An underwater local dry layered composite material arc additive manufacturing method

Abstract

This invention provides an underwater local dry-process layered composite material arc additive manufacturing method. Through additive cross-section design and welding process design of additive strips and wires, the molten metal only needs to fuse the additive strips to the matrix during the arc additive manufacturing process, which greatly reduces the amount of molten metal deposited, improves additive efficiency, effectively reduces the hydrogen embrittlement sensitivity of the additive structure, and the additive structure exhibits a layered distribution structure, that is, an alternating structure of arc additive deposition layer and additive strip solid phase layer. This structure can significantly improve the comprehensive performance of the additive body.

Description

Technical Field

[0001] This invention belongs to the field of laser welding, and particularly relates to an arc additive manufacturing method for underwater local dry layered composite materials. Background Technology

[0002] Underwater welding and additive manufacturing technologies are mainly used in the assembly and maintenance of marine engineering and large underwater facilities. Currently, underwater welding and additive manufacturing technologies are mainly divided into wet welding, dry welding, and partially dry welding. Partially dry welding combines the advantages of both wet and dry methods and is a relatively advanced welding method with promising application prospects. Partially dry welding involves installing a sealed drainage cover on the weld or additive manufacturing area to maintain a relatively dry state in the localized area. This process offers better weld quality and safety.

[0003] Chinese patent application CN 113618195 B discloses an underwater all-position local dry pulsed MIG welding method. This system features localized strong drainage, providing a dry space for underwater welding with a stable airflow field, and exhibits wide process adaptability. However, its drawback lies in the complex equipment structure and poor process adaptability.

[0004] Chinese patent application CN 116532796 A discloses an underwater local dry laser wire-filling welding system and method. After underwater local dry welding is completed, a laser beam is used to remelt the weld, improving the surface microstructure and optimizing the weld formation performance. Its drawback is that the rapid heating and cooling characteristics of the laser during weld treatment can easily lead to a high-hardness hardened structure, increasing the risk of weld cracking.

[0005] Chinese patent application CN 104942487A discloses an underwater local dry welding apparatus and method for titanium alloys and other materials. It uses a microwave radiator to emit microwaves to vibrate and heat residual water on a titanium alloy plate, raising the water temperature to vaporization, thus achieving a water-free surface for the weldment. However, a drawback is that water vapor still exists in the welding environment, and during the welding process, hydrogen atoms can dissolve into the solidified metal of the weld, increasing the risk of hydrogen-induced cracking.

[0006] However, the aforementioned patented devices have complex structures and poor process adaptability. Furthermore, the welding or additive manufacturing process requires melting a large amount of wire to complete the welding connections and additive repairs. However, during underwater welding and additive manufacturing, a small amount of water remains on the surface of the weld after drainage, easily leading to porosity defects. The lower underwater temperature causes a rapid cooling effect in the weld or additive zone, easily resulting in a high-hardness hardened structure. In addition, the high humidity of the underwater welding environment means that water vapor is reduced to hydrogen under the high temperatures of welding and additive manufacturing, and dissolves into the solidified metal. When a large number of hydrogen atoms accumulate inside the metal, hydrogen embrittlement occurs. Summary of the Invention

[0007] The purpose of this invention is to overcome the above-mentioned problems and deficiencies and provide an underwater local dry layered composite material electric arc additive manufacturing method that utilizes electric arc additive manufacturing process for additive repair, which can greatly reduce the deposition amount of additive molten metal, improve additive efficiency, effectively reduce the hydrogen embrittlement sensitivity of additive structures, and improve the mechanical properties of additive bodies.

[0008] The objective of this invention is achieved as follows:

[0009] An underwater localized dry layered composite material arc additive manufacturing method mainly includes:

[0010] (1) Additive section design:

[0011] The cross-sectional shape of the additive flat strip is a symmetrical convex hexagon composed of a rectangle and an isosceles trapezoid. The lower base of the isosceles trapezoid is the same length as the rectangle, and W:h:L = (3.5~6.5):1:(1.5~2.5), where W is the length of the rectangle, h is the width of the rectangle, and L is the upper base of the isosceles trapezoid. The angle α between the hypotenuse and the upper base of the isosceles trapezoid is 30°~55°. The cross-sectional shape of the additive wire is circular with a diameter of 0.8~1.6mm.

[0012] Furthermore, the chemical composition of the additive flat strip, by mass percentage, is as follows: C: 0.05%–0.15%, Si: 0.3%–1.5%, Mn: 0.5%–1.5%, S≤0.02%, P≤0.02%, Cr: 0.2%–0.6%, Ni: 0.5%–4.0%, Mo: 0.3%–1.0%, Ti: 0.02%–0.08%, with the balance being Fe and unavoidable impurities. Preferably, the chemical composition range of the additive flat strip is the same as that of the round filament.

