet, clamps for holding the first glass sheet and the second glass sheet, and a laser system for positioning the metal powder that can melt in the small hole opened in the first glass On the surface where the sheet is attached to the second glass sheet, adjust the laser parameters and change the laser characteristics to act on the metal powder to observe the evolution process of the molten pool. 2. A device for studying the evolution process of laser selective melting molten pool as claimed in claim 1, characterized in that: the fixture includes a draw-in slot, and the draw-in slot has the first joint for bonding together. A groove into which the glass sheet and the second glass sheet are integrally engaged, and the groove has a pressing surface for pressing the first glass sheet and the second glass sheet. 3 . The device for studying the evolution process of laser selective melting melt pool according to claim 1 , further comprising a stepping motor for driving the clamp to move. 4 . 4. A device for studying the evolution process of laser selective melting molten pool as claimed in claim 3, characterized in that: the fixture includes a connecting rod that can be connected with the driving end of the stepping motor, and the connecting rod The end of the rod away from the stepping motor is connected to the clamp. 5. A device for studying the evolution process of laser selective melting melt pool according to claim 1, characterized in that: said laser system includes a laser and a scanning galvanometer for controlling the moving path of the laser. 6. A device for studying the evolution process of laser selective melting molten pool as claimed in claim 1, characterized in that: it also includes a horizontal working platform for positioning, and the clamp is suspended on the horizontal working platform. above and parallel to the horizontal working platform. 7. A device for studying the evolution process of laser selective melting pool as claimed in claim 6, characterized in that: said horizontal working platform is provided with positioning marks. 8. A device for studying the evolution process of laser selective melting molten pool according to claim 1, characterized in that: there are multiple small holes, and the multiple small holes are arranged in a matrix. 9. A device for studying the evolution process of laser selective melting molten pool according to claim 1, characterized in that: the small hole is a hemispherical small hole. 10. The device for studying the evolution process of laser selective melting pool as claimed in claim 1, characterized in that: the first glass piece and the second glass piece are both quartz glass pieces.

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