CN110499503B

CN110499503B - Efficient double-beam light inner coaxial powder feeding cladding head light path structure and processing method

Info

Publication number: CN110499503B
Application number: CN201810467738.7A
Authority: CN
Inventors: 孔源
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-05-16
Filing date: 2018-05-16
Publication date: 2021-10-01
Anticipated expiration: 2038-05-16
Also published as: CN110499503A

Abstract

The invention relates to a high-efficiency double-beam light inner coaxial powder feeding cladding head light path structure and a processing addition method, which comprise a first convex lens, a first reflector, a beam splitting prism, a second reflector, a conical mirror, a beam splitting and expanding unit, a third reflector, a beam converging unit, a second convex lens and a third convex lens, wherein the first convex lens receives a first laser beam, the first laser beam is output and converged to the beam splitting prism, the beam splitting prism outputs two beams of light, the first beam of light is converged to form a solid light spot through the third convex lens via the first reflector, and the second beam of light enters the second reflector; the second reflector receives the second laser beam, and the second laser beam are mixed after being reflected by the conical mirror and enter the beam splitting and expanding unit; the light rays output by the beam splitting and expanding unit output hollow light spots through the third reflector, the beam converging unit and the second convex lens. The invention reflects the light spot at the rear part into a solid square light spot for secondary scanning through the light path design, thereby reducing the formation defects of poor fusion, inclusion and air holes and the like caused by overlarge powder feeding amount.

Description

Efficient double-beam light inner coaxial powder feeding cladding head light path structure and processing method

Technical Field

The invention relates to a laser powder feeding technology, in particular to a high-efficiency double-beam light inner coaxial powder feeding cladding head light path structure and a processing method.

Background

The laser melting deposition technology is one of additive manufacturing technologies, and is characterized in that a high-power laser beam is adopted to form a molten pool on the surface of a processed substrate, and simultaneously, metal powder conveyed by shielding gas is conveyed into the molten pool through a coaxial powder feeding cladding head to be mutually fused to form a cladding layer. And (3) depositing a cladding layer on the surface of the substrate along with the relative movement of the laser beam and the substrate according to a preset processing track, wherein when the laser processing finishes one layer of deposition, the coaxial nozzle translates upwards by the height of one layer relative to the substrate, and the next layer is continuously deposited until the preparation of the part is finished. Mainly applied to four fields: surface strengthening of parts and tools; the reconstruction and repair of damaged parts and tools; processing and manufacturing a multi-metal material composite workpiece; and (3) direct forming and manufacturing of complex large-sized workpieces.

The laser melting deposition technology is characterized in that:

(1) the LMD technology uses a laser with kilowatt level or more, and the forming speed is more than thirty times faster than that of the SLM technology;

(2) the adopted laser has a large focusing spot which is generally more than 1mm, and a metallurgically bonded compact metal entity can be obtained, but the size precision (plus or minus 1mm error) and the surface finish quality of the compact metal entity are general and can be used after further machining.

(3) The material has wide application range, and can be made of stainless steel, titanium, nickel, cobalt-chromium alloy and other powders;

(4) the laser cladding, laser printing and other processing technologies are realized, and one machine has multiple functions;

(5) the utilization rate of the powder is not high;

therefore, the coaxial powder feeding cladding head is a core process component of a laser melting deposition technology, and determines key indexes of powder utilization rate, forming precision, forming efficiency, laser energy distribution and the like.

The present coaxial powder feeding technology studied at home and abroad can be divided into two types of coaxial powder feeding outside light and coaxial powder feeding inside light. These two powder feeding methods have their own advantages and limitations for laser cladding processes, and will be described and compared in detail below.

The coaxial powder feeding outside the light is a powder feeding mode that a laser beam is used as a central axis, a plurality of carrier gas powder feeding nozzles are uniformly and symmetrically distributed in the circumferential direction of the laser beam, and the extension central line of a powder feeding pipeline is converged at one point on the central axis of the laser beam. As the principle is as shown in figure 1, the powder flow is symmetrically distributed, and on the premise that the powder flow is uniformly distributed and completely concentric with the laser beam, all directions have no difference, namely the problem of the directionality of lateral powder feeding can be solved in the forming process, so that the forming of parts with complex shapes can be completed. Meanwhile, the coaxial powder feeding outside the light can form an inert gas protection ring near the molten pool, so that the oxidation of the metal powder is effectively prevented. However, since the structure is relatively complicated and the powder flow and the gas flow are mutually influenced, the control of the powder flow is relatively difficult, and particularly, the powder is difficult to be gathered in a small area, and the powder utilization rate is low. At present, most of powder feeding heads adopt an optical outer coaxial powder feeding technology.

