A flux-cored welding wire for crude oil tanks, its preparation method and welding method thereon

Abstract

This invention provides a flux-cored welding wire for crude oil tanks, its preparation method, and welding method. The flux-cored welding wire comprises a closed steel strip and alloy powder encased within the steel strip. The alloy powder comprises, by mass fraction: 5-8 parts of micro-carbon ferrochrome powder; 1-3 parts of ferrovanadium powder; 1-3 parts of ferroboron powder; 6-9 parts of high-carbon ferromanganese powder; 15-20 parts of copper powder; 22-35 parts of nickel powder; 1-2 parts of ferrosilicon powder; 6-8 parts of ferromolybdenum powder; 5-7 parts of magnesium aluminum powder; 10-15 parts of reduced iron powder; 3.5-4.7 parts of rutile powder; 2.1-3.2 parts of feldspar powder; 2.3-3.1 parts of fluorite powder; and 0.1-0.3 parts of sodium fluorosilicate. The flux-cored welding wire provided by this invention has good strength and toughness, strong corrosion resistance after welding, and a stable arc with minimal spatter during welding.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, and in particular to a flux-cored welding wire for crude oil tanks, its preparation method, and welding method. Background Technology

[0002] Currently, crude oil transportation mainly relies on ship transport, which places higher demands on the welding materials of corrosion-resistant steel for crude oil tanks.

[0003] H2S gas volatilized from crude oil in the oil tanks accumulates on the inner surface of the deck. H2S undergoes a disproportionation reaction within the oil tanks, producing sulfur precipitates that adhere to the metal surface, causing severe corrosion. Furthermore, large amounts of H2S make the condensate in the oil tanks acidic, further exacerbating corrosion. Oil tanks are primarily constructed using welding processes. Differences in chemical composition and microstructure across different zones of the weld joint, along with stress-strain and stress concentration, lead to even more severe corrosion, particularly at the weld-base metal interface where corrosion grooves occur. The weld heat-affected zone (HAZ) is the most sensitive area to heat input. For thick plate welding using high heat input, coarse grains easily form in the HAZ, severely reducing the strength, toughness, and corrosion resistance of the weld metal. Traditional welding materials and methods cannot achieve a balance between strength, toughness, and corrosion resistance.

[0004] Therefore, there is a need to develop welding materials for crude oil tank steel plates that are strong, tough, and corrosion-resistant. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a flux-cored welding wire for crude oil tanks, its preparation method and welding method. By adjusting the proportion of each component, a flux-cored welding wire with low cost, stable arc, little spatter and uniform weld metal is obtained, and the weld metal has good strength, toughness and long-term corrosion resistance.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a flux-cored welding wire for crude oil tanks, the flux-cored welding wire comprising a closed steel strip and alloy powder encased inside the steel strip, the alloy powder comprising, by mass fraction:

[0008]

[0009]

[0010] The flux-cored welding wire for crude oil tanks provided by this invention achieves excellent strength, toughness, and corrosion resistance in the weld metal through the synergistic effect of its components. Specifically, the addition of high-carbon manganese iron powder during the welding cooling process allows manganese to suppress the formation of proeutectoid ferrite, increase the amount of acicular ferrite, and improve the strength and low-temperature toughness of the weld.

[0011] During the solidification process of weld metal, B can form precipitates M with aluminum, titanium, manganese, and vanadium. 23 B, M3B, where M represents any one or at least two of aluminum, titanium, manganese, or vanadium, plays a role in precipitation strengthening. Furthermore, excess B segregates towards austenite grain boundaries, lowering the grain boundary energy and thus inhibiting the formation of proeutectoid ferrite; due to Fe... 23 C and Fe 23 B forms before ferrite and can "pin" the grain boundaries of ferrite, thus inhibiting the coarsening of ferrite grains.

[0012] Steel powder and nickel powder are the main alloying elements for improving corrosion resistance. They can increase the density and viscosity of the rust layer on the weld surface. Ferrosilicon powder, with its silicon element, can improve the fluidity of the weld pool during welding, thereby enhancing the overall mechanical properties of the weld. Microcarbon ferrochrome powder, with its chromium element, can form high-hardness M3C7, M3C, and M... 23 (C,B) and M3(C,B), where M represents Fe and / or Cr, can improve the hardness and wear resistance of the matrix. The oil film layer at the bottom of the oil tank contains sludge and crude oil. During transportation, the sludge continuously washes over the surface of the oil tank. The highly wear-resistant weld surface provides good protection for the oil film layer, preventing pitting corrosion. The main element of magnesium-aluminum powder is aluminum. Adding a small amount of magnesium can improve the strength and hardness of the weld metal. The magnesium-aluminum component helps remove harmful impurities such as oxygen from the molten pool. Magnesium has a strong affinity for oxygen and sulfur, making it a good deoxidizer and desulfurizer. Aluminum can strongly reduce the austenite phase region of the molten pool during welding, increase the grain coarsening temperature, and refine the weld grains.

[0013] During welding, the weld seam must be filled with molten metal, and the welding time is relatively long, resulting in a wide heat effect zone. Adding reduced iron powder to the weld can prevent overheating and reduce the heat effect zone, allowing for the use of high current welding, significantly improving the deposition rate of the welding wire and increasing welding productivity. It can also increase the weld depth, stabilize the arc during welding, reduce spatter, produce aesthetically pleasing welds, and facilitate easy re-ignition of the arc after an interruption.

[0014] Fine, dispersed carbides (Cr) formed during the welding process 23C6, Cr7C3, TiC, VC, and Mo2C are used for precipitation strengthening and solid solution strengthening of the weld metal. Fine carbides pin grain boundaries, inhibiting grain growth and giving the weld metal good strength and toughness. By rationally controlling the proportion of fluorite powder, fluorine and carbon dioxide gases are generated during welding, providing good self-protection for the weld. Furthermore, the combination with fluorite, rutile, and feldspar powders improves the moisture resistance and fluidity of the alloy powder, ensuring arc stability and preventing cracks in the weld layer.

[0015] In this invention, the amount of micro-carbon ferrochrome powder is 5 to 8 parts, for example, 5 parts, 5.4 parts, 5.7 parts, 6 parts, 6.4 parts, 6.7 parts, 7 parts, 7.4 parts, 7.7 parts or 8 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] This invention limits the content of micro-carbon ferrochrome powder to the above-mentioned range. When the content of micro-carbon ferrochrome powder is reasonably controlled, it can effectively improve the strength and oxidation corrosion resistance of the weld metal. When the content is too low, the size of austenite grains cannot be effectively controlled. In addition, when the content of micro-carbon ferrochrome powder is low, chromium alloy cementite will be formed, which has poor stability. When the content of micro-carbon ferrochrome powder exceeds 8 parts, the strength and hardness of the weld metal increase significantly, while the toughness decreases sharply. It is necessary to add a heat treatment process to adjust its properties, which increases the welding process.

