Low-temperature-resistant corrosion-resistant welding material for LNG (Liquefied Natural Gas) storage tank and preparation method thereof

Abstract

The invention belongs to the field of metal material processing, and particularly relates to a low-temperature-resistant corrosion-resistant welding material for an LNG storage tank and a preparation method of the welding material, the welding alloy material comprises a welding wire and a plating layer, the welding wire comprises the following powder raw materials in parts by weight: 0.30-0.45% of C, 0.05-0.20% of Si, 20.0-22.0% of Mn, 6.0-8.0% of Cr, 12.0-15.0% of Ni, 1.5-2.0% of Mo, 0.001-0.005% of B, 0.05-0.10% of Ti, 1.0-1.5% of Nb, 0.2-0.5% of V, 0.3-0.5% of Cu, 0.05-0.15% of RE, 0.30-0.50% of a nano material, less than 0.005% of S, less than 0.005% of P and the balance of Fe. A welding wire raw material is subjected to high-temperature vacuum melting, atomization powder preparation, wet mixing method blending, hot isostatic pressing treatment, multi-pass drawing, annealing and solution treatment, and finally acid pickling and coating are conducted to prepare the welding wire, and the welding wire can effectively solve the problems that in the prior art, deposited metal of a welding alloy material for an LNG storage tank is poor in low-temperature impact resistance, poor in corrosion resistance, poor in corrosion resistance and not prone to deformation. And the service life is influenced.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and in particular relates to a low-temperature-resistant and corrosion-resistant welding material for LNG storage tanks and a preparation method thereof. Background Art

[0002] LNG storage tanks operate at a temperature of 163°C, placing high demands on the material's low-temperature plasticity. Low-temperature materials used for LNG storage tanks primarily include nickel-containing alloy steels, primarily 9% Ni steel, ultra-low-temperature austenitic stainless steel, and ultra-low-temperature aluminum alloys. Different materials are used in different applications, with 9% Ni steel being the most widely used. However, due to the persistently high price of nickel, nickel-based low-temperature steels are expensive, driving up the cost of LNG storage and transportation equipment, hindering the development of LNG as a clean energy source.

[0003] Ultra-low-temperature high-manganese steel (22-28% Mn content) shares the same physical and metallurgical characteristics as 9Ni steel, yet offers the advantages of high performance (excellent crack resistance) and low cost (cost savings of 30-40%). This makes it a highly competitive alternative to 9Ni steel for LNG storage tanks, with promising applications and a global research focus. In 2015, POSCO, Daewoo Shipbuilding & Marine Engineering (DSME), and the world's five major classification societies (ABS, BV, DNV GL, KR, and LR) jointly developed a high-manganese steel for LNG storage tanks that entered mass production.

[0004] On the other hand, the complexity of gas storage during LNG tank operations means that even trace amounts of hydrogen, amino, and hydrogen sulfide can lead to hydrogen embrittlement and corrosion. For example, even very low levels of hydrogen sulfide can cause sudden sulfide stress cracking in metal materials in the presence of water. The problems associated with hydrogen-induced corrosion (HIC) and sulfide stress corrosion (SSC) in the storage and transportation of natural gas and other resources, as well as some chemical products, are receiving increasing attention, placing increasing demands on corresponding materials, such as welding materials.

[0005] Therefore, it is of great significance to develop a solid welding wire with good ultra-low temperature impact toughness, corrosion resistance and matching with ultra-low temperature high manganese steel, with high strength of the weld joint, excellent welding process performance and good weld formation. Summary of the Invention

[0006] The purpose of the present invention is to address the problem in the prior art that the deposited metal of the welding alloy material for LNG storage tanks has poor low-temperature impact resistance and poor corrosion resistance, which affects the service life. The present invention provides a new low-temperature and corrosion-resistant welding material for LNG storage tanks and a preparation method thereof; the new material is formulated and optimized to effectively solve the above problems. To achieve the above purpose, the technical solution adopted by the present invention to solve its technical problems is: The present invention provides a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank, comprising the following powder raw materials in parts by weight: C: 0.30-0.45%, Si: 0.05-0.20%, Mn: 20.0-22.0%, Cr: 6.0-8.0%, Ni: 12.0-15.0%, Mo: 1.5-2.0%, B: 0.001-0.005%, Ti: 0.05-0.10%, Nb: 1.0-1.5%, V: 0.2-0.5%, Cu: 0.3-0.5%, RE: 0.05-0.15%, nanomaterial: 0.30-0.50%, S: <0.005%, P: <0.005%, and Fe as a balance.

[0007] Furthermore, the usage ratio of the above-mentioned Mn to Cr is 2.75-3.35.

[0008] Furthermore, the above RE is one or more of Y, La or Ce.

[0009] Another object of the present invention is to provide a method for preparing a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank, comprising the following steps: S1: Oxidation treatment: performing surface oxidation treatment on the nanomaterial to obtain oxidized nanomaterial; S2: Surface modification treatment: ball milling the oxidized nanomaterial with RE and Cr to obtain modified nanomaterial; S3: Raw material ratio: Under argon protection, prepare the original metal powder except the modified nanomaterial; S4: High temperature vacuum melting: The prepared metal powder is subjected to high temperature vacuum melting to obtain an alloy melt; S5: Atomization powder making: The alloy melt is treated by argon atomization method, and spherical atomized alloy powder is obtained after screening; S6: Wet mixing: spherical atomized alloy powder and modified nanomaterials are added to ethanol, ultrasonicated to obtain an ethanol suspension; and dried to obtain a mixed powder. S7: Hot isostatic pressing: The mixed powder is placed in a stainless steel sleeve with a certain amount of space reserved for degassing, and then placed in a hot isostatic press to sinter into a rod blank; S8: Forging and rolling: Forging and rolling the bar billet to prepare alloy wire rod; S9: solution treatment; S10: Surface treatment; i.e. The alloy wire is pickled and coated to obtain the target product.

