Laser welding process method for high-reflectivity material part

Abstract

The invention discloses a laser welding process method for high-reflectivity material parts, which comprises the following steps of: 1) processing two to-be-welded high-reflectivity material parts, and processing a groove at the front end of the welding surface of each high-reflectivity material part; the two grooves are used for reflecting incident laser into the matching gap; (2) the welding face and the groove are pretreated, and the roughness of the welding face and the roughness of the groove are improved; and (3) fixing the welding surfaces of the two high-reflectivity material parts treated in the step (1) and the step (2) according to a set matching gap, then controlling laser to enter any groove at a set incident angle, and then controlling the laser to weld the two high-reflectivity material parts to be welded at set laser energy, welding speed and defocusing amount. The part machining difficulty is reduced, the laser utilization efficiency is improved, energy waste is reduced, and meanwhile the welding efficiency and the yield are guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of laser welding and relates to a laser welding process method for parts made of high reflectivity materials. Background Art

[0002] Laser welding technology has been applied to manufacturing fields such as petroleum, chemical industry, atomic energy engineering, aerospace, etc. It has shown excellent performance in welding conventional materials such as carbon structural steel, stainless steel, aluminum alloy, etc. Domestic and foreign scholars have conducted a lot of experimental research on it and accumulated a lot of theoretical experience. However, there is a lack of research on laser welding of copper alloys. The research on the process, joint mechanical properties and metallographic structure of laser welding of copper is also mainly concentrated on thin plates, and there is little research on laser welding process of oxygen-free copper on medium and thick plates.

[0003] Laser welding has excellent performance for conventional materials such as carbon structural steel, stainless steel, and aluminum alloy. However, when laser welding oxygen-free copper, since oxygen-free copper has a high reflectivity to lasers, which can reach more than 90%, most of the laser energy irradiated to the surface of the part is reflected during laser welding, resulting in a waste of laser energy and a very low yield rate, which has an adverse effect on the application of laser welding to oxygen-free copper components.

[0004] In the development of vacuum microwave devices such as electron accelerators and waveguides, the connection of oxygen-free copper parts has problems such as solder accumulation, discoloration, hydrogen absorption, complicated process flow, and uncontrollable quality of welded joints in the commonly used welding methods. The use of inert gas-protected laser welding methods can improve these problems. As a material with high reflectivity to lasers, oxygen-free copper has a low effective utilization rate of laser power when laser welding is used, which is also an objective problem that limits the application and development of laser welding on oxygen-free copper. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a laser welding process method for parts made of high reflectivity materials. The present invention realizes the application of laser welding on parts made of high reflectivity materials such as oxygen-free copper by setting the part structure, pre-treatment process and welding parameters.

[0006] The technical solution of the present invention is:

[0007] A laser welding process for parts made of high reflectivity materials, comprising the following steps:

[0008] 1) Processing two parts made of high reflectivity material to be welded, and processing a groove at the front end of the welding surface of each part made of high reflectivity material; the two grooves are used to reflect the incident laser into the matching gap;

[0009] 2) Pre-treating the welding surface and groove to improve the roughness of the welding surface and groove;

[0010] 3) The welding surfaces of the two high-reflectivity material parts processed in steps 1) and 2) are fixed according to the set matching gap, and then the laser is controlled to be incident on any of the grooves at a set incident angle, and then the laser is controlled to weld the two high-reflectivity material parts to be welded at the set laser energy, welding speed, and defocus amount.

[0011] Furthermore, the fitting gap is no larger than 0.05-0.1 mm; the angle of the groove is 5°-15°, and the depth of the groove is 1-3 mm.

[0012] Furthermore, the surface roughness values ​​of the welding surface and groove are greater than Ra6.3.

[0013] Furthermore, the incident angle is less than 5°, so as to increase the number of reflections of the laser at the groove.

[0014] Furthermore, the laser energy is 1.2 to 3 kW, the welding speed is 1 to 3 m / min, and the defocusing amount is -3 to +3 mm.

[0015] Furthermore, the welding surface and groove are subjected to abrasive grinding, laser etching, blackening treatment or surface coating to make the surface rough.

[0016] Furthermore, the high reflectivity material parts are oxygen-free copper parts, niobium parts, gold parts, and silver parts.

[0017] The advantages of the present invention are as follows:

[0018] The laser welding process method proposed in the present invention reduces the difficulty of parts processing, improves the utilization efficiency of laser, reduces energy waste, and at the same time ensures welding efficiency and yield rate. The application scope is scalable. In addition to the welding of oxygen-free copper, it can also be applied to the welding of other high-reflectivity materials (such as niobium, gold, silver, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of laser beam reflection.

[0020] Figure 2 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention but not to limit the scope of the present invention.

[0022] Taking oxygen-free copper as an example, the welding method of the present invention is as follows: Figure 2 As shown, the steps include:

[0023] 1. Structural design of parts to be welded: including parts matching clearance, groove angle, etc.