[0017] The amount of vanadium iron powder is 1 to 3 parts, for example, 1 part, 1.3 parts, 1.5 parts, 1.7 parts, 1.9 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts or 3 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] 1 to 3 parts of ferroboron powder, for example, 1 part, 1.3 parts, 1.5 parts, 1.7 parts, 1.9 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts or 3 parts, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] 6 to 9 parts of high-carbon manganese iron powder, for example, 6 parts, 6.4 parts, 6.7 parts, 7 parts, 7.4 parts, 7.7 parts, 8 parts, 8.4 parts, 8.7 parts, or 9 parts, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] This invention limits the content of high-carbon ferromanganese powder to the aforementioned range. During welding, Mn and Fe can dissolve indefinitely, and the high-carbon ferromanganese powder will form M7C3 carbides. The elements Ti and Nb in the flux-cored wire steel strip will promote the refinement of M7C3, providing nuclei for heterogeneous nucleation of M7C3 and refining the primary phase of M7C3. When the content is too low, it cannot provide enough nucleation sites for M7C3, causing the primary phase of M7C3 to grow and coarsen. When the content is too high, it promotes the formation of martensite, which will reduce the plasticity and welding performance of the welding wire metal.

[0021] The amount of copper powder is 15 to 20 parts, for example, 15 parts, 15.6 parts, 16.2 parts, 16.7 parts, 17.3 parts, 17.8 parts, 18.4 parts, 18.9 parts, 19.5 parts or 20 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] The amount of nickel powder is 22 to 35 parts, for example, 22 parts, 23.5 parts, 24.9 parts, 26.4 parts, 27.8 parts, 29.3 parts, 30.7 parts, 32.2 parts, 33.6 parts, or 35 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] 1 to 2 parts of ferrosilicon powder, for example, 1 part, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts or 2 parts, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] The amount of ferromolybdenum powder is 6 to 8 parts, for example, 6 parts, 6.3 parts, 6.5 parts, 6.7 parts, 6.9 parts, 7.2 parts, 7.4 parts, 7.6 parts, 7.8 parts or 8 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] 5 to 7 parts of magnesium aluminum powder, for example, 5 parts, 5.3 parts, 5.5 parts, 5.7 parts, 5.9 parts, 6.2 parts, 6.4 parts, 6.6 parts, 6.8 parts or 7 parts, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] The amount of reduced iron powder is 10 to 15 parts, for example, 10 parts, 10.6 parts, 11.2 parts, 11.7 parts, 12.3 parts, 12.8 parts, 13.4 parts, 13.9 parts, 14.5 parts or 15 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] The amount of rutile powder is 3.5 to 4.7 parts, for example, 3.5 parts, 3.64 parts, 3.77 parts, 3.9 parts, 4.04 parts, 4.17 parts, 4.3 parts, 4.44 parts, 4.57 parts, or 4.7 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Feldspar powder is 2.1 to 3.2 parts, for example, it can be 2.1 parts, 2.23 parts, 2.35 parts, 2.47 parts, 2.59 parts, 2.72 parts, 2.84 parts, 2.96 parts, 3.08 parts or 3.2 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] The amount of fluorite powder is 2.3 to 3.1 parts, for example, 2.3 parts, 2.39 parts, 2.48 parts, 2.57 parts, 2.66 parts, 2.75 parts, 2.84 parts, 2.93 parts, 3.02 parts or 3.1 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Sodium fluorosilicate is used in quantities of 0.1 to 0.3 parts, for example, 0.1, 0.13, 0.15, 0.17, 0.19, 0.22, 0.24, 0.26, 0.28 or 0.3 parts, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the carbon content in the micro-carbon ferrochrome powder is 0.1% to 0.15% by mass, for example, it can be 0.1%, 0.11%, 0.12%, 0.13%, 0.14% or 0.15%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the chromium content in the micro-carbon ferrochrome powder is 63-75% by mass, for example, it can be 63%, 64%, 65%, 67%, 69%, 70%, 71%, 72%, 73% or 75%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] This invention limits the content of each component in the micro-carbon ferrochrome powder to the above-mentioned range, based on the formulas for carbon equivalent and chromium equivalent in steel, where C eq This refers to carbon equivalent, Cr eq This refers to chromium equivalent. The carbon equivalent can be calculated from the chromium equivalent, with each element's letter representing its mass content. Based on experience: when C... eq When C <0.4%, the steel has no obvious hardening tendency, excellent weldability, and preheating is not required for welding; when C eq At concentrations between 0.4% and 0.6%, the hardening tendency of steel gradually becomes more pronounced, requiring appropriate preheating and controlled heat input; when C...eq When the content is >0.6%, the hardening tendency is stronger, and it is a more difficult material to weld, requiring higher preheating temperature and stricter process measures.

[0034]

[0035] Cr eq =Cr + Mo + 1.5Si + 0.5 × Nb

[0036] The carbon in micro-carbon ferrochrome powder can fix chromium, effectively enabling alloy infiltration. During welding, carbon and chromium can form fine Cr2C3 carbides, improving the corrosion resistance of the weld metal. When the carbon content is too low, the alloying elements in the welding wire cannot be effectively utilized; when the carbon content is too high, the welding performance is poor, placing higher demands on the welding process. When the chromium content is below 63%, the calculated Cr equivalent is below 12%. Only when the Cr equivalent exceeds 12% does the steel plate have good resistance to oxidative corrosion. When the Cr equivalent exceeds 15%, the strength and hardness will decrease, and the elongation and reduction of area will decrease accordingly. Therefore, the chromium content should not exceed 75%.

