CN114406456A - Protection method for actively regulating and controlling laser welding small hole and molten pool based on blade-shaped airflow - Google Patents

Abstract

The invention relates to a protection method for actively regulating and controlling a laser welding small hole and a molten pool based on blade-shaped airflow, which is characterized by comprising the following steps of: the protective airflow with the shape of a knife edge splits steam flow sprayed at high speed in the small hole and acts on the deep melting small hole opening to inhibit the plume to obstruct the light beam transmission and protect the molten pool; simultaneously, a raised liquid column in a molten pool is pressed, and splashing and humping are inhibited; the protective airflow can expand the orifice, which is beneficial to the escape of vapor in the orifice and reduces the porosity in the welding seam. The thickness of the protective airflow of the blade shape is between 0.1mm and 3mm, the blade length (the length vertical to the axial direction of the airflow) is between 1mm and 20mm, and the flow speed is between 1m/s and 300 m/s; the included angle between the axial direction of the blade-shaped protective airflow and the axial direction of the light beam is between 1 and 90 degrees. The projection width of the blade-shaped protective airflow on the plate surface is equal to the thickness of the airflow, and the included angle between the projection and the welding direction is 0^°～180^°. The invention canObtaining larger penetration and better weld surface forming quality, and obviously reducing the porosity in the weld.

Description

A protection method based on “knife-shaped” airflow to actively control small holes and molten pools in laser welding

technical field

The invention relates to a protection method for actively regulating laser welding small holes and molten pools based on "blade-shaped" airflow, and belongs to a method for actively regulating laser deep penetration welding small holes and molten pools by utilizing a special form of protective airflow.

Background technique

During the laser welding process, the laser welding mode is divided into deep penetration welding and thermal conduction welding according to the sudden change in the absorption rate of the material to the laser. Among them, deep penetration welding is widely studied and applied due to its good welding quality. In laser deep penetration welding, the laser beam is irradiated on the front wall of the small hole to generate laser-induced high temperature and high pressure vapor. The spray of the steam is applied to the back wall of the small hole, which will cause huge fluctuations in the molten pool of the back wall, which will affect the formation of the weld. At the same time, some large particles on the back wall will be blown out of the small hole to form splash defects or humps, and these vapors will Blow some air into the molten metal of the rear wall to form the pores. These three defects are the most typical defects encountered in the field of laser welding at present, and the root cause is the laser-induced vapor emitted along the normal direction of the surface of the front wall of the small hole. Effective control of this gas will help to improve these defects. defect.

Weld pools and small holes are a phenomenon that will inevitably appear in the process of laser deep penetration welding of metal materials due to the influence of thermal and mechanical effects. Metal vapor and particles are ejected from the small holes under the action of recoil pressure, which will seriously affect the stability of laser welding due to blocking the propagation of the laser beam, thereby affecting the shape and cooling forming of the molten pool and small holes, which will eventually seriously affect the welding. Seam forming quality. With the help of external force, the plume, the molten pool and the small hole can be effectively controlled to reduce welding defects and improve the welding quality. What form and how much force is used has become a difficult point and key point for us to study.

The method of the invention is based on the "knife-shaped" protective airflow to split the high-speed erupted steam flow (plume) in the small hole and act on the small orifice of deep melting, and has the advantages of suppressing the high-speed eruption plume in the hole, obstructing the beam transmission and disturbing the protection of the molten pool. effect; at the same time suppress the raised liquid column in the molten pool, suppress the formation of spatter and hump. First of all, the "blade-shaped" protective airflow splits the plume erupted in the small hole to act on the molten pool, reducing the plume and the particles in the plume from entering the laser beam, thus reducing the negative impact of the plume on the welding process and improving the melting point. The protective effect of the pool. Secondly, the "knife-shaped" protective airflow acting on the surface of the molten pool acts on the molten pool (the edge of the small orifice), and has the effect of suppressing the protrusions of the molten pool to form splashes or humps, thus suppressing the formation of splashes and humps. Third, the "knife-shaped" protective airflow acts on the small orifice, which will increase the diameter of the small orifice, so it is easier for the steam in the hole to escape, and the effect of reducing the porosity in the weld is achieved.

