A dissimilar metal friction welding interface regulation layer and an aluminum-steel friction welding method

Abstract

The present invention discloses a control layer for the friction welding interface of dissimilar metals and a friction welding method for aluminum and steel, including micro-textures arranged on the metal surface, with a paste laid on the micro-textures, and the non-metallic substances in the paste are completely volatilized before the metallurgical bonding of dissimilar metals; the steps of the welding method include: preparing micro-textures in a specified area on the surface of a stainless steel plate, mixing Zn-20Al powder and ethanol to stir into a paste, then evenly laying the paste on the micro-texture area on the surface of the base material, and then performing friction stir welding. The welded joints obtained by the solution of the present invention have good toughness (plasticity), high strength, the joint interface achieves atomic-level close bonding, the mechanical properties of the joints are excellent, the joints have no porosity and crack defects, the adverse effects of brittle intermetallic compounds on the mechanical properties are weakened, the wetting and spreading properties and element diffusion ability at the interface are enhanced, and the obtained welded joints not only have good mechanical interlocking characteristics.

Description

Technical Field

[0001] The invention belongs to the technical field of dissimilar metal friction welding, and in particular relates to a dissimilar metal friction welding interface regulating layer and an aluminum-steel friction welding method. Background Art

[0002] Aluminum and steel dissimilar metal composite structures have the advantages of light weight and high strength. They have been widely used in aerospace, shipbuilding, vehicles and other fields, and have great application potential. However, aluminum and steel have different physical and chemical properties, and are prone to generate brittle and hard intermetallic compounds. The mechanical properties of the joints obtained by traditional welding methods are poor, and even continuous welds cannot be formed. Therefore, achieving reliable connection of aluminum and steel dissimilar materials has become a hot spot and difficulty in the field of welding.

[0003] Existing document 202010979074X discloses an aluminum / steel laser welding method under the regulation of surface microtexture. The morphology distribution of intermetallic compounds at the interface is improved by the preparation of microtexture, the thickness of the intermetallic compound layer at the interface is effectively reduced, and the performance of the interface organization is improved; document 202311139202X discloses a method for preparing a metal / CFRTP composite structure, by preparing a specific microtexture on the surface of a metal substrate, completing laser connection under a certain pressure to obtain a firm joint. However, the performance of the joint obtained by welding using the aforementioned welding method still needs to be further optimized. More importantly, the joint obtained by welding using the existing welding method has poor toughness, the wetting and spreading properties and element diffusion capacity at the joint interface are poor, and it is difficult to achieve tight bonding at the atomic level at the joint interface. Summary of the invention

[0004] In view of the technical problems mentioned in the background technology, the purpose of the present invention is to provide a dissimilar metal friction welding interface regulating layer and an aluminum-steel friction welding method.

[0005] The present invention adopts the following technical solution.

[0006] A dissimilar metal friction welding interface regulating layer comprises a micro-texture arranged on a metal surface, a paste is laid on the micro-texture, and non-metallic substances in the paste are completely volatilized before the dissimilar metals are metallurgically bonded.

[0007] Preferably, the dissimilar metals are steel and aluminum, and the paste is a mixture of Zn-20Al powder and ethanol.

[0008] A method for aluminum-steel friction welding based on composite regulation of microtexture and intermediate layer, comprising:

[0009] Step 1, grinding the aluminum alloy base material and the stainless steel base material to remove the oxide film on the surface of the base material, and then cleaning and drying;

[0010] Step 2, prepare micro-textures in the designated area on the surface of the stainless-steel plate. After the micro-textures are prepared, ultrasonically clean them in absolute ethanol for 10 - 15 minutes;

[0011] Step 3, mix Zn-20Al powder with ethanol and stir to form a paste. Then evenly lay the paste on the micro-textured area on the surface of the base material. Then place the base materials to be welded in a lap joint on the welding machine workbench. The lap joint method is steel on top and aluminum at the bottom, and use a fixture to position and clamp them;

[0012] Step 4, perform friction welding using a friction stir welding machine. The stirring head of the friction stir welding machine is a non-pin stirring head. After welding, an aluminum-steel friction welded joint is obtained.

[0013] Further, in Step 3, the mass ratio of Zn-20Al powder to ethanol is 1:1.5.