[0037] Preferably, the vanadium content in the vanadium-iron powder is 30-40% by mass, for example, it can be 30%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0038] Preferably, the boron content in the ferroboron powder is 4-6% by mass, for example, it can be 4%, 4.3%, 4.5%, 4.7%, 4.9%, 5.2%, 5.4%, 5.6%, 5.8% or 6%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the carbon content in the high-carbon ferromanganese powder is 2-4% by mass, for example, it can be 2%, 2.3%, 2.5%, 2.7%, 2.9%, 3.2%, 3.4%, 3.6%, 3.8% or 4%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, the manganese content in the high-carbon ferromanganese powder is 75-80% by mass, for example, it can be 75%, 75.6%, 76.2%, 76.7%, 77.3%, 77.8%, 78.4%, 78.9%, 79.5% or 80%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] Preferably, the silicon content in the ferrosilicon powder is 72-78% by mass, for example, it can be 72%, 72.7%, 73.4%, 74%, 74.7%, 75.4%, 76%, 76.7%, 77.4% or 78%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0042] Preferably, the molybdenum content in the ferromolybdenum powder is 55-60% by mass, for example, it can be 55%, 55.6%, 56.2%, 56.7%, 57.3%, 57.8%, 58.4%, 58.9%, 59.5% or 60%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0043] Preferably, the magnesium content in the magnesium-aluminum powder is 30-40% by mass, for example, it can be 30%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0044] Preferably, the aluminum content in the magnesium-aluminum powder is 60-70% by mass, for example, it can be 60%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69% or 70%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] Preferably, the titanium dioxide content in the rutile powder is ≥95%, for example, it can be 95%, 96%, 97% or 98%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the calcium fluoride content in the fluorite powder is ≥95%, for example, it can be 95%, 96%, 97% or 98%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the grain size of the alloy powder is 60 to 160 mesh, for example, it can be 60 mesh, 70 mesh, 80 mesh, 90 mesh, 100 mesh, 110 mesh, 120 mesh, 130 mesh, 150 mesh or 160 mesh, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] This invention controls the grain size of the alloy powder within the above-mentioned range. When the grain size is too low, the particles are too fine, which will reduce the fluidity of the flux. Although this is beneficial to ensure the filling of the welding wire, it increases the specific surface area of ​​the flux. During welding, the oxidation, burn-off and evaporation of alloying elements increase, which is not conducive to the transition of beneficial elements into the weld. When the grain size is too high, the flux in the flux-cored wire will have local voids or broken particles, which is not conducive to stable welding and ensuring welding quality.

[0049] Preferably, the nickel powder has a grain size of 150-160 mesh, the copper powder has a grain size of 150-160 mesh, and the reduced iron powder has a grain size of 90-120 mesh, for example, 90 mesh, 100 mesh, 110 mesh or 120 mesh, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] Preferably, the grain size of the ferrosilicon powder, ferromolybdenum powder, ferrovanadium powder, or ferroboron powder is independently 60 to 80 mesh, for example, 60 mesh, 70 mesh, or 80 mesh, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] The particle size of the alloy powder has a crucial impact on the performance of the final flux-cored wire. When the particle size is too large, it increases the porosity of the flux-cored wire during preparation, making it prone to powder breakage during wire drawing and resulting in uneven flux composition. Conversely, when the particle size is too small, it is prone to volatilization and spattering during the welding preheating stage. This invention creatively and preferably uses alloy powders with the above-mentioned grain size for matching. During the welding process, the temperature is higher in the molten entropy stage and lower in the molten pool stage. To effectively avoid air pollution, the composition of the flux-cored wire with multiple particle sizes can significantly improve the self-protection effect of the wire. This is because the use of smaller particles of nickel powder, copper powder, and reduced iron powder is more conducive to effective pre-deoxidation during the welding heating stage. At the same time, the use of slightly larger particles of ferrosilicon powder, ferromolybdenum powder, ferrovanadium powder, or ferroboron powder is more conducive to achieving alloy transfer during the droplet transfer process, and the product does not exhibit spattering. When the particles are too small or too large, or when the above-mentioned gradation is not used, the particles in the system are unevenly distributed, resulting in a decrease in the corrosion resistance of the weld after welding.

[0052] Preferably, the mass ratio of sodium fluorosilicate to fluorite powder is 0.03 to 0.05:1, for example, it can be 0.03:1, 0.04:1 or 0.05:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, the thickness of the steel strip is 0.3 to 0.5 mm, for example, it can be 0.3 mm, 0.32 mm, 0.35 mm, 0.38 mm, 0.4 mm, 0.42 mm, 0.45 mm, 0.48 mm or 0.5 mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Preferably, the width of the steel strip is 13 to 15 mm, for example, it can be 13 mm, 13.3 mm, 13.5 mm, 13.7 mm, 13.9 mm, 14.2 mm, 14.4 mm, 14.6 mm, 14.8 mm or 15 mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] Preferably, the steel strip is Inconel 718 steel strip.

[0056] Preferably, the alloy powder filling rate in the flux-cored wire is 30% to 36%, for example, it can be 30%, 30.7%, 31.4%, 32%, 32.7%, 33.4%, 34%, 34.7%, 35.4% or 36%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] In a second aspect, the present invention provides a method for preparing the flux-cored welding wire for crude oil tanks as described in the first aspect, the method comprising:

[0058] (1) Heat rutile powder, feldspar powder and fluorite powder to a first temperature for a first heat preservation, heat micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder and sodium fluorosilicate to a second temperature for a second heat preservation; mix all alloy powders, heat to a third temperature for a third heat preservation, and then cool to obtain the treated alloy powder; set grooves on the steel strip;

[0059] (2) The treated alloy powder is filled into the groove, and the steel strip is closed into a steel pipe by a forming machine;

[0060] (3) The welding wire head of the steel pipe is rolled into a point using a tipping machine, and the steel pipe is continuously drawn by a wire drawing machine to obtain the flux-cored welding wire.

[0061] This invention preferably uses micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder, rutile powder, feldspar powder, fluorite powder, and sodium fluorosilicate, which are dried and heat-treated for a certain period of time in different temperature ranges. Then, the two alloy powders are mixed evenly and kept at a third temperature. If the temperature is too high, it will promote the surface oxidation of the alloy powder, causing the alloy to be in a state similar to failure. If the temperature is too low, it will reduce the fluidity of the alloy powder, the dehumidification effect will be insignificant, the filling rate of the flux-cored wire will be reduced, and spatter will easily occur in the subsequent welding process.

[0062] The preparation method of flux-cored welding wire for crude oil tanks of the present invention has a simple process flow and can produce flux-cored welding wire with high strength, no spatter, and strong corrosion resistance.

[0063] Preferably, the first temperature in step (1) is 200 to 240°C, for example, it can be 200°C, 205°C, 209°C, 214°C, 218°C, 223°C, 227°C, 232°C, 236°C or 240°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] Preferably, the first heat preservation time is 1 to 2 hours, for example, it can be 1 hour, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] Preferably, the second temperature is 110 to 130°C, for example, it can be 110°C, 113°C, 115°C, 117°C, 119°C, 122°C, 124°C, 126°C, 128°C or 130°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] Preferably, the second heat preservation time is 40 to 60 minutes, for example, it can be 40 minutes, 43 minutes, 45 minutes, 47 minutes, 49 minutes, 52 minutes, 54 minutes, 56 minutes, 58 minutes or 60 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] Preferably, the third temperature is 500 to 550°C, for example, it can be 500°C, 505°C, 510°C, 515°C, 520°C, 525°C, 530°C, 535°C, 545°C or 550°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] The present invention preferably selects the first temperature, the second temperature and the third temperature range within the above range. The rutile powder, feldspar powder and fluorite powder selected at the first temperature have a large amount of moisture, requiring a relatively high dehumidification temperature, and some of the powders are easy to oxidize at high temperatures. Therefore, the second temperature range is relatively low. Finally, after mixing, a third heat preservation is performed at the third temperature, which can produce a flux-cored wire with more uniform powder distribution and better fluidity.