SUMMARY OF THE INVENTION

The object of the present invention is to use a kind of protection method based on "blade shape" protective airflow to actively regulate and control laser welding pinholes and molten pools, which is applicable to the field of metal material processing and relates to fields such as laser welding, laser arc hybrid welding, arc welding and the like. The "knife-shaped" protective airflow splits the high-speed erupted steam (feather) in the small hole and acts on the small deep-melting orifice, which has the effect of suppressing the high-speed eruption plume in the hole, obstructing the beam transmission and disturbing the protection of the molten pool; at the same time suppressing The raised liquid column in the molten pool inhibits the formation of spatter and hump; in addition, the protective airflow can expand the diameter of the small orifice, which is conducive to the escape of steam in the hole and reduces the porosity in the weld. By changing the flow rate or size of the blade-shaped airflow, the negative effects of plume steam can be effectively suppressed and the molten pool can be better protected, and at the same time, the effect of suppressing hump, spatter and pores in the weld can be achieved.

The "blade-shaped" airflow can be generated by the high-speed airflow passing through a very narrow slit. The width is 3-7mm, the thickness is extremely thin, only 0.01-0.05mm, and the stiffness is high. The "blade" ejected from the slit "Shape" air flow is blown out within 20mm, and its thickness is basically unchanged.

The protection method based on the "knife-shaped" airflow to actively control the laser welding holes and molten pools is characterized in that: the thickness of the "knife-shaped" protective airflow is between 0.1mm and 3mm, and the blade length (perpendicular to the airflow) The length of the axial direction) is between 1 mm and 20 mm, and the flow velocity is between 1 m/s and 300 m/s; the angle between the axial direction of the “blade-shaped” protective airflow and the beam axis is between 1° and 90°. . The projected width of the "knife-shaped" shielding airflow on the welding plate is equal to the thickness of the airflow, and the included angle between the projection and the welding direction is 0 ^° to 180 ^° .

The protection method based on the "knife-edge"-shaped airflow to actively control the laser welding holes and molten pools, the protection principle is: a special nozzle generates a special-shaped protective gas flow, and this protective gas flow is ejected from the knife-edge nozzle. , interact with the ejected metal vapor, blow off the plume to the maximum extent, and achieve the purpose of protecting the molten pool and small holes.

The protection method based on the active regulation and control of laser welding small holes and molten pools based on "blade"-shaped airflow is characterized in that: the protection gas can be argon, helium, nitrogen and other gases or a mixed gas composed of the above-mentioned gases .

The following provides a protective device for actively regulating the laser welding holes and molten pools, but it is by no means limited to the following devices, as long as the high-speed airflow can pass through a very narrow slit to generate a "blade-shaped" airflow.

The protection device is a double-layer protection nozzle composed of an outer tube and an inner tube; the outer tube of the double-layer protection nozzle is connected to an inert gas to protect the laser welding molten pool, and the inner tube generates a "blade-shaped" protective airflow and acts on the small orifice;

Including: nozzle, nozzle head cover (2), nozzle barrel inner core (3), nozzle barrel outer cover (4), nozzle tail part (5); wherein, the nozzle tail part (5) is installed on the nozzle barrel inner core (3) Install the nozzle barrel outer (4) on the nozzle barrel inner core (3), then install the nozzle head (1) on the front end of the nozzle barrel inner core (3), and then put the nozzle barrel outer jacket (4) on the nozzle (1) on; clamp the entire nozzle system with a clamp and place it above the surface of the welding material, and the gas drawn from the two protective gas cylinders flows into the nozzle barrel casing (4) and the nozzle tail part (5) through the transfer pipe, respectively. The former It is the outer nozzle of the double-layer protection nozzle, which is the inner nozzle of the double-layer protection nozzle;

The port section of the nozzle is a rectangle, the length of the rectangle is between 2mm and 7mm, and the width is between 0.01mm and 1mm.

2. For the device used, the size of the nozzle slit is 5mm in length and 0.02mm in width.

3. For the device used, the inner diameter of the outer tube of the double-layer nozzle is between 5mm and 50mm; the air jet direction of the double-layer protection nozzle is consistent with or opposite to the welding direction; the angle between the axial direction of the double-layer protection nozzle and the laser beam is set at Between 5° and 85°; the height of the protection device from the surface of the welded sheet is between 0.5mm and 5mm.

