Preparation method and brazing method of SiC-reinforced MgAl ply rolling composite brazing filler metal

Abstract

The invention discloses a preparation method and a brazing method of SiC reinforced MgAl ply rolling composite brazing filler metal, belongs to the technical field of magnesium alloy welding materials, and solves the technical problem that the welding strength of magnesium alloy brazing filler metal prepared through a smelting method is insufficient. A SiC-alcoholic solution is uniformly sprayed and deposited on the surfaces of an Mg rolled plate and two Al rolled plates, hot rolling is adopted after the Al rolled plates, the Mg rolled plates and the Al rolled plates are stacked in a staggered mode according to the sandwich structure of the Al rolled plates, the Mg rolled plates and the Al rolled plates, the SiC-reinforced MgAl ply rolling composite brazing filler metal with the thickness not larger than 500 micrometers is prepared, the melting temperature ranges from 437 DEG C to 455 DEG C, and the brazing temperature ranges from 460 DEG C to 500 DEG C. The preparation process is simple, silicon carbide is uniformly distributed among layers and is not obviously agglomerated, an eutectic structure at a brazing seam can be obviously refined, and the shearing strength of a welded joint is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy welding materials, and specifically relates to a preparation method and a brazing method of a SiC reinforced MgAl rolled composite brazing filler metal. Background Art

[0002] With the development of human society, the load on the earth's resources and environment has become increasingly severe. The sustainable use of natural resources and the environment has become a key issue in today's human society. Lightweight and green economy are the basic principles and requirements for achieving energy conservation and emission reduction and improving resource utilization. Magnesium alloy materials are the lightest metal materials in structural metals. They play a significant role in achieving lightweight, reducing energy consumption, and reducing environmental pollution. The application prospects of magnesium alloys are increasingly broad, so the connection of magnesium alloys is also receiving more and more attention.

[0003] Among the many connection methods, brazing is an important way to achieve the connection of magnesium alloy components. The traditional magnesium alloy brazing filler metal is obtained by melting the alloy together. The brazing filler metal is often difficult to form an effective connection with the magnesium alloy during brazing, and the joint strength is not ideal. Although the strength of the brazed joint can be enhanced by using a brazing flux and adding reinforcing particles to the brazing filler metal, the use of the brazing flux will also cause poor brazing formability, and the brazing filler metal obtained by melting the alloy and introducing the reinforcing body at the same time still cannot significantly improve the strength of the brazed joint. In addition, the main component of the molten alloy is the eutectic alloy, and the eutectic structure of the magnesium alloy is very brittle, making it difficult to perform secondary processing, and it is difficult to prepare the brazing filler metal in batches. Therefore, the development of a magnesium alloy brazing filler metal that can be efficiently connected with magnesium alloys, has good welding formability, and can be prepared in batches has become an urgent problem to be solved in the field of magnesium alloy welding. 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 problem of insufficient welding strength of magnesium alloy solder prepared by smelting method. The present invention provides a preparation method and brazing method of SiC reinforced MgAl rolled composite solder.

[0005] The design concept of the present invention is: to introduce SiC between the Mg rolled plate and the Al rolled plate pThe SiC-reinforced MgAl rolled composite brazing filler metal with a thickness of less than 500 μm is directly prepared by composite rolling of Mg rolled plate and Al rolled plate. The advantage of this method is that it can conveniently and efficiently prepare composite brazing filler metals with a large area and a thickness of less than 500 μm in batches, without the need for reprocessing the brazing filler metal, the formation of eutectic structure and the brazing process are integrated, and the introduced reinforcing particles can greatly improve the welding performance of magnesium alloys. In addition, the brazing temperature of the brazing filler metal is suitable, the process is simple, the brazing formability is excellent, and the joint shear strength is high. While ensuring the welding connection performance requirements of magnesium alloy structural parts, it can realize the industrial production of magnesium alloy brazing filler metals.