[0069] Preferably, the third heat preservation time is 20 to 30 minutes, for example, it can be 20 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes or 30 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0070] Preferably, the steel strip is first cleaned and dried before the groove is set.

[0071] Preferably, the drying temperature is 90-95℃, for example, it can be 90℃, 90.6℃, 91.2℃, 91.7℃, 92.3℃, 92.8℃, 93.4℃, 93.9℃, 94.5℃ or 95℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] Preferably, the drying time is 3 to 5 minutes, for example, 3 minutes, 3.3 minutes, 3.5 minutes, 3.7 minutes, 3.9 minutes, 4.2 minutes, 4.4 minutes, 4.6 minutes, 4.8 minutes or 5 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0073] Preferably, the speed of the molding machine in step (2) is 55 to 75 m / min, for example, it can be 55 m / min, 58 m / min, 60 m / min, 62 m / min, 64 m / min, 67 m / min, 69 m / min, 71 m / min, 73 m / min or 75 m / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0074] Preferably, the starting speed of the wire drawing machine in step (3) is 0.2 to 0.4 m / s, for example, it can be 0.2 m / s, 0.23 m / s, 0.25 m / s, 0.27 m / s, 0.29 m / s, 0.32 m / s, 0.34 m / s, 0.36 m / s, 0.38 m / s or 0.4 m / s, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] Preferably, the linkage and jogging speed of the wire drawing machine is 0.10 to 0.25 m / s, for example, it can be 0.10 m / s, 0.12 m / s, 0.14 m / s, 0.15 m / s, 0.17 m / s, 0.19 m / s, 0.2 m / s, 0.22 m / s, 0.24 m / s or 0.25 m / s, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0076] Preferably, the number of drawing cycles of the wire drawing machine is 7 to 10, for example, 7, 8, 9 or 10 times.

[0077] Preferably, the diameter of the flux-cored welding wire is 1.2 to 3.2 mm, for example, it can be 1.2 mm, 1.5 mm, 1.7 mm, 1.9 mm, 2.1 mm, 2.4 mm, 2.6 mm, 2.8 mm, 3 mm or 3.2 mm, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0078] Preferably, lubricating powder should be added to the wire drawing die box of the wire drawing machine, and the cooling water circuit should be kept unobstructed.

[0079] Thirdly, the present invention provides a welding method for flux-cored welding wire used in crude oil tanks, wherein the welding method uses the flux-cored welding wire for crude oil tanks described in the first aspect for welding.

[0080] Preferably, the arc voltage for welding is 28 to 33V, for example, it can be 28V, 29V, 30V, 31V, 32V or 33V, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0081] Preferably, the welding current is 300 to 350A, for example, it can be 300A, 305A, 310A, 315A, 320A, 325A, 330A, 335A, 345A or 350A, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0082] Preferably, the welding speed is 280-320 mm / min, for example, it can be 280 mm / min, 285 mm / min, 287 mm / min, 290 mm / min, 295 mm / min, 300 mm / min, 305 mm / min, 312 mm / min, 315 mm / min or 320 mm / min, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0083] Preferably, the welding wire extension length is 20-25mm, for example, it can be 20mm, 20.6mm, 21.2mm, 21.7mm, 22.3mm, 22.8mm, 23.4mm, 23.9mm, 24.5mm or 25mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] Preferably, the protective gas used in the welding is carbon dioxide.

[0085] Preferably, the flow rate of the shielding gas for welding is 20 to 25 L / min, for example, it can be 20 L / min, 20.6 L / min, 21.2 L / min, 21.7 L / min, 22.3 L / min, 22.8 L / min, 23.4 L / min, 23.9 L / min, 24.5 L / min or 25 L / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0086] Compared with the prior art, the present invention has at least the following beneficial effects:

[0087] (1) The flux-cored welding wire for crude oil tanks provided by the present invention has high strength and toughness, is not prone to spatter during use, and has high strength and strong corrosion resistance after welding.

[0088] (2) The preparation method of flux-cored welding wire for crude oil tanks provided by the present invention is simple and easy to industrialize, and the alloy powder is evenly mixed.

[0089] (3) The flux-cored welding wire for crude oil tanks provided by the present invention can significantly improve the strength and corrosion resistance of the weld when applied in the crude oil tank welding process. Attached Figure Description

[0090] Figure 1 This is a schematic diagram of the corrosion sample used in this invention.

[0091] Figure 2 This is a diagram of the apparatus for simulating corrosion tests according to the present invention.

[0092] Figure 3 This is a graph showing the corrosion test time and repetition rate of the present invention.

[0093] Figure 4 This is a fracture morphology diagram of the weld metal at -40℃ in Example 1 of the present invention.

[0094] Figure 5 This is a fracture morphology diagram of the weld metal at -40℃ in Example 2 of the present invention.

[0095] Figure 6This is a fracture morphology diagram of the weld metal at -40℃ in Comparative Example 1 of this invention.

[0096] Figure 7 This is a fracture morphology diagram of the weld metal at -40℃ in Comparative Example 2 of this invention.

[0097] Figure 8 This is a fracture morphology diagram of the weld metal in Comparative Example 3 of the present invention, obtained from an impact test at -40℃.

[0098] Figure 9 This is a fracture morphology diagram of the weld metal at -40℃ in Comparative Example 4 of this invention.

[0099] In the diagram: 1-weld; 2-base material. Detailed Implementation

[0100] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0101] As a specific embodiment of the present invention, a flux-cored welding wire for crude oil tanks is provided. The flux-cored welding wire comprises a closed steel strip and alloy powder encased inside the steel strip. The alloy powder comprises, by mass fraction:

[0102]

[0103]

[0104] The micro-carbon ferrochrome powder contains 0.1–0.15% carbon and 63–75% chromium by mass; the ferrovanadium powder contains 30–40% vanadium by mass; the ferroboron powder contains 4–6% boron by mass; the high-carbon ferromanganese powder contains 2–4% carbon and 75–80% manganese by mass; the ferrosilicon powder contains 72–78% silicon by mass; the ferromolybdenum powder contains 55–60% molybdenum by mass; the magnesium aluminum powder contains 30–40% magnesium by mass; the magnesium aluminum powder contains 60–70% aluminum by mass; the rutile powder contains ≥95% titanium dioxide by mass; and the fluorite powder contains ≥95% calcium fluoride by mass.

[0105] The steel strip has a thickness of 0.3-0.5 mm and a width of 13-15 mm. The steel strip is Inconel 718 steel strip, and the alloy powder filling rate in the flux-cored wire is 30-36%.