[0024] like Figure 1 As shown in the figure, when designing parts, the matching gap of the welding parts of the parts to be welded should be as small as possible, not more than 0.05-0.1mm. A gap that is too large is prone to cause cold welding and low welding strength; a gap that is too small has higher requirements on the processing accuracy and installation process of the parts.

[0025] A groove is made at the welding part of the parts to be welded, with a groove angle of 5°~15° and a groove depth of 1~3mm. This allows the laser beam to be reflected multiple times at the welding part until it reaches the bottom of the weld. The laser energy accumulates at the welding part, solving the problem of low laser energy utilization for high-reflectivity materials such as oxygen-free copper.

[0026] 2. Pretreatment process before welding to improve surface roughness (reduce surface finish): including abrasive grinding, laser etching, blackening treatment, surface coating, etc.

[0027] Pre-treat the welding parts before welding to improve the surface roughness. The roughness value should be greater than Ra6.3 (i.e. the average surface roughness is 6.3 microns), making the surface rougher, thereby reducing the reflectivity of the laser. The treatment process includes abrasive (sandpaper, oilstone, etc.) grinding, laser etching, blackening treatment, surface coating, etc.

[0028] After pretreatment, the parts to be welded are fixed to make the fitting gap as small as possible.

[0029] 3. Use appropriate welding parameters to weld the two parts to be welded. The welding parameters include incident laser angle, laser energy, welding speed, defocus, etc.

[0030] The incident angle should be less than 5° so that the laser beam can irradiate the groove of the parts on the same side, increase the reflection angle, ensure sufficient reflection times at the groove, and improve the utilization rate of laser energy.

[0031] Laser energy directly affects the melting depth of the weld, which can ensure a certain connection strength and sealing requirements. The laser power is 1.2-3kW. Too large a laser power may cause over-melting.

[0032] Under a certain laser power, the slower the welding speed, the more energy is accumulated, the deeper the melting depth is, and the over-melting phenomenon must be prevented. The welding speed is 1-3m / min. If the welding speed is too slow, the laser will stay at the same welding point for a longer time, and the heat will accumulate too much there, which will easily cause over-burning and lead to the scrapping of parts; if the welding speed is too fast, the laser will stay at the same welding point for a shorter time, and the heat will not accumulate enough there, the weld penetration will decrease, and even welding breakpoints will occur, resulting in poor sealing.

[0033] The defocusing amount affects the amount of laser irradiation energy received by the weldment, and also determines the size of the laser spot on the weldment surface, which has a direct impact on the welding depth and weld width. The smaller the defocusing amount, the smaller the spot, the greater the laser power density received by the weldment, the greater the weld penetration, and also causes the metal to evaporate quickly. Set the appropriate defocusing amount -3 to +3mm to obtain the ideal laser power density, thereby obtaining the ideal welding penetration and weld width, and reducing metal evaporation during the welding process.

[0034] Welding parameters such as incident laser angle, laser energy, welding speed, and defocus amount should be set in coordination to ensure a welding penetration depth of 2 to 5 mm and achieve the required welding strength and sealing.

[0035] Although the specific embodiments of the present invention are disclosed for the purpose of illustration, the purpose is to help understand the content of the present invention and implement it accordingly, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the best embodiment, and the scope of the present invention is subject to the scope defined in the claims.

Claims

1. A laser welding process for parts made of high reflectivity materials, comprising the following steps: 1) Processing two parts made of high reflectivity material to be welded, and processing a groove at the front end of the welding surface of each part made of high reflectivity material; the two grooves are used to reflect the incident laser into the matching gap; 2) Pre-treating the welding surface and groove to improve the roughness of the welding surface and groove; 3) The welding surfaces of the two high-reflectivity material parts processed in steps 1) and 2) are fixed according to the set matching gap, and then the laser is controlled to be incident on any of the grooves at a set incident angle, and then the laser is controlled to weld the two high-reflectivity material parts to be welded at the set laser energy, welding speed, and defocus amount.

2. The method according to claim 1, characterized in that The matching gap is no larger than 0.05-0.1 mm; the angle of the groove is 5°-15°, and the depth of the groove is 1-3 mm.

3. The method according to claim 1, characterized in that The surface roughness values ​​of the welding surface and groove are greater than Ra6.

3.

4. The method according to claim 1, 2 or 3, characterized in that: The incident angle is less than 5°, which is used to increase the number of reflections of the laser at the groove.

5. The method according to claim 1, 2 or 3, characterized in that: The laser energy is 1.2 to 3 kW, the welding speed is 1 to 3 m / min, and the defocusing amount is -3 to +3 mm.

6. The method according to claim 1, 2 or 3, characterized in that: The welding surface and groove are subjected to abrasive grinding, laser etching, blackening treatment or surface coating to make the surface rough.

7. The method according to claim 1, 2 or 3, characterized in that: The high reflectivity material parts are oxygen-free copper parts, niobium parts, gold parts and silver parts.

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