Oxygen-control inversely-proportional alkaline slag system 2.25% Cr-1% Mo-0. 25V steel welding rod for hydrogenation reactor and preparation method thereof

Abstract

The invention discloses an oxygen-controlled inversely-proportional alkaline slag system 2.25% Cr-1% Mo-0. 25V steel welding rod for a hydrogenation reactor and a preparation method thereof, and belongs to the technical field of welding materials. The problem that a 2.25% Cr-1% Mo-V steel welding rod is poor in low-temperature toughness is solved. The welding rod is composed of a core wire and a coating on the surface of the core wire. The coating comprises CaF2, CaCO3, iron powder, quartz, 45 # ferrosilicon, electrolytic manganese, metal chromium powder, molybdenum powder, nickel powder, magnesium powder, titanium-boron alloy and sodium carbonate. A CaF2-CaO-SiO2 type inverse-proportion low-hydrogen alkaline slag system is adopted, so that non-metallic inclusions of deposited metal can be reduced, and weld joints are purified; and magnesium powder and MgO which has a deoxidizing effect and reacts with Mg and O are added into the coating, so that the alkalinity of the slag is improved, the inclusions in the slag are further reduced, the purity of the welding seam is improved, and the low-temperature impact toughness of deposited metal is improved. The welding rod is used for hydrogenation reactor welding.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a 2.25%Cr-1%Mo-0.25V steel welding electrode with oxygen control inverse proportion alkaline slag system for hydrogenation reactors and its preparation method. Background Technology With the development of hydrogenation technology, especially residue oil hydrotreating and coal hydroliquefaction, hydrogenation reactors are becoming increasingly larger. A new type of steel, 2.25%Cr-1%Mo-0.25V steel, characterized by high strength, high operating temperature, and good hydrogen resistance, has replaced traditional 2.25Cr~1Mo steel in the manufacture of hydrogenation reactors. Compared to ordinary 2.25Cr~1Mo steel, this new Cr~Mo steel has significant advantages in various aspects: higher strength and allowable stress, higher maximum operating temperature, and better hydrogen resistance. With the continuous development of industrial technology, this new Cr~Mo~V steel will find increasingly wider applications. However, due to the addition of V, it is very difficult to improve the low-temperature impact toughness of the weld metal. The development of welding materials for 2.25%Cr-1%Mo-0.25V has been very slow. Domestic patent CN113458656 discloses a 2.25%Cr-1%Mo-V steel welding electrode for hydrogenation reactors. It uses high-quality ultra-low P and S carbon steel core (C: ≤0.08%; P: ≤0.005%; S: ≤0.003%; P+S≤0.008%), adopts a high-alkalinity low-hydrogen slag system, and adds a certain proportion of rare earth fluorides to the formula. The rare earth cations ionized during the welding process are used for deoxidation, dehydrogenation, and purification of the weld, ensuring that the weld metal is low in oxygen and hydrogen and has high toughness. However, as is well known, high-basicity slag systems and rare earth fluorides are indeed effective in improving the low-temperature toughness of Cr~Mo steel welding electrodes. But for 2.25%Cr-1%Mo-0.25V steel welding electrodes, the addition of V greatly increases the difficulty of achieving low-temperature toughness. It is difficult to improve the low-temperature toughness of the electrode deposited metal by relying solely on high-basicity slag systems and rare earth fluorides. Moreover, the patent does not mention any other effective measures to further improve low-temperature flexibility.

[0002] Therefore, given the rapid development of hydrogenation reactors made of 2.25%Cr-1%Mo-0.25V steel, it is of great significance to overcome the adverse effects of V and develop a matching welding electrode for 2.25%Cr-1%Mo-0.25V steel hydrogenation reactors to solve the technical problem of insufficient low-temperature toughness of the weld metal in 2.25%Cr-1%Mo-0.25V steel welding electrodes. Summary of the Invention

[0003] To address the problem of insufficient low-temperature toughness in 2.25%Cr-1%Mo-0.25V steel welding electrodes, this invention provides a 2.25%Cr-1%Mo-0.25V steel welding electrode with oxygen control in an inverse proportion alkaline slag system for hydrogenation reactors and its preparation method.

[0004] The technical solution of the present invention is as follows: One objective of this invention is to provide a 2.25%Cr-1%Mo-0.25V steel welding electrode with oxygen control inverse proportion alkaline slag system for hydrogenation reactors. This electrode comprises a core and a coating covering the core surface. The coating contains magnesium powder, and its chemical composition by weight percentage includes: CaF2: 40%~50%, CaCO3: 15%~25%, iron powder: 8%~20%, quartz: 4%~8%, 45# ferrosilicon: 0.5%~1%, electrolytic manganese: 1%~3%, metallic chromium powder: 5%~7%, molybdenum powder: 2%-3%, nickel powder: 0.1%~0.5%, magnesium powder: 1%~4%, titanium-boron alloy: 1%~1.5%, and soda ash: 0.5%~1%.