[0106] This specific embodiment also provides a method for preparing the flux-cored welding wire for crude oil tanks, the method comprising:

[0107] (1) Heat rutile powder, feldspar powder and fluorite powder to 200-240℃ for the first heat preservation for 1-2 hours. Heat micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder and sodium fluorosilicate to 110-130℃ for the second heat preservation for 40-60 minutes. Mix all alloy powders, heat to 500-550℃ for the third heat preservation for 20-30 minutes, and then cool to obtain the processed alloy powder. The steel strip is first cleaned and dried at 90-95℃ for 3-5 minutes, and grooves are set on the steel strip.

[0108] (2) The treated alloy powder is filled into the groove, and the steel strip is closed into a steel pipe by a forming machine. The speed of the forming machine is 55-75 m / min.

[0109] (3) The welding wire tip of the steel pipe is rolled into a point using a tipping machine, and the steel pipe is continuously drawn by a wire drawing machine. Lubricating powder should be added to the wire drawing die box of the wire drawing machine, and the cooling water path should be unobstructed. The starting speed is 0.2 to 0.4 m / s, the linkage and jogging speed is 0.10 to 0.25 m / s, and the number of drawing times is 7 to 10 times to obtain the flux-cored welding wire with a diameter of 1.2 to 3.2 mm.

[0110] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0111] It should be understood that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0112] Example 1

[0113] This embodiment provides a flux-cored welding wire for crude oil tanks. The flux-cored welding wire includes a closed steel strip and alloy powder encased inside the steel strip. The alloy powder comprises, by mass fraction:

[0114]

[0115]

[0116] The micro-carbon ferrochrome powder contains 0.1% carbon and 63% chromium by mass; the ferrovanadium powder contains 40% vanadium by mass; the ferroboron powder contains 4% boron by mass; the high-carbon ferromanganese powder contains 4% carbon and 80% manganese by mass; the ferrosilicon powder contains 72% silicon by mass; the ferromolybdenum powder contains 60% molybdenum by mass; the magnesium-aluminum powder contains 40% magnesium by mass; the magnesium-aluminum powder contains 60% aluminum by mass; the rutile powder contains 95% titanium dioxide by mass; and the fluorite powder contains 95% calcium fluoride by mass.

[0117] The steel strip has a thickness of 0.5 mm and a width of 14 mm. The steel strip is Inconel 718 steel strip, and the alloy powder filling rate in the flux-cored wire is 30%.

[0118] This embodiment also provides a method for preparing the flux-cored welding wire for crude oil tanks, the method comprising:

[0119] (1) The rutile powder, feldspar powder and fluorite powder are heated to 200℃ and kept for 1 hour. The micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder and sodium fluorosilicate are heated to 110℃ and kept for 40 minutes. All alloy powders are mixed and heated to 500℃ for 20 minutes. Then they are cooled to obtain the processed alloy powder. The steel strip is first cleaned and dried at 90℃ for 3 minutes. Grooves are set on the steel strip.

[0120] (2) The treated alloy powder is filled into the groove, and the steel strip is closed into a steel pipe by a forming machine at a speed of 55 m / min.

[0121] (3) The welding wire tip of the steel pipe is rolled into a point using a tipping machine, and the steel pipe is continuously drawn by a wire drawing machine. Lubricating powder should be added to the wire drawing die box of the wire drawing machine, and the cooling water circuit should be kept unobstructed. The starting speed is 0.2m / s, the linkage and jogging speed is 0.10m / s, and the number of drawing times is 10 times, which are 4mm→3.80mm→3.5mm→3.2mm→2.9mm→2.7mm→2.5mm→2.2mm→1.9mm→1.5mm→1.2mm, to obtain the flux-cored welding wire with a diameter of 1.2mm.

[0122] The welding process parameters of the flux-cored welding wire prepared in this embodiment are set as follows: arc voltage 28V; current 300A; welding speed 320mm / min; welding wire extension length 25mm; welding gas protection 100% carbon dioxide; gas flow rate 20L / min.

[0123] Example 2

[0124] This embodiment provides a flux-cored welding wire for crude oil tanks. The flux-cored welding wire includes a closed steel strip and alloy powder encased inside the steel strip. The alloy powder comprises, by mass fraction:

[0125]

[0126]

[0127] The micro-carbon ferrochrome powder contains 0.15% carbon and 75% chromium by mass; the ferrovanadium powder contains 30% vanadium by mass; the ferroboron powder contains 6% boron by mass; the high-carbon ferromanganese powder contains 2% carbon and 75% manganese by mass; the ferrosilicon powder contains 78% silicon by mass; the ferromolybdenum powder contains 55% molybdenum by mass; the magnesium aluminum powder contains 30% magnesium by mass; the magnesium aluminum powder contains 70% aluminum by mass; the rutile powder contains 96% titanium dioxide by mass; and the fluorite powder contains 95% calcium fluoride by mass.

[0128] The steel strip has a thickness of 0.4 mm and a width of 15 mm. The steel strip is Inconel 718 steel strip, and the alloy powder filling rate in the flux-cored wire is 32%.

[0129] This embodiment also provides a method for preparing the flux-cored welding wire for crude oil tanks, the method comprising:

[0130] (1) The rutile powder, feldspar powder and fluorite powder are heated to 220℃ and kept for 1.5h for the first time. The micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder and sodium fluorosilicate are heated to 115℃ and kept for 60min for the second time. All alloy powders are mixed and heated to 540℃ for the third time for 30min, and then cooled to obtain the processed alloy powder. The steel strip is first cleaned and dried at 95℃ for 5min, and grooves are set on the steel strip.

[0131] (2) The treated alloy powder is filled into the groove, and the steel strip is closed into a steel pipe by a forming machine at a speed of 75 m / min.

[0132] (3) The welding wire tip of the steel pipe is rolled into a point using a tipping machine, and the steel pipe is continuously drawn by a wire drawing machine. Lubricating powder should be added to the wire drawing die box of the wire drawing machine, and the cooling water circuit should be unobstructed. The starting speed is 0.4m / s, the linkage and jogging speed is 0.25m / s, and the number of drawing times is 7, which are 4mm→3.85mm→3.73mm→3.68mm→3.62mm→3.57mm→3.42mm→3.2mm, respectively, to obtain the flux-cored welding wire with a diameter of 3.2mm.

[0133] The welding process parameters of the flux-cored welding wire prepared in this embodiment are set as follows: arc voltage 33V; current 340A; welding speed 280mm / min; welding wire extension length 20mm; welding gas protection 100% carbon dioxide; gas flow rate 25L / min.

[0134] Example 3

[0135] This embodiment provides a flux-cored welding wire for crude oil tanks. The flux-cored welding wire includes a closed steel strip and alloy powder encased inside the steel strip. The alloy powder comprises, by mass fraction:

[0136]

[0137]

[0138] The micro-carbon ferrochrome powder contains 0.13% carbon and 70% chromium by mass; the ferrovanadium powder contains 35% vanadium by mass; the ferroboron powder contains 5% boron by mass; the high-carbon ferromanganese powder contains 3% carbon and 78% manganese by mass; the ferrosilicon powder contains 75% silicon by mass; the ferromolybdenum powder contains 58% molybdenum by mass; the magnesium aluminum powder contains 35% magnesium by mass; the magnesium aluminum powder contains 65% aluminum by mass; the rutile powder contains 96% titanium dioxide by mass; and the fluorite powder contains 95% calcium fluoride by mass.

[0139] The steel strip has a thickness of 0.4 mm and a width of 15 mm. The steel strip is Inconel 718 steel strip, and the alloy powder filling rate in the flux-cored wire is 34%.

[0140] This embodiment also provides a method for preparing the flux-cored welding wire for crude oil tanks, the method comprising:

[0141] (1) The rutile powder, feldspar powder and fluorite powder are heated to 240℃ and kept for 2 hours. The micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder and sodium fluorosilicate are heated to 130℃ and kept for 50 minutes. All alloy powders are mixed and heated to 550℃ for 25 minutes. Then they are cooled to obtain the processed alloy powder. The steel strip is first cleaned and dried at 90℃ for 4 minutes. Grooves are set on the steel strip.

[0142] (2) The treated alloy powder is filled into the groove, and the steel strip is closed into a steel pipe by a forming machine at a speed of 65m / min.

[0143] (3) The welding wire tip of the steel pipe is rolled into a point using a tipping machine, and the steel pipe is continuously drawn by a wire drawing machine. Lubricating powder should be added to the wire drawing die box of the wire drawing machine, and the cooling water circuit should be unobstructed. The starting speed is 0.3m / s, the linkage and jogging speed is 0.20m / s, and the number of drawing times is 9, namely 4mm→3.65mm→3.41mm→3.2mm→2.91mm→2.49mm→2.24mm→1.93mm→1.71mm→1.6mm, to obtain the flux-cored welding wire with a diameter of 1.6mm.

[0144] The welding process parameters of the flux-cored welding wire prepared in this embodiment are set as follows: arc voltage 27V; current 330A; welding speed 290mm / min; welding wire extension length 22mm; welding gas protection 100% carbon dioxide; gas flow rate 22L / min.

[0145] Example 4

[0146] This embodiment provides a flux-cored welding wire for crude oil tanks. The flux-cored welding wire includes a closed steel strip and alloy powder encased inside the steel strip. The alloy powder comprises, by mass fraction:

[0147]

[0148]

[0149] The micro-carbon ferrochrome powder contains 0.13% carbon and 75% chromium by mass; the ferrovanadium powder contains 35% vanadium by mass; the ferroboron powder contains 6% boron by mass; the high-carbon ferromanganese powder contains 3% carbon and 80% manganese by mass; the ferrosilicon powder contains 75% silicon by mass; the ferromolybdenum powder contains 60% molybdenum by mass; the magnesium-aluminum powder contains 55% magnesium by mass; the magnesium-aluminum powder contains 45% aluminum by mass; the rutile powder contains 95% titanium dioxide by mass; and the fluorite powder contains 95% calcium fluoride by mass.

[0150] The steel strip has a thickness of 0.6 mm and a width of 13 mm. The steel strip is Inconel 718 steel strip, and the alloy powder filling rate in the flux-cored wire is 36%.

[0151] This embodiment also provides a method for preparing the flux-cored welding wire for crude oil tanks, the method comprising:

[0152] (1) The rutile powder, feldspar powder and fluorite powder are heated to 230℃ and kept for 2 hours. The micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder and sodium fluorosilicate are heated to 130℃ and kept for 45 minutes. All alloy powders are mixed and heated to 550℃ for 30 minutes. Then they are cooled to obtain the processed alloy powder. The steel strip is first cleaned and dried at 95℃ for 5 minutes. Grooves are set on the steel strip.

[0153] (2) The treated alloy powder is filled into the groove, and the steel strip is closed into a steel pipe by a forming machine at a speed of 75 m / min.

[0154] (3) The welding wire tip of the steel pipe is rolled into a point using a tipping machine, and the steel pipe is continuously drawn by a wire drawing machine. Lubricating powder should be added to the wire drawing die box of the wire drawing machine, and the cooling water circuit should be unobstructed. The starting speed is 0.4m / s, the linkage and jogging speed is 0.25m / s, and the number of drawing times is 8, which are 4mm→3.84mm→3.75mm→3.63mm→3.49mm→3.29mm→2.95mm→2.62mm→2.4mm, to obtain the flux-cored welding wire with a diameter of 2.4mm.

[0155] The welding process parameters of the flux-cored welding wire prepared in this embodiment are set as follows: arc voltage 30V; current 350A; welding speed 300mm / min; welding wire extension length 23mm; welding gas protection 100% carbon dioxide; gas flow rate 23L / min.

[0156] Example 5

[0157] This embodiment provides a flux-cored welding wire for crude oil tanks. Except for the vanadium iron powder having a particle size of 90-120 mesh, the flux-cored welding wire is the same as that in Embodiment 1.

[0158] Example 6

[0159] This embodiment provides a flux-cored welding wire for crude oil tanks. Except for the boron iron powder having a particle size of 30-50 mesh, the flux-cored welding wire is the same as in Embodiment 1.

[0160] Example 7

[0161] This embodiment provides a flux-cored welding wire for crude oil tanks. Except for the copper powder having a particle size of 90-120 mesh, the flux-cored welding wire is the same as in Embodiment 1.

[0162] Example 8

[0163] This embodiment provides a flux-cored welding wire for crude oil tanks. Except for the copper powder having a particle size of 170-180 mesh, the flux-cored welding wire is the same as in Embodiment 1.

[0164] Example 9

[0165] This embodiment provides a flux-cored welding wire for crude oil tanks. Except for the nickel powder having a particle size of 90-120 mesh, the flux-cored welding wire is the same as in Embodiment 1.

[0166] Example 10

[0167] This embodiment provides a flux-cored welding wire for crude oil tanks. Except for the amount of sodium fluorosilicate, which is 0.3 parts, the flux-cored welding wire is the same as in Embodiment 1.

[0168] Example 11

[0169] This embodiment provides a flux-cored welding wire for crude oil tanks. Except that all alloy powders are subjected to a first heat preservation at 200°C for 1 hour, and no second heat preservation is performed, the flux-cored welding wire is the same as in Embodiment 1.

