Preparation method of silicon carbide reinforced magnesium-zinc filler metal and brazing method

Abstract

A preparation method and brazing method of silicon carbide reinforced magnesium-zinc filler metal belong to the technical field of magnesium alloy welding materials, solve the technical problem of insufficient welding strength of magnesium alloy filler metal, and the solution is as follows: clean magnesium foil and zinc foil are stacked in the mode of one zinc foil and one magnesium foil from bottom to top in turn, the outermost layer is zinc foil, and the surface of each layer of magnesium foil or zinc foil is uniformly sprayed with a silicon carbide-alcohol solution, then the solution is heated in a resistance furnace to obtain a silicon carbide reinforced magnesium-zinc filler metal blank, and then the blank is sent into a cold rolling mill for rolling to obtain a silicon carbide reinforced magnesium-zinc filler metal with a thickness of not more than 500 microns, which is used for brazing of magnesium alloy materials, and the final brazing temperature is 380-420 DEG C, and the holding time is 30-120 min. The preparation process is simple, the silicon carbide is uniformly distributed between the layers, there is no obvious agglomeration, the eutectic structure at the joint can be significantly refined, and the shear strength of the welded joint is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium alloy welding materials, and particularly relates to a preparation method of silicon carbide reinforced magnesium-zinc filler metal and a brazing method. BACKGROUND

[0002] Magnesium alloy has the advantages of low density, high specific strength and specific stiffness, good electrical conductivity and thermal conductivity, excellent damping and shock absorption performance, good electromagnetic shielding effect, good mechanical processing performance, easy recycling, etc., and is the lightest metal structural material that can be applied in industry, and has important application value and broad application prospect in the fields of aerospace, national defense and military industry, automobile manufacturing, electronic products, etc. Due to the demand for product lightweight, it is urgent to braze some widely used magnesium alloys, which requires research and development of filler metals required for magnesium alloy brazing.

[0003] At present, the joint performance after brazing with magnesium alloy filler metal is poor, far lower than the performance of magnesium alloy base material (strength greater than 200 MPa). In addition, in the prior art, the addition of rare earth elements in the magnesium alloy filler metal base can improve the strength and heat resistance of the magnesium alloy filler metal. For example, the patent document with the application number 201110205638.5 discloses a Mg-Zn-Al-Er magnesium alloy filler metal added with rare earth element Er, and the welding strength can reach 49.2~58.9 MPa. However, the price of rare earth elements is high, which limits the application of the filler metal. The patent document with the application number 202210278121.7 discloses a silicon carbide particle reinforced magnesium alloy brazing filler metal and its preparation method and application, and for the first time proposes to use silicon carbide as a reinforcing body to improve the brazing strength of magnesium alloy. However, the brazing shear strength of this filler metal is only 30~36 MPa, and the addition of reinforcing particles (silicon carbide, titanium particles, aluminum oxide, boron nitride, etc.) during smelting is prone to agglomeration, resulting in a decrease in brazing strength. Moreover, the particle reinforced magnesium alloy filler metal prepared by smelting is difficult to thin during secondary processing, and it is difficult to realize industrial application. SUMMARY

[0004] The main purpose of the present application is to overcome the shortcomings of the prior art and solve the technical problem of insufficient welding strength of magnesium alloy filler metal. The present application provides a preparation method of silicon carbide reinforced magnesium-zinc filler metal and a brazing method. The melting temperature range of the silicon carbide reinforced magnesium-zinc filler metal is 330℃~380℃, and the welding temperature range is 370℃~420℃, which is suitable for brazing of magnesium-zinc alloy with a solidus temperature above 420℃.

[0005] The design concept of the present application is that the magnesium foil and the zinc foil are staggered and stacked from bottom to top in the mode of one layer of zinc foil and one layer of magnesium foil, and the silicon carbide particles are introduced on the surface of each layer by the spray deposition method, and then the silicon carbide reinforced magnesium-zinc filler metal with a thickness less than 500 microns is prepared by the method of composite roll bonding, the silicon carbide is uniformly distributed between the layers without obvious agglomeration, and the eutectic structure at the solder joint can be significantly refined, the method is simple, and the magnesium alloy filler metal can be industrialized.