Aiming at the requirements of the laser cladding technology on the powder feeding technology and the defects of the coaxial powder feeding mode outside the light, the prior hollow laser inside-light powder feeding laser cladding process and device exist, and the schematic diagram of the principle is shown in figure 2. The powder feeding mode has the following characteristics: 1) the light path system utilizes a spectroscope to match with a condenser lens to obtain a hollow inverted cone-shaped annular focusing laser beam, a single powder feeding pipe is arranged in the hollow part, powder falls vertically in the middle, and the annular laser beam surrounds and surrounds the powder flow. 2) The focusing system employs a mirror instead of a conventional transparent mirror. Because the reflection focusing focal length is longer, the distance between the optical lens and the processing area is longer, the optical lens can be effectively protected, and the energy loss is mainly reflected in the temperature rise of the mirror, so that the energy loss can be greatly reduced. Different from the traditional coaxial powder feeding, the coaxial powder feeding mode in light easily realizes the true coaxial of the laser beam and the powder beam, and the light beam surrounding light beam is converted into the light beam surrounding powder beam, so that the precision of light-powder coupling is greatly improved, and the surface quality of a formed part and the powder utilization rate are greatly improved.

Although the powder feeding mode in light improves the utilization rate of powder, the existing feeding cladding head in light cannot be used under the action of high-power laser because of the structure and cooling problems, the main reason is caused by the size of a bracket connected with the inner wall of the cladding head inside the cladding head, and if the size of the bracket is too small, the problems of powder feeding amount and a cooling channel cannot be solved. Otherwise, the problem of spot integrity cannot be solved.

Disclosure of Invention

Aiming at the defects that the light path of the powder feeding cladding head in the prior art cannot solve the problem of light spot integrity and the like, the invention aims to solve the problem of providing a high-efficiency double-beam light inner coaxial powder feeding cladding head light path structure and a processing method which can give consideration to both the utilization rate of powder and the use of high-power laser.

In order to solve the technical problems, the invention adopts the technical scheme that:

the invention relates to a high-efficiency double-beam light inner coaxial powder feeding cladding head light path structure which comprises a first convex lens, a first reflector, a beam splitter prism, a second reflector, a conical mirror, a beam splitting and expanding unit, a fifth reflector, a beam converging unit, a second convex lens and a third convex lens, wherein the first convex lens receives a first laser beam and outputs converging light to the beam splitter prism; the second reflector also receives another laser beam, namely a second laser beam, and the second laser beam are mixed and enter the beam splitting and expanding unit after being reflected by the conical mirror; and the light rays output by the light splitting and beam expanding unit output hollow light spots after passing through the fifth reflector, the beam converging unit and the second convex lens.

The second reflector is a hollow cylindrical reflector, the interior of the second reflector comprises two communicated and vertical hollow cylindrical light channels, the exterior of the second reflector is a reflecting surface, the two communicated and vertical hollow cylindrical light channels respectively form an angle of 30-60 degrees with the reflecting surface, and a through hole is formed in the reflecting surface.

The beam splitting and expanding unit comprises a first prism, a third reflector and a fourth reflector, wherein the third reflector and the fourth reflector are symmetrically arranged on two sides of the first prism, the first prism receives mixed light output by the second reflector, and the mixed light enters the fifth reflector after being reflected by the third reflector and the fourth reflector.

The beam-condensing unit comprises a second prism, a sixth reflector and a seventh reflector, wherein the sixth reflector and the seventh reflector are symmetrically arranged on two sides of the second prism.

And the fifth reflector, the second prism of the beam bunching unit and the second convex lens are provided with through holes, and the through holes are coaxially arranged in the vertical direction.