4. a kind of protection device for actively regulating laser welding aperture and molten pool according to claim 3, it is characterized in that: outer tube diameter is 20mm; the included angle between nozzle axis and laser beam is 45°, and the nozzle head bottom is 1mm away from the plate .

5. The device used is that the nozzle structure is machined on a solid cylinder. First, a concentric circular table is hollowed out. Starting from the left side, the radius of the section of the hollowed-out circular table gradually becomes smaller, and when it reaches the predetermined radius, it starts to hollow out a The cylinder with a smaller area; the purpose of the circular hollowed-out shape is a truncated cone, one is to accelerate the flow of air, and the other is to match the shape of the front port of the nozzle core in the figure below to make it fixed. The radius of the hollowed-out cylinder is the same as the figure below. The size of the front air outlet of the inner core of the nozzle is the same; then the hollowed out cylinder is hollowed out in the shape of a cuboid, and the size is described below to generate a blade-shaped airflow; The cuboid is the slit, where h is the width of the slit, which can be set to 0.01mm-1mm, L is the length of the slit, which can be set to 2-7mm, and g is the depth of the slit, which can be set to 2-3mm. A kind of slit, which outputs a knife-edge airflow.

6. The device used, the nozzle head cover is composed of a hollowed cylinder and a hollowed round table, and its installation position is screwed on the outer tube of the nozzle. effect.

7. The device used, the inner core structure of the nozzle is composed of a hollow cylinder, a convex part and a front end part of the inner core; the convex part plays a fixed role in the combination process of the inner tube and the outer tube to ensure the inner tube sleeve. After entering the outer tube, it is in a fixed position; the bulge part has an outlet channel to ensure the passage of the outer layer of air; the front end of the bulge starts, and the diameter gradually becomes smaller, and the bulge front end is connected to the nozzle, which is used to input air flow to the nozzle.

8. In the device used, a boss is set on the outer casing of the nozzle barrel, and the boss is provided with a hole thread, which is connected to the gas nozzle valve for inputting protective gas.

9. For the device used, the tail part of the nozzle is located at the end of the entire nozzle structure, connecting the inner pipe and the protective gas cylinder for supplying gas to the inner pipe.

Compared with the prior art, the present invention has the following beneficial effects: by changing the flow rate or size of the blade-shaped airflow, the negative effect of plume steam can be effectively suppressed, the molten pool can be better protected, and at the same time, the hump, splash and weld can be suppressed. The effect of mesoporosity. It can effectively protect the molten pool and small holes, and can also protect the weld and beautify the weld. It is used in the field of automobile processing, aerospace manufacturing, ship manufacturing, etc., as well as the protection of molten pools and small holes in the fields of laser welding, laser arc hybrid welding, and arc welding.

Description of drawings

Figure 1 is a schematic diagram of a nozzle;

Figure 2 is a schematic diagram of the nozzle head cover;

Figure 3 is a schematic diagram of the inner core of the nozzle;

Figure 4a is a schematic diagram of a nozzle jacket;

Fig. 4b is a half-section schematic diagram of the outer casing of the nozzle cartridge;

Figure 5 is a schematic diagram of the tail part of the nozzle;

6 is a schematic diagram of the overall structure of the nozzle;

Figures 7 and 8 are the actual observation results;

Fig. 9 is the air flow pattern produced by the nozzle observed using the schlieren;

FIG. 10 is a schematic diagram of the welding process.

Figure 11 Schematic diagram of shielding gas flow during welding

Figure 12. Top view of the schematic diagram of airflow action

Figure 13. The results of the longitudinal section of the knife-edge airflow

Figure 14. Results of adding circular airflow longitudinal section

Figure 15. Surface forming of blade-type airflow weld

Figure 16. Surface forming of circular air flow weld

Figure 17. The cross-sectional results of the bladed airflow

Figure 18. Results of adding circular airflow cross-section

Figure 19 shows the inner core of the nozzle;

Figure 20 shows a part of the inner core of the nozzle.