[0006] The present application is realized by the following technical solutions:

[0007] A preparation method of a silicon carbide reinforced magnesium-zinc filler metal, comprising the following steps:

[0008] S1, cut the magnesium foil with a thickness of 0.03-0.1 mm into 6-10 pieces, cut the zinc foil with a thickness of 0.03-0.07 mm into 7-11 pieces, and then clean them with ultrasonic waves and dry them with cold air for later use;

[0009] S2, prepare a silicon carbide-alcohol solution, the particle size of the silicon carbide particles is 1-10 microns, and the mass fraction of the silicon carbide particles in the alcohol is 0.1%-10%, and then stir them uniformly for later use;

[0010] S3, take the magnesium foil and the zinc foil prepared in step S1 and stagger and stack them from bottom to top in the mode of one layer of zinc foil and one layer of magnesium foil, the outermost layer is the zinc foil, and the silicon carbide-alcohol solution prepared in step S2 is uniformly sprayed and deposited on the surface of each layer of magnesium foil or zinc foil, and then put them into an electric resistance furnace for heating, the heating temperature is 250-320 DEG C, the holding time is 5-10 min, and the silicon carbide reinforced magnesium-zinc filler metal blank is prepared;

[0011] S3, roll forming: put the silicon carbide reinforced magnesium-zinc filler metal blank prepared in step S2 into a cold rolling mill, the reduction per pass is 15%-30%, and the total reduction is 50%-70%, and the silicon carbide reinforced magnesium-zinc filler metal with a thickness not greater than 500 microns is prepared.

[0012] As a preferred, the number of layers of the magnesium foil is 8-10 layers, the number of layers of the zinc foil is 9-11 layers, the thickness of each layer of magnesium foil is 0.05-0.1 mm, the thickness of each layer of zinc foil is 0.03-0.05 mm, the particle size of the silicon carbide particles is 3-8 microns, and the mass fraction of the silicon carbide particles in the alcohol is 0.1-9%.

[0013] As a preferred, the melting temperature range of the prepared silicon carbide reinforced magnesium-zinc filler metal is 330-380 DEG C, the welding temperature range is 370-420 DEG C, and it is used for the brazing of magnesium-zinc alloy with a solid phase line temperature above 420 DEG C.

[0014] A brazing method of silicon carbide reinforced magnesium-zinc filler metal, comprising the following steps:

[0015] S1, first, the surface of the magnesium alloy to be brazed is cleaned to remove impurities, dirt and oxide film; then the surface to be welded is polished smooth with 80 and 600 mesh metallographic sandpaper; finally, the magnesium alloy to be brazed and the silicon carbide reinforced magnesium-zinc filler metal are washed with alcohol and dried with cold air, ready for use in the next step;

[0016] S2, the cleaned silicon carbide reinforced magnesium-zinc filler metal is placed between the surfaces to be brazed of the magnesium alloy to be brazed, and then placed in a brazing mold; in order to improve the efficiency of eutectic structure diffusion of the silicon carbide reinforced magnesium-zinc filler metal and the precision of the connection, the brazing mold applies a constant vertical pressure of 1~5MPa;

[0017] 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 0~10Pa; 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, a stepwise multi-step heating method is used to promote the generation of eutectic structure, the heating rate of the vacuum hot pressing welding furnace is set to 1℃ / min~10℃ / min, and the temperature is raised by 30~50℃ every time, and the temperature is kept for 5~10min, the final brazing temperature is 370~420℃, the holding time is 30~120min, and the temperature is cooled to room temperature, the magnesium alloy material brazing is completed.

[0018] Preferably, in step S2, the brazing mold applies a constant vertical pressure of 2~3MPa.

[0019] Compared with the prior art, the beneficial effects of the present application are:

[0020] 1, the present application uses spray deposition method to introduce silicon carbide particles on the surface of magnesium foil and zinc foil, the silicon carbide is uniformly distributed between the layers, and there is no obvious agglomeration, which can significantly refine the eutectic structure at the joint; when the filler metal is used to weld magnesium-zinc alloy, no flux is needed, and the shear strength of the welded joint is between 87~100MPa;

[0021] The melting temperature of the magnesium alloy filler metal of the present application is 330~380℃, the brazing temperature is 370~420℃, and the thickness of the filler metal is less than 500μm, without the need for secondary processing and thinning; the filler metal is prepared by the mature rolling method, which is convenient for industrial transformation of enterprises, does not need to buy new equipment, and realizes batch production simply and conveniently. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Low-power OM photo of the silicon carbide reinforced magnesium-zinc filler metal prepared for example 1;

