Working method of programmable gradient interface of WAAM formed steel / aluminum bimetallic block structure

Abstract

The invention relates to a working method for a programmable gradient interface of a WAAM formed steel / aluminum bimetal block structure, which comprises the following steps: constructing a steel / aluminum block structure model needing to be formed, generating the programmable gradient interface with wedge-shaped characteristics at the interface position, and calculating the material adding sequence of a melting channel of the programmable gradient interface; compiling is carried out on a demonstrator for controlling the motion trail of the robot, the machining trails of the steel matrix and the aluminum matrix of the additive material are designed, and additive material parameters are set; a multi-layer and multi-channel block-shaped steel base body is added; a plurality of wedge-shaped structural steel substrates are added; a layer of zinc is electroplated on the steel base body, meanwhile, the wettability of aluminum molten drops is improved in a heating assisting mode, and the space between the wedge-shaped structure steel base bodies is filled with an additive wedge-shaped structure aluminum base body; multi-layer and multi-channel blocky aluminum alloy is added on an aluminum substrate of the steel / aluminum connection structure, and finally the steel / aluminum bimetal block structure with the gradient interface characteristic is obtained. According to the method, the strength of the steel / aluminum dissimilar metal joint can be improved, and the wettability between steel and aluminum is improved, so that the forming quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of arc additive manufacturing, and in particular to a working method for a WAAM-formed steel / aluminum bimetallic block structure programmable gradient interface. Background Art

[0002] Due to its lightweight characteristics, Fe / Al dissimilar joint structure is widely used in vehicles, ships, aerospace, weapons, national defense and military industries. Steel and aluminum are the two most widely used metal materials in the field of industrial manufacturing. Among them, steel has the advantages of high mechanical strength, high melting point, good machinability and low cost. Aluminum alloy has the advantages of high specific strength and good corrosion resistance. Replacing part of the steel in steel structural parts with aluminum and its alloys, the Fe / Al composite components obtained can reduce the weight of the entire mechanical structure, have the advantages of both aluminum and steel, and have high application value. At present, people have been conducting research on Fe / Al dissimilar metal connection for many years. Based on the metal connection theory, many advanced welding methods such as laser welding, electron beam welding, stir friction welding, brazing, diffusion welding, explosion welding, tungsten inert gas welding, cold metal transition welding, etc. have been proposed. The strength of the Fe / Al joint reported in the research has reached more than 70% of the aluminum side parent material. However, in practical applications, it is often difficult to connect Fe / Al practical application parts with complex structures due to the limitations of corresponding welding methods. The high-strength connection joints obtained in the study are also limited to the connection of Fe / Al thin plates with regular shapes, while blocky complex structure Fe / Al dissimilar metals have a wider range of applications.

[0003] Wire and Arc Additive Manufacturing (WAAM) is an additive manufacturing process that uses an arc as a heat source and welding wire as a raw material. The arc heat melts the welding wire into molten droplets, which are deposited layer by layer on a set path, and the welds are accumulated layer by layer to finally obtain a complete component. Compared with other existing additive manufacturing technologies, the equipment used in WAAM technology has a simple structure, low cost, and high production efficiency. It has advantages in forming large-sized and medium-to-low structural complexity metal components. It has been applied to the manufacture of dissimilar metal structures and has achieved a lot of results.

