Coated electrodes, electrodes and methods of making and use of the same in the surfacing of austenitic-ferritic dissimilar steel materials

Abstract

The present application discloses a kind of coating of electrode, electrode and its preparation method and application, coating includes by weight parts: 8.0-14.0 rutile, 6.0-8.0 marble, 1.5-3.5 fluoride, 1.5-3.0 mica, 5.0-9.0 potassium feldspar, 0.8-1.6 electrolytic manganese, 0.4-1.0 ferro titanium, 2.0-4.0 metal chromium, 1.0-3.0 metal nickel, 0.1-0.6 iron sand, 0.1-0.4 calcium sulfide and 0.4-0.6 soda ash;Coating and welding core constitute electrode, electrode is applied to austenite-ferrite dissimilar steel surfacing, and the plasticity and toughness of deposited metal after surfacing forming are good, and corrosion resistance is excellent, satisfy the surfacing requirement of petroleum, chemical, hydraulic and nuclear power equipment.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically to a coating of a welding electrode, the welding electrode itself, its preparation method, and its application in surfacing welding of austenitic-ferritic dissimilar steel materials. Background Technology

[0002] In recent years, with the large-scale development of industry, pollution has become increasingly serious, and the contradiction between industrial development and the improvement of people's living standards and the environment has become increasingly prominent. People around the world are becoming more and more aware of environmental protection. Government departments have begun to attach great importance to the environmental pollution caused by the chemical industry, actively promote energy conservation and emission reduction, promote cleaner production and circular economy, and have successively introduced a number of industrial policies to encourage the development of environmentally friendly petrochemical industries, encourage the petrochemical industry to increase the deep processing and recycling of end products, and reduce direct emissions into the atmosphere and water resources.

[0003] With the development of the petrochemical industry and technological advancements, hydrogen-producing equipment, represented by hydrogenation reactors, is widely used not only in oil refining and ethylene production but also in the coal-to-oil industry. Petroleum products from refineries must undergo hydrogenation to remove harmful impurities before leaving the plant. Hydrogenation reactors require resistance to high temperatures, high pressures, and corrosion from hydrogen and hydrogen sulfide. To enhance corrosion resistance and save costs, austenitic stainless steel is typically welded onto the inner wall of carbon steel or low-alloy steel base materials for protection, replacing the use of austenitic stainless steel as a single material. This technology is widely used in energy, chemical, and petroleum industries. In actual manufacturing, the welding method for austenitic stainless steel generally employs combined welding, using two welding materials with a transition layer and a surface layer. While combined welding can significantly improve the ductility and toughness of the weldment, reduce the tendency for brittle fracture and cracking, and improve overall utilization performance, it requires two processes, making the welding process cumbersome and potentially affecting weld quality. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing austenitic stainless steel uses combined welding, which requires two processes, making the welding process complicated and affecting the welding quality.

[0005] The first objective of this invention is to provide a coating for a welding electrode, wherein the raw materials of the coating, by weight, comprise: 8.0-14.0 parts rutile, 6.0-8.0 parts marble, 1.5-3.5 parts fluoride, 1.5-3.0 parts mica, 5.0-9.0 parts potassium feldspar, 0.8-1.6 parts electrolytic manganese, 0.4-1.0 parts ilmenite, 2.0-4.0 parts metallic chromium, 1.0-3.0 parts metallic nickel, 0-0.6 parts iron sand, 0.1-0.4 parts calcium sulfide, and 0.4-0.6 parts soda ash.

[0006] Rutile: Its main functions are slag formation, arc stabilization, and adjustment of slag viscosity. It plays a key role in the length of the slag.

[0007] Marble: Under the action of electric arc heat, it decomposes into CaO and CO2. It is a commonly used slag-forming and gas-forming material in the manufacture of welding electrodes. It can increase the basicity of molten slag, stabilize the electric arc, refine the molten droplets, increase the interfacial tension between molten slag and metal, improve slag removal, and has a good desulfurization capacity.

[0008] Fluorides: Their main functions are to purify the molten pool, reduce the surface tension of the liquid metal, improve the fluidity of the slag, reduce the sensitivity of the weld to porosity, and adjust the viscosity and temperature of the slag. They play a key role in the ductility and toughness of the weld and the length of the slag.