[0023] Figure 2Low-magnification OM photos of magnesium alloy brazing after using the silicon carbide reinforced magnesium-zinc filler metal prepared in Example 1. DETAILED DESCRIPTION

[0024] The application will be further described in detail below in combination with the drawings and examples. Example 1

[0025] A preparation method of a silicon carbide reinforced magnesium-zinc filler metal, comprising the following steps:

[0026] S1, cut magnesium foils with a thickness of 0.1 mm into 10 pieces, cut zinc foils with a thickness of 0.03 mm into 11 pieces, and then ultrasonic clean and dry with cold air for later use; wherein the purity of the magnesium foils and the zinc foils is above 99.9%;

[0027] S2, prepare a silicon carbide-alcohol solution, 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%, and then stir uniformly for later use;

[0028] S3, stack the magnesium foils and the zinc foils prepared in step S1 in an alternating manner from bottom to top with one zinc foil and one magnesium foil, the outermost layer is a zinc foil, and uniformly spray the silicon carbide-alcohol solution prepared in step S2 on the surface of each magnesium foil or zinc foil, and then put into a resistance furnace for heating, the heating temperature is 300℃, and the holding time is 10 min, to obtain a silicon carbide reinforced magnesium-zinc filler metal blank;

[0029] S3, roll forming: send the silicon carbide reinforced magnesium-zinc filler metal blank prepared in step S2 into a cold rolling mill, the reduction per pass is 26%, and the total reduction is 62%, to obtain a silicon carbide reinforced magnesium-zinc filler metal with a thickness of 493 μm, and the microstructure of the filler metal is as shown in Figure 1 The melting temperature range of the prepared silicon carbide reinforced magnesium-zinc filler metal is 330℃~380℃, the welding temperature range is 370~420℃, and the filler metal is used for brazing of magnesium-zinc alloys with a solidification temperature above 420℃.

[0030] A brazing method of a silicon carbide reinforced magnesium-zinc filler metal, comprising the following steps:

[0031] S1, the size of the magnesium alloy to be brazed in this example 1 is 50 mm in length, 30 mm in width and 5.7 mm in thickness, first, clean the welding surface of the magnesium alloy to be brazed to remove impurities, oil stains and oxide films on the surface, then polish the welding surface smooth by using 80 and 600 mesh metallographic sandpaper in sequence, and finally, rinse the magnesium alloy to be brazed and the silicon carbide reinforced magnesium-zinc filler metal with alcohol and dry with cold air for later use;

[0032] S2, place the cleaned silicon carbide reinforced magnesium-zinc filler metal between the surfaces to be welded 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;

[0033] S3, place the brazing mold assembled in step S2 as a whole in a vacuum hot press welding furnace, first, vacuumize the vacuum hot press welding furnace to a vacuum degree of 10 Pa; then, fill argon in the vacuum hot press welding furnace for protection, the argon pressure is not less than the standard atmospheric pressure; finally, set the heating rate of the vacuum hot press welding furnace to 10 ℃ / min, and keep the temperature for 5 min every time when the temperature is increased by 50 ℃, the final brazing temperature is 390 ℃, the holding time is 60 min, and the temperature is cooled to room temperature, the brazing of the magnesium alloy material is completed, the microstructure of the brazing seam is as shown in Figure 2 The brazing obtains a magnesium-zinc alloy joint with good connection, there is no obvious crack and pore defect in the metallographic observation, the welding interface is tightly metallurgically combined, and the room temperature shear strength is 87.3 MPa. Example 2

[0034] A preparation method of a silicon carbide reinforced magnesium-zinc filler metal, comprising the following steps:

[0035] S1, cut a magnesium foil with a thickness of 0.1 mm into 10 pieces, and cut a zinc foil with a thickness of 0.03 mm into 11 pieces, and then clean them by ultrasonic waves and dry them with cold air for later use; wherein the purity of the magnesium foil and the zinc foil is more than 99.9%;

[0036] S2, prepare a silicon carbide-alcohol solution, 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%, and then stir them uniformly for later use;

[0037] S3, take the magnesium foil and the zinc foil prepared in step S1, and stack them from bottom to top in the manner of one zinc foil and one magnesium foil alternately, the outermost layer is a zinc foil, and uniformly spray the silicon carbide-alcohol solution prepared in step S2 on the surface of each magnesium foil or zinc foil, and then place them in an electric resistance furnace for heating, the heating temperature is 310 ℃, and the holding time is 8 min, and then a silicon carbide reinforced magnesium-zinc filler metal blank is prepared;

[0038] S3, rolling forming: send the silicon carbide reinforced magnesium-zinc filler metal blank prepared in step S2 into a cold rolling mill set, the reduction per pass is 30%, and the total reduction is 70%, and then a silicon carbide reinforced magnesium-zinc filler metal with a thickness of 480 μm is prepared.