[0006] The present invention is implemented by the following technical scheme: A method for preparing SiC reinforced MgAl rolled composite solder comprises the following steps: S1. Raw material preparation: First, cut the pure Mg ingot and the pure Al ingot to obtain the 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~400°C respectively, with a reduction of 15%~20% per pass, to obtain Mg rolled plates and Al rolled plates with a thickness of 0.4~0.6 mm; finally, prepare the raw materials according to the ratio of the number of Al rolled plates to Mg rolled plates of 2:1, and reserve them for use in the next step; S2. Prepare a silicon carbide-alcohol solution, wherein the particle size of the silicon carbide particles is 1-10 μm, and the mass fraction of the silicon carbide particles in the alcohol is 0.1%-10%. Stir evenly and keep it for use in the next step; S3, uniformly spraying and depositing the silicon carbide-alcohol solution prepared in step S2 onto the surfaces of the Mg rolled plate and the Al rolled plate prepared in step S1, and then staggering and stacking 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; S4, placing the brazing material prepared in step S3 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; S5. Send the solder blank heated in step S4 to a rolling device for multiple rolling processes, with a reduction of 15% to 30% in each process and a total reduction of 50% to 70% to obtain a SiC-reinforced MgAl laminated-rolled composite solder, wherein the thickness of the SiC-reinforced MgAl laminated-rolled composite solder does not exceed 500 μm.

[0007] Preferably, the melting temperature of the prepared SiC reinforced MgAl rolled composite brazing filler metal is 437-455°C, and the brazing temperature is 460-500°C, and it is used for brazing magnesium-aluminum alloys with a solidus temperature above 500°C.

[0008] A brazing method for SiC reinforced MgAl rolled composite brazing material 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 SiC reinforced MgAl rolled composite brazing material with alcohol and blow dry with cold air for later use; S2. Place the cleaned SiC reinforced MgAl rolled composite brazing filler metal between the surfaces of the magnesium alloy to be brazed, and then place it in a brazing mold. To improve the efficiency of the brazing filler metal diffusion to generate the eutectic structure and the connection accuracy, the brazing mold applies a constant vertical pressure of 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.

[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 preparation of SiC reinforced MgAl rolled composite brazing alloy by the present invention is convenient and easy to operate. p The introduction is simple and the distribution is uniform, no flux is required during welding, and the strength of the welded joint can be greatly improved; 2) The melting temperature of the SiC-reinforced MgAl rolled composite brazing filler metal prepared by the present invention is 437-455°C, and the brazing temperature is 460-500°C. It can be used for brazing of magnesium-aluminum alloys with a solidus temperature above 500°C. The brazing filler metal thickness is less than 500 μm, and no secondary processing and thinning is required, so mass production can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a low-magnification OM photograph of magnesium alloy brazing using the SiC reinforced MgAl rolled composite brazing filler metal prepared in Example 2. 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 SiC reinforced MgAl rolled composite solder comprises the following steps: S1. Raw material preparation: First, pure Mg ingots and pure Al ingots (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 350°C, with a reduction of 15% per pass, to obtain Mg rolled plates with a thickness of 0.52 mm and Al rolled plates with a thickness of 0.5 mm; finally, raw materials are prepared according to a ratio of 2:1 between the number of Al rolled plates and the number of Mg rolled plates, which are reserved for use in the following step; S2, prepare a silicon carbide-alcohol solution, the particle size of the silicon carbide particles is 5 μm, the mass fraction of the silicon carbide particles in the alcohol is 0.1%, stir evenly and keep it for use in the next step; S3, uniformly spraying and depositing the silicon carbide-alcohol solution prepared in step S2 onto the surfaces of the Mg rolled plate and the Al rolled plate prepared in step S1, and then staggering and stacking 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; S4, placing the brazing material prepared in step S3 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; S5. The solder blank heated in step S4 is sent to a rolling device for multiple rolling processes, with a reduction of 26% in each process and a total reduction of 68% to obtain a SiC-reinforced MgAl laminated composite solder. The SiC-reinforced MgAl laminated composite solder has a thickness of 486 μm, a melting temperature of 437-455°C, and a brazing temperature of 460-500°C. It is used for brazing magnesium-aluminum alloys with a solidus temperature above 500°C.