[0004] In the field of arc additive steel / aluminum dissimilar metal structures, some scholars have studied the evolution behavior of Fe / Al interface microstructure under different WAAM modes, thermal cycle times and interlayer temperatures. The results show that the heat accumulation process plays an important role in the evolution of the Fe / Al interface. A study adopted a new welding process, bypass-current MIG welding (BC-MIG), and obtained a T-shaped dissimilar metal structure with excellent performance using galvanized Q235 as the substrate and 4043 aluminum alloy as the additive material. The researchers found that the deposited layer obtained in the experiment was well formed, the organization was uniform and complete, and the tensile results showed that the profile could withstand large shear stress. A study used WAAM to add a nickel (Ni) interlayer between Fe and Al to obtain a multilayer single-pass thin-walled part with better performance, because the addition of Ni element inhibited the formation of Fe-Al intermetallic compounds and formed Fe-Ni and Al-Ni intermetallic compounds with better performance than Fe-Al intermetallic compounds, which was considered to improve the structural integrity. Some studies have successfully used Cu intermediate layers to obtain multi-layer single-pass thin-walled parts with good performance by depositing Fe-Al transition walls based on arc directional energy deposition process with metal inert gas, because the addition of Cu element inhibits the formation of Fe-Al intermetallic compounds. However, the existing arc additive manufacturing for steel / aluminum dissimilar metal structures is mostly limited to the manufacture of multi-layer single-pass thin-walled parts, and the manufacture of block steel / aluminum dissimilar metal structures by multi-layer and multi-pass is not reported. First, during the multi-layer and multi-pass additive process, aluminum droplets are formed on two different materials, steel / aluminum. Due to the difference in physical properties between steel and aluminum, there are large differences in the melting point, density, thermal conductivity, linear expansion coefficient, etc. of Fe and Al. The wettability of aluminum droplets on steel is poor and it is difficult to add materials, resulting in challenges in forming; secondly, brittle intermetallic compounds are easily generated at the interface of steel / aluminum dissimilar metal structures, making it difficult to form reliable connection strength, and when steel / aluminum dissimilar metals are subjected to external loads, the fracture position is along the interface connection. Summary of the invention

[0005] The object of the present invention is to provide a working method for WAAM forming a programmable gradient interface of a steel / aluminum bimetallic block structure, which can improve the strength of the steel / aluminum dissimilar metal junction and improve the wettability between steel / aluminum to improve the forming quality.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a working method of forming a programmable gradient interface of a WAAM steel / aluminum bimetallic block structure, comprising the following steps:

[0007] (1) Construct a model of a steel / aluminum block structure to be formed, generate a programmable gradient interface with a wedge-shaped feature at its interface, and calculate the additive sequence of its melt path;

[0008] (2) Compile on the teach pendant that controls the robot's motion trajectory, design the machining trajectories of the additive steel substrate and the aluminum substrate, and set the additive parameters of the steel substrate and the aluminum substrate;

[0009] (3) Adding multiple layers and multiple passes of blocky steel substrate according to the characteristics of the model;

[0010] (4) Adding multiple wedge-shaped structural steel matrices based on the gradient interface characteristics;

[0011] (5) electroplating a layer of zinc on the steel substrate obtained by additive manufacturing, thereby increasing the wettability between steel and aluminum and ensuring stable forming during additive aluminum melting. At the same time, heating-assisted method is used to increase the wettability of aluminum droplets, and the additive wedge-shaped aluminum substrate is filled between the wedge-shaped steel substrates, thereby obtaining the desired gradient interface structure model at the steel / aluminum joint;

[0012] (6) Adding multiple layers and multiple passes of block aluminum alloy onto the aluminum matrix of the steel / aluminum joint structure ultimately results in a steel / aluminum bimetallic block structure with gradient interface characteristics.

[0013] Furthermore, step (1) specifically includes the following steps:

[0014] 1) Determine the interface parameter characteristics, including the interface width W, and the interface steel / aluminum transition ratio range r1 to r2;

[0015] 2) Determine the number of additive passes n required for the interface based on the interface width characteristics, that is,

[0016] 3) The additive sequence of the steel / aluminum melt channel at the interface position is programmed according to the interface steel / aluminum transition ratio range r1~r2.

[0017] Furthermore, when r1=0%, r2=100%, and n=4, the first layer of the interface is deposited by steel molten tracks, and the number of aluminum molten tracks is increased and the number of steel molten tracks is decreased in sequence according to the wedge-shaped characteristics.

[0018] Furthermore, when r1=50%, r2=100%, and n=4, the first layer of the interface is alternately deposited by 4 steel molten tracks and 4 aluminum molten tracks, and the number of aluminum molten tracks increases and the number of steel molten tracks decreases in sequence according to the wedge-shaped characteristics.

