Low-temperature high-toughness nickel-based welding rod and preparation method thereof

Abstract

The application belongs to the technical field of welding material, and particularly relates to a low-temperature high-toughness nickel-based welding rod and a preparation method thereof. The nickel-based welding rod comprises a welding core, a rare earth modified graphene coating coated on the surface of the welding core, and a coating coated on the surface of the rare earth modified graphene coating. The preparation method of the rare earth modified graphene comprises the following steps: adding graphene oxide and yttrium chloride hexahydrate into water to perform a hydrothermal reaction, so as to obtain a modified graphene precursor; and calcining the modified graphene precursor in an inert gas atmosphere, so as to obtain the rare earth modified graphene. The rare earth modified graphene coated on the surface of the welding core can increase the arc stability, and can also serve as a strengthening phase to improve the strength and toughness of the weld in the cladded metal.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a low-temperature, high-toughness nickel-based welding electrode and its preparation method. Background Technology

[0002] In key industrial sectors such as heavy machinery, shipbuilding, and energy equipment, ductile iron and gray cast iron, with their superior damping, wear resistance, and excellent casting properties, have become the preferred materials for core components such as engine blocks, gearboxes, and machine tool beds. However, cast iron welding technology has long faced three major technical bottlenecks: First, the carbon content of cast iron (2.11%–4.0%) is much higher than that of steel, making it prone to forming hard and brittle martensitic structures during welding, with a probability of cracking after weld cooling exceeding 80%; second, rapid cooling easily leads to the formation of high-hardness white iron structures in the weld metal, resulting in brittle fracture and extremely poor machinability; third, the poor thermal conductivity of cast iron makes uneven heat input during welding prone to coarsening of the heat-affected zone (HAZ), significantly reducing joint toughness. These technical challenges result in cast iron welded repair parts having a service life of less than one-third of the original, necessitating the reliance on imported welding materials or direct equipment scrapping for major equipment repairs, causing huge losses to the global industrial sector every year.

[0003] Against this backdrop, nickel-based welding electrodes have emerged as a leader due to their unique properties. Nickel can form a stable Ni3C phase with carbon, effectively reducing free carbon concentration and inhibiting the formation of hard and brittle martensite. Simultaneously, the coefficient of thermal expansion of nickel-based alloys is close to that of cast iron, significantly reducing welding residual stress and decreasing cracking tendency by more than 60%. However, with technological advancements, the low-temperature toughness requirements for nickel-based welding electrodes are becoming increasingly stringent in fields such as liquefied natural gas (LNG) storage tanks and polar offshore platforms. Furthermore, the application of nickel-based welding electrodes still faces limitations: they are extremely sensitive to welding parameters (such as current, voltage, and preheating temperature), require extremely high arc stability, and are prone to porosity or lack of fusion during operation, restricting their large-scale adoption.

[0004] There is an urgent need for nickel-based welding electrodes that have excellent low-temperature toughness, stable arc, and superior mechanical properties. Summary of the Invention

[0005] The primary objective of this invention is to provide a low-temperature, high-toughness nickel-based welding electrode that possesses excellent high-temperature stability, effectively controls the hydrogen content of the weld, and improves the weld toughness.

[0006] The second objective of this invention is to provide a method for preparing a low-temperature, high-toughness nickel-based welding electrode.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A low-temperature, high-toughness nickel-based welding electrode, the nickel-based welding electrode comprising a core, a rare-earth modified graphene coating covering the surface of the core, and a flux coating covering the surface of the rare-earth modified graphene coating.

[0009] The preparation method of the rare earth modified graphene includes the following steps:

[0010] (1) Graphene oxide and yttrium hexahydrate were added to water, stirred, and allowed to stand for hydrothermal reaction. After filtration, washing and drying, the modified graphene precursor was obtained.

[0011] (2) The modified graphene precursor was calcined in an inert gas atmosphere to obtain the rare earth modified graphene.

[0012] Further, in step (1), the mass ratio of graphene oxide, yttrium chloride hexahydrate and water is 1:(1.5-2):(400-600); the stirring time is 2-4 hours; the settling time is 20-24 hours; the hydrothermal reaction temperature is 100-120°C and the time is 10-12 hours.

[0013] Furthermore, the calcination temperature in step (2) is 800–900°C, and the time is 1–2 hours.

[0014] Furthermore, the coating is composed of powder and binder; the binder is composed of the following raw materials: 70-75 wt% sodium potassium silicate, 17-20 wt% sodium carboxymethyl cellulose, and 8-10 wt% binder.

[0015] The preparation method of the adhesive additive includes the following steps:

[0016] (a) Add tridecylfluorooctyltriethoxysilane, sodium dodecyl sulfate and sodium persulfate to water and stir to obtain a pre-emulsion;

[0017] (b) The pre-emulsion is heated to react, and after the reaction, it is cooled to room temperature and butyl acrylate and hexafluorobutyl methacrylate are added. Then the temperature is raised to 70-85°C and sodium thiosulfate is added to react for 1-2 hours to obtain the adhesive.

[0018] Further, the mass ratio of tridecafluorooctyltriethoxysilane, sodium dodecyl sulfate, sodium persulfate and water in step (a) is (7-10):(0.8-1.2):(0.2-0.4):100.

[0019] Further, the heating reaction in step (b) is carried out at a temperature of 60-80°C for 1-2 hours; the mass ratio of the pre-emulsion, butyl acrylate, hexafluorobutyl methacrylate and sodium thiosulfate is 100:(30-60):(5-8):(0.5-0.8).

[0020] Furthermore, the powder is composed of the following raw materials: rutile: 20-33 wt%, marble: 8-12 wt%, chromium powder: 23-28 wt%, potassium cryolite: 7-14 wt%, electrolytic manganese: 8-12 wt%, atomized iron powder: 5-8 wt%, molybdenum powder: 3-6 wt%, barium carbonate: 2-5 wt%, lanthanum fluoride: 1-2 wt%, and dehydrated quartz sand: 1-2 wt%; the mass ratio of the powder to the binder is (3-4):1.

[0021] The preparation method of the above-mentioned low-temperature high-toughness nickel-based welding electrode includes the following steps:

[0022] (S1) Rare earth modified graphene is added to water to make a suspension. After preheating the welding core, the suspension is sprayed onto the surface of the welding core to form a rare earth modified graphene coating.

[0023] (S2) Mix the raw materials of the medicine powder, then add the binder and stir to obtain the medicine coating;

[0024] (S3) Apply the coating material to the surface of the rare earth modified graphene coating to form a coating, and dry it to obtain the low temperature high toughness nickel-based welding electrode.

[0025] Further, the concentration of the suspension in step (S1) is 1 to 1.5 mg / mL; the preheating temperature is 300 to 400 °C; and the thickness of the rare earth modified graphene coating is 50 to 100 μm.

[0026] Furthermore, the spraying parameters in step (S1) are as follows: spray gun power 30-35kW, current 700-750A, voltage 40-50V, air pressure 0.5-0.9MPa, gas flow rate 50-80L / min, suspension feed flow rate 20-40mL / min, spray gun moving speed 100-150mm / s, and spraying cycle number 40-60 times.

[0027] Furthermore, the drying temperature in step (S3) is 120-150°C, and the drying time is 3-5 hours; the coating of the welding electrode accounts for 20-30% of the total mass of the welding electrode.

[0028] The beneficial technical effects of this invention are as follows:

[0029] 1. This invention involves coating a nickel-based alloy welding core with rare-earth modified graphene. Modifying graphene using rare-earth compounds improves its dispersibility and bonding with the metal matrix, enhancing the welding stability of the coating and strengthening the weld's strength and toughness. This improvement also allows for an increase in the amount of rare-earth added, further reducing impurities in the cladding metal and thus enhancing the weld's mechanical properties. This invention also adds a bonding aid to the flux coating binder. This binder is prepared by forming a pre-emulsion from tridecafluorooctyltriethoxysilane and sodium dodecyl sulfate under the catalysis of sodium persulfate, followed by a reaction of this pre-emulsion with butyl acrylate and hexafluorobutyl methacrylate. Butyl acrylate has good film-forming properties, improving the hygroscopic resistance of the electrode coating. When combined with organosilicon, it improves the electrode's water resistance, adhesion, and thermal stability, reduces the coating's moisture content, thereby reducing the diffusible hydrogen content in the weld metal, preventing hydrogen-induced delayed cracking, and improving the weld's toughness, strength, and other mechanical properties.

[0030] 2. This invention provides a method for preparing a low-temperature, high-toughness nickel-based welding electrode, which is simple to prepare and beneficial for large-scale production. Detailed Implementation

[0031] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0032] The nickel-based welding core described in this invention can be a commercially available welding core, with no special requirements. In the following examples and comparative examples, the nickel-based welding core used is a NiCrMo-3 nickel-based alloy, with the following composition: Cr: 20–23 wt%, Mo: 8–10 wt%, Nb: 3–4 wt%, Fe: ≤5 wt%, and the balance being Ni.

[0033] (I) Implementation Examples

[0034] Example 1

[0035] Example 1 provides a low-temperature high-toughness nickel-based welding electrode, comprising a welding core, a rare earth modified graphene coating covering the surface of the welding core, and a flux coating covering the surface of the rare earth modified graphene coating.

[0036] The specific preparation process of the above rare earth modified graphene is as follows:

[0037] (1) Graphene oxide and yttrium hexahydrate were added to water at a ratio of 1:1.8:500 and stirred for 3 hours. After mixing evenly, the mixture was allowed to stand for 22 hours. After standing, the mixture was subjected to hydrothermal reaction at 110°C for 11 hours. After the reaction solution was cooled to room temperature, it was filtered, washed with water, and dried to obtain the modified graphene precursor.

[0038] (2) The modified graphene precursor was calcined at 850°C under a nitrogen atmosphere for 1.5 h to obtain rare earth modified graphene.

[0039] The aforementioned coating is composed of powdered medicine and binder in a mass ratio of 3:1. The binder is composed of the following raw materials: 73wt% sodium potassium water glass, 18wt% sodium carboxymethyl cellulose, and 9wt% binder; the powdered medicine is composed of the following raw materials: 23wt% rutile, 10wt% marble, 26wt% chromium powder, 11wt% potassium cryolite, 10wt% electrolytic manganese, 7wt% atomized iron powder, 5wt% molybdenum powder, 4wt% barium carbonate, 2wt% lanthanum fluoride, and 2wt% dehydrated quartz sand.

[0040] The specific preparation process of the above-mentioned adhesive additive is as follows:

[0041] (a) Add tridecafluorooctyltriethoxysilane, sodium dodecyl sulfate and sodium persulfate to water in a mass ratio of 8:1:0.3:100 and stir for 1.25 h to obtain a preemulsion;

[0042] (b) The pre-emulsion was heated to 70°C and reacted for 1.5 h. After the reaction, it was cooled to room temperature and butyl acrylate and hexafluorobutyl methacrylate were added. The temperature was then raised to 80°C and sodium thiosulfate was added, and the reaction was carried out for 1.5 h to obtain the adhesive additive. The mass ratio of the pre-emulsion, butyl acrylate, hexafluorobutyl methacrylate and sodium thiosulfate was 100:40:6:0.7.

[0043] Example 1 also provides a method for preparing the above-mentioned low-temperature high-toughness nickel-based welding electrode, the specific preparation process of which is as follows:

[0044] (S1) Rare earth modified graphene was added to water to prepare a suspension with a concentration of 1.2 mg / mL. After the welding core was preheated to 350℃, the suspension was sprayed onto the surface of the welding core using plasma spraying to form a rare earth modified graphene coating with a thickness of 80 μm. The spraying parameters were as follows: spray gun power 32kW, current 720A, voltage 45V, air pressure 0.8MPa, gas flow rate 70L / min, suspension feed flow rate 30mL / min, spray gun moving speed 120mm / s, and spraying cycle number 50 times.

[0045] (S2) Mix all the raw material components of the medicine powder evenly, then add the binder and stir to obtain the medicine coating;

[0046] (S3) Apply the coating material to the surface of the above rare earth modified graphene coating to form a coating, let it stand and dry, and then dry it at 130°C for 4 hours to obtain a low-temperature high-toughness nickel-based welding electrode; wherein the coating accounts for 25% of the total mass of the welding electrode.

[0047] Example 2

[0048] Example 2 provides a low-temperature high-toughness nickel-based welding electrode, comprising a welding core, a rare earth modified graphene coating covering the surface of the welding core, and a flux coating covering the surface of the rare earth modified graphene coating.

[0049] The specific preparation process of the above rare earth modified graphene is as follows:

[0050] (1) Graphene oxide and yttrium hexahydrate were added to water at a ratio of 1:1.5:400 and stirred for 2 hours. After mixing evenly, the mixture was allowed to stand for 20 hours. After standing, the mixture was subjected to hydrothermal reaction at 100°C for 10 hours. Finally, the modified graphene precursor was obtained by filtration, washing and drying.

[0051] (2) The modified graphene precursor was calcined at 800℃ in a nitrogen atmosphere for 1 h to obtain rare earth modified graphene.

[0052] The aforementioned coating consists of powdered medicine and binder in a mass ratio of 4:1. The binder is composed of the following raw materials: 70 wt% sodium potassium silicate, 20 wt% sodium carboxymethyl cellulose, and 10 wt% binder. The powdered medicine consists of the following raw materials: 20 wt% rutile, 12 wt% marble, 28 wt% chromium powder, 14 wt% potassium cryolite, 8 wt% electrolytic manganese, 8 wt% atomized iron powder, 6 wt% molybdenum powder, 2 wt% barium carbonate, 1 wt% lanthanum fluoride, and 1 wt% dehydrated quartz sand.

[0053] The specific preparation process of the above-mentioned adhesive additive is as follows:

[0054] (a) Add tridecafluorooctyltriethoxysilane, sodium dodecyl sulfate and sodium persulfate to water in a mass ratio of 7:0.8:0.2:100 and stir for 1 hour to obtain a pre-emulsion;

[0055] (b) The pre-emulsion was heated to 60°C and reacted for 1 hour. After the reaction, it was cooled to room temperature and butyl acrylate and hexafluorobutyl methacrylate were added. The temperature was then raised to 70°C and sodium thiosulfate was added, and the reaction was carried out for 1 hour to obtain the adhesive additive. The mass ratio of the pre-emulsion, butyl acrylate, hexafluorobutyl methacrylate and sodium thiosulfate was 100:30:5:0.5.

[0056] Example 2 also provides a method for preparing the above-mentioned low-temperature high-toughness nickel-based welding electrode, the specific preparation process of which is as follows:

[0057] (S1) Rare earth modified graphene was added to water to prepare a suspension with a concentration of 1 mg / mL. After the welding core was preheated to 300℃, the suspension was sprayed onto the surface of the welding core using plasma spraying to form a rare earth modified graphene coating with a thickness of 50 μm. The spraying parameters were as follows: spray gun power 30kW, current 700A, voltage 40V, air pressure 0.5MPa, gas flow rate 50L / min, suspension feed flow rate 20mL / min, spray gun moving speed 100mm / s, and spraying cycle number 40 times.

[0058] (S2) Mix all the raw material components of the medicine powder evenly, then add the binder and stir to obtain the medicine coating;

[0059] (S3) Apply the coating material to the surface of the above rare earth modified graphene coating to form a coating, let it stand and dry, and then dry it at 120°C for 3 hours to obtain a low-temperature high-toughness nickel-based welding electrode; wherein the coating accounts for 20% of the total mass of the welding electrode.

[0060] Example 3

[0061] Example 3 provides a low-temperature high-toughness nickel-based welding electrode, which includes a welding core, a rare earth modified graphene coating on the surface of the welding core, and a flux coating on the surface of the rare earth modified graphene coating.

