Chromium-molybdenum steel-based gas cylinder pipe and preparation method thereof

Abstract

The invention relates to the field of chromium-molybdenum steel-based gas cylinder pipes, in particular to a chromium-molybdenum steel-based gas cylinder pipe and a preparation method thereof. The preparation method comprises the following steps: preparing a chromium-molybdenum steel base tube from 34CrMO4 steel, preparing a dimethylolpyridine molybdate complex by taking molybdenum trioxide and 2, 6-dimethylolpyridine as raw materials and zinc chloride as an auxiliary agent, and modifying a polyurethane prepolymer by using the dimethylolpyridine molybdate complex to obtain a molybdate modified polyurethane prepolymer; mixing and reacting the molybdate modified polyurethane prepolymer and epoxy resin to prepare modified epoxy resin; mixing the modified epoxy resin, zinc powder, polydopamine modified graphene, an epoxy diluent, a flatting agent, a defoaming agent and an epoxy curing agent to prepare an epoxy resin coating; and the chromium-molybdenum steel pipe is coated with the epoxy resin coating, and the chromium-molybdenum steel-based gas cylinder pipe is obtained. The prepared chromium-molybdenum steel-based gas cylinder pipe is good in hydrogen resistance and can be used for hydrogen and natural gas transportation.

Description

Technical Field

[0001] The invention relates to the technical field of chromium-molybdenum steel-based gas cylinder tubes, in particular to a chromium-molybdenum steel-based gas cylinder tube and a preparation method thereof. Background Art

[0002] With the development of society, the demand for energy in industrial production and daily life is increasing day by day. Hydrogen, as a green energy, can be used as a substitute for traditional fossil fuels to reduce greenhouse gas emissions. At present, among the many solutions for large-scale long-distance hydrogen transportation, pipeline hydrogen transportation is the lowest cost method.

[0003] However, the transportation of natural gas and hydrogen by pipeline has always been plagued by the problem of hydrogen embrittlement. Chromium-molybdenum steel, also known as medium-temperature hydrogen-resistant steel, is an alloy of chromium (Cr), molybdenum (Mo), iron (Fe), and carbon (C). Due to its special high-quality properties, it is often used to manufacture hydrogen pipelines. Considering the operating costs and service life, an anti-corrosion organic coating is often applied on the surface of the pipeline, but the intermolecular gaps of the organic coating can still be penetrated by hydrogen atoms and ions, so the application of pipeline hydrogen resistance faces many challenges. For this reason, it is very necessary to prepare a chromium-molybdenum steel-based gas cylinder tube that is corrosion-resistant and resistant to hydrogen embrittlement. Summary of the invention

[0004] The object of the present invention is to provide a chromium-molybdenum steel-based gas cylinder tube and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a chromium-molybdenum steel-based gas cylinder tube and a preparation method thereof, comprising the following steps: Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and taken out of the furnace when the temperature of the billet is heated to 1250°C. When taken out of the furnace, the temperature difference between the core temperature and the surface temperature of the billet is less than or equal to 5°C; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 45-55r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is detubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference between the wall thickness of the chromium-molybdenum steel base pipe and the wall thickness of the rough pipe is less than 0.1mm; Step 2: The chrome-molybdenum steel base tube was polished and sandblasted to Sa2 level with sandpaper, ultrasonically cleaned in alcohol solution for 30 minutes, rinsed with deionized water and dried; Step 3: Apply epoxy resin coating to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 100-150 μm, and cure at 100-120°C for 2-3 hours to obtain a chrome-nickel steel base gas cylinder tube.