The invention relates to a high-efficiency double-beam light inner coaxial powder feeding cladding head light path processing method, which comprises the following steps:

1) electrifying the laser, and adopting an optical inner coaxial powder feeding mode, and utilizing a double-beam optical inner coaxial powder feeding cladding head to enable laser output by the laser to be incident to a beam splitter prism through a first convex lens to be divided into a front beam and a rear beam;

2) the first beam of light positioned in front forms a hollow square light spot through the light path beam of the double-beam light inner coaxial powder feeding cladding head, so that the laser light spot is larger than the powder spot, and the size of a molten pool is increased;

3) through the light path of the double-beam coaxial powder feeding cladding head, the second beam of light positioned at the rear part is reflected into a solid square light spot for secondary scanning, and the defect of poor fusion and inclusion air hole formation caused by overlarge powder feeding amount is reduced.

The invention also comprises the following steps:

before the processing starts, the distance between the two light spots is adjusted;

selectively shading light at the end of the starting, turning and scanning routes by using an automatic shading plate;

the power of the front and back double-spot light beams is adjusted on the multi-input light path, so that the forming quality is convenient to control.

The invention has the following beneficial effects and advantages:

1. the invention adopts an optical inner coaxial powder feeding mode, divides high-power laser into front and rear two lights by using a brand new light path design, designs the brand new light path to enable the front laser to be a hollow square light spot, thus the laser light spot is slightly larger than the powder spot, the size of a molten pool is increased, more powder enters the molten pool, and meanwhile, the laser power is increased to enable the powder to be melted or semi-melted in the flying process, thereby reducing rebound. Meanwhile, the light spot positioned at the rear part is reflected into a solid square light spot for secondary scanning through the light path design, so that the forming defects of poor fusion, inclusion, air holes and the like caused by overlarge powder feeding amount are reduced.

2. The invention takes the utilization rate of powder and the problem of use under high-power laser into consideration, and is a novel optical path and structure, so that more powder enters a molten pool, the powder keeps a molten or semi-molten state when flying in the air, and the powder does not bounce when entering the molten pool or reaching the surface of a base material.

Drawings

FIG. 1 is a schematic diagram of optical-external coaxial powder feeding in the prior art;

FIG. 2 is a schematic diagram of optical-internal coaxial powder feeding in the prior art;

FIG. 3 is a light path diagram of a dual-beam optical internal powder feeding cladding head according to the present invention;

FIG. 4 is a diagram of an optical path of a beam splitting and expanding unit according to the present invention;

FIG. 5 is a light path diagram of a beam focusing unit according to the present invention;

FIG. 6 is a three-dimensional view of an optical device and a light spot diagram according to the present invention.

The optical system comprises a light source, a first lens, a second lens, a first reflector, a beam splitting and expanding unit, a second lens, a conical lens, a beam converging unit, a beam splitting and expanding unit, a first prism, a third reflector, a fourth reflector, a fifth reflector, a beam converging unit, a second prism, a sixth reflector, a seventh reflector, a sixth lens, a seventh reflector, a second lens and a third lens, wherein 1 is the first convex lens, 2 is the first reflector, 3 is the beam splitting prism, 4 is the second reflector, 5 is the conical lens, 6 is the beam splitting and expanding unit, 601 is the first prism, 602 is the third reflector, 603 is the fourth reflector, 7 is the fifth reflector, 8 is the beam converging unit, 801 is the second prism, 802 is the sixth reflector, 803 is the seventh reflector, 9 is the second convex lens, and 10 is the third convex lens.

Detailed Description

The invention is further elucidated with reference to the accompanying drawings.

As shown in fig. 3, the high-efficiency dual-beam optical inner coaxial powder feeding cladding head optical path structure of the invention comprises a first convex lens 1, a first reflector 2, a beam splitter prism 3, a second reflector 4, a conical mirror 5, a beam splitting and expanding unit 6, a fifth reflector 7, a beam converging unit 8, a second convex lens 9 and a third convex lens 10, wherein the first convex lens receives a first laser beam and outputs a converged light to the beam splitter prism 3, the beam splitter prism 3 outputs two beams of light, the first beam of light is converged by the third convex lens 10 after being reflected by the first reflector 2 to form a solid light spot, and the second beam of light enters the second reflector 4; the second reflecting mirror 4 also receives another laser beam, namely a second laser beam, and the second laser beam are mixed and enter the beam splitting and expanding unit 6 after being reflected by the conical mirror 5; the light output by the beam splitting and expanding unit 6 passes through a fifth reflector 7, a beam converging unit 8 and a second convex lens 9, and then a hollow light spot is output.