[0170] Comparative Example 1

[0171] This comparative example provides a flux-cored welding wire for crude oil tanks. Except for the amount of 10 parts of micro-carbon ferrochrome powder, the flux-cored welding wire is the same as that in Example 1.

[0172] Comparative Example 2

[0173] This comparative example provides a flux-cored welding wire for crude oil tanks. Except for the presence of 2 parts of micro-carbon ferrochrome powder, the flux-cored welding wire is the same as that in Example 1.

[0174] Comparative Example 3

[0175] This comparative example provides a flux-cored welding wire for crude oil tanks. Except for the high-carbon manganese iron powder, which is 12 parts, the flux-cored welding wire is the same as that in Example 1.

[0176] Comparative Example 4

[0177] This comparative example provides a flux-cored welding wire for crude oil tanks. Except for the high-carbon manganese iron powder being 3 parts, the flux-cored welding wire is the same as that in Example 1.

[0178] Comparative Example 5

[0179] This comparative example provides a flux-cored welding wire for crude oil tanks. Except for replacing the nickel powder with an equal amount of copper powder, the flux-cored welding wire is the same as in Example 1.

[0180] Comparative Example 6

[0181] This comparative example provides a flux-cored welding wire for crude oil tanks. The flux-cored welding wire is the same as in Example 1, except that the copper powder is replaced with an equal amount of nickel powder.

[0182] Comparative Example 7

[0183] This comparative example provides a flux-cored welding wire for crude oil tanks. Except for the absence of sodium fluorosilicate, the flux-cored welding wire is the same as that in Example 1.

[0184] The main chemical composition of the steel strip used in the above embodiments and comparative examples is shown in Table 1 (wt%). However, this does not mean that the steel strip of this application can only be made with the following composition; the technical objectives of this application can also be achieved by using other commonly used steel strips in the art.

[0185] Table 1

[0186] 0.04 0.13 0.12 52.00 18.50 3.14 0.55 1.01 5.11 0.002 Residuals

[0187] Test methods: Room temperature tensile test specimens of the flux-cored welding wires prepared in the embodiments and comparative examples of this invention were made into rectangular cross-section standard tensile specimens according to GB / T228-2002. The room temperature tensile tests were conducted on a CMT5105-SANS microcomputer-controlled electronic universal testing machine; the impact tests were conducted on a drop hammer impact testing machine. The fracture morphology images of the deposited metal from Examples 1-2 and Comparative Examples 1-4 after the -40℃ impact test are shown below. Figures 4-9 As shown, from Figures 4-9 It can be seen that Examples 1 and 2 show typical ductile fracture surfaces, with deep and uniform dimples, indicating good impact performance. Figures 6-9 The formation of sheet-like structures indicates that the material was torn apart by an impact, resulting in poor mechanical properties.

[0188] According to the "Inspection Guidelines for Corrosion-Resistant Steel Materials in Cargo Oil Tanks of Crude Oil Tankers" standard, the dimensions of the weld wire deposited metal corrosion test sample are 60mm × 25mm × 5mm (the dimensions of base material 2). Welding is performed in the middle of base material 2 to form weld 1, with weld dimensions of 15mm × 25mm × 5mm. Figure 1 and Figure 2 As shown. The sample was polished with 600-grit sandpaper before being placed in the test container. The corrosion sample was drilled with a suspension hole with a diameter of 2 mm, and was suspended in the corrosion solution using a fine nylon thread.

[0189] The corrosion test process is conducted in accordance with the "Guideline for Inspection of Corrosion-Resistant Steel for Cargo Oil Tanks of Crude Oil Tankers" standard, and the following conditions must be met:

[0190] (1) Salt solution mass percentage concentration: 10% NaCl solution;

[0191] (2) pH value: The test solution should contain 10% sodium chloride by weight. The pH value of the solution should be adjusted to 0.85 with hydrochloric acid (if the pH value after dilution is measured, the pH value after dilution should be the same as the pH value before dilution of 0.85).

[0192] (3) Laboratory temperature: 30±2℃;

[0193] (4) Sample placement angle: vertical suspension;

[0194] (5) Change the solution every 24 hours.

[0195] After the corrosion test of the deposited metal corrosion specimen is completed, the weight loss data of the corrosion specimen at each time parameter is recorded. Each time is repeated 5 times, and the average value is taken. The corrosion rate CR (mm / year) is calculated according to the following formula.

[0196]

[0197] Where W is the mass of corrosion loss (g), and S is the surface area of ​​the sample (cm²). 2 ), where ρ is the density of the sample (g / cm³). 2 T is the corrosion test time (h). The coefficients A and B are obtained by performing least squares calculations using a power function on the test results for 21, 49, 77, and 98 days, as shown in the formula ECL = A × t. B Where t is the test time in days, and ECL is the estimated average corrosion weight loss (mm).

[0198] The estimated corrosion loss (ECL) after 25 years is calculated using the following formula, and the standard after 25 years is less than 2 mm;

[0199] ECL(mm)=A×(25×365) B

[0200] The experimental data on seawater corrosion time (h) and weight loss (g) of the samples are shown in Tables 2 and 3. Taking Examples 1 to 4 as examples, the relationship between weight loss and time is shown in the graphs. Figure 3 As shown, from Figure 3 It can be seen that its weight loss is slow and the amount of weight lost is small.

[0201] Table 2

[0202]

[0203] Table 3

[0204]

[0205]

[0206] The mechanical test results and corrosion calculation results of the above embodiments and comparative examples are shown in Table 4.

[0207] Table 4

[0208]

[0209] R in the table above p0.2 R represents yield strength.m A represents tensile strength; A represents elongation; A KV This represents the impact absorption energy at -40℃.

[0210] The following points can be observed from Table 1:

[0211] (1) As can be seen from Examples 1-4, the crude oil tank flux-cored welding wire provided by the present invention, after being welded into a weld, loses ≤0.041g after 72h of seawater corrosion, and R p0.2 ≥396MPa, R m ≥593MPa, A≥24%, A KV ≥75J, the estimated corrosion loss after 25 years is ≤0.82mm, and spatter is not likely to occur during welding;

[0212] (2) It can be seen from the combined examples 1 and 5-9 that in example 1, a specific particle size was selected for gradation of a specific powder. Compared with the example 5-9, where the particle size range was not within the preferred range, the mechanical properties and the estimated corrosion loss after 25 years in example 1 are better than those in example 5-9. Moreover, in example 5-9, slight spatter or splashing occurred during the welding process. This shows that the present invention significantly improves the mechanical properties, corrosion resistance and weldability of flux-cored welding wire for crude oil tanks by selecting a specific particle size of a specific powder for synergistic combination, under the same element ratio.

