Hydrogen-seepage-preventing copper-plating-free coating for underwater additive manufacturing and preparation method of hydrogen-seepage-preventing copper-plating-free coating

Abstract

The invention provides an anti-hydrogen-seepage copper-plating-free coating for underwater additive manufacturing and a preparation method. The coating comprises the following chemical components in percentage by mass: 25%-35% of Al2O3, 20%-30% of CaF2, 5%-15% of Na2SiO3, 1%-3% of Y2O3, 1%-5% of copper powder, 5%-15% of an adhesive, 15%-25% of an organic carrier, 1%-2% of a stabilizer and a flatting agent and inevitable impurities. By the adoption of the method, the problem that a welding wire coating falls off in the welding process is effectively solved, and the stability of long-time welding in the underwater additive manufacturing process is guaranteed; a hydrophobic layer is formed on the surface of the coating, so that the hydrolysis hydrogen permeation phenomenon caused by long-time storage of the welding wire in a marine environment is improved; therefore, the welding wire is protected from being corroded by moisture and water molecules, the service life of the welding wire is prolonged, the mechanical performance of an additive manufacturing component is improved, and welding defects are reduced.

Description

Technical Field

[0001] The invention belongs to the field of welding, and in particular relates to an underwater additive manufacturing welding wire coating that is anti-hydrogen permeation and copper-free. Background Art

[0002] The rapid development of marine engineering has led to a continuous demand for underwater welding technology, especially in the repair, construction and installation of marine structures. One of the main challenges facing underwater welding technology is the harsh conditions of the marine environment, including high pressure, high humidity and high salinity, which have a significant negative impact on the welding process and the quality of welded joints. Traditional wet underwater welding is difficult to ensure welding quality and has low efficiency due to the interference of water.

[0003] Local dry welding technology effectively improves welding quality and efficiency by creating a local dry environment in the welding area. However, even in a local dry environment, the performance of the welding wire itself still plays a vital role in the welding process and quality. Traditional copper-plated welding wire will produce a large amount of harmful wastewater during the production process, aggravating environmental pollution. At the same time, the copper plating layer is easy to peel off during the welding process, which will cause the welding wire to stick to the conductive nozzle and deteriorate the wire feeding performance, which will greatly affect the stability of the long-term welding process such as additive manufacturing. In addition, during long-term storage in the marine environment, the welding wire is easily corroded by water molecules, and a certain amount of hydrogen permeation occurs inside the welding wire, which will seriously affect the mechanical properties and corrosion resistance of the welded joint. Therefore, improving the anti-hydrogen permeation ability of the welding wire is also the key to ensuring the quality of underwater welding.

[0004] In response to the problem of copper-plated welding wire, major manufacturers have begun to transform to non-copper-plated welding wire. Non-copper-plated welding wire does not require pickling and copper plating during the production process, which is the development trend of green production. Due to the different materials of the coating, the coating purpose and the use processability of the coating are also very different. The current non-copper-plated welding wire coating is often for the purpose of environmental protection, lubrication, rust prevention and conductivity, but the impact of hydrogen permeation during long-term transportation at sea has not been considered. Therefore, it is extremely necessary to invent a non-copper-plated coating that is anti-hydrogen permeation for underwater additive manufacturing. Summary of the invention

[0005] The object of the present invention is to overcome the above problems and shortcomings and to provide a hydrogen permeation resistant copper-free welding wire coating for underwater additive manufacturing and a method for manufacturing the same.

[0006] The object of the invention is achieved in this way:

[0007] A hydrogen-proof copper-free welding wire coating for underwater additive manufacturing, characterized in that the chemical composition of the coating is as follows by mass percentage: Al2O3: 25% to 35%, CaF2: 20% to 30%, Na2SiO3: 5% to 15%, Y2O3: 1% to 3%, copper powder: 1% to 5%, adhesive: 5% to 15%, organic carrier: 15% to 25%, stabilizer and leveling agent: 1% to 2%, and unavoidable impurities.

[0008] The welding wire coating thickness is 50-70 μm.

[0009] The adhesive is modified epoxy resin.

[0010] The organic carrier is tetrafluoroethylene, polyimide or a mixture of the two.

[0011] The stabilizer is calcium stearate.

[0012] The leveling agent is polyvinyl alcohol.

[0013] The coating hardness is 200-300 HV, and the increase of the diffusible hydrogen content of the coated welding wire is less than 1.0 mL / 100 g after being placed in an environment with a temperature of 25° C. and a humidity of 70% for 180 days.

[0014] The chemical composition of the welding wire coating with excellent hydrolysis resistance is designed for the following reasons:

[0015] Al2O3: Purity ≥ 99.5%, particle size < 50μm. Alumina is also called corundum. In the coating, the hard particles of Al2O3 with high hardness can form a hard wear-resistant layer on the surface of the coating, which effectively resists wear. When the coating is subjected to friction, the Al2O3 particles can disperse and absorb the applied force, reducing the direct wear on the surface of the coating. If the Al2O3 content is too low, the wear resistance of the coating will be reduced, which may cause early wear or damage, but if the content is too high, it may reduce the toughness of the coating and increase the risk of brittle fracture. Therefore, the content of Al2O3 in the coating is controlled at 25% to 35%.

[0016] CaF2: Purity> 99.0%. CaF2 has excellent chemical stability and is not easy to react with other chemicals. It can form a dense protective film on the surface of the coating. The protective film can effectively isolate water molecules. In addition, it can change the surface energy of the coating, reduce the adhesion of water molecules on the surface of the coating, and form hydrophobic characteristics. Insufficient CaF2 content will reduce the hydrolysis resistance of the coating, and may degrade rapidly in a humid environment, causing hydrogen to penetrate into the welding wire. However, too high a content will increase the brittleness of the coating and affect the overall performance. Therefore, the content of CaF2 in the coating is controlled at 20% to 30%.

[0017] Na2SiO3: Purity ≥ 98.0%. The oxide on the metal surface can react chemically with the silicate in sodium silicate. The silicon-oxygen bond is a very strong chemical bond, and this bonding ability can provide very high adhesion. When the content of Na2SiO3 is insufficient, the adhesion of the coating decreases, which may cause the coating to fall off or peel off. Too high a content may cause incompatibility between the coating and the welding wire substrate, affecting the performance of the coating. Therefore, the content of Na2SiO3 in the coating is controlled at 5% to 15%.

[0018] Y2O3: Purity ≥ 99.9%, particle size < 200nm. Y2O3 can refine the grains of the welded joint and reduce the grain boundary area, thereby reducing the penetration rate of the corrosive medium at the grain boundary. It can also form an oxide film on the surface of the welded joint to further improve the corrosion resistance. When the content is low, the corrosion resistance of the welded joint is insufficient, and excessive addition will lead to unnecessary cost increases. Therefore, the content of Y2O3 is controlled at 1-3%.

[0019] Copper powder: purity ≥ 99.9%, average particle size 300-500nm. Copper powder is added to the coating to improve the conductivity of the coating. The particle size of the copper powder is selected to be 300-500nm, with good dispersibility. When the copper powder content is low, the conductivity of the coating may not be sufficient to support an efficient welding process, resulting in reduced welding efficiency and reduced welding quality; when the content exceeds 5%, the cost of the coating will increase, and the copper welding wire will also reduce the mechanical properties of the coating. Therefore, the content of copper powder is controlled at 1-5%.

[0020] Adhesive: modified epoxy resin, viscosity ≤500cps. Add adhesive to the coating; the adhesive should have good water resistance and stability, be suitable for underwater environment, and have low volatility to meet environmental protection requirements. The content of modified epoxy resin in the coating is controlled at 5-15%. Preferably, modified epoxy resin is added to the coating as an adhesive, and the modified epoxy resin has good water resistance and stability. When the content of modified epoxy resin is low, there will be insufficient bonding inside the coating, affecting the overall strength. Too high a content will cause the coating to be too hard and lack the necessary toughness.