[0014] Preferably, the laying thickness of the paste is 10 - 50 μm.

[0015] Further, during the friction welding process, press the stirring head on the area to be welded at a rotational speed of 1500 - 3000 r / min, and control the depth of the stirring head pressing into the upper surface of the stainless steel to be 0.2 mm, the downward pressing speed to be 3 mm / min, and the holding pressure time to be controlled at 60 s.

[0016] Preferably, use an ultrafast laser system to process the micro-textures. The processing parameters of the ultrafast laser system are: the pulse width is 20 ns, the laser wavelength is 300 nm, the pulse repetition frequency is 20 kHz, the laser power is 10 W, the pulse energy is 0.5 mJ, the laser scanning rate is 20 - 80 mm / s, and the laser beam scanning area is 20 mm x 20 mm; the groove width of the processed micro-textures is 50 μm and the depth is 200 μm.

[0017] Further, the length direction of the grooves of the micro-textures is consistent with the width direction of the base materials to be welded.

[0018] Further, during the friction welding process, the pressing of the stirring head on the area to be welded is carried out in stages. First, control the stirring head to press on the top surface of the stainless-steel base material at a rotational speed of 1500 - 1800 r / min and maintain it for 10 - 15 seconds. During this process, the temperature of the base material is higher than 80 °C but does not exceed 300 °C. Then control the stirring head to run at a rotational speed of 2000 - 3000 r / min and gradually press down.

[0019] Preferably, the stainless-steel base material is a 304 stainless-steel plate, and the aluminum-alloy base material is a T6-state 6061 aluminum alloy.

[0020] Beneficial effects: The welded joint obtained by the solution of the present invention has good toughness (plasticity), high strength, and the joint interface achieves atomic-level close bonding (metallurgical bonding). The mechanical properties of the joint are excellent, and there are no porosity and crack defects in the joint. During the welding process, the Zn-20Al powder, as a low-melting-point material, forms a soft and tough dispersion including FeZn10 and Al-rich amorphous phase in the hard and brittle intermetallic compound layer of the joint. The formed dispersion improves the toughness of the joint during the welding of dissimilar aluminum / steel materials, weakens the adverse effects of brittle intermetallic compounds on mechanical properties, and during the welding process, the aluminum plate undergoes plastic deformation under the combined action of frictional heat generation and pressure, forming a mechanical interlock with the micro-texture on the surface of the steel, significantly enhancing the wetting and spreading performance and element diffusion ability at the interface. The obtained welded joint not only has good mechanical interlock characteristics, but also performs intermediate layer regulation compared with traditional welding methods, improving the plasticity of the intermetallic compounds at the joint interface and enhancing the mechanical properties of the friction welded aluminum-steel joint. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the micro-texture structure obtained in Example 1;

[0022] Figure 2 It is a schematic diagram of the friction welding process of aluminum-steel in Example 1;

[0023] Figure 3 It is a schematic diagram of the interface of the welded joint obtained in Example 1;

[0024] In the figure: 1 represents a 304 stainless steel plate, 2 represents a 6061 aluminum plate, 3 represents a ZnAl20 intermediate layer (interface layer), 4 represents a stirring head, and 5 represents the groove of the micro-texture. Detailed Embodiments

[0025] The following combines the drawings to clearly and completely describe the technical solutions in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. Example 1

[0026] A friction welding method for aluminum-steel based on the composite regulation of micro-texture and intermediate layer is used to weld and connect a T6-state 6061 aluminum alloy plate (referred to as 6061 aluminum plate) and a 304 stainless steel plate. Combining Figures 1 to 3 as shown, the steps include:

[0027] Step 1: Grind the aluminum alloy base material and the stainless steel base material to remove the oxide film on the surface of the base material, and then clean and dry them. Specifically: Use 400# and 800# SiC metallographic sandpaper to grind the aluminum alloy base material (6061 aluminum plate) and the 304 stainless steel base material (304 stainless steel plate), and use anhydrous ethanol reagent to grind and clean the 6061 aluminum plate and the 304 stainless steel plate to remove the surface oil stain and surface oxide film of the plates.