[0019] Compared with the prior art, the present invention has the following beneficial effects: in view of the fact that the existing arc additive manufacturing of steel / aluminum dissimilar metals is mostly limited to the manufacturing of multi-layer single-channel thin-walled parts, and the wettability between steel / aluminum is poor, and the fracture positions of steel / aluminum dissimilar metals when subjected to external loads are all fractured along the interface connection, the present invention provides a WAAM forming steel / aluminum bimetallic block structure programmable gradient interface working method, the method can design different gradient interfaces at the steel / aluminum connection and realize the structure of mechanical interlocking connection at the steel / aluminum interface connection, thereby improving the strength of the steel / aluminum dissimilar metal joint, and improving the wettability and spreadability between steel / aluminum to ensure stable forming, which can provide technical support for directly forming complex Fe / Al dissimilar metal structural parts by additive manufacturing and expanding its application in vehicles, ships, aerospace, national defense and military industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of a method implementation of an embodiment of the present invention;

[0021] Figure 2 is a steel / aluminum gradient interface structure model in one embodiment of the present invention;

[0022] Figure 3 is a steel / aluminum gradient interface structure model in another embodiment of the present invention;

[0023] Figure 4 Schematic diagram of a multi-layer and multi-pass steel matrix for additive manufacturing in Embodiment 1 of the present invention;

[0024] Figure 5 Schematic diagram of the steel matrix of the additive wedge-shaped structure in the first embodiment of the present invention;

[0025] Figure 6 Schematic diagram of an aluminum substrate with an additive wedge-shaped structure in Embodiment 1 of the present invention;

[0026] Figure 7 Schematic diagram of an additive multi-layer multi-channel block aluminum substrate in Example 1 of the present invention;

[0027] Figure 8 is a schematic diagram of an additively-made wedge-shaped structural steel substrate in Embodiment 2 of the present invention;

[0028] Fig. 9 Schematic diagram of an aluminum substrate with an additive wedge-shaped structure in Embodiment 2 of the present invention;

[0029] Fig.10 It is a schematic diagram of the additive multi-layer multi-channel block aluminum substrate in Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0033] like Figure 1 As shown, this embodiment provides a working method for forming a programmable gradient interface of a WAAM steel / aluminum bimetallic block structure, characterized in that it includes the following steps:

[0034] (1) A model of a steel / aluminum bulk structural component to be formed is constructed, a programmable gradient interface with wedge-shaped features is generated at its interface position, and the additive sequence of its melt path is calculated.

[0035] The specific implementation process of step (1) includes:

[0036] 1) Determine the interface parameter characteristics, including the interface width W, and the interface steel / aluminum transition ratio range r1~r2.

[0037] 2) Determine the number of additive passes n required for the interface based on the interface width characteristics, that is,

[0038] 3) The additive sequence of the steel / aluminum melt channel at the interface position is programmed according to the interface steel / aluminum transition ratio range r1~r2.

[0039] like Figure 2 As shown, when r1=0%, r2=100%, and n=4, the first layer of the interface is deposited by steel melt channels, and the number of aluminum melt channels is increased and the number of steel melt channels is decreased in sequence according to the wedge-shaped characteristics.

[0040] like Figure 3 As shown, when r1=50%, r2=100%, and n=4, the first layer of the interface is alternately deposited by 4 steel molten tracks and 4 aluminum molten tracks, and the number of aluminum molten tracks increases and the number of steel molten tracks decreases in sequence according to the wedge-shaped characteristics.

[0041] (2) Compile on the teach pendant that controls the robot's motion trajectory, design the processing trajectories of the additive steel substrate and the aluminum substrate, and set the additive parameters of the steel substrate and the aluminum substrate.

[0042] (3) Add multiple layers and multiple passes of blocky steel substrate according to the characteristics of the model.

[0043] (4) Based on the gradient interface characteristics, multiple wedge-shaped structural steel matrices are added.

[0044] (5) A layer of zinc is electroplated on the steel substrate obtained by additive manufacturing, thereby increasing the wettability between steel and aluminum and ensuring stable forming during the additive aluminum melt. At the same time, a heating-assisted method is used to increase the wettability of the aluminum droplet, and the additive wedge-shaped aluminum substrate is filled between the wedge-shaped steel substrates, thereby obtaining the desired gradient interface structure model at the steel / aluminum joint.

[0045] (6) Adding multiple layers and multiple passes of block aluminum alloy onto the aluminum matrix of the steel / aluminum joint structure ultimately results in a steel / aluminum bimetallic block structure with gradient interface characteristics.

[0046] Embodiment 1

[0047] In this embodiment, the interface width W is 2.4 mm, the interface steel / aluminum transition ratio range r1 is 0%, r2 is 100%, and the number of additive passes n is 2.

