Dissimilar metal friction welding interface regulation and control layer and aluminum steel friction welding method

Abstract

The invention discloses a dissimilar metal friction welding interface regulation and control layer and an aluminum steel friction welding method. The dissimilar metal friction welding interface regulation and control layer comprises a micro-texture arranged on the metal surface, paste is laid at the micro-texture, and non-metal substances in the paste are completely volatilized before dissimilar metal metallurgical bonding; the welding method comprises the steps that a microstructure is prepared in a designated area on the surface of a stainless steel plate, Zn-20Al powder and ethyl alcohol are mixed and stirred into paste, then the paste is evenly laid on the microstructure area on the surface of base metal, and then friction stir welding is conducted. A welding joint obtained through the scheme is good in toughness (plasticity) and high in strength, atomic-level tight combination of a joint interface is achieved, the mechanical property of the joint is excellent, the joint is free of air hole and crack defects, the adverse effect of brittle intermetallic compounds on the mechanical property is weakened, the wetting spreading performance and the element diffusion capacity of the interface are enhanced, and the welding quality is improved. The obtained welding joint has a good mechanical embedding characteristic.

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: 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 is mixed with ethanol to form 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 material to be welded is overlapped and placed on the welding machine workbench, with the overlap method of steel on top and aluminum on the bottom, and clamped by a fixture; Step 4, using a friction stir welding machine to perform friction welding, 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.

[0009] Furthermore, in step 3, the mass ratio of Zn-20Al powder to ethanol is 1:1.5.

[0010] Preferably, the paste is laid to a thickness of 10-50 um.

[0011] Furthermore, during the friction welding process, the stirring head is pressed on the area to be welded at a rotation speed of 1500-3000 r / min, 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 is controlled to be 60 s.

[0012] Preferably, an ultrafast laser system is used to process the microtexture, 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 microtexture is 50μm and the depth is 200μm.

[0013] Furthermore, the length direction of the grooves of the micro texture is consistent with the width direction of the base material to be welded.

[0014] Furthermore, 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 1500-1800 r / min and maintained for 10-15 seconds. During this process, the temperature of the base material is higher than 80°C but not more than 300°C. Then, the stirring head is controlled to run at a rotation speed of 2000-3000 r / min and gradually pressed down.

[0015] 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.

[0016] Beneficial effects: The welded joint obtained by the scheme of the present invention has good toughness (plasticity), high strength, and the joint interface achieves close bonding (metallurgical bonding) at the atomic level. The joint has excellent mechanical properties and is free of pores and crack defects. 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. The formed dispersion improves the toughness of the joint during the welding of aluminum / steel dissimilar materials, and reduces the adverse effects of brittle intermetallic compounds on mechanical properties. In addition, during the welding process, the aluminum plate undergoes plastic deformation under the combined action of frictional heat generation and pressure, and forms a mechanical fit with the micro-texture of the steel surface, which significantly enhances the wetting and spreading properties and element diffusion capacity at the interface. The obtained welded joint not only has good mechanical fit characteristics, but also performs intermediate layer regulation compared to traditional welding methods, improves the plasticity of the intermetallic compound at the joint interface, and improves the mechanical properties of the aluminum-steel friction welding joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the micro-texture structure obtained in Example 1; Figure 2 This is a schematic diagram of the aluminum-steel friction welding process in Example 1; Figure 3 is a schematic diagram of the welding joint interface obtained in Example 1; 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 a micro-textured groove. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0019] A friction welding method for aluminum steel based on micro-texture and intermediate layer composite control is used to weld T6 state 6061 aluminum alloy plate (referred to as 6061 aluminum plate) and 304 stainless steel plate. Figures 1 to 3 As shown, the steps include: 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 it; 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 and surface oxide film of the plate; Step 2, preparing micro-textures in designated areas on the surface of the stainless steel plate, and ultrasonically cleaning the plate in anhydrous ethanol for 10 to 15 minutes after the micro-textures are prepared; specifically, the cleaned 304 stainless steel plate is placed on the sample stage of the ultrafast laser processing system, the texture form is selected as stripes, and a nanosecond laser is used to prepare a laser surface micro-texture with a groove width of 50 μm and a depth of 200 μm in a designated area on the surface of the 304 stainless steel plate (such as Figure 1 As shown), the length direction of the groove of the micro texture is consistent with the width direction of the 304 stainless steel plate, the length of the groove of the micro texture is equal to the width of the 304 stainless steel plate, and the spacing between each micro texture is 500μm. After preparation, it is ultrasonically cleaned in anhydrous ethanol for 15 minutes; Step 3, Zn-20Al powder and ethanol are mixed and stirred into a paste (the mass ratio of Zn-20Al powder to ethanol is 1:1.5), and then the paste is evenly spread on the micro-texture area on the surface of the base material (304 stainless steel plate), and the top surface of the spread paste is about 30 um higher than the surface of the 304 stainless steel. Then, the 304 stainless steel is overlapped on the 6061 aluminum plate on the welding machine workbench, and the overlap method is steel on top and aluminum on the bottom, the overlap length is 20 mm, and the fixture is used for positioning and clamping; Step 4, friction welding is performed using a friction stir welding machine, the stirring head of the friction stir welding machine is a pinless stirring head, and after the welding is completed, an aluminum-steel friction welded joint is obtained; specifically: a pinless stirring head made of W-25Re is installed on the main shaft of the friction stir welding machine, the welding machine is started, and the stirring head is moved above the welding point, 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 3shown.

[0020] 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.

[0021] 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.

[0022] 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 the 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.

2. The dissimilar metal friction welding interface regulating layer according to claim 1, characterized in that: The dissimilar metals are steel and aluminum, and the paste is a mixture of Zn-20Al powder and ethanol.

3. A friction welding method for aluminum steel based on micro-texture and intermediate layer composite control, 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 is mixed with ethanol to form 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 material to be welded is overlapped and placed on the welding machine workbench, with the overlap method of steel on top and aluminum on the bottom, and clamped by a fixture; Step 4, using a friction stir welding machine to perform friction welding, 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.

4. The aluminum-steel friction welding method according to claim 3, characterized in that: In step 3, the mass ratio of Zn-20Al powder to ethanol is 1:1.

5.

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

6. The aluminum-steel friction welding method according to claim 3, 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.

7. The aluminum-steel friction welding method according to claim 3, characterized in that: An ultrafast laser system is used to process the microtexture. 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 microtexture is 50μm and the depth is 200μm.

8. The aluminum-steel friction welding method according to claim 3, 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.

9. The aluminum-steel friction welding method according to claim 6, 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.

10. The aluminum-steel friction welding method according to claim 9, characterized in that: The stainless steel base material is 304 stainless steel plate, and the aluminum alloy base material is T6 state 6061 aluminum alloy.

Images