[0062] The specific preparation process of the above rare earth modified graphene is as follows:

[0063] (1) Graphene oxide and yttrium hexahydrate were added to water and stirred for 4 hours according to the ratio of 1:2:600. After mixing evenly, the mixture was allowed to stand for 24 hours. After standing, the mixture was subjected to hydrothermal reaction at 120°C for 12 hours. Finally, the modified graphene precursor was obtained by filtration, washing and drying.

[0064] (2) The modified graphene precursor was calcined at 900℃ in a nitrogen atmosphere for 2h to obtain rare earth modified graphene.

[0065] The aforementioned coating consists of powdered medicine and a binder in a mass ratio of 3:1. The binder is composed of the following raw materials: 75 wt% sodium potassium silicate, 17 wt% sodium carboxymethyl cellulose, and 8 wt% binding aid. The powdered medicine consists of the following raw materials: 33 wt% rutile, 8 wt% marble, 23 wt% chromium powder, 7 wt% potassium cryolite, 12 wt% electrolytic manganese, 5 wt% atomized iron powder, 3 wt% molybdenum powder, 5 wt% barium carbonate, 2 wt% lanthanum fluoride, and 2 wt% dehydrated quartz sand.

[0066] The specific preparation process of the above-mentioned adhesive additive is as follows:

[0067] (a) Add tridecafluorooctyltriethoxysilane, sodium dodecyl sulfate and sodium persulfate to water in a mass ratio of 10:1.2:0.4:100 and stir for 1.5 h to obtain a pre-emulsion;

[0068] (b) The pre-emulsion was heated to 80°C and reacted for 2 hours. After the reaction, it was cooled to room temperature and butyl acrylate and hexafluorobutyl methacrylate were added. The temperature was then raised to 85°C and sodium thiosulfate was added, and the reaction was carried out for 2 hours to obtain the adhesive additive. The mass ratio of the pre-emulsion, butyl acrylate, hexafluorobutyl methacrylate and sodium thiosulfate was 100:60:8:0.8.

[0069] Example 3 also provides a method for preparing the above-mentioned low-temperature high-toughness nickel-based welding electrode. The specific preparation process is as follows:

[0070] (S1) Rare earth modified graphene was added to water to prepare a suspension with a concentration of 1.5 mg / mL. After the welding core was preheated to 400℃, the suspension was sprayed onto the surface of the welding core using plasma spraying to form a rare earth modified graphene coating with a thickness of 100 μm. The spraying parameters were as follows: spray gun power 35kW, current 750A, voltage 50V, air pressure 0.9MPa, gas flow rate 80L / min, suspension feed flow rate 40mL / min, spray gun moving speed 150mm / s, and spraying cycle number 60 times.

[0071] (S2) Mix all the raw material components of the medicine powder evenly, then add the binder and stir to obtain the medicine coating;

[0072] (S3) Apply the coating material to the surface of the above rare earth modified graphene coating to form a coating, let it stand and dry, and then dry it at 150°C for 5 hours to obtain a low-temperature high-toughness nickel-based welding electrode; wherein the coating accounts for 30% of the total mass of the welding electrode.

[0073] (II) Comparative Example

[0074] Comparative Example 1

[0075] Comparative Example 1 is basically the same as Example 1, except that in the preparation process of nickel-based welding rod, rare earth modified graphene is replaced with an equal amount of a mixture of yttrium chloride hexahydrate and graphene oxide. That is, in step (S1), the mixed suspension of yttrium chloride hexahydrate and graphene oxide is sprayed onto the surface of the welding core. The amount of yttrium chloride hexahydrate and graphene oxide is the same as in Example 1.

[0076] Comparative Example 2

[0077] Comparative Example 2 is basically the same as Example 1, except that in the preparation process of nickel-based welding rod, rare earth modified graphene is replaced with an equal amount of graphene oxide, that is, in step (S1), a suspension of graphene oxide is sprayed onto the surface of the welding core.

[0078] Comparative Example 3

[0079] Comparative Example 3 is basically the same as Example 1, except that the adhesive additive in Example 1 is omitted.

[0080] Comparative Example 4

[0081] Comparative Example 4 is basically the same as Example 1, except that the adhesive additive in Example 1 is replaced with an equal amount of butyl acrylate.