[0028] Step 2: Prepare micro-textures in the designated area on the surface of the stainless steel plate. After the micro-textures are prepared, ultrasonically clean them in anhydrous ethanol for 10 - 15 minutes. Specifically: Place the cleaned 304 stainless steel plate on the sample stage of the ultrafast laser processing system. Select the texture form as strip-shaped. Use a nanosecond laser to prepare laser surface micro-textures with a groove width of 50 μm and a depth of 200 μm in the designated area on the surface of the 304 stainless steel plate (as Figure 1 shown). The length direction of the grooves of the micro-textures is consistent with the width direction of the 304 stainless steel plate. The length of the grooves of the micro-textures is equal to the width of the 304 stainless steel plate. The spacing between each micro-texture is 500 μm. After preparation, ultrasonically clean them in anhydrous ethanol for 15 minutes.

[0029] Step 3: Mix Zn-20Al powder and ethanol and stir them into a paste (the mass ratio of Zn-20Al powder to ethanol is 1:1.5). Then evenly lay the paste on the micro-texture area on the surface of the base material (304 stainless steel plate). The top surface of the laid paste is about 30 μm higher than the surface of the 304 stainless steel. Then lap the 304 stainless steel on the 6061 aluminum plate on the welding machine workbench. The lapping method is steel on top of aluminum, and the lapping length is 20 mm. And use a fixture to position and clamp.

[0030] Step 4: Carry out friction welding using a friction stir welding machine. The stirring head of the friction stir welding machine is a non-pin stirring head. After welding, an aluminum-steel friction welded joint is obtained. Specifically: Install a non-pin stirring head made of W-25Re on the main shaft of the friction stir welding machine. Start the welding machine. Move the stirring head above the welding point.

[0031] Next, the stirring head is controlled to rotate at a speed of 1600 r / min and pressed on the top surface of the stainless steel base material for 12 seconds. During this process, the base material temperature is higher than 80°C but not more than 300°C, and the remaining ethanol in the paste evaporates rapidly along the length of the groove (due to the use of a specific ratio of Zn-20Al powder and ethanol and a specific stirring friction process, the Zn-20Al powder particle morphology in the paste will not be changed after the ethanol in the paste evaporates and before metallurgical bonding). Then the stirring head is controlled to rotate at a speed of 2500 r / min and gradually pressed down (the Zn-20Al powder particle morphology in this process changes under the action of high temperature), and the depth of the stirring head pressed into the upper surface of the stainless steel is controlled to be 0.2 mm, the pressing speed is 3 mm / min, and the holding time after pressing in place is controlled to be 60 s. After the end, an aluminum-steel friction welding joint is obtained, as shown in FIG. Figure 3 shown.

[0032] RT testing was performed on the aluminum-steel friction welding joint in this embodiment, and the results showed that the welding joint had no defects such as pores and cracks; the mechanical properties of the aluminum-steel friction welding joint were tested, and the results showed that the average shear strength was 3250N, which was significantly improved compared with the welding structure without the addition of intermediate layer and micro-texture.

[0033] In this embodiment, by laying a paste of a specific ratio on the micro-texture, and then cooperating with a specific friction welding process, a stable and reliable connection of dissimilar metal materials is achieved, and effective welding of the joint is achieved while ensuring uniform interface chemical diffusion phase and excellent wettability, thereby avoiding the generation of pore defects. In the comparative scheme, if phosphate salt (polymer) is used instead of anhydrous ethanol, a large number of pores will be generated at the joint; if anhydrous ethanol is used too much, a small number of pores will also be generated at the joint; if anhydrous ethanol is used too little, the plastic toughness of the welded joint is poor.

[0034] During the welding process, Zn-20Al powder, as a low melting point material, forms a soft and tough dispersion including FeZn10 and Al-rich amorphous phase in the hard and brittle intermetallic compound layer of the joint (i.e., ZnAl20 intermediate layer, such as Figure 3 As shown in the figure, the dispersion formed improves the toughness of the joint during aluminum / steel dissimilar material welding, weakens the adverse effects of brittle intermetallic compounds on mechanical properties, and during the welding process, the aluminum plate undergoes plastic deformation under the combined action of frictional heat and pressure, forming a mechanical fit with the micro-texture of the steel surface, significantly enhancing the wetting and spreading properties and element diffusion capacity at the interface, and achieving a close bond (metallurgical bonding) at the atomic level at the joint interface. The obtained welded joint not only has good mechanical fit characteristics, but also has an intermediate layer regulated compared to traditional welding methods, thereby improving the plasticity of the intermetallic compounds at the joint interface and improving the mechanical properties of the aluminum-steel friction welding joint.