In this embodiment, the second reflector 4 is a hollow cylindrical reflector, the interior of the second reflector includes two intercommunicated and perpendicular hollow cylindrical optical channels, the exterior of the second reflector is a reflective surface, the two intercommunicated and perpendicular hollow cylindrical optical channels respectively form an angle of 30-60 degrees with the reflective surface (in this embodiment, an angle of 45 degrees), and a through hole is formed at the reflective surface.

As shown in fig. 4, the second reflecting mirror 4 has a cylindrical body, a reflecting surface of the second reflecting mirror is at an angle of 45 ° to the axial direction of the cylindrical body, and the cylindrical body has three holes, wherein a through hole is formed on the central axis of the reflecting surface, and the through hole is directly connected to the end surface of the cylindrical body and is used for introducing the second beam of light split by the beam splitter prism 3; and a through hole is arranged on the reflecting surface in the direction vertical to the central shaft, and is directly communicated to the position of the cylindrical cambered surface for introducing another laser beam.

The beam splitting and expanding unit 6 includes a first prism 601 and third and

fourth reflectors

602 and 603, wherein the third and

fourth reflectors

602 and 603 are symmetrically disposed on two sides of the first prism 601, the first prism 601 receives the mixed light outputted by the second reflector 4, and the mixed light enters the fifth reflector 7 after being reflected by the third and

fourth reflectors

602 and 603.

The beam focusing unit 8 includes a second prism 801, a sixth mirror 802 and a seventh mirror 803, wherein the sixth mirror 802 and the seventh mirror 803 are symmetrically disposed on two sides of the second prism 801.

The fifth reflector 7, the second prism 801 of the beam focusing unit 8 and the second convex lens 9 are all provided with through holes, and the through holes are coaxially arranged in the vertical direction.

The beam splitter prism 3 splits the light beam into two parts, wherein one part, namely the first light beam, passes through the first reflecting mirror 2 and the third convex lens 10 to form a solid light spot. The other part of the second beam of laser light passes through the hollow cylindrical reflector 4 and is mixed with the other laser beam reflected by the conical mirror 5 through the reflector 4 to reach the beam splitting and expanding unit 6 for expanding, and the main function is to change the solid laser beam into a hollow laser beam. The hollow laser beam reaches the bunching unit 8 through a fifth reflector 7 (the fifth reflector 7 is provided with a hole for reserving a powder feeding/filament tube), and the bunching unit has the function of bunching light spots with large hollow part areas and strengthening the duty ratio of the hollow light spots. The hollow light beams are converged into a hollow light spot by the hollow lens of the second prism 801. The resulting light spot and overall light path three-dimensional diagram of the present invention is shown in fig. 4.

The double-beam coaxial powder feeding cladding head in light of the invention is matched with the processing technology, can realize two times of scanning in short time, realizes optical feeding in the first time of scanning, and improves the utilization rate of powder; the defects of inclusion, poor fusion and the like are eliminated by the second scanning, the advantages of an LMD (laser melting deposition) technology and an SLM (selective laser melting) technology are achieved, the deposition efficiency is high, the powder utilization rate can reach more than 80%, cladding layers can be well combined under the action of high-power laser (more than 6000 w), the mechanical property is excellent, and the height of the cladding layers is controllable.

The invention adopts an optical inner coaxial powder feeding mode, divides high-power laser into front and rear two lights by using a brand new light path design, designs the brand new light path to enable the front laser to be a hollow square light spot, thus the laser light spot is slightly larger than the powder spot, the size of a molten pool is increased, more powder enters the molten pool, and meanwhile, the laser power is increased to enable the powder to be melted or semi-melted in the flying process, thereby reducing rebound. Meanwhile, the light spot positioned at the rear part is reflected into a solid square light spot for secondary scanning through the light path design, so that the forming defects of poor fusion, inclusion, air holes and the like caused by overlarge powder feeding amount are reduced.