[0014] A brazing method for SiC reinforced MgAl rolled composite brazing material comprises the following steps: S1. The size of the magnesium alloy to be brazed in Example 1 is 50 mm in length × 30 mm in width × 5.7 mm in thickness. 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 SiC-reinforced MgAl rolled composite brazing material are rinsed with alcohol and blown dry with cold air for later use; S2, placing the cleaned SiC reinforced MgAl rolled composite brazing material between the to-be-welded surfaces 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, the brazing mold assembled in step S2 is placed in a vacuum hot pressing welding furnace. First, the vacuum hot pressing welding furnace is evacuated to a vacuum degree of 10Pa; then, the vacuum hot pressing welding furnace is filled with argon gas for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, the heating rate of the vacuum hot pressing welding furnace is set to 10℃ / min, and the temperature is kept for 5min for each 50℃ increase. The final brazing temperature is 470℃, the insulation time is 60min, and the brazing of the magnesium alloy material is completed. The MgAl alloy joint obtained by brazing is well connected, and there are no obvious defects such as cracks and pores in metallographic observation. The metallographic bonding of the welding interface is tight, and the room temperature shear strength is 65.7MPa. Example 2

[0015] A method for preparing a SiC reinforced MgAl rolled composite solder comprises the following steps: S1. Raw material preparation: First, pure Mg ingots and pure Al ingots (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 0.5 mm and Al rolled plates with a thickness of 0.52 mm; finally, raw materials are prepared according to a ratio of 2:1 between the number of Al rolled plates and the number of Mg rolled plates, which are reserved for use in the following step; S2, prepare a silicon carbide-alcohol solution, the particle size of the silicon carbide particles is 5 μm, the mass fraction of the silicon carbide particles in the alcohol is 3%, stir evenly and keep it for use in the next step; S3, uniformly spraying and depositing the silicon carbide-alcohol solution prepared in step S2 onto the surfaces of the Mg rolled plate and the Al rolled plate prepared in step S1, and then staggering and stacking 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; S4, placing the brazing material prepared in step S3 into a heating furnace, setting the heating temperature to 310°C, and heating to the set temperature and keeping the temperature for 8 minutes; S5. Send the solder blank heated in step S4 to a rolling device for multiple rolling processes, with a reduction of 30% in each process and a total reduction of 70% to obtain a SiC-reinforced MgAl laminated composite solder having a thickness of 462 μm.

[0016] A brazing method for SiC reinforced MgAl rolled composite brazing material comprises the following steps: S1. The size of the magnesium alloy to be brazed in Example 2 is 50 mm in length × 30 mm in width × 5.7 mm in thickness. 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 SiC-reinforced MgAl rolled composite brazing material are rinsed with alcohol and blown dry with cold air for later use; S2, placing the cleaned SiC reinforced MgAl rolled composite brazing material between the to-be-welded surfaces 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, the brazing mold assembled in step S2 is placed in a vacuum hot pressing welding furnace. First, the vacuum hot pressing welding furnace is evacuated to a vacuum degree of 9Pa; then, argon gas is filled into the vacuum hot pressing welding furnace for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, the vacuum hot pressing welding furnace is set to have a heating rate of 9°C / min, and the temperature is kept for 5 minutes for each increase of 50°C. The final brazing temperature is 470°C, and the temperature is kept for 60 minutes. After cooling to room temperature, the brazing of the magnesium alloy material is completed. The low-magnification OM photograph at the weld position is as shown in FIG. Figure 1 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 67.8MPa. Example 3