[0006] Furthermore, in step 3, the preparation method of the epoxy resin coating comprises the following steps: S1: Disperse molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride in deionized water, perform hydrothermal reaction at 180-190°C for 72-84h, wash with water and dry after cooling to obtain dihydroxymethylpyridine molybdate complex; S2: performing vacuum dehydration treatment on polyethylene glycol 1000 at 110-120°C for 2-3h, mixing isophorone diisocyanate and polyethylene glycol 1000, heating to 65-80°C, using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 2-3h, cooling to 40-50°C, adding dimethylolpropionic acid, heating to 65-80°C and continuing the reaction for 1-2h to obtain a modified polyurethane prepolymer; adding dimethylol pyridine molybdate complex to the polyurethane prepolymer, continuing the reaction for 0.5-1h, and obtaining a molybdate-modified polyurethane prepolymer; S3: adding graphene to Tris buffer, ultrasonically dispersing for 30-60 min, then adding dopamine hydrochloride, stirring continuously at 25-30°C for 24 h, then centrifuging the mixed system, washing the centrifugal product with anhydrous ethanol and deionized water, and vacuum drying to obtain polydopamine-modified graphene; S4: Mix the molybdate-modified polyurethane prepolymer and epoxy resin, react at 80-90°C for 3-4 hours to obtain a modified epoxy resin; mix the modified epoxy resin, zinc powder, polydopamine-modified graphene, epoxy diluent, leveling agent, and defoaming agent and stir for 10-15 minutes to obtain component A; take the epoxy curing agent as component B; mix components A and B in a mass ratio of 4: (1-1.2) to obtain an epoxy resin coating.

[0007] Furthermore, in S1, the molar ratio of molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride is 1:(0.1~0.2):1.

[0008] Furthermore, in S2, the amounts of the components in the polyurethane prepolymer are, by weight, 28 to 44 parts of isophorone diisocyanate, 65 to 80 parts of polyethylene glycol 1000, and 5 to 8 parts of dimethylol propionic acid.

[0009] Furthermore, in S2, in the molybdate-modified polyurethane prepolymer, the added amount of the dihydroxymethylpyridine molybdate complex is 8-12% of the total weight of the polyurethane prepolymer.

[0010] Furthermore, in S3, the amount of each component used, by weight, is 0.1-0.2 parts of graphene and 0.4-0.5 parts of dopamine hydrochloride.

[0011] Further, in S4, 10-15% of molybdate-modified polyurethane prepolymer and 85-90% of epoxy resin are mixed by weight.

[0012] Furthermore, in S4, in component A, the contents of each component, by weight, are 40 to 50 parts of modified epoxy resin, 24 to 30 parts of zinc powder, 0.1 to 0.3 parts of polydopamine modified graphene, 18 to 22 parts of epoxy diluent, 1 to 2 parts of leveling agent, and 1 to 2 parts of defoaming agent.

[0013] Further, in S4, components A and B are mixed in a mass ratio of 4:(1~1.2).

[0014] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention provides a chrome-molybdenum steel-based gas cylinder tube and a preparation method thereof, wherein 34CrMO4 steel is used as a raw material to process the chrome-molybdenum steel-based tube, and an epoxy resin coating is coated on the surface thereof to obtain a chrome-nickel steel-based gas cylinder tube. In the present invention, graphene is added when preparing the epoxy resin coating, and graphene has a barrier property for hydrogen atoms, but graphene is easily agglomerated in the epoxy resin, resulting in poor coating performance, so the present invention uses polydopamine to modify the graphene to improve its compatibility with the epoxy resin.