[0009] Mica: Its main functions are slag formation, slag thinning, and plasticizing.

[0010] Potassium feldspar: Its main functions are slag formation, arc stabilization, reducing the surface tension of liquid metal, improving the fluidity of molten slag, and adjusting the viscosity and temperature of molten slag.

[0011] Electrolytic manganese: Manganese is an austenitic element. Its addition can desulfurize and deoxidize, and can also introduce manganese into the weld, improving weld strength.

[0012] Ferro-titanium alloy: Its addition can play a role in early deoxidation, stabilizing the electric arc, and slag formation.

[0013] Metallic chromium: Chromium is a ferritic element. It can be introduced into the weld to improve the strength, yield point, and corrosion resistance of the weld metal.

[0014] Metallic nickel: Nickel is an austenitic element. The alloying agent, using powdered metallic nickel, transitions / infiltrates nickel into the weld, effectively improving the weld metal's ductility, toughness, and corrosion resistance.

[0015] Iron sand: Its main functions are slag formation, oxidizing agent, improving the fluidity of molten slag, and adjusting the viscosity and temperature of molten slag.

[0016] Soda ash: Used as a binder and to stabilize electric arcs.

[0017] Calcium sulfide: Experiments have shown that it is a slag remover and also has a slag-forming effect.

[0018] As one possible design, the raw material composition of the coating, by weight, includes: 11.0-14.0 parts rutile, 7.0-8.0 parts marble, 2.5-3.5 parts fluoride, 2.5-3.0 parts mica, 6.8-9.0 parts potassium feldspar, 1.2-1.6 parts electrolytic manganese, 0.8-1.0 parts ilmenite, 2.8-4.0 parts metallic chromium, 2.0-3.0 parts metallic nickel, 0.4-0.6 parts iron sand, 0.2-0.4 parts calcium sulfide, and 0.5-0.6 parts soda ash.

[0019] As one possible design, the raw material composition of the coating includes, by weight: 11.0 parts rutile, 7.0 parts marble, 2.5 parts fluoride, 2.5 parts mica, 6.8 parts potassium feldspar, 1.2 parts electrolytic manganese, 0.8 parts ilmenite, 2.8 parts metallic chromium, 2.0 parts metallic nickel, 0.4 parts iron sand, 0.2 parts calcium sulfide, and 0.5 parts soda ash.

[0020] As one possible design, the chemical composition of the raw material for the coating, by mass percentage, includes: rutile with TiO2 content ≥95%; marble with CaCO3 content ≥96%; fluoride with F content ≥53% and Na content ≤32%; mica with SiO2 content 48%-58% and Al2O3 content 26%-35%; potassium feldspar with SiO2 content 63%-73%, Al2O3 content 15%-24%, and K2 and NaO2 content ≥12%; electrolytic manganese with Mn content ≥99.5%; ferrotitanium with Ti content 25%-35%; metallic chromium with Cr content ≥99.2%; metallic nickel with Ni content ≥99.5%; iron sand with Fe3O4 content ≥97%; calcium sulfide with CaS content ≥99%; and soda ash with Na2CO3 content ≥96% and NaCl content ≤0.7%.

[0021] A second objective of this invention is to provide a welding electrode comprising a core coated with the aforementioned flux coating; the chemical composition of the core, by mass percentage, comprises: C≤0.020%, Mn 1.5%-2.0%, Si≤0.30%, P≤0.020%, S≤0.010%, Cr 23.0%-25.0%, Ni 12.0%-14.0%, Mo≤0.40%, Cu≤0.40%, N≤0.040%, with the balance being Fe and impurities.

[0022] As one possible design, the mass of the flux coating is 30%-45% of the mass of the core electrode.

[0023] A third objective of this invention is to provide a method for preparing the aforementioned welding electrode, comprising:

[0024] A binder is added to the raw material of the coating, and then it is wrapped around the welding core to obtain the welding electrode intermediate.

[0025] The welding electrode intermediate was dried sequentially at 100℃-150℃ and 300℃-400℃.