[0010] Furthermore, the above-mentioned nanomaterials include two-dimensional nanomaterials.

[0011] Furthermore, the above-mentioned two-dimensional nanomaterial is graphene.

[0012] Another object of the present invention is to provide a welding method for low-temperature and corrosion-resistant welding materials for LNG storage tanks, using argon protection with an argon flow rate of 15-20 L / min; a welding current of 300-400 A, and a voltage of 28-32 V; and performing post-weld heat treatment.

[0013] Furthermore, the post-weld heat treatment is a heat treatment at 600-620° C. for 2.0-2.5 hours.

[0014] The present invention has the following beneficial effects: (1) The present invention provides a low-temperature and corrosion-resistant welding material for LNG storage tanks. The welding wire structure is based on Fe, and Mn promotes the formation of a fully austenitic weld, ensuring the low-temperature comprehensive mechanical properties of the weld metal. Cr can strengthen the austenite grain boundaries and improve the corrosion resistance. Ni is a strong austenite-forming element that can effectively improve the low-temperature toughness of the weld metal and has excellent corrosion resistance. Mo is a solid solution strengthening element that can refine the grains and improve the strength of the weld metal. At the same time, Mn, C, and Ni are all austenite-forming elements. When the weld metal molten pool solidifies, the austenite phase is used as the initial solidification phase and is maintained until room temperature, forming a weld metal with an austenitic structure and excellent ultra-low temperature toughness.

[0015] (2) The present invention provides a low-temperature and corrosion-resistant welding material for LNG storage tanks, wherein a certain amount of Ti, V, and Cu elements are added to the welding wire alloy. On the one hand, Ti can improve the weldability of the alloy. It has a strong affinity with oxygen and can act as a deoxidizing element to protect the weld from oxidation, thereby effectively inhibiting the formation of CO and N2 pores and facilitating the formation of the weld. On the other hand, Ti can also reduce the grain size of the weld metal and improve the overall mechanical properties. The V precipitated phase has stability and hydrogen trapping ability, and the ionic bond formed by V carbide and hydrogen is the strongest, which has hydrogen embrittlement resistance. Cu can improve the corrosion resistance of the weld. Copper has a lower affinity with oxygen than iron. During welding, most of it can be transferred to the weld to form a protective film layer, which prevents the corrosion reactions of ammonia, hydrogen sulfide, etc., thereby improving the corrosion resistance.

[0016] (3) The present invention provides a low-temperature and corrosion-resistant welding material for LNG storage tanks. A certain amount of nanomaterials is added to the alloy, and the alloy is ball-milled with RE and Cr. First, RE has a wetting effect, which can reduce the interfacial tension and make the new phase more closely bonded to the matrix, which helps the weld filler metal to spread and bond better, and improve the mechanical properties of the weld. Cr can form a dense Cr2O3 protective layer on the surface, which has antioxidant and corrosion resistance. Second, the two-dimensional nanomaterial has an ultra-large specific surface area, which effectively prevents the growth of grains during heat treatment and has a fine grain strengthening effect. At the same time, it can increase the lattice distortion energy of the dislocation-affected zone, increase the slip resistance, and improve the low-temperature resistance. In addition, the two-dimensional planar structure can effectively block the corrosion factors, further improving the corrosion resistance. Third, the wettability of rare earth provides excellent compatibility between the nanomaterial and the metal; at the same time, it enriches the phase interface, further improving the corrosion resistance of the welding material. Fourth, due to the high specific surface area of the nanomaterial, it has an excellent synergistic effect on the Cr modified on its surface, ensuring low-temperature toughness while also having high corrosion resistance. DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to the following examples. However, it should be understood that the following examples are merely illustrative of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0018] The purpose of the present invention is to develop a low-temperature and corrosion-resistant welding material for LNG storage tanks to solve the problems of poor low-temperature impact resistance and corrosion resistance of the deposited metal of existing welding alloy materials for LNG storage tanks. The implementation strategy is as follows: Mn in the deposited metal ensures the low-temperature comprehensive mechanical properties of the weld metal, including low-temperature toughness; Cr is a solid solution strengthening element, forming a dense Cr2O3 protective layer with corrosion resistance, but Cr>8% will reduce low-temperature toughness; too low a content is insufficient to exert corrosion resistance; that is, Mn and Cr have different emphases on low-temperature toughness and corrosion resistance, but there is a certain antagonism; considering the high specific surface area of nanomaterials, they have a synergistic effect on material properties; at the same time, two-dimensional nanomaterials also have multiple functions such as improving mechanical properties and shielding corrosion factors; surface modification of two-dimensional nanomaterials with Cr can improve corrosion resistance without adding insufficient Cr; at the same time, through surface modification with rare earth metals, its wettability and compatibility between metals are improved; and various mechanisms such as grain refinement, increased lattice distortion energy in dislocation zones, and load bearing of two-dimensional nanomaterials improve various properties; and through formula design, the synergistic addition of trace elements such as Ti, V, and Cu, combined with the preparation and welding processes, a new low-temperature and corrosion-resistant welding material and excellent deposited metal can be prepared. The embodiments of the present invention are as follows: An embodiment of the present invention provides a low-temperature and corrosion-resistant welding material for an LNG storage tank, comprising the following powder raw materials in parts by weight: C: 0.30-0.45%, Si: 0.05-0.20%, Mn: 20.0-22.0%, Cr: 6.0-8.0%, Ni: 12.0-15.0%, Mo: 1.5-2.0%, B: 0.001-0.005%, Ti: 0.05-0.10%, Nb: 1.0-1.5%, V: 0.2-0.5%, Cu: 0.3-0.5%, RE: 0.05-0.15%, nanomaterial: 0.30-0.50%, S: <0.005%, P: <0.005%, and Fe balance.