[0015] In order to further improve the hydrogen barrier effect of epoxy resin coating, the present invention uses molybdenum trioxide and 2,6-dihydroxymethyl pyridine as raw materials and zinc chloride as an auxiliary agent to synthesize a dihydroxymethyl pyridine molybdate complex. Since the hydroxyl group on the dihydroxymethyl pyridine molybdate complex can react with the isocyanate group, molybdate is introduced into the polyurethane prepolymer to obtain a molybdate-modified polyurethane prepolymer, and the modified epoxy resin is obtained by mixing the molybdate-modified polyurethane prepolymer and the epoxy resin. Compared with the pre-modified epoxy resin, the modified epoxy resin has stronger adhesion, and molybdate has both adsorption and deposition effects on the metal surface, wherein the adsorption effect is: molybdate can be adsorbed on the active sites on the metal surface, so that the metal corrosion potential is positively shifted, the metal corrosion is inhibited and a passivation film is formed on the metal surface; the deposition effect is: molybdate will react with the corrosion products on the steel surface to form a FeMoO4 film, due to MoO4 2- The presence of molybdate forms a competitive adsorption relationship with hydrogen atoms, thereby hindering the diffusion of hydrogen atoms into the metal. Under the joint action of molybdate and graphene, the hydrogen barrier performance of the coating has been significantly improved, reducing hydrogen embrittlement damage and increasing the service life of the gas cylinder tube. It should be noted that although molybdate-modified polyurethane prepolymer has a modification effect on epoxy resin, excessive dosage will also cause phase separation between the two and lead to a decrease in the performance of the coating. Therefore, by weight, the epoxy resin coating prepared by mixing 10~15% molybdate-modified polyurethane prepolymer and 85~90% epoxy resin has the best performance. DETAILED DESCRIPTION

[0016] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0017] Materials and sources used in the present invention: epoxy resin is epoxy resin E-51 from Hebei Linyuan Fine Chemical Co., Ltd.; epoxy diluent is 501 butyl glycidyl ether; epoxy curing agent is epoxy curing agent 650; zinc powder is from Jiangsu Shenlong Zinc Industry Co., Ltd., size 500 mesh; graphene is from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd., item number XF001H; leveling agent is polyether modified polymethyl alkyl siloxane, from Shanghai Bangao Chemical Co., Ltd., model JS-3028; defoaming agent is from Foshan Nanhai Datian Chemical Co., Ltd., item number DT-604.

[0018] Embodiment 1: A chromium-molybdenum steel-based gas cylinder tube and a preparation method thereof, comprising the following steps: Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and taken out of the furnace when the temperature of the billet is heated to 1250°C, and the temperature difference between the core temperature and the surface temperature of the billet when taken out of the furnace is less than or equal to 5°C; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 45r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is de-tubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference in wall thickness between the chromium-molybdenum steel base pipe and the rough pipe is less than 0.1mm; Step 2: S21: dispersing molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride in deionized water in a molar ratio of 1:0.2:1, subjecting the mixture to a hydrothermal reaction at 180° C. for 72 h, cooling, washing with water and drying to obtain a dihydroxymethylpyridine molybdate complex; S22: performing vacuum dehydration treatment on polyethylene glycol 1000 at 110° C. for 2 h, mixing 44 kg of isophorone diisocyanate with 65 kg of polyethylene glycol 1000, raising the temperature to 65° C., using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 2 h, cooling the temperature to 40° C., adding 7 kg of dihydroxymethylpropionic acid, raising the temperature to 65° C. and continuing the reaction for 1 h to obtain a modified polyurethane prepolymer; adding dihydroxymethylpyridine molybdate complex to the polyurethane prepolymer, the amount of dihydroxymethylpyridine molybdate complex added being 8% of the total weight of the polyurethane prepolymer; continuing the reaction for 0.5 h to obtain a molybdate-modified polyurethane prepolymer; S23: 0.1 g of graphene was added to Tris buffer, and after ultrasonic dispersion for 30 min, 0.4 g of dopamine hydrochloride was added, and stirring was continued at 25° C. for 24 h. The mixed system was then centrifuged, and the centrifuged product was washed with anhydrous ethanol and deionized water, and vacuum dried to obtain polydopamine-modified graphene; S24: In percentage by weight, 10% of molybdate-modified polyurethane prepolymer and 90% of epoxy resin are mixed, and reacted at 80° C. for 3 hours to obtain a modified epoxy resin; 40 kg of modified epoxy resin, 24 kg of zinc powder, 0.3 kg of polydopamine-modified graphene, 22 kg of epoxy diluent, 1.5 kg of leveling agent, and 1.3 kg of defoaming agent are mixed and stirred for 10 minutes to obtain component A; epoxy curing agent is taken to obtain component B; components A and B are mixed in a mass ratio of 4:1 to obtain an epoxy resin coating; Step 3: S31: Grind and sandblast the chrome-molybdenum steel base pipe to Sa2 level with sandpaper, ultrasonically clean it in an alcohol solution for 30 minutes, rinse it with deionized water and dry it; S32: Apply epoxy resin coating to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 150 μm, and cure at 100° C. for 2 h to obtain a chrome-nickel steel base gas cylinder tube.