Detailed ways

The results of the protection of the molten pool and the small holes during the laser welding process obtained in this example.

In Figure 11: 1. Laser beam, 2. Feather light, 3. Small hole, 4. Molten pool, 5. Plate, 6. "Blade-shaped" shielding gas flow.

Figure 11 is a schematic diagram of the protection of the molten pool and the weld seam by the knife-edge airflow generated by the knife-edge nozzle during the laser welding process. When the laser beam is irradiated on the welded plate, the plate absorbs the laser energy and heats up sharply. When it reaches the boiling point, it rapidly vaporizes to form a hot plume of vapor. The molten metal sinks down under the pressure of the recoil, forming small holes. During this process, welding defects such as spatter, humps and blowholes are produced. Suppressing or purposefully improving the fluctuation amplitude and characteristics of the molten pool will greatly improve the welding quality and the aesthetics of the weld. Based on this theoretical basis, we have researched and invented such a protective gas form, which is specially used to actively control the molten pool and small holes.

In this example, the welding plate is low carbon steel, the laser used in the experiment is a YLS-6000 fiber laser with a wavelength of 1.07 microns, and the protective gas is argon. The welding process parameters are: laser power 2kW, shielding gas flow rate 3L/min, welding speed 2m/min, defocus amount 0mm, focal length 300mm, high-speed camera shooting frame number of 10000 frames/second. The welding direction is the same as the air jet direction, and the axial direction of the "knife-shaped" air flow forms an included angle of 45° with the laser beam. After the experiment, the samples were cut, ground, polished, etc. It can be seen from the figure that the number of pores in the longitudinal section of the weld with “knife-shaped” airflow is significantly less than that without airflow, the weld penetration is significantly narrower and deeper, and the weld formation has also been greatly improved. It can be seen that the "blade-shaped" protective airflow has a significant control effect on the molten pool and small holes, greatly inhibits the generation of spatter, hump and pores, and improves the weld penetration and weld surface forming quality.

As shown in Figure 1-10, it is mainly the structure of each part of the protection device. The protection device is composed of the above five parts, and is divided into two layers: the inner layer and the inner layer. The airflow in the inner layer flows through the nozzle to generate a blade-shaped airflow. The outer space is between the inner core and the outer casing. The overall structure is shown in Figure 7.

The following laser welding experiments are designed for effect comparison: use fiber laser to scan and weld low carbon steel sheets, set the laser power to 6kw, the welding speed to 2m/min, the defocus amount to 0, and place the nozzle at a distance of 1 from the surface of the welding material. -2mm position, the included angle with the laser beam is 45°, the blowing direction is opposite to the welding direction, and the shielding gas is connected to argon. After welding, the samples were cut longitudinally and transversely to observe porosity, surface formation and penetration.

The beneficial effect of the present invention is that, using the device to carry out experiments, the "blade-shaped" airflow with different stiffness and different airflow velocity can be freely realized, and then the molten pool and the small hole are actively regulated to achieve the purpose of forming a good weld.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, All should be included within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

As shown in Figure 1, it is a three-dimensional three-dimensional representation of the nozzle, which is the core component of the device of the present invention, and is used to generate a "blade-shaped" airflow, and the blade-shaped airflow is actually a bundle of airflow with extremely high stiffness.

The nozzle structure is machined on a solid cylinder. First, a concentric cone is hollowed out. As shown in the figure above, starting from the left side, the radius of the section of the hollow cone gradually becomes smaller, and an area is hollowed out after reaching the predetermined radius. smaller cylinders. The purpose of the circular hollowed-out shape as a truncated cone is to accelerate the flow of air, and secondly, to match the shape of the front port of the nozzle inner core in the figure below to make it fixed. The vent size is the same. The hollowed-out cylinder is then hollowed out in the shape of a cuboid, sized as described below, to create a knife-edge airflow. The generation mechanism is that the input airflow passes through a cuboid (slit) with a very small width, as marked in the figure above: where h is the width of the slit, which can be set to 0.01mm-1mm, and L is the length of the slit, which can be set to 2mm-7mm , g is the depth of the slit, which can be set to 2-3mm. The output airflow passes through this slit, and an ideal "blade type" airflow can be output.