In order to solve the problem of the directionality of light spots, a steering head can be added at the joint of the cladding head and the machine tool.

1) electrifying the laser, and adopting an optical inner coaxial powder feeding mode, and utilizing a double-beam optical inner coaxial powder feeding cladding head to enable laser output by the laser to enter a beam splitter prism 3 through a first convex lens 1 to be split into a front beam and a rear beam;

3) through the light path of the double-beam coaxial powder feeding cladding head, the second beam of light positioned at the rear part is reflected and converged into a solid square light spot for secondary scanning, so that the defect of poor fusion and inclusion air hole formation caused by overlarge powder feeding amount is reduced.

The invention also comprises the following steps:

The double-beam scanning interval is short, so that the laser can be used under the condition of relatively low laser power on the premise of ensuring that the cladding material is melted.

The invention adopts the principle of optical internal powder feeding, the light spot is larger than the powder spot, the size of a formed molten pool is relatively larger, more powder enters the molten pool in unit time, the nucleation rate is increased, the grain refinement is facilitated, and the mechanical property of a cladding layer is improved; double-beam scanning is adopted, the temperature gradient in the forming process is smoothed to a certain extent, the residual stress is reduced, and the deformation and cracking of the cladding layer are inhibited; the secondary scanning enables the cladding layer to be remelted, the solidification time is increased, bubbles carried by powder entering a molten pool have sufficient time to escape, pores of the cladding layer are reduced, and the density of the cladding layer is increased.

Claims

1. The utility model provides a coaxial powder feeding melts and covers first light path structure in high-efficient two beam light, its characterized in that: the laser beam splitter comprises a first convex lens, a first reflector, a beam splitter prism, a second reflector, a conical mirror, a beam splitting and expanding unit, a fifth reflector, a beam converging unit, a second convex lens and a third convex lens, wherein the first convex lens receives a first laser beam and outputs converging light to the beam splitter prism; the second reflector also receives another laser beam, namely a second laser beam, and the second laser beam are mixed and enter the beam splitting and expanding unit after being reflected by the conical mirror; and the light rays output by the light splitting and beam expanding unit output hollow light spots after passing through the fifth reflector, the beam converging unit and the second convex lens.

2. The high-efficiency double-beam coaxial powder feeding cladding head optical path structure in the light of claim 1 is characterized in that: the second reflector is a hollow cylindrical reflector, the interior of the second reflector comprises two communicated and vertical hollow cylindrical light channels, the exterior of the second reflector is a reflecting surface, the two communicated and vertical hollow cylindrical light channels respectively form an angle of 30-60 degrees with the reflecting surface, and a through hole is formed in the reflecting surface.

3. The high-efficiency double-beam coaxial powder feeding cladding head optical path structure in the light of claim 1 is characterized in that: the beam splitting and expanding unit comprises a first prism, a third reflector and a fourth reflector, wherein the third reflector and the fourth reflector are symmetrically arranged on two sides of the first prism, the first prism receives mixed light output by the second reflector, and the mixed light enters the fifth reflector after being reflected by the third reflector and the fourth reflector.

4. The high-efficiency double-beam coaxial powder feeding cladding head optical path structure in the light of claim 1 is characterized in that: the beam-condensing unit comprises a second prism, a sixth reflector and a seventh reflector, wherein the sixth reflector and the seventh reflector are symmetrically arranged on two sides of the second prism.

5. The high-efficiency double-beam coaxial powder feeding cladding head optical path structure in the light of claim 4 is characterized in that: and the fifth reflector, the second prism of the beam bunching unit and the second convex lens are provided with through holes, and the through holes are coaxially arranged in the vertical direction.

6. The method for processing the optical path of the high-efficiency double-beam optical inner coaxial powder feeding cladding head according to any one of claims 1 to 5, characterized by comprising the following steps:

3) through the light path of the double-beam coaxial powder feeding cladding head, the second beam of light positioned at the rear part is reflected into a solid square light spot for secondary scanning, so that the defect of poor fusion and inclusion air hole formation caused by overlarge powder feeding amount is reduced;

further comprising the steps of: