Method for preparing si c reinforced magnesium aluminum clad composite filler material and brazing method

Abstract

The application discloses a preparation method and a brazing method of SiC reinforced MgAl laminated composite filler, belongs to the technical field of magnesium alloy welding materials, and solves the technical problem of insufficient welding strength of magnesium alloy filler prepared by a melting method.The solution is that the length, width and thickness of Mg rolling plates and Al rolling plates are the same, a silicon carbide-alcohol solution is uniformly sprayed and deposited on the surfaces of one Mg rolling plate and two Al rolling plates, the sandwich structure of the Al rolling plate-Mg rolling plate-Al rolling plate is staggered and laminated, and hot rolling is adopted to prepare the SiC reinforced MgAl laminated composite filler with a thickness of not more than 500 microns, a melting temperature of 437-455 DEG C and a brazing temperature of 460-500 DEG C.The preparation process is simple, the silicon carbide is uniformly distributed between the layers and has no obvious agglomeration, the eutectic structure at the brazing seam can be obviously refined, and the shear strength of the welded joint is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium alloy welding materials, and particularly 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 burden on the earth's resources and environment is increasing. The sustainable utilization of natural resources and the environment has become a key issue in today's human society. Lightweighting and green economy are the basic principles and requirements for achieving energy conservation, emission reduction, and improving resource utilization. Magnesium alloys are currently the lightest metal materials in structural metals. They play a significant role in achieving lightweighting, reducing energy consumption, and reducing environmental pollution. The application prospects of magnesium alloys are becoming increasingly broad, and therefore, magnesium alloy connections are also receiving increasing attention.

[0003] Among the many connection methods, brazing is an important way to achieve the connection of magnesium alloy components. Traditional magnesium alloy brazing filler metals are obtained by melting the alloys together. During brazing, it is often difficult for the brazing filler metals to form an effective connection with the magnesium alloy, and the joint strength is very unsatisfactory. 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 a brazing flux will also cause poor brazing formability, and the brazing filler metals obtained by melting the alloy and introducing the reinforcement at the same time still cannot significantly improve the strength of the brazed joint. In addition, the main component of the molten alloy is a eutectic alloy, and the eutectic structure of the magnesium alloy is very brittle, making it difficult to perform secondary processing and difficult to prepare the brazing filler metal in batches. Therefore, the development of a magnesium alloy brazing filler metal that can be efficiently connected to 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 brazing filler metals prepared by smelting method. The present invention provides a preparation method and brazing method of SiC reinforced MgAl rolled composite brazing filler metal.

[0005] The design concept of the present invention is to introduce SiC between the Mg rolled plate and the Al rolled plate pThe reinforcing particles are then directly prepared by the method of composite rolling of Mg rolled plates and Al rolled plates to produce SiC reinforced MgAl rolled composite brazing filler metal with a thickness of less than 500μm. The advantage of this method is that it can conveniently and efficiently produce composite brazing filler metals with a large area and a thickness of less than 500μm in batches. There is no need to reprocess 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 achieved through the following technical solutions: A method for preparing SiC reinforced MgAl rolled composite solder comprises the following steps:

[0007] S1. Raw material preparation: First, pure Mg ingots and pure Al ingots were cut to obtain cast plates with dimensions of 70 mm in length, 30 mm in width, and 1.5 mm in height. Then, the Mg cast plates and Al cast plates were rolled at 350°C to 400°C, with a reduction of 15% to 20% per pass, respectively, to obtain Mg rolled plates and Al rolled plates with thicknesses of 0.4 to 0.6 mm. Finally, raw materials were prepared with 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.

[0008] 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 well and set aside for use in the next step.

[0009] 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 alternately 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 prepare a solder blank;

[0010] S4. Place the solder blank prepared in step S3 into a heating furnace, set the heating temperature to 280-400°C, and keep it warm for 2-10 minutes after reaching the set temperature;

[0011] S5. The solder blank heated in step S4 is fed into a rolling device for multiple rolling passes, with a reduction of 15% to 30% in each pass and a total reduction of 50% to 70%, to obtain a SiC reinforced MgAl laminated composite solder, wherein the thickness of the SiC reinforced MgAl laminated composite solder does not exceed 500 μm.

[0012] 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.

[0013] A brazing method for SiC-reinforced MgAl rolled composite brazing filler metal comprises the following steps:

[0014] 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 polish 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, leaving them for later use;

[0015] 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 form the eutectic structure and the connection accuracy, the brazing mold applies a constant vertical pressure of 0.5-5 MPa.

[0016] 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 0-10 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 heating rate of the vacuum hot pressing welding furnace to 1°C / min-10°C / min, and keep the temperature for 5-10 minutes every time the temperature rises by 30-50°C. The final brazing temperature is 460-500°C, and the holding time is 30-120 minutes. Cool to room temperature to complete the brazing of the magnesium alloy material.

[0017] Preferably, in step S2, the constant vertical pressure applied by the brazing mold is 2-3 MPa.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) The preparation of SiC reinforced MgAl rolled composite solder by the present invention is 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;

[0020] 2) The SiC-reinforced MgAl rolled composite brazing filler metal prepared by the present invention has a melting temperature of 437-455°C and a brazing temperature of 460-500°C. It can be used for brazing magnesium-aluminum alloys with a solidus temperature above 500°C. The brazing filler metal thickness is less than 500 μm, and no secondary processing thinning is required, thereby enabling mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1This 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

[0022] The present invention will be described in further detail below with reference to the accompanying drawings and examples. Example 1

[0023] A method for preparing a SiC reinforced MgAl rolled composite solder comprises the following steps:

[0024] 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, and 1.5 mm in height. Then, the Mg cast plates and Al cast plates were 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 were prepared with 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.

[0025] 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 0.1%. Stir well and set aside for use in the next step.

[0026] 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 alternately 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 prepare a solder blank;

[0027] S4. Place the solder blank prepared in step S3 into a heating furnace, set the heating temperature to 300°C, and heat it to the set temperature and keep it warm for 10 minutes;

[0028] S5. The solder blank heated in step S4 is fed into a rolling machine for multiple rolling passes, with a reduction of 26% in each pass 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.

[0029] A brazing method for SiC-reinforced MgAl rolled composite brazing filler metal comprises the following steps:

[0030] S1. The dimensions of the magnesium alloy to be brazed in Example 1 are 50 mm in length, 30 mm in width, and 5.7 mm in thickness. First, the surface to be brazed of the magnesium alloy is cleaned to remove impurities, oil stains, and oxide films on the surface. Then, the surface to be brazed is polished smooth using 80-grit and 600-grit metallographic sandpapers, respectively. Finally, the magnesium alloy to be brazed and the SiC-reinforced MgAl rolled composite brazing filler metal are rinsed with alcohol and dried with cold air for later use.

[0031] 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. The brazing mold applies a constant vertical pressure of 2 MPa.

[0032] 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 for protection, and the argon pressure is not less than standard atmospheric pressure; finally, the heating rate of the vacuum hot pressing welding furnace is set to 10 ° C / min, and the temperature is kept at 50 ° C for 5 minutes for each increase. The final brazing temperature is 470 ° C, the holding time is 60 minutes, and it is cooled to room temperature to complete the brazing of the magnesium alloy material. The MgAl alloy joint obtained by brazing is well connected, and there are no obvious defects such as cracks and pores in the metallographic observation. The metallographic observation shows that the welding interface is metallurgically bonded and has a close shear strength of 65.7 MPa at room temperature. Example 2

[0033] A method for preparing a SiC reinforced MgAl rolled composite solder comprises the following steps:

[0034] 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, and 1.5 mm in height. Then, the Mg cast plates and Al cast plates were 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 were prepared with 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.

[0035] 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 3%. Stir well and set aside for use in the next step.

[0036] 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 alternately 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 prepare a solder blank;

[0037] S4. Place the brazing material prepared in step S3 into a heating furnace, set the heating temperature to 310°C, and heat it to the set temperature and keep it warm for 8 minutes;

[0038] S5. The solder blank heated in step S4 is fed into a rolling device for multiple rolling passes, with a reduction of 30% in each pass and a total reduction of 70%, to obtain a SiC-reinforced MgAl laminated composite solder having a thickness of 462 μm.

[0039] A brazing method for SiC-reinforced MgAl rolled composite brazing filler metal comprises the following steps:

[0040] S1. The dimensions of the magnesium alloy to be brazed in Example 2 are 50 mm in length, 30 mm in width, and 5.7 mm in thickness. First, the surface to be brazed of the magnesium alloy is cleaned to remove impurities, oil stains, and oxide films on the surface. Then, the surface to be brazed is polished smooth using 80-grit and 600-grit metallographic sandpapers, respectively. Finally, the magnesium alloy to be brazed and the SiC-reinforced MgAl rolled composite brazing filler metal are rinsed with alcohol and dried with cold air for subsequent use.