[0039] A brazing method of a silicon carbide reinforced magnesium-zinc filler metal, comprising the following steps:

[0040] S1, the size of the magnesium alloy to be brazed in this embodiment 2 is length 50mm x width 30mm x thickness 5.7mm, first, the surface of the magnesium alloy to be brazed is cleaned to remove impurities, oil stains and oxide film on the surface; then the surface to be welded is polished with 80 and 600 mesh metallographic sandpaper in turn; finally, the magnesium alloy to be brazed and the silicon carbide reinforced magnesium zinc filler metal are washed with alcohol and dried with cold air, and left for later use;

[0041] S2, the cleaned silicon carbide reinforced magnesium zinc filler metal is placed between the surfaces to be brazed of the magnesium alloy to be brazed, and then placed in the brazing mold, the brazing mold applies a constant vertical pressure of 2MPa;

[0042] S3, the brazing mold assembled in step S2 is placed in the vacuum hot pressing welding furnace as a whole, first, the vacuum hot pressing welding furnace is evacuated to a vacuum degree of 9Pa; then, the vacuum hot pressing welding furnace is filled with argon for protection, and the argon gas pressure is not less than standard atmospheric pressure; finally, the temperature rising rate of the vacuum hot pressing welding furnace is set to 9℃ / min, and the temperature is kept for 5min every 50℃, the final brazing temperature is 390℃, the holding time is 60min, and the cooling to room temperature is completed, the magnesium alloy material brazing is completed, the magnesium zinc alloy joint is connected well, and the room temperature shear strength is 95.6MPa. Embodiment 3

[0043] A preparation method of a silicon carbide reinforced magnesium zinc filler metal, comprising the following steps:

[0044] S1, cut the magnesium foil with a thickness of 0.1mm into 10 pieces, and cut the zinc foil with a thickness of 0.03mm into 11 pieces, then ultrasonic cleaning and drying with cold air, and leave for later use; wherein the purity of magnesium foil and zinc foil is more than 99.9%;

[0045] S2, prepare a silicon carbide-alcohol solution, the particle size of silicon carbide particles is 5μm, the mass fraction of silicon carbide particles in alcohol is 9%, and the solution is stirred uniformly and left for later use;

[0046] S3, take the magnesium foil and zinc foil prepared in step S1 and stack them in the order of one layer of zinc foil and one layer of magnesium foil from bottom to top, the outermost layer is zinc foil, and the silicon carbide-alcohol solution prepared in step S2 is uniformly sprayed on the surface of each layer of magnesium foil or zinc foil, then put it into a resistance furnace for heating, the heating temperature is 300℃, and the holding time is 10min, and the silicon carbide reinforced magnesium zinc filler metal blank is prepared;

[0047] S3, rolling forming: send the silicon carbide reinforced magnesium zinc filler metal blank prepared in step S2 into a cold rolling mill, the reduction per pass is 22%, and the total reduction is 56%, and the silicon carbide reinforced magnesium zinc filler metal with a thickness of 495μm is prepared.

[0048] A brazing method of silicon carbide reinforced magnesium-zinc filler metal, comprising the following steps:

[0049] S1, the size of the magnesium alloy to be brazed in this embodiment 3 is length 50mm x width 30mm x thickness 5.7mm, first, the welding surface of the magnesium alloy to be brazed is cleaned to remove the surface impurities, dirt and oxide film; then the welding surface is polished smooth by using 80 and 600 mesh metallographic sandpaper in turn; finally, the magnesium alloy to be brazed and the silicon carbide reinforced magnesium-zinc filler metal are washed with alcohol and dried with cold air, waiting for use in the next step;

[0050] S2, the cleaned silicon carbide reinforced magnesium-zinc filler metal is placed between the welding surfaces of the magnesium alloy to be brazed, and then placed in the brazing mold, the brazing mold applies a constant vertical pressure of 2MPa;

[0051] S3, the brazing mold assembled in step S2 is placed in the vacuum hot pressing welding furnace as a whole, 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 gas pressure is not less than 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 every 50℃, the final brazing temperature is 390℃, the holding time is 60min, and the cooling to room temperature is completed, the magnesium alloy material brazing is completed, the magnesium-zinc alloy joint is connected well, and the room temperature shear strength is 99.3MPa.

