CN117921176A - A method for welding thick microcrystalline glass to metal based on ultrafast laser - Google Patents

Abstract

The invention discloses a method for welding large-thickness glass ceramics and metal based on ultrafast laser, and belongs to the technical field of laser welding. The method comprises the following steps: s1, preparing a material; s2, placing the metal to be welded on a processing platform, and placing microcrystalline glass to be welded on the metal; s3, focusing by laser: s4, ultra-fast laser welding: firstly, carrying out laser pre-scanning for a plurality of times in the central area of a sample to be welded, wherein the pulse energy of the pre-scanning laser is lower than the removal threshold value of microcrystalline glass; and performing laser welding scanning for a plurality of times in the central area of the sample to be welded, wherein the pulse energy of the welding scanning laser is higher than that of the pre-scanning laser. The welding process of high-speed scanning is repeated through variable energy, so that the welding stress is effectively reduced, and zero expansion coefficient microcrystalline glass and metal can be reliably connected, so that the microcrystalline glass and the metal are not affected by huge physical parameter differences.

Description

A method for welding thick microcrystalline glass to metal based on ultrafast laser

Technical Field

The invention belongs to the technical field of laser welding, and in particular relates to a method for welding thick microcrystalline glass and metal based on ultrafast laser.

Background technique

Glass has good physical and chemical properties, such as high light transmittance, high mechanical strength, corrosion resistance and friction resistance. It is an excellent material for high-end optical systems, astronomy and satellites, machine vision and life sciences. However, the brittleness and low impact resistance of glass lead to its poor mechanical properties, which seriously limits its application in practical engineering. Joining metals with good elastic-plasticity and high impact resistance with glass can greatly improve their overall mechanical properties. Therefore, glass-metal joining technology is increasingly used in micro-electromechanical systems, medical implants, optical sensors and other fields.

At present, there are many ways to connect glass and metal. Adhesive bonding and active brazing introduce additional fillers to meet the requirements of gap connection. However, adhesives are easy to deform and difficult to cope with complex working environments such as high temperature, humidity and corrosion. Active brazing usually requires high-temperature heating in a vacuum furnace (usually above 700°C), which greatly limits its application scenarios. Connection methods such as matching sealing and anodic bonding realize the connection between glass and metal in the form of plastic deformation or solid atomic diffusion, which is suitable for connection occasions with small deformation. However, its main disadvantage is that the material combination needs to have similar thermal expansion coefficients and the connection strength is low. Traditional laser melting welding is to fuse glass and metal materials to form a joint by locally heating the metal material, but it is easy to cause thermal damage to the substrate and produce cracks during the welding process. Ultrafast lasers have the advantages of small thermal effect and high processing accuracy. They can effectively avoid the problems of thermal damage, accumulation of thermal stress and defects in the long pulse width laser processing process, and can realize the connection of various glass and metal.

Ultrafast lasers have extremely narrow pulse widths and extremely high peak powers, which can induce multi-photon ionization and avalanche ionization of glass materials, and achieve effective absorption of laser energy by glass. Through the thermal accumulation effect of high-repetition-rate ultrafast lasers, glass and metal melt simultaneously to achieve effective connection. Ultrafast laser welding of glass and metal has three major advantages: 1. Wide range of applications, applicable to the connection of various glass and metals; 2. Small heat-affected zone, local precise heating, will not change the properties of materials outside the weld; 3. High welding efficiency, no need for long-term heating and heat preservation.