[0019] Embodiment 2: A chromium-molybdenum steel-based gas cylinder tube and a preparation method thereof, comprising the following steps: Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and the billet is taken out of the furnace when the temperature is heated to 1250°C, and the temperature difference between the core temperature and the surface temperature of the billet is less than or equal to 5°C when it is taken out of the furnace; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 50r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is de-tubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference between the wall thickness of the chromium-molybdenum steel base pipe and the wall thickness of the rough pipe is less than 0.1mm; Step 2: S21: dispersing molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride in deionized water in a molar ratio of 1:0.2:1, subjecting the mixture to a hydrothermal reaction at 185° C. for 78 h, cooling, washing with water and drying to obtain a dihydroxymethylpyridine molybdate complex; S22: performing vacuum dehydration treatment on polyethylene glycol 1000 at 115° C. for 2.5 h, mixing 44 kg of isophorone diisocyanate with 65 kg of polyethylene glycol 1000, raising the temperature to 70° C., using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 2.5 h, cooling the temperature to 45° C., adding 7 kg of dihydroxymethylpropionic acid, raising the temperature to 70° C., and continuing the reaction for 1.5 h to obtain a modified polyurethane prepolymer; adding dihydroxymethylpyridine molybdate complex to the polyurethane prepolymer, the dihydroxymethylpyridine molybdate complex added in an amount of 10% of the total weight of the polyurethane prepolymer, and continuing the reaction for 1 h to obtain a molybdate-modified polyurethane prepolymer; S23: 0.1 g of graphene was added to Tris buffer, and after ultrasonic dispersion for 45 min, 0.4 g of dopamine hydrochloride was added, and stirring was continued at 30° C. for 24 h. The mixed system was then centrifuged, and the centrifuged product was washed with anhydrous ethanol and deionized water, and vacuum dried to obtain polydopamine-modified graphene; S24: 13% molybdate modified polyurethane prepolymer and 87% epoxy resin were mixed by weight, and reacted at 85°C for 3.5 hours to obtain modified epoxy resin; 40 kg modified epoxy resin, 24 kg zinc powder, 0.3 kg polydopamine modified graphene, 22 kg epoxy diluent, 1.5 kg leveling agent, and 1.3 kg defoaming agent were mixed and stirred for 12 minutes to obtain component A; epoxy curing agent was taken to obtain component B; components A and B were mixed in a mass ratio of 4:1 to obtain epoxy resin coating; Step 3: S31: Grind and sandblast the chrome-molybdenum steel base pipe to Sa2 level with sandpaper, ultrasonically clean it in an alcohol solution for 30 min, rinse it with deionized water and dry it; S32: Apply epoxy resin coating to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 150 μm, and cure at 110° C. for 2.5 hours to obtain a chrome-nickel steel base gas cylinder tube.