[0213] (3) Combining Examples 1 and 10, it can be seen that the amount of sodium fluorosilicate in Example 1 is 0.1 parts, compared to 0.3 parts in Example 10. In Example 1, the weight loss after 72 hours of seawater corrosion is 0.038 g, and Rp... 0.2 396 MPa, R m The pressure is 650 MPa, and the a value is 24%. KV The estimated corrosion loss after 25 years is 0.82 mm at 76 J, and spatter is less likely to occur during welding. In contrast, the weight loss after 72 hours of seawater corrosion in Example 10 was 0.078 g, and R... p0.2 375MPa, R m The pressure is 501 MPa, and A is 18%. KV The estimated corrosion loss after 25 years is 3.9 mm, with a value of 37 J. Slight spattering occurs during welding, indicating that the present invention, by optimizing the mass ratio between sodium fluorosilicate and fluorite, produces a flux-cored welding wire with better performance for crude oil tanks.

[0214] (4) As can be seen from the combined examples 1 and 11, the present invention, by adopting a two-stage heat preservation technology, is more conducive to improving the performance of flux-cored welding wire for crude oil tanks;

[0215] (5) As can be seen from the comprehensive examples 1 and 1 to 7, the components of the flux-cored welding wire for crude oil tanks provided by the present invention work together synergistically. These components are indispensable and difficult to be replaced by other components. The synergistic combination improves the mechanical properties, welding performance and corrosion resistance of the welding wire.

[0216] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A flux-cored welding wire for crude oil tanks, characterized in that, The flux-cored welding wire comprises a closed steel strip and alloy powder encased inside the steel strip, wherein the alloy powder comprises, by weight, the following components: 5-8 parts of micro-carbon ferrochrome powder; 1-3 parts of ferrovanadium powder; 1-3 parts of ferroboron powder; 6-9 parts of high-carbon ferromanganese powder; 15-20 parts copper powder; 22-35 parts nickel powder; 1-2 parts of ferrosilicon powder; 6-8 parts of ferromolybdenum powder; 5-7 parts magnesium aluminum powder; 10-15 parts of reduced iron powder; Rutile powder 3.5~4.7 parts; Feldspar powder 2.1~3.2 parts; Fluorite powder 2.3~3.1 parts; Sodium fluorosilicate 0.1~0.3 parts.

2. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The carbon content in the micro-carbon ferrochrome powder is 0.1-0.15% by mass.

3. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The chromium content in the micro-carbon ferrochrome powder is 63-75% by mass.

4. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The vanadium content in the ferrovanadium powder is 30-40% by mass.

5. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The boron content in the ferroboron powder is 4-6% by mass.

6. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The carbon content in the high-carbon ferromanganese powder is 2-4% by mass.

7. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The high-carbon ferromanganese powder contains 75-80% manganese by mass.

8. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The silicon content in the ferrosilicon powder is 72-78% by mass.

9. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The molybdenum content in the ferromolybdenum powder is 55-60% by mass.

10. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The magnesium-aluminum powder contains 30-40% magnesium by mass.

11. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The magnesium-aluminum powder contains 60-70% aluminum by mass.

12. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The rutile powder contains ≥95% titanium dioxide by mass.

13. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The calcium fluoride content in the fluorite powder is ≥95% by mass.

14. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The particle size of the alloy powder is 60~160 mesh.

15. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The nickel powder has a particle size of 150-160 mesh, the copper powder has a particle size of 150-160 mesh, and the reduced iron powder has a particle size of 90-120 mesh.

16. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The particle size of the ferrosilicon powder, ferromolybdenum powder, ferrovanadium powder, or ferroboron powder is independently 60-80 mesh.

17. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The mass ratio of sodium fluorosilicate to fluorite powder is 0.03~0.05:

1.

18. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The thickness of the steel strip is 0.3~0.5mm.

19. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The steel strip has a thickness of 0.3~0.5mm and a width of 13~15mm.

20. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The steel strip is Inconel 718 steel strip.

21. The flux-cored welding wire for crude oil tanks according to claim 1, characterized in that, The alloy powder filling rate in the flux-cored welding wire is 30-36%.

22. A method for preparing the flux-cored welding wire for crude oil tanks according to any one of claims 1 to 21, characterized in that, The preparation method includes: (1) Heat rutile powder, feldspar powder and fluorite powder to 200~240℃ for the first heat preservation, heat micro-carbon ferrochrome powder, ferrovanadium powder, ferroboron powder, high-carbon ferromanganese powder, copper powder, nickel powder, ferrosilicon powder, ferromolybdenum powder, magnesium aluminum powder, reduced iron powder and sodium fluorosilicate to 110~130℃ for the second heat preservation; mix all alloy powders, heat to 500~550℃ for the third heat preservation, and then cool to obtain the treated alloy powder; set grooves on the steel strip; (2) The treated alloy powder is filled into the groove, and the steel strip is closed into a steel pipe by a forming machine; (3) The welding wire head of the steel pipe is rolled into a point using a tipping machine, and the steel pipe is continuously drawn by a wire drawing machine to obtain the flux-cored welding wire.

23. The preparation method according to claim 22, characterized in that, The first heat preservation time is 1~2 hours.

24. The preparation method according to claim 22, characterized in that, The second heat preservation time is 40~60 minutes.

25. The preparation method according to claim 22, characterized in that, The third heat preservation time is 20-30 minutes.

26. The preparation method according to claim 22, characterized in that, The steel strip is first cleaned and dried before the grooves are set.

27. The preparation method according to claim 26, characterized in that, The drying temperature is 90~95℃.

28. The preparation method according to claim 26, characterized in that, The drying time is 3-5 minutes.

29. The preparation method according to claim 22, characterized in that, The speed of the molding machine in step (2) is 55~75m / min.

30. The preparation method according to claim 22, characterized in that, The starting speed of the wire drawing machine in step (3) is 0.2~0.4m / s.

31. The preparation method according to claim 22, characterized in that, The linkage and jogging speed of the wire drawing machine is 0.10~0.25m / s.

32. The preparation method according to claim 22, characterized in that, The wire drawing machine draws 7 to 10 times.

33. The preparation method according to claim 22, characterized in that, The diameter of the flux-cored welding wire is 1.2~3.2mm.

34. A welding method for flux-cored welding wire used in crude oil tanks, characterized in that, The welding method uses the flux-cored welding wire for crude oil tanks as described in any one of claims 1 to 21.

35. The welding method according to claim 34, characterized in that, The arc voltage for welding is 28~33V.

36. The welding method according to claim 34, characterized in that, The welding current is 300~350A.

37. The welding method according to claim 34, characterized in that, The welding speed is 280~320mm / min.

38. The welding method according to claim 34, characterized in that, The welding wire extension length is 20~25mm.

39. The welding method according to claim 34, characterized in that, The protective gas used in the welding is carbon dioxide.

40. The welding method according to claim 34, characterized in that, The flow rate of the protective gas used in the welding is 20~25L / min.

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