[0082] (III) Test Examples

[0083] The low-temperature, high-toughness nickel-based welding electrodes prepared in Examples 1-3 and Comparative Examples 1-4 were used to test the welding performance of 9Ni steel. The welding process parameters were: current 120-130A, interpass temperature 120-130℃, and number of layers 6-8.

[0084] Mechanical properties: After welding, the yield strength, tensile strength, elongation after fracture and impact performance at -196℃ of each group of weld metal were tested according to GB / T2652~2008 "Tension test method for weld and deposited metal". The results are shown in Tables 1 and 2.

[0085] Table 1 Mechanical properties of weld metal from the examples and comparative cases

[0086] Group Yield strength ReL (MPa) Tensile strength Rm (MPa) Elongation A (%) Example 1 471 742 35 Example 2 467 740 32 Example 3 465 739 33 Comparative Example 1 377 659 26 Comparative Example 2 369 634 24 Comparative Example 3 389 681 28 Comparative Example 4 402 690 30

[0087] Table 2 Impact performance of welding electrodes from examples and comparative models at -196℃

[0088] Group / Impact Value (J) weld center Fusion Line Fusion line + 2mm Example 1 94 87 107 Example 2 92 86 105 Example 3 91 84 101 Comparative Example 1 74 68 83 Comparative Example 2 67 60 78 Comparative Example 3 76 70 85 Comparative Example 4 80 74 90

[0089] As shown in Tables 1-2, when welding is performed using the low-temperature high-toughness nickel-based welding electrodes prepared in Examples 1-3 of this invention, the weld has excellent mechanical strength and low-temperature toughness.

[0090] Compared to Example 1, Comparative Example 1 replaced rare earth modified graphene with an equal amount of a mixture of yttrium chloride hexahydrate and graphene oxide, and Comparative Example 2 replaced rare earth modified graphene with an equal amount of graphene oxide. Both examples showed reduced mechanical properties of the cladding metal and poor low-temperature toughness in the resulting nickel-based welding electrodes. Specific analysis reveals that graphene has good electrical and thermal conductivity, and as a coating, it can effectively dissipate heat generated during welding and stabilize the arc, preventing the electrode coating from reddening and cracking. Appropriate amounts of graphene in the cladding metal can also act as a reinforcing phase, improving the strength and toughness of the weld. However, graphene has poor dispersibility and interfacial bonding with nickel-based alloys, making its preparation as a coating difficult and unstable. Furthermore, excessive carbon can easily generate embrittlement phases in the weld metal, affecting the mechanical properties of the weld. This invention prepares a rare-earth modified graphene coating on the outer surface of a nickel-based alloy welding core. By modifying graphene with rare-earth compounds, the dispersibility of graphene and its bonding with the metal matrix can be improved, thereby enhancing the welding stability of the coating and increasing the strength and toughness of the weld. Simultaneously, this improvement also allows for an increase in the amount of rare-earth material added, further reducing impurities in the cladding metal and enhancing low-temperature toughness.