[0019] The usage ratio of Mn to Cr is 2.75-3.35.

[0020] Mn is a strong austenite-forming element, which promotes the formation of fully austenitic welds and ensures the low-temperature comprehensive mechanical properties of the weld metal, including strength, plasticity and low-temperature toughness. The Mn content in this application is in the range of 21-25%.

[0021] Cr is a solid solution strengthening element and can also strengthen austenite grain boundaries. It forms a dense Cr2O3 protective layer on the surface of the base material that is resistant to oxidation and corrosion. However, Cr>8% will reduce low-temperature toughness and worsen weld formation. The Cr content range of this application is 6.0-8.0%.

[0022] At the same time, considering that Mn and Cr have a certain performance complementary effect, in order to ensure the best comprehensive performance, the usage ratio of Mn to Cr is 2.75-3.35, ensuring that it has excellent low-temperature effect while having certain corrosion resistance.

[0023] The above RE is one or more of Y, La or Ce.

[0024] RE has good wettability and can improve the mechanical strength of the weld; it can also purify the grain boundaries, reduce the segregation of impurity elements at the grain boundaries, and improve the low-temperature toughness and corrosion resistance of the welding material.

[0025] In addition, other important components and functions in the embodiments of the present invention are as follows: As a deoxidizer, Si can improve weld purity, reduce defects, increase weld strength, and reduce the tendency to solidification cracks. However, excessive Si content can cause weld metal to become brittle, reducing plasticity and toughness. Therefore, the present invention controls the Si content to 0.05-0.20%.

[0026] Ni also plays a major role in solid solution strengthening in the alloy, and replacing Ni can reduce costs. At the same time, Fe can also reduce the stacking sequence of the γ matrix, which has a positive impact on improving yield strength. Therefore, the present invention controls the Fe content to 7.0-10.0%.

[0027] Ni is a strong austenite-forming element that can effectively improve the low-temperature toughness and corrosion resistance of the weld metal. It can also improve the material's oxidation resistance, offsetting the problems of weld microstructure coarsening and reduced toughness caused by the addition of Cr. However, Ni is expensive, and excessive content will significantly increase material costs. In the present invention, the Ni content is controlled at 12.0-15.0%.

[0028] Mo is a solid solution strengthening element that can increase weld strength and improve alloy corrosion resistance, especially when combined with Cr, which has a better pitting corrosion resistance. Therefore, the present invention controls the Mo content to 1.5-2.0%.

[0029] Adding a trace amount of B element strengthens the grain boundary and improves the long-term strength of the weld deposited metal, and the trace addition will not increase the sensitivity of welding cracks.

[0030] Ti is a strong deoxidizing element and plays a deoxidizing role during the welding process. Ti can also reduce the grain size of the weld metal and improve the comprehensive mechanical properties. The Ti content range of this application is 0.05-0.10%.

[0031] Niobium increases solid solution lattice distortion and lattice atomic bond attraction, strengthening the matrix and achieving significant solid solution strengthening effects. Niobium is also a strong carbide-forming element, forming MC, M6C, or M2C carbides, which significantly strengthen the weld metal as a second phase and improve mechanical properties. Therefore, the present invention limits the Niobium content to 1.0-1.5%.

[0032] V further enhances the yield strength and tensile strength of the deposited metal, ensuring its low-temperature toughness. Furthermore, V carbides form the strongest ionic bonds with hydrogen, providing resistance to hydrogen embrittlement and excellent storage for the trace amounts of hydrogen in LNG. Therefore, the present invention limits the V content to 0.2-0.5%.

[0033] Cu is an austenite-forming element, which improves the mechanical properties of the weld. Furthermore, copper has a lower affinity for oxygen than iron, so during welding, most of it transfers to the weld, forming a protective film that inhibits corrosive reactions such as ammonia and hydrogen sulfide, thereby improving corrosion resistance. Therefore, the present invention limits the Cu content to 0.3-0.5%.

[0034] Nanomaterials have a high specific surface area and have a significant synergistic effect after being modified on the metal surface, making the material both low-temperature resistant and corrosion-resistant.

[0035] Fe is the main component and plays a major role in solid solution strengthening in the alloy. Substituting Ni can reduce costs.

[0036] Another object of the present invention is to provide a method for preparing a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank, comprising the following steps: S1: oxidation treatment; i.e. The nanomaterial is added to a mixture of concentrated nitric acid and concentrated sulfuric acid, ultrasonically dispersed at room temperature for 4-8 hours, then heated to 60-80°C and refluxed for 1-4 hours. After centrifugation to remove most of the acid, the insoluble matter is filtered and washed with deionized water until neutral, and then vacuum dried at 60°C for 12 hours to obtain the oxidized nanomaterial.

[0037] The total amount of the above-mentioned nanomaterials and the amount of concentrated nitric acid and concentrated sulfuric acid are in the ratio of 1g:30mL:90mL; The above-mentioned nanomaterials include two-dimensional nanomaterials; they can also be one-dimensional nanomaterials; The usage ratio of the above two-dimensional nanomaterial to the one-dimensional nanomaterial is 1.0g:0-0.3g; The two-dimensional nanomaterial is graphene or other two-dimensional nanomaterials that can be oxidized by mixed acid; The graphene has a thickness of 3-10 nm and a sheet diameter of 5-10 μm. In addition, the graphene in the following embodiments and comparative examples of the present invention has a product number of 100078, which was purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.

[0038] The one-dimensional nanomaterial is a carbon nanotube or a carbon nanofiber; preferably, a carbon nanotube; The average diameter of the carbon nanotubes is 10-30 nm, and the aspect ratio is greater than 500. In addition, the carbon nanotubes in the following embodiments and comparative examples of the present invention are of model CT-M-001, purchased from Jiangsu Super Carbon Xianfeng Technology Co., Ltd.

[0039] S2: surface modification treatment; i.e. The oxidized nanomaterial was added to anhydrous ethanol A and ultrasonically vibrated for 20 minutes to obtain a dispersion; the dispersion, RE, Cr, and anhydrous ethanol B were added to a ball mill and ball-milled for 15-24 hours, then filtered, and the insoluble matter was taken and vacuum-dried at 60°C for 12 hours to obtain the modified nanomaterial.

[0040] The usage ratio of the above-mentioned oxidized nanomaterial, anhydrous ethanol A, RE, and anhydrous ethanol B is 0.30-0.50 g: 20 mL: 0.05-0.15 g: 6.0-8.0 g: 30 mL.

[0041] The ball milling process has a rotation speed of 200-300 r / min and a ball-to-material mass ratio of 8-10:1.

[0042] The average particle size of the RE and Cr is 30 μm.

[0043] S3: Raw material ratio: Under argon protection, prepare the original metal powder except the modified nanomaterial; The average particle size of the above-mentioned original metal powder is 50-100 μm.

[0044] S4: High temperature vacuum melting: The prepared metal powder is subjected to high temperature vacuum melting to obtain an alloy melt; The vacuum degree of the above vacuum melting is 5×10 3 -8×10 3Pa，熔炼温度为1420-1600℃。 S5: Atomization powder making: The alloy melt is treated by argon atomization method, and spherical atomized alloy powder is obtained after screening; The process parameters of the argon atomization method are as follows: atomization temperature 1680-1720°C, atomization pressure 0.3 bar, flow rate 45-55 mL / min, and 99.99% high-purity Ar.

[0045] S6: Wet mixing: add spherical atomized alloy powder and modified nanomaterials into ethanol, stir magnetically at 1000 r / min for 3 h, and then subject to 50 kHz ultrasonic treatment for 2 h to obtain an ethanol suspension; filter, take out the insoluble matter, and place it in a drying oven at 80°C for drying for 2 h to obtain a mixed powder.

[0046] S7: Hot isostatic pressing: The mixed powder is placed in a stainless steel sleeve with a certain amount of space reserved for degassing, and then placed in a hot isostatic press to sinter into a rod blank; The degassing process is as follows: the furnace temperature is maintained at 660-700°C, the vacuum degree is less than 0.1Pa, and it is maintained for 6-8 hours; the sintering process is as follows: the temperature is raised to 1220-1280°C at a heating rate of 25°C / min, and then a gas pressure of 120-180MPa is applied to the surface, and the temperature is maintained at constant pressure and temperature for 4-6 hours, and the furnace is cooled to obtain a cylindrical powder sintered rod blank.

[0047] S8: Forging and rolling: Forging and rolling the bar billet to prepare alloy wire rod, and then annealing-drawing treatment; The forging process is to forge the billet into an alloy billet at 1080-1130°C with a forging ratio of 3-4; The above rolling process is to keep the temperature at 1180-1220°C for 0.5-1.5h and hot-roll the alloy wire rod at 1020-1080°C into Φ7.0-8.0mm.

[0048] Lubricant is added before drawing, and 6-8 drawing passes are performed to obtain Φ1.2 mm alloy wire; The present invention has no special requirements for the above-mentioned annealing-drawing process, and the annealing-drawing process well known in the art can be adopted.

[0049] S9: solution treatment; The above-mentioned solution treatment is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 900-1000°C, keeping warm for 2-3 hours, continuing to heat to 1000-1100°C, keeping warm for 2-3 hours, and rapidly water quenching to obtain a solid solution alloy.

[0050] S10: Surface treatment; i.e. The alloy wire is pickled; the coating is specifically and unless otherwise specified, the pickling in the following embodiments and comparative examples of the present invention is to pickle the heat-treated alloy wire, first pickling it with a mixed pickling solution containing 100 g / L nitric acid and 20 g / L hydrofluoric acid, controlling the temperature to be ≤50°C and the pickling time to be 10 minutes; finally, cleaning the residual acid on the surface; The coating is to apply a layer of water-soluble coating agent on the surface of the pickled alloy wire, and the coated alloy wire is naturally air-dried.

[0051] Another object of an embodiment of the present invention is to provide a welding method for low-temperature and corrosion-resistant welding materials for LNG storage tanks, using argon protection with an argon flow rate of 15-20 L / min; a welding current of 300-400 A, a voltage of 28-32 V; and performing post-weld heat treatment.

[0052] The above-mentioned post-weld heat treatment is a heat treatment at 600-620°C for 2.0-2.5 hours.

[0053] In order to further understand the present invention, the low-temperature and corrosion-resistant welding material for LNG storage tanks provided by the present invention is described in detail below in conjunction with specific embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0054] Example 1 This embodiment provides a low-temperature and corrosion-resistant welding material for an LNG storage tank, comprising the following powder raw materials in parts by weight: C: 0.38%, Si: 0.12%, Mn: 21.0%, Cr: 7.0%, Ni: 13.5%, Mo: 1.8%, B: 0.003%, Ti: 0.08%, Nb: 1.2%, V: 0.36%, Cu: 0.4%, RE: 0.10%, nanomaterial: 0.40%, S: 0.002%, P: 0.001%, and Fe balance.

[0055] The above RE is Y.

[0056] Another object of this embodiment is to provide a method for preparing a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank, comprising the following steps: S1: oxidation treatment; i.e. The nanomaterial was added to a mixture of concentrated nitric acid and concentrated sulfuric acid, ultrasonically dispersed at room temperature for 6 hours, then heated to 70°C and refluxed for 2 hours. After centrifugation to remove most of the acid, the insoluble matter was filtered and washed with deionized water until neutral, and then vacuum dried at 60°C for 12 hours to obtain the oxidized nanomaterial.

[0057] The total amount of the above-mentioned nanomaterials and the amount of concentrated nitric acid and concentrated sulfuric acid are in the ratio of 1g:30mL:90mL; The above-mentioned nanomaterials are graphene and carbon nanotubes in a usage ratio of 1.0g:0.2g.

[0058] S2: surface modification treatment; i.e. The oxidized nanomaterial was added to anhydrous ethanol A and ultrasonically vibrated for 20 minutes to obtain a dispersion; the dispersion, RE, Cr, and anhydrous ethanol B were added to a ball mill and ball-milled for 20 hours, then filtered, and the insoluble matter was taken and vacuum-dried at 60°C for 12 hours to obtain the modified nanomaterial.

[0059] The usage ratio of the above-mentioned oxidized nanomaterial, anhydrous ethanol A, RE, and anhydrous ethanol B is 0.40g:20mL:0.10g:7.0g:30mL.

[0060] The ball milling process was performed at a rotation speed of 271 r / min and a ball-to-material mass ratio of 9:1.

[0061] S3: Raw material ratio: Under argon protection, prepare the original metal powder except for the modified nanomaterial.

[0062] S4: High temperature vacuum melting: The prepared metal powder is subjected to high temperature vacuum melting to obtain an alloy melt; The vacuum degree of the above vacuum melting is 6×10 3 Pa, the melting temperature is 1500℃.

[0063] S5: Atomization powder making: The alloy melt is treated by argon atomization method, and spherical atomized alloy powder is obtained after screening; The process parameters of the argon atomization method are as follows: atomization temperature of 1700°C, atomization pressure of 0.3 bar, flow rate of 50 mL / min, and 99.99% high-purity Ar.

[0064] S6: Wet mixing: add spherical atomized alloy powder and modified nanomaterials into ethanol, stir magnetically at 1000 r / min for 3 h, and then subject to 50 kHz ultrasonic treatment for 2 h to obtain an ethanol suspension; filter, take out the insoluble matter, and place it in a drying oven at 80°C for drying for 2 h to obtain a mixed powder.

[0065] S7: Hot isostatic pressing: The mixed powder is placed in a stainless steel sleeve with a certain amount of space reserved for degassing, and then placed in a hot isostatic press to sinter into a rod blank; The above-mentioned degassing treatment process is to maintain the furnace temperature at 680°C and the vacuum degree at <0.1Pa for 7 hours; the above-mentioned sintering process is to heat the temperature to 1250°C at a heating rate of 25°C / min, then apply a gas pressure of 165MPa to the surface, and maintain it at constant pressure and temperature for 5 hours while cooling with the furnace to obtain a cylindrical powder sintered rod blank.

[0066] S8: Forging and rolling: Forging and rolling the bar billet to prepare alloy wire rod, and then annealing and drawing treatment; The forging process is to forge the alloy billet at 1100°C with a forging ratio of 3.5; The above rolling process is to keep the temperature at 1200°C for 1.0h and hot-roll the alloy wire rod at 1050°C into Φ7.5mm.

[0067] Lubricant is added before drawing, and 6-8 drawing passes are performed to obtain Φ1.2mm alloy wire.

[0068] S9: solution treatment; The above-mentioned solution treatment is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 950°C, keeping warm for 2.5 hours, continuing to heat to 1050°C, keeping warm for 2.5 hours, and rapid water quenching to obtain a solid solution alloy.

[0069] S10: The target product is obtained after surface treatment.

[0070] Another object of this embodiment is to provide a welding method for low-temperature and corrosion-resistant welding materials for LNG storage tanks, using argon protection with an argon flow rate of 18L / min; welding current of 350A, voltage of 30V; and post-weld heat treatment.

[0071] The above-mentioned post-weld heat treatment is a heat treatment at 610°C for 2.0h.

[0072] Example 2 This embodiment provides a low-temperature and corrosion-resistant welding material for an LNG storage tank, comprising the following powder raw materials in parts by weight: C: 0.30%, Si: 0.20%, Mn: 20.0%, Cr: 6.0%, Ni: 15.0%, Mo: 2.0%, B: 0.005%, Ti: 0.05%, Nb: 1.0%, V: 0.5%, Cu: 0.5%, RE: 0.15%, nanomaterial: 0.50%, S: 0.002%, P: 0.001%, and Fe balance.

[0073] The above RE is Y.

[0074] Another object of this embodiment is to provide a method for preparing a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank, comprising the following steps: S1: oxidation treatment; i.e. The nanomaterial was added to a mixture of concentrated nitric acid and concentrated sulfuric acid, ultrasonically dispersed at room temperature for 4 hours, then heated to 60°C and refluxed for 4 hours. After centrifugation to remove most of the acid, the insoluble matter was filtered and washed with deionized water until neutral, and vacuum dried at 60°C for 12 hours to obtain the oxidized nanomaterial.

[0075] The total amount of the above-mentioned nanomaterials and the amount of concentrated nitric acid and concentrated sulfuric acid are in the ratio of 1g:30mL:90mL; The above-mentioned nanomaterials are graphene and carbon nanotubes in a usage ratio of 1.0g:0.2g.

[0076] S2: surface modification treatment; i.e. The oxidized nanomaterial was added to anhydrous ethanol A and ultrasonically vibrated for 20 minutes to obtain a dispersion; the dispersion, RE, Cr, and anhydrous ethanol B were added to a ball mill and ball-milled for 15 hours, then filtered, and the insoluble matter was taken and vacuum-dried at 60°C for 12 hours to obtain the modified nanomaterial.

[0077] The usage ratio of the above-mentioned oxidized nanomaterial, anhydrous ethanol A, RE, and anhydrous ethanol B is 0.50g:20mL:0.15g:6.0g:30mL.

[0078] The ball milling process has a rotation speed of 295 r / min and a ball-to-material mass ratio of 8:1.

[0079] S3: Raw material ratio: Under argon protection, prepare the original metal powder except for the modified nanomaterial.

[0080] S4: High temperature vacuum melting: The prepared metal powder is subjected to high temperature vacuum melting to obtain an alloy melt; The vacuum degree of the above vacuum melting is 8×10 3 Pa, the melting temperature is 1420℃.

[0081] S5: Atomization powder making: The alloy melt is treated by argon atomization method, and spherical atomized alloy powder is obtained after screening; The process parameters of the argon atomization method are as follows: atomization temperature of 1720°C, atomization pressure of 0.3 bar, flow rate of 45 mL / min, and 99.99% high-purity Ar.

[0082] S6: Wet mixing: add spherical atomized alloy powder and modified nanomaterials into ethanol, stir magnetically at 1000 r / min for 3 h, and then subject to 50 kHz ultrasonic treatment for 2 h to obtain an ethanol suspension; filter, take out the insoluble matter, and place it in a drying oven at 80°C for drying for 2 h to obtain a mixed powder.

[0083] S7: Hot isostatic pressing: The mixed powder is placed in a stainless steel sleeve with a certain amount of space reserved for degassing, and then placed in a hot isostatic press to sinter into a rod blank; The above-mentioned degassing treatment process is to maintain the furnace temperature at 700°C and the vacuum degree <0.1Pa for 6 hours; the above-mentioned sintering process is to heat the temperature to 1280°C at a heating rate of 25°C / min, then apply a gas pressure of 120MPa to the surface, and maintain it at constant pressure and temperature for 4 hours while cooling with the furnace to obtain a cylindrical powder sintered rod blank.

[0084] S8: Forging and rolling: Forging and rolling the bar billet to prepare alloy wire rod, and then annealing and drawing treatment; The forging process is to forge the alloy billet at 1130°C with a forging ratio of 3; The above rolling process is to keep the temperature at 1220°C for 0.5h and hot-roll the alloy wire rod at 1080°C into Φ8.0mm.

[0085] Lubricant is added before drawing, and 6-8 drawing passes are performed to obtain Φ1.2mm alloy wire.

[0086] S9: solution treatment; The above-mentioned solution treatment is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 900°C, keeping warm for 3 hours, continuing to heat to 1000°C, keeping warm for 3 hours, and rapid water quenching to obtain a solid solution alloy.

[0087] S10: The target product is obtained after surface treatment.

[0088] Another object of this embodiment is to provide a welding method for low-temperature and corrosion-resistant welding materials for LNG storage tanks, using argon protection with an argon flow rate of 20L / min; a welding current of 400A and a voltage of 28V; and performing post-weld heat treatment.

[0089] The above-mentioned post-weld heat treatment is a heat treatment at 600°C for 2.5 hours.

[0090] Example 3 This embodiment provides a low-temperature and corrosion-resistant welding material for an LNG storage tank, comprising the following powder raw materials in parts by weight: C: 0.45%, Si: 0.05%, Mn: 22.0%, Cr: 8.0%, Ni: 12.0%, Mo: 1.5%, B: 0.001%, Ti: 0.10%, Nb: 1.5%, V: 0.2%, Cu: 0.3%, RE: 0.05%, nanomaterial: 0.30%, S: 0.002%, P: 0.001%, and Fe balance.

[0091] The above RE is Y.

[0092] Another object of this embodiment is to provide a method for preparing a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank, comprising the following steps: S1: oxidation treatment; i.e. The nanomaterial was added to a mixture of concentrated nitric acid and concentrated sulfuric acid, ultrasonically dispersed at room temperature for 8 hours, then heated to 80°C and refluxed for 1 hour. After centrifugation to remove most of the acid, the insoluble matter was filtered and washed with deionized water until neutral, and vacuum dried at 60°C for 12 hours to obtain the oxidized nanomaterial.

[0093] The total amount of the above-mentioned nanomaterials and the amount of concentrated nitric acid and concentrated sulfuric acid are in the ratio of 1g:30mL:90mL; The above-mentioned nanomaterials are graphene and carbon nanotubes in a usage ratio of 1.0g:0.2g.

[0094] S2: surface modification treatment; i.e. The oxidized nanomaterial was added to anhydrous ethanol A and ultrasonically vibrated for 20 minutes to obtain a dispersion; the dispersion, RE, Cr, and anhydrous ethanol B were added to a ball mill and ball-milled for 24 hours, then filtered, and the insoluble matter was taken and vacuum-dried at 60°C for 12 hours to obtain the modified nanomaterial.

[0095] The usage ratio of the above-mentioned oxidized nanomaterial, anhydrous ethanol A, RE, and anhydrous ethanol B is 0.30g:20mL:0.05g:8.0g:30mL.

[0096] The ball milling process has a rotation speed of 211 r / min and a ball-to-material mass ratio of 10:1.

[0097] S3: Raw material ratio: Under argon protection, prepare the original metal powder except for the modified nanomaterial.

[0098] S4: High temperature vacuum melting: The prepared metal powder is subjected to high temperature vacuum melting to obtain an alloy melt; The vacuum degree of the above vacuum melting is 5×10 3 Pa, the melting temperature is 1600℃.

[0099] S5: Atomization powder making: The alloy melt is treated by argon atomization method, and spherical atomized alloy powder is obtained after screening; The process parameters of the argon atomization method are: atomization temperature of 1680°C, atomization pressure of 0.3 bar, flow rate of 55 mL / min, and 99.99% high-purity Ar.

[0100] S6: Wet mixing: add spherical atomized alloy powder and modified nanomaterials into ethanol, stir magnetically at 1000 r / min for 3 h, and then subject to 50 kHz ultrasonic treatment for 2 h to obtain an ethanol suspension; filter, take out the insoluble matter, and place it in a drying oven at 80°C for drying for 2 h to obtain a mixed powder.