[0020] Embodiment 3: A chromium-molybdenum steel-based gas cylinder tube and a preparation method thereof, comprising the following steps: Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and taken out of the furnace when the temperature of the billet is heated to 1250°C, and the temperature difference between the core temperature and the surface temperature of the billet when taken out of the furnace is less than or equal to 5°C; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 55r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is de-tubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference between the wall thickness of the chromium-molybdenum steel base pipe and the wall thickness of the rough pipe is less than 0.1mm; Step 2: S21: dispersing molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride in deionized water in a molar ratio of 1:0.2:1, subjecting the mixture to a hydrothermal reaction at 190° C. for 84 h, cooling, washing with water and drying to obtain a dihydroxymethylpyridine molybdate complex; S22: performing vacuum dehydration treatment on polyethylene glycol 1000 at 120°C for 3 hours, mixing 44 kg of isophorone diisocyanate with 65 kg of polyethylene glycol 1000, heating to 80°C, using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 3 hours, cooling to 50°C, adding 7 kg of dihydroxymethylpropionic acid, heating to 80°C and continuing the reaction for 2 hours to obtain a modified polyurethane prepolymer; adding dihydroxymethylpyridine molybdate complex to the polyurethane prepolymer, the amount of dihydroxymethylpyridine molybdate complex added is 12% of the total weight of the polyurethane prepolymer; continuing the reaction for 1 hour to obtain a molybdate-modified polyurethane prepolymer; S23: 0.1 g of graphene was added to Tris buffer, and after ultrasonic dispersion for 60 min, 0.4 g of dopamine hydrochloride was added, and stirring was continued at 30° C. for 24 h. The mixed system was then centrifuged, and the centrifuged product was washed with anhydrous ethanol and deionized water, and vacuum dried to obtain polydopamine-modified graphene; S24: In percentage by weight, 15% of molybdate-modified polyurethane prepolymer and 85% of epoxy resin are mixed, and reacted at 90° C. for 4 hours to obtain a modified epoxy resin; 40 kg of modified epoxy resin, 24 kg of zinc powder, 0.3 kg of polydopamine-modified graphene, 22 kg of epoxy diluent, 1.5 kg of leveling agent, and 1.3 kg of defoaming agent are mixed and stirred for 15 minutes to obtain component A; epoxy curing agent is taken to obtain component B; components A and B are mixed in a mass ratio of 4:1 to obtain an epoxy resin coating; Step 3: S31: Grind and sandblast the chrome-molybdenum steel base pipe to Sa2 level with sandpaper, ultrasonically clean it in an alcohol solution for 30 minutes, rinse it with deionized water and dry it; S32: Apply epoxy resin coating to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 150 μm, and cure at 120° C. for 3 hours to obtain a chrome-nickel steel base gas cylinder tube.

[0021] Comparative Example 1: The graphene is not modified, and the other parameters are the same as those in Example 1.

[0022] Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and taken out of the furnace when the temperature of the billet is heated to 1250°C, and the temperature difference between the core temperature and the surface temperature of the billet when taken out of the furnace is less than or equal to 5°C; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 45r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is de-tubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference in wall thickness between the chromium-molybdenum steel base pipe and the rough pipe is less than 0.1mm; Step 2: S21: dispersing molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride in deionized water in a molar ratio of 1:0.2:1, subjecting the mixture to a hydrothermal reaction at 180° C. for 72 h, cooling, washing with water and drying to obtain a dihydroxymethylpyridine molybdate complex; S22: performing vacuum dehydration treatment on polyethylene glycol 1000 at 110° C. for 2 h, mixing 44 kg of isophorone diisocyanate with 65 kg of polyethylene glycol 1000, raising the temperature to 65° C., using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 2 h, cooling the temperature to 40° C., adding 7 kg of dihydroxymethylpropionic acid, raising the temperature to 65° C. and continuing the reaction for 1 h to obtain a modified polyurethane prepolymer; adding dihydroxymethylpyridine molybdate complex to the polyurethane prepolymer, the amount of dihydroxymethylpyridine molybdate complex added being 8% of the total weight of the polyurethane prepolymer; continuing the reaction for 0.5 h to obtain a molybdate-modified polyurethane prepolymer; S23: In percentage by weight, 10% of molybdate-modified polyurethane prepolymer and 90% of epoxy resin are mixed, and reacted at 80° C. for 3 hours to obtain a modified epoxy resin; 40 kg of modified epoxy resin, 24 kg of zinc powder, 0.3 kg of graphene, 22 kg of epoxy diluent, 1.5 kg of leveling agent, and 1.3 kg of defoaming agent are mixed and stirred for 10 minutes to obtain component A; epoxy curing agent is taken to obtain component B; components A and B are mixed in a mass ratio of 4:1 to obtain an epoxy resin coating; Step 3: S31: Grind and sandblast the chrome-molybdenum steel base pipe to Sa2 level with sandpaper, ultrasonically clean it in an alcohol solution for 30 min, rinse it with deionized water and dry it; S32: Apply epoxy resin coating to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 150 μm, and cure at 100° C. for 2 h to obtain a chrome-nickel steel base gas cylinder tube.

