A superior pitting-resistant nickel-based electrode and a method for preparing the same

Abstract

The application provides a kind of excellent pitting-resistant nickel-based electrode, including welding core and electrode coating powder coated on the surface of welding core, and each component of the electrode coating powder comprises, by weight percentage, 35-50% of sodium hexafluoroaluminate, 25-35% of barium carbonate, 5-10% of 95% rutile, 1-2% of rutile titanium dioxide, 5-10% of quartz, 4-6% of 70% micro-carbon chromium iron, 3-5% of niobium iron, 1-3% of manganese iron, 1-1.5% of calcium alginate, 0.5-1% of alkali surface.The electrode uses special welding core and adds a certain proportion of Nb and other alloy elements through the electrode coating powder formula, adjusts the chemical composition of the electrode deposited metal, realizes the characteristics that the electrode deposited metal has excellent mechanical properties and corrosion resistance, effectively improves the operability during manual welding, improves the welding efficiency and reduces the repair rate.

Description

Technical Field

[0001] This invention relates to the field of welding materials, and in particular to a nickel-based welding electrode with excellent pitting resistance and its preparation method. Background Technology

[0002] Corrosion is a widespread problem in the field of metallic materials, posing a significant threat to national economic development, human life, and the social environment. Metallic materials remain among the most important structural materials, widely used in petrochemicals, aerospace, offshore drilling platforms, boilers, and pressure vessels. Therefore, corrosion of metallic materials should be a key concern.

[0003] Corrosion directly impacts all sectors of the national economy, causing enormous direct losses to alloy materials. Preliminary statistics indicate that at least 10% of all metal products worldwide are scrapped annually due to corrosion, resulting in global losses exceeding US$800 billion annually, and approximately RMB 300 billion in my country each year. Beyond the economic issues, the corrosion process and its consequences represent a significant waste of Earth's limited resources and energy. It causes severe environmental pollution, disrupts normal industrial production and daily life, and poses substantial social security risks. Furthermore, corrosion can be a major constraint on the development of high technology and the sustainable development of the national economy. To improve equipment reliability and lifespan, and reduce material usage, corrosion and protection science has gained widespread attention in various countries.

[0004] With the development of modern industry, the requirements for materials are becoming increasingly stringent. In order to meet various harsh usage conditions, the research and development of various new materials has received great attention. Correspondingly, welding materials have also developed accordingly. The product structure and variety of welding materials have undergone great changes. New and efficient welding materials have made great progress and have been widely used. Among them, the most widely used new special welding materials are stainless steel welding materials and nickel-based alloy welding materials.

[0005] Some existing nickel-based alloy welding electrodes lack sufficient corrosion resistance and have poor weldability. During welding, they exhibit varying degrees of poor arc stability, excessive welding spatter, and poor slag removal. Therefore, addressing these shortcomings is an urgent problem to be solved. Summary of the Invention

[0006] In view of this, the present invention aims to propose an excellent pitting corrosion resistant nickel-based welding electrode and its preparation method. The welding electrode uses a special welding core and adds a certain proportion of alloying elements such as Nb through the welding electrode powder formulation, thereby adjusting the chemical composition of the weld metal and achieving excellent mechanical properties and corrosion resistance of the weld metal. This effectively improves the operability of manual welding, increases welding efficiency, and reduces the rework rate.

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

[0008] A high-quality nickel-based welding electrode with excellent pitting resistance includes a core electrode and a coating powder covering the surface of the core electrode. The chemical composition of the core electrode, by weight percentage, includes: C ≤ 0.020%, Si ≤ 0.15%, Mn ≤ 0.50%, P ≤ 0.010%, S ≤ 0.010%, Ni ≥ 60.0%, Cr 20.0-22.0%, Mo 9.0-10.0%, Cu ≤ 0.20%, Fe ≤ 1.0%, and Nb. 4.0-4.5%, others ≤0.50%; the components of the electrode powder coating, by weight percentage, include: sodium hexafluoroaluminate 35-50%, barium carbonate 25-35%, 95% rutile 5-10%, rutile titanium dioxide 1-2%, quartz 5-10%, 70% micro-carbon ferrochrome 4-6%, ferroniobium 3-5%, ferromanganese 1-3%, calcium alginate 1-1.5%, and alkali 0.5-1%.

[0009] Furthermore, the components of the electrode coating powder, by weight percentage, include: sodium hexafluoroaluminate 48%, barium carbonate 27%, 95% rutile 6%, rutile titanium dioxide 2%, quartz 6%, 70% micro-carbon ferrochrome 4%, ferroniobium 3%, ferromanganese 2%, calcium alginate 1%, and baking soda 1%.

[0010] Furthermore, the components of the electrode coating powder, by weight percentage, include: sodium hexafluoroaluminate 42%, barium carbonate 33%, 95% rutile 8%, rutile titanium dioxide 1%, quartz 6%, 70% micro-carbon ferrochrome 4%, ferroniobium 3%, ferromanganese 1%, calcium alginate 1%, and baking soda 1%.

[0011] Furthermore, the components of the electrode coating powder, by weight percentage, include: 35% sodium hexafluoroaluminate, 34% barium carbonate, 10% 95% rutile, 1% rutile titanium dioxide, 7% quartz, 5% 70% micro-carbon ferrochrome, 4% ferroniobium, 2% ferromanganese, 1.5% calcium alginate, and 0.5% sodium hydroxide.

[0012] Furthermore, the components of the electrode coating powder, by weight percentage, include: 40% sodium hexafluoroaluminate, 30% barium carbonate, 9% 95% rutile, 2% rutile titanium dioxide, 7% quartz, 5% 70% micro-carbon ferrochrome, 4% ferroniobium, 1.5% ferromanganese, 1% calcium alginate, and 0.5% sodium hydroxide.

[0013] Nickel has a face-centered cubic structure, and its crystallographic stability allows it to accommodate more alloying elements (Cr, Mo, etc.) than iron-based alloys, thus enabling it to resist various environments. Therefore, nickel-based corrosion-resistant alloys, compared with general stainless steel and non-metallic materials, possess the ability to resist various forms of corrosion damage in various corrosive environments, and also have excellent mechanical and processing properties. Their overall corrosion resistance is far superior to stainless steel and other corrosion-resistant metals, making them more suitable for working under harsh conditions.

[0014] Sodium hexafluoroaluminate primarily functions to form slag and remove hydrogen. Under the influence of the welding arc, it ionizes to release F-, reducing the partial pressure of hydrogen in the arc atmosphere, achieving the same effect as carbonates. Sodium hexafluoroaluminate has a low melting point, effectively reducing the high-temperature viscosity of the slag, improving slag fluidity, and enhancing weld formation. This significantly improves welding processes and the mechanical properties of the deposited metal. However, if the amount of sodium hexafluoroaluminate added is less than 35%, the electrode penetration is insufficient, the weld pool has poor fluidity, and gas rise is inadequate. This leads to prolonged pauses at the bevel edge during weld operation, resulting in coarse weld ripples and a higher risk of porosity, lack of fusion, and slag inclusions. Therefore, the amount of sodium hexafluoroaluminate added should be controlled between 35% and 50%.

[0015] Barium carbonate undergoes stable decomposition under the action of a welding arc. The CO2 gas release process is stable along with the electrode coating melting process. After decomposition, the products of barium carbonate are BaO and CO2 gas, thus playing a role in slag formation and gas generation. BaO is a basic oxide that can increase the basicity of the slag, stabilize the arc, increase the interfacial tension between the slag and the metal surface, improve slag removal performance, and has good desulfurization ability. CO2 can reduce the hydrogen partial pressure in the arc atmosphere and reduce the hydrogen content of the weld. In order to control the acidity and alkalinity of the formula and the welding processability, the amount of barium carbonate added is controlled at 25%-35%.

[0016] The main function of 95% rutile is to balance the pH of the formulation, improve the physical properties of the slag, transform long slag into short slag, and improve the vertical welding performance of the welding electrode. This invention controls the addition of 95% rutile at 5%-10%.

[0017] The titanium dioxide used is rutile titanium dioxide, and its main function is to improve the welding processability of welding electrodes, enhance the plasticity and adhesion of the electrode coating, and facilitate electrode coating production. This invention controls the amount of titanium dioxide added to be 1%-2%.

[0018] Quartz primarily functions to form slag; an appropriate amount of quartz can increase the slag's activity. However, excessive quartz content can cause slag adhesion, excessive splattering, and noticeable explosions, leading to poor weld formation. This invention controls the quartz addition amount to 5%-10%.

[0019] The main function of 70% micro-carbon ferrochrome is to increase the chromium content in the weld metal and facilitate the formation of a Cr2O3 oxide film, giving the welding material excellent resistance to oxidation at both room temperature and high temperature, and improving its corrosion resistance. At the same time, compared to metallic chromium, it is more advantageous for molten iron flowability and spatter control. This invention controls the addition amount of 70% micro-carbon ferrochrome at 4%-6%.

[0020] The main function of ferroniobium is to improve the strength, plasticity, and heat and corrosion resistance of weld metal. Niobium (Nb) is a reinforcing element that forms stable NbC carbides, which are extremely stable. However, increasing Nb content leads to a decrease in elongation, caused by the increased volume ratio of NbFe2. Excessively high Nb content significantly reduces the toughness of the weld metal. Therefore, the addition of ferroniobium is controlled at 3%-5%.

[0021] The main function of ferromanganese is deoxidation and desulfurization, increasing the manganese content in the weld metal and improving the strength and plasticity of the weld metal. This invention controls the amount of ferromanganese added to be between 1% and 3%.

[0022] The main functions of calcium alginate and baking soda are lubricants. Adding calcium alginate and baking soda to welding electrodes can increase their coating properties. In this invention, the addition amounts of calcium alginate and baking soda are controlled at 1%-1.5% and 0.5%-1%, respectively.

[0023] The present invention also provides a method for preparing a high-quality pitting-resistant nickel-based welding electrode as described above. The method includes the following steps: weighing each component of the coating according to the proportion and mixing them evenly, then adding 20-21% water glass of the total weight of the coating and stirring evenly, then feeding it into a pressure coating machine to coat the surface of the welding core, and then baking it to obtain the electrode.

[0024] Furthermore, the glass is potassium-sodium silicate, with a potassium-sodium ratio of 1:1 and a Baumé concentration of 37-39°.

[0025] Furthermore, the baking process is as follows: first, it is baked at a low temperature of 50-100℃, then baked at a medium-high temperature of 150-360℃ for 4 hours, and then air-cooled to room temperature.

[0026] Compared with existing technologies, the superior pitting corrosion resistant nickel-based welding electrode and its preparation method described in this invention have the following advantages:

[0027] The superior pitting corrosion resistant nickel-based welding electrode of the present invention is a Na3AlF6+TiO2 slag system. This slag system effectively solves the process problems of poor arc stability, large spatter, and poor slag removal of traditional slag system welding electrodes. The reasonable alloy composition ratio and the control of impurity elements improve the microstructure of the weld, giving the weld excellent pitting corrosion resistance. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0029] The present invention will now be described in detail with reference to embodiments.

[0030] Example 1

[0031] A high-quality, pitting-resistant nickel-based welding electrode, comprising a core and a coating powder covering the core surface. The chemical composition of the core, by weight percentage, includes C≤0.020%, Si≤0.15%, Mn≤0.50%, P≤0.010%, S≤0.010%, Ni≥60.0%, Cr 20.0-22.0%, Mo9.0-10.0%, Cu≤0.20%, Fe≤1.0%, Nb 4.0-4.5%, and other ≤0.50%. The components of the coating are shown in Table 1.

[0032] The preparation method of this welding electrode is as follows:

[0033] Take the welding core and welding electrode powder, mix the components of the welding electrode powder evenly, and add 21% of 37-39°Be potassium-sodium mixed water glass (potassium to sodium ratio 1:1) to prepare wet powder. This wet powder, along with the welding core, is then used to prepare the welding electrode on a hydraulic production machine. The baking process involves first baking at a low temperature of 50-100℃, followed by baking at a medium-high temperature of 150-360℃ for 4 hours.

[0034] The welding electrodes produced according to the above process have a smooth surface, stable eccentricity, stable welding arc, minimal spatter, easy slag removal, excellent operability, and beautiful weld formation. The pitting corrosion test results for the welding electrodes are shown in Table 2.

[0035] Example 2

[0036] The difference between this embodiment and Example 1 is that the components of the drug coating are different, and the specific components are shown in Table 1.

[0037] The welding electrodes produced according to the above process have a smooth surface, stable eccentricity, stable welding arc, minimal spatter, easy slag removal, excellent operability, and beautiful weld formation. The pitting corrosion test results for the welding electrodes are shown in Table 2.

[0038] Example 3

[0039] The difference between this embodiment and Example 1 is that the components of the drug coating are different, and the specific components are shown in Table 1.

[0040] The welding electrodes produced according to the above process have a smooth surface, stable eccentricity, stable welding arc, minimal spatter, easy slag removal, excellent operability, and beautiful weld formation. The pitting corrosion test results for the welding electrodes are shown in Table 2.

[0041] Example 4

[0042] The difference between this embodiment and Example 1 is that the components of the drug coating are different, and the specific components are shown in Table 1.

[0043] The welding electrodes produced according to the above process have a smooth surface, stable eccentricity, stable welding arc, minimal spatter, easy slag removal, excellent operability, and beautiful weld formation. The pitting corrosion test results for the welding electrodes are shown in Table 2.

[0044] Comparative Example 1

[0045] The difference from Example 1 is that the core does not contain Nb.