[0101] S7: Hot isostatic pressing: The mixed powder is placed in a stainless steel sleeve with a certain amount of space reserved for degassing, and then placed in a hot isostatic press to sinter into a rod blank; The above-mentioned degassing treatment process is to maintain the furnace temperature at 660°C and the vacuum degree at <0.1Pa for 8 hours; the above-mentioned sintering process is to heat the temperature to 1220°C at a heating rate of 25°C / min, then apply a gas pressure of 180MPa to the surface, and maintain it at constant pressure and temperature for 6 hours while cooling in the furnace to obtain a cylindrical powder sintered rod blank.

[0102] S8: Forging and rolling: Forging and rolling the bar billet to prepare alloy wire rod, and then annealing-drawing treatment; The forging process is to forge the alloy billet at 1080°C with a forging ratio of 4; The above rolling process is to keep the temperature at 1180°C for 1.5 hours and hot-roll the alloy wire rod at 1020°C to Φ7.0 mm.

[0103] Lubricant is added before drawing, and 6-8 drawing passes are performed to obtain Φ1.2mm alloy wire.

[0104] S9: solution treatment; The above-mentioned solution treatment is a multi-step graded treatment; specifically, in a nitrogen environment, heating to 1000°C, keeping warm for 2 hours, continuing to heat to 1100°C, keeping warm for 2 hours, and rapid water quenching to obtain a solid solution alloy.

[0105] S10: The target product is obtained after surface treatment.

[0106] Another object of this embodiment is to provide a welding method for low-temperature and corrosion-resistant welding materials for LNG storage tanks, using argon protection with an argon flow rate of 15L / min; a welding current of 300A and a voltage of 32V; and performing post-weld heat treatment.

[0107] The above-mentioned post-weld heat treatment is a heat treatment at 620°C for 2.0h.

[0108] Example 4 The rest is the same as in Example 1, except that: A low-temperature and corrosion-resistant welding material for an LNG storage tank comprises the following powder raw materials in parts by weight: C: 0.38%, Si: 0.12%, Mn: 20.0%, Cr: 6.6%, Ni: 13.5%, Mo: 1.8%, B: 0.003%, Ti: 0.08%, Nb: 1.2%, V: 0.36%, Cu: 0.4%, RE: 0.10%, nanomaterial: 0.40%, S: 0.002%, P: 0.001%, and Fe as the balance.

[0109] Example 5 The rest is the same as in Example 1, except that: A low-temperature and corrosion-resistant welding material for an LNG storage tank comprises the following powder raw materials in parts by weight: C: 0.38%, Si: 0.12%, Mn: 22.0%, Cr: 7.3%, Ni: 13.5%, Mo: 1.8%, B: 0.003%, Ti: 0.08%, Nb: 1.2%, V: 0.36%, Cu: 0.4%, RE: 0.10%, nanomaterial: 0.40%, S: 0.002%, P: 0.001%, and Fe as the balance.

[0110] Example 6 The rest is the same as in Example 1, except that: A formula of low temperature and corrosion resistant welding material for LNG storage tanks: Preferably, RE is Ce.

[0111] Example 7 The rest is the same as in Example 1, except that: A formula of low temperature and corrosion resistant welding material for LNG storage tanks: Preferably, RE is a mixture of Y and La in a mass ratio of 3:1.

[0112] Example 8 The rest is the same as in Example 1, except that: A method for preparing low-temperature and corrosion-resistant welding materials for LNG storage tanks, in S1, The preferred nanomaterial is graphene and carbon nanotubes in a ratio of 1.0 g:0.3 g.

[0113] Example 9 The rest is the same as in Example 1, except that: A method for preparing low-temperature and corrosion-resistant welding materials for LNG storage tanks, in S1, The preferred nanomaterial is a graphene to carbon nanotube ratio of 1.0 g:0 g; that is, no carbon nanotube is added.

[0114] The following comparative examples are compared with Example 1: Comparative Example 1 The rest is the same as in Example 1, except that: A low-temperature and corrosion-resistant welding material for an LNG storage tank comprises the following powder raw materials in parts by weight: C: 0.38%, Si: 0.12%, Mn: 21.0%, Cr: 8.0%, Ni: 13.5%, Mo: 1.8%, B: 0.003%, Ti: 0.08%, Nb: 1.2%, V: 0.36%, Cu: 0.4%, RE: 0.10%, nanomaterial: 0.40%, S: 0.002%, P: 0.001%, and Fe as the balance.

[0115] Comparative Example 2 The rest is the same as in Example 1, except that: A formula of low temperature and corrosion resistant welding material for LNG storage tanks: No V added.

[0116] Comparative Example 3 The rest is the same as in Example 1, except that: A formula of low temperature and corrosion resistant welding material for LNG storage tanks: No Cu was added.

[0117] Comparative Example 4 The rest is the same as in Example 1, except that: A formula of low temperature and corrosion resistant welding material for LNG storage tanks: No RE added.

[0118] Comparative Example 5 The rest is the same as in Example 1, except that: A formula of low temperature and corrosion resistant welding material for LNG storage tanks: No nanomaterials added.

[0119] Comparative Example 6 The rest is the same as in Example 1, except that: A method for preparing low-temperature and corrosion-resistant welding materials for LNG storage tanks, in S1, The preferred nanomaterial is graphene and carbon nanotubes in a ratio of 0g:0.2g; that is, graphene is added.

[0120] Comparative Example 7 The rest is the same as in Example 1, except that: A method for preparing low-temperature and corrosion-resistant welding materials for LNG storage tanks. Operations S1 and S2 were not performed; that is, no nanomaterial modification treatment was performed.

[0121] Comparative Example 8 The rest is the same as in Example 1, except that: In a welding method for low-temperature and corrosion-resistant welding materials for LNG storage tanks, No post-weld treatment was performed.