[0048] like Figure 4 As shown, a processing trajectory is designed on a steel substrate 2 according to an overlapping deposition strategy and a steel / aluminum double-wire arc additive device 1 is started according to set process parameters including a working current of 140A, an additive speed of 21cm / min, a wire feeding speed of 175cm / min, and a shielding argon gas flow rate of 12L / min to add the first layer of steel substrate. When adding the remaining layers, an alternating additive strategy is used to design a processing trajectory to add the steel substrate, that is, to fill the additive steel melt channel between two adjacent melt channels of the previous layer to obtain the next layer of steel substrate, and finally a multi-layer and multi-channel block steel substrate 3 is obtained.

[0049] like Figure 5 As shown, on the multi-layer and multi-channel block steel substrate 3, the steel / aluminum double-wire arc additive device 1 is started according to the set process parameters including the working current of 140A, the additive speed of 21cm / min, the wire feeding speed of 175cm / min, and the shielding argon gas flow rate of 12L / min. The additive is composed of five tightly connected wedge-shaped structural steel substrates 4. The wedge-shaped structural steel substrate 4 is first obtained by adding two steel melt channels using an overlapping deposition strategy and finally filling a steel melt channel between the two steel melt channels.

[0050] like Figure 6 As shown in the figure, after the steel substrate is obtained, it is polished and ground, and then Zn 2+ The mass concentration is 100g / L, the temperature is 58℃, the pH value is 1.2, and the current density is 70A / dm 2Galvanizing treatment is carried out, and the final zinc coating thickness is 10um to increase the wettability between steel and aluminum. Then, between the two steel substrates 4, according to the set process parameters including working current of 110A, additive speed of 15cm / min, wire feeding speed of 140cm / min, protective argon gas flow rate of 12L / min, and auxiliary heating temperature of 200°C, first fill one layer of aluminum alloy and then fill two overlapping layers of aluminum alloy, thereby obtaining a wedge-shaped structure aluminum substrate 5, and finally obtaining a structural component with mechanical interlocking and gradient interface transition characteristics at the steel / aluminum connection.

[0051] like Figure 7 As shown, on the steel / aluminum structural component showing a gradient interface transition characteristic of mechanical interlocking, the set process parameters include a working current of 110A, an additive speed of 15cm / min, a wire feeding speed of 140cm / min, a protective argon gas flow rate of 12L / min, and an auxiliary heating temperature of 200°C. An overlapping deposition strategy is used to add the first layer of aluminum matrix, and an alternating additive strategy is used to add the remaining layers, thereby obtaining a multi-layer and multi-pass block aluminum alloy 6, and finally obtaining a block steel / aluminum dissimilar metal structural component with mechanical interlocking and gradient interface transition characteristics at the steel / aluminum interface connection.

[0052] Embodiment 2

[0053] In this embodiment, the interface width W is 4.8 mm, the interface steel / aluminum transition ratio range r1 is 0%, r2 is 100%, and the number of additive passes n is 4.

[0054] like Figure 8 As shown, the multi-layer and multi-channel block steel substrate 3 is additively formed by three tightly connected wedge-shaped structural steel substrates 4 according to the process parameters set in Example 1. The wedge-shaped structural steel substrate 4 is first additively formed by using an overlapping deposition strategy to add four steel channels in the first layer, and then the last two or four layers are additively formed by using a filling deposition strategy to add three or four steel channels in sequence.

[0055] like Fig. 9 As shown, after obtaining the gradient connection structural steel matrix, it is galvanized according to the galvanizing parameters of Example 1 to increase the wettability between steel and aluminum, and then under the action of auxiliary heat, first a layer of aluminum alloy is filled between the two wedge-shaped structural steel matrixes 4, and then two or four overlapping layers of aluminum alloy are filled in sequence, and finally a wedge-shaped structural aluminum matrix 5 is obtained, and finally a structural component with mechanical interlocking and gradient interface transition characteristics at the steel / aluminum connection is obtained.

[0056] like Fig.10 As shown, a multi-layer and multi-pass block aluminum substrate 6 is added according to the process parameters of Example 1 on a steel / aluminum structural component with a gradient interface transition characteristic exhibiting mechanical interlocking, and finally a block steel / aluminum dissimilar metal structural component exhibiting mechanical interlocking and gradient interface transition characteristics at the steel / aluminum interface connection is obtained.