[0005] Further specifying, the welding core is H08E welding core.

[0006] Furthermore, the chemical composition of the H08E welding core, by weight percentage, includes: C≤0.05%, Si≤0.20%, Mn: 0.45%~0.55%, P≤0.010%, S≤0.005%, with the balance being Fe.

[0007] Further specified, the weight percentage of CaF2 to the weight percentage of CaCO3 in the drug coating is ≥2.0.

[0008] Further specified, the weight percentage of CaF2 to the weight percentage of CaCO3 in the drug coating is ≥2.5.

[0009] Further specifying, the magnesium powder in the drug coating is 1.5-3% by weight.

[0010] Furthermore, the welding rods are specified to be low-hydrogen alkaline slag systems of the CaF2~CaO~SiO2 type.

[0011] Further specifying, the CaF2 in the herb coating is provided by fluorite, and the CaCO3 is provided by marble. A second objective of this invention is to provide a method for preparing the above-mentioned welding electrode, which includes the following steps: Step 1: Weigh marble, fluorite, iron powder, quartz, 45# ferrosilicon, electrolytic manganese, metallic chromium, molybdenum powder, nickel powder, magnesium powder, titanium boron alloy and soda ash according to the composition ratio of the welding rod, and mix them to obtain the welding rod coating powder. Step 2: Mix the electrode coating powder with potassium sodium water glass evenly to obtain a coating mixture. Then, use a pressure coating machine to coat the electrode core with the coating mixture. Finally, bake the electrode at low temperature, medium temperature and high temperature to obtain the electrode.

[0012] Further specified, the low-temperature baking temperature is 60℃ for 2 hours, the medium-temperature baking temperature is 150℃ for 2 hours, and the high-temperature baking temperature is 350℃ for 1 hour.

[0013] A third objective of this invention is to provide an application of the aforementioned welding electrode in the welding of a hydrogenation reactor.

[0014] The fourth objective of this invention is to provide a weld metal obtained from the above-mentioned application, wherein the chemical composition of the weld metal comprises, by weight percentage: C: 0.05%~0.15%, Si≤1.00%, Mn≤0.90%, P≤0.025%, S≤0.015%, Cr: 2.00%~2.60%, Ni: ≤0.30%, Mo: 0.90%~1.20%, V: 0.20%~0.40%, Nb: 0.010%~0.040%, O≤0.04%, and the balance being Fe.

[0015] Further specified, the oxygen content (O) of the deposited metal is ≤0.035%.

[0016] Further specified, the impact absorption energy of the deposited metal at -30℃ is ≥140J.

[0017] The beneficial effects of this invention are as follows: (1) The weld metal obtained after welding in this invention is heat-treated at (705±10)℃ for 8h. The room temperature tensile strength is ≥602MPa, the room temperature elongation after fracture is ≥18%, and the KV2 of the low temperature impact at -30℃ can be stably greater than 140J.

[0018] (2) The hydrogenation reactor of the present invention uses 2.25%Cr~1%Mo~0.25V steel welding rods. Magnesium powder is added to the coating. Magnesium powder has high activity and reacts violently with oxygen in the arc atmosphere during the welding process. On the one hand, it can play a strong deoxidation role, reduce the oxygen content in the weld metal, thereby reducing oxide inclusions in the weld metal and improving the low-temperature impact toughness of the weld metal. On the other hand, MgO produced by the reaction of Mg and O is alkaline. After entering the slag, it can increase the alkalinity of the slag, thereby further reducing inclusions in the slag, improving the purity of the weld metal, and further improving the low-temperature impact toughness of the weld metal.

[0019] (3) The welding electrode of the present invention adopts an inverse proportion low-hydrogen alkaline slag system of CaF2~CaO~SiO2 type. This slag system can effectively reduce non-metallic inclusions in the weld metal, play a role in purifying the weld, and significantly improve the impact toughness of the weld metal. Compared with the direct proportion slag system, the inverse proportion slag system of the present invention has a stronger desulfurization and dephosphorization capacity. Sulfur and phosphorus are harmful impurities in weld metal, which will seriously damage its toughness. By efficiently removing these impurities, the weld metal obtains better impact toughness at low temperature. In addition, the inverse proportion slag system means that the electrode coating contains more CaF2. The large presence of CaF2 can more effectively reduce the diffusible hydrogen content of the weld metal, thereby reducing the incidence of cold cracking in the weld metal, thus obtaining higher quality weld metal, which is also a guarantee for obtaining excellent low-temperature impact toughness. Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0024] The welding electrodes used in the following examples and comparative examples are of the inverse proportion low-hydrogen basic slag system of CaF2~CaO~SiO2 type, with H08E core and magnesium powder added to the coating.