[0026] As one possible design, the adhesive comprises potassium sodium silicate in a weight ratio of 4 to 6 parts; the concentration of the potassium sodium silicate is 37.0°Be˝~39.0°Be˝.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. This invention uses calcium sulfide to remove and form slag. Calcium sulfide and other components work synergistically to enable one-time welding, and the weld after welding has excellent plasticity, toughness and corrosion resistance. It can meet the special requirements of welding for reaction and storage equipment in petroleum, chemical, hydraulic engineering, nuclear power and other industries. At the same time, it improves welding efficiency and welding quality. It can be applied to the welding of austenitic-ferritic dissimilar steel materials, such as dissimilar carbon steel and other dissimilar low alloy steels.

[0029] 2. Potassium sodium water glass is used as a binder in the preparation of welding electrodes, which can improve the adhesion of the coating. At the same time, the step-by-step drying (100℃-150℃ and 300℃-400℃) can ensure that the welding electrodes have less spatter, stable arc, good slag removal performance, more beautiful weld formation, excellent corrosion resistance, and good all-position operability during welding. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0031] Example 1: This example provides an austenitic-ferritic dissimilar steel overlay welding electrode. The raw material composition of the electrode coating, by weight, is as follows: rutile 8.0 kg, marble 7.8 kg, fluoride 1.8 kg, mica 3.0 kg, potassium feldspar 9.0 kg, electrolytic manganese 0.8 kg, ilmenite 0.4 kg, metallic chromium 2.0 kg, metallic nickel 3.0 kg, iron sand 0.4 kg, calcium sulfide 0.4 kg, and soda ash 0.4 kg;

[0032] The chemical composition of the electrode coating, by mass percentage, is as follows: rutile contains 95.2% TiO2, marble contains 97.3% CaCO3, fluorides contain 53.6% F and 30.4% Na, mica contains 53.2% SiO2 and 32.8% Al2O3, potassium feldspar contains 65.1% SiO2, 15.8% Al2O3, and a total of 13.6% KO2 and NaO2, electrolytic manganese contains 99.7% Mn, ferrotitanium contains 30.5% Ti, metallic chromium contains 99.4% Cr, metallic nickel contains 99.6% Ni, iron sand contains 97% Fe3O4, calcium sulfide contains 99.2% CaS, and soda ash contains 97% Na2CO3 and 0.5% NaCl.

[0033] The chemical composition of the iron-chromium-nickel-manganese alloy core of the welding electrode, by mass percentage, is as follows: C 0.016%, Mn 1.88%, Si 0.14%, P 0.016%, S 0.004%, Cr 23.60%, Ni 13.23%, Mo 0.03%, Cu 0.04%, N 0.021%, with the balance being Fe and impurities; the mass of the iron-chromium-nickel-manganese alloy core is 100 kg.

[0034] This embodiment also discloses a method for preparing the aforementioned welding electrode, including the following steps:

[0035] Step 1: Raw material pretreatment; Stir and mix the above-mentioned electrode coating powder evenly;

[0036] Step 2: Coating preparation; Add 5.8 kg of potassium sodium silicate with a concentration of 38°Be˝ and mix thoroughly;

[0037] Step 3: Press coating and molding; the mixed powder is wrapped onto the welding core using a pressing machine;

[0038] Step 4: Dry the finished product; bake the core material wrapped with the mixed powder at 120℃ for 5 hours, and then bake at 350℃ for 2 hours to obtain the austenitic-ferritic dissimilar steel overlay welding electrode.

[0039] Example 2: This example differs from Example 1 in that the weight of the raw materials of the electrode coating is different. In the preparation of the electrode, the baking temperatures are 100℃ and 400℃ respectively, while the rest are the same as in Example 1.

[0040] The austenitic-ferritic dissimilar steel surfacing electrode provided in this embodiment 2 has the following coating raw materials by weight: rutile 14.0 kg, marble 6.0 kg, fluoride 3.5 kg, mica 1.6 kg, potassium feldspar 5.0 kg, electrolytic manganese 1.6 kg, ilmenite 1.0 kg, metallic chromium 4.0 kg, metallic nickel 1.2 kg, iron sand 0.6 kg, calcium sulfide 0.1 kg, and soda ash 0.6 kg.