Claims

1. A dissimilar metal friction welding interface control layer, characterized in that: The invention comprises a micro-texture arranged on a metal surface, a paste is laid on the micro-texture, and non-metallic substances in the paste are completely volatilized before metallurgical bonding of dissimilar metals; the dissimilar metals are 6061 aluminum alloy and 304 stainless steel; the micro-texture is obtained by processing with an ultrafast laser system, and the processing parameters of the ultrafast laser system are: pulse width of 20ns, laser wavelength of 300nm, pulse repetition frequency of 20kHz, laser power of 10W, pulse energy of 0.5mJ, laser scanning rate of 20-80mm / s, and laser beam scanning area of ​​20mmx20mm; the groove width of the processed micro-texture is 50μm and the depth is 200μm; the paste is a mixture of Zn-20Al powder and ethanol, and the mass ratio of Zn-20Al powder to ethanol is 1:1.

5.

2. A method for friction welding of aluminum and steel based on the composite regulation of micro-texture and intermediate layer, characterized in that the steps include: Step 1, grinding the aluminum alloy base material and the stainless steel base material to remove the oxide film on the surface of the base material, and then cleaning and drying; Step 2, preparing micro textures in a designated area on the surface of the stainless steel plate, and ultrasonically cleaning the micro textures in anhydrous ethanol for 10 to 15 minutes after the micro textures are prepared; Step 3, Zn-20Al powder and ethanol are mixed and stirred into a paste, and then the paste is evenly spread on the micro-texture area on the surface of the base material, and then the base materials to be welded are overlapped and placed on the welding machine workbench, the overlap method is steel on top and aluminum on the bottom, and the clamp is used for positioning and clamping; the paste is a mixture of Zn-20Al powder and ethanol, and the mass ratio of Zn-20Al powder to ethanol is 1:1.5; Step 4, friction welding is performed using a friction stir welding machine, wherein the stirring head of the friction stir welding machine is a needle-free stirring head, and after the welding is completed, an aluminum-steel friction welded joint is obtained; The aluminum alloy base material is 6061 aluminum alloy, and the stainless steel base material is 304 stainless steel; The micro-texture is obtained by processing with an ultrafast laser system, wherein the processing parameters of the ultrafast laser system are as follows: pulse width of 20 ns, laser wavelength of 300 nm, pulse repetition frequency of 20 kHz, laser power of 10 W, pulse energy of 0.5 mJ, laser scanning rate of 20-80 mm / s, and laser beam scanning area of ​​20 mm x 20 mm; the groove width of the processed micro-texture is 50 μm and the depth is 200 μm.

3. The aluminum-steel friction welding method according to claim 2, characterized in that: The paste is laid at a thickness of 10-50um.

4. The aluminum-steel friction welding method according to claim 2, characterized in that: During the friction welding process, the stirring head is pressed on the area to be welded at a rotation speed of 1500-3000r / min, and the depth of the stirring head pressed into the upper surface of the stainless steel is controlled to be 0.2mm, the pressing speed is 3mm / min, and the holding time is controlled to be 60s.

5. The aluminum-steel friction welding method according to claim 2, characterized in that: The length direction of the groove of the micro texture is consistent with the width direction of the base material to be welded, and the ethanol in the paste overflows along the length direction of the groove.

6. The aluminum-steel friction welding method according to claim 4, characterized in that: During the friction welding process, the stirring head is pressed on the area to be welded in stages. First, the stirring head is controlled to be pressed on the top surface of the stainless steel base material at a rotation speed of 1500-1800r / min and maintained for 10-15 seconds. During this process, the base material temperature is higher than 80℃ but not more than 300℃. Then the stirring head is controlled to run at a rotation speed of 2000-3000r / min and gradually pressed down.

7. The aluminum-steel friction welding method according to claim 5, characterized in that: The aluminum alloy base material is T6 state 6061 aluminum alloy.

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