[0013] Furthermore, additive flat strips are extruded materials, and additive wires are cold-drawn wires.

[0014] Furthermore, additive components produced using the underwater local dry layered composite material arc additive manufacturing method have a tensile strength greater than ≥500MPa, an elongation of ≥20%, an impact energy of ≥90J(KV2) at -40℃~0℃, and a residual stress ≤100MPa.

[0015] The rationale for the additive manufacturing process design of this invention's flat strip is as follows:

[0016] The carbon (C) content ensures high strength in the weld metal. A C content above 0.2% severely deteriorates the weldability, while a C content below 0.05% fails to guarantee the required strength. Maintaining a certain C content in the weld metal, along with a specific Cr and Mo ratio, ensures the precipitation of fine M2C-type carbides during subsequent heating, achieving secondary strengthening. Considering all factors, the preferred C content in this invention is 0.05%–0.15%; Mo: 0.3%–1.0%; and Cr: 0.2%–0.6%.

[0017] The combined deoxidation using Si and Mn produces MnO·SiO2, which has a low melting point (approximately 1270℃) and low density. This allows it to agglomerate into large slag masses in the molten pool and float to the surface, achieving a good deoxidation effect. Furthermore, Mn combines with S to form MnS, which reduces the tendency for hot cracking caused by S. To ensure effective deoxidation of the weld metal, the Si content should be no less than 0.3% and the Mn content no less than 0.5%. However, a Si content greater than 1.5% can cause solution hardening and an increase in the number of secondary phases in the weld, leading to weld brittleness. This invention preferably uses a Si content of 0.3%–0.6% and an Mn content of 0.5%–1.5%, resulting in weld metal with good overall performance.

[0018] Ni: Ni content can improve the hardenability of steel, lower the ductile-brittle transition temperature and cleavage fracture tendency of the weld metal, and improve the toughness of the weld metal. Adding Ni can improve the strength of the weld metal without significantly reducing its toughness. A Ni content greater than 0.5% can ensure that the weld metal has good impact toughness at low temperatures. Considering other elements, the preferred Ni content in this invention is 0.5% to 4.0%.

[0019] Ti: Trace amounts of Ti easily form TiO inclusions during additive manufacturing, promoting nucleation within austenite grains and improving the toughness of the weld metal. However, Ti content greater than 0.1% promotes the formation of hard phases such as bainite and MA components in the weld microstructure, deteriorating the toughness of the weld metal. Considering other elements, the preferred Ti content in this invention is 0.02%–0.08%.

[0020] (2) Creating a water-proof environment: A drainage hood is used to isolate the additive manufacturing area from the surrounding water in the work area. After draining the water from the drainage hood, argon gas is introduced into the drainage hood as a protective gas. The introduction of argon gas prevents the additive metal from undergoing an oxidation reaction with oxygen at high temperatures, which would affect the purity and performance of the additive metal. In addition, argon gas can make the electric arc of the additive manufacturing process more stable, ensuring the continuity and uniformity of the additive manufacturing process;

[0021] (3) Place the coiled additive flat strip above the substrate to be welded, and symmetrically distribute two gas metal arc welding torches on both sides of the substrate. The tilt angle β of the gas metal arc welding torch is 20° to 40°, which is the angle between the welding torch and the horizontal line. The welding current of the additive wire is 100 to 300A, the welding voltage of the additive wire is 12 to 30V, the welding torch moving speed is 3 to 10mm / s, the extension length of the additive wire is 15 to 35mm, and the additive shielding gas is 80% to 90% argon + 10% to 20% carbon dioxide.

[0022] During additive welding, the wire of the gas metal arc welding (GMAW) melts. Adjusting the angle of the welding torch can fill the angle between the additive strip and the substrate. The selected process parameters of the additive wire can ensure the penetration depth of the deposited metal and form a good metallurgical bond between the additive strip and the substrate. Preferably, after each additive process ends and before the next, the temperature of the additive strip is controlled at 100-150°C to prepare for the next additive process.

[0023] (4) Keep the angle of the gas metal arc welding torch unchanged, raise the height of one layer of additive flat strip, place the additive flat strip above the first layer of flat strip, and repeat step (3) until all additive welding work is completed.

[0024] The beneficial effects of this invention are as follows:

[0025] 1) In the process of electric arc additive manufacturing, the deposited metal only needs to fuse the additive strip with the substrate, which greatly reduces the amount of deposited additive metal and improves the additive manufacturing efficiency.