[0041] Example 3: This example differs from Example 1 in that the weight of the raw material composition of the electrode coating is different, but the rest is the same as in Example 1.

[0042] The austenitic-ferritic dissimilar steel surfacing electrode provided in this embodiment 3 has the following coating raw materials by weight: 11.0 kg rutile, 7.0 kg marble, 2.5 kg fluoride, 2.5 kg mica, 6.8 kg potassium feldspar, 1.2 kg electrolytic manganese, 0.8 kg ferrotitanium, 2.8 kg metallic chromium, 2.0 kg metallic nickel, 0.2 kg iron sand, 0.2 kg calcium sulfide, and 0.5 kg soda ash.

[0043] Example 4: This example differs from Example 1 in that the baking temperatures in the preparation of the welding rod are 150°C and 300°C, respectively, while the rest is the same as in Example 1.

[0044] Example 5: This example differs from Example 1 in that the chemical composition of the iron-chromium-nickel-manganese alloy core of the welding electrode is different, but the rest is the same as in Example 1.

[0045] The chemical composition of the iron-chromium-nickel-manganese alloy core of the welding electrode, by mass percentage, is as follows: C 0.002%, Mn 1.61%, Si 0.28%, P 0.001%, S 0.003%, Cr 24.42%, Ni 12.89%, Mo 0.35%, Cu 0.34%, N 0.037%, with the balance being Fe and impurities; the mass of the iron-chromium-nickel-manganese alloy core is 100 kg.

[0046] Example 6: The coating of a welding electrode provided in this example contains the following raw materials by weight: 14.0 kg rutile, 8.0 kg marble, 2.5 kg fluoride, 2.5 kg mica, 8.5 kg potassium feldspar, 1.2 kg electrolytic manganese, 0.8 kg ilmenite, 2.8 kg metallic chromium, 2.0 kg metallic nickel, 0.4 kg calcium sulfide, and 0.5 kg soda ash.

[0047] The chemical composition of the electrode coating, by mass percentage, is as follows: rutile contains 96.3% TiO2, marble contains 97.2% CaCO3, fluoride contains 55.4% F and 28% Na, mica contains 55.9% SiO2 and 27.2% Al2O3, potassium feldspar contains 70.8% SiO2, 18.7% Al2O3, and a total of 15.1% KO2 and NaO2, electrolytic manganese contains 99.8% Mn, ferrotitanium contains 29.4% Ti, metallic chromium contains 99.5% Cr, metallic nickel contains 99.8% Ni, iron sand contains 97% Fe3O4, calcium sulfide contains 99.5% CaS, and soda ash contains 976.1% Na2CO3 and 0.7% NaCl.

[0048] The chemical composition of the iron-chromium-nickel-manganese alloy core of the welding electrode, by mass percentage, is as follows: C 0.016%, Mn 1.88%, Si 0.14%, P 0.016%, S 0.004%, Cr 23.60%, Ni 13.23%, Mo 0.03%, Cu 0.04%, N 0.021%, with the balance being Fe and impurities; the mass of the iron-chromium-nickel-manganese alloy core is 100 kg.

[0049] This embodiment also discloses a method for preparing the aforementioned welding electrode, including the following steps:

[0050] Step 1: Raw material pretreatment; Stir and mix the above-mentioned electrode coating powder evenly;

[0051] Step 2: Coating preparation; Add 6.0 kg of potassium sodium water glass with a concentration of 37°Be˝ and mix thoroughly;

[0052] Step 3: Press coating and molding; the mixed powder is wrapped onto the welding core using a pressing machine;

[0053] Step 4: Dry the finished product; bake the core material wrapped with the mixed powder at 110℃ for 6 hours, and then bake at 300℃ for 3 hours to obtain the austenitic-ferritic dissimilar steel overlay welding electrode.

[0054] Comparative Example 1: Compared with Example 1, no calcium sulfide was added in this comparative example, but everything else was exactly the same as in Example 1.