[0122] High manganese austenitic steel was welded using the welding materials and welding methods obtained in the embodiments and comparative examples. The chemical composition of the steel was as follows: C ≤ 0.40-0.50%, Si 0.10-0.20%, Mn 20-28%, N 0.01-0.08%, P ≤ 0.005%, and S ≤ 0.003%. The steel had a size of 400 mm × 300 mm × 20 mm, a 45° groove, a groove bottom distance of 20 mm, a 400 mm × 60 mm × 10 mm pad placed at the bottom, a 3 mm isolation layer was welded on the groove, and tungsten inert gas arc welding was performed.

[0123] The physical properties of the deposited metals of the low-temperature and corrosion-resistant welding materials for LNG storage tanks prepared in the examples of the present invention and the comparative examples were measured, and the results are shown in Table 1.

[0124] Table 1 Physical test performance of each embodiment It can be observed from Examples 1-9 that the low-temperature-resistant and corrosion-resistant welding material for LNG storage tanks of the present invention has excellent mechanical properties, low-temperature resistance and corrosion resistance.

[0125] From Example 1 and Comparative Examples 1-6, it can be observed that the addition of an appropriate ratio of Mn and Cr and the appropriate Cr content in the low-temperature and corrosion-resistant welding material for LNG storage tanks of the present invention can significantly improve low-temperature performance; V and Cu have a positive effect on corrosion resistance, and Cu also has a positive effect on improving mechanical properties and low-temperature performance; RE has a positive effect on weld integrity, improving mechanical properties, low-temperature performance, and corrosion resistance; nanomaterials, especially two-dimensional structured nanomaterials, have an important influence on improving corrosion resistance and low-temperature toughness; It can be observed from Example 1 and Comparative Examples 7-8 that in the preparation method of the low-temperature and corrosion-resistant welding material for LNG storage tanks of the present invention, effective modification of RE, Cr and two-dimensional nanomaterials can significantly improve various performances; post-weld heat treatment also plays an important role in releasing stress, refining grain boundaries, and improving performance.

[0126] In summary, the low-temperature-resistant and corrosion-resistant welding material for LNG storage tanks of the present invention has excellent mechanical properties, low-temperature resistance and corrosion resistance.

[0127] The test method is as follows: (1) Mechanical properties test: The test shall be carried out in accordance with the method described in GB / T 228.1-2021 "Tensile tests on metallic materials - Part 1: Room temperature test methods".

[0128] (2) Low-temperature impact absorption energy: According to GB / T 229-2020 "Metallic Materials - Charpy Pendulum Impact Test Method", the temperature is -196°C.

[0129] (3) Corrosion resistance: Test according to method E described in GB / T 4157-2017; record whether the weld cracks after 720 hours. The product is qualified if there is no cracking or (corrosion) cracks.

[0130] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A low-temperature and corrosion-resistant welding material for LNG storage tanks, characterized by: The invention comprises powder raw materials in the following parts by weight: C: 0.30-0.45%, Si: 0.05-0.20%, Mn: 20.0-22.0%, Cr: 6.0-8.0%, Ni: 12.0-15.0%, Mo: 1.5-2.0%, B: 0.001-0.005%, Ti: 0.05-0.10%, Nb: 1.0-1.5%, V: 0.2-0.5%, Cu: 0.3-0.5%, RE: 0.05-0.15%, nanomaterial: 0.30-0.50%, S: <0.005%, P: <0.005%, and Fe as a remainder.

2. The low-temperature and corrosion-resistant welding material for LNG storage tanks according to claim 1, characterized in that: The usage ratio of Mn to Cr is 2.75-3.

35.

3. The low-temperature and corrosion-resistant welding material for LNG storage tanks according to claim 1, characterized in that: The RE is one or more of Y, La or Ce.

4. A method for preparing a low-temperature and corrosion-resistant welding material for an LNG storage tank, characterized by: The following steps are involved: S1: Oxidation treatment: performing surface oxidation treatment on the nanomaterial to obtain oxidized nanomaterial; S2: Surface modification treatment: ball milling the oxidized nanomaterial with RE and Cr to obtain modified nanomaterial; S3: Raw material ratio: Under argon protection, prepare the original metal powder except the modified nanomaterial; S4: High temperature vacuum melting: The prepared metal powder is subjected to high temperature vacuum melting to obtain an alloy melt; S5: Atomization powder making: The alloy melt is treated by argon atomization method, and spherical atomized alloy powder is obtained after screening; S6: Wet mixing: spherical atomized alloy powder and modified nanomaterials are added to ethanol, ultrasonicated to obtain an ethanol suspension; and dried to obtain a mixed powder. S7: Hot isostatic pressing: The mixed powder is placed in a stainless steel sleeve with a certain amount of space reserved for degassing, and then placed in a hot isostatic press to sinter into a rod blank; S8: Forging and rolling: Forging and rolling the bar billet to prepare alloy wire rod; S9: solution treatment; S10: Surface treatment; i.e. The alloy wire is pickled and coated to obtain the target product.

5. The method for preparing a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank according to claim 4, characterized in that: The nanomaterials include two-dimensional nanomaterials.

6. The method for preparing a low-temperature-resistant and corrosion-resistant welding material for an LNG storage tank according to claim 5, characterized in that: The two-dimensional nanomaterial is graphene.

7. A welding method for low-temperature and corrosion-resistant welding materials for LNG storage tanks, characterized by: Argon protection is used with an argon flow rate of 15-20L / min; welding current is 300-400A, voltage is 28-32V; and post-weld heat treatment is performed.

8. The welding method of low-temperature-resistant and corrosion-resistant welding materials for LNG storage tanks according to claim 7, characterized in that: The post-weld heat treatment is a heat treatment at 600-620° C. for 2.0-2.5 hours.

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