Zero expansion coefficient microcrystalline glass refers to a glass with LiO ₂ , Al ₂ O ₃ , and SiO ₂ as the main components. After strict controlled crystallization treatment, it forms a composite material composed of negative expansion β-quartz solid solution nanocrystalline phase and positive expansion glass phase. It has excellent optical, thermal, and mechanical properties. It is currently the material with the best dimensional stability in variable temperature environments and is widely used in many fields such as aviation, aerospace, electronics, weapons, ships, and precision machinery. The average thermal expansion coefficient of zero expansion coefficient microcrystalline glass is usually 0±1×10 ^-7 /K, and the average thermal expansion coefficient of the most advanced microcrystalline glass can be 0±0.07×10 ^-7 /K. The thermal expansion coefficient of most metals is usually more than two orders of magnitude higher than that of microcrystalline glass, such as the thermal expansion coefficient of 304 stainless steel is 1.8×10 ^-5 /K. The huge difference in thermal expansion coefficients causes great stress in the welding process of microcrystalline glass and metal, making the glass very easy to produce microcracks or even overall shattering, thus placing strict requirements on heat input and thermal deformation during welding.

For thick (≥70mm) glass-ceramics, the height of the glass increases significantly, which causes interference with the short-focal-length ultrafast laser during processing, thus placing higher requirements on the laser input method. At the same time, the increase in glass thickness also greatly increases the glass's absorption rate of the laser, making the laser energy more easily absorbed by the glass matrix and unable to reach the glass-metal interface, which also severely limits the parameter selection of ultrafast laser welding.

In order to solve the problems of welding stress control and welding process selection caused by the large difference in thermal expansion coefficient and the large thickness of glass in the welding scenario of thick zero-expansion coefficient microcrystalline glass and metal, a simple, reliable and versatile welding method is urgently needed.

Summary of the invention

The purpose of the present invention is to provide a method for welding thick microcrystalline glass to metal based on ultrafast laser, so as to solve the problem that microcrystalline glass and metal with thermal expansion coefficients different by more than two orders of magnitude have large thermal stress during welding and are difficult to connect reliably.

The purpose of the present invention can be achieved through the following technical solutions:

A method for welding thick microcrystalline glass to metal based on ultrafast laser, comprising the following steps:

S1 Material preparation: Clean and dry the glass-ceramics and metal to be welded to remove surface oil stains;

S2: Placing the materials to be welded: placing the metal to be welded flat on the processing platform, and placing the glass-ceramics to be welded on the metal;

S3 laser focus: adjust the horizontal position of the processing platform so that the laser spot is located at the center of the micro-ceramic glass and the metal; adjust the height of the processing platform so that the geometric focus of the laser penetrating the thick micro-ceramic glass is located at the interface between the micro-ceramic glass and the metal;

S4 ultrafast laser welding: First, multiple laser pre-scans are performed in the central area of the sample to be welded, so that metal particles are splashed on the lower surface of the glass; the pulse energy of the pre-scanning laser is lower than the removal threshold of the glass;

Then, multiple laser welding scans are performed in the central area of the sample to be welded, so that the glass and the metal are effectively melted and mixed, and a reliable connection between the glass and the metal is achieved; the pulse energy of the welding scanning laser is higher than the pulse energy of the pre-scanning laser.

As a further solution of the present invention, the thickness of the microcrystalline glass is ≥70 mm.

As a further solution of the present invention, in S1, the cleaning methods for the microcrystalline glass and the metal include ultrasonic cleaning, alcohol cleaning or acetone solvent cleaning.

As a further solution of the present invention, in S2, the gap between the microcrystalline glass to be welded and the metal to be welded is less than 10 μm. The welding gap will directly affect the welding effectiveness and welding strength. The smaller the welding gap, the higher the welding strength.

As a further solution of the present invention, in S3, the laser will be refracted after passing through the glass, causing the laser focus to change. Therefore, the focusing operation needs to consider the impact of laser refraction, and the specific change value needs to be calculated based on the refractive index of the glass used.

As a further solution of the present invention, the ultrafast laser welding equipment includes an ultrafast laser and a large focal length high-speed scanning galvanometer system.

As a further solution of the present invention, in S4, the ultrafast laser selects different welding parameters according to the types of the microcrystalline glass and the metal.

As a further solution of the present invention, in S4, the scanning trajectory of the laser includes a spiral line or a concentric circle.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention provides a method for welding thick microcrystalline glass and metal based on ultrafast laser, adopts a large focal length high-speed scanning galvanometer system, solves the interference problem that may occur in the welding process of thick microcrystalline glass (≥70mm); adopts a welding process with variable energy and repeated high-speed scanning, can achieve simultaneous melting of microcrystalline glass and metal, effectively suppress the generation of thermal stress in the welding process, avoid the generation of defects such as microcracks inside the glass, and achieve effective welding of microcrystalline glass and metal with a difference of more than two orders of magnitude in thermal expansion coefficient. The whole welding process has a small heat input, concentrated heating positions, fewer processing steps, and is easy to achieve high-quality and efficient automated welding.

2. In the laser welding process of the present invention, firstly, under the action of the pre-scanning ultrafast laser pulse with lower energy, the metal effectively absorbs the laser energy and ablates, generating a large number of particles splashing on the lower surface of the glass; however, since the laser energy of the microcrystalline glass is far from reaching the removal threshold, it will not absorb the laser energy through the nonlinear absorption effect; when the metal particles splash onto the lower surface of the glass, the metal particles directly absorb the laser energy and heat up sharply, and then transfer the heat to the glass through heat conduction, thereby reducing the glass removal threshold; secondly, under the action of the welding scanning ultrafast laser pulse with higher energy, the glass undergoes multi-photon ionization and avalanche ionization processes, generating a large number of free electrons, and achieving effective absorption of the laser energy. Under the heat accumulation effect of the high repetition rate pulse, the glass melts, and the metal also melts due to direct absorption of the laser energy. The molten glass and the molten metal are mixed, and the laser spot is cooled away to form a reliable welding joint. Compared with direct welding with constant energy, the melting of glass and metal can be achieved at a lower laser energy, reducing welding stress and thermal effects.

3. The present invention effectively solves the problems of processing interference and internal absorption, and is suitable for the welding of thick microcrystalline glass. It adopts ultrafast laser welding to perform local precise heating, reduce the thermal impact of non-welding parts, and does not affect the material properties of non-welding parts, nor does it affect the normal operation of components around the welding parts. The welding process uses ultrafast laser as a heat source, and there is no need to pre-treat the material. The process is simple and easy to automate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings.

FIG1 is a schematic diagram of a method for welding thick microcrystalline glass to metal based on ultrafast laser according to the present invention;

FIG2 is a schematic diagram showing the relationship between welding steps and pulse energy in the ultrafast laser welding process of the present invention;

FIG3 is a schematic diagram of the welding sample effect obtained by welding in Example 1 of the present invention;

FIG4 is a hand-held test effect diagram of a welding sample obtained by welding 1 according to the present invention;

FIG5 is a schematic diagram of the welding effect of the welding sample obtained by welding in Comparative Example 1 of the present invention;

In the figure: 1. Ultrafast laser; 2. High-speed scanning galvanometer; 3. Ultrafast laser; 4. Microcrystalline glass; 5. Metal.

Detailed ways

The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Please refer to FIG1 , a method for welding thick microcrystalline glass to metal based on ultrafast laser, comprising the following steps:

S1 Material preparation: Clean and dry the glass-ceramics (thickness ≥ 70 mm) and metal to be welded to remove surface oil stains;

S2: Placing the materials to be welded: placing the metal to be welded flat on the processing platform, and placing the glass-ceramics to be welded on the metal, wherein the gap between the glass-ceramics to be welded and the metal to be welded is less than 10 μm;

S3 laser focus: adjust the horizontal position of the processing platform so that the laser spot is located at the center of the micro-ceramic glass and the metal; adjust the height of the processing platform so that the geometric focus of the laser penetrating the thick micro-ceramic glass is located at the interface between the micro-ceramic glass and the metal;

S4 ultrafast laser welding: Please refer to Figure 2. First, perform multiple laser pre-scans in the central area of the sample to be welded, so that metal particles are splashed on the lower surface of the glass; the pulse energy of the pre-scan laser is lower than the removal threshold of the glass;

Then, multiple laser welding scans are performed in the central area of the sample to be welded, so that the glass and the metal are effectively melted and mixed, and a reliable connection between the glass and the metal is achieved; the pulse energy of the welding scanning laser is higher than the pulse energy of the pre-scanning laser.

