MgAl ply rolling composite brazing filler metal and preparation method and brazing method thereof

Abstract

The invention discloses MgAl ply rolling composite brazing filler metal and a preparation method and a brazing method thereof, belongs to the technical field of magnesium alloy welding materials, and solves the technical problems that magnesium alloy brazing filler metal prepared through a smelting method is insufficient in welding strength, and the thickness of the brazing filler metal is difficult to reduce through secondary machining before welding. According to the solution, Mg rolled plates and Al rolled plates are manufactured through hot rolling after being staggered and stacked according to an Al rolled plate-Mg rolled plate-Al rolled plate sandwich structure, the lengths and the widths of the Mg rolled plates and the Al rolled plates are the same, the thicknesses of the Mg rolled plates and the Al rolled plates are both 0.4-0.6 mm, the thickness of the MgAl pack rolling composite brazing filler metal does not exceed 500 micrometers, the melting temperature is 437-455 DEG C, and the brazing temperature is 460-500 DEG C. The preparation technology is simple, the low-melting-point eutectic structure of the MgAl ply rolling composite brazing filler metal can be generated in a diffusion mode in the brazing process, and brazing filler metal preparation and brazing processes are achieved in one step.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy welding materials, and particularly relates to a MgAl rolled composite solder and a preparation method and a brazing method thereof. Background Art

[0002] Magnesium alloy is the lightest metal material in the current application of structural metal materials. It has the advantages of low specific gravity, high specific strength, easy cutting and processing, and easy recycling. It has significant advantages in achieving lightweight, reducing energy consumption, and reducing environmental pollution. It is known as the "green" engineering material of the 21st century and has attracted more and more attention. In particular, it has extremely important application value and broad application prospects in the fields of electronics, transportation, automobiles, aviation, aerospace, and national defense and military. Therefore, research on metallurgical bonding of magnesium alloys has also received more and more attention.

[0003] Magnesium alloys need to be brazed in some applications in radar and electronics fields. The brazing flux is an important factor affecting brazing. Currently, most magnesium alloy brazing materials are prepared by smelting alloys. The main component of the magnesium alloy brazing materials prepared by smelting is eutectic structure. The brazing materials prepared by smelting method usually need to be processed again to obtain the required brazing material size. However, the eutectic structure of magnesium alloy is very brittle and difficult to process again. In addition, the method of obtaining magnesium alloy brazing materials by smelting alloys is difficult to prepare in batches. Summary of the invention

[0004] The main purpose of the present invention is to overcome the deficiencies in the prior art and solve the technical problems of insufficient welding strength of magnesium alloy solder prepared by smelting method and difficulty in thinning the solder thickness by secondary processing before welding. The present invention provides a MgAl rolled composite solder and a preparation method and a brazing method thereof.

[0005] The design concept of the present invention is: by the method of composite rolling of Mg rolled plate and Al rolled plate, a MgAl rolled composite solder with a thickness of less than 500μm is directly prepared. The solder is "formed first and then formed into properties", and the low melting point eutectic structure will diffuse and generate during the brazing process, and the solder preparation and brazing process can be realized in "one step". The advantage of this method is that it can conveniently and efficiently prepare composite solders with a large area and a thickness of less than 500μm in batches, without the need to reprocess the solder, and the generation of the eutectic structure and the brazing process are integrated. In addition, the solder has a suitable brazing temperature, a simple process, excellent brazing formability, and high joint shear strength. While ensuring the welding connection performance requirements of magnesium alloy structural parts, it can realize the industrial production of magnesium alloy solders.

[0006] The present invention is achieved through the following technical solutions: A MgAl laminated rolled composite solder is prepared by hot rolling after Mg rolled plates and Al rolled plates are alternately laminated in a sandwich structure of Al rolled plates-Mg rolled plates-Al rolled plates. The Mg rolled plates and Al rolled plates have the same length and width, and the thickness of the Mg rolled plates and Al rolled plates are both 0.4-0.6 mm. The thickness of the MgAl laminated rolled composite solder does not exceed 500 μm.

[0007] A method for preparing the MgAl rolled composite solder as described above comprises the following steps: S1. Raw material preparation: First, cut the pure Mg ingot and the pure Al ingot to obtain cast plates with the size of 70 mm in length × 30 mm in width × 1.5 mm in height; then, roll the Mg cast plate and the Al cast plate at 350°C to 400°C, respectively, with a reduction of 15% to 20% per pass, to obtain Mg rolled plates and Al rolled plates with a thickness of 0.4 to 0.6 mm; finally, stack one Mg rolled plate and two Al rolled plates in a sandwich structure of Al rolled plate-Mg rolled plate-Al rolled plate to obtain a solder blank; S2, placing the brazing material prepared in step S1 into a heating furnace, setting the heating temperature to 280-400°C, and keeping the temperature for 2-10 minutes after the temperature reaches the set temperature; S3, sending the solder blank heated in step S2 to a rolling device for multiple rolling processes, with each process having a reduction of 15% to 30% and a total reduction of 50% to 70%, to obtain a MgAl laminated composite solder.

[0008] A brazing method using the MgAl rolled composite brazing filler metal as described above comprises the following steps: S1. First, clean the surface of the magnesium alloy to be brazed to remove impurities, oil stains and oxide film on the surface; then use 80 and 600 mesh metallographic sandpaper to grind the surface to be brazed smooth; finally, rinse the magnesium alloy to be brazed and the MgAl laminated composite brazing material with alcohol and blow dry with cold air for later use; S2, placing the cleaned MgAl rolled composite brazing filler metal between the surfaces to be brazed of the magnesium alloy to be brazed, and then placing it in a brazing mold. In order to improve the efficiency of the brazing filler metal diffusion to generate the eutectic structure and the connection accuracy, the constant vertical pressure applied by the brazing mold is 0.5~5MPa; S3. Place the brazing mold assembled in step S2 as a whole in a vacuum hot pressing welding furnace. First, evacuate the vacuum hot pressing welding furnace to a vacuum degree of 0-10Pa; then, fill the vacuum hot pressing welding furnace with argon gas for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, set the heating rate of the vacuum hot pressing welding furnace to 1°C / min-10°C / min, keep warm for 5-10min every time the temperature rises by 30°C-50°C, and finally the brazing temperature is 460-500°C, the insulation time is 30-120min, and the temperature is cooled to room temperature to complete the brazing of the magnesium alloy material.

[0009] Preferably, in step S2, the constant vertical pressure applied by the brazing mold is 2-3 MPa.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1) The melting temperature of the MgAl rolled composite solder prepared by the present invention is 437-455°C, the brazing temperature is 460-500°C, the thickness of the MgAl rolled composite solder is less than 500 μm, and no secondary processing and thinning is required before brazing; the solder is prepared by a rolling method with mature technology, which is convenient for the industrial transformation of enterprises, and does not require the purchase of new equipment, and can be simply and conveniently mass-produced; 2) The present invention uses the brazing process to control the conversion of MgAl rolled composite brazing filler metal into eutectic structure and the welding of components simultaneously. The brazing filler metal is first converted into eutectic structure with a lower melting point during the brazing process, and then the eutectic structure melts to achieve component welding. This process promotes micro-diffusion of welding components and brazing filler metals, reduces defects such as cracks, pores and inclusions at the weld, has good surface wettability, and fully fills the brazing seam; when welding magnesium and aluminum alloys using the furnace brazing process, no brazing flux is required, and the shear strength of the welded joint is between 43 and 96 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The DSC curve of the MgAl rolled composite solder prepared in Example 1; Figure 2 This is a low-magnification OM photograph of the MgAl rolled composite solder prepared in Example 1. DETAILED DESCRIPTION

[0012] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Example 1

[0013] A method for preparing a MgAl rolled composite solder comprises the following steps: S1. Raw material preparation: First, pure Mg ingots and pure Al ingots (with a purity of 99.9% or more) were cut to obtain cast plates with dimensions of 70 mm in length × 30 mm in width × 1.5 mm in height; then, the Mg cast plate and the Al cast plate were rolled at 350°C, with a reduction of 16% per pass, to obtain Mg rolled plates with a thickness of 0.45 mm and Al rolled plates with a thickness of 0.42 mm; finally, one Mg rolled plate and two Al rolled plates were stacked in an interlaced manner in a sandwich structure of Al rolled plate-Mg rolled plate-Al rolled plate to obtain a solder blank; S2, placing the brazing material prepared in step S1 into a heating furnace, setting the heating temperature to 300°C, and keeping the temperature for 10 minutes after the temperature reaches the set temperature; S3, the solder blank heated in step S2 is sent to a rolling device for multiple rolling processes, with a reduction of 25% in each process and a total reduction of 64%, to obtain a MgAl laminated rolled composite solder, the thickness of which is 457 μm. The DSC curve of the MgAl laminated rolled composite solder is as shown in FIG. Figure 1 As shown, it can be known that the melting point of the composite solder is 452°C.

[0014] A brazing method using the MgAl rolled composite brazing filler metal as described above comprises the following steps: S1. The size of the magnesium alloy to be brazed in this embodiment 1 is 30 mm × 50 mm × 5.7 mm. First, the surface to be brazed of the magnesium alloy to be brazed is cleaned to remove impurities, oil stains and oxide films on the surface; then, the surface to be brazed is polished smooth using 80 and 600 mesh metallographic sandpapers in turn; finally, the magnesium alloy to be brazed and the MgAl laminated composite brazing material are rinsed with alcohol and blown dry with cold air for later use; S2, placing the cleaned MgAl rolled composite brazing material between the surfaces to be brazed of the magnesium alloy to be brazed, and then placing it in a brazing mold, wherein the constant vertical pressure applied by the brazing mold is 2 MPa; S3, placing the brazing mold assembled in step S2 as a whole in a vacuum hot pressing welding furnace. First, evacuate the vacuum hot pressing welding furnace to a vacuum degree of 10Pa; then, fill the vacuum hot pressing welding furnace with argon gas for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, set the vacuum hot pressing welding furnace to a heating rate of 10°C / min, and keep warm for 5 minutes every time the temperature rises by 50°C. The final brazing temperature is 480°C, and the heat preservation time is 60 minutes. Cool to room temperature to complete the brazing of the magnesium alloy material. The low-magnification OM photograph at the weld position is as follows: Figure 2 The MgAl alloy joints obtained by brazing are well connected, and metallographic observation shows no obvious defects such as cracks and pores. The metallurgical bonding of the welding interface is tight, and the room temperature shear strength is 84.3MPa. Example 2

[0015] A method for preparing a MgAl rolled composite solder comprises the following steps: S1. Raw material preparation: First, pure Mg ingots and pure Al ingots (with a purity of 99.9% or more) are cut to obtain cast plates with dimensions of 70 mm in length × 30 mm in width × 1.5 mm in height; then, the Mg cast plate and the Al cast plate are rolled at 380°C, with a reduction of 18% per pass, to obtain Mg rolled plates with a thickness of 0.45 mm and Al rolled plates with a thickness of 0.5 mm; finally, one Mg rolled plate and two Al rolled plates are stacked in an interlaced manner according to a sandwich structure of Al rolled plate-Mg rolled plate-Al rolled plate to obtain a solder blank; S2, placing the brazing material prepared in step S1 into a heating furnace, setting the heating temperature to 310°C, and heating to the set temperature and keeping the temperature for 8 minutes; S3. The solder blank heated in step S2 is sent to a rolling device for multiple rolling processes, with a reduction of 25% in each process and a total reduction of 68%, to obtain a MgAl laminated rolled composite solder having a thickness of 464 μm.

[0016] A brazing method using the MgAl rolled composite brazing filler metal as described above comprises the following steps: S1. The size of the magnesium alloy to be brazed in Example 2 is 30 mm × 50 mm × 5.7 mm. First, the surface to be brazed of the magnesium alloy to be brazed is cleaned to remove impurities, oil stains and oxide films on the surface; then, the surface to be brazed is polished smooth using 80 and 600 mesh metallographic sandpapers in turn; finally, the magnesium alloy to be brazed and the MgAl laminated composite brazing material are rinsed with alcohol and blown dry with cold air for later use; S2, placing the cleaned MgAl rolled composite brazing material between the surfaces to be brazed of the magnesium alloy to be brazed, and then placing it in a brazing mold, wherein the constant vertical pressure applied by the brazing mold is 3 MPa; S3. Place the brazing mold assembled in step S2 as a whole in a vacuum hot pressing welding furnace. First, evacuate the vacuum hot pressing welding furnace to a vacuum degree of 8Pa; then, fill the vacuum hot pressing welding furnace with argon gas for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, set the vacuum hot pressing welding furnace to a heating rate of 8°C / min, keep warm for 6 minutes every time the temperature rises by 50°C, and the final brazing temperature is 480°C, the insulation time is 60 minutes, and the brazing is completed to room temperature. The brazing of the magnesium alloy material is completed. The MgAl alloy joint obtained by brazing is well connected, and metallographic observation shows no obvious defects such as cracks and pores. The welding interface is metallurgically bonded tightly, and the room temperature shear strength is 79.9MPa. Example 3

[0017] A method for preparing a MgAl rolled composite solder comprises the following steps: S1. Raw material preparation: First, pure Mg ingots and pure Al ingots (with a purity of 99.9% or more) are cut to obtain cast plates with dimensions of 70 mm in length × 30 mm in width × 1.5 mm in height; then, the Mg cast plate and the Al cast plate are rolled at 400°C, with a reduction of 20% per pass, to obtain Mg rolled plates with a thickness of 0.51 mm and Al rolled plates with a thickness of 0.42 mm; finally, one Mg rolled plate and two Al rolled plates are stacked in an interlaced manner according to a sandwich structure of Al rolled plate-Mg rolled plate-Al rolled plate to obtain a solder blank; S2, placing the brazing material prepared in step S1 into a heating furnace, setting the heating temperature to 320°C, and heating to the set temperature and keeping the temperature for 10 minutes; S3. The solder blank heated in step S2 is sent to a rolling device for multiple rolling processes, with a reduction of 20% in each process and a total reduction of 64%, to obtain a MgAl laminated rolled composite solder having a thickness of 486 μm.