[0041] 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. The brazing mold applies a constant vertical pressure of 2 MPa.

[0042] S3. Place the brazing mold assembled in step S2 in a vacuum hot pressing welding furnace. First, evacuate the vacuum hot pressing welding furnace to a vacuum degree of 9 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 heating rate of the vacuum hot pressing welding furnace to 9°C / min, and keep the temperature for 5 minutes every time the temperature rises by 50°C. The final brazing temperature is 470°C, the holding time is 60 minutes, and the temperature is cooled to room temperature to complete the brazing of the magnesium alloy material. The low-magnification OM photograph of the weld position is as follows: Figure 1 The MgAl alloy joints obtained by brazing are well connected, with no obvious defects such as cracks and pores in metallographic observation. The metallurgical bonding of the welding interface is tight, and the room temperature shear strength is 67.8 MPa. Example 3

[0043] A method for preparing a SiC reinforced MgAl rolled composite solder comprises the following steps:

[0044] 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, and 1.5 mm in height. Then, the Mg cast plates and Al cast plates 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 with 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.

[0045] 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 well and set aside for use in the next step.

[0046] 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 alternately 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 prepare a solder blank;

[0047] S4. Place the solder blank prepared in step S3 into a heating furnace, set the heating temperature to 320°C, and heat it to the set temperature and keep it warm for 10 minutes;

[0048] S5. The solder blank heated in step S4 is fed into a rolling device for multiple rolling passes, with a reduction of 22% in each pass and a total reduction of 60%, to obtain a SiC-reinforced MgAl laminated solder having a thickness of 488 μm.

[0049] A brazing method for SiC-reinforced MgAl rolled composite brazing filler metal comprises the following steps:

[0050] S1. The dimensions of the magnesium alloy to be brazed in Example 3 are 50 mm in length, 30 mm in width, and 5.7 mm in thickness. First, the surface to be brazed of the magnesium alloy is cleaned to remove impurities, oil stains, and oxide films on the surface. Then, the surface to be brazed is polished smooth using 80-grit and 600-grit metallographic sandpapers, respectively. Finally, the magnesium alloy to be brazed and the SiC-reinforced MgAl rolled composite brazing filler metal are rinsed with alcohol and dried with cold air for later use.

[0051] 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. The brazing mold applies a constant vertical pressure of 2 MPa.

[0052] 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 for protection, and the argon pressure is not less than standard atmospheric pressure; finally, the heating rate of the vacuum hot pressing welding furnace is set to 8 ° C / min, and the temperature is kept at 50 ° C for 5 minutes for each increase. The final brazing temperature is 470 ° C, the holding time is 60 minutes, and it is cooled to room temperature to complete the brazing of the magnesium alloy material. The MgAl alloy joint obtained by brazing is well connected, and there are no obvious defects such as cracks and pores in the metallographic observation. The metallographic interface is closely metallurgically bonded, and the room temperature shear strength is 64.3MPa.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing SiC reinforced MgAl rolled composite solder, characterized in that: The following steps are involved: S1. Raw material preparation: First, pure Mg ingots and pure Al ingots were cut to obtain cast plates with dimensions of 70 mm in length, 30 mm in width, and 1.5 mm in height, respectively. Then, the Mg cast plates and Al cast plates were rolled at 350°C to 400°C, with a reduction of 15% to 20% per pass, respectively, to obtain Mg rolled plates and Al rolled plates with thicknesses of 0.4 to 0.52 mm. Finally, raw materials were prepared with 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 1-10 μm and the mass fraction of the silicon carbide particles in the alcohol is 0.1%-10%. Stir well and set aside 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 alternately 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 prepare a solder blank; S4. Place the solder blank prepared in step S3 into a heating furnace, set the heating temperature to 280-400°C, and keep it warm for 2-10 minutes after reaching the set temperature; S5. The solder blank heated in step S4 is fed into a rolling device for multiple rolling passes, with a reduction of 15% to 30% in each pass and a total reduction of 50% to 70%, to obtain a SiC reinforced MgAl laminated composite solder, wherein the thickness of the SiC reinforced MgAl laminated 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 polish 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, leaving them 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. 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 0-10 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 heating rate of the vacuum hot pressing welding furnace to 1°C / min-10°C / min, and keep the temperature for 5-10 minutes every time the temperature rises by 30-50°C. The final brazing temperature is 460-500°C, and the holding time is 30-120 minutes. Cool to room temperature to complete the brazing of the magnesium alloy material.

4. The brazing method of a SiC reinforced MgAl rolled composite brazing filler metal 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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