[0023] Comparative Example 2: No molybdate-modified polyurethane prepolymer was added, and the other parameters were the same as those in Example 2.

[0024] Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and the billet is taken out of the furnace when the temperature is heated to 1250°C, and the temperature difference between the core temperature and the surface temperature of the billet is less than or equal to 5°C when it is taken out of the furnace; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 50r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is de-tubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference between the wall thickness of the chromium-molybdenum steel base pipe and the wall thickness of the rough pipe is less than 0.1mm; Step 2: S21: 0.1 g of graphene was added to Tris buffer, and after ultrasonic dispersion for 45 min, 0.4 g of dopamine hydrochloride was added, and stirring was continued at 30° C. for 24 h. The mixed system was then centrifuged, and the centrifuged product was washed with anhydrous ethanol and deionized water, and vacuum dried to obtain polydopamine-modified graphene; S22: 40 kg of epoxy resin, 24 kg of zinc powder, 0.3 kg of polydopamine-modified graphene, 22 kg of epoxy diluent, 1.5 kg of leveling agent, and 1.3 kg of defoaming agent were mixed and stirred for 12 minutes to obtain component A; epoxy curing agent was taken to obtain component B; components A and B were mixed in a mass ratio of 4:1 to obtain epoxy resin coating; Step 3: S31: Grind and sandblast the chrome-molybdenum steel base pipe to Sa2 level with sandpaper, ultrasonically clean it in an alcohol solution for 30 min, rinse it with deionized water and dry it; S32: Apply epoxy resin coating to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 150 μm, and cure at 110° C. for 2.5 hours to obtain a chrome-nickel steel base gas cylinder tube.

[0025] Comparative Example 3: The amount of molybdate-modified polyurethane prepolymer was increased, and the other parameters were the same as those in Example 3.

[0026] Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and taken out of the furnace when the temperature of the billet is heated to 1250°C, and the temperature difference between the core temperature and the surface temperature of the billet when taken out of the furnace is less than or equal to 5°C; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 55r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is de-tubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference between the wall thickness of the chromium-molybdenum steel base pipe and the wall thickness of the rough pipe is less than 0.1mm; Step 2: S21: dispersing molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride in deionized water in a molar ratio of 1:0.2:1, subjecting the mixture to a hydrothermal reaction at 190° C. for 84 h, cooling, washing with water and drying to obtain a dihydroxymethylpyridine molybdate complex; S22: performing vacuum dehydration treatment on polyethylene glycol 1000 at 120°C for 3 hours, mixing 44 kg of isophorone diisocyanate with 65 kg of polyethylene glycol 1000, heating to 80°C, using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 3 hours, cooling to 50°C, adding 7 kg of dihydroxymethylpropionic acid, heating to 80°C and continuing the reaction for 2 hours to obtain a modified polyurethane prepolymer; adding dihydroxymethylpyridine molybdate complex to the polyurethane prepolymer, the amount of dihydroxymethylpyridine molybdate complex added is 12% of the total weight of the polyurethane prepolymer; continuing the reaction for 1 hour to obtain a molybdate-modified polyurethane prepolymer; S23: 0.1 g of graphene was added to Tris buffer, and after ultrasonic dispersion for 60 min, 0.4 g of dopamine hydrochloride was added, and stirring was continued at 30° C. for 24 h. The mixed system was then centrifuged, and the centrifuged product was washed with anhydrous ethanol and deionized water, and vacuum dried to obtain polydopamine-modified graphene; S24: In percentage by weight, 15% of molybdate-modified polyurethane prepolymer and 85% of epoxy resin are mixed, and reacted at 90° C. for 4 hours to obtain a modified epoxy resin; 40 kg of modified epoxy resin, 24 kg of zinc powder, 0.3 kg of polydopamine-modified graphene, 22 kg of epoxy diluent, 1.5 kg of leveling agent, and 1.3 kg of defoaming agent are mixed and stirred for 15 minutes to obtain component A; epoxy curing agent is taken to obtain component B; components A and B are mixed in a mass ratio of 4:1 to obtain an epoxy resin coating; Step 3: S31: Grind and sandblast the chrome-molybdenum steel base pipe to Sa2 level with sandpaper, ultrasonically clean it in an alcohol solution for 30 minutes, rinse it with deionized water and dry it; S32: Apply epoxy resin coating to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 150 μm, and cure at 120° C. for 3 hours to obtain a chrome-nickel steel base gas cylinder tube.