[0052] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any skilled person in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for producing a silicon carbide reinforced magnesium-zinc brazing material, characterized by, The method comprises the following steps: S1, cutting magnesium foil with a thickness of 0.03-0.1 mm into 6-10 pieces and cutting zinc foil with a thickness of 0.03-0.07 mm into 7-11 pieces, and then performing ultrasonic cleaning and blowing with cold air for drying and leaving for later use; S2, preparing a silicon carbide-alcohol solution, 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%, and then stirring uniformly and leaving for later use; S3, taking the magnesium foil and the zinc foil prepared in step S1 and stacking them in an alternating manner from bottom to top with one layer of zinc foil and one layer of magnesium foil, the outermost layer being zinc foil, and uniformly spraying the silicon carbide-alcohol solution prepared in step S2 on the surface of each layer of magnesium foil or zinc foil, and then placing them in a resistance furnace for heating, the heating temperature being 250-320℃, and the holding time being 5-10 min, to obtain a silicon carbide reinforced magnesium-zinc filler metal blank; S4, rolling forming: sending the silicon carbide reinforced magnesium-zinc filler metal blank prepared in step S3 into a cold rolling mill, the reduction per pass being 15%-30%, and the total reduction being 50%-70%, to obtain a silicon carbide reinforced magnesium-zinc filler metal with a thickness of not more than 500 μm.

2. The method of claim 1, wherein the silicon carbide reinforced magnesium-zinc brazing material is prepared by the steps of: mixing a magnesium alloy powder and a zinc alloy powder; adding a silicon carbide powder to the mixture; and sintering the mixture. The number of layers of the magnesium foil in the cross-laminated rolling is 8-10, the number of layers of the zinc foil is 9-11, the thickness of each layer of magnesium foil is 0.05-0.1 mm, the thickness of each layer of zinc foil is 0.03-0.05 mm, the particle size of the silicon carbide particles is 3-8 μm, and the mass fraction of the silicon carbide particles in the alcohol is 0.1-9%.

3. The method of claim 1, wherein the silicon carbide reinforced magnesium-zinc brazing material is prepared by the steps of: mixing a magnesium alloy powder and a zinc alloy powder; adding a silicon carbide powder to the mixture; and sintering the mixture. The melting temperature range of the prepared silicon carbide reinforced magnesium-zinc filler metal is 330-380℃, the welding temperature range is 370-420℃, and the silicon carbide reinforced magnesium-zinc filler metal is used for brazing magnesium-zinc alloys with a solid phase line temperature of above 420℃.

4. A brazing method using the silicon carbide reinforced magnesium-zinc brazing material produced by the production method according to claim 1, characterized by, The method comprises the following steps: S1, first, cleaning the surface of the magnesium alloy to be brazed to remove impurities, oil stains and oxide films, then polishing the surface with 80 and 600 mesh metallographic sandpaper in sequence, and finally washing the magnesium alloy to be brazed and the silicon carbide reinforced magnesium-zinc filler metal with alcohol and drying with cold air, leaving for later use; S2, placing the cleaned silicon carbide reinforced magnesium-zinc filler metal between the surfaces of the magnesium alloy to be brazed, and then placing them in a brazing mold, the brazing mold applying a constant vertical pressure of 1-5 MPa; S3, placing the brazing mold assembled in step S2 in a vacuum hot-pressing welding furnace, first, vacuumizing the vacuum hot-pressing welding furnace to a vacuum degree of 0-10 Pa, then filling the vacuum hot-pressing welding furnace with argon for protection, the argon pressure being not less than the standard atmospheric pressure, and finally setting the heating rate of the vacuum hot-pressing welding furnace to 1-10℃ / min, holding for 5-10 min every time the temperature is raised by 30-50℃, the final brazing temperature being 370-420℃, the holding time being 30-120 min, and cooling to room temperature to complete the brazing of the magnesium alloy material.

5. The brazing method of silicon carbide reinforced magnesium zinc brazing material according to claim 4, characterized by, In step S2, the brazing mold applies a constant vertical pressure of 2-3 MPa.

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