[0021] Organic carrier: Organic carrier is added to the coating as the matrix of the coating to provide the required flexibility and chemical stability of the coating. The flexibility of the coating with less organic carrier is lower and it is easy to crack. The higher organic carrier will reduce the wear resistance and hardness of the coating and reduce the overall performance. Therefore, the content of organic carrier in the coating is controlled at 15% to 25%. Preferably, polytetrafluoroethylene (PTFE) and polyimide (PI) are added to the coating as the matrix of the coating, or a mixture of the two.

[0022] Stabilizer and leveling agent: viscosity ≤ 1000cps. Stabilizer and leveling agent are added to the coating to prevent degradation of the coating during processing and improve the surface quality of the coating. When the content of stabilizer and leveling agent is low, the coating is unstable during processing and the surface will be uneven. However, when the content is high, the coating will be too smooth, affecting the adhesion between the coating and the substrate. Therefore, the content of stabilizer and leveling agent is controlled at 1-2%. It is preferred to add calcium stearate as a stabilizer and polyvinyl alcohol as a leveling agent to the coating.

[0023] The second technical solution of the present invention is to provide a method for preparing an underwater additive manufacturing welding wire coating with excellent hydrolysis resistance, comprising the following steps:

[0024] (1) Material mixing stage

[0025] In a vacuum mixer, Al2O3 and CaF2 are first dry-mixed, followed by adding Na2SiO3, a binder, and deionized water for wet mixing, followed by adding Y2O3, copper powder, and an organic carrier, and finally adding a stabilizer and a leveling agent for stirring and mixing;

[0026] (2) Surface pretreatment of welding wire:

[0027] Surface activation: Use a high-frequency plasma generator to activate the surface of the welding wire, with a power of 750-850W and a time of 1.5-2.5 minutes;

[0028] Surface roughening: Use laser cleaning technology to roughen the surface, laser power 10 ~ 30W, action time: 5-20μs;

[0029] (3) Coating spraying:

[0030] The pretreated welding wire is coated with a coating using an automated spraying system at a spraying speed of 0.5 to 1 m / min and an ambient humidity of 40% to 50%;

[0031] (4) Coating curing: After spraying, the coating is preheated, cured and cooled after curing to complete the curing process of the coating; preheating: temperature 70-90°C, lasting 4-6 minutes; main curing: main curing temperature 140-160°C, main curing time 40-50 minutes; post-curing cooling: naturally cool to room temperature;

[0032] Furthermore, in the material mixing stage: Al2O3 and CaF2 are dry mixed for 5 to 10 minutes; Na2SiO3 is first added, and then the modified binder is added, and deionized water is added at the same time, and stirred for 10 to 15 minutes; Y2O3 is then added, followed by copper powder, and the above mixed materials are further refined by ultrasonic dispersion technology, and the refinement time is 15 to 30 minutes; after adding the organic carrier, stirring is continued for 5 to 10 minutes; finally, calcium stearate and polyvinyl alcohol are added, and stirred for 20 to 30 minutes to form a uniform coating material;

[0033] Further, the amount of deionized water added is 5% to 25% of the total mass of the coating mixture;

[0034] The beneficial effects of the present invention are:

[0035] 1. The above solution effectively improves the problem of wire coating shedding during welding and ensures the stability of long-term welding during underwater additive manufacturing;

[0036] 2. The hydrophobic layer is formed on the coating surface, which improves the hydrolysis and hydrogen permeation phenomenon caused by long-term storage of welding wire in the marine environment; thereby protecting the welding wire from moisture and water molecule erosion, extending the service life of the welding wire, improving the mechanical properties of additively manufactured components, and reducing the occurrence of welding defects;

[0037] 3. The use of coating makes the welding wire more environmentally adaptable and can remain stable in underwater environments, ensuring the reliability of welding operations under complex marine conditions; DETAILED DESCRIPTION

[0038] The present invention will be further described below by way of examples;

[0039] The composition of the welding wire coating of the embodiment of the present invention is shown in Table 1; the preparation method of the underwater additive manufacturing welding wire coating with excellent hydrolysis resistance comprises the following steps:

[0040] (1) Material mixing stage

[0041] In a vacuum mixer, Al2O3 and CaF2 are first dry-mixed, followed by adding Na2SiO3, a binder, and deionized water for wet mixing, followed by adding Y2O3, copper powder, and an organic carrier, and finally adding a stabilizer and a leveling agent for stirring and mixing;

[0042] Premixing: In a vacuum mixer, dry mix Al2O3 and CaF2 according to the proportion for 5 to 10 minutes to ensure uniform dispersion;

[0043] Wet mixing stage: first add Na2SiO3, then add modified epoxy resin, and add deionized water at the same time. The amount of deionized water added is 5% to 25% of the total mass of the coating mixture, and stir for 10 to 15 minutes;

[0044] Adding active materials and conductivity enhancers: Y2O3 and copper powder are uniformly dispersed and added to the above mixture in order, and ultrasonic dispersion technology is used to further refine the particles for 15 to 30 minutes to ensure uniform distribution of metal powder in the coating;

[0045] Organic carrier control: add organic carrier to adjust to the required content and continue stirring for 5 to 10 minutes;

[0046] Stabilization and leveling treatment: Finally, add stabilizer and leveling agent and stir for 20 to 30 minutes until a uniform coating material is formed;

[0047] (2) Surface pretreatment of welding wire:

[0048] Surface activation: Use a high-frequency plasma generator to activate the surface of the welding wire, with a power of 750-850W and a time of 1.5-2.5 minutes;

[0049] Surface roughening: Use laser cleaning technology to roughen the surface; laser power 10~30W, action time: 5~20μs;

[0050] (3) Coating spraying:

[0051] Use an automated spraying system to spray the pretreated welding wire with coating, and control the environmental conditions to ensure uniform coating coverage; Spraying: Use an automated spraying system with a spraying speed of 0.5 to 1 m / min to ensure uniform coating coverage; Environmental control: Humidity 40% to 50%;

[0052] During the coating spraying process, real-time monitoring and adjustment of spraying parameters are carried out to ensure the consistency of coating thickness;

[0053] Target thickness setting: The target thickness of the coating is set at 50-70 μm; ensure that the coating has sufficient wear resistance, corrosion resistance and adhesion; if the coating thickness is less than 50 μm, the coating may not provide sufficient protection, causing the welding wire to be susceptible to wear and corrosion in an underwater environment; the coating adhesion may be reduced, increasing the risk of coating peeling or falling off during welding; if the coating thickness exceeds 70 μm, it may cause the coating to be too thick, affecting the welding performance of the welding wire and the quality of the welded joint; too thick a coating may increase the unevenness during welding, resulting in welding stress concentration and an increased risk of welding defects;

[0054] Thickness measurement and control: Use a high-precision X-ray fluorescence thickness gauge or electronic micrometer to accurately measure the coating thickness; during the spraying process, ensure the coating thickness is uniform by real-time monitoring and adjusting the spraying parameters;

[0055] (4) Coating curing: After spraying, the coating is preheated, mainly cured, and then cooled down after curing to complete the curing process of the coating;

[0056] Preheating: preheating temperature 70 ~ 90 ℃, preheating time 4 ~ 6 minutes;

[0057] Main curing: main curing temperature 140 ~ 160 ℃, main curing time 40 ~ 50min;

[0058] Post-curing cooling: Natural cooling to room temperature;

[0059] The main process parameters of the welding wire coating and the surface treatment of the welding wire in the embodiment of the present invention are shown in Table 2. The main process parameters of the welding wire and the coating in the embodiment of the present invention are shown in Table 3. The Vickers hardness of the welding wire coating in the embodiment of the present invention is shown in Table 4. The diffusible hydrogen content of the welding wire coating in the embodiment of the present invention is shown in Table 5.