The three-dimensional view of the nozzle head cover is shown in Figure 2. It consists of a hollowed-out cylinder and a hollowed-out circular platform. The shape of the hollowed-out structure is shown in Figure 2. The left and right sides are columns, and the middle is the connecting area. The cylinder is made smaller to speed up the flow of air. Its installation position is screwed on the outer tube of the nozzle, and its function is to flow out the outer air flow in a circular state to assist in protecting the molten pool.

The inner core structure of the nozzle is shown in Fig. 3a and b, which consists of a hollow cylinder and a convex part and a front end part of the inner core. The total length is 16cm, the diameter of the outer tube of the cylindrical part is 6mm, and the diameter of the inner tube is 4mm. The structure of the raised part is shown in the figure above. On the solid body formed by sandwiching a cylinder between two circular truncated cones, a longitudinal cut is made to form the shape of the cross section as shown in Figure 3.b. The protruding part has two functions, one is to fix the inner tube and the outer tube in the process of combining, to ensure that the inner tube is in a fixed position after being sleeved into the outer tube; Starting from the front of the bulge, the diameter gradually becomes smaller, the gradient length is 2cm, the diameter of the outer tube gradually changes from 6mm to 4cm, and the diameter of the inner tube gradually changes to 3cm, which is conducive to improving the flow rate. Connect the nozzle at this part to input airflow to the nozzle, thereby generating Very stiff airflow.

Figure 4a is a nozzle jacket, Figure 4b is a half-section schematic diagram of the nozzle barrel jacket; the nozzle barrel jacket is used to generate a circular auxiliary protective air flow, the convex part is a cylinder cut by a knife, and there are holes and threads on the cutting surface to connect the gas nozzle valve for input of protective gas. The total length is 125mm, the outer diameter is 12mm, and the inner diameter is 8mm.

Figure 5 is the tail part of the nozzle, the tail part of the nozzle is located at the end of the entire nozzle structure, connecting the inner pipe and the protective gas cylinder for supplying gas to the inner pipe. The structure is shown in Figure 5.

The schematic diagram of the welding process is shown in Figure 10, in which, 7 represents the nozzle, the direction of the big arrow is the welding direction, the air jet direction is 45° from the horizontal, that is, θ is 45°, and the other direction is that the air jet direction is opposite to the welding direction , as indicated by the arrow on the nozzle head. b represents the distance between the nozzle and the plate, which can be set to 0.5mm-5mm.

Claims (4)

1. A protection method for actively regulating and controlling laser welding small holes and a molten pool based on blade-shaped airflow is characterized in that:

the generation of the protective airflow in the shape of a knife edge is to open a gap on the laser nozzle, the gap is a slit when viewed from the side view, and the width h of the slit is 0.01mm-0.05 mm;

the blade-shaped protective airflow splits the steam flow sprayed in the small hole and acts on the deep melting small hole opening, so that the effects of inhibiting the spray plume in the hole from obstructing the light beam transmission and disturbing the molten pool protection are achieved; meanwhile, a raised liquid column in the molten pool is pressed, so that splashing and hump formation are inhibited; by changing the flow rate or the action position of the blade-shaped air flow, the negative effect of the plume steam is inhibited.

2. The protection method for actively regulating and controlling the laser welding small hole and the molten pool based on the blade-shaped airflow is characterized in that:

the thickness of the protective airflow is between 0.1mm and 3mm, the blade length, namely the length vertical to the axial direction of the airflow, is between 1mm and 20mm, and the flow speed is between 1m/s and 300 m/s; the included angle between the axial direction of the blade-shaped protective airflow and the axial direction of the light beam is between 1 and 90 degrees; the projection width of the blade-shaped protective airflow on the plate surface is equal to the thickness of the airflow, and the included angle between the projection and the welding direction is 0-180 degrees.

3. The protection method for actively regulating and controlling the laser welding small hole and the molten pool based on the blade-shaped airflow is characterized in that: the protective gas is argon, helium, nitrogen or a mixed gas of the gases.

4. The protection method for actively regulating and controlling the laser welding small hole and the molten pool based on the blade-shaped airflow is characterized in that: the wavelength of the laser used for welding is between 0.1 and 15 mu m.

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