[0027] Experiment: Performance tests were performed on the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3.

[0028] Coating adhesion test: Refer to GB / T 9286-2021, and use the cross-cut method to test adhesion, with level 0 being the highest and level 5 being the lowest.

[0029] Hydrogen resistance: Electrochemical hydrogen permeation test was used, with the exposed area of ​​the sample being 2.5 mm in diameter and 0.5 mm in thickness. The polarization potential was 0.3 V (relative to HgO / Hg), the hydrogen permeation current was 30 mA, and the power was continuously turned on and the time for the coating to peel off was recorded, which was recorded as the failure duration.

[0030] The test results are shown in Table 1. Table 1. Test results of various properties of chrome-nickel steel-based gas cylinder tubes

[0031] Conclusion: The data of Examples 1 to 3 show that the chromium-molybdenum steel gas cylinder tube prepared by the present invention has good performance and meets the application standards of gas cylinder tubes. The data of Example 1 and Comparative Example 1 show that after graphene is modified, its compatibility with organic resin can be effectively improved, and the adhesion and hydrogen barrier properties of the coating are improved; the data of Example 2 and Comparative Example 2 show that the adhesion and hydrogen barrier properties of the coating can be improved by adding molybdate-modified polyurethane prepolymer; the data of Example 3 and Comparative Example 3 show that when the amount of molybdate-modified polyurethane prepolymer is too high, the adhesion and hydrogen barrier properties of the material decrease.

[0032] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a chromium-nickel steel-based gas cylinder tube, characterized in that: The following steps are involved: Step 1: The 34CrMO4 steel billet is placed in a ring heating furnace for heating, and taken out of the furnace when the temperature of the billet is heated to 1250°C. When taken out of the furnace, the temperature difference between the core temperature and the surface temperature of the billet is less than or equal to 5°C; the billet taken out of the furnace is perforated to obtain a rough pipe; the roll speed is controlled to be 45-55r / min to perform PQF three-roll continuous rolling on the rough pipe to obtain a rough pipe; the rough pipe is detubed, reduced in diameter, sized, and cooled to obtain a chromium-molybdenum steel base pipe, and the difference between the wall thickness of the chromium-molybdenum steel base pipe and the wall thickness of the rough pipe is less than 0.1mm; Step 2: The chrome-molybdenum steel base tube was polished and sandblasted to Sa2 level with sandpaper, ultrasonically cleaned in alcohol solution for 30 minutes, rinsed with deionized water and dried; Step 3: The epoxy resin coating is applied to the inner and outer surfaces of the chrome-molybdenum steel base tube with a coating thickness of 100-150 μm, and cured at 100-120° C. for 2-3 hours to obtain a chrome-nickel steel base gas cylinder tube.