[0060] Table 1 Composition of welding wire coating of the embodiment of the present invention (wt%)

[0061]

[0062] Table 2 Main process parameters of welding wire coating and welding wire surface treatment according to the embodiment of the present invention

[0063]

[0064] Table 3 Main processing parameters of welding wire and coating in the embodiment of the present invention

[0065]

[0066] Table 4 Vickers hardness (HV) of welding wire coating of the embodiment of the present invention

[0067] Example 1 2 3 4 5 6 7 8 Welding wire copper coating (pure copper) Hardness value 243 230 270 255 285 295 220 236 85

[0068] Table 5 Diffusible hydrogen content of the internal welding wire (ER50-6) protected by the welding wire coating of the embodiment of the present invention (mL / 100g)

[0069]

[0070] In order to describe the present invention, the present invention is appropriately and fully illustrated by the examples in the above. The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made should be included in the protection scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A hydrogen-proof copper-free welding wire coating for underwater additive manufacturing, characterized in that: The chemical composition of the coating is as follows by mass percentage: Al2O3: 25% to 35%, CaF2: 20% to 30%, Na2SiO3: 5% to 15%, Y2O3: 1% to 3%, copper powder: 1% to 5%, adhesive: 5% to 15%, organic carrier: 15% to 25%, stabilizer and leveling agent: 1% to 2%, and unavoidable impurities.

2. The anti-hydrogen permeation copper-free welding wire coating for underwater additive manufacturing according to claim 1, characterized in that: The adhesive is modified epoxy resin.

3. The anti-hydrogen permeation copper-free welding wire coating for underwater additive manufacturing according to claim 1, characterized in that: The organic carrier is tetrafluoroethylene, polyimide or a mixture of the two.

4. The anti-hydrogen permeation copper-free welding wire coating for underwater additive manufacturing according to claim 1, characterized in that: The stabilizer is calcium stearate.

5. The anti-hydrogen permeation copper-free welding wire coating for underwater additive manufacturing according to claim 1, characterized in that: The leveling agent is polyvinyl alcohol.

6. The anti-hydrogen permeation copper-free welding wire coating for underwater additive manufacturing according to claim 1, characterized in that: The welding wire coating has a thickness of 50-70 μm, a coating hardness of 200-300 HV, and a diffusion hydrogen content increase of less than 1.0 mL / 100 g after the coated welding wire is placed in an environment of room temperature and 70% humidity for 180 days.

7. A method for preparing a hydrogen permeation-resistant copper-free welding wire coating for underwater additive manufacturing according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Material mixing stage In a vacuum mixer, Al2O3 and CaF2 are first dry-mixed, followed by adding Na2SiO3, a binder, and deionized water for wet mixing, followed by adding Y2O3, copper powder, and an organic carrier, and finally adding a stabilizer and a leveling agent for stirring and mixing; (2) Surface pretreatment of welding wire: Surface activation: Use a high-frequency plasma generator to activate the surface of the welding wire, with a power of 750-850W and a time of 1.5-2.5 minutes; Surface roughening: Use laser cleaning technology to roughen the surface, laser power 10 ~ 30W, action time: 5-20μs; (3) Coating spraying: The pretreated welding wire is coated with a coating using an automated spraying system at a spraying speed of 0.5 to 1 m / min and an ambient humidity of 40% to 50%; (4) Coating curing: After spraying, the coating is preheated, cured, and cooled after curing to complete the curing process of the coating; Preheating: temperature 70 ~ 90 ℃, lasting 4 ~ 6 minutes; main curing: main curing temperature 140 ~ 160 ℃, main curing time 40 ~ 50 minutes; post-curing cooling: natural cooling to room temperature.

8. The method for preparing a hydrogen permeation-resistant copper-free welding wire coating for underwater additive manufacturing according to claim 6, characterized in that: Material mixing stage: dry mix Al2O3 and CaF2 for 5 to 10 minutes; first add Na2SiO3, then add the modified adhesive, and add deionized water at the same time, and stir for 10 to 15 minutes; then add Y2O3, followed by copper powder, and use ultrasonic dispersion technology to further refine the above mixed materials for 15 to 30 minutes; continue stirring for 5 to 10 minutes after adding the organic carrier; finally, add calcium stearate and polyvinyl alcohol, stir for 20 to 30 minutes to form a uniform coating material.

9. The method for preparing a hydrogen permeation-resistant copper-free welding wire coating for underwater additive manufacturing according to claim 6, characterized in that: The amount of deionized water added is 5% to 25% of the total mass of the coating mixture.

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