In a specific implementation case, in S1, the cleaning method of the microcrystalline glass and the metal includes ultrasonic cleaning, alcohol cleaning or acetone solvent cleaning.

In a specific implementation case, in S3, the laser will be refracted after passing through the glass, causing the laser focus to change. Therefore, the focusing operation needs to consider the impact of laser refraction, and the specific change value needs to be calculated based on the refractive index of the glass used.

In a specific implementation case, the ultrafast laser welding equipment includes an ultrafast laser and a large focal length high-speed scanning galvanometer system.

In a specific implementation case, in S4, the ultrafast laser selects different welding parameters according to the types of microcrystalline glass and metal.

In a specific implementation case, in S4, the scanning trajectory of the laser includes a spiral line or concentric circles.

Example 1

Please refer to FIG1 , a method for welding thick microcrystalline glass and metal based on ultrafast laser, wherein a 1 mm thick 304 stainless steel sheet (thermal expansion coefficient 1.8×10 ^-5 /K) and a 70 mm thick zero expansion coefficient microcrystalline glass (thermal expansion coefficient 0±1×10 ^-7 /K) are welded, and the main welding equipment includes an ultrafast laser (wavelength 1030 nm, pulse width 8 ps), a large focal length high-speed scanning galvanometer system (focal length 100 mm); the method includes the following steps:

S1 Material preparation: Clean the glass-ceramic and stainless steel sheets to be welded with alcohol, dry them, and remove surface oil stains;

S2 Placement of materials to be welded: Place the stainless steel sheet to be welded flat on the processing platform, and place the microcrystalline glass to be welded on the stainless steel sheet, with a gap of 8±0.5μm between the two;

S3 laser focus: adjust the horizontal position of the processing platform so that the laser spot is located at the center of the micro-ceramic glass and the stainless steel sheet; adjust the height of the processing platform so that the geometric focus of the laser penetrating the thick micro-ceramic glass is located at the interface between the micro-ceramic glass and the stainless steel sheet;

S4 ultrafast laser welding: Please refer to Figure 2. First, perform multiple spiral path pre-scans in the central area of the sample to be welded, so that the metal particles of the stainless steel sheet are splashed on the lower surface of the microcrystalline glass; the spiral diameter is 2mm, the line spacing is 10μm, the scanning speed is 1000mm/s, and the number of repeated scans is 5 times; pre-scan laser parameters: single pulse energy 2.5μJ, pulse repetition frequency 400kHz;

Then, multiple spiral path welding scans are performed in the central area of the sample to be welded, so that the microcrystalline glass and the stainless steel sheet are effectively melted and mixed, and a reliable connection between the glass and the stainless steel sheet is achieved; the spiral wire diameter is 2mm, the line spacing is 10μm, the scanning speed is 1000mm/s, and the scanning is repeated 5 times; the welding scanning laser parameters are: single pulse energy 18.75μJ, pulse repetition frequency 400kHz.

The effect diagram of the welded sample obtained by welding is shown in Figure 3. The handheld microcrystalline glass is used to detect whether the microcrystalline glass is effectively welded to the stainless steel sheet, as shown in Figure 4. It can be seen from the figure that the microcrystalline glass and the stainless steel sheet are effectively welded, and the shear strength of the welded sample reaches 14.75MPa.