2. The method for preparing the chromium-nickel steel-based gas cylinder tube according to claim 1, characterized in that: In step 3, the preparation method of the epoxy resin coating comprises the following steps: S1: Disperse molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride in deionized water, perform hydrothermal reaction at 180-190°C for 72-84h, wash with water and dry after cooling to obtain dihydroxymethylpyridine molybdate complex; S2: performing vacuum dehydration treatment on polyethylene glycol 1000 at 110-120°C for 2-3h, mixing isophorone diisocyanate and polyethylene glycol 1000, heating to 65-80°C, using dibutyltin dilaurate as a catalyst, keeping the temperature for reaction for 2-3h, cooling to 40-50°C, adding dimethylolpropionic acid, heating to 65-80°C and continuing the reaction for 1-2h to obtain a modified polyurethane prepolymer; adding dimethylol pyridine molybdate complex to the polyurethane prepolymer, continuing the reaction for 0.5-1h, and obtaining a molybdate-modified polyurethane prepolymer; S3: adding graphene to Tris buffer, ultrasonically dispersing for 30-60 min, then adding dopamine hydrochloride, stirring continuously at 25-30°C for 24 h, then centrifuging the mixed system, washing the centrifugal product with anhydrous ethanol and deionized water, and vacuum drying to obtain polydopamine-modified graphene; S4: Mix the molybdate-modified polyurethane prepolymer and epoxy resin, react at 80-90°C for 3-4 hours to obtain a modified epoxy resin; mix the modified epoxy resin, zinc powder, polydopamine-modified graphene, epoxy diluent, leveling agent, and defoaming agent and stir for 10-15 minutes to obtain component A; take the epoxy curing agent as component B; mix components A and B to obtain an epoxy resin coating.

3. The method for preparing a chromium-nickel steel-based gas cylinder tube according to claim 2, characterized in that: In S1, the molar ratio of molybdenum trioxide, 2,6-dihydroxymethylpyridine and zinc chloride is 1:(0.1~0.2):

1.

4. The method for preparing a chromium-nickel steel-based gas cylinder tube according to claim 2, characterized in that: In S2, the amounts of the components in the polyurethane prepolymer are, by weight, 28-44 parts of isophorone diisocyanate, 65-80 parts of polyethylene glycol 1000, and 5-8 parts of dimethylol propionic acid.

5. The method for preparing a chromium-nickel steel-based gas cylinder tube according to claim 2, characterized in that: In S2, in the molybdate-modified polyurethane prepolymer, the added amount of the dihydroxymethylpyridine molybdate complex is 8-12% of the total weight of the polyurethane prepolymer.

6. The method for preparing a chromium-nickel steel-based gas cylinder tube according to claim 2, characterized in that: In S3, the amount of each component used, by weight, is 0.1-0.2 parts of graphene and 0.4-0.5 parts of dopamine hydrochloride.

7. The method for preparing a chromium-nickel steel-based gas cylinder tube according to claim 2, characterized in that: In S4, 10-15% of molybdate-modified polyurethane prepolymer and 85-90% of epoxy resin are mixed by weight percentage.

8. The method for preparing a chromium-nickel steel-based gas cylinder tube according to claim 2, characterized in that: In S4, in component A, the contents of each component, by weight, are 40-50 parts of modified epoxy resin, 24-30 parts of zinc powder, 0.1-0.3 parts of polydopamine modified graphene, 18-22 parts of epoxy diluent, 1-2 parts of leveling agent, and 1-2 parts of defoaming agent.

9. The method for preparing a chromium-nickel steel-based gas cylinder tube according to claim 2, characterized in that: In S4, components A and B are mixed in a mass ratio of 4:(1~1.2).

10. The chromium-nickel steel-based gas cylinder tube prepared by the preparation method according to any one of claims 1 to 9.

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