[0026] 2) During the arc additive manufacturing process, the two gas metal arc welding torches are symmetrically distributed on both sides of the substrate, and the amount of additive weld metal deposited is less, which greatly reduces the residual stress of the additive structure and makes the residual stress distribution more uniform. The reduction in the amount of weld metal results in fewer hydrogen atoms dissolving into the solidified metal of the weld during the additive manufacturing process, reducing the risk of hydrogen-induced cracking.

[0027] 3) The additive structure exhibits a layered distribution structure, namely, an alternating structure of arc-deposited additive layers and additive flat strip solid phase layers, and an alternating interlocking structure of cast-state deposited layers and extruded solid phase layers. The cast-state deposited layers ensure the forming and connection of the additive body, while the presence of the extruded solid phase layers is beneficial to improving the overall performance of the additive body. This layered distribution structure feature can significantly improve the overall performance of the additive body. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the additive repair process of the present invention.

[0029] Figure 2 This is a schematic diagram showing the tilt angle of the gas metal arc welding torch of the present invention.

[0030] Figure 3 This is a schematic diagram of the additive flat strip structure of the present invention.

[0031] Figure 4 This is a magnified view of the tissue characteristics of layered additive structures.

[0032] Figure 5 This is a microstructure diagram of region a, the interface between the layered additive body deposition layer and the flat strip solid phase layer in Embodiment 1 of the present invention.

[0033] Figure 6 This is a microstructure diagram of region b of the solid phase layer of the layered additive fabric flat strip in Embodiment 1 of the present invention.

[0034] Figure 7 This is a microstructure diagram of region c of the layered additive body deposition layer in Embodiment 1 of the present invention.

[0035] In the figure, 1 is the substrate, 2 is the gas metal arc welding torch, 3 is the additive wire, 4 is the arc additive deposition layer, 5 is the additive flat strip solid phase layer, 6 is the additive flat strip, and 7 is the isolation cover. Detailed Implementation

[0036] The present invention will be further illustrated below through examples.

[0037] Example 1: Additive Manufacturing of AH32 Marine Engineering Steel for Underwater Applications

[0038] Based on the material composition of AH32, the composition (mass fraction %) of the additive flat strip and round wire is designed as follows: C: 0.1, Si: 1.3, Mn: 1.3, S≤0.02, P≤0.02, Cr: 0.2, Ni: 0.8, Mo: 0.4, Ti: 0.03, with the balance being Fe.

[0039] The additive flat strip is processed using a hot extrusion process. The cross-sectional shape of the additive flat strip is a symmetrical convex hexagon composed of a rectangle and an isosceles trapezoid. The lower base of the isosceles trapezoid is the same length as the rectangle, W:h:L = 3.625:1:2, where W is the length of the rectangle, h is the width of the rectangle, and L is the upper base of the isosceles trapezoid, specifically h = 8mm, W = 29mm, and L = 16mm. The angle α between the hypotenuse and the upper base of the isosceles trapezoid is 45°. After the additive flat strip is processed, it is wound onto a reel.

[0040] Circular additive filaments with a diameter of 1.2 mm are processed using a cold drawing process. After processing, the additive filaments are wound onto a reel.

[0041] 2) Use a drainage hood to isolate the additive manufacturing area from the surrounding water. After draining the water from the drainage hood, introduce argon gas into the drainage hood as a protective gas.

[0042] 3) Place the coated additive flat strip above the substrate, adjust the tilt angle β of the gas metal arc welding torch to 25°, and symmetrically distribute the two gas metal arc welding torches on both sides of the substrate. Arc additive process parameters: current is 180A, voltage is 13V, moving speed is 8mm / s, extension length of additive wire is 25mm, and additive shielding gas is 80% argon + 20% carbon dioxide.

[0043] Turn on the arc additive manufacturing device and start the additive manufacturing process. The wire of the gas metal arc welding device melts and the molten metal fills the angle between the additive strip and the substrate, so that the additive strip and the substrate form a good metallurgical bond. After the first layer of additive manufacturing is completed, control the interpass temperature to 120℃.

[0044] 4) Keep the two gas metal arc welding torches at the same angle, raise the height of one layer of additive strip, place the additive strip above the first layer of strip, and carry out the subsequent additive work according to the additive process in 3) until the 50mm, total 5 layers of arc additive work are completed.