Comparative Example 1

A 1mm thick 304 stainless steel sheet (thermal expansion coefficient 1.8×10 ^-5 /K) and a 70mm thick zero expansion coefficient glass-ceramic sheet (thermal expansion coefficient 0±1×10 ^-7 /K) were welded. The main welding equipment included an ultrafast laser (wavelength 1030nm, pulse width 8ps) and a large focal length high-speed scanning galvanometer system (focal length 100mm); the following steps were included:

S1 Material preparation: Clean the glass-ceramic and stainless steel sheets to be welded with alcohol, dry them, and remove surface oil stains;

S2 Placement of materials to be welded: Place the stainless steel sheet to be welded flat on the processing platform, and place the microcrystalline glass to be welded on the stainless steel sheet, with a gap of 8±0.5μm between the two;

S3 laser focus: adjust the horizontal position of the processing platform so that the laser spot is located at the center of the micro-ceramic glass and the stainless steel sheet; adjust the height of the processing platform so that the geometric focus of the laser penetrating the thick micro-ceramic glass is located at the interface between the micro-ceramic glass and the stainless steel sheet;

S4 ultrafast laser welding: multiple spiral path welding scans are performed in the central area of the sample to be welded, with a spiral diameter of 2mm, a line spacing of 10μm, a scanning speed of 1000mm/s, and repeated scanning times of 5 times; welding scanning laser parameters: single pulse energy 18.75μJ, pulse repetition frequency 400kHz.

The welding sample effect diagram obtained by welding is shown in Figure 4. Due to the use of single energy for welding, effective connection between thick microcrystalline glass and stainless steel sheet cannot be achieved.

It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims (8)

1. The method for welding the high-thickness glass ceramic and the metal based on the ultrafast laser is characterized by comprising the following steps of:

s1, preparation of a material: cleaning glass ceramics and metal to be welded, drying and removing oil stains on the surface;

S2, placing a material to be welded: placing the metal to be welded on a processing platform, and placing microcrystalline glass to be welded on the metal;

S3, focusing by laser: adjusting the horizontal position of the processing platform to enable the laser spot to be positioned at the center of the glass ceramics and the metal; adjusting the height of the processing platform so that the geometric focus of laser passing through the glass ceramics with large thickness is positioned at the interface between the glass ceramics and the metal;

S4, ultra-fast laser welding: firstly, carrying out laser pre-scanning for a plurality of times in the central area of a sample to be welded, wherein the pulse energy of the pre-scanning laser is lower than the removal threshold value of microcrystalline glass;

and performing laser welding scanning for a plurality of times in the central area of the sample to be welded, wherein the pulse energy of the welding scanning laser is higher than that of the pre-scanning laser.

2. The method for welding the high-thickness glass ceramics and the metal based on the ultrafast laser according to claim 1, wherein the thickness of the glass ceramics is more than or equal to 70mm.

3. The method for welding high-thickness glass ceramics and metal based on ultrafast laser according to claim 1, wherein in S1, the cleaning mode of glass ceramics and metal comprises ultrasonic cleaning, alcohol cleaning or acetone solvent cleaning.

4. The method for welding the ultra-fast laser-based large-thickness glass ceramic and the metal according to claim 1, wherein in the step S2, the clearance between the glass ceramic to be welded and the metal to be welded is less than 10 μm.

5. The method for welding the ultra-fast laser-based large-thickness glass ceramic and the metal according to claim 1, wherein in the step S3, the specific value of the laser focus is calculated according to the refractive index of the glass ceramic.

6. The method for welding the high-thickness glass ceramic and the metal based on the ultrafast laser according to claim 1, wherein the ultrafast laser welding equipment comprises an ultrafast laser and a high-focal-length high-speed scanning galvanometer system.

7. The method for welding high-thickness glass ceramics and metals based on ultrafast laser according to claim 1, wherein in S4, the ultrafast laser selects different welding parameters according to different glass ceramics and metal types.

8. The method for welding high-thickness glass ceramic and metal based on ultrafast laser according to claim 1, wherein in S4, the scanning track of the laser comprises a spiral line or concentric circles.