[0055] Comparative Example 2: Compared with Example 1, this comparative example does not use two baking processes in the preparation of welding electrodes, but directly uses a temperature of 300°C for 5 hours to dry them.

[0056] Comparative Example 3: Compared with Example 1, this comparative example does not use two baking processes in the preparation of welding electrodes, but directly uses a temperature of 150°C for 10 hours to dry them.

[0057] Comparative Example 4: Compared with Example 1, this comparative example added 2 kg of calcium sulfide, and the rest was exactly the same as Example 1.

[0058] The austenitic stainless steel welding electrodes prepared in the above embodiments and comparative examples were subjected to surfacing experiments and welding processes:

[0059] For the test plate welding, DC reverse polarity was used, and welding was carried out in accordance with Article 9 of Part 3 of the Welding Procedure Qualification of the Welding Specification for Mechanical Equipment of Nuclear Island in Pressurized Water Reactor Nuclear Power Plant (NB-T20002.3-2013). Lateral bending test specimens and intergranular corrosion test specimens were prepared in accordance with the requirements of NB / T 20004-2011.

[0060] Testing methods for various material properties of welding electrodes:

[0061] Methods for detecting the chemical composition and ferrite number of deposited metal:

[0062] GB / T 223 Chemical Analysis Methods for Iron and Steel and Alloys

[0063] GB / T 11170-2008 Determination of Multi-Element Content in Stainless Steel by Spark Discharge Atomic Emission Spectrometry (Conventional Method)

[0064] GB / T 20123-2006 Determination of Total Carbon and Sulfur Content in Iron and Steel - Infrared Absorption Method After Combustion in a High-Frequency Induction Furnace (Conventional Method)

[0065] GB / T1954-2008 Determination of Ferrite Content in Welds of Chromium-Nickel Austenitic Stainless Steel

[0066] The chemical composition of the diluted weld metal of the austenitic-ferritic dissimilar steel overlay welding electrodes prepared in each embodiment is shown in Table 1.

[0067] 2. Testing methods for the properties of weld overlay metals:

[0068] NB / T 20004-2011 Physical and Chemical Testing Methods for Materials of Mechanical Equipment in Nuclear Island of Nuclear Power Plants

[0069] GB / T 4334 Corrosion of metals and alloys - Test method for intergranular corrosion of stainless steel

[0070] GB / T 2653-2008 Test method for bending of welded joints

[0071] The mechanical properties of the weld metal of the austenitic stainless steel welding electrodes prepared in each embodiment are shown in Table 2.

[0072] Table 1 Chemical composition (%) and ferrite number FN of the weld metal after dilution of austenitic-ferritic dissimilar steel overlay welding electrodes

[0073]

[0074] As can be seen from Table 1, when using the welding rod of the present invention for surfacing, the deposited metal is mainly composed of austenite with a low ferrite content, specifically 3%-8%.

[0075] Table 2 Properties of deposited metal after surfacing with austenitic-ferritic dissimilar steel electrodes

[0076]

[0077] As can be seen from Table 2 above, the welding electrode provided by the present invention is applied to the surfacing of austenitic-ferritic dissimilar steels. The deposited metal after surfacing has good plasticity and toughness and excellent corrosion resistance, which can meet the surfacing requirements of petroleum, chemical, hydraulic and nuclear power equipment. Furthermore, the performance of the deposited metal is unqualified when baking is used once, and the performance of the deposited metal is also unqualified when calcium sulfide is not added or when the amount added is too large.

[0078] Table 3 Welding process and welding defects of austenitic-ferritic dissimilar steel overlay welding electrodes

[0079]

[0080] Tables 1 to 3 also show that, compared with Comparative Examples 1 to 4, the welding electrodes obtained in Example 1, when calcium sulfide is lacking or when a large amount of calcium sulfide is used, or when the electrodes are baked once, have significantly worse weld metal performance after surfacing than those in Example 1, and cannot meet the surfacing requirements of petroleum, chemical, hydraulic and nuclear power equipment.