[0045] The arc-addition component made of AH32 marine steel and layered composite material has a tensile strength of 515 MPa, an elongation of 24%, an impact energy of 125 J (0℃), and a residual stress of 55 MPa. Figure 5 This is a microstructure diagram of region a, the interface between the layered additive body deposition layer and the flat strip solid phase layer in Embodiment 1 of the present invention. Figure 6 This is a microstructure diagram of region b of the solid phase layer of the layered additive fabric flat strip in Embodiment 1 of the present invention. Figure 7 This is a microstructure diagram of region c of the layered additive body deposition layer in Embodiment 1 of the present invention.

[0046] Example 2: Additive Manufacturing of DH36 Marine Steel for Underwater Applications

[0047] 1) Based on the material composition of the DH36 matrix, design the composition (mass fraction %) of the additive flat strip and round wire: C: 0.08, Si: 1.0, Mn: 1.2, S≤0.02, P≤0.02, Cr: 0.5, Ni: 1.5, Mo: 0.5, Ti: 0.05, with the balance being Fe.

[0048] The additive flat strip is processed using a hot extrusion process. The cross-sectional shape of the additive flat strip is a symmetrical convex hexagon composed of a rectangle and an isosceles trapezoid. The lower base of the isosceles trapezoid is the same length as the rectangle, and W:h:L = 5:1:2.3, where W is the length of the rectangle, h is the width of the rectangle, and L is the upper base of the isosceles trapezoid, specifically h = 3mm, W = 15mm, and L = 7mm. The angle α between the hypotenuse and the upper base of the isosceles trapezoid is 55°. After the additive flat strip is processed, it is wound onto a reel.

[0049] Circular additive filaments with a diameter of 1.2 mm are processed using a cold drawing process. After processing, the additive filaments are wound onto a reel.

[0050] 2) Use a drainage hood to isolate the additive manufacturing area from the surrounding water. After draining the water from the drainage hood, introduce argon gas into the drainage hood as a protective gas.

[0051] 3) Place the coated additive flat strip above the substrate, adjust the tilt angle β of the gas metal arc welding torch to 30°, and symmetrically distribute the two gas metal arc welding torches on both sides of the substrate. Arc additive process parameters: current is 210A, voltage is 16V, moving speed is 5mm / s, extension length of additive wire is 35mm, and additive shielding gas is 80% argon + 20% carbon dioxide.

[0052] Turn on the arc additive manufacturing device and start the additive manufacturing process. The wire of the gas metal arc welding device melts and the molten metal fills the angle between the additive strip and the substrate, so that the additive strip and the substrate form a good metallurgical bond. After the first layer of additive manufacturing is completed, control the interpass temperature to 150℃.

[0053] 4) Keep the two gas metal arc welding torches at the same angle, raise the height of one layer of additive strip, place the additive strip above the first layer of strip, and carry out the subsequent additive work according to the additive process in 3) until all the arc additive work of 60mm and a total of 15 layers is completed.

[0054] The DH36 marine steel arc additive manufacturing component with layered composite material has a tensile strength of 535 MPa, an elongation of 25%, an impact energy of 115 J (-20℃), and a residual stress of 75 MPa.

[0055] Example 3: Additive Manufacturing of EH36 Marine Steel for Underwater Applications

[0056] 2) Based on the material composition of the EH36 matrix, design the composition (mass fraction %) of the additive flat strip and round wire: C: 0.07, Si: 0.8, Mn: 1.1, S≤0.02, P≤0.02, Cr: 0.3, Ni: 3.5, Mo: 0.7, Ti: 0.05, with the balance being Fe.

[0057] The additive flat strip is processed using a hot extrusion process. The cross-sectional shape of the additive flat strip is a symmetrical convex hexagon composed of a rectangle and an isosceles trapezoid. The lower base of the isosceles trapezoid is the same length as the rectangle, W:h:L = 3.6:1:1.8, where W is the length of the rectangle, h is the width of the rectangle, and L is the upper base of the isosceles trapezoid, specifically h = 5mm, W = 18mm, and L = 9mm. The angle α between the hypotenuse and the upper base of the isosceles trapezoid is 45°. After the additive flat strip is processed, it is wound onto a reel.

[0058] Circular additive filaments with a diameter of 1.0 mm are processed using a cold drawing process. After processing, the additive filaments are wound onto a reel.

[0059] 2) Use a drainage hood to isolate the additive manufacturing area from the surrounding water. After draining the water from the drainage hood, introduce argon gas into the drainage hood as a protective gas.

[0060] 3) Place the coated additive flat strip above the substrate, adjust the tilt angle β of the gas metal arc welding torch to 35°, and symmetrically distribute the two gas metal arc welding torches on both sides of the substrate. Arc additive process parameters: current is 250A, voltage is 18V, moving speed is 5mm / s, extension length of additive wire is 30mm, and additive shielding gas is 90% argon + 10% carbon dioxide.