[0017] A method for preparing a SiC reinforced MgAl rolled composite solder comprises the following steps: S1. Raw material preparation: First, pure Mg ingots and pure Al ingots (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 400°C, with a reduction of 20% per pass, to obtain Mg rolled plates with a thickness of 4.2 mm and Al rolled plates with a thickness of 4.0 mm; finally, raw materials were prepared according to a ratio of 2:1 between the number of Al rolled plates and the number of Mg rolled plates, which were reserved for use in the following step; S2. Prepare a silicon carbide-alcohol solution, wherein the particle size of the silicon carbide particles is 5 μm and the mass fraction of the silicon carbide particles in the alcohol is 9%. Stir evenly and keep it for use in the next step; S3, uniformly spraying and depositing the silicon carbide-alcohol solution prepared in step S2 onto the surfaces of the Mg rolled plate and the Al rolled plate prepared in step S1, and then staggering and stacking the Mg rolled plate and the Al rolled plate in a sandwich structure of Al rolled plate-Mg rolled plate-Al rolled plate to obtain a solder blank; S4, placing the brazing material prepared in step S3 into a heating furnace, setting the heating temperature to 320°C, and heating to the set temperature and keeping the temperature for 10 minutes; S5. Send the solder blank heated in step S4 to a rolling device for multiple rolling processes, with a reduction of 22% in each process and a total reduction of 60%, to obtain a SiC-reinforced MgAl laminated composite solder having a thickness of 488 μm.

[0018] A brazing method for SiC reinforced MgAl rolled composite brazing material comprises the following steps: S1. The size of the magnesium alloy to be brazed in Example 3 is 50 mm in length × 30 mm in width × 5.7 mm in thickness. 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 SiC-reinforced MgAl rolled composite brazing material are rinsed with alcohol and blown dry with cold air for later use; S2, placing the cleaned SiC reinforced MgAl rolled composite brazing material between the to-be-welded surfaces 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, the brazing mold assembled in step S2 is placed in a vacuum hot pressing welding furnace. First, the vacuum hot pressing welding furnace is evacuated to a vacuum degree of 10Pa; then, the vacuum hot pressing welding furnace is filled with argon gas for protection, and the argon gas pressure is not less than the standard atmospheric pressure; finally, the heating rate of the vacuum hot pressing welding furnace is set to 8℃ / min, and the temperature is kept for 5min for each increase of 50℃. The final brazing temperature is 470℃, the insulation time is 60min, and the brazing of the magnesium alloy material is completed. The MgAl alloy joint obtained by brazing is well connected, and there are no obvious defects such as cracks and pores in metallographic observation. The metallographic bonding of the welding interface is tight, and the room temperature shear strength is 64.3MPa.

[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 method for preparing a SiC reinforced MgAl rolled composite brazing material, 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 the 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~400°C respectively, with a reduction of 15%~20% per pass, to obtain Mg rolled plates and Al rolled plates with a thickness of 0.5~1 mm; finally, prepare the raw materials according to the ratio of Al rolled plates to Mg rolled plates of 2:1, and reserve them for use in the next step; S2. Prepare a silicon carbide-alcohol solution, wherein the particle size of the silicon carbide particles is 1-10 μm, and the mass fraction of the silicon carbide particles in the alcohol is 0.1%-10%. Stir evenly and keep it for use in the next step; S3, uniformly spraying and depositing the silicon carbide-alcohol solution prepared in step S2 onto the surfaces of the Mg rolled plate and the Al rolled plate prepared in step S1, and then staggering and stacking 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; S4, placing the brazing material prepared in step S3 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; S5. Send the solder blank heated in step S4 to a rolling device for multiple rolling processes, with a reduction of 15% to 30% in each process and a total reduction of 50% to 70% to obtain a SiC-reinforced MgAl laminated-rolled composite solder, wherein the thickness of the SiC-reinforced MgAl laminated-rolled composite solder does not exceed 500 μm.

2. The method for preparing a SiC reinforced MgAl rolled composite solder according to claim 1, characterized in that: The melting temperature of the prepared SiC reinforced MgAl rolled composite brazing filler metal is 437-455°C, and the brazing temperature is 460-500°C. It is used for brazing magnesium-aluminum alloys with a solidus temperature above 500°C.

3. A brazing method using the SiC reinforced MgAl rolled composite brazing filler metal prepared by the preparation method according to 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 SiC reinforced MgAl rolled composite brazing material with alcohol and blow dry with cold air for later use; S2, placing the cleaned SiC reinforced 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 SiC reinforced 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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