[0018] A brazing method using the MgAl rolled composite brazing filler metal as described above comprises the following steps: S1. The size of the magnesium alloy to be brazed in Example 3 is 30 mm × 50 mm × 5.7 mm. First, the surface to be brazed of the magnesium alloy to be brazed is cleaned to remove impurities, oil stains and oxide films on the surface; then, the surface to be brazed is polished smooth using 80 and 600 mesh metallographic sandpapers in turn; finally, the magnesium alloy to be brazed and the MgAl laminated composite brazing material are rinsed with alcohol and blown dry with cold air for later use; S2, placing the cleaned MgAl rolled composite brazing material between the surfaces to be brazed of the magnesium alloy to be brazed, and then placing it in a brazing mold, wherein the constant vertical pressure applied by the brazing mold is 5 MPa; S3. Place the brazing mold assembled in step S2 as a whole in a vacuum hot pressing welding furnace. First, evacuate the vacuum hot pressing welding furnace to a vacuum degree of 5 Pa; then, fill the vacuum hot pressing welding furnace with argon gas for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, set the vacuum hot pressing welding furnace to a heating rate of 6°C / min, and keep warm for 5 minutes every time the temperature rises by 50°C. The final brazing temperature is 480°C, the insulation time is 60 minutes, and the brazing is completed to room temperature. The brazing of the magnesium alloy material is completed. The MgAl alloy joint obtained by brazing is well connected, and metallographic observation shows no obvious defects such as cracks and pores. The welding interface is metallurgically bonded tightly, and the room temperature shear strength is 80.1MPa.

[0019] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A MgAl rolled composite brazing material, characterized in that: The Mg rolled plate and the Al rolled plate are alternately stacked in a sandwich structure of Al rolled plate-Mg rolled plate-Al rolled plate and then hot rolled. The length and width of the Mg rolled plate and the Al rolled plate are the same, and the thickness of the Mg rolled plate and the Al rolled plate are both 0.4-0.6 mm. The thickness of the MgAl laminated composite solder does not exceed 500 μm.

2. A method for preparing the MgAl rolled composite solder according to claim 1, characterized in that: The following steps are involved: S1. Raw material preparation: First, cut the pure Mg ingot and the pure Al ingot to obtain cast plates with the size of 70 mm in length × 30 mm in width × 1.5 mm in height; then, roll the Mg cast plate and the Al cast plate at 350°C to 400°C, respectively, with a reduction of 15% to 20% per pass, to obtain Mg rolled plates and Al rolled plates with a thickness of 0.4 to 0.6 mm; finally, stack one Mg rolled plate and two Al rolled plates in a sandwich structure of Al rolled plate-Mg rolled plate-Al rolled plate to obtain a solder blank; S2, placing the brazing material prepared in step S1 into a heating furnace, setting the heating temperature to 280-400°C, and keeping the temperature for 2-10 minutes after the temperature reaches the set temperature; S3, sending the solder blank heated in step S2 to a rolling device for multiple rolling processes, with each process having a reduction of 15% to 30% and a total reduction of 50% to 70%, to obtain a MgAl laminated composite solder.

3. A brazing method using the MgAl rolled composite brazing filler metal as claimed in claim 1, characterized in that: The following steps are involved: S1. First, clean the surface of the magnesium alloy to be brazed to remove impurities, oil stains and oxide film on the surface; then use 80 and 600 mesh metallographic sandpaper to grind the surface to be brazed smooth; finally, rinse the magnesium alloy to be brazed and the MgAl laminated composite brazing material with alcohol and blow dry with cold air for later use; S2, placing the cleaned MgAl rolled composite brazing material between the surfaces to be brazed of the magnesium alloy to be brazed, and then placing it in a brazing mold, wherein the constant vertical pressure applied by the brazing mold is 0.5-5 MPa; S3. Place the brazing mold assembled in step S2 as a whole in a vacuum hot pressing welding furnace. First, evacuate the vacuum hot pressing welding furnace to a vacuum degree of 0-10Pa; then, fill the vacuum hot pressing welding furnace with argon gas for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, set the heating rate of the vacuum hot pressing welding furnace to 1°C / min-10°C / min, keep warm for 5-10min every time the temperature rises by 30°C-50°C, and finally the brazing temperature is 460-500°C, the insulation time is 30-120min, and the temperature is cooled to room temperature to complete the brazing of the magnesium alloy material.

4. The brazing method of the MgAl rolled composite brazing material according to claim 3, characterized in that: In step S2, the constant vertical pressure applied by the brazing mold is 2-3 MPa.

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