[0061] Turn on the arc additive manufacturing device and start the additive manufacturing process. The wire of the gas metal arc welding device melts and the molten metal fills the angle between the additive strip and the substrate, so that the additive strip and the substrate form a good metallurgical bond. After the first layer of additive manufacturing is completed, control the interpass temperature to 130℃.

[0062] 5) Keep the two gas metal arc welding torches at the same angle, raise the height of one layer of additive strip, place the additive strip above the first layer of strip, and carry out the subsequent additive work according to the additive process in 3) until all the arc additive work of 100mm and a total of 17 layers is completed.

[0063] The arc additive manufacturing component made of EH36 marine steel with layered composite material has a tensile strength of 575 MPa, an elongation of 26%, an impact energy of 132 J (-40℃), and a residual stress of 80 MPa.

[0064] The additive components produced by the underwater local dry layered composite material arc additive manufacturing method have a tensile strength greater than 500MPa, an elongation of ≥20%, an impact energy of ≥90J(KV2) at -40℃~0℃, and a residual stress ≤100MPa.

[0065] To illustrate the present invention, the present invention has been appropriately and sufficiently described above through embodiments. The above embodiments are only for illustrating the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. An underwater localized dry layered composite material arc additive manufacturing method, characterized in that, (1) Additive section design: The cross-sectional shape of the additive flat strip is a symmetrical convex hexagon composed of a rectangle and an isosceles trapezoid. The lower base of the isosceles trapezoid is the same length as the rectangle, and W:h:L = (3.5~6.5):1:(1.5~2.5); where W is the length of the rectangle, h is the width of the rectangle, L is the upper base of the isosceles trapezoid, and the angle α between the hypotenuse and the upper base of the isosceles trapezoid is 30°~55°; the cross-sectional shape of the additive wire is circular with a diameter of 0.8~1.6mm; (2) Create a water-proof environment: Use a drainage cover to block the water around the additive manufacturing area and the work area, and after draining the water from the drainage cover, introduce argon gas into the drainage cover as a protective gas. (3) Two gas metal arc welding torches are symmetrically arranged on both sides of the substrate. The tilt angle β of the gas metal arc welding torch is 20°~40°, which is the angle between the welding torch and the horizontal line. The welding current of the additive wire is 100~300A, the welding voltage of the additive wire is 12~30V, the welding torch moving speed is 3~10mm / s, the extension length of the additive wire is 15~35mm, and the additive shielding gas is 80%~90% argon + 10%~20% carbon dioxide. Turn on the arc additive device and carry out additive work. The wire of the gas metal arc welding melts and the molten metal fills the angle between the additive flat strip and the substrate. The first layer of additive is carried out. (4) Keep the angle of the gas metal arc welding torch unchanged, raise the height of one layer of additive flat strip, place the additive flat strip above the first layer of flat strip, and carry out the subsequent additive work according to the additive process in step (3) until all additive welding work is completed.

2. The method for arc additive manufacturing of underwater locally dry layered composite materials according to claim 1, characterized in that, The chemical composition of the additive flat strip, by mass percentage, is as follows: C: 0.05%~0.15%, Si: 0.3%~1.5%, Mn: 0.5%~1.5%, S≤0.02%, P≤0.02%, Cr: 0.2%~0.6%, Ni: 0.5%~4.0%, Mo: 0.3%~1.0%, Ti: 0.02%~0.08%, with the balance being Fe and unavoidable impurities.

3. The method for arc additive manufacturing of underwater locally dry layered composite materials according to claim 1, characterized in that, The chemical composition range of additive flat strips and round wires is the same.

4. The method for arc additive manufacturing of underwater locally dry layered composite materials according to claim 1, characterized in that, Additive flat strips are extruded materials, while additive wires are cold-drawn wires.

5. The method for arc additive manufacturing of underwater locally dry layered composite materials according to claim 1, characterized in that, Additive components produced by the underwater local dry layered composite material arc additive manufacturing method have a tensile strength greater than ≥500MPa, an elongation of ≥20%, an impact energy of ≥90J at -40℃ to 0℃, and a residual stress of ≤100MPa.

6. The method for arc additive manufacturing of underwater locally dry layered composite materials according to claim 1, characterized in that, After step (3) is completed and before the next layer of additive manufacturing is completed, the temperature of the additive flat strip is controlled at 100~150℃.

7. The method for arc additive manufacturing of underwater locally dry layered composite materials according to claim 1, characterized in that, The additive components produced by the underwater local dry layered composite material arc additive manufacturing method have a layered internal structure, wherein the layered structure consists of alternating arc additive deposition layers and additive flat strip solid phase layers.

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