[0091] Compared to Example 1, Comparative Example 3 omitted the bonding agent from Example 1, and Comparative Example 4 replaced the bonding agent from Example 1 with an equal amount of butyl acrylate. During welding, the same phenomenon of decreased mechanical properties and low-temperature toughness of the nickel-based welding electrode was observed. Specific analysis reveals that the bonding agent of this invention is prepared by forming a pre-emulsion of tridecafluorooctyltriethoxysilane and sodium dodecyl sulfate under the catalysis of sodium persulfate, followed by reaction of this pre-emulsion with butyl acrylate and hexafluorobutyl methacrylate. Butyl acrylate has good film-forming properties, which can improve the moisture resistance of the electrode coating. When combined with organosilicon, it can improve the water resistance, adhesion, and thermal stability of the welding electrode, reduce the water content of the coating, thereby reducing the diffusible hydrogen content of the weld metal, preventing the occurrence of hydrogen-induced delayed cracking, and improving the toughness of the weld.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A low-temperature, high-toughness nickel-based welding electrode, characterized in that, The nickel-based welding electrode includes a welding core, a rare earth modified graphene coating covering the surface of the welding core, and a flux coating covering the surface of the rare earth modified graphene coating. The preparation method of the rare earth modified graphene includes the following steps: (1) Graphene oxide and yttrium hexahydrate were added to water, stirred, and allowed to stand for hydrothermal reaction. After filtration, washing and drying, the modified graphene precursor was obtained. (2) The modified graphene precursor was calcined in an inert gas atmosphere to obtain the rare earth modified graphene. The coating is composed of powdered medicine and a binder; the binder is composed of the following raw materials: 70-75 wt% sodium potassium silicate, 17-20 wt% sodium carboxymethyl cellulose, and 8-10 wt% binder. The preparation method of the adhesive additive includes the following steps: (a) Add tridecafluorooctyltriethoxysilane, sodium dodecyl sulfate and sodium persulfate to water and stir to obtain a preemulsion; (b) The pre-emulsion is heated to react, and after the reaction, it is cooled to room temperature and butyl acrylate and hexafluorobutyl methacrylate are added. Then the temperature is raised to 70~85 °C and sodium thiosulfate is added to react for 1~2 h to obtain the adhesive.

2. The low-temperature high-toughness nickel-based welding electrode according to claim 1, characterized in that, In step (1), the mass ratio of graphene oxide, yttrium chloride hexahydrate and water is 1:(1.5~2):(400~600); the stirring time is 2~4 h; the settling time is 20~24 h; the hydrothermal reaction temperature is 100~120 ℃ and the time is 10~12 h.

3. The low-temperature high-toughness nickel-based welding electrode according to claim 1, characterized in that, The calcination temperature in step (2) is 800~900 ℃ and the time is 1~2 h.

4. The low-temperature high-toughness nickel-based welding electrode according to claim 1, characterized in that, The mass ratio of tridecafluorooctyltriethoxysilane, sodium dodecyl sulfate, sodium persulfate and water in step (a) is (7~10):(0.8~1.2):(0.2~0.4):

100.

5. The low-temperature high-toughness nickel-based welding electrode according to claim 1, characterized in that, The heating reaction in step (b) is carried out at a temperature of 60-80 °C for 1-2 h; the mass ratio of the pre-emulsion, butyl acrylate, hexafluorobutyl methacrylate and sodium thiosulfate is 100:(30-60):(5-8):(0.5-0.8).

6. The low-temperature high-toughness nickel-based welding electrode according to claim 1, characterized in that, The powder is composed of the following raw materials: rutile: 20-33 wt%, marble: 8-12 wt%, chromium powder: 23-28 wt%, potassium cryolite: 7-14 wt%, electrolytic manganese: 8-12 wt%, atomized iron powder: 5-8 wt%, molybdenum powder: 3-6 wt%, barium carbonate: 2-5 wt%, lanthanum fluoride: 1-2 wt%, and dehydrated quartz sand: 1-2 wt%; the mass ratio of the powder to the binder is (3-4):

1.

7. The method for preparing the low-temperature high-toughness nickel-based welding electrode according to claim 6, characterized in that, Includes the following steps: (S1) Rare earth modified graphene is added to water to make a suspension. After preheating the welding core, the suspension is sprayed onto the surface of the welding core to form a rare earth modified graphene coating. (S2) Mix the raw materials of the medicine powder, then add the binder and stir to obtain the medicine coating; (S3) Apply the coating material to the surface of the rare earth modified graphene coating to form a coating, and dry it to obtain the low temperature high toughness nickel-based welding electrode.

8. The method for preparing low-temperature high-toughness nickel-based welding electrodes according to claim 7, characterized in that, The concentration of the suspension in step (S1) is 1~1.5 mg / mL; the preheating temperature is 300~400 ℃; and the thickness of the rare earth modified graphene coating is 50~100 μm.

9. The method for preparing low-temperature high-toughness nickel-based welding electrodes according to claim 7, characterized in that, The drying temperature in step (S3) is 120~150 ℃ and the time is 3~5 h; the coating of the welding electrode accounts for 20-30% of the total mass of the welding electrode.