[0046] Comparative Example 2

[0047] The difference from Example 1 is that the amount of Nb added to the core is 2.

[0048] Comparative Example 3

[0049] The difference from Example 1 is that the Nb addition ratio in the welding core is 5.

[0050] Table 1. Composition ratio of the drug coating in each embodiment (mass percentage %)

[0051] Drug coating components Example 1 Example 2 Example 3 Example 4 Sodium hexafluoroaluminate 48 42 35 40 Barium carbonate 27 33 34 30 95% Rutile 6 8 10 9 Rutile titanium dioxide 2 1 1 2 quartz 6 6 7 7 70% micro-carbon ferrochrome 4 4 5 5 niobium iron 3 3 4 4 Ferromanganese 2 1 2 1.5 Calcium alginate 1 1 1.5 1 baking soda 1 1 0.5 0.5

[0052] Table 2 shows the pitting corrosion test of welding electrodes according to ASTM G48 Method A.

[0053]

[0054] As can be seen from Table 2, the welding electrode prepared by the present invention has good corrosion resistance.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nickel-based welding electrode with excellent pitting corrosion resistance, characterized in that: The electrode comprises a welding core and a welding powder coating on the surface of the welding core. The chemical composition of the welding core, by weight percentage, includes C≤0.020%, Si≤0.15%, Mn≤0.50%, P≤0.010%, S≤0.010%, Ni≥60.0%, Cr 20.0-22.0%, Mo 9.0-10.0%, Cu≤0.20%, Fe≤1.0%, Nb 4.0-4.5%, and others≤0.50%. The components of the welding powder coating, by weight percentage, include: sodium hexafluoroaluminate 35-50%, barium carbonate 25-35%, 95% rutile 5-10%, rutile titanium dioxide 1-2%, quartz 5-10%, 70% micro-carbon ferrochrome 4-6%, ferroniobium 3-5%, ferromanganese 1-3%, calcium alginate 1-1.5%, and alkali 0.5-1%.

2. The excellent pitting corrosion resistant nickel-based welding electrode according to claim 1, characterized in that: The components of the electrode coating powder, by weight percentage, include: sodium hexafluoroaluminate 48%, barium carbonate 27%, 95% rutile 6%, rutile titanium dioxide 2%, quartz 6%, 70% micro-carbon ferrochrome 4%, ferroniobium 3%, ferromanganese 2%, calcium alginate 1%, and baking soda 1%.

3. The excellent pitting-resistant nickel-based welding electrode according to claim 1, characterized in that: The components of the electrode coating powder, by weight percentage, include: sodium hexafluoroaluminate 42%, barium carbonate 33%, 95% rutile 8%, rutile titanium dioxide 1%, quartz 6%, 70% micro-carbon ferrochrome 4%, niobium ferrochrome 3%, manganese ferrochrome 1%, calcium alginate 1%, and baking soda 1%.

4. The excellent pitting-resistant nickel-based welding electrode according to claim 1, characterized in that: The components of the electrode coating powder, by weight percentage, include: 35% sodium hexafluoroaluminate, 34% barium carbonate, 10% 95% rutile, 1% rutile titanium dioxide, 7% quartz, 5% 70% micro-carbon ferrochrome, 4% ferroniobium, 2% ferromanganese, 1.5% calcium alginate, and 0.5% sodium hydroxide.

5. The excellent pitting-resistant nickel-based welding electrode according to claim 1, characterized in that: The components of the electrode coating powder, by weight percentage, include: sodium hexafluoroaluminate 40%, barium carbonate 30%, 95% rutile 9%, rutile titanium dioxide 2%, quartz 7%, 70% micro-carbon ferrochrome 5%, ferroniobium 4%, ferromanganese 1.5%, calcium alginate 1%, and alkali 0.5%.

6. A method for preparing a superior pitting-resistant nickel-based welding electrode as described in any one of claims 1-5, characterized in that: The method includes the following steps: weigh each component of the coating according to the proportion, mix them evenly, add 20-21% water glass of the total weight of the coating and stir evenly, then send it into a pressure coating machine to coat the surface of the welding core, and bake it to obtain the coating.

7. The method for preparing the excellent pitting-resistant nickel-based welding electrode according to claim 5, characterized in that: The water glass is potassium-sodium water glass, with a potassium-sodium ratio of 1:1 and a Baumé concentration of 37-39°Bé.

8. The method for preparing the excellent pitting-resistant nickel-based welding electrode according to claim 5, characterized in that: The baking process is as follows: first, bake at a low temperature of 50-100℃, then bake at a medium-high temperature of 150-360℃ for 4 hours, and finally air-cool to room temperature.

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