[0025] Example 1 The welding electrode in this embodiment consists of a welding core and a coating covering the surface of the welding core; The composition of the powdered drug by mass fraction is as follows: CaF2: 46%, CaCO3: 23%, iron powder: 12.1%, quartz: 5%, 45# ferrosilicon: 1%, electrolytic manganese: 2.2%, metallic chromium powder: 5%, molybdenum powder: 2.8%, nickel powder: 0.4%, magnesium powder: 1%, titanium-boron alloy: 1%, soda ash: 0.5%; The chemical composition and mass percentage of the welding core are: C: 0.045%, Si: 0.10%, Mn: 0.49%, P: 0.006%, S: 0.003%, with the balance being Fe.

[0026] Example 2 The welding electrode in this embodiment consists of a welding core and a coating covering the surface of the welding core; The composition of the powdered drug by mass fraction is as follows: CaF2: 48%, CaCO3: 20%, iron powder: 8.2%, quartz: 8%, 45# ferrosilicon: 0.5%, electrolytic manganese: 2%, metallic chromium powder: 5.8%, molybdenum powder: 2.8%, nickel powder: 0.2%, magnesium powder: 2%, titanium-boron alloy: 1.5%, soda ash: 1%; The chemical composition and mass percentage of the welding core are: C: 0.042%, Si: 0.10%, Mn: 0.51%, P: 0.005%, S: 0.002%, with the balance being Fe.

[0027] Example 3 The welding electrode in this embodiment consists of a welding core and a coating covering the surface of the welding core; The composition of the powdered drug by mass fraction is as follows: CaF2: 48%, CaCO3: 20%, iron powder: 12.9%, quartz: 4%, 45# ferrosilicon: 0.5%, electrolytic manganese: 3%, metallic chromium powder: 6%, molybdenum powder: 2.8%, nickel powder: 0.3%, magnesium powder: 1%, titanium-boron alloy: 1%, soda ash: 0.5%; The chemical composition and mass percentage of the welding core are: C: 0.044%, Si: 0.08%, Mn: 0.54%, P: 0.006%, S: 0.003%, with the balance being Fe.

[0028] Comparative Example 1 The welding electrode in this comparative example consists of a core and a coating covering the surface of the core. The composition of the powdered drug by mass fraction is as follows: CaF2: 25%, CaCO3: 37%, iron powder: 17.2%, quartz: 4%, 45# ferrosilicon: 1%, electrolytic manganese: 4%, metallic chromium powder: 5.7%, molybdenum powder: 2.8%, nickel powder: 0.3%, magnesium powder: 1%, titanium-boron alloy: 1%, soda ash: 1%; The chemical composition and mass percentage of the welding core are: C: 0.045%, Si: 0.10%, Mn: 0.49%, P: 0.006%, S: 0.003%, with the balance being Fe.

[0029] Comparative Example 2 The welding electrode in this comparative example consists of a core and a coating covering the surface of the core. The composition of the powdered drug by mass fraction is as follows: CaF2: 24%, CaCO3: 40%, iron powder: 14.2%, quartz: 4%, 45# ferrosilicon: 1%, electrolytic manganese: 4%, metallic chromium powder: 5.7%, molybdenum powder: 2.8%, nickel powder: 0.3%, magnesium powder: 2%, titanium-boron alloy: 1%, soda ash: 1%; The chemical composition and mass percentage of the welding core are: C: 0.042%, Si: 0.10%, Mn: 0.51%, P: 0.005%, S: 0.002%, with the balance being Fe.

[0030] Comparative Example 3 The welding electrode in this comparative example consists of a core and a coating covering the surface of the core. The composition of the powdered drug by mass fraction is as follows: CaF2: 48%, CaCO3: 20%, iron powder: 13.4%, quartz: 5%, 45# ferrosilicon: 1%, electrolytic manganese: 3%, metallic chromium powder: 6%, molybdenum powder: 2.8%, nickel powder: 0.3%, titanium-boron alloy: 1%, soda ash: 0.5%; The chemical composition and mass percentage of the welding core are: C: 0.044%, Si: 0.08%, Mn: 0.54%, P: 0.006%, S: 0.003%, with the balance being Fe.

[0031] The welding electrodes used in the above embodiments and comparative examples were prepared using the following steps: Step 1: Weigh marble, fluorite, iron powder, quartz, 45# ferrosilicon, electrolytic manganese, metallic chromium, molybdenum powder, nickel powder, magnesium powder, titanium boron alloy and soda ash according to the composition ratio of the welding rod, and mix them to obtain the welding rod coating powder. Step 2: Mix the electrode coating powder with potassium sodium water glass evenly to obtain a coating mixture. Then, use a pressure coating machine to coat the electrode core with the coating mixture at a pressure of 10-18 MPa. Then, bake the electrode at a low temperature of 60℃ for 2 hours, a medium temperature of 150℃ for 2 hours, and a high temperature of 350℃ for 1 hour to obtain the electrode.

[0032] In the above embodiments and comparative examples, the welding electrode specification was φ4.0mm, the base material of the welding test plate was Q345R, the bevel was 22.5° on one side, the test plate size was 300mm×300mm, the welding process parameters shown in Table 1 were used for welding, the heat treatment parameters shown in Table 2 were used for heat treatment, the chemical composition of the deposited metal is shown in Table 3, and the mechanical properties of the deposited metal are shown in Table 4.

[0033] Table 1 Welding process parameters of welding electrodes

[0034] Table 2 Heat treatment parameters

[0035] Table 3 Chemical composition of deposited metal (wt%)

[0036] Table 4 Mechanical properties of welded metal

[0037] As can be seen from the data in Table 3, the low-temperature impact resistance of Examples 1-3 of the present invention is superior to that of Comparative Examples 1-3. Because the electrode of Comparative Example 1 uses a direct-ratio formulation, its molten pool smelting capacity is reduced, and the impurity content of the deposited metal increases, resulting in a decrease in its impact toughness. The electrode of Comparative Example 2, due to the increased CaCO3 / CaF2 ratio, has an increased oxygen content. Simultaneously, due to the reduced molten pool smelting capacity and increased impurity content in the deposited metal, its impact toughness decreases. The electrode of Comparative Example 3, due to the absence of magnesium powder, has a reduced deoxidizing capacity, increased oxygen content, and consequently, decreased impact toughness.

[0038] As can be seen from the comparison of the above embodiments and comparative examples, the welding electrode of the present invention, when combined with the welding process described in the present invention, has excellent mechanical properties and good impact toughness at a low temperature of -30℃.

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A 2.25%Cr-1%Mo-0.25V steel welding electrode for oxygen-controlled inverse-proportional alkaline slag system used in a hydrogenation reactor, characterized in that... The welding electrode consists of a core and a coating covering the surface of the core. The coating contains magnesium powder, and its chemical composition by weight percentage includes: CaF2: 40%~50%, CaCO3: 15%~25%, iron powder: 8%~20%, quartz: 4%~8%, 45# ferrosilicon: 0.5%~1%, electrolytic manganese: 1%~3%, metallic chromium powder: 5%~7%, molybdenum powder: 2%-3%, nickel powder: 0.1%~0.5%, magnesium powder: 1%~4%, titanium-boron alloy: 1%~1.5%, and soda ash: 0.5%~1%.

2. The welding electrode according to claim 1, characterized in that, The welding core is an H08E welding core.

3. The welding electrode according to claim 2, characterized in that, The chemical composition of the H08E welding core, by weight percentage, includes: C≤0.05%, Si≤0.20%, Mn: 0.45%~0.55%, P≤0.010%, S≤0.005%, with the balance being Fe.

4. The welding electrode according to claim 1, characterized in that, The weight percentage of CaF2 to the weight percentage of CaCO3 in the drug coating is ≥2.

0.

5. The welding electrode according to claim 1, characterized in that, The magnesium powder in the drug coating is 1.5-3% by weight.

6. The welding electrode according to claim 1, characterized in that, The welding rods use a low-hydrogen alkaline slag system of CaF2~CaO~SiO2 type.

7. A method for preparing a welding electrode according to any one of claims 1 to 6, characterized in that, The preparation method includes: Step 1: Weigh marble, fluorite, iron powder, quartz, 45# ferrosilicon, electrolytic manganese, metallic chromium, molybdenum powder, nickel powder, magnesium powder, titanium boron alloy and soda ash according to the composition ratio of the welding rod, and mix them to obtain the welding rod coating powder. Step 2: Mix the electrode coating powder with potassium sodium water glass evenly to obtain a coating mixture. Then, use a pressure coating machine to coat the electrode core with the coating mixture. Finally, bake the electrode at low temperature, medium temperature and high temperature to obtain the electrode.

8. The application of the inverse proportion alkaline slag system 2.25%Cr-1%Mo-0.25V steel welding electrode as described in any one of claims 1-6 in the welding of hydrogenation reactors.

9. A weld metal obtained by the application of claim 8, characterized in that, The chemical composition by weight percentage includes: C: 0.05%~0.15%, Si≤1.00%, Mn≤0.90%, P≤0.025%, S≤0.015%, Cr: 2.00%~2.60%, Ni: ≤0.30%, Mo: 0.90%~1.20%, V: 0.20%~0.40%, Nb: 0.010%~0.040%, O≤0.04%, with the balance being Fe.

10. The weld metal according to claim 9, characterized in that, Impact absorption energy at -30℃ ≥140J.

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