[0081] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An austenitic-ferritic dissimilar steel material electrode for surfacing, comprising a core, characterized in that, The welding core is coated with a flux coating; the chemical composition of the welding core, by mass percentage, includes: C≤0.020%, Mn 1.5%-2.0%, Si≤0.30%, P≤0.020%, S≤0.010%, Cr 23.0%-25.0%, Ni 12.0%-14.0%, Mo≤0.40%, Cu≤0.40%, N≤0.040%, with the balance being Fe and impurities; The raw material composition of the coating, by weight, includes: 8.0-14.0 parts rutile, 6.0-8.0 parts marble, 1.5-3.5 parts fluoride, 1.5-3.0 parts mica, 5.0-9.0 parts potassium feldspar, 0.8-1.6 parts electrolytic manganese, 0.4-1.0 parts ilmenite, 2.0-4.0 parts metallic chromium, 1.0-3.0 parts metallic nickel, 0-0.6 parts iron sand, 0.1-0.4 parts calcium sulfide, and 0.4-0.6 parts soda ash.

2. The welding electrode for overlay welding of austenitic-ferritic dissimilar steel materials according to claim 1, characterized in that, The raw material composition of the coating, by weight, includes: 11.0-14.0 parts rutile, 7.0-8.0 parts marble, 2.5-3.5 parts fluoride, 2.5-3.0 parts mica, 6.8-9.0 parts potassium feldspar, 1.2-1.6 parts electrolytic manganese, 0.8-1.0 parts ilmenite, 2.8-4.0 parts metallic chromium, 2.0-3.0 parts metallic nickel, 0.4-0.6 parts iron sand, 0.2-0.4 parts calcium sulfide, and 0.5-0.6 parts soda ash.

3. The welding electrode for overlay welding of austenitic-ferritic dissimilar steel materials according to claim 2, characterized in that, The raw materials of the coating, by weight, include: 11.0 parts rutile, 7.0 parts marble, 2.5 parts fluoride, 2.5 parts mica, 6.8 parts potassium feldspar, 1.2 parts electrolytic manganese, 0.8 parts ilmenite, 2.8 parts metallic chromium, 2.0 parts metallic nickel, 0.4 parts iron sand, 0.2 parts calcium sulfide, and 0.5 parts soda ash.

4. The welding electrode for overlay welding of austenitic-ferritic dissimilar steel materials according to claim 1, characterized in that, The chemical composition of the raw materials for the medicinal coating, by mass percentage, includes: rutile with TiO2 content ≥95%; marble with CaCO3 content ≥96%; fluoride with F content ≥53% and Na content ≤32%; mica with SiO2 content 48%-58% and Al2O3 content 26%-35%; potassium feldspar with SiO2 content 63%-73% and Al2O3 content 15%-24%; electrolytic manganese with Mn content ≥99.5%; ilmenite with Ti content 25%-35%; metallic chromium with Cr content ≥99.2%; metallic nickel with Ni content ≥99.5%; iron sand with Fe3O4 content ≥97%; calcium sulfide with CaS content ≥99%; and soda ash with Na2CO3 content ≥96% and NaCl content ≤0.7%.

5. The welding electrode for overlay welding of austenitic-ferritic dissimilar steel materials according to claim 1, characterized in that, The mass of the flux coating is 30%-45% of the mass of the welding core.

6. A method for preparing a welding electrode for surfacing austenitic-ferritic dissimilar steel materials as described in any one of claims 1-5, characterized in that, The preparation method includes: A binder is added to the raw material of the coating, and then it is wrapped around the welding core to obtain the welding electrode intermediate. The welding electrode intermediate was dried sequentially at 100℃-150℃ and 300℃-400℃.

7. The method for preparing a welding electrode for surfacing austenitic-ferritic dissimilar steel materials according to claim 6, wherein the adhesive comprises potassium sodium silicate, wherein the potassium sodium silicate comprises 4-6 parts by weight; and the concentration of the potassium sodium silicate is 37.0°Bé to 39.0°Bé.

8. The application of a welding electrode prepared by the preparation method as described in claim 6 or 7 in the surfacing of austenitic-ferritic dissimilar steel materials, characterized in that, The dissimilar steel materials include dissimilar carbon steel and dissimilar low-alloy steel.

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