[0057] The present invention proposes a working method for WAAM forming a programmable gradient interface of a steel / aluminum bimetallic block structure, which makes it easy to control the steel / aluminum connection interface so as to directly add bimetallic materials with different structural shapes of steel / aluminum connections required in various fields, and makes up for the deficiency that the existing arc additive manufacturing strategy of steel / aluminum bimetallic material structural parts is limited to multi-layer single-channel thin-walled parts. This patent scheme can provide technical support and theoretical guidance for directly forming complex steel / aluminum bimetallic structural parts through additive manufacturing and expanding their application in vehicles, ships, aerospace, national defense and military industries.

[0058] The present invention proposes a wedge-shaped feature design for the interface connection of the WAAM-formed steel / aluminum bimetallic structural parts, so that the steel / aluminum connection interface presents mechanical interlocking and gradient transition characteristics. Compared with the traditional direct planar connection of steel / aluminum dissimilar metals, this connection method can improve the capillary force of the liquid aluminum alloy inside the microstructure, and inhibit the damage to the interface of the steel / aluminum due to the difference in physical properties of the steel / aluminum by regulating the variation range of the gradient composition, which is beneficial to improving the mechanical properties of the steel / aluminum bimetallic structure interface.

[0059] In response to the problems existing in WAAM forming of steel / aluminum, the galvanizing method and heating assistance can improve the poor wettability between steel / aluminum, thereby ensuring stable additive manufacturing between steel / aluminum under low current, and the heating assistance can improve the wetting and spreading of the aluminum droplets, so that the aluminum molten channels are closely bonded, ultimately ensuring the formation of the steel / aluminum gradient transition interface.

[0060] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for forming a programmable gradient interface of a WAAM steel / aluminum bimetallic block structure, characterized in that: The following steps are involved: (1) Construct a model of a steel / aluminum block structure to be formed, generate a programmable gradient interface with a wedge-shaped feature at its interface, and calculate the additive sequence of its melt path; (2) Compile on the teach pendant that controls the robot's motion trajectory, design the machining trajectories of the additive steel substrate and the aluminum substrate, and set the additive parameters of the steel substrate and the aluminum substrate; (3) Adding multiple layers and multiple passes of blocky steel substrate according to the characteristics of the model; (4) Adding multiple wedge-shaped structural steel matrices based on the gradient interface characteristics; (5) electroplating a layer of zinc on the steel substrate obtained by additive manufacturing, thereby increasing the wettability between steel and aluminum and ensuring stable forming during additive aluminum melting. At the same time, heating-assisted method is used to increase the wettability of aluminum droplets, and the additive wedge-shaped aluminum substrate is filled between the wedge-shaped steel substrates, thereby obtaining the desired gradient interface structure model at the steel / aluminum joint; (6) Adding multiple layers and multiple passes of block aluminum alloy onto the aluminum matrix of the steel / aluminum joint structure ultimately results in a steel / aluminum bimetallic block structure with gradient interface characteristics.

2. The working method of a WAAM forming steel / aluminum bimetallic block structure programmable gradient interface according to claim 1, characterized in that: Step (1) specifically includes the following steps: 1) Determine the interface parameter characteristics, including the interface width W, and the interface steel / aluminum transition ratio range r1 to r2; 2) Determine the number of additive passes n required for the interface based on the interface width characteristics, that is, 3) The additive sequence of the steel / aluminum melt channel at the interface position is programmed according to the interface steel / aluminum transition ratio range r1~r2.

3. A method for forming a programmable gradient interface of a WAAM steel / aluminum bimetallic block structure according to claim 2, characterized in that: When r1=0%, r2=100%, and n=4, the first layer of the interface is deposited by steel molten tracks, and the number of aluminum molten tracks increases and the number of steel molten tracks decreases in sequence according to the wedge-shaped characteristics.

4. The working method of a WAAM forming steel / aluminum bimetallic block structure programmable gradient interface according to claim 2, characterized in that: When r1=50%, r2=100%, and n=4, the first layer of the interface is alternately deposited by 4 steel molten tracks and 4 aluminum molten tracks, and the number of aluminum molten tracks increases and the number of steel molten tracks decreases in sequence according to the wedge-shaped characteristics.

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